Crop Weather and Climate Vulnerability Profiles · 2019-04-17 · CROP WEATHER AND CLIMATE 6...

Crop Weather and Climate Vulnerability Profiles

A collection of crop temperature and water requirement profiles to help reduce the exposure of smallholder farmers to weather and climate-related shocks

ACKNOWLEDGEMENTS

Key contributors to this publication are:

Lead AuthorNorman Martín CasasFormer Researcher Concern Worldwide

Editing Paul Wagstaff Former Agriculture AdviserConcern Worldwide

ACRONYMS AND ABBREVIATIONS

CRS Catholic Relief Services

CSA Climate Smart Agriculture

DAS Days After Sowing

NERICA New Rice for Africa

Cover image: Coconut plantations in Zambezia province, Mozambique have been decimated in recent years by Lethal Yellow Disease, leaving communities without a vital source of food and income. Concern Wolrdwide has been working to encourage small farmers to grow replacement crops such as sesame as a more profitable alternative. Photo by Kieran McConville, 2014.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S2

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 3

FIGURE 1. Maize temperature requirements by growth stage. p10

FIGURE 2. Maize water requirements by growth stage in the tropics and subtropics. p11

FIGURE 3. Pearl millet temperature requirements by growth stage. p13

FIGURE 4. Pearl millet water requirements by growth stage in India and Middle East. p14

FIGURE 5. Pearl millet water requirements by growth stage in northern Africa and the Sahel. p15

FIGURE 6. Sorghum temperature requirements by growth stage. p17

FIGURE 7. Sorghum water requirements by growth stage in the tropics and subtropics. p18

FIGURE 8. Rice (Oryza sativa) temperature requirements by growth stage. p20

FIGURE 9. Rice (sp. indica) temperature requirements by growth stage. p21

FIGURE 10. Paddy rice water requirements by growth stage. p22

FIGURE 11. Upland rice water requirements by growth stage. p23

FIGURE 12. New Rice for Africa (NERICA) water requirements by growth stage. p24

FIGURE 13. Common bean temperature requirements by growth stage. p26

FIGURE 14. Green bean water requirements by growth stage. p27

FIGURE 15. Dry bean water requirements by growth stage. p28

FIGURE 16. Cowpea temperature requirements by growth stage. p30

FIGURE 17. Cowpea water requirements by growth stage. p31

FIGURE 18. Cowpea water requirements by growth stage in Nigeria. p32

FIGURE 19. Groundnut temperature requirements by growth stage. p34

FIGURE 20. Groundnut water requirements by growth stages. p35

FIGURE 21. Groundnut water requirements by growth stage in Sudan. p36

FIGURE 22. Pigeon pea temperature requirements by growth stage. p38

FIGURE 23. Pigeon pea water requirements by growth stage in semi-arid India. p39

FIGURE 24. Soybean temperature requirements by growth stage. p41

FIGURE 25. Soybean water requirements by growth stage in the tropics and subtropics. p42

FIGURE 26. Soybean water requirements by growth stage in West Africa (Nigeria, Senegal). p43

FIGURE 27. Bambara groundnut temperature requirements by growth stage. p45

FIGURE 28. Bambara groundnut water requirements by growth stage in the tropics and subtropics. p46

FIGURE 29. Cassava water requirements by growth stage. Adapted from Del Rio and Simpson (2014). p48

FIGURE 30. Cassava water requirements by growth stage in the tropics: Year 1. p49

FIGURE 31. Cassava water requirements by growth stage in the tropics: Year 2. Adapted from Allen et al., 1998. p50

FIGURE 32. Potato temperature requirements by growth stage. p52

FIGURE 33. Potato water requirements by growth stage in the tropics. p53

FIGURE 34. Optimum temperatures for sweet potato by growth stage. Adapted from Del Rio and Simpson (2014). p55

FIGURE 35. Sweet potato water requirements by growth stage in the tropics. p56

FIGURE 36. Yam (Dioscorea spp.) temperature requirements by growth stage. p58

FIGURE 37. Yam water requirements by growth stage in the tropics (Chapagain and Hoekstra, 2004). p59

FIGURE 38. Taro water requirements by growth stage. p61

FIGURE 39. Banana water requirements by growth stage: year 1. p64

FIGURE 40. Banana water requirements by growth stage: year 2. p65

FIGURE 41. Sesame water requirements by growth stage in the tropics. p67

FIGURE 42. Sesame - Water requirements for Khidir and Promo varieties in Sudan by growth period and irrigation regime (Ahmed & Mahmoud 2010). p68

FIGURE 43. Sunflower temperature requirements by growth stage. p70

FIGURE 44. Sunflower water requirements by growth stage in the tropics and subtropics. p71

LIST OF FIGURES


1. INTRODUCTION ............................. 6

Limitations ........................................ 7

2. CEREALS ........................................ 8

2.1. Maize ........................................ 8

Ecology .......................................... 8

General environmental conditions ....... 8

Crop temperature requirements .......... 8

Crop water requirements ................... 9

2.2. Pearl millet .............................. 12

Ecology ........................................ 12

General environmental conditions ..... 12

Crop temperature requirements ........ 12

Crop water requirements ................. 12

2.3. Sorghum ................................. 16

Ecology ........................................ 16




2.4. Rice ........................................ 19

Ecology ........................................ 19




3. LEGUMES ..................................... 25

3.1. Common bean ......................... 25

Ecology ........................................ 25

Environmental conditions ................. 25



3.2. Cowpea ................................... 29

Ecology ........................................ 29




3.3. Groundnut ............................... 33

Ecology ........................................ 33




3.4. Pigeon pea .............................. 37

Ecology ........................................ 37




3.5. Soybean .................................. 40

Ecology ........................................ 40




3.6. Bambara groundnuts ................ 44

Ecology ........................................ 44




TABLE OF CONTENTS

4. ROOT CROPS ............................... 47

4.1. Cassava .................................. 47

Ecology ........................................ 47




4.2. Solanum Potato ....................... 51

Ecology ........................................ 51




4.3. Sweet Potato ........................... 54

Ecology ........................................ 54




4.4. Yam (Dioscorea spp.) ............... 57

Ecology ........................................ 57




4.5. Taro (Colocasia & Xanthosoma) 60

Ecology ........................................ 60




5. CASH CROPS ............................... 62

5.1. Banana ................................... 62

Ecology ........................................ 62




5.2. Sesame ................................... 66

Ecology ........................................ 66




5.3. Sunflower ................................ 69

Ecology ........................................ 69






1. INTRODUCTION

Smallholder farming systems in the tropics and sub-tropics need to adapt to the consequences of climate change. Most farming systems have1 traditionally evolved and adapted to a changing climate by shifting to different crops, agricultural production systems or even through transformative changes (i.e. moving out of agriculture as a main livelihood source). However, the rapid climate shifts expected to happen over the next years as a result of climate change require immediate agricultural adaptation actions to be put in place2,3,4.

The first step in helping farmers adapt to climate change is to work with farmers to identify climate change risks and vulnerabilities and assess:

• Their Exposure to various climate change risks.• The Sensitivity of their crops and livestock species to the risk identified.• Develop Adaptive responses to avoid or reduce sensitivities.

The full details of this approach can be found in the Catholic Relief Services (CRS) guide: Preparing smallholder farm families to adapt to climate change (Pocket Guide 1: Extension Practice for Agricultural Adaptation)5.

For this type of crop weather vulnerability assessments, two main factors need consideration: water requirements and optimum temperatures/temperature thresholds. This booklet provides a simplified visual guide for field extension staff in relation to these two factors, although there are also other important sensitivity factors including photoperiod, wind, and waterlogging that should be considered.

An essential component of this approach is to consider growth-stage specific crop requirements. This information can be used to adjust planting dates so that critical growth stages avoid temperature and water stresses predicted by weather and climate modelling. In some cases predicted changes in weather patterns may require farmers to change to alternative varieties or entirely new crops. This information also provides an indication of supplementary irrigation needs, if this is an option.

This guide is based on the approach used by Alfonso del Rio and Brent M. Simpson in their Review of fifteen crops cultivated in the Sahel6 and was the result of an extensive literature

1. IPCC5 Climate Change 2014: Impacts, Adaptation, and Vulnerability2. Thornton and Cramer, 2012 (https://cgspace.cgiar.org/rest/bitstreams/17024/retrieve) 3. Ramirez-Villegas and Thornton, 2015 (https://cgspace.cgiar.org/rest/bitstreams/54957/retrieve) 4. Thornton et al., 2015. (https://cgspace.cgiar.org/bitstream/handle/10568/66474/CCAFSWP120.pdf) 5. CRS Pocket Guide 1 http://www.crs.org/our-work-overseas/research-publications/pocket-guide-1-extension-

practice-agricultural-adaptation 6. Alfonso del Rio, Brent M. Simpson, 2014. Review of fifteen crops cultivated in the Sahel. http://pdf.usaid.

gov/pdf_docs/pa00k697.pdf

review with a special focus on sources for crops grown in the tropics and for specific regions of interest, provided that enough data was available. A detailed list of the reference sources for each crop is provided as an annex. For field use this guide should be printed without the annex.

The guide provides a set of diagrams on temperature needs, and water requirements for a range of common tropical smallholder crops through their respective developmental stages. The guide covers maize, pearl millet, sorghum, rice, common bean, cowpea, groundnuts, pigeon pea, soybeans, Bambara groundnuts, cassava, potato, sweet potato, yam, taro (Colocasia spp.), banana, sesame and sunflower. For temperature sensitivity, maximum and minimum ceiling (lethal) temperatures and optimum temperature ranges are represented for both daytime and night-time (whenever enough data is available). For water requirements, average daily temperatures (mm/day) are presented according to a range of agro-ecological zones (semi-arid, sub-humid and humid) and temperature regimes (medium: 15 ºC – 25 ºC; high: > 25 ºC).

LimitationsThis guide only considers the potential interaction between temperature and water requirements. However, other interactions influence crop growth and development: temperature responses change with different photoperiods7, water requirements are influenced by wind speeds8 and the rate of crop development is linked to degree-days experienced by the crop. Unfortunately, this review did not find enough consistent data to provide accurate assessments of these interactions, though as the majority of the papers reviewed were for research carried out in the tropics, the charts assume a more or less constant photoperiod regimes.

The review looked at approximately 300 references, both published papers and agriculture reference books. Crop temperature and water requirements are integral to processed-based crop yield models but there was insufficient time to interrogate crop modelling software to understand the temperature and water requirement variables used and the only software used was the United Nations Food and Agriculture Organisation (FAO) crop water requirement software.

The references reviewed varied widely in quality and usefulness. Many failed to mention the crop variety under trial, or even the location of the trials. Some of the published results were so far from the mean of the results reviewed that they have been treated as outliers and removed from the dataset.

Climate-Smart Agriculture (CSA) includes management practices that enhance the resilience of farming systems by physically reducing the exposure of crops to water and temperature stresses. Few of the references mentioned the farming practices use, so the data is assumed to come from conventionally managed crops.


7. Hatfield and Prueger, 2015 (http://dx.doi.org/10.1016/j.wace.2015.08.001)8. Doorenbos and Pruitt, 1977 (http://www.fao.org/3/a-f2430e.pdf)

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S MAIZE8

2. CEREALS

2.1 Maize

ECOLOGY

Maize grows at regions with latitudes ranging from 40º S to 52º N. This encompasses a number of geographical regions ranging from Russia and Northern Europe, on the northern side; to South Africa, southern Asia (Himalayas, China and Southeast Asia) and Pacific Islands on the southern side. Most producing regions are however found in the humid subtropics and in warm parts of temperate regions. Reported elevations range from sea level to 3,800 m and optimal annual rainfall conditions in the tropics fall between 600 and 900 mm. Maize varieties are classified by starch type (Dent, Flint or Soft), colour (white or yellow) and maturity. White dent maize is the staple food crop for East and Southern Africa, while yellow flint maize predominates in the rest of the world. Flint maize tends to be early maturing.

GENERAL ENVIRONMENTAL CONDITIONS

Full sunlight conditions are needed for the proper development of the maize plant (a C4 plant). Maize is a short day plant, though photoperiod sensitivities vary between cultivars. The short day requirement determines the latest planting date in Southern Africa, with ≈1.5% yield reduction for each day of delayed planting. Optimum soil conditions are characterized by deep, well-drained and aerated soils with plenty of organic matter and a pH range from 5.4 to 7.4. It does not generally withstand waterlogged conditions, especially during its early development stages (first five weeks).

CROP TEMPERATURE REQUIREMENTS

In general, the optimal air temperatures for the maize crop range from 18º to 32º C. Temperature needs are higher for the first development stages (up to flowering), whereas temperature requirements for kernel development and ripening tend to be somewhat lower. Slightly higher temperature requirements are also observed at the flowering stage. Minimum lethal temperatures range from about 8º to 10º C, whereas maximum lethal temperatures tend to become lower as the plant develops (Figure 1). The crop germinates well at soil temperatures between 16º and 18ºC. For proper growth, mean night temperatures should not fall below 14º C. Optimum night temperatures for germination are up to 30º C and those for vegetative development range from 16º to 23º C, whereas night temperatures in the flowering period should not exceed 30º C.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 9MAIZE

Total degree-day accumulated for the whole growing season determines maturity and a maize crop might require from 1600º to 1800º C. Seed companies are not consistent in their classification of maturity but varieties generally range from very early (90-100 days to maturity) to early (100-135 days), medium (120-140 days) and late (130-150 days).

CROP WATER REQUIREMENTS

For the whole crop growth cycle, a total amount of rainfall between 500 and 1200 mm is needed for maize, with short-season varieties even withstanding a minimum of 300 mm. The highest water requirements for maize are found from the flowering until the late grain filling phase (mid- and late season; Figure 2), with a peak during the tasselling and silking phases.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S MAIZE10

11

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FIGURE 1. Maize temperature requirements by growth stage.

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FIGURE 2. Maize water requirements by growth stage in the tropics and subtropics.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S11MAIZE

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S PEARL MILLET12

2.2 Pearl millet

ECOLOGY

The main producing regions of pearl millet can be found in India and in the African tropics and subtropics. It is mostly grown in semi-arid environments and rainfed conditions, especially in the West African Sahel, and it is one of the most important crops in the Sahel. It is mainly grown in areas with an annual rainfall pattern from 200 mm to 800 mm falling within a period of three to six months and matures in 55-65 days.


Pearl millet, a C4 plant, is generally a highly drought tolerant crop able to withstand high temperatures, low soil fertility, salinity and soil acidity. However it is highly sensitive to waterlogging and soil crusting at germination. The best suited type of soils for pearl millet production are light loam soils and sandy soils. Different varieties are adapted to either short or long photoperiods.


The optimal average temperature for pearl millet generally falls between 25º and 30º C, although for West Africa it has been reported to be between 30º C and 35º C. Optimal temperatures remain somewhat constant throughout all the development stages (Figure 3). Minimum night-time temperatures should generally be above 10 º C. Little or no germination occurs below 12º C.


Pearl millet requires between 250 and 700 mm of rainfall during the growth season, although in some cases it can grow with as little as 250 mm if there is little water evaporation and enough soil water retention. The plant is especially susceptible to drought at its early stages and to some extent during the grain filling phase, whereas for the other stages it can withstand droughts up to one month. A minimum accumulated rainfall of 20 mm is recommended for planting. Earlier varieties should be chosen in areas with less amount of rainfall, whereas late varieties are common in areas with rainfall levels above 800 mm. According to the few available studies covering the Sahel and northern Africa (more concretely in Nigeria, Senegal and Southern Tunisia), the studied varieties seem to generally have higher water demands than those consulted for India and the Middle East (UAE) (Figures 4 and 5).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 13PEARL MILLET

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FIGURE 3. Pearl millet temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S PEARL MILLET14

16

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FIGURE 4. Pearl millet water requirements by growth stage in India and Middle East.

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FIGURE 5. Pearl millet water requirements by growth stage in northern Africa and the Sahel.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 15PEARL MILLET

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SORGHUM16

2.3 Sorghum

ECOLOGY

Sorghum is grown in areas ranging between 40 ºN and 40 ºS from the equator, covering a range of 105 countries in the drier parts of Asia, the Americas, Africa and Australia; and with India, United States, Mexico, Nigeria, Sudan and Ethiopia as major producers. It is a typical crop in warm and hot semi-arid environments, although it can grow well in different conditions in the tropics. It normally grows in zones with yearly rainfall amounts from 500 to 1,500 mm and it is cultivated at altitudes up to 2,000 m, as in Ethiopia, Burundi, Uganda and Rwanda.


Sorghum is a drought tolerant C4 crop and is more tolerant to low soil fertility conditions and salinity than other common crops such as maize. It can grow in waterlogging conditions, though it is susceptible to fungal diseases. The crop is extremely vulnerable to frost. It grows best on medium to light textured soils. It tolerates heavy vertisols and light sandy soils, as well as soils with different drainage conditions, with an optimum pH ranging from 5.5 to 8.2. Sorghum is generally a short-day plant, although there are a range of varieties adapted to different photoperiod regimes and tropical varieties may fail to flower at higher latitudes.


Sorghum tolerates a wide range of temperatures and is particularly resistant to high temperatures. Optimum temperatures range from 23º to 31º C, and soil temperatures for planting should be at least 17º C. The reproductive and yielding stages are the most sensitive to high temperatures, with an optimum up to 28º – 30º C and a maximum lethal temperature at flowering of 37º C, whereas higher temperatures are usually required at the younger stages (Figure 6). According to the few sources available, maximum (lethal) night temperatures might range from 28º to 34º C. Prolonged night temperatures below 15º C during the flowering stage are critical.


Sorghum requires between 400 to 900 mm of rainfall during the whole growing season and it is considered as a drought tolerant crop, being able to remain dormant during prolonged dry spells. However, it is particularly susceptible to water stress during the reproductive stages, especially during flowering, where yields can be greatly affected (Figure 7). A minimum accumulated rainfall of 20 mm is recommended for planting.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 17SORGHUM

20

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FIGURE 6. Sorghum temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SORGHUM18

21

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2.4 Rice

ECOLOGY

Rice, (Oryza sativa), is a common crop cultivated in both temperate and tropical environments under a wide range of climatic conditions, ranging from 35 ºS and 50 ºN and from sea level to high altitudes (up to 3,000 m). This is due the different existing varieties, growth periods and cultivation methods, which can either be upland (hill or dryland) and paddy (lowland, flooded). The three sub-species are ssp. indica (tropical rice), ssp. japonica (temperate rice) and ssp. javanica (Javanese rice).


Rice generally requires humid and hot climates. Although being a short-day plant, most modern varieties are insensitive to photoperiod. It is sensitive to strong winds and to frost. It tolerates a wide range of soils, with preference for those with a heavy texture and moderately well drained. It does not grow well in sandy soils and optimum is pH between 6.0 and 7.0. Rice is sensitive to sunlight levels and shade or clouds during the reproductive and ripening phases will reduce yields. Yields are therefor higher in rice grown under irrigation in the dry season.

A relatively new rice variety for Africa, the New Rice for Africa (NERICA) (Africa Rice Centre)9 is also gaining relevance, due to its special resistance to drought and pests. Currently there are 15 different NERICA varieties, most of them for upland production.


In general, daytime temperatures between 24º and 30º C can be considered optimal, whereas optimal night-time temperatures should be between 18 and 25 ºC, with a maximum of 33º C. Rice tolerates relatively high temperatures during the vegetative stage, although African varieties are not able to withstand night temperatures above 25º C during this phase. The range of temperatures at which it can grow becomes narrower as the crop develops (Figures 8, 9). Cold temperatures during flowering can also be detrimental. The subspecies indica is not very tolerant to high temperatures during the flowering and grain filling stages (Figure 9).


Upland rice requires between 800 to 1,000 mm of water for the whole growth period, while paddy rice requires between 1000 and 1500, or even much more. Rice is especially sensitive to drought before tillering and during the flowering stages (mid-season). Paddy rice water requirements do no vary much along growth seasons, remaining constantly high (Figure 10). With regards to lowland rice, the reproductive stage is especially sensitive; and NERICA varieties do generally require slightly less water than average upland varieties, with a notable lower requirement at the late period (Figures 11 and 12).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 19RICE

9. http://www.africarice.org/warda/guide-compend.asp

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S RICE20

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ripen

ing

Germ

inat

ion

and

emer

genc

eSe

edlin

g es

tabl

ishm

ent

Tille

ring

Pani

cle fo

rmat

ion

Head

ing

Flor

al in

itiat

ion,

an

thes

is25

- 40

days

43 ºC

37 ºC

15 -

40 d

ays

5 - 1

0 da

ys25

- 50

day

s15

- 30

day

s5

- 15

days

10 -

15 d

ays

11 ºC

13 ºC

20 ºC

-25

ºC

27 ºC

-35

ºC

20 ºC

-30

ºC

26 ºC

-30

ºC

20 ºC

-26

ºC

28 ºC

-33

ºC25

ºC -

31 ºC

23 ºC

-31

ºC

FIGURE 8. Rice (Oryza sativa) temperature requirements by growth stage.


25

Figure 9. Rice (sp. indica) temperature requirements by growth stage

Maximum temperatures

464544434241 40.1 ºC403938 37 ºC

37363534 33.1 ºC333231302928272625242322212019 20.7 ºC1817 15.8 ºC 16.2 ºC16151413121110

Subspecies Indica (adapted from Sánchez et al., 2014)* Rice - Temperature requirements by growth stage

Minimum temperatures

35.3 ºC

Anthesis Grain fillingGermination and

emergence Tillering Panicle initiation

11.3 ºC

16.4 ºC

31.3 ºC

* Optimal temperature ranges are simplified values expressed as optimal average temperature ± SE, as reported by Sánchez et al. (2014).

25 ºC - 31 ºC

22 ºC - 31 ºC

22 ºC - 26 ºC

25 ºC - 28 ºC

27 ºC - 30 ºC

Rice

FIGURE 9. Rice (sp. indica) temperature requirements by growth stage.


26

Fi

gure

10.

Pad

dy ri

ce w

ater

requ

irem

ents

by

grow

th s

tage

FIGURE 10. Paddy rice water requirements by growth stage.


27

Fi

gure

11.

Upl

and

rice

wat

er re

quire

men

ts b

y gr

owth

sta

ge

FIGURE 11. Upland rice water requirements by growth stage.


28

Fi

gure

12.

New

Ric

e fo

r Afri

ca (N

ER

ICA

) wat

er re

quire

men

ts b

y gr

owth

sta

ge

FIGURE 12. New Rice for Africa (NERICA) water requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 25COMMON BEAN

3. LEGUMES

3.1 Common bean

ECOLOGY

The common bean (Phaseolus vulgaris), a C3 crop, is widely grown throughout the tropics, subtropics and in temperate regions. In the tropics beans are most commonly found in high altitude regions (800 – 2,800 m) and in humid and moderately warm climates. Most of the African production is concentrated in Uganda, Rwanda, Burundi, Tanzania and Kenya, whereas the crop is generally not well suited to ecological conditions in West Africa. It generally grows in regions with an average annual rainfall between 500 to 1,200 mm. Varieties may show determinate (bush beans) or indeterminate (climbing beans) growth.

ENVIRONMENTAL CONDITIONS

Beans are susceptible to frost, waterlogging and strong winds. They are not well suited to wet tropical conditions. Excessive rains causes flower drop and increase the risk of diseases. Moderately to well-drained soils are needed, with an optimum depth from 0.5 m. Beans require a soil pH from 6.0 to 7.5 and a loam to clay loam texture.


Optimum temperatures range from 21º to 26º C. Temperatures from 20º to 28º C are needed for germination. The early vegetative phase is especially sensitive to high temperatures and optimal temperature ranges are higher as the crop progresses to the next stages.


The crop needs an average of 400 to 500 mm during the growth cycle, with a highest demand during the flowering and pod filling phase. Excessive rains (above 1,500 mm) are detrimental. Growing green beans generally implies higher water demands than growing dry beans, with a notably higher requirement during the late growth stages (bean development and maturation) (Figure 14). For dry beans, water demands during the reproductive and early pod filling phase (mid-season) are two to three times higher than for the other phases, whereas a dry weather is required towards the harvesting stage (Figure 15)

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S COMMON BEAN26

31

Figure 13. Common bean temperature requirements by growth stage

Minimum temperatures Optimum day temperatures Optimum night temperatures

34 33 ºC33323130 29 ºC29 28 ºC2827 28 ºC26252423222120191817161514 13.2 ºC13 12 ºC121110

11.6 ºC

32.6 ºC

10 days 25 - 30 days 15 - 25 days 15-20 days (green); 25-30 days (dry)

0 - 5 days (green); 20 - 25 days (dry)

Maximum temperatures

Germination and emergence

Vegetative growth Flowering and pod setting

Pod development and bean filling

Maturation

20 ºC - 28 ºC 21.5 ºC - 26 ºC18 ºC - 27 ºC

21.5 ºC - 27.5 ºC

16 ºC - 24 ºC21.5 ºC

17 ºC - 19.5ºC17 ºC

FIGURE 13. Common bean temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 27COMMON BEAN

32

F Fi

gure

14.

Gre

en b

ean

wat

er re

quire

men

ts b

y gr

owth

sta

ge

FIGURE 14. Green bean water requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S COMMON BEAN28

33

Fi

gure

15:

Dry

bea

n w

ater

requ

irem

ents

by

grow

th s

tage

FIGURE 15. Dry bean water requirements by growth stage.

3.2 Cowpea

ECOLOGY

One of the most widely grown beans in the world, Vigna unguiculata is indigenous to Africa and is well adapted to semi-arid regions. Cowpea is grown throughout Africa, and is the staple legume for most of the Sahel (Niebe). Cowpea is fast maturing (60-65 days) and, depending on the variety, almost all the plant can be eaten. The dried grains contain 25% protein, the pods can be eaten green, the leaves are an important source of green leafy vegetables in Uganda and the roots are used to make a non-alcoholic drink in Zambia. Cowpea is a useful soil improver, fixing more N than the common bean, but is often severely attacked by aphids.


Cowpea is a low altitude crop and is rarely grown above 1,200m. Cowpea tolerates heat and drought but not frost. It can grow on a wide range of soils types, with light soil preferred. Cowpea tolerates a wide range of soil pH, with an optimum pH of 6.0-7.8. Cowpea is shade-tolerant and is usually intercropped or relay cropped with sorghum, millet or maize. Cowpea is a short day C3 crop.


Optimum temperatures range from 24 to 31.5 º C, with temperatures of 31.5-38.5 º C required for germination. Emergence and pod formation is the most sensitive stages for high temperatures, and germination is restricted to temperatures above 11 º C. Night temperatures should not exceed 29 º C, and should ideally be between 17 and 20 º C during flowering.


Cowpea needs 300-50mm of rainfall during the growth cycle. Too much rain will increase incidents of pests and diseases, with significant reductions in yields above 900mm. The highest water requirements are mid-season (30 DAS). Water requirements are low during germination and harvest, and should not exceed 4mm per day. Local varieties have been selected over generations to flower at the end of the rains. Excessive rainfall will extend the flowering period, resulting in asynchronous maturity.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 29COWPEA

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S COWPEA30

36

Figure 16. Cowpea temperature requirements by growth stage


4342 43 ºC414039 38 ºC

383736 37 ºC 35 ºC353433323130 29 ºC292827262524232221201918171615141312 11 ºC11 10 ºC

10 9 ºC98

8.5 ºC

10-15 days

35.5 ºC

25 - 30 days 15-20 days ≥ 20 days

Cowpea - Temperature requirements by growth stage Maximum temperatures

GerminationEmergence and establishment Leaf development Flowering

Pod formation and maturation

30 ºC

31.5 ºC - 38.5 ºC

25.5 ºC - 28 ºC

21 ºC - 28 ºC

21.5 ºC 17 ºC - 20ºC

17 ºC

21.5 ºC - 33 ºC 24 ºC - 31.5 ºC

Cow

pea

FIGURE 16. Cowpea temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 31COWPEA

37

Fi

gure

17.

Cow

pea

wat

er re

quire

men

ts b

y gr

owth

sta

ge

1.45

-1.

94

2.42

-3.

22

3.33

-4.

44

2.17

-2.

89

1.05

-1.

40

2.42

-2.

91

4.03

-4.

84

5.55

-6.

66

3.61

-4.

33

1.75

-2.

10

2.91

-3.

39

4.84

-5.

64

6.66

-7.

76

4.33

-5.

05

2.10

-2.

45

3.39

-3.

88

5.64

-6.

45

7.76

-8.

87

5.05

-5.

78

2.45

-2.

80

3.88

-4.

36

6.45

-7.

25

8.87

-9.

98

5.78

-6.

50

2.80

-3.

15

01234567891011

Initi

al (2

0 da

ys)

Crop

dev

elop

men

t (3

0 da

ys)

Mid

seas

on (3

0 da

ys)

Late

seso

n (2

0 da

ys)

At h

arve

st

W a t e r r e q u i r e m e n t s

Gro

wth

sta

ge

Sem

i-arid

, hig

h te

mpe

ratu

res

Sub-

hum

id, h

igh

tem

pera

ture

s

Sem

i-arid

, med

ium

tem

pera

ture

s

Hum

id, h

igh

tem

pera

ture

s / S

ub-

hum

id, m

ediu

m te

mpe

ratu

res

Hum

id, m

ediu

m te

mpe

ratu

res

Agro

-eco

logi

cal z

one

and

tem

pera

ture

regi

me

(med

ium

=

15 ºC

-25

ºC; h

igh

= >

25 ºC

)

mm

/day

Cow

pea

FIGURE 17. Cowpea water requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S COWPEA32

38

Fi

gure

18.

Cow

pea

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

Nig

eria

1.08

-1.

44

2.22

-2.

96

3.17

-4.

23

2.52

-3.

36

1.80

-2.

16

3.70

-4.

44

5.29

-6.

35

4.20

-5.

04

2.16

-2.

52

4.44

-5.

18

6.35

-7.

40

5.04

-5.

88

2.52

-2.

88

5.18

-5.

92

7.40

-8.

46

5.88

-6.

72

2.88

-3.

24

5.92

-6.

66

8.46

-9.

52

6.72

-7.

56

01234567891011

Initi

al (2

0 da

ys)

Crop

dev

elop

men

t (30

da

ys)

Mid

seas

on (3

0 da

ys)

Late

seso

n (2

0 da

ys)


Gro

wth

sta

ge

Sem

i-arid

, hig

h te

mpe

ratu

res

Sub-

hum

id, h

igh

tem

pera

ture

s

Sem

i-arid

, med

ium

tem

pera

ture

s

Hum

id, h

igh

tem

pera

ture

s / S

ub-

hum

id, m

ediu

m te

mpe

ratu

res

Hum

id, m

ediu

m te

mpe

ratu

res

Agro

-eco

logi

cal z

one

and

tem

pera

ture

regi

me

(med

ium

=

15 ºC

-25

ºC; h

igh

= >

25 ºC

)

mm

/day

FIGURE 18. Cowpea water requirements by growth stage in Nigeria.

3.3 Groundnut

ECOLOGY

Groundnuts, Arachis hypogaea, originated in Peru and are grown throughout the tropics, sub tropics and warm temperate regions, between 40° N and 40° S. Groundnuts are subdivided into runner and bunch types, runner types predominating in West Africa and bunch types in East Africa, with strong cultural preferences. In Uganda red bunch types are preferred in the centre and west of the country and white runner types in the North. White runner-types are grown for direct consumption as a snack, and Red bunch/ Spanish types are grown as an oil crop. Groundnuts may be ground into a flour that is used as the basis for sources. Though high in protein, groundnuts are highly susceptible to mycotoxins, particularly aflatoxins from Aspergillus flavus infections.


Groundnuts need hot and sunny conditions and are sensitive to frosts. Long days (>14 hours) increase vegetative growth while short days (>10 hours) stimulate reproductive growth. Though often intercropped, most groundnuts varieties are not very shade tolerant. Groundnuts grow best on light sandy to sandy loam soils as heavier soils hamper the penetration of the pegs during flowering. Groundnuts fix N and only require additional N during the early growth stages, until Bradyrhizobium has become established. Optimum pH is 6.0-7.5, though Spanish types tolerate lower pH. Calcium deficiencies will cause empty pods “pops”, so Ca should be applied as either gypsum if the pH >6.5 or lime if the pH <6.5. Correct spacing reduces aphid infestations, vectors of groundnut rosette virus.


Though groundnuts can tolerate temperatures as high as 45°C, optimum temperatures are between 24 and 30°C. High temperatures are tolerated during seedling establishment but should be between 24-31°C during flowering, peg and pod formation. Cool temperatures delay flowering. Unlike other legumes, groundnuts can tolerate high night temperatures.


Groundnuts cannot tolerate waterlogging and optimum water requirements are 400-1,200mm for the growing cycle, depending on variety grown. The highest water requirements are during crop development (30-45 DAS) and mid-season (30-50 DAS), up to 10mm per day in hot semi-arid regions. Rainfall over 1,100mm for the growth cycle will significantly reduce yields.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 33GROUNDNUT

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S GROUNDNUT34

41

Figure 19. Groundnut temperature requirements by growth stage


4544 45 ºC 45 ºC 45 ºC4342 43 ºC

41403938373635343332 31 ºC31302928272625242322212019181716151413 12 ºC 12 ºC1211 10 ºC 10 ºC10

* Optimum soil temperature for germination is between 29 ºC and 30 ºC (Mohamed et al. 1988)** Optimum soil temperature for pod development and maturation is between 23 ºC and 32 ºC (Dreyer et al. 1980; Golombek & Johansen 1997)

Groundnut - Temperature requirements by growth stage Maximum temperatures

GerminationSeedling

establishmentStem growth and leaf

developmentFlowering, peg

formationPod formation and

maturation10 - 20 days 25 - 35 days 30 - 40 days 40 - 55 days

13.5 ºC 13.5 ºC

24 ºC - 31 ºC*26 ºC - 31 ºC

26.5 ºC - 33 ºC

25.5 ºC23 ºC - 25ºC

18 ºC - 26 ºC

27 ºC - 32 ºC

24 ºC - 30 ºC**

Groundnut

FIGURE 19. Groundnut temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 35GROUNDNUT

42

Fi

gure

20.

Gro

undn

ut w

ater

requ

irem

ents

by

grow

th s

tage

s

1.47

-1.

96

2.58

-3.

44

3.30

-4.

40

2.01

-2.

681.

77 -

2.36

2.45

-2.

94

4.30

-5.

16

5.50

-6.

60

3.35

-4.

022.

95 -

3.54

2.94

-3.

43

5.16

-6.

02

6.60

-7.

70

4.02

-4.

693.

54 -

4.13

3.43

-3.

92

6.02

-6.

88

7.70

-8.

80

4.69

-5.

364.

13 -

4.72

3.92

-4.

41

6.88

-7.

74

8.80

-9.

90

5.36

-6.

03

4.72

-5.

31

01234567891011

Initi

al (1

5 -3

5 da

ys)

Crop

dev

elop

men

t (3

0 -4

5 da

ys)

Mid

seas

on (3

0 -5

0 da

ys)

Late

seso

n (2

0 -3

5 da

ys)

At h

arve

st


Gro

wth

sta

ge

Sem

i-arid

, hig

h te

mpe

ratu

res

Sub-

hum

id, h

igh

tem

pera

ture

s

Sem

i-arid

, med

ium

tem

pera

ture

s

Hum

id, h

igh

tem

pera

ture

s / S

ub-

hum

id, m

ediu

m te

mpe

ratu

res

Hum

id, m

ediu

m te

mpe

ratu

res

Agro

-eco

logi

cal z

one

and

tem

pera

ture

regi

me

(med

ium

=

15 ºC

-25

ºC; h

igh

= >

25 ºC

)

mm

/day

FIGURE 20. Groundnut water requirements by growth stages.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S GROUNDNUT36

43

Fi

gure

21.

Gro

undn

ut w

ater

requ

irem

ents

by

grow

th s

tage

in S

udan

1.44

-1.

92

2.82

-3.

763.

21 -

4.28

2.07

-2.

762.

40 -

2.88

4.70

-5.

64

5.35

-6.

42

3.45

-4.

14

2.88

-3.

36

5.64

-6.

58

6.42

-7.

49

4.14

-4.

83

3.36

-3.

84

6.58

-7.

52

7.49

-8.

56

4.83

-5.

52

3.84

-4.

32

7.52

-8.

46

8.56

-9.

63

5.52

-6.

21

01234567891011

Initi

al (2

1 da

ys)

Crop

dev

elop

men

t (40

da

ys)

Mid

seas

on (1

6 da

ys)

Late

seso

n (4

0 da

ys)


Gro

wth

sta

ge

Sem

i-arid

, hig

h te

mpe

ratu

res

Sub-

hum

id, h

igh

tem

pera

ture

s

Sem

i-arid

, med

ium

tem

pera

ture

s

Hum

id, h

igh

tem

pera

ture

s /

Sub-

hum

id, m

ediu

m t

empe

ratu

res

Hum

id, m

ediu

m t

empe

ratu

res

Agro

-eco

logi

cal z

one

and

tem

pera

ture

regi

me

(med

ium

=

15 ºC

-25

ºC; h

igh

= >

25 ºC

)

mm

/day

FIGURE 21. Groundnut water requirements by growth stage in Sudan.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 37PIGEON PEA

3.4 Pigeon pea

ECOLOGY

Originally from India, Pigeon Pea, Cajanus cajans spread early to East Africa, which has become a secondary centre of diversity. Pigeon pea is a perennial shrub but is usually grown as an annual. Until recently Pigeon pea was largely ignored by plant breeders but export opportunities to India and the promotion of Pigeon pea as an agroforestry species with multiple uses that can be intercropped with maize has created new markets. Pigeon pea is a short-day plant and takes 60 – 250 days to reach maturity, depending on variety and temperature.


Pigeon Pea is mainly grown in the semi-arid tropics, from sea level to 1,200m. Pigeon pea can be grown on a wide range of soils, including Vertisols and Alfisols and has a wide soil pH tolerance 5.0-8.5. Pigeon pea fixes N through the same rhizobium as cowpeas and fertilisers are rarely used. High rainfall will increase the risk of fungal diseases and in some areas the very high losses due to pod borers and Bruchids (up to 40%) discourage farmers from growing Pigeon Pea.


Pigeon pea can tolerate high temperatures up to 45°C, except during flowering when the optimum temperatures are between 22 and 26°C. Pigeon pea is also tolerant of high night temperatures, but temperatures should not fall below 9°C. Temperature will influence the time of flowering.


Pigeon pea is drought tolerant, shedding flowers during drought, but is intolerant of waterlogging and is unsuitable for high rainfall areas. Between 500-1,000mm of rainfall is required for the crop cycle. Water requirements, 6-12 mm per day, are relatively constant from crop development (35 DAS) onwards as long as the soil is free draining.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S PIGEON PEA38 46

Figure 22. Pigeon pea temperature requirements by growth stage

Maximum temperatures Minimum temperatures Optimum day temperatures Optimum night temperatures

4645 45 ºC44434241 40 ºC

4039383736353433323130292827262524232221201918171615141312 11 ºC 10.7 ºC1110 9.2 ºC

9

45.5 ºC

11.4 ºC

Pigeonpea - Temperature requirements by growth stage

GerminationEmergence and

seedling development Vegetative growth Flowering

20 ºC - 22ºC19 ºC - 26 ºC

22 ºC - 36 ºC

22 ºC - 26 ºC

29 ºC - 36 ºC

21 ºC - 26.5 ºC

15 ºC - 20 ºC

FIGURE 22. Pigeon pea temperature requirements by growth stage.

47

Fi

gure

23.

Pig

eon

pea

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

sem

i-arid

Indi

a.

2.75

-3.

21

6.15

-7.

18

7.83

-9.

14

6.64

-7.

75

3.67

-4.

13

8.20

-9.

23

10.4

4 -1

1.75

8.85

-9.

96

0123456789101112

Initi

al (2

8 da

ys)

Crop

dev

elop

men

t (35

day

s)M

id se

ason

(42

days

)La

te se

son

(21

days

)


Gro

wth

sta

ge

High

tem

pera

ture

s (>

25

ºC)

Med

ium

tem

pera

ture

s (1

5 ºC

-25

ºC)

mm

/day

FIGURE 23. Pigeon pea water requirements by growth stage in semi-arid India.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 39PIGEON PEA

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SOYBEAN40

3.5 Soybean

ECOLOGY

Soybean, Glycine max, originates from China and Japan and has become the most important legume in world trade. Soybean has a high protein and oil content and is traded internationally for oil and animal feeds. Soybean has considerable potential for improving the nutrition of smallholder farmers as it fits well into smallholder farming systems, is a complementary food for maize and rice, can be stored for up to three years and, as a very effective N-fixing crop, increases soil fertility. Soybean requires careful processing to remove anti-nutritional factors and off-favours. Roasted soybeans are often sold as a roadside snack and there is increasing demand from the poultry industry for soybean for poultry feed.


Soybean is a short-day plant and soybean varieties have specific day-length requirements. Soybean will grow in a wide range of soils provided they are not waterlogged, with pH from 5.5-7.5, but low pH soils may create iron and aluminium toxicity issues and liming is recommended to correct the pH and supply calcium. Commercial soybean varieties normally require inoculation with Bradyrhizobium japonicum. Some local varieties nodulate well with local rhizobia (promiscuous varieties) but yields improve with inoculation.


Though originally a temperate crop soybean can tolerate high day temperatures up to 40°C and dislikes low temperatures particularly at flowering. Soybean is particularly sensitive to low night temperatures. Ideally day temperatures should be between 18 and 29°C and night temperatures should not fall below 20°C.


Soybean requires 350-1,100mm of water in the growing cycle and has the greatest water demand mid-season (25-65 DAS), requiring 9.5mm per day in semi-arid climates. Water demand declines towards harvest (<5mm per day), which should be timed for the end of the rains. Unlike most legumes soybean is tolerant of temporary waterlogging,

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 41SOYBEAN50

Figure 24. Soybean temperature requirements by growth stage


464544434241 40 ºC 40 ºC 40 ºC403938373635343332313029282726252423222120191817161514 13 ºC 13 ºC131211 10 ºC10

987 6 ºC6

45.5 ºC


Vegetative growth Flowering Pod development

10 days 30 - 40 days 25 - 35 days 40 - 55 days

20 ºC - 27.5 ºC

17 ºC - 23.5ºC

20 ºC - 27.5 ºC

18.5 ºC - 27.5 ºC 19 ºC - 28 ºC

22 ºC - 29 ºC 22.5 ºC - 29 ºC

FIGURE 24. Soybean temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SOYBEAN42

51

Fi

gure

25.

Soy

bean

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

the

tropi

cs a

nd s

ubtro

pics

FIGURE 25. Soybean water requirements by growth stage in the tropics and subtropics.

52

Fi

gure

26.

Soy

bean

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

Wes

t Afri

ca (N

iger

ia, S

eneg

al)

FIGURE 26. Soybean water requirements by growth stage in West Africa (Nigeria, Senegal)

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 43SOYBEAN

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S BAMBARA GROUNDNUTS44

3.6 Bambara groundnuts

ECOLOGY

Bambara nuts Vigna subterranea (syn. Voandezeia subterranean (Lin)) are indigenous to the sub-humid and semi-arid regions of Africa south of the Sahara10, 11. It is probably the most drought-tolerant of the legumes. The Bambara Groundnut is practically free of pest problems. The underground nature of the plants pod development protects the seeds from airborne insect predation, and the seeds, if left unshelled and properly dried, are less susceptible to rodent and bean weevil (Bruichinae) than most pulses. Bambara nuts are becoming a premium product in local and urban markets, popular with Africa’s emerging middle-classes. Bambara nut has a balanced mix of carbohydrates (50-60%), proteins (16-21%), and fat (4.5-6.5%), with micronutrients potassium, magnesium, calcium, and phosphorous. The proteins contain high levels of methionine. Maturity is between 100 and 180 days.


Bambara nuts grows in a wide range of soils, ranging from loose sand to dense clay and is one of the few crops that thrive sub-Saharan Africa’s widespread lateritic (reddish, acidic) soils. The pH range, 5.0-6.5 is ideal for most African soils and it can be grown from sea level to 1,600m.


Optimum and maximum temperatures decline as growth progresses, from 29-35°C at germination to 21-25°C at pod development. Bambara groundnuts can tolerate high night temperatures but may be sensitive to low night temperatures.


Bambara groundnuts are probably the most drought-tolerant of the legumes, surviving on as little as 600-750mmf rainfall per year, though the best yields are achieved at 900-1,200mm. The plants can tolerate heavy rain, though not flooding. Highest water requirements are at 45 DAS, 3.45- 10.35mm depending on the climate.

10. FAO Traditional Crop of the Month: http://www.fao.org/traditional-crops/bambaragroundnut/en/ 11. Swahili: Njugu mawe (hard stone).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 45BAMBARA GROUNDNUTS

55

Figure 27. Bambara groundnut temperature requirements by growth stage


4948474645444342414039 40 ºC383736 35 ºC3534 35 ºC333231 32 ºC302928272625242322212019181716 15 ºC1514 15 ºC13121110

987 7 ºC

48.5 ºC

12.5 ºC


Vegetative growth Flowering Pod development

21.5 ºC

7 - 11 days 30 - 57 days 23 - 31 days 40 - 66 days

29 ºC - 34 ºC

21 - 25 ºC

28.5 ºC - 32.5 ºC

25 ºC 24 ºC - 27 ºC

Bam

bara Groundnut

FIGURE 27. Bambara groundnut temperature requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S BAMBARA GROUNDNUTS46

56

Fi

gure

28.

Bam

bara

gro

undn

ut w

ater

requ

irem

ents

by

grow

th s

tage

in th

e tro

pics

and

sub

tropi

cs

FIGURE 28. Bambara groundnut water requirements by growth stage in the tropics and subtropics.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 47CASSAVA

4. ROOT CROPS

4.1 Cassava

ECOLOGY

Cassava, Manihot esculenta, is native to South America and was spread throughout the tropics and sub tropics by the Portuguese. Cassava has become the staple carbohydrate crop for many cultures, and the standby, famine, food for others. Maturity varies with variety, traditional varieties may require up to three years, newer varies 9 months. Cassava is hardy, requires little labour and produces very high carbohydrate yields per ha. Cassava contains a cyanogenic glucoside which decomposes to produce cyanide and glucose. Traditional cassava processing removes the cyanide but is adapted to local varieties and may not work well for introduced varieties. Farmers class cassava as “sweet” or “bitter”, depending on the level and distribution of the cyanide in the root tissues. Cassava production in East and Southern Africa has been severely affected by African Cassava Mosaic Virus and Cassava Brown Streak Virus. Cassava is always grown from cuttings, which is responsible, together with whitefly and green mites, for the spread of cassava viruses.


Cassava grows on a wide range of soils but is typically grown on poorer sandy soils or at the end of crop rotation cycles as Cassava can grow on very poor soils due to the presence of very effective endomycorrhizal (fungal) symbiosis. Very fertile soils may even reduce tuber formation. Deep soils, without a hard pan, are required for full tuber formation. Cassava can grow on a very wide range of pH values, from 4.5 -8.2, but does best at 5.2-7.0.


Temperature requirements for cassava are more or less constant for the growth cycle. Cassava grows best at 22-33°C and is damaged by low temperatures and frosts.


Cassava requires 500-5,000mm/year, with an optimum of 1,400-1,80mm. Cassava is very sensitive to waterlogging and grows best on well-drained soils. Water requirement is very low at planting 1-3mm, but full drought will kill the cuttings. Maximum water requirement is reached when the full canopy has developed (11mm/day). Cassava can survive extended droughts.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S CASSAVA48

59

Fi

gure

29.

Cas

sava

wat

er re

quire

men

ts b

y gr

owth

sta

ge. A

dapt

ed fr

om D

el R

io a

nd S

imps

on (2

014)

Max

imum

tem

pera

ture

s

Min

imum

tem

pera

ture

s

O

ptim

um d

ay te

mpe

ratu

res

49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9

10 ºC

10 ºC

10 ºC

10 ºC

10 ºC

Root

dev

elop

men

tLe

af d

evel

opm

ent

Early

and

late

gro

wth

Stem

cutti

ngs

Root

form

atio

nSh

oot e

mer

genc

e

10 ºC

27 ºC

-30

ºC

22 ºC

-29

ºC

26 ºC

-33

ºC25

ºC -

30 ºC

24 ºC

-30

ºC

20 ºC

-27

ºC

FIGURE 29. Cassava water requirements by growth stage. Adapted from Del Rio and Simpson (2014).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 49CASSAVA

60

Fi

gure

30.

Cas

sava

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

the

tropi

cs: Y

ear 1

FIGURE 30. Cassava water requirements by growth stage in the tropics: Year 1.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S CASSAVA50

61

Fi

gure

31.

Cas

sava

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

the

tropi

cs: Y

ear 2

. Ada

pted

from

Alle

n et

al.,

199

8

FIGURE 31. Cassava water requirements by growth stage in the tropics: Year 2. Adapted from Allen et al., 1998.

4.2 Solanum Potato

ECOLOGY

Irish / Solanum Potato, Solanum tuberosum, is a hardy crop, native to the Andes that is now grown worldwide. In the topics and sub tropics the best crops are achieved at high altitudes (1,800-2,300m), where few other staple crops can be grown, or during the cool season in lowland areas. Potatoes can be grown under irrigation in desert areas as long as the nights are cool. Tuber formation is triggered by the short days in the tropics (<12 hours).


Potato grows on a wide range of soils, from sandy soils to the deep organic and volcanic soils of Rwanda and Burundi. Deep, friable soils are required for good tuber formation, and potato does not do well in clays. Potatoes prefer an acidic soil, as low as 4.8, with optimum pH 5.6-7.0.


Low night temperatures are critical for tuber formation. Potato can tolerate high day temperatures as long as the nights are cool. Low day and night temperatures are required for tuber formation (15.5-19°C day, 15-16°C night). Potato is not frost tolerant.


Potato has a small root system and is easily water stressed and a regular water supply is required for good quality tubers. Maximum water requirement is 11mm/day in semi-arid areas. Potato does not tolerate waterlogging – raised beds should be used if the water table is high.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 51SOLANUM POTATO

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SOLANUM POTATO52

63

Figure 32. Potato temperature requirements by growth stage


3736 37 ºC35 36 ºC343332313029 30 ºC2827 28 ºC262524 25 ºC 25 ºC23222120191817161514131211 10 ºC 10 ºC10

987 6 ºC6

6.5 ºC

Soil temperature Air temperature Soil temperature Soil temperature

Sprout development and emergence

Early vegetative growth

Late vegetative, tuber initiation

Tuber bulking

15 - 20 days 15 - 25 days 15 - 20 days 30 - 55 days

29.5 ºC

12 ºC - 18 ºC

17.5 ºC - 23 ºC19 ºC - 24 ºC

15.5 ºC - 19 ºC

21 ºC - 27 ºC

15 ºC - 16 ºC

Solanum

Potato

FIGURE 32. Potato temperature requirements by growth stage.

64

Fi

gure

33.

Pot

ato

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

the

tropi

cs

FIGURE 33. Potato water requirements by growth stage in the tropics.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 53SOLANUM POTATO

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SWEET POTATO54

4.3 Sweet Potato

ECOLOGY

Sweet Potato, Ipomoea batatas, also originates from the Andes. It is grown across Africa and Asia, up to an altitude of 2,000m, and is the stable carbohydrate in the Papua New Guinea Highlands. Vine cuttings are used for propagation and the leaves are often used as a vegetable.


Sweet Potato grows well on acid soils and, as it is also tolerant of aluminium, it is the crop of choice for very acid soils, down to pH4. Sweet potato grows on a wide variety of soils but, like most tubers, deep, loose, well-drained soils produce the best yields. Sweet potato is often planted in mounds or ridges to ensure good drainage and friable soil.


As with most vegetative propagated crops temperature requirements are consistent through the growth cycle. The optimum temperatures range is 21-30°C, with a minimum of 16 and a maximum 40°C. Night temperatures should be between 18°C and 21°C. Growths stops below 4°C and is reduced below 10°C. Sweet Potato is frost sensitive.


Sweet potato has very little resistance to drought and requires 550-1,270 mm of rainfall in the growing season. The highest water requirement is mid-season, 4-12mm/day of water, with reduced water requirements at harvest.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 55SWEET POTATO

66

Fi

gure

34.

Opt

imum

tem

pera

ture

s fo

r sw

eet p

otat

o by

gro

wth

sta

ge. A

dapt

ed fr

om D

el R

io a

nd S

imps

on (2

014)

49 47 45 43 41 39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9

Late

gro

wth

and

root

de

velo

pmen

tLe

af d

evel

opm

ent

Vine

gro

wth

and

m

atur

itySt

em cu

ttin

gs,

seed

ling

deve

lopm

ent

Root

initi

atio

nSh

oot g

row

th

24 ºC

-28

ºC25

ºC -

30 ºC

24 ºC

-28

ºC21

ºC -

28 ºC

24 ºC

-28

ºC20

ºC -

30 ºC

FIGURE 34. Optimum temperatures for sweet potato by growth stage. Adapted from Del Rio and Simpson (2014).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SWEET POTATO56

67

Fi

gure

35.

Sw

eet p

otat

o w

ater

requ

irem

ents

by

grow

th s

tage

in th

e tro

pics

FIGURE 35. Sweet potato water requirements by growth stage in the tropics.

4.4 Yam (Dioscorea spp.)

ECOLOGY

There are many Dioscorea species, originating in West Africa, South America and Asia and grown throughout the humid and sub-humid regions. The preferred habitat is the border between tropical moist forest and savanna. An important crop in West Africa but a minor crop elsewhere, where it is usually grown as a “plant and forget” reserve food crop.


Dioscorea yams need a hot humid climate with deep, fertile, friable and permeable sandy-clay soils with a pH of 5.0-7.0. Yam is often the first crop after the forest has been cleared. Yams are normally staked but may climb up trees or maize stalks.


Yams dislike low temperatures, growing best at 20-33°C, and night temperatures above 19°C. Temperatures should not fall below 11°C and 17°C during tuber formation.


Yams require an annual rainfall of 1,000 to 1,500mm, but are tolerant of irregular rainfall. The critical period is mid-season, when the plants are in full growth and the reserves of the seed tubers (sets) have been exhausted when the plants will require 3.3-10mm per day.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 57 YAM (DIOSCOREA SPP.)

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S YAM (DIOSCOREA SPP.)58

69

Figure 36. Yam (Dioscorea spp.) temperature requirements by growth stage

38 37 ºC3736353433323130292827262524232221201918 17 ºC171615141312 11 ºC1110

987

Germination Seedling establishment Vegetative growth Tuber development

20 - 25 days 30 - 40 days > 35 days

11.5 ºC

32.5 ºC

36.5 ºC

23 ºC - 30 ºC

24 - 33 ºC

20 ºC - 32 ºC

19 ºC - 25 ºC

23 ºC - 28 ºCYam

(Dioscorea)

FIGURE 36. Yam (Dioscorea spp.) temperature requirements by growth stage.

70

Fi

gure

37.

Yam

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

the

tropi

cs (C

hapa

gain

and

Hoe

kstra

, 200

4)

FIGURE 37. Yam water requirements by growth stage in the tropics (Chapagain and Hoekstra, 2004).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 59 YAM (DIOSCOREA SPP.)

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S TARO (COLOCASIA & XANTHOSOMA)60

4.5 Taro (Colocasia & Xanthosoma)

ECOLOGY

Taro is often called yam is East Africa and the terms cocoyam, eddo, dasheen, tannia and yam may be used without distinction. This data refers to Colocasia sp. and Xanthosoma sagittifolium. Colocasia originated in South Asia while Xanthosoma came from Central America and the Caribbean. Taro is recognisable by its large heart-shaped leaves. Taro is an important crop in West Africa and is the starch staple for several of the Pacific and Caribbean Islands.


Taro requires high temperatures, a light, deep soil, high water table and a pH of 5.5-6.5. In East Africa and the Pacific Islands taro is often grown in swamps and seasonal wetlands however a high yielding drought tolerant variety, Berekat, has been developed in Ethiopia. Taro prefers shade and is often intercropped with bananas, coffee or breadfruit.


Given the lack of available reports documenting temperature effects on taro at different growth stages, it has not been possible to graphically represent taro temperature requirements by growth stage.

The optimal daily temperature ranges from 21 ºC to 27 ºC. Best photosynthesis is achieved between 25 ºC and 29 ºC. Plants die with air temperatures below 10 ºC. According to a few available reports, it is suggested that optimum temperature ranges for vegetative development fall between 22 and 30 ºC, whereas optimum temperatures for tuber development may lie between 19 ºC and 32 ºC. Taro corms must be stored at cool temperatures. Temperatures around 25 ºC result in low germination rates. Low temperatures (10 ºC or lower) can effectively break dormancy of taro corms.


An annual rainfall of 2,000mm is required for most taro varieties. Once growth is underway water requirements are high, up to 13mm/day, until harvest.

73

Fi

gure

38.

Tar

o w

ater

requ

irem

ents

by

grow

th s

tage

FIGURE 38. Taro water requirements by growth stage.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 61TARO (COLOCASIA & XANTHOSOMA)

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S BANANA62

5. CASH CROPS

5.1 Banana

ECOLOGY

Bananas (Musa acuminate; Musa × paradisiaca L. = hybrid M. acuminata × M. balbisiana) are a genetically diverse group of plants. Banana classification is complexed and common names are used interchangeably (banana v plantain). Bananas for export (Cavendish) are grown in large monoculture plantations while smallholders in Central Uganda and the Great Lakes Region of Africa, where bananas are the staple crop, grow a diverse range of banana types for cooking, beer, fibre, and as a desert fruit. East African Highland bananas are often intercropped with coffee, beans, taro, papaya and timber trees like Albezia sp.


With the exception of the East Africa Highland bananas which are grown up to 1,800m, bananas are grown in the lowlands, desert bananas require high humidity and protection from strong winds. Most bananas grow well in full sun and shading or clouds prolong the growth cycle. Bananas are heavy feeders and require a fertile, deep loam, pH 4-8, with plenty of organic material and manure.


Not enough data was found for a proper graphical assessment of the temperature needs of banana throughout all its development stages.

In general, banana trees prefer temperatures around 27 ºC. Temperatures below 21 ºC negatively affect growth, leaf production and shooting rates. Temperatures below 10 ºC can cause a lethal chilling damage to the plant, though “Mysore”, “Dwarf Cavendish” and “Pome” can tolerate temperatures near 0 ºC.

For plant growth and leaf development, the optimum temperature range could fall between 28 ºC and 30 ºC during the day while optimum temperatures during the night could be between 18 and 26 ºC. Minimum lethal day temperatures fall between 9 and 17 ºC, with an estimated average value of 14 ºC, while maximum lethal day temperatures have been commonly measured at 38 ºC. Minimum and maximum lethal temperatures at night might be 10 ºC and 30 ºC, respectively.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 63BANANA

The maximum temperature for the following phases (flowering, fruit development and maturation) is 38 ºC. For flowering, estimated optimal temperature range between 22 and 31 ºC and temperature of 24 ºC for ripening.


Bananas require 60-100% humidity and and annual rainfall of 1,300-3,600mm. Water requirements increase with age and leaf area and, due to their large leaf area, high winds will increase transpiration rates. As the bunch matures water requirments may be as high as 10mm per day. Soil moisture should not fall below 60-70% of field capacity.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S BANANA64

76

Fi

gure

39.

Ban

ana

wat

er re

quire

men

ts b

y gr

owth

sta

ge: y

ear 1

FIGURE 39. Banana water requirements by growth stage: year 1.

77

Fi

gure

40.

Ban

ana

wat

er re

quire

men

ts b

y gr

owth

sta

ge: y

ear 2

FIGURE 40. Banana water requirements by growth stage: year 2.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 65BANANA

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SESAME66

5.2 Sesame

ECOLOGY

Sesamum indicum is a high value oilseed, also known as simsim, benniseed and gingelly. Grown throughout the topics and sub tropics, there is a high market demand for export to the Middle East and the Indian Sub-Continent.


Sesame is grown from sea level to 1,500m on fertile, well-drained soils. A fine tilth is required as the seeds are very small. Sesame needs thinning after emergence and regular weeding.


Optimal annual average temperatures for growing sesame should be between 24 and 27 ºC. For germination, a minimum temperature of 12 ºC is needed, and preferably above 18 ºC for optimal germination rates. Optimal temperatures for flowering and grain development range from 26 ºC to 30 ºC. Temperatures above 40 ºC cause flower sterility. Growth is significantly reduced below 20 ºC.


Generally 400-500mm of rainfall is required during the growing season. The seedlings are very sensitive to water stress and require between 2.2mm/day to 7mm in Sudan. Heavy rains will wash out the small seeds. In mid-season sesame will require up to 10mm/day but water demand reduces towards harvest.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 67SESAME

79

Fi

gure

41.

Ses

ame

wat

er re

quire

men

ts b

y gr

owth

sta

ge in

the

tropi

cs

FIGURE 41. Sesame water requirements by growth stage in the tropics.

80

Fi

gure

42.

Ses

ame

- Wat

er r

equi

rem

ents

for

Khi

dir

and

Pro

mo

varie

ties

in S

udan

by

grow

th p

erio

d an

d irr

igat

ion

regi

me

(Ahm

ed

&

Mah

mou

d 20

10)

80

Fi

gure

42.

Ses

ame

- Wat

er r

equi

rem

ents

for

Khi

dir

and

Pro

mo

varie

ties

in S

udan

by

grow

th p

erio

d an

d irr

igat

ion

regi

me

(Ahm

ed

&

Mah

mou

d 20

10)

FIGURE 42. Sesame - Water requirements for Khidir and Promo varieties in Sudan by growth period and irrigation regime (Ahmed & Mahmoud 2010).

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SESAME68

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 69SUNFLOWER

5.3 Sunflower

ECOLOGY

Sunflower, Helianthus anuus, a Central American crop, grows well across the World and is mainly grown for oil. Sunflower is mainly grown in East and Southern Africa, where demand exceeds supply. In West Africa palm and groundnut oil predominates.


Sunflower can be grown from sea level to 2,500m but it does not tolerate high humidity. Sunflower does best on deep (1.5m or more), well drained, heavy soils with a p of 6.0-7.5. sandy soils often give poor yields and in Africa sunflower often does well on the clay-rich soils of old termite mounds. Liming is required on soils <pH 6. Sunflower is a heavy feeder and requires fertilisers for good production. Strong winds will cause lodging


Optimal air temperatures for growth range from 18 to 26 ºC, with maximum yields achieved around 22 ºC. Though sunflower can tolerate frost, minimum temperatures should not go below 2°C. The ideal temperature range is 18-30°C, with higher temperatures required for ripening. Night temperatures should not fall below 12°C, ideally 17-22°C.


Sunflower grows in areas with a wide range of rainfall, from 250-4,000mm. Sunflower has a very deep taproot, up to 2m, and is drought-avoiding, but is intolerant of waterlogging. The highest water requirements are at mid-season, and may reach 10mm/day. Rainfall should be low at harvest, < 3mm/day.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S SUNFLOWER70

82

Fi

gure

43.

Sun

flow

er te

mpe

ratu

re re

quire

men

ts b

y gr

owth

sta

ge

Max

imum

tem

pera

ture

s

Min

imum

tem

pera

ture

s O

ptim

um d

ay te

mpe

ratu

res

O

ptim

um n

ight

tem

pera

ture

s

46 4445

.5 ºC

42 40 3840

ºC36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4

6 ºC

24.

5 ºC

02.

5 ºC

15 d

ays

Ripe

ning

30 d

ays

20 d

ays

25 d

ays

30 d

ays

25 d

ays

Germ

inat

ion

and

emer

genc

eEa

rly ve

geta

tive

Late

vege

tativ

eFi

rst t

o la

st a

nthe

sisEm

bryo

filli

ng

23 ºC

-30

ºC

21 ºC

-26

ºC21

ºC -

28 ºC

12 ºC

-22

ºC

20 ºC

-29

ºC

18 ºC

-25

ºC

17ºC

-19

ºC

25 ºC

-30

ºC

17ºC

-22

ºC

FIGURE 43. Sunflower temperature requirements by growth stage.

83

Fi

gure

44.

Sun

flow

er w

ater

requ

irem

ents

by

grow

th s

tage

in th

e tro

pics

and

sub

tropi

cs

FIGURE 44. Sunflower water requirements by growth stage in the tropics and subtropics.

C R O P W E A T H E R A N D C L I M A T E V U L N E R A B I L I T Y P R O F I L E S 71SUNFLOWER

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Crop Weather and Climate Vulnerability Profiles · 2019-04-17 · CROP WEATHER AND CLIMATE 6...

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