Factors affecting soil sub-surface phase of

purple nutsedge (Cyperus rotundus) development

Tal Naamat1,2, Hanan Eizenberg1 and Baruch Rubin2

1 Newe Ya’ar Research Center, ARO; 2 The faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem,

Rehovot

The 2nd International Conference on: Novel and Sustainable Weed Management in Arid and Semi-Arid

Agro-Ecosystems

The problem:Purple nutsedgeA troublesome weedcauses heavy damages in irrigated summer crops

A sweet potato field in Israel infested with purple nutsedge

Photographed by Baruch Rubin

The biology:Mostly vegetative reproduction by tubers and bulbs

The tuber contain many buds It can survive in moist soil long time Although the sub-surface development affects the above ground growththe knowledge of the factors affecting the soil sub-surface development of purple nutsedge is limited

Temperature:

Temperature is considered as a main regulator in purple nutsedge developmentBased on preliminary experiments, temperature data can be converted to physiological age (thermal time) units, expressed in Growing Degree Days (GDD)

Objectives:To study the effect of various environmental conditions on key stages in the sub-surface development of purple nutsedge

Specifically, to study the effect of:•Temperature•Radiation•Tuber burial depth •Desiccation

To appoint the development on a time course of GDD

Key stages that were studied:Accumulation of foliage

biomass Accumulation of sub-

surface biomass

and tuber productio

n Tubers’

sprouting

Emergence

1. Sprouting:

Temperature

Desiccation

Depth

Heat Source

The effect of temperature on sprouting

Temperature (°C)25 30 35 40 45 50 55

Spro

uting

(%)

0

20

40

60

80

100

120

25 30 35 40 45 50 55

Temperature (°C)

2

5.98.305.0

1.100x

eyR2=0.86;

P<0.0001

The relations between temperature and sprouting were addressed for developing a

prediction means for purple nutsedege sprouting80-120 GDD at sprouting

1. Sprouting:

Temperature

Desiccation

Depth

10

15

20

25

30

35

The effect of desiccation on sprouting

15°C

20°C

25°C

30°C

35°C

Tim

e (D

ays)

Thermal time (GDD) accumulation

100 200 300 400 500 600 700 800

Biomass loss (% of T0)0 20 40 60

Spro

uting

(%)

0

20

40

60

80

100

120

Thermal time in pre-treatment (GDD) 0 200 400 600 800 1000

Biom

ass l

oss (

% of

T0)

0

10

20

30

40

50

60

70

The effect of desiccation on sprouting

R2=0.9; P<0.0001

R2=0.95; P<0.0001

Later than 200 GDD

A tuber loses 55% of its biomass

It has 30% chance to sprout

IllustrationIllustration

After cultivation

Control Irrigation at 200 GDD

30% sprouting90-100% sprouting

1. Sprouting:

Temperature

Desiccation

Depth

The effect of tuber burial depth on sprouting

Tested in 2 methods:Field

experiment

Hom

ogen

eous

tem

pera

ture

regi

me

1 17 33 49 65 81 97 11312914516117719320922524125720

25

30

35

40

45

0 cm10 cm30 cm50 cm50 cm

Het

erog

eneo

us te

mpe

ratu

re

regi

me

2 3 4Days from burial

10

20

30

Bud

elon

gatio

n (m

m)

Minirhizothron experiment

0 10 20 30 40 500.0

30.0

60.0

90.0

120.0 0 10 20 30 40 500.0

30.0

60.0

90.0

120.0

0 10 20 30 40 500.0

30.0

60.0

90.0

120.0

Tuber’s depth (cm)

Spro

utin

g)%

( 4 DAP

7 DAP

11 DAP

4 DAP

7 DAP

11 DAP

The effect of tuber burial depth on sprouting

LSD

LSD

0 10 20 30 40 500.0

30.060.090.0

120.0

0 10 20 30 40 500.0

30.0

60.0

90.0

120.0

Minirhizothron expt.

0 10 20 30 40 500.0

30.0

60.0

90.0

120.0

Field expt.

N.SN.S

N.S

N.S

Key stages that were studied:Accumulation of foliage

biomass Accumulation of sub-

surface biomass

and tuber productio

n Tubers’

sprouting

Emergence

2. Underground biomass accumulation3. Tuber production

Temperature

Radiation

The effect of radiation on tuber production

0 10 20 30 40 50 60 700

5

10

15

20

25

30

Control35% shade60% shade90% shade

No. of tubers

No.

of s

hoot

sControl

35% 90%60%

• Natural sun light• 35% shade• 60% shade• 90% shade

The effect of radiation on tuber production

0 10 20 30 40 50 60 700

5

10

15

20

25

30

ControlLogarithmic (Control)35% shade

No. of tubers

No.

of s

hoot

sTemperature and radiation are key factors affecting the sub-surface biomass accumulation

Therefore, both factors and their interactions must be taken into consideration when developing a mathematical predictive model for the sub-surface growth of purple nutsedge

Conclusions:o The sub-surface development of purple nutsedge is environmental related o The effect of sub-surface biomass accumulation on shoots biomass accumulation can be quantified

o The combined effects can be theoretically integrated for the entire model on a GDD time course

oThis empirical model must be validated in field conditions

Temperature

Water Conte

ntRadiat

ion

The predictive model might be of use as a tool in control management; e.g. – to imply on the optimal time frame of control

0 100 300 400

Average time of sprouting

Emergence of deep tubers

Beginning of tuber

production

GDD

Thermal time frame of control

Thanks…My advisors – Hanan Eizenberg and Baruch RubinEWRS - for funding my trip

Newe Ya’ar, the Department of Weed Research:Joseph Hershenhorn, Radi Ali, Daniel Joel,Evgeny Smirnov, Tal Lande, Guy Achdari,Evgenya Dor, Dina Plakhin

The Faculty of Agriculture,Weed Lab

My fellow students