Verification and Development of Best Management Practices for United States Department of Agriculture - Certified Organic Carrots in the Sandy

Soil of Florida’s Suwannee Valley.

Master Internship Plant Production Systems

Ludovica Elena Zampieri MSc. Organic Agriculture WUR reg. nr.: 911115982010 Superviors: Dr. Danielle Treadwell Dr. Gerrie van de Ven Course code: PPS – 70424

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Table of Contents

Verification and Development of Best Management Practices for United States Department of Agriculture - Certified Organic Carrots in the Sandy Soil of Florida’s Suwannee Valley. ............................................................................................................... 1

1. Introduction. ................................................................................................................... 3 1.1 Problem analysis. ..................................................................................................... 5 1.3 Water quality preservation. ..................................................................................... 6 1.4 Carrots in Florida. .................................................................................................... 7 1.4 Research objectives. ................................................................................................ 8

2. Material and Methods. ................................................................................................... 9 2.1. The field trial. ........................................................................................................... 9 2.2 Experimental design. ............................................................................................. 11 2.3 Lysimeters installation .......................................................................................... 14 2.4 Fertilizer application. ............................................................................................. 15 2.5 Sowing of the carrots. ............................................................................................ 18 2.6 Midterm data collection. ........................................................................................ 19 2.7 Statistical analysis. ................................................................................................ 21

3 Results of the midterm analysis. ................................................................................. 22 3.1 ANOVA summary. .................................................................................................. 22 3.2 Yield quality variables. ........................................................................................... 23

3.2.1 Plant density ...................................................................................................... 23 3.2.2 Shoot Length. .................................................................................................... 24 3.2.3 Crown diameter. ................................................................................................ 25 3.2.4 Nitrogen Content in the Root. ............................................................................ 26 3.2.5 Biomass and N partitioning. ............................................................................... 26

4. Discussion .................................................................................................................... 28

5. Conclusions ................................................................................................................. 29

6. Other activities performed as part of the internship experience. ............................ 30

Reference ......................................................................................................................... 31

Appendix 1 ....................................................................................................................... 34

Appendix 2. ...................................................................................................................... 36

Appendix 3. ...................................................................................................................... 37

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1. Introduction. The state of Florida is the second largest vegetable producer in the United States (US), with a total of 47 100

commercial farms and 3.8 million ha reserved for agricultural production (USDA, 2016.State Agriculture

Overview). (Table 1).

Florida has a subtropical savanna climate with a bimodal distribution of rainy seasons. The greatest amount

of precipitation falls in winter and summer, and the average annual precipitation is 1504 mm (Figure 1). The

high precipitation rate allows for the maintenance of the hydrological system, which is composed of 7700 lakes,

13 major rivers, and 27 major springs (Burnett et al., 2003).

Table 1. Florida’s major vegetable crops, planted area and economic value in 1, 000 US $ (USDA. 2016.State agriculture Overview ttps://www.nass.usda.gov/Quick_Stats/Ag_Overview/stateOverview.php?state=FLORIDA).

Crop Planted area (ha)

Value of production (1 000 US $)

Strawberry 10 800 449 770

Tomatoes (total all types) 30 000 382 200

Bell pepper 13 500 209 711

Sweet corn 37 600 160 096

Watermelon 22 500 123 310

Cantaloupe 2 300 11 861

Cucumbers 24 300 116 866

Peanuts 155 000 108 354

Blueberries Missing data

53 656

Snap bean 28 200

Squash 6 000 30 082

Cabbage 8 500 49 422

Sweet Potato Missing data

Missing data

Carrots Missing data

Missing data

Figure 1. Florida climate data. Monthly rainfall and temperature average from 1981 to 2010 for the whole state of Florida (U.S. Climate Data). http://www.usclimatedata.com/climate/florida/united-states/3179#.

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Greater than 30% of the state’s total land area is covered by wetlands (Munson, Delfino, & Leeper, 2005). In

the early 1900s, Florida's wetlands experienced a great drainage and channelization activity that allowed for

the expansion of agricultural areas. This process allowed the State to reach the current agricultural production

levels. The drainage of the wetlands started with the channelization of the Caloosahatchee and the upper

Kissimmee River basins in southern and central Florida (Brockmeyer et al.,1996). Numerous other canals

were dug throughout the state, and additional channels and dikes were built to drain more land for agricultural

development. The complex network of drainage channels (Figure 2), which were built over the last century, is

still present and ineffectively diverts water with agricultural residues into the adjacent water bodies, negatively

Many studies assess the transportation of nitrates (NO-3) from the drainage canals of the agricultural areas to

surrounding water bodies, contributing to eutrophication and depletion of aquatic ecosystems (Boyer et al.,

2000; Corbett et al., 2002; Hernández et al., 2012). Examples of ecosystems affected by a high load of

nutrients are the Lower St. Johns River Basin, Biscayne Bay, Florida Bay, and Lake Okeechobee (Caccia and

Boyer, 2000). The abundant precipitation combined with the great network of channels allow for an easy

transport of nitrates in the surface water of the surroundings waterbodies (Carriker, 2000).

impacting the water quality and its biodiversity (Munson et al., 2005).

Two additional challenges to maintaining Florida’s water quality include the significant water use demands

from its population of 20 million residents and 100 million visitors annually and its Karst topography. The

peninsula of Florida developed from volcanic activity and accumulation of marine sediments. As a result, the

parent material of Florida’s soils is primarily composed of carbonate rock (limestone, dolomite and marble),

eroding over time to form karst, characterized by an interconnected network of underground streams and

caves (Allen and Main, 2015; Kuniansky et al., 2012). The karst is exposed on the surface in some places,

or may be buried with up to 200 ft. of minerals and organic matter. Transmission of precipitation and irrigation

water to the Floridan aquifer system occurs at different rates throughout the area, but on deep course sands

with high porosity such as those in the Suwannee Valley, it is estimated to be significant (Kuniansky et al.,

2012). Therefore, producers of agricultural crops are encouraged to apply nitrogen judiciously, taking care not

to apply more than the crop can utilize to avoid risk to water quality. In Florida, careful resource management

is an essential condition for environmental preservation.

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Figure 2. Florida’s hydrological system in 1900 and 1992. http://www.nasa.gov/audience/formedia/features/MP_Photo_Guidelines.html

1.1 Problem analysis. Clean water is a crucial resource that supports different human activities. In the last decade nutrients, inputs

to water bodies have increased, degrading the water quality of many ecosystems.

Eutrophication is one of the most common causes of degradation for aquatic ecosystems in Florida, as in other

parts of the world (Carriker. 2000; Magley and Joyner, 2008; Brockmeyer 1996). Eutrophication is caused by

an excessive growth of algae and aquatic weeds that negatively interfere with the designated use of the

waterbody. This exceptional algae growth is caused by a high input of nutrients that have a fertilizer effect on

the algae population. N is considered to play a significant role for eutrophication, because of its high mobility

in the soil solution and because of is the immediate effect on algae growth. Since N is the most limiting factor

for aquatic plants’ growth, it causes a rapid increase in algae biomass when it becomes available (Mason,

2002; Rivett, Buss, Morgan, Smith, & Bemment, 2008). The excessive growth of algae leads to a loss of quality

in the water bodies that can be assessed as loss of biodiversity, alterations of flora and fauna (Carpenter et

al., 1998; Mason, 2002; Vitousek et al., 1997).

It emerges that agricultural activities are one of the primary sources of N inputs to watersheds. For example,

it has been estimated that 70% to 80% of the nitrate (NO-3) in surface and ground water, is of agricultural origin

(Carpenter et al., 1998; Rivett et al., 2008). These data indicate that limiting the inputs of nitrogen from

agricultural areas to watersheds can have significant impacts for aquatic ecosystems.

Nitrogen is an essential element for plant nutrition, and it is supplied in different fertilizer forms to improve crop

yields. One criticism of modern agriculture is that high inputs of fertilizer overpowered the natural nutrient cycle

(Figure 3), adding more nitrogen than the amount removed by crops (Carpenter et al., 1998; Howarth & Marino,

2006). Nitrogen supplied through fertilization in the plant available forms NO3- and NH4

+ is particularly

susceptible to leaching. These nitrate ions have high mobility in the soil because of their weak interactions with

the negatively charged matrix of most top soils. Hence, soils with high infiltration rates and low nutrient

retention capacities, such as sandy soils low-activity clays, and soils with low organic matter content, are

particularly conducive to NO3-leaching (Figure 3). This effect is enhanced in wet areas where precipitation

rates exceed soil field capacity. Therefore, N surpluses in the agricultural systems can quickly become a

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source of transported nitrate from the farming system to groundwater through leaching (Schroth et al., 2001).

To limit nitrate leaching, and consequently the risk of eutrophication, fertilizer inputs provided to crops should

be carefully planned (Carpenter et al., 1998; Pimentel et al., 2005).

Figure 3. Impact of fertilization and other cultural practices in vegetable fields on the steps of Nitrogen cycle. Nitrogen fertilizer use (UC Davis, 2013). http://calag.ucanr.edu/Archive/?article=ca.E.v067n01p68.

1.2 Water quality preservation.

To limit agricultural inputs to the aquatic ecosystem, the Florida Department of Agriculture and Consumer

Services, in collaboration with researchers at the University of Florida developed a series of Best Management

Practices (BMPs). BMPs are guidelines for resource management during crop production, and emphasize

conservation of water and preservation of water quality. They cover four major areas:

nutrient management advising on fertilizer use;

pest management advising pesticides;

water management advising usage and discard water;

sediment management, monitoring the management of sediments on and around the production area.

BMPs can have specific indications for certain sensitive areas and are usually specific for each type of crop

(Florida-IFAS, 2015).

In 1972, the US government instituted the Clean Water Act (CWA) in response to growing concerns over water

quality. This federal law establishes Total Maximum Daily Loads (TDML), which are determinations, based on

scientific evidence, of the amounts of a given pollutant that a water body can absorb and still meet the water

quality standards that protect human health and aquatic life (EPA, 2016). In 1999, the Florida Legislature

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enacted the Florida Watershed Restoration Act (FWRA), to protect Florida's waters through the Total Maximum

Daily Load (TMDL) program. This program protects water bodies by monitoring the pollution from point sources

(sources that discharge through a discrete conveyance) and nonpoint sources (which are sources contributing

to pollution caused by rainfall moving over and through the ground). By the FWRA, the Florida Department of

Agriculture and Consumer services (FDACS), develops, adopts and assists with the implementation of BMPs

to protect and conserve water sources. In this respect, the University of Florida’s Institute of Food and

Agricultural Science (UF/IFAS) plays a significant role in developing and implementing BMPs by conducting

randomized, replicated trials to evaluate the impact of irrigation and fertilization rates on yield and water quality.

These data are used to validate and refine BMPs.

1.3 Carrots in Florida. Carrot (Daucus carota L.) isa crop with an important commercial value. Carrots have important nutritional

properties. For example, a medium size root contains the daily amount of vitamin A that is required in an adult

diet. Commercial carrot production has an economic share in the US $500 million, with a yearly production of

2 million tons, and 40 000 ha cultivated (Farrar et al., 2004). Carrots are an important crop in Florida’s

vegetable production estimated to be estimated at 2 900 ha (Hochmuth, Brecht, & Bassett, 1999). Historically

the production was concentrated on the histosols in the central part of the State. However, this area was put

under protection because it was identified as a potential source of nutrient contamination for Lake Apopka,

production was moved on the deep sandy soils in the northern area of the State (Hochmuth, Brecht, & Bassett,

1999).

The current BMPs practice for conventional carrot production recommend a fertilization of 175 lb/acer (196 kg

N/ha) (UF/IFAS, 2016). Organic carrots comprise 14% of the domestic carrot market, and are in demand by

buyers in Florida and throughout the US (Florida-IFAS, 2015). Price premiums for organic carrots are

significant; retail prices for bagged organic carrots were on average 30% greater than conventional carrots for

the past 7 years (Jaenicke and Carlson, 2015). Farmers in North Florida are expected to plant as much as an

additional 2023 ha of organic carrots in the next few years if successful systems are found. Most of the carrots

produced on those farms will be sold to processors for cutting, shaping and bagging as snack-size carrots

(baby carrots) and packaged as fresh, whole carrots (tops removed) in 1, 2, or 10 kg approximately cello bags

of whole carrots, and distributed to mass market retailers in Florida and beyond (Florida-IFAS, 2015).

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1.4 Research objectives. The research objective is to define best management practices (BMPs) of nitrogen fertilizer for organically

grown carrots, to initiate recommendations of N-BMPs for organic carrot cultivation. Organic carrot production

on a large scale is new to North Florida, and as a result, little or no research is available on which a BMP can

be written. This research project will determine organic nutrient management programs that will maintain high

yield and quality while at the same time minimize the impact on the environment.

The goal of this project is to develop evidenced-based recommendations for nutrient management in organic

carrots to support the success of North Florida vegetable producers while conserving our state’s natural

resources.

This objective will be evaluated in two field trials, one that examines N fertilization rates, and one that examines

fertilizer applications strategies, addressing the following research questions:

1) Which N rate on organically grown carrots shows the best environmental and agronomical performance?

2) Which of the application strategies is the most effective for the employment of organic fertilizer?

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2. Material and Methods.

2.1. The field trial. The field trial (Figure 5) is located at the Suwannee Valley Agricultural Extension Center (SVAEC) near Live

Oak, Florida USA (30°18'54.3"N 82°53'47.1"W). The soils in the experiment area are classified as deep sands,

which means that have a sandy texture with a deep ground water table. The soil of the field is a mineral soil

with a sandy-loam texture (Table 2).

Table 2. Soil characteristics of the field trial from pre-trial soil samples.

Soil parameters Values (South side) Values (North side)

Soil pH 6.0 6.5

Mehlich-3 extractable P 170 ppm 153 ppm

Mehlich-3 extractable K 31 ppm 20 ppm

Mehlich-3 extractable Mg 21 ppm 32 ppm

Mehlich-3 extractable Ca 337 ppm 394 ppm

To develop an N fertilization recommendation for organic carrot cultivation, typical production practices

employed by the farmers of the area were used. ‘Choctaw’ was the cultivar selected for the trial as it is a variety

widely used in organic farming and an adopted cultivar in this area. ‘Choctaw’ is a larger carrot typically used

for fresh pack whole carrot.

Although scarce precipitations recorded throughout the month of November 0.25 mm, weather conditions

precipitations, air temperature recoded and soil temperature were generally favorable for carrot production,

from October 2016 to April 2017 (Figure 4).

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Figure 4. Weather data recoded at the field trial site. Data were recorded at the agro meteorological station in Live Oak and downloaded from the Florida Automated Weather Network (FAWN) database (https://fawn.ifas.ufl.edu/data/reports/?res)

Figure 5. Map of the field trial with repetitions blocks, and experimental setup at the UF/IFAS Suwannee Valley Agricultural Extension Center. The blue squares indicate the four blocks of the Application Strategy study, while the orange squares indicate the four blocks of the N Rate study. The dashed blue line is the curvature of irrigation reach from the center pivot.

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2.2 Experimental design. The N-BMPs recommendations for organically-grown carrots will be evaluated in two different trials: one that

examines N fertilization rates (N Rate); and one that tests fertilizer applications strategies (N Application

Strategies). Both experiments are located on the 1 ha organic unit, certified United States Department of

Agriculture (USDA) Organic land (Quality Certification Services, Gainesville, FL). As such, all inputs and

methods were compliant with the USDA National Organic Standards, were included in the experimental

farming system plan, and approved by the certification agency prior to use. In each trial, five treatments (T)

are arranged in a randomized complete block design and replicated four times for a total of 20 plots (Figures

4a and b). The production beds in each experiment were 18 m long and 1.30 m wide. One production bed

represents an experimental unit (a plot). The total experimental area in the N Rate study and the N Application

Strategy combined is 0.10 ha (Figure 4a; Figure 4b and Figure 5).

In the N Rate trial, five treatments of different N rates were tested with an organic fertilizer, using 56 kg N

increments starting from a rate of 168 N kg ha-1, and reaching maximum rate of 394 kg N ha-1. These rates

were selected by researchers of the extension program of the Institute of Food and Agricultural Science of the

University of Florida (UF/IFAS), based on previous research for best management practices in conventional

carrot, and adjusted for the 100 LBF (liner bed foot) estimation method. This method accounts for not fertilizing

the space between cultivated beds (Hochmuth and Hanlon, 2015) (Appendix 1). The UF/IFAS

recommendation for conventionally-produced carrot is in the 76-102 kg N ha-1 range, depending on the time

of year and cultivar selection. In this trial, a control rate (0 kg N) was not included, as previous experience of

the research team determined it would not be possible to obtain measurable yield without a minimum fertilizer

application on the sandy soils of this area.

In the second trial, N Application Strategies, the effect of timing of application was investigated by selecting

the median rate of the N Rate study, 281 N kg ha-1, into five different application schedules (Table 4):

A. Three applications of N: 50% of the median rate will be supplied prior to seeding, 25% after

establishment, and 25% at the halfway point of the growing season.

B. Three applications of 25%, 25% and 50% the median rate, from seeding to the halfway point of

the season.

C. Three applications of 33.3% median rate, from seeding to the halfway point of the season.

D. Four applications: 40% of the median rate applied at seeding, and remaining applications split in

decreasing amounts of 30%, 20%and 10%.

E. Five applications: 1/12th pre-seeding, 40% of the rate half way of the season, and 3 equal

application of 20% the rate. This rate slightly higher than 100% because a delay on the original

working plan forced the research team to redistribute the rates (Paragraph 2.5).

These treatments were selected to create different soil N environments based on previously published

research on carrot phenology, and the assumption that the crop has a different demand for N depending on

its phenological phase, consequently a different capacity of N uptake. Therefore, to find the best combination

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of fertilizer amount per application and application timing that allowed for the best environmental and

agronomical performances, a range of fertilizer application were selected.

In the application strategy experiment, the amount of N applied correspond to the median rate, T3’s rate of the

N Rate trial, (Table 3) of the first trial (281.25 kg N /ha) The N rate is split in different applications (Table 4) as

it was previously described.

Table 3. Treatment abbreviations and the seasonal amount of N applied on each plot of the N Rate trial converted in kg ha. N rate (kg/ha) are the amounts of N selected for the experiment. Adjusted N expresses the amount of N distributed on the plots of the experiment calculated with Equation 1.

Treatment abbreviation

N rate (kg/ha) Adjusted N Rate (kg/plot)

T1 168 12.93

T2 225 17.26

T3 281 21.51

T4 337 25.84

T5 394 30.18

Table 4. Treatment abbreviations for the Application Strategy trial. Letters are used to differentiate the treatment of the application method study to the treatment of the N rate trial. Different split application of the median rate (280 N kg ha-1).

Treatment abbreviation

Application strategy as described in the experimental designee section.

T1 A

T2 B

T3 C

T4 D

T5 E

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Figures 4a and 4b. Experimental design of two field trials at the UF/IFAS Suwannee Valley Agricultural Extension Center. a) Represents the experimental set up for the N Rate study, while b) illustrates the set-up of the N Application Strategy study. The letter T1...n refers to the treatment, while the letter L in the blue shaded boxes indicates approximates the lysimeters’ position in the plots. Specific locations were measured, recorded, and flagged after installation.

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2.3 Lysimeters installation Drainage lysimeters were installed in the plots of the N Rate study to monitor nitrate leaching. The lysimeters

were designed and developed by UF researchers (M. Dukes et al., unpublished data), and improved by the

team at SVAEC in Live Oak by using higher quality materials and adding the polyspun fabric layer. Each

lysimeter was assembled using a plastic barrel that was cut in half obtaining a U-shaped container 0.20 m

deep, and about 1 m long. This container served as the base of the lysimeters and included a soil solution

collection tube (made of PVC plastic with a permeable membrane on the soil side) that was inserted to allow

collection of gravity-fed soil solution (Figure 6a).

To ensure stability to the lysimeters and to avoid a miss positioning of the water collection tube, landscape

gravel was placed at the bottom of the lysimeters and over the collection tube (Figure 6b). A sheet of polyspun

landscape fabric with pore sizes smaller than sand grains (to selectively allow soil solution to pass through but

inhibit sandy soil) was positioned on the top of the rocks (Figure 6c), and final layer of native soil was added

on top in the reverse order of stratification that it was removed (Figure 6d).

The lysimeters were installed under the production beds on a depth of 0.80 m. Top soil was removed first and

set to one side, then the deeper alluvial layer of soil was removed with an excavator. The remaining depth

was excavated by hand using a shovel. This procedure was used to ensure consistency with the depth at

which the lysimeters were buried. Inclination and alignment of the lysimeters were verified with a bubble level.

A total of 12 lysimeters, three per repetition, were placed in the field using a predetermined stratified grid

method where lysimeters were placed in alternating locations to avoid risk of lateral water movement between

lysimeters placed side by side in neighboring plots (Figure 1a).

Figure 6. Lysimeters installation and assembly process in the N Rate study at the UF/IFAS Suwannee Valley Agricultural Extension Center. One lysimeters was installed in each plot in the study.

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2.4 Fertilizer application. Prior to each experiment, soil samples were collected and submitted to the UF/IFAS Extension Soil Testing

Laboratory for analysis of macro and micronutrient content. The soil analysis did not indicate the amount of

soil N prior planting. Fertility recommendations were limited to an application of boron at a rate of 0.18 kg a-1.

Dolomitic lime was applied the previous fall, and no additional lime was needed. Soil pH in the study area

measured 6.5 and 6.0 and was deemed sufficient. Potassium levels were variable throughout the field but

were primarily in the “middle” range, meaning crop response to additional K would be modest, but some

additional K would have some advantage. Phosphorus levels were primarily “very high”, typical for this area

due to the native soil P (Florida’s phosphate mines supply 40% of the worlds’ agronomic phosphorus).

The fertilizer employed in the trial is a blended fertilizer approved for use in USDA certified organic systems,

made exclusively of poultry litter (Perdue AgriRecycle, LLC, Delmarva, MD) with an analysis of 3% total N, 2%

P2O5 and 3% K2O. In the N Rate trial, the amount of applied N for each treatment is calculated starting from

the recommended fertilizer amount for a 4.5 linear bed foot (LBF) cultivation system, adjusted for the N

concentration of the fertilizer (3%) and the actual length of the production plots. An average of 34 day is

expected for the mineralization of the N in the in organic fertilizer. This assumption is based on research on

organic N turn over, tested in incubation with 40 different soil (UF/IFAS, 2015).

The five adjusted fertilizer rates (Adj. Fert.) are the amount applied per plot, which corresponds to the

experiment’s treatments (Table 1). The fertilizer inputs were estimated on the base of typical rates for a 4.5

LBF units (Rates 4.5 LBF). The calculation method for LBF is indicated in Appendix 1. The amount of fertilizer

for each treatment was calculated according to the equation described below (Equation 1).

Equation 1.

Adj. Fert = (((((Rate of 1.6 LBF (kg ha − 1)/ fertilizer N (%)) ∗ 73 (100 LBF ha − 1))

∗ difference in area (%)) ∗ Exp. Area (a)) ∗ 0.2) ∗ 0.25

The rates given for a 1.6 LBF spacing, are the target fertilizer application in kg per ha converted to kg

per 100 LBF (Appendix 1).

N is the estimate of readily available N in the fertilizer utilized in the trial (3%).

73 (100 LBF/a)) are the units of 100 LBF in one ha for a bed spacing system of 1.6 LBF.

The difference in area (%) is an adjustment to the fertilizer rate, obtained, by knowing the difference

in area, 3.701% less area, between a 1.6 LBF bed spacing and the actual spacing utilized in the trial

1.5 LBF.

Exp. Area (a) is the experimental area that is occupied by the plots in the N Rate study. There are 20

production beds, each 1.6 m wide and 18m long (18*1.6*20 = 576 m2 = 0.0576 ha).

0.20 is the percentage of applied N to each bed from the treatment (one per treatment). There are five

treatments in the experiment, therefore 1 bed represent 20% of the fertilizer applied to the area for the

corresponding rate.

0.25 represents the fraction of fertilizer that is applied in each treatment on one experimental plot,

being one plot a quarter of the experimental area.

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In the N Rate trial, 50% of the total amount of fertilizer applied was applied pre-sowing. Knowing that the

fertilizer spreader had a maximum drop of 1226.25 kg ha-1, the maximum number of passes done by truck

were estimated per each treatment, and the remaining fertilizer was spread by hand (Table 5). Fertilizer was

lightly incorporated with a rototiller set to mix only the top 5 cm of soil on the bed. Fertilizer additions that

occurred after carrots emerged were incorporated with hand tools customized to fit between carrot rows without

disturbance. In the attempt to distribute as precisely as possible, the amounts of fertilizer to spared by hand,

were weighed on a scale that was brought to the field. A bucket was use as a tare and the and the fertilizer

amounts to distribute was weighed for each treatment.

In the N Application Strategy trial, fertilizer as applied in the same way as in the N Rate study. The rate

corresponding to a split application of T3 and applied in each treatment as described in the experimental

design. The fertilization events were scheduled on the base of the assumed developmental stages of the

carrots counting the day after sowing and by in field observation of the shoot development (Feller,1995; Meier,

1997;Guanglong, 2016).

Table 5. Fertilizer application plan in the N Rate study. This table shows the amount of fertilizer applied with the first fertilization event and it represents 50% of the total N amount that was applied during the trial, in the N application rate trial.

N Rate Treatments

Fertilizer Application

(kg/ha)

Number of Tractor Passes Needed (1 226 kg/ha per pass)

Total Fertilizer

Applied by Spreader (kg/ha)

Remaining Fertilizer to

be Applied by Hand (kg/ha)

Per Bed by Tractor

(kg/0.002388 ha)

Per Bed by Hand

(kg/0.002388 ha)

T1 2813 2 2452 361 5.86 0.86

T2 3757 3 3679 78 8.78 0.19

T3 4682 3 3679 1004 8.78 2.40

T4 5626 4 4906 721 11.71 1.72

T5 6570 5 6131 361 14.64 0.86

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Table 6. Distribution of the fertilizer in the application strategy trial expressed in weeks after sowing (WAS). Stages correspond to leafs development (1); formation of side roots (2); 3rd true leaf stage tap root formation (3); development of tap root 30% of the final size (4) (Hack et al., 1992).

Nitrogen in % of Total N Application

WAS STAGE N Demand Date A B C D E

0 1 low 14/10/16 50 25 33.3 40 1/12th

1 1 low 21/10/16 0 0 0 2 1 low 28/10/16 0 25 0 3 2 mod 04/11/16 25 0 33.3 10 4 2 mod 11/11/16 0 25 0 10 40

5 2 mod-high 18/11/16 25 0 0 10 6 2 mod-high 25/11/16 0 25 33.3 10 20

7 3 high 02/12/16 0 0 0 10 8 3 high 09/12/16 0 0 0 10 20

9 3 mod 16/12/16 0 0 0 10 3 mod 23/12/16 0 0 0 20

11 3 mod 30/12/16 0 0 0 12 3 mod 06/01/16 0 0 0 0

13 3 mod 13/01/16 0 0 0 0

14 4 low 20/01/16 0 0 0 0

15 4 low 27/01/16 0 0 0 0

16 4 low 03/02/16 0 0 0 0

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2.5 Sowing of the carrots. Following lysimeters installation and prior to sowing, cultivation beds were reshaped and cultivated with a

rototiller to eliminate emerging weeds.

The first carrots sown on October 21, 2016 using a Spider (Sutton Agricultural Enterprises, Salinas, CA)

vegetable seed planter (Figure 7). This seeder is used widely among farmers in our area. This seeder has an

internal high-density sponge that attracts small seeds by electrostatic charge, then releases that charge and

drops seed in place in rows in the soil approximately 0.63 cm deep and then presses the soil firmly with a

roller. Seeds were coated with an organic compliant zeolite to reduce accumulation of static charge in the

planter.

After emergence, it became apparent that the planting configuration was going to interfere with mechanical

weeding, a necessary strategy in the absence of effective compliant herbicides. It was decided to re-plant the

carrots in a different setting to facilitate cultivation. Beds were mechanically cultivated with a rototiller and

reshaped with a bed shaper.

The second sowing occurred on November 14, 2016 using the same seeder and adjusting the hoppers to fit

the new planting configuration. Carrots were planted at a depth of 0.63 cm in 4 rows per bed. Rows were

spaced equidistant from one another 16.50 cm apart to facilitate mechanical weeding. The population target

was set at 31 live plants per bed foot, or 410,000 plants per acre. The amount of seed needed to reach the

desired plant population was calculated using a planting calculator model (Appendix 2).

The planter was calibrated knowing the speed at which seeds were dropped and the seed per gram count,

targeting 43.09 g. of seed per bed in four minutes. A couple of trials were conducted to set the proper working

speed of the seeder. The amount of seed dropped in 4 minutes and the speed that the tractor needed to

accomplish one pass on one production bed was recorded by collecting the seed dropped in buckets and

weighing these on a scale. It was decided to keep a seeding rate of 46.70 g in 4 minutes per bed, to

compensate for loss after emergence that according to the model was estimated to be 15% of the seeding

rate (Appendix 2).

Four weeks after sowing, the emergence rate was measured for all the treatments and in all replication,

counting the planets emerged in the four rows along a randomly selected section, equal 1m, of the production

bed

Carrots were scouted weekly for insects, diseases and weeds. Weeds were mechanically cultivated in the row

by hand in the absence of an appropriate cultivator for this planting regime and crop until carrot foliage covered

the bed surface. Weeds emerging from the carrot canopy were rouged by hand weekly. No insect pests were

observed. Special attention was given to Alternaria leaf spot management by applying preventative fungicide

applications weekly beginning February 17 through March 27. Products used were compliant with organic

agriculture standards formulations and included Actinovate AG (Streptomyces) and Nordox (copper).

19

Figure 7. Vegetable seed planter utilized to plants carrots in the field trials.

2.6 Midterm data collection. The mid-term analysis, was conducted only on the N Rate study, because in the Application strategy trial many

treatments had received only a part of the designated rete (Table 6), making a comparison between the

treatments pointless at this stage.

The midterm analysis was conducted to verify the effect of the different nitrogen rates on carrot development.

An interim data collection offered the opportunity to increase the amount of information on the relevant

processes governing the crop development and resource utilization. The data collection aimed to assess the

effects of treatments on yield, quality, and nitrogen use by carrot, a set of relevant variables was selected

based on previous studies (Watkinson & Hara, 1996; Suojala, 2000; Warncke, 1996) (Table 7).

According to Wein and Guanglong, the five carrot development phases include: 1) root emergence, 2) root

elongation, 3) leaf emergence and foliar development, and finally 5) root expansion (Figure 8). Samples were

collected seven weeks after sowing on January 24, 2017 during the middle stage of carrot development

(Feller,1995; Meier, 1997;Guanglong, 2016; Wien, 1997). The seven variables measured in the field were

collected from a subsample in each plot in each replicate (Table 7). The plants were harvested from the two

central rows of the production beds, from where plant density was recorded. From the designated portion, all

the plants were harvested to ensure a sample size with enough weight for the further analysis of N content.

The sampling took place one bed at the time starting, in all four replicates.

20

Figure 8. Carrot developmental stages day after sowing as determined by Guanglong (2016). Error bars represent SD among three independent replicates. Data are the mean ± SD of three replicates. Means denoted by different lowercase letters significantly differ at P < 0.05 between developmental stages according to Duncan's multiple range test.

Table 7. Variables selected for the midterm analysis. Variables are subdivided between the ones that were directly collected in the field and the ones that were analyzed in the lab.

Variables measured in the field

Units Variables analyzed in the laboratory

Units

Plant density Plants/0.25 m2 N/A ---

Shoot fresh weight g Shoot dry weight g

Shoot N concentration %

Root fresh weight g Root dry weight g

Root N concentration %

Shoot length cm N/A ---

Root length cm N/A ---

Crown diameter mm N/A ---

Plant density.

The area on where plant density was recorded was randomly selected along the production beds, excluding

1.5 m from each end of the bed and areas on the top of the lysimeters. The frame width was designed to

include all four carrot rows, and the length was determined by calculation as the length necessary to establish

a quarter meter sampling area within the frame itself. Frames were made by hand prior to sampling using PVC

pipe, elbows, and plumber’s glue. The dimension of each frame was extremely accurate each piece was

carefully measured using measuring tape before assembling the frame. The inner curvature of the elbow was

taken in account in the measurement of the of the sides’ length and subtracted from the pipes length when

catted. Final dimensions of the frame were measured and assed to be 69.85 x 35.80 cm, embedding an area

of 2500.63 cm2 (0.25 m2). The plants on the outside rows were counted first in situ, and the inner two rows

were counted at excavation (see plant fresh weight below). Density was calculated as the sum of plant

numbers in inside and outside rows.

21

Since all the data in the field were recorded form the area selected for plant density, they are all based on a

same surface area. For the easy of the interpretation, the data presented in the result section are converted

on a per hectare scale.

Plant fresh and dry weight, length, and crown diameter.

To avoid too much disruptive sampling, from the same section were plant density was recorded, the plants

from the middle two rows were excavated with a shovel, carefully lifting soil and roots that were removed gently

by hand, ensuring the tap root was removed intact with as many secondary roots as possible, with tops

attached. The harvested plants were immediately brushed with a soft bristle brush to remove any remaining

soil. Each plant was numbered so the top weight and its corresponding root weight could be summed for a

total plant weight during data management. Tops were removed at the suture with clippers, the crown diameter

measured with an electronic caliper, and tops and roots were weighed then measured for length individually

and recorded in the field. Each top was placed in a labelled paper bag. Correspondingly, each carrot root was

placed in separate labelled bag. After field sampling, the carrots were transported to the laboratory on UF

campus and placed in a forced-air oven at 65 °C for 75 h, at which time they were determined to be dry (at

constant weight). Dry weight of shoots and roots were recorded individually per plant. After The amount of

plant collected from each production bed depended on the number of plant present on the bed.

Determination of N content.

After dry weight was recorded, the plant samples were submitted to the UF/IFAS Extension Plant Analysis

laboratory that determined the N concentration for shoot and root. By the department protocol the analysis

were carried out by the technician of the laboratory as this

2.7 Statistical analysis.

The Analysis of variance (ANOVA) was conducted for each of the dependent variables and analyzed during

the midterm assessment, to detect effect the effect of the treatment on the experimental variables. Significance

was set at p0.05.

The means of each group of experimental variables, defining development the development of the crop,

(Table 9), were analyzed for at each treatment (Table 8), which is the amount of fertilizer applied in each

treatment (T1…n) until the midterm data collection.

Before executing the analysis, data were graphically checked to verify the assumption of a normal distribution,

and the homogeneity of variance was checked performing Levene's test. The test was not significant for all

the variables.

The goal of this analysis was to determine the treatment’s effect on physiological processes at the time of the

midterm collection. Significance was set at p 0.05.

22

Table 8. Treatments (T1…n) with the corresponding amounts of fertilizer applied and N (kg/ha) until the midterm data collection.

N Rate Treatments

Fertilization rate (kg/bed)

Total N applied (kg/ha)

T1 9.94 125

T2 13.28 166

T3 16.55 207

T4 19.88 250

T5 23.03 288

Table 9. Test of Homogeneity of Variance. The significance (Sig.) is higher than 0.05 meaning that the assumption of homogeneity of variance is meet.

Variables Name Levene

Statistic

Sig.

Crown diameter (mm) 1.539 0.241

N content Shoot DM (%) 1.620 0.221

N content Root DM (%) 1.700 0.202

Plant density (plants/m2) 0.498 0.738

Root dry weight (g) 1.147 0.372

Shoot dry weight (g) 1.644 0.215

3 Results of the midterm analysis.

3.1 ANOVA summary.

The analysis of the Experimental variables where conducted per mean of the production bed, which represents

one experimental unit with one treatment. Each treatment had four repetitions for a total of 20 production beds

(20n =5treatments x 4repetitions).

From the analysis of variance, it resulted that there is no significant effect of the treatment on the investigated

variables as the significance, of both the F-value and the P-value, is larger than 0.05.

This result indicates that the effect of different fertilization rates could not be detected at this stage.

23

Table 10. Summary of the analysis of variance Sum of squares, degrees of freedom (df), mean Square, F-value (F) and significance (Sig.) of the treatment on yield quality parameters.

ANOVA

Sum of

Squares df Mean Square F Sig.

Crown diameter (mm) Between Groups 2.368 4 0.592 0.982 0.447

Within Groups 9.041 15 0.603

Total 11.409 19

N content Shoot DM (%) Between Groups 0.091 4 0.023 0.070 0.990

Within Groups 4.861 15 0.324

Total 4.952 19

N content Root DM (%) Between Groups 0.597 4 0.149 2.310 0.106

Within Groups 0.969 15 0.065

Total 1.565 19

Plant density (plants/m2) Between Groups 266.200 4 66.550 1.005 0.435

Within Groups 993.000 15 66.200

Total 1 259.200 19

Root dry weight (g) Between Groups 0.782 4 0.196 0.405 0.802

Within Groups 7.241 15 0.483

Total 8.023 19

Shoot dry weight (g) Between Groups 2.151 4 0.538 0.625 0.652

Within Groups 12.905 15 0.860

Total 15.056 19

3.2 Yield quality variables.

3.2.1 Plant density The treatment with the greatest plant density, at the time of the midterm analysis, was T3 (207 kg N/ha) and

the lowest was T1 (125 kg N /ha) (Figure 9). The other fertilization rates appear to have intermediate

performances with similar plant densities. The pant density measured in the midterm analysis matched the

trends recoded of the plantlets emergence measured at the 4th week after sowing (Figure 10).

24

Figure 9. Means of the plant density, at the time of the midterm analysis, for at the 5-fertilization rate T1= 125 kg N/ha, T2=160 kg/ha, T3=207

kg/ha, T4=250kg/ha, T5= 288 kg/ha.

Figure 10. Mean values of plant emerged plants per treatment in the different treatments, at the forth week after sowing (5-fertilization rate T1=

125kg/ha, T2=160 kg/ha, T3=207 kg/ha, T4=250kg/ha, T5= 288 kg/ha).

The number of emerged plantlets were the highest in T3 where the mean emerged plants was 31 (plants/m).

Followed by T2, T5, T4 T1, with 29, 27, 23 (plants/m) respectively (Figure 10).

3.2.2 Shoot Length. The mean highest shoot length was recorded in T1, while the lowest in T5. The other treatments T2, T3 and

T4 were in the between of the two, showing decreasing length at increasing fertilization rates (Figure 11).

0

10

20

30

40

50

60

70

80

90

100

110

120

130

T1 T2 T3 T4 T5

Pla

nt

den

sity

(p

lan

t/m

2)

Tretments

0

5

10

15

20

25

T1 T2 T3 T4 T5

Eme

regd

pla

ntl

ets

(m)

Tretments

25

Figure 11. Recorded shoot length in the different Treatments (5-fertilization rate T1= 125kg/ha, T2=160 kg/ha, T3=207 kg/ha, T4=250kg/ha, T5= 288

kg/ha)

3.2.3 Crown diameter.

Similarly, to shoot length, crown diameter showed a declining trend at highest fertilization rates. T1 resulted

the treatment with highest mean, while T5 had the lowest. (Figure 12).

Figure 12. Means of crown diameter recorded in the different treatments. (5-fertilization rate T1= 125kg/ha, T2=160 kg/ha, T3=207 kg/ha,

T4=250kg/ha, T5= 288 kg/ha).

0

2

4

6

8

10

12

14

16

T1 T2 T3 T4 T5

SHo

ot

len

ghth

(cm

)

Treatments

0

1

2

3

4

5

T1 T2 T3 T4 T5

Cro

wn

dia

met

er (

mm

)

Treatments

26

3.2.4 Nitrogen Content in the Root.

The nitrogen content in the root is presented as the mean of the treatments. The treatment with the highest N

concentration was T3 with (2.09%). The treatment with the lowest N content was T5 (1.6%). While T1, T2 and

T4 showed very similar results with a content of N in the root of 1.97%, 1.98% and 1.97% respectively (Figure

13).

Figure 13. Percentage of Nitrogen content in the carrot root. of the at different fertilization rates (5-fertilization rate T1= 125kg/ha, T2=160 kg/ha,

T3=207 kg/ha, T4=250kg/ha, T5= 288 kg/ha).

3.2.5 Biomass and N partitioning. Since At this stage of the root expansion stage (stage 5), the shoot was the organ with the largest biomass

accumulation, ranging between 60% and 72% of the total biomass weight. Root biomass ranged between 28%

and 39 % of the total (Figure14).

T2 was the fertilization rate with the most harvested biomass. Although T4 was the treatment with the, lowest

harvested biomass, the results indicated also, that T2 and T4 had highest harvested root biomass. Variations

in the proportions of shoot’s and root’s biomass between treatments were minimal (Figure 14).

Hochmuth et al. (2006) report an average root yield, for the carrot cultivar Choctaw, of 4 t/ha. However, the

yield recorded in the study was of full size carrots, while the yield presented in this report are of not fully

developed carrots.

The harvest biomass seams low because the carrot size at the time of harvest was still very small. However,

it is not possible to further analyse the dataset.

0.00

0.50

1.00

1.50

2.00

2.50

T1 T2 T3 T4 T5

Mea

n N

co

nte

nt

in t

he

Ro

ot

DM

(%

)

Treatments

27

Figure 14. Average biomass fresh yield per treatment and partitioning of the biomass between shoot and root (T1= 125kg/ha, T2=160 kg/ha, T3=207 kg/ha, T4=250kg/ha, T5= 288 kg/ha).

Laboratory Analysis on shoot and root N content indicated that, at this stage of the carrot development, the

shoot had the highest amount of N in the tissue, ranging between a minimum of 86% (T3) and a maximum of

89 % (T1) of total biomass N. While, the root tissue ranged between a minimum of 11% (T1) and a maximum

of 14% (T3) of total biomass N (Figure 15). Nitrogen partitioning between the organs had minimal fluctuation

between treatments, following the same distribution pattern of the biomass partitioning (Figure 15).

Figure 15. N content in the biomass (dry matter) and N partitioning (%) between carrot shoots and roots of the total N in the biomass, for the

different treatments. T1= 125kg/ha, T2=160 kg/ha, T3=207 kg/ha, T4=250kg/ha, T5= 288 kg/ha).

111.93(kg)

155.41(kg) 107.11

(kg)

129.10(kg)

116.42(kg)

224.34(kg)

386.04(kg)

246.89(kg)

200.23(kg)

284.59(kg)

0.00

100.00

200.00

300.00

400.00

500.00

600.00

T1 T2 T3 T4 T5

har

vest

ed b

iom

ass

(kg/

ha)

Treatments

Shoot

Root

11% 12% 14% 13% 13%

89%88%

86%87%

87%

0.000

0.050

0.100

0.150

0.200

0.250

T1 T2 T3 T4 T5

N c

on

ten

t o

f th

e b

iom

ass

(%)

Treatments

N Shoot (g)

N Root (g)

28

4. Discussion Because of the results of the statistical analysis it is not possible to draw sound conclusions on the effect of

fertilization rate at this stage of the analysis. However, the observations made on the yield quality variables

match earlier findings on effects of N rates on carrot yield parameters.

It appears that fertilization rate affected plant density at the early stage of carrot emergence in the form of a

starter effect (Costigan, 1988; Ma and Kalb, 2006; Stone, 1998). In fact, the plant density observed during the

midterm data collection follows the pattern of the emergence rate recorded at the 4th weeks after sowing

(01.12. 2016). This result is also of interest because it shows that in this time span, no relevant plant loss

occurred due to weed competition nor pest and disease outbreaks.

Although the mineralization rate of the fertilizer was not tested and only total N (3%) was considered in the

calculations of the fertilization rates, it could be expected that the fertilizer applied had a starter effect on crop

germination. Based on experience with this same brand and type of fertilizer, during previous field trials, a

turnover of three weeks was expected for N mineralization (Dr. Treadwell, Personal communication). Since

the first fertilizer application was on October 19th, 2016, and the carrots were sown on November 14th, 2016,

it was possible to assume that by the time the carrots emerged, enough N was mineralized to produce an

effect in proportion to the amount applied. Even though this calculation method for N rates leads to an

approximate general conclusion, extensive analysis on the characteristic of the fertilizer employed in the trial

were not conducted. The experiment did not aim to serve as a recommendation on the type of fertilizer to

employ in carrot production, rather on developing recommendations for the N rate to optimize production.

The lower plant density and germination rate at higher N rates (T4 and T5) matches the earlier study of Hegarty

(1976) and Stone (1998), who fined a toxic effect of N on higher emergence rate. The numbers of plantlets

emerged increase consistently until the median rate T3 (207 kg N /ha) and, subsequently, declining at the two

highest rate (Appendix 3). Hegarty (1976) reported a decline in seedling emergence at increasing rate of N

applied, where the emergence rate dropped from 70%, at a rate of 125 kg N/ ha, to 56% at a rate of 250 kg N/

ha. Also, the author indicates that the phenomenon is enhanced by soil physical characteristics, attributing

part of this effect on an increase in soil osmotic potential caused by higher presence of ions in the soil (Hegarty,

1976).

Many studies have associated a large shoot with high root yield (Boli, 1996; McKe, 1996; Suojala, 2000). The

data recorded on shoot length, crown diameter shoot size and root size matches these observations. Shoot

length and crown diameter follow the same trend, with decreasing values at increasing fertilization rates (Figure

11; Figure 12).

The results indicate T2 as the treatment where the most overall biomass was produced (shoot biomass plus

root biomass) and T3 as the treatment with the highest percentage of N in the root biomass (Figure 13; Figure

14; Figure 15). This finding point out that while there were equal amounts of harvested root biomass in T2 and

T3, N absorption was more effective in T3 with a 14% of the N in the biomass in the root (Figure 13; Figure

15).

The results on harvested biomass do not give a clear trend in correspondence to increasing N rate. However,

the patterns of yield observed in this trial are in line with what established by the UF/IFAS researchers, who

found for the same cultivar (Choctaw), in a multiyear fertilization trial with conventional fertilize, increasing

roots yield at a fertilization rate from 0 kg N /ha until 165 kg N /ha and a subsequent yield decline at the higher

29

rate of 220 kg N/ ha (Hochmuth; Brecht and Basset, 1999).

The results on nitrogen and biomass partitioning confirmed that the carrot was still in an early vegetative growth

stage, when the plant is investing in biomass and assimilate accumulation toward the shoot (Feller,1995;

Meier, 1997; Guanglong, 2016; Wien, 1997). These results are in line what was expected to be the

phenological phase of the crop at the time of the assessment (Figure 8). This finding was of interest since it

was the first time that the research team had worked with this plant, and there was a certain degree of

uncertainty on how the environmental conditions, the sowing time and the fertilization rate, may have affected

the growing period of the carrot.

However, at this stage of the crop development it cannot be concluded which fertilization rates give the best

performance in terms of yields and environmental impacts, as the effect of different N rates on yield qualities

and quantity can be assessed only with the final harvest. Moreover, to asses leaking potential form the different

the analysis of the leachate in the lysimeters will be indispensable.

5. Conclusions It is not possible to draw conclusion on BMPs form the midterm analysis, although T2 and T3 showed promising

results in terms of yield performance. At this fertilization rate the highest percentage of N in the harvested

biomass and root biomass production were found. The research team collected similar data at final harvest on

April 14, 2017, and will perform similar analysis to determine if the trends observed during the sampling carried

out in January were retained through harvest. Understanding the N demand of the plant based on its

phenological life stage will allow farmers to fine tune N application rates and the timing of N application

throughout the season to maximize the percentage of N utilized by the plant, and minimize risk to water quality

due to N leaching. To make final recommendations for BMPs for organic carrot production it will be necessary

to repeat the experiments a second year to ensure results are consistent in different conditions.

Funding for this work was provided by the Florida Department of Agriculture’s Office of Agricultural Water

Policy, the University of Florida-IFAS, and the UF-IFAS Agricultural Extension Center in Live Oak, FL.

30

6. Other activities performed as part of the internship experience. The research presented in this report is the outcome of the work I conducted during my internship at the

University of Florida, with UF/IFAS Extension research team.

My primary role during the internship was to assist Dr. Treadwell with the two filed trials for BMPs development

for fertilizer use in organically grown carrots.

It was the first time that the research team worked with this crop. Therefore, I invested a good amount of time

in researching information about the development of carrot and the current practice of organic farming for this

carrot.

In the first three weeks of internship, before the establishment of the field trial, I participated in all the field

surveying and field sampling needed to design the experiments.

Activities involved measuring the field, observing the area looking for restriction, mapping the area using the

tools available in Google Earth. Also, marking in the field repetitions, the production beds and the area for the

lysimeter installation.

After identifying and defining the experimental area, and subdividing it in the experimental units, I actively

worked in the process of the lysimeter installation, thatoccured on October 8th, 2016.

After the lysimeters installation, before the Carrots were first sown the 21st October 2016, I spend time

developing a field guide, relevant to carrot, for weeds and pest identification. Also, listing all the available

products in organic agriculture for weeds and pest management. Because of practice reason such as number

of pages and file’s dimension, I decided to attach this document separately from the report (Annex 2). During

this period, I also Implemented the LBF table for recommended fertilizer rates and researched on typical row

spacing in organic agriculture.

Part of my job was to maintain, record data and report field activity, on a shared Excel file that the whole

research team used as a source of information (Annex 1). This file is also attached separately because of its

dimensions. This Excel file contains all the relevant calculation for the N rate trial, and the Application strategy

one. I personally worked on the calculations and conversion in this file under the direction of Dr. Treadwell.

I participated in the field work for the calibration of the seeder we used to plant the carrots, and I overlooked

the second sowing event. During this activity, the research team and I would check that the machine correctly

dropped the seeds and that row spacing was indeed correct.

After the carrots were sowed, except for routine check (weekly) on the field trial for weed, soil sampling and

pest scouting, I invested time in researching on the physiological phases of the crop. With this information, I

developed a fertilization calendar for the Application strategy trial. The calendar was based on the expected N

demand by the crop (Annex 1).

Between sowing and the data collection of the midterm analysis I actively worked in the field for weeds

scouting, weeding, and fertilizer distribution in the two trials. Even dough I could collect data only for the N rate

one, an equal amount of time was invested on both the field trials (The N rate trials and the Application

strategy). All the routinely field activities were performed for both.

31

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Appendix 1 Liner bed foot (LBF) is an approach designed to increase the accuracy of fertilizer application in bedded vegetable systems by accounting for, and eliminating the area between beds in fertilizer calculations (Hochmuth and Hanlon, 2015). When vegetable producers apply fertilizer only to the bed, they save money by not applying it to areas between beds, and they also minimize N leaching when withholding fertilizer from plant-free areas. The LBF approach converts a fertilizer rate from a per acre basis to a production bed basis, based on the width of the bed. An LBF is a linear distance of 1 foot measured along a raised, mulched production bed. The total number of LBF in a planting system or bed arrangement system can be expressed as LBF per acre (LBF/acre). For simplicity, it is preferred to represent the rate per on a 100 LBF per acre basis. Different crops are placed on production beds in many spacing configurations. These spacing configurations depend on from the distance between the centers of two production beds. In this system, it is necessary to convert fertilization rate for lb a-1 to lb LBF-1. To do so the first step is to calculate LBF per acre, which can be done by dividing 43,560 ft2 (the dimension of 1 acre) by the bed spacing. Subsequently, the fertilizer rate lb per acre can be divided by LBF per acre.

Fertilizer rate lb./100 LBF= Fertilizer rate (lb./a)/((43560(ft2)/ bed spacing (ft.))/100)

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Appendix 2.

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Appendix 3.