Lincoln Zotarelli Horticultural Sciences Department University of Florida Apopka, October 12, 2011

What do we want from our vegetable systems in Florida? Vegetable System higher production and profits Lower environmental impact -nutrient losses -runoff -pesticides -ground water contamination Lower inputs -fertilizer -irrigation -pesticides -costs Soil and water quality -high soil organic matter -Better crop system -Crop rotation -CEC Efficient control of -diseases -nematodes -insects Climate -management of risk -decision support systems

Vegetable & Citrus Irrigation in Florida Average of total of 207,700 acres planted with vegetable crops and 739,500 acres with citrus in Florida between 1998 and 2006 (NASS/USDA, 2008)

Upper Floridian Aquifer Water Levels

Water Use Permits in the Southwest Florida Water Management District

Water Conservation Harold A. Wilkening III, Director (Jun 9, 2009)

Effect of soil texture and soil tension on soil water availability Kramer and Boyer (1995)

Actual soil moisture on sandy soils Saturation Field Capacity Wilting Point VWC > 30% VWC > 0.3 m 3 /m 3 -1 cbar MPa VWC approx. 12% VWC > 0.12 m 3 /m cbar MPa VWC approx. 6% VWC > 0.06 m 3 /m cbar -1.5 MPa

Irrigation and nutrient management “an example"

Water management and zucchini production "an example of interaction between water and fertilizer"  Two irrigation strategies Fixed irrigation – 2 hours continuously Equivalent to 79.6 gal/100ft/day At the end of the season applied 16.2 in or 5,970 gal/100ft Controlled irrigation – TARGET WAS TO WET THE TOP 12-16” OF SOIL 5 possible irrigation windows controlled by soil moisture sensors set at soil field capacity Equivalent to 33.2 gal/100ft/day At the end of the season applied 6.7in or 2,492 gal/100ft  N-rates of 75, 150 and 225 lb/ac weekly fertigation with calcium nitrate Source: Zotarelli et al Scientia Horticulturae

150 lbN/ac75 lbN/ac 225 lbN/ac Controlled irrigation 2h fixed irrigation Controlled irrigation

75 lbN/ac225 lbN/ac Controlled irrigation 75 lbN/ac 2h fixed irrigation

150 lbN/ac Controlled irrigation 75 lbN/ac 2h fixed irrigation 150 lbN/ac 2h fixed irrigation 75 lbN/ac Controlled irrigation

Zucchini plant N accumulation

Zucchini daily N uptake

Irrigation vs. N-fertilization on zucchini 75 lbN/ac150 lbN/ac225 lbN/acAverage Zucchini marketable yield (lb/ac) Controlled irrigation – up to 5 irrig. windows/day 22,38925,42226,13524,649 A Fixed irrigation of 2h/day 15,52519,53519,89118,316 B Average19,955 B22,478 A23,013 A 84%100%102% 100% 74%

24 hrs3 days7 days Effect of irrigation on solute displacement (injecting dye in fertigation lines) soil sensor based irrigation fixed time irrigation schedule 16in +38 in

Fertilization strategies for potatoes  It’s critical to understand: 1) nutrient status in the soil 2) nutrient requirement of the crop (when, where, how much…) A soil probe is used to sample fields. (Tom Schultz)

1) Nutrient status in the soil how much can soil offer?  Fact: soil must have good fertility status to produce good yields and quality. Step 1) Soil sampling – soil fertility test - composite sample from representative areas - sampling areas delineated by soil types, topography, cropping history, etc. - Great tool available: USDA – Web Soil Survey

USDA – WEB SOIL SURVEY - Main page

Identify and view soil map units of a production area

Web Soil Survey provides: 1.Soil map of a area of interest understanding the soil properties and limitation 2. Acreage and linear measurement to be used for: A. More precise fertilizer calculation rate B. chemical calculation rate C. required info for fumigation documentation e.g. exact location of the area (coordinates) 3. Better yield estimation

Fertilization strategies for potato  Excellent indicator of soil chemical status  Adjustment of soil pH if necessary  Nutrient most affected by pH are P and Mn P most available (pH ) Mn low availability above pH 6.5 Mn toxicity below near pH 5.0  higher soil pH levels are more conducive to scab, a potato disease caused by a soil-borne pathogen. If your soil has a higher pH, chose a scab-resistant variety.

Potato characteristics  Amount of N provided to potato crop can control the balance between vegetative and reproductive growth.  Nutrient requirement different at different crop stages  Sprout development about 30 DAP  0-30 DAP – no root – nutrition from seed piece  Vegetative stage – days after sprout development  Tuber initiation – requires N for growth, soil moisture, temperature  Excess N prior tuber initiation may promote excess vegetative growth and delay initiation and bulking of tuber  Tuber bulking – DAP – linear increase in dry matter

Source: Alva et al Journal of Plant Nutrition. Potato biomass accumulation

Source: Alva et al Journal of Plant Nutrition. Potato biomass accumulation Nutrition from seed piece Tuber initiation no roots Tuber bulking Linear growth Tuber are the predominant sink of N (translocation of N from vines to tubers) Vines are the predominant sink of N

2) Nutrient requirement of the crop: Source: Rosen, 2001 Table. Uptake of soil nutrients by potato vines and tubers as a function of yield. NutrientTuber yield, cwt/A Vines Nutrient uptake lb/A Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulfur (S)— Zinc (Zn) Manganese (Mn) Iron (Fe) Copper (Cu) Boron (B)

Application of fertilizer according to soil testing for potato in FL: Source: Florida Vegetable Handbook

Potato fertilization strategies  Pre-plant application of fertilizer – is it a good idea?

F P 01/07 02/8-19 3/ in

F F P 01/07 02/8-19 3/ / in 1.4 in /8

F F F P 01/07 02/8-19 3/ / in 1.4 in 0.02 in /8

F F F P 01/07 02/8-19 3/ / in 1.4 in 5.1 in /8 Harvest 0.02 in

Potato fertilization strategies  Pre-plant application of fertilizer – is it a good idea?  During planting or emergence?  Side-dress?  Banded or broadcast???

In season plant nutrient status monitoring

2007 Processing tomato monitoring, early fruit set most petiole NO 3 -N is already stored in plant cells, and therefore the concentration is dependent on the rate at which the plant converts it to organic N forms Hartz et al Hortscience Limitations of petiole testing

Seepage Relies on upward flux of water from a shallow water table to provide moisture to the plant root zone

Seepage management Commonly uses visual observation and/or hand- feel method to assess the soil moisture Rule of thumb: high water table to avoidrisk of plant water stress ???

Seepage management Water table that is kept higher than necessary may cause nutrient leaching Fertilizer application: High soil moisture rapidly dissolves the fertilizer particles and diffuses them slowly into the root zone. concentrated fertilizer Moves slowly to the shallow water table because of it has higher density than the free water Fertilizer

Ideal Seepage Management Benefits: With more efficient water use the fertilizer is retained in the root zone Reduced irrigation water application Soil storage capacity for rainfall would increase Potential reduction in nutrient leaching water table depth that maintains optimum soil moisture in the root zone while minimizing nutrient leaching

Ideal Seepage Management requires NUTRIENT MANAGEMENT Timing and fertilizer rate are important factors to increase nutrient use efficiency E.g. Pre-plant fertilization increases the risk of fertilizer leaching and reduces fertilizer use efficiency by the plant

Overhead irrigation Easier control of water application compared to seepage Fertigation More effective on nutrient losses IF WELL MANAGED

Irrigation Requirement I = irrigation ETc = crop evapotranspiration P = precipitation All terms are expressed as inches of water.

ET provides reference measure of water use based on plant water demand Scalable for specific crop, growth stage, climate, and season of year ET c = ET o * K c Crop Evapotranspiration

Potato Kc

FAWN stations

ET 0 hourly

Final consideration:  Establishment of integrated fertilizer and irrigation program  Remember: Low water and nutrient retention of Florida soils  Soil pH  Combination of fertilizer rate / placement and timing are key for success