Strategies for Managing Nitrogen in Strawberry Michael Cahn Irrigation and Water Resources Advisor UC Cooperative Extension, Monterey County
Acknowledgements: Tim Hartz, UC Davis Tom Bottoms, Dellavalle Laboratory Mark Bolda, UCCE Santa Cruz Andre Biscaro, UCCE Ventura Oleg Daugovish, UCCE Ventura Surendra Dara, UCCE San Luis Obispo Mark Gaskell, UCCE San Luis Obispo Emily Gardner, Driscolls
Nitrogen Use Reporting
Developing a Nitrogen Fertilization Plan For Strawberry 1. Crop N demand: Estimate crop nitrogen requirement 2. Nitrogen supply: Residual mineral N (nitrate and ammonium in soil) Potential soil mineralization (organic matter, residue, amendments) Irrigation water Fertilizer 3. Tools to guide fertilizer scheduling: Soil sample Tissue analysis Suction lysimeter
Seasonal Nitrogen Fertilizer Applied in Strawberry (Salinas/Watsonville 2017) Observation: Marketable fruit yield is not correlated with seasonal applied N fertilizer Marketable Fruit Yield (lbs/acre) 120000 100000 80000 60000 40000 20000 50 100 150 200 250 300 350 Seasonal applied N fertilizer (lbs N/acre) Fields can have high yields with low rates of N fertilizer Applied N can be much lower than the amount of N that the crop takes up
Seasonal Nitrogen Fertilizer Applied in Strawberry (Salinas/Watsonville 2017) Applied N (lbs N/acre) 350 300 250 200 150 100 50 Preplant Fertigated 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Field Fertilizer programs are often similar among fields within the same grower operation Reliance on preplant fertilizer
1000 lbs of fruit take up about 2 lbs of N per acre 250 Fruit N uptake lbs N/acre 200 150 100 50 N uptake = 2 x fruit yield/1000-1.65 R 2 = 0.95 0 0 20000 40000 60000 80000 Fruit Yield (lbs/acre)
About Half of the Crop Nitrogen is in the Fruit 350 Crop N uptake (lbs N/acre) 300 250 200 150 100 50 vegetation N fruit N 0 1 2 3 4 5 6 7 8 9 10 11 Field Number
Crop N needs can be estimated from fruit yield Crop N uptake (vegetation + fruit) lbs/acre 400 300 200 100 0 N uptake = 20.3 + 3.3 x fruit yield/1000 R 2 = 0.93 0 20000 40000 60000 80000 Fruit Yield (lbs/acre)
Crop Nitrogen Uptake Pattern in Strawberry Crop N uptake (lbs N/acre) 200 150 100 50 N uptake = 1 to 1.5 lbs N/acre/day 0 100 150 200 250 Days after Planting
Previous Crop Residues Potentially mineralize 30 to 60 lbs N/acre
Organic Amendments
Soil Nitrogen Mineralization Estimated N Soil % Organic Matter mineralization (lbs N/acre/day) Placentia sandy loam 0.9 0.5 Chualar loam 1.2 0.7 Cropley silty clay 1.3 0.9 Metz fine sandy loam 1.4 0.6 Mocho silty clay loam 2.0 1.0
Nitrogen available in irrigation water Well water (2 to 70 ppm Nitrate-N) Recycled water (15 to 30 ppm N as Ammonium + Nitrate)
Calculating N applied from irrigation water: Applied water (inches) x NO 3 -N conc. (ppm) x 0.227 = lbs N/acre Example: Applied water = 1.1 inch per week Nitrate-N concentration = 20 ppm 1.1 inches/week x 20 ppm NO 3 -N x 0.227 = 5.0 lbs N/acre/week
Soil Nitrate Quick Test Sample 0 1 foot zone just outside of plant row Angle probe slightly towards the center of bed Composite soil from > 10 locations
What is a sufficient soil nitrate-n concentration for strawberry? Crop N uptake (lbs N/acre) 200 150 100 50 30 lb N/acre/month 10 to 15 ppm Nitrate-N adequate in early season (40 to 60 lbs N/acre) Many productive fields have soil nitrate levels < 10 ppm N during the main fruiting period Soil NO 3 -N (ppm) 0 30 25 20 15 10 5 0 Jan 01 Mar 02 May 01 Jun 30 Aug 29 Soil N threshold
Irrigation management affects soil nitrate levels (2016 Watsonville Trial) Treatment Applied Water Seasonal N fertilizer Average soil nitrate Marketable Yield inches lbs N/acre ppm N lbs fruit/acre 70% Crop ET 18 240 28 80159 A* 100% Crop ET 26 240 15 83910 A B 130% Crop ET 32 240 14 92000 B Grower Standard 36 266 3 81956 A * Treatments with similar letters are not statistically different at the 95% confidence level.
} DRIS leaf optimum ranges early flowering peak harvest Values from high yielding, nutritionally balanced fields Composite of 30 recently mature leaves Bottoms et al. 2013 1 2 3 4 5 Crop Stage
CropManage: Online irrigation and nitrogen management decision support tool v3.cropmanage.ucanr.edu
How useful are suction lysimeters for monitoring crop N status? Highly variable concentrations of nitrate in leachate Concentration is affected by irrigation (leaching fraction)
Is preplant fertilizer necessary?
How effectively is preplant CRF being used? Most common product is 18-8-13, 6-8 month release Documenting N release rate from CRF: CRF bags buried in two strawberry fields in mid-november 3 bags recovered from each field each month, and analyzed for the amount of N remaining in the prills (Hartz and Bottoms 2011)
N release was nearly linear over time : When CRF was applied in November, 70-80% N release by April 1
Controlled Release Fertilizer Trial (Crop N uptake by the end of April)
Nitrate leaching usually occurs during the winter
Salt burn due to proximity roots to preplant fertilizer band Photo: S. Koike
Summary Strawberry N uptake is 20 to 30 lbs N/acre during the winter and about 1 to 1.5 lbs N/acre/day after March Other sources of N (residual soil N, soil mineralization, irrigation water) may supply much of the N needs of a strawberry crop besides fertilizer A combination of soil and whole leaf sampling can help with decision making on N rates Irrigation needs to be optimized