Strategies for Managing Nitrogen in Strawberry. Michael Cahn Irrigation and Water Resources Advisor UC Cooperative Extension, Monterey County

Transcription

1 Strategies for Managing Nitrogen in Strawberry Michael Cahn Irrigation and Water Resources Advisor UC Cooperative Extension, Monterey County

2 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

3 Nitrogen Use Reporting

4 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

5 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) 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

6 Seasonal Nitrogen Fertilizer Applied in Strawberry (Salinas/Watsonville 2017) Applied N (lbs N/acre) Preplant Fertigated Field Fertilizer programs are often similar among fields within the same grower operation Reliance on preplant fertilizer

7 1000 lbs of fruit take up about 2 lbs of N per acre 250 Fruit N uptake lbs N/acre N uptake = 2 x fruit yield/ R 2 = Fruit Yield (lbs/acre)

8 About Half of the Crop Nitrogen is in the Fruit 350 Crop N uptake (lbs N/acre) vegetation N fruit N Field Number

9 Crop N needs can be estimated from fruit yield Crop N uptake (vegetation + fruit) lbs/acre N uptake = x fruit yield/1000 R 2 = Fruit Yield (lbs/acre)

10 Crop Nitrogen Uptake Pattern in Strawberry Crop N uptake (lbs N/acre) N uptake = 1 to 1.5 lbs N/acre/day Days after Planting

11 Previous Crop Residues Potentially mineralize 30 to 60 lbs N/acre

12 Organic Amendments

13 Soil Nitrogen Mineralization Estimated N Soil % Organic Matter mineralization (lbs N/acre/day) Placentia sandy loam Chualar loam Cropley silty clay Metz fine sandy loam Mocho silty clay loam

14 Nitrogen available in irrigation water Well water (2 to 70 ppm Nitrate-N) Recycled water (15 to 30 ppm N as Ammonium + Nitrate)

15 Calculating N applied from irrigation water: Applied water (inches) x NO 3 -N conc. (ppm) x = 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 = 5.0 lbs N/acre/week

16 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

17 What is a sufficient soil nitrate-n concentration for strawberry? Crop N uptake (lbs N/acre) 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) Jan 01 Mar 02 May 01 Jun 30 Aug 29 Soil N threshold

18 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 A* 100% Crop ET A B 130% Crop ET B Grower Standard A * Treatments with similar letters are not statistically different at the 95% confidence level.

19 } DRIS leaf optimum ranges early flowering peak harvest Values from high yielding, nutritionally balanced fields Composite of 30 recently mature leaves Bottoms et al Crop Stage

20 CropManage: Online irrigation and nitrogen management decision support tool v3.cropmanage.ucanr.edu

21 How useful are suction lysimeters for monitoring crop N status? Highly variable concentrations of nitrate in leachate Concentration is affected by irrigation (leaching fraction)

22 Is preplant fertilizer necessary?

23 How effectively is preplant CRF being used? Most common product is , 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)

24 N release was nearly linear over time : When CRF was applied in November, 70-80% N release by April 1

25 Controlled Release Fertilizer Trial (Crop N uptake by the end of April)

26 Nitrate leaching usually occurs during the winter

27 Salt burn due to proximity roots to preplant fertilizer band Photo: S. Koike

28 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