Assessing nitrogen uptake and the impact of fertilizer amounts and sources on strawberry production in California

Abstract

A study was conducted in Oxnard, CA, from 2014 to 2015 to assess seasonal nitrogen (N) uptake, and 2018-2019 to assess the effect of fertilizer rates and types (calcium nitrate [CN9] and ammonium nitrate [AN20]) on yield of two strawberry (Fragaria × ananassa Duch.) cultivars (Fronteras and a proprietary cultivar). The 2014-2015 study identified mainly two seasonal uptake rates: 0.59 and 1.30 kg ha -1 d -1 for early (October-February) and late season (March-June), respectively. The N fertilizer rates for the 2018-2019 study, derived from the 2014-2015 study, were defined as low (CN9-L and AN20-L; 132 kg ha -1 total applied), optimum (CN9-O and AN20-O; 233 kg ha -1 total applied), and high (CN9-H and AN20-H; 334 kg ha -1 total applied). Marketable yield for Fronteras plateaued at the optimum fertilizer rate, suggesting the average rate determined from the 2014-2015 study (equivalent to the optimum rate in the 2018-2019 study) achieved the highest yield for that cultivar.Marketable yield of the AN20 treatments for the proprietary cultivar was significantly greater than the CN9 treatments. Increasing N fertilizer rates resulted in greater aboveground vegetative biomass and consequent increased yield for both cultivars.The AN20 treatments resulted in 193-264% less nitrate found in the 30.5-to-61.0-cm depth of soil than the CN9 treatments at crop termination, indicating significantly less nitrate-leaching potential for fertilizers with greater proportion of N as ammonium. Assessing N uptake and tailoring fertilizer amounts and sources accordingly can maximize strawberry yield and minimize nitrate leaching. INTRODUCTIONAmong all essential plant nutrients, nitrogen (N) is the most yield-limiting nutrient for strawberry (Fragaria × ananassa Duch.