2002/12/01 by S.J. Breschini, T.K. Hartz
Agricultural and Biological Sciences · Chemistry · #Agronomy #Animal science #Biology #Chemistry #Environmental science #Fertilizer #Growth and nutrition in plants #Irrigation Practices and Water Management #Leaching (pedology) #Nitrate #Nitrogen #Plant nutrient uptake and metabolism #Soil science #Soil water
paper · pdf · doi:10.21273/hortsci.37.7.1061
openalex publication_date 2002/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25
Trials were conducted in 15 commercial fields in the central coast region of California in 1999 and 2000 to evaluate the use of presidedress soil nitrate testing (PSNT) to determine sidedress N requirements for production of iceberg and romaine lettuce ( Lactuca sativa L.). In each field a large plot (0.2-1.2 ha) was established in which sidedress N application was based on presidedress soil NO 3 -N concentration. Prior to each sidedress N application scheduled by the cooperating growers, a composite soil sample (top 30 cm) was collected and analyzed for NO 3 -N. No fertilizer was applied in the PSNT plot at that sidedressing if NO 3 -N was >20 mg·kg -1 ; if NO 3 -N was lower than that threshold, only enough N was applied to increase soil available N to ≈20 mg·kg -1 . The productivity and N status of PSNT plots were compared to adjacent plots receiving the growers' standard N fertilization. Cooperating growers applied a seasonal average of 257 kg·ha -1 N, including one to three sidedressings containing 194 kg·ha -1 N. Sidedressing based on PSNT decreased total seasonal and sidedress N application by an average of 43% and 57%, respectively. The majority of the N savings achieved with PSNT occurred at the first sidedressing. There was no significant difference between PSNT and grower N management across fields in lettuce yield or postharvest quality, and only small differences in crop N uptake. At harvest, PSNT plots had on average 8 mg·kg -1 lower residual NO 3 -N in the top 90 cm of soil than the grower fertilization rate plots, indicating a substantial reduction in subsequent NO 3 -N leaching hazard. We conclude that PSNT is a reliable management tool that can substantially reduce unnecessary N fertilization in lettuce production.