Download or read book Nitrogen Management and Water Quality Protection in California Lettuce and Strawberry Production written by Thomas Glenn Bottoms and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Intensive production of horticultural crops in the Salinas Valley of California has contributed to NO3-N pollution of surface water and groundwater in this region; NO3-N in excess of the 10 mg L−1 Federal drinking water standard is common. Nitrogen dynamics in lettuce and strawberry production were studied using both commercial field surveys and replicated fertilization trials, with the objective of identifying production practices that protect environmental water quality. Additionally, wood-chip denitrification bioreactors were evaluated as a method of removing NO3-N from surface runoff and tile drain effluent from horticultural fields. In lettuce production the use of presidedress soil nitrate testing to guide in-season N fertilization was evaluated. Delaying N application when root zone soil NO3-N was > 20 mg kg−1 was found to be a safe and effective practice that maintained peak crop productivity while minimizing environmental N loading. While leaf N and midrib NO3-N monitoring may indicate the adequacy of N fertility, those plant-based measures were not correlated with concurrently measured soil NO3-N and therefore were of minimal use in identifying fields in which N fertilization could be postponed. Strawberry crop N uptake showed a consistent pattern across fields, with limited uptake from fall transplanting through March, followed by a consistent uptake of approximately 1.1 kg ha−1 d−1 N through the rest of the production season. Mean seasonal N uptake was estimated at 220 kg ha−1. Monitoring of strawberry fields revealed a wide range of seasonal N fertilization rates and irrigation volumes, but neither N rate nor irrigation volume was correlated with seasonal fruit yield. The potential for NO3-N leaching from the root zone was higher over the winter than during the main irrigation season (May-September). Preplant application of >100 kg ha−1 N in the form of controlled release fertilizer, a common grower practice, was shown to be highly inefficient. Strawberry leaf nutrient optimum levels were reevaluated using the Diagnosis and Recommendation Integrated System (DRIS) approach. The DRIS optimum leaf N concentration range was lower than existing sufficiency standards. Wood-chip denitrification bioreactors consistently removed NO3-N from surface runoff and tile drain effluent. Denitrification rates achieved ranged from approximately 5-11 mg L−1 N removal per day of residence time in the bioreactor, depending on water temperature. Both management practice modifications to limit N loading, and some method of wastewater remediation, will undoubtedly be required to approach a 10 mg L−1 NO3-N environmental water quality standard.