Variable Rate Fertilizer Application for Desert Vegetable Production

Fields used for vegetable production in the southwestern United States often require large amounts of P fertilizer for optimal production and quality.  The field production units (many alluvial) in this region are typically highly variable in soil physical and chemical properties.  However, the prospects of variable rate (VR) P fertilization practices had not been evaluated for vegetable crops in this region. Studies were conducted in commercial production fields with grower–cooperators in 2013–2015 with lettuce (Lactuca sativa L), broccoli (Brassica oleracae Italica Group), and potato (Solanum tuberosumL.). In these evaluation we compared grid sampling based VR fertilizer recommendations and zone sampling based VR fertilizer recommendations to the grower standard fertilizer practice, which was usually based on composited soil sampling. This presentation will include a detailed description of commercial-grade application equipment upgraded with specialized hardware and software used for VR applications of pre-plant phosphorous fertilizer, the scientific framework used to convert soil P levels into prescribed fertilizer amounts, and hardware and software for the collection of production data. Preliminary data collected show potential economic and environmental benefits to VR P fertilizer management for vegetables produced in the desert.