Phosphorus fertilizer management strategies for variable rate fertilizer applications in center pivot irrigated potato rotations

摘要

To adapt variable rate fertilizer application technology in the Pacific Northwest for preplant fertilizer applications in irrigated potato (Solanum tuberosum L.) systems, fields are grid soil sampled (0.5-1.5 ha basis) and preplant P fertilizer applications are made based on soil test P values. These large, center pivot irrigated systems can have a high degree of variability of factors affecting P availability. To evaluate the efficacy of using soil test P values alone versus using several soil test factors for crop response to P fertilizer, a potato field was grid soil sampled and the samples analyzed for soil pH, and extractable P, Ca, and Fe. The field had a distinct east-west split between slightly acid and slightly alkaline soil pH. Uniform rate strips of P fertilizer (29, 120, and 169 kg P ha~-1) were applied across a 65 m width, then the rest of the field was variable rate fertilized based on soil test P. Replicated areas in the strips were established in two areas of like soil test P andeither low or high soil pH and monitored during the season for petiole P content then evaluated for crop yield and quality. The remainder of the field was yield monitored. Preliminary results indicate that soil pH may provide a better indicator of P fertilizer response than soil test P.