Tomato Responses to Preplant-incorporated or Fertigated Phosphorus on Soils Varying in Mehlich-1 Extractable Phosphorus

Abstract

Experiments were conducted to evaluate the yield response of tomato (Lycopersicon esculentum Mill.) to P, either preplant-incorporated or injected through the drip irrigation system, on soils with low, high, or very high soil P content. Fertilization through the drip irrigation system (fertigation) was more efficient than preplant incorporation of P for soil that tested low in P (9 mg·kg–1 Mehlich-1 P). On soil testing low in P, marketable yield response to preplant soil P application rates (0 to 100 kg·ha–1) was maximum at 61 kg·ha–1 P according to the linear-plateau model, but 37 kg·ha–1 P according to the quadratic-plateau model. The lower value is about one-half the P recommended by Univ. of Florida for low-P soils. On soil testing high in P (48 mg·kg–1 Mehlich-1 P) the linear-plateau model predicted a maximum yield of 72.8 t·ha–1 with 25 kg·ha–1 P. The Univ. of Florida recommended no P for that soil. On soil testing very high in P (85 mg·kg–1 Mehlich-1 P), there was no yield improvement with P fertilization.