Peanut, corn, and cotton critical levels for phosphorus and potassium on goldsboro soil

Abstract

Fertilizer applications of phosphorus (P) and potassium (K) are most economic if based upon local soil test information. The objective of this study was to determine the soil test (Mehlich 3-extractable) and plant tissue critical levels of P and K for corn (Zea mays L.), peanut (Arachis hypogaea L.), and cotton (Gossypium hirsutum L.) grown on a Goldsboro (fine-loamy, siliceous, subactive, thermic Aquic Paleudult) sandy loam for 17 years. Four soil test levels of P were created and maintained by applying triple superphosphate at about 6-year intervals in a factorial design, with three rates of K applied annually prior to planting crops other than peanut. Soil and tissue samples were taken in midseason, and yield and grade determined at harvest. Yields from the first two years and one drought year were not included. Critical levels were determined by a linear response and plateau method on data restricted to that portion of the crop being grown at a sufficient level of the other nutrient. The Mehlich 3 P critical levels (mg dm−3) were 22 for corn, 21 for peanut, and 16 for cotton, whereas the plant tissue critical levels for these three crops were 0.23, 0.26, and 0.21%, respectively. It was calculated that an annual application of 37 kg P2O5 ha−1 (33 lb acre−1) would maintain the Mehlich 3 P level at 33 mg dm−3, a practical maximum for the recommendation of P fertilizer, on this soil. The Mehlich 3 K critical levels (cmol dm−3) were 0.08 for corn, 0.10 for peanut, and 0.10 for cotton on this soil which has a low cation exchange capacity, whereas the plant tissue critical levels for these crops were 1.0, 1.6, and 0.9%, respectively. Cotton required a greater application of K than corn.