Tillage and Phosphorus Management Effects on Crop Production in Soils with Phosphorus Stratification

Reduced‐ and no‐tillage seedbed preparation methods coupled with broadcast P applications lead to an accumulation of available P in the surface 0‐ to 5‐cm soil layer and a depletion of available P deeper in the profile. A 3‐yr study determined the effects of tillage and fertilizer P management on P uptake and grain yield for P‐stratified soils. Tillage practices were moldboard plow (once at the start of the study followed by reduced tillage), reduced tillage (disk followed by field cultivation), and no‐tillage. Four P management methods were imposed: (i) no P; (ii) 20 kg P ha −1 applied as a surface broadcast; (iii) 20 kg ha −1 applied as a banded starter, 5 cm to the side and 5 cm below the seed; or (iv) 20 kg ha −1 applied in a deep placed band, 13 to 15 cm on 0.7‐m centers. The one‐time moldboard plowing produced higher early season dry matter yields for corn ( Zea mays L.), wheat ( Triticum aestivum L.), and soybean [ Glycine max (L.) Merr.] compared with the no‐tillage system, but tillage effects on final grain yield were inconsistent. Subsurface placement of P generally increased P uptake and grain yield of corn and sorghum [ Sorghum bicolor (L.) Moench], but had little effect on grain yield of soybean. Results indicate that subsurface applications of P fertilizers should be considered if soil test P is highly stratified within the surface 0‐ to 15‐cm layer and the 15‐cm composite is medium or below for available P.