ABSTRACT
Field studies were conducted to evaluate cotton response to the deep placement of K fertilizer and agricultural limestone on Alabama soils. Studies were initiated in 1989 on a Dewey silt loam and a Norfolk silt loam, and in 1990 on a Lucedale sandy clay loam. Deep placement treatments were achieved using a dry fertilizer applicator that applies fertilizer at depths of 6 to 15 inches deep behind a subsoiler shank. Potassium was applied deep at rates ranging from 0 to 90 lbs K2O ac-1. Tests on the Dewey and Lucedale soils included an additional deep placement treatment that received 120 lbs K2O ac-1. Additional treatments received K applied as surface broadcast applications at rates ranging from 0 to 90 lbs K2O ac-1 with and without subsoiling. Two additional treatments received 1500 lbs agricultural limestone ac-1 and 1500 lbs limestone + 90 lbs K2O ac-1, respectively. There were no consistent yield responses to the deep placement treatments. Except for the Dewey soil in 1990, treatments receiving deep placement of limestone produced the same seed cotton yields as the subsoiled check treatment. In 1990, the treatment receiving 1500 lbs limestone ac-1, deep placed, resulted in lower yields as compared to the subsoiled check treatment. A yield response to the deep placement of K was obtained in 1990 on the Lucedale soil, but a greater yield response was obtained by applying the same rates of K as a surface broadcast application. Initial results from this series of field studies suggest that for cotton, the deep placement of K fertilizer is not superior to surface broadcast applications of K fertilizer on Alabama soils.
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