Phosphorus and Potassium Distribution in Soil Following Long-Term Deep-Band Fertilization in Different Tillage Systems

Mallarino, Antonio P.; Borges, Rogério

Phosphorus and Potassium Distribution in Soil Following Long-Term Deep-Band Fertilization in Different Tillage Systems

2006

Mallarino, Antonio P. | Borges, Rogério

Tillage and fertilizer placement affect soil-test P (STP) and K (STK) distribution in topsoil but little is known about stratification after deep banding. This study investigated lateral and vertical STP and STK stratification after deep-banding fertilizers for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] managed with no-till or chisel-disk tillage. Soil samples were collected from selected plots of 10 Iowa trials (five for P and five for K) having 4-yr treatment histories. Treatments sampled (three replications of each) were no-till and chisel-disk tillage with or without deep-band fertilization. Either 28 kg P ha⁻¹yr⁻¹ or 66 kg K ha⁻¹yr⁻¹ was banded 13 to 18 cm deep and spaced 76 cm. Crop rows were planted on top of the fertilizer bands. Soil samples were collected at 5-cm increments to a 30-cm depth from band/row (BR) and interband/interrow (IBR) positions. Vertical nutrient stratification was observed for all treatments but was more evident for BR with no-till. Lateral stratification was not observed in nonfertilized plots. At a 5-cm depth, both nutrients were higher for BR than for IBR only with no-till management. At a 5- to 15-cm depth both nutrients were higher for BR than for IBR with both tillage systems, but at deeper depths lateral stratification was less evident across nutrients and sites. Vertical and lateral stratification were more pronounced for STP than for STK. Higher crop K uptake and recycling than for P could explain this difference. The results indicate that vertical and lateral stratification due to deep-band fertilization is of concern when planning soil sampling for no-till and may also be of concern for chisel-disk tillage.

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