Phosphate Placement for Corn in Chisel and Moldboard Plowing Systems1

Abstract Field experiments conducted at three locations in Nebraska and one in Illinois compared tillage by chisel and moldboard plowing for corn (Zea mays L.). Specific objectives were to compare the two tillage systems in respect to growth characteristics and final yield of corn, to ascertain the most effective method of applying fertilizer P with chisel plowing, and to determine residual P distribution in the rooting zone after 3 years with the various systems employed. Fertilizer P was applied at three or four rates as orthophosphoric acid in conjunction with varied tillage and placement as follows: 1) surface broadcasting of P and incorporation by chisel plow tillage, 2) P application by chisel plow at 18 to 20‐cm depth, 3) chisel plow tillage with P banded beside the row at planting, and 4) moldboard plow tillage following surface broadcasting of P. Primary tillage was accomplished in the fall after corn harvest. Somewhat higher yields were obtained with moldboard plowing than with chisel plowing, irrespective of P rate or placement. This benefit for the moldboard plow is offset by the moisture conservation and erosion control advantages afforded by the chisel. Broadcast P prior to chiselling and deep placement of P with the chisel gave comparable yields, although deep placement afforded greater season‐long crop feeding on the fertilizer. Runoff loss of P on sediment was minimized with chisel placement of the P.