Potassium placement and tillage system effects on corn response following long-term no till
2001
Stratification of immobile nutrients in long term no-till (NT) fields may reduce corn (Zea mays L.) yield potential. Five field studies were conducted from 1995 to 1998 to evaluate corn response to different K placements and rates when fields with a NT cropping history were either fall zone-tilled (ZT), fall moldboard-plowed [conventional tillage (CT)], or continued in the NT system. The silt loam to silty clay loam soils had medium or high soil-test K (0-15 cm) ratings with varying degrees of K stratification to the 30-cm depth. Fall-applied K at rates of 0, 42 and 84 kg ha(-1) was surface-broadcast in the NT system, deep-banded to 15-cm depth in the ZT system, and surface-broadcast and incorporated in the CT system. Potassium was also shallow-banded with the planter at rates of either 0 to 8 kg ha(-1) (low) or 42 to 50 kg ha(-1) (high). Average concentrations of corn ear-leaf K near silking increased from 10.9 g kg(-1) with no K to 15.2 g kg(-1) with highest fall plus spring K rates on the three sites with soil-test K levels of <100 mg kg(-1). For these same sites, ear-leaf K concentrations averaged 1.2 g kg(-1) higher in CT compared with NT or ZT. On four of the five field sites, corn yields in the NT and ZT systems were maximized by applying the high rate of starter K, even when no K fertilizer was applied the previous fall. On long-term NT soils with medium soil-test K, corn producers may derive most K fertility benefit from shallow banding at planting.
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