Long-Term Residual Effects of Potassium to Cotton on Soil Potassium Supply and Corn Productivity Under No-Tillage.

The long-term residual effects of potassium (K) applications to preceding cotton (Gossypium hirsutum L.) on subsequent corn (Zea mays L.) is largely unknown under no-tillage. A cotton field experiment was conducted on a no-tilled Loring silt loam at Jackson, TN during 1995-2008 with the K treatments of 0, 28, 56, 84, 112, 140, and 168 kg ha^-1applied to the same plots each year. From 2009 through 2011, corn was no-till planted on the previous cotton trial without further K fertilization. Incremental gains in corn leaf K responses were consistent during early to mid-season with increases in the K application rate for previous cotton. A significant quadratic relationship was observed between corn yields and K application rates in 2010 and 2011 with corn yield peaking at the K application rate of 94 kg ha^-1 in 2010 and 84 kg ha^-1 in 2011. Potassium removal by grain ranged from 2.54 to 3.55 with an average of 3.10 kg K per Mg of grain at the 155 g kg^-1 moisture level. For the 28 kg K ha^-1 rate and those higher K rates, soil K buffering capacity followed an exponential decline as the initial soil test K level increased. Surface broadcasting of K fertilizer at the recommended rate of 56 kg K ha^-1 or above to preceding cotton for 14 years and relying on the residual K fertilizer for the subsequent corn for at least three years without further K fertilization might be a viable K management practice on high K fields under no-tillage.