Management and Dynamics of Potassium in a Humid Tropical Ultisol under a Rice-Cowpea Rotation

Little is known about the role of K fertilization, stover management, and tillage methods on soil K availability as they affect rice (Oryza sativa L.) and cowpea [Vigna unguiculata (L.) Walp.] productivity on Utisols of the humid tropics. The effects of five K rates (0-120 kg k ha −1 ), returning or removing stover, and three tillage methods (notill, strip, and conventional) were evaluated during 12 crops of rice and cowpea grown for a 4-yr period. Fertilizer K was applied to the first seven crops. The site was a recently cleared, 18-yr-old secondary forest in the Peruvian Amazon Basin. The soil was a fine-loamy, siliceous, isohyperthermic Typic Paleudult (...)