M. Van Noordwijk, Widianto, M. Heinen, Kurniatun Hairiah
Under high rainfall conditions on acid soils with shallow crop root systems the rate of N leaching is high. A simple model predicts nitrogen uptake efficiency as a function of the amount of rainfall in excess of evapotranspiration, rooting depth and degree to which N leaching is retarded in comparison with water transport. Field observations on acid soils in S.E. Nigeria and S. Sumatera (Indonesia) showed that this model should be amended to include the role of old tree root channels. Crop roots can follow these channels, which are coated with partly decayed organic matter, into the acid subsoil. Measurements of water infiltration with a Guelph permeameter and a methylene blue dye showed that such channels form the major infiltration sites during rainstorms. Implications for nitrogen use efficiency and cropping pattern are discussed. © 1991 Kluwer Academic Publishers.
Institute for Soil Fertility Research, Haren, 9750 RA, P.O. Box 30003, Netherlands; Soil Science Department, Faculty of Agriculture, Brawijaya University, Malang, 65145, Indonesia
