Soil erosion effects on productivity of a humic nitisol

Abstract

This study was carried out with the aim of assessing the effect of accelerated erosion on soil productivity of a humic nitisol at Kabete, Kenya. Twenty runoff plots which had been subjected to varying levels of ero¬sion for four seasons (from 1991 to 1992) were planted with maize during the 1993 long-rains. Ten of the plots were cropped with maize under fertilized conditions while the rest were cropped with maize under non-fertilized conditions. There was very little change in soil physi¬cal properties following erosion. However, there was a decrease in percentage volu¬metric water content after four seasons at pressure heads between - 100cm to - 1500 em. Differences in %C, %N and available P between the least and most eroded plots were significant at the 0.01 probability level. Maize grain and above-ground dry matter yields and crop height were always greater in the least eroded plots compared to the more eroded plots in both fertilized and non-fertilized crops. These crop para¬meters were highly and negatively correlat¬ed with cumulative soil loss. Relative to the least eroded plot, there was a decline in maize grain yields of 214 kg ha-l cm-l of topsoil lost. Plant height was reduced 34cm per cm of soil lost for the first 2.5cm of topsoil.