Technical aspects of the ngoro system of cultivation from a water and soil conservation viewpoint

Abstract

This paper describes the Ngoro system of soil and water conservation which is indigenous to the Mbinga District of SW Tanzania. It consists of a regular series of pits of around two metres square, with matrix of surrounding bund walls under which grass is buried and left to decompose. Crops are planted only on the bunds, not in the pit itself. The system is compared to ridges with and without buried organic residues, on 2 slope classes, in two areas in the district. It is difficult to draw definite conclusions based on only one seasons research: Contrary to expectation, one year after formation, soil % carbon and % nitrogen values were lower in ngoro. It appears that in several cases, the ngoro suffered more erosion than ridges but the majority of soil was redeposited in the pits, meaning a small, if any, net loss of soil, whereas in ridges, much soil was transported down the furrow and out of the studied area. Moisture content, especially in the side bunds was found to increase with increasing pit size. More work is needed to better understand the long term conserving performance of ngoro but the encouraging findings of this initial research have provided the basis for some recommendations to be made for improved efficiency.