Soil-water dynamics and crop productivity of a rainfed sorjan system in different landscape positions.

Sorjan refers to an Indonesian alternate raised bed (RB) and sink (S) or furrow system. Field trials were conducted in five different landscape positions or sites from May 1988 to Feb 1990 (four crop seasons) to determine the soil-water dynamics and agro-economic productivity of the sorjan system. The experimental sites were selected based on their diverse soil and land types, and drainage and flooding patterns. All experiments were laid-out in split-plot design replicated four times with bed management. RB was planted to mungbean during the wet season and corn and cowpea during the dry season and S was grown with rice. Results indicated that the drainage capacity of RB improved dramatically as compared to the conventional plot (CP) when the 25 cm high sorjan RB was constructed. A reduction in bulk density and an increase in saturated hydraulic conductivity brought about by the earth-moving operations also helped increases the permeability of the soil. The sorjan system in high landscape position did not show any yield and economic advantage over CP under normal rainfall condition. The sorjan system in impeded drainage soils remarkably increased the yield and economic returns as compared to CP. The economic performance of the sorjan system indicated that the field or sweet corn grown under RB was the most profitable crop. The mungbean-field corn pattern of RB was the highest income generating cropping pattern. The importance of improved drainage was also evident from the significant positive relationship between ground water table and grain yield as well as net return of mungbean and corn under CP. The sorjan trials although showed promising yield and crop growth performance of upland crops in RB, unlike those of S were not encouraging due to submergence and soil related problems.