Nutrients movement characteristic in terrace sawah occupied by cascade irrigation system in West Sumatra, Indonesia

Abstract

West Sumatra is one of Indonesian rice bowl. The landscape of this province dominated by mountainous 
area with beautiful terrace sawah lied from the middle slope to the lowland. The most common rice 
cultivation management in this area is application of cascade irrigation system with blanked amount of 
chemical fertilizer application. This study intends to figure out, whether this kind of sawah management 
sustains are friendly to the environment or not. The results showed that cascade irrigation system 
created some discrepancies in suspended solid (SS), dissolve organic matter (DOM) and the nutrient 
movement characteristic along the slope. The SS and DOM load and discharge strongly influenced by 
land preparation activities, while total and available nitrogen (N) and phosphorous (P) affected by 
chemical fertilizer application. In the upper part, the amount of chemical fertilizer seemed sufficient, 
indicated by negative amount of nutrient balance, while lower terrace show some indication of excess 
nutrient input. To avoid some demerit of cascade irrigation system, chemical fertilizer application should 
be base on site specific characteristic and taking into account of natural source contribution.