Analisis kecukupan air di kebun belimbing manis (Averrhoa carambola L)

Abstract

Problem faced by star fruit farmers in Depok, West Java, is water availability relying only on rainfed which the quantity is always unevenly distributed in each year. The abundant water availability during the rainy season has not been optimally utilized so that water stress often occurs during the dry season. Therefore, research related to water conservation technique for optimum utilization of rain water and runoff for star fruit in that area was conducted. The objectives of the research were: 1) to develop water balance analytical model with and without runoff for the sweet star fruit orchard, 2) to find out the effectiveness of water harvest technique using infiltration canal and silt pit to control runoff and change soil water content at the star fruit orchard, and 3) to find out the relationship of evapotranspiration and star fruit productivity. In this experiment the water table was approximately 16 m from the soil surface, no irrigation was used and infiltration canals equipped with silt pits were constructed so that runoff component and contribution of water capillarity movement were zero. The research results showed that: 1) the water balance analytical model without runoff could nicely simulate the soil water content at the rooting zone with R2 of 0.83 and RSME of 0.001; 2) the water balance analytical model with runoff could nicely simulate the soil water content at the rooting zone with R2 of 0.82 and RSME of 0.007; 3) the water harvest technique was effective in controlling runoff which was indicated by the higher soil water content at the rooting zone ranging from 0.429 to 0.458 m3/m3 with an average of 0.452 m3/m3 as compared to control (with no water harvest technique) ranging from 0.362 to 0.458 m3/m3with an average of 0.417 m3/m3; 4) productivity of the star fruit increased with the increase of evapotranspiration as expressed by the following linear regression equation: Y = 0,299X – 13,93 with R2 of 0.74, F value of 5.56 at p~0.81, indicating that evapotranspiration had influence on the star fruit productivity.; and 5) with water harvest technique treatment (infiltration canal with silt pit), the value of soil water content at the star fruit orchard was in good condition for the growth and year-round production of the star fruit plants.