Phosphorus and Potassium Balances of Cabagge at Different Soil Conservation Techniques in Talun Berasap, Indonesia

Study on phosphorus and potassium balances of cabbage at different soil conservation techniques was conducted in Talun Berasap, a vegetables growing area in Kerinci District, Indonesia in 2011. Four treatments were tested including control, a farmers practices with the direction of planting in line with slop (KTA-1), modification of farmer practice by adding ridge terrace every 5 m of slope length (KTA-2), modification of farmer practice by adding ridge terrace and hill side ditch every 5 m of slope length (KTA-3), and (4) planting in line with contour (KTA-4). Phosphorus and potassium balances were calculated according to the differences between phosphorus and potassium gains and losses. To quantify total phosphorus and potassium inputs, P and K contents in SP-36 and KCl, rate of compost, P and K concentrations in compost, as well as P and K concentrations in rainfall were collected. Output parameters were cabbage yield, crop residues production, P and K concentrations in cabbage and crop residues as well as erosion. The results indicated that positive balances of phosphorus and potassium were taken place in all treatments. Concerning the environmental, agronomical and economic point of views as well as to get higher cabbage yield and stabile, recommended SP-36 application rate should be 100 kg SP-36 and 50 kg KCl ha-1 season-1 with adding more compost up to 20 - 30 tons ha-1 season-1.