Effect of Nitrogen Application Levels on Nitrate Concentration in Soil Solution under Plastic Film House

Abstract

This study was conducted to investigate investigated the effect of nitrogen fertilizer on nitrate concentration in soil solution and to determine the relationship between yield and nitrate concentration in soil solution for cucumber cultivation under plastic film house. Nitrogen as urea was applied at rates of 0, 120, 240, 360, and <TEX>$480kg\;N\;ha^{-1}$</TEX> as an additional fertilizer by trickle irrigation during cucumber cultivation. Monitoring of nitrate concentration in soil solution was investigated using porous cups at 25 cm depth under soil surface. Nitrate concentration in soil solution increased with increasing the rate of additional nitrogen. Correlation coefficient between EC value and nitrate concentration was positive in soil and soil solution (p<0.05). An additional nitrogen of about <TEX>$300kg\;ha^{-1}$</TEX> was shown the highest yield of cucumber, and improved yield by 5% compared to N recommendation of <TEX>$240kg\;N\;ha^{-1}$</TEX>. The highest yield was determined at nitrate concentration of <TEX>$82mg\;L^{-1}$</TEX> in soil solution by regression equation (<TEX>$Y=74.2+0.73X+0.000504X^2$</TEX>, <TEX>$R^2=0.629^*$</TEX>). These results means indicate that nitrate concentration in soil solution would be useful method to rapid determination for additional nitrogen during cucumber cultivation under plastic film house.