This study evaluated the effect of organic fertilizer on the yield of sesame and the movement of nitrogen and carbon in soil under mulching cultivation. The seven fertilizer treatments investigated are as follows: 1) 8-4-9 kg N-P2O5-K2O 10a-1-control, 2) 80% of control treatment N from mixed expeller cake (MEC)-MEC 80%, 3) 100% of control treatment N from MEC-MEC 100%, 4) 80% of control treatment N from mixed organic fertilizer (MOF)MOF 80%, 5) 100% of control treatment N from MOF-MOF 100%, 6) 80% of control treatment N from latex coated urea complex fertilizer (LCU)-LCU 80%, and 7) no nitrogen. The soil mineral N available in the applied organic MEC and MOF fertilizers was less than the available N in the applied urea fertilizer during the early growth stage of sesame but the amount was observed to increase with time. The concentration of nitrate-N in leached solution 35 days after application was highest at 75 mg l-1 in the control, followed in descending order by MEC 100%, MOF 100%, LCU 80%, MOF 80% and MEC 80%. The concentration of nitrate-N in the leachate in all treatments was observed to rapidly decrease 45 days after fertilizer application and recorded at less than 20 mg l-1 65 days after application. The concentration of dissolved organic carbon in the leached solution and organic carbon in the soil of the organic fertilizer plots was higher than in the urea- and LCU-fertilized plots during the whole growing period. The yields of sesame applied with MEC and MOF organic fertilizers were 2 to 7% higher than those fertilized with urea. The amount of retained mineral N or organic carbon in the soil is higher in the LCU and organic fertilizer plots than in the urea-fertilized treatments, which resulted in the reduction of nitrate leaching, increasing N efficiency and sesame yield.

A long-term experiment was carried out to examine the effects of compost on the long-term trends and synergy effects with chemical fertilizer and saving the chemical fertilizers of paddy cropping. The experiment was conducted for the past 36 years with constant amounts of N, P, K and compost in a paddy field at Milyang, South Korea. Grain yield was significantly increased in the plots with compost application. Twenty five years after the compost treatment, grain yield was significantly increased and it reached almost 90% of NPK plots. The effect of rice straw compost on grain yield was not clear during the early cropping years about 60%, but it slightly increased there after about 95% during the late five years. In compost plots, soil organic matter content, K and SiO2 was greater in the compost applied plots than with application of recommended doses of NPK. However, soil pH was reduced in compost applied plots and Ca, and Mg were remained unchanged when compared to the application of recommended doses NPK. Soil nutrient contents were less in compost applied plots than with the application of recommended doses of NPK along with compost but was found to be increased than that of un-fertilized plots. The present study indicated that the application of rice straw compost with NPK is the best of all and followed by NPK and Compost. However, treatment of Compost is time consuming and hard working desired and eventually non economical practice in mechanized agricultural systems, even though Compost is very useful source of improving the soil fertility and its physical characteristics and also the application of inorganic N and P are essential for sustaining high yield.