Influence of successive application using various animal waste composts and the difference of weather condition by year on the yield of sweet potato [Ipomoea batatas]

"Some kinds of animal waste composts and chemical fertilizer were applied successively in cropping system of sweet potato and barley by open ground condition on andosols. It was assumed that availability of nitrogen of animal waste composts was 50 percent compared with chemical fertilizer. Therefore, we analyzed the relationships between differences of yields of sweet potato and weather conditions by year. The results obtained were summarized as follows; 1 Successive application of poultry waste compost was the highest, and next was swine waste, cattle waste, and chemical fertilizer was the lowest, concerning yields of sweet potato. Yields applied successively with animal waste composts were difficult to influence by the amount of rainfall in the growing period compared with chemical fertilizer. 2 Nitrogen availability of chemical fertilizer declined remarkably as the amount of rainfall, however, this tendency was not admitted in successive application of animal waste composts. 3 Readily decomposable organic matter and exchangeable potassium were much remained in soil by successive application of cattle waste compost. And leaching of cation exchangeable bases were little concerning plot of swine and poultry waste composts. We consider these reason was that mineralization of nutrient of swine and poultry waste compost was slow. 4 It was the year of low temperature, much rain and little daylight in 1993, and this year was an unusual weather. The decreasing rate of the yield was low on the plot applied successively with animal waste composts compared with chemical fertilizer under these weather conditional year. 5 From these results, successive application of animal waste composts were made clear effectivity to yields of sweet potato. Because, yields of these growing was difficult to influence by the weather factors and also the decline rate of yields was low in the unusual weather year."