The influence of swine-waste irrigation on grain quality in rice (Oryza sativa. L.): I. The effect of field irrigation with swine-waste on the rice quality

To recycle use swine-waste and reduce its pollutant impact on environment, the objective of this study has been to investigate the effect of applying swine-waste in irrigation system of rice on grain quality. A field experiment was performed in the 1st and 2nd crops of 1992, the influence of irrigation treated with swine-waste on rice grain quality was investigated. The field was divided into 6 sections based on their distance from irrigation gate, the grain quality of rice in each section was measured. Grain quality of a field with swine-waste irrigation over consecutive 7 years was also measured. Using soil nitrogen content as an index of the impact of swine-waste treatment, soil nitrogen content of each section was positively correlated with its distance from the gate. In milling quality, treatment with ground water (control) had higher brown and head rice ratio, especially in the 1st crop. Grain size was not affected by treatment. Ground water irrigation had the highest translucency. Significant difference on grain chalkiness was found only in the 2nd crop, the lowest white center and white belly appeared in the grain of sections 4 m and 10 m from irrigation gate respectively. In chemical quality, treatment had no effect on grain alkali spreading value and amylose content. Grains of treated sections showed higher crude protein content than those of ground water irrigation. Texture of grains from swine-waste treatment showed significant lower value in hardness, viscouseness and balance, but not in cohesiveness. Grains from the field of consecutive-waste treatment had the worst value in adhesiveness and stickiness, and in turn a lower palatability index. The present results suggest that irrigation with low concentration of swine-waste may not have significant influence on grain quality, but the long-term accumulative effect should be taken for cautiousness.