Effects of nitrogen supply from irrigation water on rice production
2010
Hirai, Y., Kyushu Univ., Fukuoka (Japan). Faculty of Agriculture | Kawai, K. | Yokoyama, M. | Beppu, Y. | Mouri, M. | Hamagami, K.
Between 2006 and 2008, we surveyed the rice production in Hoshino village, Fukuoka prefecture, Japan, and examined the quality of irrigation water in this region. Through the survey, we obtained data for the 3 paddy fields where the same cultivar (Yumetsukushi) was cultivated in irrigation water with a wide range of inorganic nitrogen concentrations. In the field located downstream to tea fields, where large amounts of nitrogen fertilizers are used, and located upstream to a water system with small water volumes, the inorganic nitrogen concentrations in irrigation water were high (4.98 to 13.67mg/L) during the rice-growth season. This field showed notably higher SPAD values as compared to other fields where the amounts of basal nitrogen fertilization were equivalent or larger. In this field, the 100-grain weight was large, and the protein content and weight of brown rice were the highest among the 3 paddy fields. Further, nitrogen supply from the irrigation water and the amount of nitrogen absorbed by rice were roughly calculated. The results of the calculation indicated that rice cultivation without nitrogen fertilization is possible in the field where inorganic nitrogen concentration in irrigation water is the highest.
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