水稲の乾田直播栽培における硝酸化成抑制剤の効果について : (第2報)2-Mercaptobenzothiazole(MBT)の効果と施肥体系について

Effect of the Nitrification Inhibitor on Nitrification of Ammonium Fertilizer and Yield of Rice Sown Directly on Unflooded Paddy Field. : Part 2. Effect of 2 Mercaptobenzothiazole (MBT) and Application Method of Fertilizer.

Creators Marumoto Takuya

Creators Kida Hideo

Creators Yamazaki Kinta

The purpose of this experiment is to evaluate the effect of a nitrification inhibitor, 2 Mercaptobenzothiazole (MBT ), on the nitrification of ammonium nitrogen applied to rice culture by direct sowing on unflooded field, and the yielding effects on the plant growth and grain yield. In addition to this, to get a fundamental information to establish an application method of the fertilizer containing the inhibitor in the rice culture, which is most profitable to increase the yield with less labor repuirement, is also the other purpose. The results obtained were as follows : 1 . MBT exhibited considerable effect of the inhibition on the nitrification of applied nitrogen, and NH4-N concentrations in soils of + MBT plots were higher than those in soils of -MBT plots during the early period of unflooded state. The inhibitory effect of MBT on nitrification, however, terminated within about 40 days. 2. MBT showed superior effect on the rice plant growth and the effect was large during the initial growth, but during the latter growth, it decreased gradually. Further, it was indicated that the effect decreased also with an increase of the times of split application. The total nitrogen absorption in the plant was higher in the plots of split application than that of whole basal application. And the nitrogen utilization coefficient of rice plant in the +MBT plot of whole basal application considerably higher than that in the -MBT plot, but it was remarkably lower than those in the plots of split application. 3. The yielding effect of MBT on the rice grain yield was clearly recognized in every plots, especially the effect was large in the plot of whole basal application. The grain yield of +MBT plot of whole basal application was lower than those of every-MBT plots of split application. The grain yields of + MBT plots of split application showed the following order: A(8-8-0-0)>D(8-3-3.2) ?B(4-12-0.0) >C(8-6-0.2). 4 . From the results mentioned above, it was showed that the MBT added to the fertilizer for basal application exhibited considerable effect on an increase of the rice grain yield. However, it was indicated that, even if the MBT was added to the fertilizer for basal application, some additional dressing was necessary to maintain the predominancy of the initial plant growth till later stage and to get consequently the high grain yield. And, from the result that the grain yields of the plots applicated preponderantly additional dressing at flooded stage ( namely, +MBT plots of A (8 8 0 0) and B (4 -12 0 0)) coresponded to that of the plot applicated the common additional dressing (namely, +MBT plot of D (8 3 3 2) ), the omissible possibility of labor by the omission of the additional dressings after having been flooded was suggested. 5. Almost no physiological obstacle of MBT on rice plant was observed throughout all the growing stages. (Received June 30, 1974)

[ISSN]0513-1715

[NCID]AN00244250