暖地型マメ科・イネ科両草種の混ぜ播栽培に関する研究 : V.デスモディウムの初期生育および根粒菌の窒素固定におよぼす温度・光量および窒素施肥量の影響

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The effects of various conditions of temperatures and light intensities and rates of N application on the early growth of Desmodium intortum cv. Greenleaf and its symbiotic N fixation were studied using the ^<15>N. To study those effects, 24 treatments of 3 temperature regimes (20°, 25°, and 30℃ of the day and night temperatures)×2 light intensities [full light (L) and shade (S), 50% of full light]×4 rates of N application (0N, 1N, 2N and 4N) were made. Plants were sampled 40 days after the treatments were imposed. (N≒1kg/10a) Items studied were total DM yield, Leaf Area, nodule number, nodule weight, total N yield and the portions of N originated from N fertilizer and symbiotically fixed N. Results obtained are as follows: 1) DM yield (Table 1) increased with higher temperature and increased rates of N application. However, at 25℃ under S treatment, DM yield was lower at 4N as compared with 2N. DM yield decreased in the S except for 1N and 2N under 25℃. 2) Leaf Area increased with the higher temperature (Fig.2) and with the S under 25℃. It also increased with 1N and 2N and in some cases with 4N. DM yield per Leaf Area was higher in the order of 25>30>20℃, and also it was higher in the S than in the L. In the L, DM yield per Leaf Area increased with the increased rates of N application excluding 4N under 25℃. There was no significant variation in DM yield per Leaf Area under S. 3) Total nodule number and weight increased with N applications up to 2N (Table 2) and decreased with 4N except in a few cases. They also increased at higher temperatures and L except at 25℃. The weight per nodule increased under higher temperatures and with the N application as compared with no nitrogen application except in 4N. The nodule weight. per Leaf Area increased under 20℃, and no significant differences were observed between 25℃ and 30℃. It also decreased with the increased rates of N application. The nodule weight per DM yield was not significantly affected by temperatures, but decreased with the L. 4) N contents of plants under 25℃ were higher with the increased rates of N application and no clear-cut differences were observed between the L and the S. In the L under 25℃ and 30℃, N contents decreased with the increased rates of N application in contrast to that in the S. Total N yield (Fig.2) increased as the rates of N application were increased except for 4N under 25℃. The amount of N in the plant originated from the N fertilizer in creased linearly as the rates of N application were increased. By contrast, the amount of symbiotically fixed N increased with decreased rates of N application and decreased with in creased rates of N application; and it was stimulated more under higher temperature, but not under the S at 20°and 30℃. The amounts of symbiotically fixed N per nodule (Table 4) were significantly decreased under 20℃ as compared with under 25℃ and 30℃. This also increased with the N application in the S but not in the L. 5) Results outlined above were discussed in view of the differences between the symbiotic N fixation and the absorption of the fertilizer N in terms of the range of temperatul requirements for optimum activity, the effects of N on the nitrogenase and Leghaemoglobin syntheses and differences between the symbiotic N fixation and the absorption of the N fertilizer in terms of carbon economy. It was concluded that the symbiotic N fixation was easily affected by the changes in environmental factors as compared with the absorption of the fertilizer N by plant. Also, the low rates of N application increased not only DM production but also the symbiotic N fixation even under low temperature provided light energy in sufficient amounts. Finally it can be stated that the N application at the low rates overcame the low rate of the symbiotic N fixation in the early spring of low temperature. Also, low rates of N application maximized both N yield and the symbiotic N fixation in the summer of high temperature and high light intensity. It can suggest that limited shading due to the associated grass will not severely reduce symbiotic N fixation except under low temperature.
日本草地学会の論文
1977-07-31

暖地型マメ科・イネ科両草種の混ぜ播栽培に関する研究 : V.デスモディウムの初期生育および根粒菌の窒素固定におよぼす温度・光量および窒素施肥量の影響

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