暖地型マメ科・イネ科両草種の混ぜ播栽培に関する研究 : IV.混ぜ播草地におけるマメ科草の生育と根粒形成におよぼす窒素施肥の影響

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The effects of various rates and methods of N application on the growth and nodulation of Desmodium intortum cv. Greenleaf (De) mixed with Setaria anceps cv. Kazungula (Ks) were studied. To study those effects, 9 treatments of 3 N rates×3 methods of N application to the mixture (M) were made. Also, 3 treatments with no N on the mixture and pure stands of individual legume and grass were included as shown below. The treatments were replicated 3 times. [table] The plants were arranged in a 15cm×15cm grid in the pure stands and alternately in the mixture. Plot size was 2×3m each. Urea was applied just before transplanting (basal N) and an additional N was applied after the first clipping in the first year. Sufficient amounts of the other needed nutrients were applied. Items studied were total DM and total N yield, nodule number and nodule weight. Clippings were imposed when the mean height of any treatment reached 50cm. Three soil cores (10cm diameter×10cm length) per plot, each core representing three plant roots of De, were sampled for the nodule counting. Results obtained are as follows: 1) The growth of De was poor in the first year. DM yield was highest in 16 N due to the vigorous Ks component. The effects of N in increasing DM yield were observed up to the sencond clipping (Fig.1). DM yields were highest under 8N in the second year due to the effect of the legume mixture (Table 1). 2) The mixture effect was calculated as described below (Fig.2). [numerical formula] The effects on De were also calculated in the same way. The mixture effects were significant in the second year. Both Ks and De components in the mixture showed increase in DM yields. 3) DM yields increased in 4N and more significantly in 8N when total N was applied before transplanting (Table 7). This might be attributed to the following: a) In the first year, better establishment of Ks were observed as N rates were increased; b) In the second year, the mixture effects were increased in those plots. 4) Increased N yield followed the pattern of the increase in DM yields. DM yield of De increased in 4N and 8N and decreased in 16N as compared to ON (Table 2). N content of Ks component in all the treatments showed almost identical values at the third clipping (Fig.3). N contents of De component at the third clipping were higher in 4N and 8 than in ON and 16N. Active N fixation might be suggested in 4N and 8N. 5) The effects of basal N rates on the nodule formation were examined at the first clipping in the first year (Table 3). The nodule formation and development were stimulated with increased N rates up to 8kg N/10a as compared with Okg N, and decreased with 16kg N. Also, the number of white nodules per plant were increased with 16kg N. The effects of basal-additional N ratio were evaluated in the 4N and 8N plots (Table 4). The number of nodules per plant and the weight per nodule were higher when all the N were applied as basal compared to the split application of N. 6) In view of the DM and N yields and the effects of N on the nodule formation in the first year and the mixture effects in the second year, the N rate of approximately 8kg/10a applied mainly as a basal is recommendable under the field conditions similar to this experimental field.
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 : IV.混ぜ播草地におけるマメ科草の生育と根粒形成におよぼす窒素施肥の影響

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