Abstract
Effects of allotment of nitrogen (N) application on annual dry matter yield of three timothy-legume mixtures were investigated to determine the adequate allotment for obtaining the highest yield. Three timothy varieties were used in this experiment ; Kunpu (extremely early variety) for use of three cuts, Nosappu (early) and Hokushu (late) for use of two cuts. Each of these varieties was grown with legumes in Kunpu-, Nosappu- and Hokushu mixtures, respectively. Legumes tested were red clover (Trifolium pratense L., CV. Sapporo) and white clover (Trifolium repens L., CV. New Zealand). Application rate of N fertilizer was 8 kgN/10 a/year for each mixture. Results obtained were summarized as follows: 1. Total annual yields of timothy and legumes were closely correlated with annual yield of timothy, and both yields increased with higher application rates of N fertilizer at early spring. These tendencies were shown clearly in both Nosappu and Hokushu mixtures. 2. Within a range of allotments in this experiment, the adequate allotment of N fertilizer for the highest total annual yield in each mixture was clarified as follows: Kunpu mixture was in the ratio 3:2:1 alloted for early spring, after the 1st cutting and after the 2nd cutting. Both Nosappu and Hokushu mixtures were 2 to 1 proportion for early spring and after the 1st cutting. It seems that these adequate allotments coincided with those bringing the highest annual yield of timothy. 3. The increase in the 1st cutting yield of timothy was required for raising annual yield, and this increase was intensified by high amount of N absorbtion at this cutting. From the standpoint of morphological constituents, increases of yield were associated with the increase of their heading tillers in both Kunpu and Nosappu, while with that of elongating tillers in Hokushu. Securing of these contributing tillers for each variety, therefore, was important to increase the 1st cutting yield of timothy. 4. From the results described above, under the conditions where the same annual rates of N fertilizer were applied, the adequate allotment application method of N fertilizer for the highest annual yield in each timothy-legume mixture was that more rates of N fertilizer were alloted to the 1st cutting rather than the 2nd or 3rd cutting.
