混作, 間作, 輪作における作物の生長と窒素の動態 : 第1報 アカクローバとの混作初期におけるイネ科牧草の生長

抄録

Three temperate grasses : orchardgrass (Dactylis glomerata L.), Italian ryegrass (Lolium multiflorum LAM.) and tall fescue (Festuca arundinacea SCHREB.), were grown singly or in mixture with red clover (Trifolium pratense L.) in 1/5000 a pots. The results are summarized as follows. 1. Red clover significantly accelerated the growth of companion temperate grasses in terms of dry weight and nitrogen content 22 days after mixed cropping in poor nitrogen soil (Figs. 1 and 2). This acceleration was also obtained 10 days after mixed cropping in solution culture containing no nitrogen fertilizer (Fig. 9). 2. This acceleration effect varies with grass species. In orchardgrass and Italian ryegrass, the effect was marked, whereas it was not marked in tall fescue (Figs. 1 and 2). 3. In case of no nitrogen fertilizer, the dry weight and nitrogen content per plant of orchardgrass were larger in mixed cropping with red clover than in single cropping 20 days after planting. With nitrogen 1 kg and 5 kg/10a, however, the orchardgrass dry weight was less in mixture than in single cropping. Nitrogen content of orchardgrass with nitrogen application was larger in mixture than in single cropping 90 days after planting (Figs. 5 and 6). 4. Culture solution of the single cropping of red clover and of the mixed cropping had a greater amount of organic nitrogen than the single cropping of orchardgrass 15 days after planting (Table 2.) 5. Dry weight and nitrogen content per plant of succeeding millet and wheat increased in cases where preceding cropping was single cropping of red clover and mixture. This acceleration effect varied with the species of three grasses in preceding cropping (Figs. 3 and 4). It is found from these results that growth of three temperate grasses are accelerated by mixed cropping with red clover soon after the beginning of cultivation in cases where the soil contains little nitrogen and also that the acceleration effect varies with the species of temperate grasses. It is suggested that growth acceleration of grasses raised with red clover in early stage of cultivation is probably due to absorbing nitrogen excreted directly from root system of red clover.