水稲晩植による減収機構の解析 (要旨) : 〔第2報〕 苗代に於ける発育干渉

抄録

1. When transplanting of rice seedlings is, delayed because of prolonged harvest of winter crops (such as barley, wheat, potato and rape, etc.), the seedlings are grown in the nursery for an improperly long period causing a shortage of space for individnal growth. Consequently the yield of the crop decreases remarkably owing to shortening of growing period after transplanting and besides to the mutual growth interference of the seedlings in the nursery. 2. The authors investigated. the growth (height of plants, increase of tillers and weight of plants) of rice seedlings under different experimental conditions ; i. e. the seeds were sown at each of five different densities (amount of seeds ; 541 cc, 180 cc, 54 cc, 18 cc, and 5.4 cc per 3.3 m²). Two varieties, "Sekiyama" a variety of heavy-panicle type and, , Ou-No. 195", a mediate-type were used. 3. The seedlings grown in sparsely sown plot produced tillers regularly and had mote than 18 tillers at the time of transplanting. Interference of growth occured late, because each seedlings had good enough space to grow. But the seedlings in densely sown plot suffered interference of growth at early stage of growth and had no tillers at the time of transplanting. 4. The numder of days after sowing to the time when tillering ceased is shown in the following table. The time of the initiation of the interference of mediate type was earlier than that, of heavy-panicle type. 5. When rice plants are to be transplanted lately than usual, it is necessary to take into consideration the relation between the sowing density and the initiation of the growth interference of plants in nursery.