Relationship between Root Distribution of Upland Crops and Yield : II. Influence of mulching methods, seeding times and plant densities on root distribution of upland-cultured paddy rice and upland rice

摘要

This experiment was conducted to clarify that the root distribution of upland-cultured paddy rice (var. Myojoo) and upland rice (var. Norin No. 21) in the soil was influenced by soil temperature. To obtain the different soil temperature, two mulching methods, three seeding times and two plant densities were adopted. The soil temperature was raised by transparent-polyethylene mulch and was lowered by aluminium-foil mulch and it was also lower in the early seeding than the late seeding and in the dense planting than the sparse planting. The results obtained are as follows. 1. The roots of upland-cultured paddy rice were distributed shallow in the soil at high soil temperature and deep in the soil at low soil temperature. 2. The root distribution of upland rice was not influenced by soil tempcrature because upland rice has genetically deep rooting in thc soil. 3. Seeding times grcately influenced the root systems of upland rice. The roots of upland rice in the rainy season (May 28) penetrated into the shallow layer of soil because of high soil moisture. Otherwise, that in the dry season (June 29) penetrated into the deep layer of soil because of low soil moisture. 4. The roots of upland-cultured paddy rice and upland rice in sparse plant density penetrated into the deep layer of soil, otherwise that in dense plant density penetrated the shallow layer of soil. 5. The top weight and the root weight of upland-cultured paddy rice were enhanced at high soil temperature.