Relationship between root distribution of upland crops and their yield 3. influence of soil moisture levels on root distribution and root dry matter of upland cultured paddy rice cross bred rice of paddy rice and upland rice and upland rice
Banba, H.; Ohkubo, T.
Japanese Journal of Crop Science 50(1): 1-7
This experiment was conducted to clarify the effects of different soil moisture levels on the root distribution and root dry matter of upland-cultured paddy rice (cv. Myojoo, Kochihibiki), crossbred rice of paddy rice and upland rice (cv. Ishioka glutinous No. 10, Mizuhatamochi) and upland rice (cv. Norin No. 12, Norin No. 21). In the 1st experiment (1977) the root distribution and dry matter was investigated on the 6 cultivars which were cultivated under irrigation and nonirrigation. The irrigation treatments were begun at July 18. The soil moisture tension of the 2 irrigation plots were at pF 2.5 and pF 2.0 at 10 cm depth, respectively. During July 24 to Aug. 8 the soil moisture tension of nonirrigation plot was over pF 2.9 and in the range of pF 2.5-2.9, at 10 cm and 30 cm depths, respectively. The soil moisture of nonirrigation plots reached to first permanent wilting point Aug. 4. Top dry matter, root dry matter and root distribution were investigated at maturity. Root distribution was studied by excavating soil masses, which were sectioned by 7 cm increments up to 35 cm depth. The 2nd experiment (1978) was set up in cylindrical plastic pots of 30 cm height and 25 cm inner diameter using four cultivars (Myojoo, Mizuhatamochi, Norin No. 12, Norin No. 21). Soil moisture treatments ccomposed by 2 levels of high and low were begun at July 10. The high soil moisture plot was irrigated every day. Low soil moisture plot was irrigated when the soil moisture reached the permanent wilting point. Treatments continued for 58 days. Root distribution was effectively influenced by different soil moisture levels. Roots were concentrated in the shallow layer under irrigation, while the roots occurred in the deeper layer under nonirrigation. Root dry matter was influenced by different soil moisture levels. The root dry matter was increased in drier soil condition, where rice plants proliferated numerous branches to take up a small amount of soil water. The root dry matter of upland rice cultivar Norin No. 12 was increased conspicuously in the surface layer under nonirrigation. The high growth rate of root weights in water stressed rice plants was correlated with drought resistance.