Stagnancy of Water in Paddy Soils Under the Triple Cropping System and its Improvement

Abstract

Shiyue Production Brigade is located on the north bank of the Changjiang River at the foot of the Dabie Mountain. The soils developed on granitic gneiss in situ or washed down from upper stream are of the Yellow-brown earth type and has been under cultivation for hundreds of years. Paddy soils occupy about 90% of the total cultivated area in the Brigade, and most of paddy soils (approximately 70%) are distributed in the bottom of concave topography and slightly rolling flat land. Before 1955, the soils were given to doubie cropping system (rice-winter seed crop or green manure) a year. From 1956–1965, the cropping system was changed to double rice-green manure a year (rice-rice- milk vetch). From 1966–1972, part of milk vetch was replaced by barley, wheat or rapeseed. Owing to the improvements in production conditions and farming technique and the changes in the cropping system, the annual output of crops has remarkably increased. Since 1972, the area of rice-rice-winter seed cropping has been extended to 72% of the total paddy fields and the average yields per hectare of double cropping rice have gone up to 10500–12000 kg and that of wheat up to 1500–2250 kg (or rape-seed 750–1500 kg). However, as a result of the prolonging waterlogging each year, the properties of soil showed a tendency towards degradation and annual output stayed put or even decreased. In recent years, the Brigade practised a new system of rice-cotton rotation. One or two crops of cotton were grown between years of rice culture. The winter crops following cotton grew much better than those under the continuous triple cropping system. The rice crop grown the next year after cotton was also markedly improved.

The Project was carried out under direction of Prof. Chen Hua-kui.