Influences of combing ridge and no-tillage on rice yield and soil temperature and distribution of aggregate in cold waterlogged field

Abstract: Cold waterlogged paddy field refers to the paddy field submerged under water for extensive period of time in a year. It has the characteristics of "cold in temperature, slush in tillage, rich in plant toxicants, and low in productivity". There are 267 to 400 million hectares of the cold-waterlogged field in China, accounting for 15.07% of the total paddy field area and 44.20% of low-yield paddy field area. Since the waterlogged paddy field has such a large acreage it has become a focus of study in order to make full use of it by increasing rice production. This study aimed to apply ridges and no-tillage together to improve cold spring mud type of cold waterlogged paddy field for rice production in field experiment in 2011 and 2012. Rice was planted by using techniques of conventional till and no till combined with ridging with heights of 10 (LG10), 15 (LG15) and 20 cm (LG20). Soil temperature was monitored throughout the growing season. Rice yields and its component were measured and aggregate distribution was determined from soil samples taken at 0-20 cm depth at the end of the experiment. The results showed that the ridge culture could increase rice yield markedly in cold water-logged paddy field. The rice yield in the LG15 treatment was 10.95% and 18.51% higher (P<0.05) than conventional till in 2011 and 2012, respectively. The ridge culture improved soil temperature of the cold water-logged paddy field as compared to the conventional till. Soil temperature in the LG15 treatment was higher (P<0.05) among different treatments. On an average, soil temperature in ridging treatments was increased by 0.2℃-1.2℃ in 0-5 cm soil depth. Different ridge height had effect on the distribution of soil aggregates: large soil aggregates (>1 mm) in the ridging treatments increased greatly in 0-5 cm depth, but highest in LG15 and lowest in conventional till treatment in 5-25 cm. Effect of ridging on soil aggregate distribution on formation of soil aggregate was obvious in 0-5 cm than 5-25 cm. After ridging, the content of large soil aggregate at 0-5 cm soil depth was higher than that at 5-25 cm. However, there was no positive correlation between ridge height and soil temperature and large soil aggregate. In summary, the ridge height under no-tillage of the cold water-logged paddy field was best at 15 cm for rice production.