Impacts of different fertilizers/amendments on rice yield and nutrient uptake and soil properties in the waterlogged paddy field

【Objective】 Poor rice growth in waterlogged paddy fields of the southwest China is usually attributed to a number of adverse soil factors, including physical, chemical and biological factors. Aiming at the adverse soil factors limiting rice growth in waterlogged paddy fields, a field experiment was carried out to study impacts of different fertilizers/amendments on grain yield and nutrient uptake by rice and soil properties and to offer scientific and practical techniques to improve soil fertility, better land use and enhancerice yield in this type of soils. 【Methods】 A two-year field experiment was carried out in Luxian County of the southwest Sichuan, where waterlogged paddy fields prevail. The experiment was set up in a randomized design consisting of nine treatments, including CK(no fertilizers), NPK(nitrogen, phosphorus, potassium chemical fertilizer), NPK+Pe(NPK plus peat), NPK+COF(NPK plus commodity organic fertilizer), NPK+CM(NPK plus chicken manure), NPK+ Si(NPK plus silicon fertilizer), NPK + L(NPK plus lime), NPK +SiCa(NPK plus silicon calcium fertilizer) and NPK + Zn(NPK plus zinc fertilizer). Rice plants were sampled from each treatment two days before the harvest to analyze agronomic traits, uptake of total nitrogen, phosphorus and potassium by rice as affected by different treatments. Soil samples were collected from each plot right after the harvest to determine effects of different treatments on soil pH, total nitrogen, available phosphorus, available potassium, organic matter, total reductants, active reductants, total iron and manganese. 【Results】 The lime and the silicon-calcium fertilizer treatments are capable of improving the yield forming factors and thus, significantly increase rice yields by 15.40% and 10.64% compared to the NPK chemical fertilizer treatment, while other treatments insignificantly increased the rice yield. The application of lime and silicon-calcium fertilizers increase soil pH, significantly decrease soil total reductants and active reductants including Fe2+ and Mn2+ and improve soil nutrient availabilities, so stimulate the N, P and K uptakes of rice, which is an indirect contribution of the two treatments to rice yield increase via the improved soil chemical properties. Besides, the two treatments also directly contribute to the rice yield increase via the improved nutritional status of the rice since the soil is both calcium and silicon deficient. The effects of the organic fertilizers, chicken manure in particular, on the measured soil properties are just opposite to the lime and the silicon-calcium fertilizers. Addition of the zinc fertilizer insignificantly increases rice yield. The post-harvest soil residual nutrient status is closely related to quantity of nutrient input and removal by rice plants. 【Conclusions】 In the long-term waterlogged acidic paddy fields with low depression landscape, lime and silicon-calcium fertilizers are recommonded soil amendments, which can improve not only the soil properties but also the rice yield. Organic manure, the not fully decomposed manures or organic materials in particular, should be avoided to use in this kind of paddy fields.