Yield and nitrogen uptake of lowland rice (Oryza sativa L.) in a water-saving ground cover rice production system (GCRPS) in Beijing, North China
In this work, a new water-saving ‘Ground Cover Rice Production System (GCRPS)’ was evaluated for the understanding of growth and yield formation of lowland rice, N dynamics in plants-soil system, N-use efficiency, and Mn condition in the different systems. With GCRPS, lowland rice is cultivated under the soil humidity at approximately field capacity and mulched either by plastic film or straw in order to reduce evaporation. In the field experiment, the amount of irrigation water was significantly reduced by GCRPS, and water use efficiency was improved accordingly. However, plant growth and yield were limited, which was strongly related to leaf area index duration. Among yield components, the number of productive tillers had the largest effect on yield. The reduced tiller formation in GCRPS coincided with nutrient disorders, i.e., N and Mn deficiency. The N dynamics of GCRPS was characterised by surprisingly low N recoveries. NO3- leaching was probably the main pathway of N losses in the field condition of GCRPS. Fertiliser N split application improved N-use efficiency in 2002, but remained lower than paddy because of unavoidable leaching loss. Hence, the effect of soil humidity on growth and nutrient uptake was studied under greenhouse conditions. The soil redox-potential decreased sharply with higher soil humidity, which led to the increase of Mn accumulation in plant shoots under high humidity conditions. Lowland rice grown under saturated conditions performed best among treatments, characterised by the most vigour growth and optimal nutrient acquisition compared to other conditions. The experiment demonstrated that the GCRPS has a potential to save substantial amounts of water at relatively minor yield penalties, and the nutrients acquisition needs to be improved.
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