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Water and nitrogen management to increase agricultural production and improve environmental quality

Overview of Project

The overall objective of the project was to increase the efficiency of use of nitrogen in the North China Plain (NCP), to improve crop production and decrease contamination of groundwater with nitrate and to reduce emission of greenhouse gases. A parallel study was undertaken as part of a large more comprehensive project in northeastern Victoria. The need to identify optimum water, N and P management for production while minimizing environmental impacts is fundamental to the survival of Australian and Chinese agriculture. The challenge facing China’s agriculturalists and planners is how to meet the food demands of its 1.2 billion people. The North China Plain (NCP) supports a large population through intensive wheat-maize systems. Production is based on large inputs of inorganic fertiliser and irrigation water - more than 400 kg/ha of nitrogen and 450 mm of water each year. Improving productivity is the preferred option to meet demand and can be achieved by improved efficiency of fertiliser use (especially nitrogen) and improved management of water for irrigation.

Earlier ACIAR projects studied the efficiency of nitrogen fertilisers in flooded rice systems and how to maximize the benefits of biological nitrogen fixation, mostly at the plot scale. This project was orientated to the environmental impacts of nitrogen losses from agriculture at larger scales. Scientists quantified water, nitrogen (N) and phosphorus (P) losses from the soil-plant systems to the environment, and undertook systems modelling and study practices for crop, water and nutrient management.

Key Outcomes of Project

Project Outcomes

The project showed that on the NCP large losses of nitrogen and water occurred from maize grown in the warm and wet season, but losses from winter wheat were small. Losses of nitrogen were largely in the form of ammonia resulting from the application of urea to the relatively light and alkaline soils of the NCP.

The scientists found that simply changing farmers’ practices to applying urea just before irrigation markedly reduced gaseous losses of nitrogen. This practice is now being promoted to farmers around the experimental sites. For example, 20% of farmers near Fengqiu experimental station in Henan Province applied excessive N fertiliser and there was significant potential to reduce the N fertiliser input. A survey of Fengqiu county showed that the highest maize yields (not necessary the most economical yields) were achieved when 200-250 kg N/ha fertiliser was applied, but about 20% formers applied more than this amount. This excessive amount of N not only caused farmers financial losses but also increased the nitrate recharge into the ground water as a contaminant.

Using a GIS database the scientists graphically displayed the location of these farmers and advised them to reduce N use, and identify the real cause of their low yields by referring to their soil properties and management practices. The potential cost saving by using less N fertiliser with the possibility even to increase the yields is around RMB270,000 (A$63,000) for Fengqiu county, and RMB39m (A$9m) if extrapolated for all of Henan province.

For the first time in China the actual nitrate leaching was systematically measured and simulated. In the one ha experimental site in Fengqiu the nitrate leaching for the complete wheat-maize crops was 35 kg N/ha in the 1998-99 and 90 kg N/ha in 1999-2000, accounting for 8% and 18% applied N, respectively. This significant N leaching was caused by the excessive application of N fertiliser (466 kg N in 98-99 and 502 in 99-2000) and inappropriate and excessive irrigation (561 mm in 98-99 and 451mm in 99-2000). The county survey data showed no clear correlation between the amount of irrigation and maize yield. There was therefore significant room for reducing irrigation to reduce the nitrate leaching.

In northeast Victoria data collection and modelling at small catchment scales showed that even with P fertilisation (5-22 kg/ha P) that there was very little transport of P out of the catchments (0.1-0.7 kg/ha per year). There was a small decrease in drainage in high P input systems at Maindample (cocksfoot pasture) but the reverse was found at Ruffy (perennial natives). N losses were around 7 kg/ha per year in a dry year (1998) and 17 kg/ha per year in wetter years. It was found that grasses could not decrease drainage and therefore could not reduce rises in groundwater nor reduce salt rising up the profile. Deep-rooted perennials had to be used to reduce drainage."

Project Dates

01 Jan 1998 - 30 Jun 2003

Partners

China Agricultural University - China
Department of Natural Resources and Environment - Australia
Chinese Academy of Science - China
University of Melbourne

Leaders

Prof Robert White

Email

r.white@agriculture.unimelb.edu.au

Phone

03 8344 5013

Website
Launch Website