Written Paper

Exploring options to combine high yields with high nitrogen use efficiencies in irrigated rice in China  [2007]

Jing, Q. Bouman, B.A.M. Hengsdijk, H. Keulen, H. van et al.

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In Jiangsu province, Southeast China, high irrigated rice yields (6-8000 kg ha-1) are supported by high nitrogen (N) fertilizer inputs (260-300 kg N ha-1) and low fertilizer N use efficiencies (recoveries of 30-35%). Improvement of fertilizer N use efficiency can increase farmers' profitability and reduce negative environmental externalities. This paper combines field experimentation with simulation modeling to explore N fertilizer management strategies to realize high yields, while increasing N use efficiency. The rice growth model ORYZA2000 was parameterized and evaluated using data from field experiments carried out in Nanjing, China. ORYZA2000 satisfactorily simulated yield, crop biomass and crop N dynamics, and the model was applied to explore options for different N-fertilizer management regimes, at low and high levels of indigenous soil N supply, using 43 years of historical weather data. On average, yields of around 10-11,000 kg ha-1 were realized (simulated and in field experiments) with fertilizer N rates of around 200 kg ha-1. Higher fertilizer doses did not result in substantially higher yields, except under very favorable weather conditions when yields exceeding 13,000 kg ha-1 were calculated. At fertilizer rates of 150-200 kg ha-1, and at the tested indigenous soil N supplies of 0.6-0.9 kg ha-1 day-1, high fertilizer N recovery (53-56%), partial N productivity (50-70 kg kg-1) and agronomic N use efficiency (20-30 kg kg-1) were obtained with a
pplication in three equal splits at transplanting, panicle initiation and booting. Increasing the number of splits to six did not further increase yield or improve any of the N use efficiency parameters.

From the journal

European journal of agronomy

ISSN : 1161-0301