IRRI - International Rice Research Institute

Farmers in China can reduce their current high rates of nitrogen (N) fertilizer through site-specific nutrient management (SSNM). This approach maintains high yield and can protect the environment by avoiding loss of excess N fertilizer into surface and ground water.

Farmers in China routinely use high rates of N fertilizer, which is often ineffectively utilized by rice because of improper timing and rates of application. For example, farmers at a study site in Jinhua, Zhejiang Province, apply nearly all their N fertilizer in two large doses of about 40 to 160 kg N ha-1 within the first two weeks after transplanting.

Researchers from Zhejiang University are working with farmers to demonstrate a site-specific nutrient management (SSNM) approach in which smaller applications of N fertilizer are timed during rice growth to match the plants' need for N. Farmers were initially reluctant to participate when they heard that researchers intended to apply 90% of the N fertilizer between mid-tillering and panicle initiation.

The farmers quickly became believers in the SSNM approach when demonstration plots in the pilot village of Tianmushan in 2001 revealed substantial opportunities to reduce N fertilizer consumption and increase rice yield. Grain yield increased by at least 0.5 t ha-1 in both the early and late rice cropping seasons despite a reduction in N fertilizer use of 10-30% (see table). Both N fertilizer recovery and agronomic efficiency (increase in grain yield per unit of N fertilizer applied) also increased significantly.

The agronomic performance of SSNM as compared with farmers' fertilizer practice (FFP) in 2001 in Tianmushan village in China. Values are the average of ten farms.

Parameter	Unit	FFP	SSNM
Early rice
Grain yield	t/ha	6.5	7.2
N fertilizer	kg/ha	122	110
P fertilizer	kg/ha	15	16
K fertilizer	kg/ha	30	60
N recovery efficiency	kg/kg
Agronomic N efficiency	kg/kg	12	19
Late rice
Grain yield	t/ha	7.1	7.6
N fertilizer	kg/ha	169	120
P fertilizer	kg/ha	17	16
K fertilizer	kg/ha	58	60
N recovery efficiency	kg/kg	0.18	0.30
Agronomic N efficiency	kg/kg	12	19

The new SSNM approach for N fertilization is being disseminated to more farmers in 2002. In addition, activities also expanded in 2001 to include sites in the provinces of Jiangsu, Hunan and Guangdong. For further information, contact Prof. Wang Guanghuo (ghwang@mail.hz.zj.cn) at Zhejiang University.

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Efficient N fertilizer use to protect the environment