Site Specific Nutrient Management

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Guangdong, China

Research Results

Attainable yields and nutrient deficits (2004-05)

The nutrient omission plot technique was used to determine attainable yield with full fertilization and nutrient-limited yields (Table 1). Rice grain yield in plots fully fertilized with N, P, and K provided an estimate of the attainable yield target. The yield of rice not fertilized with N, but fertilized with other nutrients, was used to determine N-limited yield. Similarly, the yield of rice not fertilized with K, but receiving other nutrients, indicated K-limited yield. The difference between the yield target and a nutrient-limited yield indicated the crop response to the nutrient.

Table 1. Rice yields obtained with the nutrient omission plot technique in farmers’ fields in Guangdong, 2004-05.

Parameter	Early rice^a		Late rice^b
	Mean	SD	Mean	SD
Attainable yield target; yield with NPK (t ha⁻¹)	6.4	0.2	7.6	0.5
N-limited yield; yield without fertilizer N (t ha⁻¹)	5.0	0.4	4.7	0.6
Yield response to N (t ha⁻¹)	1.4	-	2.8	0.9
K-limited yield; yield without fertilizer K (t ha⁻¹)	-	-	7.2	0.6
Yield response to K (t ha⁻¹)	-	-	0.4	0.9

SD = standard deviation.

^a Estimated from field experiments conducted at Guangzhou in 2004 and 2005.

^b From the experiment conducted in 2004 late season in 10 farmers’ fields.