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  • SSNM approach
  • SSNM in three steps
  • Initial concept of SSNM
  • Current version of the SSNM approach
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  • Principles of N management
  • Background on making an N Recommendation
  • Using the SSNM approach to formulate locally adapted N recommendation
  • Using the Leaf Color Chart (LCC) for fertilizer N management
  • FAQs on N Management
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  • Principles of P and K management
  • Background on making P and K recommendations
  • Using SSNM approach to formulate P recommendations
  • Using SSNM approach to formulate K recommendations
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  • Bangladesh
  • China
  • India
  • Indonesia
  • Myanmar
  • Philippines
  • Vietnam
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  • Introduction to SSNM version 1.1
  • N management
  • P&K management
  • Implementing SSNM recommendations
  • Making an SSNM recommendation for rice
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  • SSNM: an approach for optimizing nutrient use in intensive rice production
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  • Nutrient omission plot
  • Potassium addition plot
  • Zinc addition plot

Mekong River Delta, Vietnam

Attainable yield and nutrient deficits with inbred rice in the Mekong Delta

The nutrient omission plot technique was used to determine attainable yield with full fertilization and nutrient-limited yields. Table 1 shows the results averaged for three provinces in 2002–03. Rice grain yield in plots fully fertilized with N, P, and K provided an estimate of the attainable yield target, which was higher in the dry than wet season. 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 P but receiving other nutrients indicated P-limited yield; and 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. Crop response to P averaged 1.2 t ha⁻¹ in the dry season and 0.8 t ha⁻¹ in the wet season. The K-limited yield was not determined during this period.

Table 1. Attainable yield and nutrient deficits with inbred rice in alluvial soils in three provinces (An Giang, Cantho, and Tien Giang) of the Mekong Delta, 2002-03.

SD = standard deviation; n = number of replicated plots

SSNM-based nutrient requirements

The SSNM approach was used to estimate fertilizer N and P₂O₅ requirements from Table 1. The fertilizer K₂O requirement for the wet season was estimated from data obtained in 1997 and 1998 in Cantho Province. Total fertilizer N required for rice (Table 2) was estimated from the measured response to N (Table 1) and assumed target agronomic efficiency of N (kg yield increase kg⁻¹ fertilizer N) of 25 for the dry season and 18 for wet season. See N management for more details.

Total fertilizer P₂O₅ and K₂O were estimated from attainable yield target, P-limited yield (Table 1), and K-limited yield (data not shown) using the nutrient decision support system (NuDSS). Straw input was estimated as 0.5 t ha⁻¹ for both seasons.

Table 2. Fertilizer N, P₂O₅, and K₂O requirements for rice in alluvial soil estimated from results with the nutrient omission plot technique in three provinces in the Mekong Delta, Vietnam, 2002-03.

SD = standard deviation; n = number of replicated plots

* Determined from data collected in 1997 and 1998 in Cantho Province (n = 36).

On-farm evaluation of SSNM in alluvial soil 

No Caption for figure 2

of fertilizer N, P₂O₅, and K₂O applied to rice per season with the farmers’ fertilizer practice (FFP) and site-specific nutrient management (SSNM) in the Mekong River Delta, Vietnam in 2001-04. Values shown are the means and standard deviation of 26-40 replicates per province.

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