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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
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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

Tamil Nadu, India

Attainable yield and nutrient deficits

The nutrient omission plot technique was used to determine attainable yield with full fertilization and nutrient-limited yields. Table 1 shows the results in 2002 to 2004. 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 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 <0.5 t ha⁻¹ in both the Old and New Delta for both kuruvai and thaladi seasons. Crop response to K averaged 0.5 t ha⁻¹ for both kuruvai and thaladi in the Old Delta and >0.5 t ha⁻¹ for both seasons in the New Delta.

Table 1. Attainable yield and nutrient deficits in the Old and New Delta in Tamil Nadu, 2002 to 2004. Values shown are means and standard deviation (SD) of 25–40 farms per location and season.

SSNM-based nutrient requirements

The SSNM approach was used to estimate fertilizer N and P₂O₅ requirements from Table 1. 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 fertilizer N⁻¹) of 20 for both the kuruvai and thaladi seasons. See N management for more details.

Total fertilizer P₂O₅ and K₂O were estimated from attainable yield target, P-limited yield, and K-limited yield (Table 1) using the nutrient decision support system (NuDSS) software. Straw input was estimated as 1 t ha⁻¹ for the kuruvai season and 2 t ha⁻¹ for the thaladi season.

Table 2. Fertilizer N, P₂O₅, and K₂O requirements for rice estimated from results with the nutrient omission plot technique in the Old and New Delta in Tamil Nadu, India, 2002 to 2004. Values shown are means and standard deviation (SD) of 25–40 farms per location and season.

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