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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

Nutrient Omission Plot Technique

Background

The nutrient omission plot technique is a tool for determining the amount of fertilizer N, P, and K required for attaining a yield target (Fig. 1). In this technique, four 25m² plots with the following treatments are placed in a farmer’s field:

1.      Full fertilization: NPK applied

2.      N omission (–N): No N applied, PK applied

3.      P omission (–P): No P applied, NK applied

4.      K omission (–K): No K applied, NP applied

Fertilizer N, P, and K are applied at sufficiently high rates to ensure that yield is not limited by an insufficient supply of the added nutrients. Grain yield in the plot with full fertilization and relatively good crop management can be used to estimate an attainable yield target. Nutrient-limited yields are determined from plots in which the nutrient of interest is not added. For example, the N-limited yield is determined in an N omission plot receiving no N fertilizer but sufficient P and K to ensure that they do not limit yield. The K-limited yield is determined in a K omission plot receiving no K fertilizer but a sufficient supply of other nutrients.

The difference in grain yields between a fully fertilized plot and an N omission plot illustrates the deficit between the crop demand for N and indigenous supply of N, which must be met by fertilizers. Similarly, the difference in grain yields between a fully fertilized plot and a K omission plot illustrates the deficit between the crop demand for K and indigenous supply of K, which must be met by fertilizers.

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