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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

Phosphorous and Potassium Management

Principles of P and K management

Phosphorus (P) and potassium (K) are essential elements for plant growth. Phosphorus is particularly important in the early growth stages. It promotes root development, tillering, and early flowering. Potassium strengthens plant cell walls, and contributes to greater canopy photosynthesis and crop growth. It does not have a pronounced effect on tillering, but it can increase the number of spikelets per panicle (flowers per grain bunch) and percentage of filled grain.

Rice plants obtain much of their required P and K from the soil, crop residues, organic amendments, and irrigation water; but the supply of P and K from these naturally occurring, indigenous sources are typically insufficient to sustain high rice yields. Supplemental P and K from fertilizers are thus essential for sustaining high and profitable yields of rice without depleting the fertility of soil.

Fertilizer P and K requirements for rice are determined with a nutrient decision support system (Witt and Dobermann 2004), which is derived from scientific principles within the QUEFTS model (Janssen et al. 1990, Witt et al. 1999). In this approach, recommended fertilizer P and K rates are sufficient to both overcome P and K deficiencies and maintain soil P and K fertility.

References 

Janssen BH, Guiking FCT, van der Eijk D, Smaling EMA, Wolf J, van Reuler H. 1990. A system for quantitative evaluation of the fertility of tropical soils (QUEFTS). Geoderma 46: 299-318.

Witt C, Buresh RJ, Peng S,  Balasubramanian V, Dobermann A. 2007. Nutrient management. In: Fairhurst TH, Witt C, Buresh R, Dobermann A, eds. Rice: A practical guide to nutrient management. Los Baños (Philippines) and Singapore: International Rice Research Institute(IRRI), International Plant Nutrition Institute (IPNI), and International Potash Institute (IPI).  p 1-45.

Witt C, Dobermann A. 2004. Toward a decision support system for site-specific nutrient management. In Dobermann A, Witt C, Dawe D (eds). Increasing the productivity of intensive rice systems through site-specific nutrient management. Enfield, NH (USA) and Los Baños (Philippines): Science Publishers, Inc., and International Rice Research Institute (IRRI).

p 359-395

Witt C, Dobermann A, Abdulrachman S, Gines GC, Wang GH, Nagarajan R, Satawathananont S, Son TT, Tan PS, Tiem LV, Simbahan GC, Olk DC. 1999. Internal nutrient efficiencies of irrigated lowland rice in tropical and subtropical Asia. Field Crops Res. 63:113-138.

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