Site-specific nutrient management for maize in tropical, favorable environments

The principles of SSNM
The principles of site-specific nutrient management (SSNM) are generic and applicable to other crops. In the presentation below we apply the most recently published principles of SSNM developed for rice (Buresh and Witt 2007; IRRI 2007) to maize in Asia.

SSNM provides an approach for “feeding” crops with nutrients as and when needed. This approach advocates:
• optimal use of existing indigenous nutrient sources, including crop residues and manures, and
• timely application of fertilizers at optimal rates to meet the deficit between the nutrient needs of a high-yielding crop and the indigenous nutrient supply

The SSNM approach is illustrated below in three basic steps:



Step 1: Establish an attainable yield level
Maize yields are location and season specific — depending upon climate, variety, and crop management. The attainable yield for a given location and season is estimated from farmers’ fields where good crop management was practiced and nutrients were not limiting yield. The amount of nutrients taken up by a maize crop is directly related to yield. The attainable yield level therefore indicates the total amount of nutrients that must be taken up by the crop.

Step 2: Effectively use existing nutrients
The SSNM approach promotes the optimal use of existing (indigenous) nutrients coming from the soil, organic amendments, crop residue, manure, and irrigation water. The uptake of a nutrient from indigenous sources can be estimated from the nutrient-limited yield, which is the grain yield for a crop not fertilized with the nutrient of interest but fertilized with other nutrients to ensure they do not limit yield.

Step 3: Apply fertilizer to fill the deficit between crop needs and indigenous supply
Fertilizer N, P, and K are applied to supplement the nutrients from indigenous sources and achieve the yield target (= attainable yield). The quantity of required fertilizer is determined by the deficit between the crop’s total needs for nutrients — as determined by the attainable yield level — and the supply of these nutrients from indigenous sources — as determined by the nutrient-limited yield.

Download the SSNM Manual for Maize.


References:

Buresh RJ, Witt C. 2007. Research Findings: III The principles of Site-Specific Nutrient Management [online]. Available at http://www.ipipotash.org/e-ifc/2006-10/research3.php (last update 2007).

IRRI. 2007. Site-specific nutrient management [online]. Available at www.irri.org/irrc/ssnm (last update 2007; accessed 05 Dec. 2007).