Agricultural Suitability and Potential Yields

The constraint-free crop yields calculated in the AEZ biomass model reflect yield potentials with regard to temperature, radiation and moisture regimes prevailing in the respective grid-cells. The model requires the following crop characteristics: Length of growth cycle (days from emergence to full maturity); length of yield formation period; maximum rate of photosynthesis at prevailing temperatures, leaf area index at maximum growth rate; harvest index; crop adaptability group; sensitivity of crop growth cycle length to heat provision; development stage specific crop water requirements, and coefficients of crop yield response to water stress. Agro-climatically attainable yields were calculated at crop/LUT level for three input levels (high, intermediate and low) and three water supply system types (rain-fed, rain-fed with water conservation, and irrigation.

Apart from providing estimates of agro-climatically attainable crop yields the model provides information on the climate-related constraints affecting crop yields. These constraints include temperature constraints, moisture constraints, and yield constraints due to pests, diseases and workability. Crop water deficits (rain-fed conditions) or crop irrigation water requirements (irrigated conditions) are provided as model output.

The results of the biomass and yield calculation depend on timing of the crop growth cycle (crop calendar). For each grid-cell the starting and ending dates of each crop/LUT growth cycle are determined optimally to obtain best possible crop yields, separately for rain-fed and irrigated conditions. This procedure also guarantees adaptation in simulations with year-by-year historical weather conditions and allows major crop calendar shifts and adaptations under climate distortions applied in accordance with various climate change scenarios.

Adequate agricultural exploitation of the climatic potentials and maintenance of land productivity largely depend on soil fertility and the management of soils on an ecologically sustained basis. Soil fertility is concerned with the ability of the soil to retain and supply nutrients and water in order to enable crops to maximally utilize the climatic resources of a given location. The fertility of a soil is determined by both its physical and chemical properties. An understanding of these factors and insight in their interrelations is essential for the effective utilization of climate, terrain and crop resources for optimum use and production. From the basic soil requirements of crops, a number of soil characteristics have been established related to crop yield. For most crops and cultivars, optimal, sub-optimal, marginal and unsuitable levels of these soil characteristics are known and have been quantified. Beyond critical ranges, crops cannot be expected to yield satisfactorily unless special precautionary management measures are taken. Soil suitability classifications are based on knowledge of crop requirements, of prevailing soil conditions, and of applied soil management. In other words, soil suitability procedures quantify to what extent soil conditions match crop requirements under defined input and management circumstances. The agro-ecological suitability and productivity are presented for four input levels (high, intermediate, low and mixed), five water supply system types (rain-fed, rain-fed with water conservation, gravity irrigation, sprinkler irrigation and drip irrigation), at crop level (49 crops) for baseline climate (1961-1990) and future climate conditions. In addition comprehensive crop summary tables by administrative units are available for viewing and download.