Assessing the productivity of wheat genotypes in a Mediterranean climate, using a crop-simulation model

Abstract

A locally developed and validated crop-growth model for wheat, SIMTAG, using historic daily weather data, was used to simulate wheat crops at four locations in northern Syria. The chosen sites have a Mediterranean climate with an average annual rainfall between 280 and 480 mm (cv 35–28%). The analysis examined the effects on crop productivity of manipulating crop genotype (early, medium or late-maturing) or management (sowing date, fallowing, sowing rate). Cumulative frequency distributions of grain-yield, and dates of germination, anthesis and maturity, were derived from the simulation results and were used to discriminate between alternative choices. Means of simulated crop growth, water use, rooting depth and wetting depth were used to illustrate aspects of wheat production in this highly variable climate. Sowing close to the break of season showed a definite yield advantage at all sites, with simulated yield reductions of 4.2% per 1-week delay in germination. Average grain-yields increased from 217 g m −2 ( CV 53%) at the driest site to 471 g m −2 ( CV 48%) at the wettest site. Optimum anthesis dates were identified for each location, with an average yield reduction of 3–9% per 1-week delay in anthesis. Environmental pressure on wheat production in the area is high, as is shown by average simulated water-stress-free periods finishing 3 weeks prior to the optimum anthesis date at the driest site, and around anthesis at the wettest site. It was concluded that an early-maturing cultivar was most appropriate for the driest site and a medium-late-season cultivar for the wettest site, with medium-early cultivars for the intermediate sites. The simulated output was judged to be a realistic representation of the studied crop system. The wheat model SIMTAG can therefore be recommended for use in similar climates.