Model analysis of a straw mulch system for continuous wheat in an arid climate

Wheat (Triticum aestivum L.) production in some dryland regions is severely limited by the cereal cyst nematode (Heterodera avenae Woll.). Conventional fallow management during a wet period has been shown to allow hatching of the cysts during the fallow season and thereby sanitize the soil for the subsequent wheat crop. Recently a straw mulch (SM) management has been introduced into a long-term experiment in the Negev region of Israel. This management ameliorated the nematode damage and allowed continuous wheat production. Only three seasons of successful experimentation exist with the SM system so questions remain about its performance over seasons with differing weather conditions. A simple, mechanistic, wheat model was extended to simulate wheat development and growth when the crop is grown on nematode-infested soils. Incorporating statements describing inhibition of rooting depth as a result of nematode activity resulted in good agreement between simulations and 16 seasons of yield observations on continuous wheat. The effect of SM was simulated simply by decreasing soil evaporation and this resulted in higher levels of soil water and decreased nematode inhibition of rooting. Good agreement was obtained between the three seasons of experimental data and simulations of the SM system, with predicted grain yield within 10% of observations. Over 16 seasons, simulations of the SM system indicated substantial grain yield increases over continuous wheat in all but the highest-yielding season. Simulations in 14 seasons with conventional fallow management revealed that annual yields of SM were equivalent to biennial yields of the fallow system, resulting in a predicted doubling of wheat production for this dryland region of the Negev.