Evaluation of Wheat Yield and Weed Biomass under Planting Patterns and Irrigation Regimes

Both planting pattern (with changes in canopy structure) and soil water availability (which affects growth and development) exert a strong effect on crop-weed competitiveness. Therefore, the effect of different planting patterns on the wheat yield and weed biomasses under different irrigation conditions were evaluated. The experimental design was a split plot with three replications, with irrigation treatments as the main plot, and planting pattern as the sub plot. Main plots included three irrigation regimes: normal irrigation, deficit irrigation (irrigation after planting and in start of flowering) and rainfed. Subplots were four planting patterns (three rows of wheat on the ridge, three rows of wheat inside the furrow, one row on the ridge and one row inside the furrow). The results showed that wheat grain yield significantly affected by both irrigation treatments and planting pattern. In irrigated condition, using the pattern of three rows on the ridges resulted in higher wheat grain yield (3437.8 kg.ha-1), while in the deficit irrigation and rainfed condition, the pattern of “one row inside furrow” had greater grain yield, whereas the average grain yields were 2574.3 and 1868.2 kg.ha-1 , respectively. Results also showed that, weed biomasses were the lowest in one row inside furrow pattern in all irrigation treatments. However, lowest weed biomasses on the ridges obtained in the “one row inside furrow pattern” at irrigation and rainfed condition and in the “three rows on the ridges pattern” at deficit irrigation. Average over all irrigation treatments, the “one row inside the furrow pattern” decreased weed biomass by 67.4, 14.9 and 60% compared with three rows inside the furrow, three rows one the ridge and one row on the ridge patterns, respectively.