Dual-purpose winter wheat: interactions between crop management, availability of nitrogen and weather conditions

Abstract Dual-purpose wheat has been adopted in many farming systems, but interactions between management, supply of resources, and seasonal conditions are still not clearly elucidated. Two experiments were established in the Loess Plateau of China to measure yield and its components, evapotranspiration, water-use efficiency(yield per unit evapotranspiration), accumulation and apparent remobilisation of stem water soluble carbohydrates (WSC), and economic benefit of dual-purpose winter wheat. Experiment 1 combined factorially three defoliationtreatments, i.e. winter defoliation(DC23), spring defoliation(DC29) and untreated control, two seeding rates (currently recommended, and 125% recommended), and over four seasons. Experiment 2 combined factorially two defoliationtreatments (spring defoliationand control), two nitrogen rates (low: 120–150 kg N ha−1, high: 180–200 kg N ha−1), three levels of soil waterat sowing (low: rainfed; medium: rain +67 mm; high: rain +133 mm), and over three seasons. Defoliationwas largely neutral for grain yield and water-use efficiency, and improved translocation of WSC to grain by 8%, harvest index by 7% and net income by 15% across conditions. Grain yield was unaffected by the interaction between defoliationand seeding rate, but significantly impacted by interactions of defoliation × initial soil waterlevel and defoliation × nitrogen rate. Defoliatedwheat yield was greater at high than at medium and low initial soil watercontent, and at low than at high nitrogen rate. Spring defoliationproduced similar yield as winter defoliationbut the former increased forage income. Increasing seeding rate or nitrogen rate increased forage income but reduced net income due to lower grain income and higher cost. Thus, dual-purpose winter wheat was more profitable (i) when defoliatedin spring, (ii) at the lower seeding density, (iii) under the lower nitrogen rate, and (iv) with higher soil watercontent at sowing. Apparent translocation of stem WSC partially mediated the effect of defoliationon grain yield. It is concluded that dual-purpose winter wheat is feasible under straw mulching in semiarid environment.