Tillage and deficit irrigation strategies to improve winter wheat production through regulating root development under simulated rainfall conditions

Knowledge of rooting systems and soil water status across rooting zones is important for stabilizing agricultural productivity in the semi-arid regions of China. In the present study, a mobile rainproof shelter trial was performed to find out the effects of cultivation mode on the temporal and spatial root growth distribution, soil water content, root respiration rate, and grain yield during 2015-2016 and 2016-2017 growing seasons. The two cultivation modes were: (1) the ridge furrow (RF) rainfall harvesting technique; and (2) traditional flat planting (TF). In addition, three simulated rainfall (1: 275, 2: 200, 3: 125 mm) and two deficit irrigation (150, 75 mm) levels were used. Our results showed that different cultivation modes with simulated precipitation levels significantly improved moisture content for wheat growth, improved root growth, and provided favourable conditions for higher wheat production. The RF150 treatment with 200 mm rainfall significantly increased morphology of the wheat rooting system, especially in the top 40 cm soil layer compared with TF cultivation. The RF150 treatment significantly increased root dry weight (47%), root tissue density (6.7%), root fineness (4.8%), root length ratio (20.3%), root mass ratio (27.3%), and grain yield (18.9%) of wheat at 200 mm rainfall than that of TF2150 treatment. Root weight density, root length density, root surface area density, and root diameter were significantly higher under RF150 treatment with 200 mm and 275 mm precipitation in the 40 cm soil layer and reached maximum values at the flowering stage. The root dry weight, root respiration rate, and grain yield were significantly improved under RF2150 treatment, but there were no significant differences when the rainwater increased from 200 to 275 mm under both cultivation modes. Therefore, we suggested that the RF2150 treatment is a suitable water saving strategy to improve temporal and spatial root growth distribution, resulting in higher grain yield in a dry-land farming system.