Effects of soil water regulation at different growing stages on nitrogen uptake and utilization of spring wheat in the Hexi Region, Gansu Province

ObjectivesIn Hexi Region of Gansu Province, there is shortage of water resource, and the water and fertilizer use efficiencies of crops are low. The nitrogen uptake and utilization of spring wheat was studied, to find the effective regulation mode of soil water at different growing stages of spring wheat.

MethodsField experiments were carried out with the spring wheat cultivar of ‘Yongliang 4’ as materials at a nitrogen application rate of N 180 kg/hm². Five lower soil water supply treatments, recorded as W1, W2, W3, W4 and CK (sufficient irrigation) were set up at the four growing stages of spring wheat. The accumulation, distribution and translocation of nitrogen in spring wheat were determined, and the rhizosphere soil NO₃^–-N contents were analyzed at the same time.

Results1) When the low soil water limit became high, the irrigation amount of spring wheat would be increased, and the increment in CK was significantly higher than in W1, W2, W3 and W4 treatments, with the corresponding increase of 26.6%, 15.0%, 9.3% and 4.8%, respectively. 2) Increased irrigation promoted the soil nutrient assimilation by wheat plants. Compared with W4 treatment, the nitrogen assimilation of wheat was significantly reduced by 29.3%, 23.0% and 15.5% in the W1, W2 and W3 treatments, respectively, while the difference was not significant between the W4 and CK. 3) Compared with the W1, W2, W3 and W4 treatments, the nitrogen assimilation in vegetative organs of the CK treatment at the maturity was increased by 28.2%, 28.6%, 19.2% and 12.7%, respectively, while the grain nitrogen assimilation of the CK treatment was significantly reduced by 10.4% compared with the W4 treatment. The W4 had the highest nitrogen translocation amount and efficiency except for its decreasing contribution proportion (76.2%). Compared with the W1, W2, W3 and CK treatments, the nitrogen translocation amount and efficiency were increased by 40.4%, 28.0%, 10.6%, 10.0% and 6.8%, 3.5%, 1.3%, 6.9%, respectively. With the increase of lower soil water limits, the nitrogen uptake efficiencies, nitrogen productive efficiencies and nitrogen harvest indices in all treatments increased first and then decreased, while the W4 had the most obvious changing trend. 4) At the same fertilizer level, the increase in irrigation amount increased the movement of the soil NO₃^–-N into deep soil, which was not good for wheat plants to absorb soil NO₃^–-N. 5) The soil water regulation at different growing stages had significant effects on soil NO₃^–-N contents. At the maturity stage, the treatment W4 showed the lowest soil NO₃^–-N accumulation in the 0–100 cm soil layer, which was reduced by 9.6%, 7.2%, 6.6% and 1.4%, respectively, compared with those of the W1, W2, W3 and CK treatments.

ConclusionsThe appropriate soil water regulation is beneficial to the soil nutrient uptake by spring wheat plants. Comprehensively considering the nitrogen accumulation, distribution, and soil NO₃^–-N contents, the treatment W4 is selected as the optimal mode for spring wheat in the Hexi Region under present experimental conditions.