Effects of water, nitrogen and phosphorus coupling on starch paste properties of winter wheat

A field experiment was conducted under rain-shelter conditions in Luoyang (Henan Province) during the 2009—2010 and 2010—2011 cropping seasons by using “Luohan 2” winter wheat cultivar. The objective of the experiment was to evaluate the effects of irrigation and nitrogen/phosphorus fertilization on grain quality of winter wheat in the semiarid region of West Henan Province. The experiment was a factorial combination of 5 irrigation, nitrogen and phosphorus application rates, each in 3 replicas. The effects of water, nitrogen and phosphorus application rates and interactions on starch paste parameters of winter wheat were determined. The results showed that the application of nitrogen and phosphorus fertilizers had significant effects on starch paste properties of winter wheat (P≤0.05 or P≤0.01). Main starch viscosity parameters (peak viscosity, initial viscosity and final viscosity) increased significantly as nitrogen application increased from 0 kg·hm^-2 to 105 kg·hm^-2, and after peaking at 105 kg·hm^-2 decreased with nitrogen application rate. Starch viscosity parameters reached the highest values at phosphorus application rate of 168 kg·hm^-2. Irrigation had no significant effect on starch paste properties. However, irrigation and nitrogen interactions significantly influenced some starch paste properties. Overall, combined treatments of nitrogen, phosphorus and water at N105P168W217.5 — i.e., 105 kg(N)·hm^-2, 168 kg(P₂O_{5-2 and 217.5 mm irrigation — produced the best starch quality. Statistical analysis indicated a significant positive correlation between starch paste properties and grain yield in the 2009—2010 cropping season and not in the 2010—2011 crop season. This suggested that there existed the possibility for improvement of both grain yield and starch paste quality in the region.}