Effects of potassium on physiological characteristics, yield and quality of spring wheat

Spring wheat is one of the main grain crops in Heilongjiang province of China. The annual planted area is about 0.2 million hectares. The yield and quality of the spring wheat in the province is below the medium level in the country. So it is an urgent problem to enhance the yield and the quality. Potassium is not only the essential nutrient for crops growth and development, but also an important element in quality formation. The aim of the paper is to study the effect of potassium on the physical characteristics, yield and quality of spring wheat, and to provide technical support for high yield and high quality and high efficiency fertilization for wheat production in Heilongjiang province. The methods of pot culture and field experiment were adopted to study the effect of potassium on the physiological characteristics, yield and quality of the spring wheat. There were 5 treatments for the pot culture experiment and the rate of potassium (K2O) was 0, 0.05, 0.10, 0.20, 0.50 g/kg. The samples of the second leaf from the top of the wheat plants at the stages of three-leaf and jointing and the samples of the flag leaf at the stages of blooming, filling and maturing were collected for the determination of chlorophyll content, photosynthesis rate and the activity of nitrate reductase. The result of pot experiment showed that potassium could increase the chlorophyll content in the leaves. With potassium application, the chlorophyll content in the leaves increased by 0.51, 0.37, 0.75, 0.55 and 0.28 mg/g from three-leaf stage to maturing stage respectively compared to the control, on average. Among these, the optimum rate for the increase of chlorophyll content was K2O 0.10g/kg. With potassium application the rate of photosynthesis increased by 0.44, 1.87, 2.11and 1.49 mol/(m2s)from jointing stage to maturing stage respectively compared to the control, on average. Among these treatments, the optimum rate of potassium for photosynthesis was K2O 0.20g/kg. Potassium also showed a good effect on the activity of nitrate reductase of the spring wheat. With potassium application the nitrate reductase activity(NRA) increased by NO2- 17.7, 17.6, 21.9, 23.9 and 13.5 g/(gh),FW from three-leaf stage to maturing stage respectively compared to the control, on average. Among these treatments, the optimum rate of potassium for NRA was K2O 0.20g/kg.The field experiments were conducted in the main region of spring wheat production in Heilongjiang province. The soils for the experiments were black soil and planosol. There were 5 treatments with 3 replications. The rate of potassium was (K2O): 0, 22.5, 37.5, 52.5 and 82.5 kg/ha. The experimental result showed that potassium had a significant effect on the yield and quality of spring wheat. On the view point of yield and quality, the optimum rate of potassium for wheat in Heilongjiang province was K2O 37.5-52.5 kg/ha, the yield increased by 3.8%-18.1%, the average was 9.9%. Appropriate rate potassium application could improve wheat quality, especially on the processing quality. Compared the treatments of potassium with control, the protein content increased by 0.36 percent, wet gluten content by 2.33 percent, sedimentation value by 3.07mL, time of stability by 4.13 min, the maximum resistance by 10.2 EU, the extensibility by 1.4cm and the bread volume increased 10.4mL, on average. Potassium application could affect the components of protein in wheat. Compared the treatments of potassium with control, aibumine content increased by 0.14 percent, globumine content by 0.13 percent, glutenine content by 0.39 percent and prolamine content decreased by 0.42 percent.