| The experiment was conducted with the sandy loam of experimental farmland in Yangzhou University from 2007 to 2009. The soil had middle level fertility and the pre-planted crop was rice. The mid-gluten wheat Yangmai 16 and the weak-gluten wheat Yangmai 15 were used to study effect of nitrogen application amount on grain yield, nitrogen absorption efficiency and soil available nutrients , and to seek the critical threshold of growth-related indexes.The results were summarized as followings:(1) The relationship between the output (y) and the nitrogen application rate(x) of the weak-gluten wheat Yangmai 15: y=-1.0127x2+30.537x+300.23.The optimumfertilizer rate was: x=14.9 kg/mu, the maximum yield was: y=530.5 kg/mu; The relationship between the output (y) and the nitrogen application rate(x) of the mid-gluten wheat Yangmai 16: y= -0.8652x2+24.579x+348.91.The optimum fertilizer rate was x=14.2 kg/mu, the maximum yield was: y=523.4 kg/mu.(2) The critical threshold of growth-related: When the optimum fertilizer rate (14.9 kg/mu) for the weak-gluten wheat Yangmai 15 was applied, the dry matter weight during the elongation stage was 328.47 kg/mu, the maturity was 1041.27 kg/mu. The tiller number instage winter, elongation, heading and maturity was 0.324, 0.707, 0.348 and 0.333 million/mu, respectively; When the optimum fertilizer rate (14.2 kg/mu) for the mid-gluten wheat Yangmai 16 was applied, the dry matter weight during the elongation stage was 613.5 kg/mu, the maturity was 1031.12 kg/mu. Tiller number at heading stage was 0.328 million/mu, while that in maturity was 0.322 million/mu. (3) The critical threshold of physiological indicators: When the optimum fertilizer rate for the weak-gluten wheat Yangmai 15 was x=14.9kg/mu, the SPAD value of flag leaf during the heading stage was 53.14, the nitrate reductase activity was 12.8ug/g/h; When the optimum fertilizer rate of the mid-gluten wheat Yangmai 16 was x=14.2kg/mu, the SPAD value of flag leaf during the heading stage was 56.01.(4) The critical threshold of N P K nutrients during maturity: When the optimum fertilizer rate for the weak-gluten wheat Yangmai 15 was x=14.9kg/mu, the absorption of nitrogen nutrient was 29.6kg/mu,the uptake of P was 4.8kg/mu, the requirement of K nutrient was 11.6kg/mu; When the optimum fertilizer of the mid-gluten wheat Yangmai 16 was x=14.2kg/mu, the absorption of nitrogen nutrient was 35.8kg/mu,the uptake of P was 5.5kg/mu,the requirement of K nutrient was 12.1kg/mu.(5) The critical threshold of N P K nutrients in plant vivo at different growth stages: When the optimum fertilizer rate of the weak-gluten wheat Yangmai 15 was x=14.9kg/mu,the nitrogen nutrient in vivo at heading stage was 18.3 kg/mu, the phosphorus nutrient in vivo at maturity was 4.8 kg/mu, the potassium nutrient in vivo at elongation stage was 13.9 kg/mu; When the optimum fertilizer rate of the mid-gluten wheat Yangmai 16 was x=14.2kg/mu, the nitrogen nutrient in vivo at elongation stage was 12.4 kg/mu, the phosphorus nutrient in vivo at maturity was 5.5 kg/mu, the potassium nutrient in vivo at elongation stage was 6.6 kg/mu;(6) The critical threshold of soil available nutrients: When the optimum fertilizer rate of the weak-gluten wheat Yangmai 15 was x=14.9kg/mu,the available potassium at heading stage was 78.96 mg/kg; When the optimum fertilizer rate of the mid-gluten wheat Yangmai 16 was x=14.2kg/mu,the available potassium at heading stage was 79.04 mg/kg. (7) the critical threshold of CaCl2 extracted soil nutrients: When the optimum fertilizer rate of the weak-gluten wheat Yangmai 15 was x=14.9kg/mu, the content of CaCl2-N at heading stage was 45.99 mg/kg, the content of CaCl2-K was 21.49 mg/kg; When the optimum fertilizer rate of the mid-gluten wheat Yangmai 16 was x=14.2kg/mu, the content of CaCl2-N at heading stage was 45.48 mg/kg, the content of CaCl2-K was 21.55 mg/kg.(8)Compared with soil available nutrients measured by routine methods, CaCl2 extracted soil nutrients were more closely related to the amount of N fertilizer rate and growth status of wheat plant. |
