The Study Of Relationship Between SPAD Values And Soil N And Plant N Content About Nondestructive Diagnosis Of Cotton N

Mulched-cotton by drip irrigation technology has been considerable development in Xinjiang, The key issue of cotton fertilization is that how to timely and appropriate application of nitrogen fertilizer, the technology of SPAD non-destructive, fast diagnosis fertilization was used progressively widely, but the technology's accuracy has to be improved. This choice in typical arid area in Xinjiang Korla cotton cultivation, conducted a 2-year field experiment, drip irrigation of cotton in the same total amount of fertilizer, studies on the effects of in different growth stage the different top dressing nitrogen fertilization strategy on soil nitrogen, plant total nitrogen, yield, SPAD value. Determine the number of samples for improve the accuracy of the SPAD value, and offer a reference for improving nondestructive diagnosis technology and nitrogen fertilizer use efficiency. The main conclusions are as follows:(1) When nitrogen fertilizer was supplied relatively adequate, SPAD value of the cotton from bud stage keep on a high level to full-boll stage. In boll opening stage, the SPAD value begin to decline slowly, SPAD value maintaining a high level throughout the growth stage, the overall high yield of cotton is available. Therefore, the appropriate choice of the total nitrogen can increase effectively the yield in which cotton growing stage using fine fertilization strategy.(2) No matter the level of fertilization is high or low, in 0-60cm soil section, under the strategy of different nitrogen topdressing rate,0-20cm,20-40cm,40-60cm layer, the soil available nitrogen content of each layer is significant difference, the soil available nitrogen showed increase in gradient with the increase of the depth section. Available nitrogen content in soil is not the same within the same section depth under different N application strategies. According to the proportion of recommended fertilization which pattern of requirement of fertilizer of cotton in growth stage apply fertilizer, between the SPAD value and soil available N have the highest relativity in growth stage. Under the different fertilization strategies,in cotton growing SPAD value reflects the sensitivity that the level of available nitrogen in the soil have difference.(3) Whether the nitrogen is relatively low or high, According to the proportion of recommended fertilization which pattern of requirement of fertilizer of cotton apply N, between the content of available nitrogen that within 0-20cm soil section rage and SPAD value have the highest relativity, followed by the soil section 40-60cm rage, the lowest relativity is the range 0-20cm soil section. The choice of soil available nitrogen value within soil section 20-40cm can improve that the SPAD values reflect soil nitrogen levels.(4) Under the same nitrogen, the different strategies of nitrogen topdressing rate can produce significant effect which on cotton absorb nitrogen and accumulate nitrogen, and single boll's weight, resulting in the accumulation of nitrogen and increasing yield of cotton play same role. Fertilization twice with "behind the front less" application of N fertilizer can improve nitrogen accumulation rate in early flowering and boll opening of the cotton, can meet the cotton stem absorbs nitrogen adequately in the early flowing, and improve the percentage of N accumulation in the total N accumulation in initial boll opening, to coordinate the nitrogen accumulation rate reached its highest level whole growth stage is conducive to form the high yield.(5) Under the same nitrogen, different strategies of nitrogen topdressing produced varying degrees effect on related level which of between aerial part of cotton plant and SPAD value, and related level which of between nitrogen uptake of leaves and SPAD value. And the related level which of between nitrogen uptake of leaves and SPAD value are higher than the related level which of between aerial part of cotton plant and SPAD value. Under the different strategies of nitrogen topdressing, the rule of relativity which of between aerial part of cotton plant and SPAD value is the same as the rule of relativity which of between nitrogen uptake of leaves and SPAD value. The sensitivity that SPAD value reflects the level of leaves nitrogen is higher than the sensitivity of plants.(6) When using the SPAD chlorophyll measured In each growth stage of cotton, number of samples affected the precision of using SPAD value, the more number of sample is, the better precision is, and the relativity which of between the SPAD value and content of leaves is better, SPAD value measured the number of samples and standard deviation as a power function.