Research Of Nitrogen Nutrition Diagnosis Technology On Cotton

Cotton plant nitrogen diagnosis and nitrogen fertilizer recommendation with rapid nitrate testing tecnology, which combined with digital image analysis method, were studied in the field under border irrigation in southern Xinjiang. Nitrate concentration of the 4th expanding leaf petioles were measured by the Reflectance Meter. Based on these comprehensive experiments, a simple recommendation system had been established, which can be easily spread and suitable for agricultural advisors and farmers in southern Xinjiang. The possibility of using digital image analysis method for plant N status diagnosis was studied, and available color index for N status diagnosis were filtered to assess plant nutrition. The main results are as follows:Results showed that: different N rate applied could make different effects on cotton yield and the partial factors consisting many organs kinds under border condition in southern Xinjiang. Among all of that, the ginned cotton and the lint cotton yield were increased when the N rate applied were between 0 300 kg/hm². Factors mentioned wouldn't increase until N rate applied exceed 300 kg/hm².Along with increase of nitrogen fertilizer application, the biomass and N rate of above-ground plant parts of cotton (leaf, stem, bud, flower, boll) also increased to some extent. Trends of biomass accumulation in different treatments were the same and N rate of every cotton organs showed decreasing trend through the growth development.In condition of border irrigation, NO3" concentration in the 4th expanding petiole between stage of flowering period and full boll period were significantly correlated with N rates applied and lint cotton yield. The critical value of NO₃^- concentration were 10463 mg/L and 6901mg/L separately as nitrogen diagnostic index of two of the main growth stage. The reasonable amount of nitrogen needed for getting the economical lint yield of 2420kg/hm² was 304 kg N/hm². Based on the good relationship above, a cotton nitrogen fertilizer recommendation model was established. Then, the rate of nitrogen topdressing could be recommended according to the recommendation model.The digital processing technique could be used in cotton N diagnosis under border irrigation. Results showed that: four green index [G/(R+G+B), G/L,G/R , G/B] of cotton plant canopy were much better than other color parameters because of its better correlation with nitrate concentration in bud stage. The plant canopy indexes including G, R/(R+G+B),B/(R+G+B) and G/R, which obtained from digital image analysis, were good correlated with partial common plant nutrition index and they could be suitable indicators for N status diagnosis through the growth stages.Field digital image analysis method combined with soil and plant rapid test could be used for N fertilization recommendation. In this field experiment, when G/R was less than 1.15, cotton plant was in serious N stress state at boll stage; when G/R was 1.150-l.160, cotton was in N stress state, and the plant need more N topdressing; when G/R was 1.160—1.180, cotton plant was in optimum N stress supply state. When N rate reached 300kg. hm^-2 and G/R was less than 1.155, cotton plant was in serious N surplus state, did not need more N topdressing at boll stage.