Effects Of Planting Population And Nitrogen On Cotton Biomass And Nitrogen Accumulation In The Cotton Extremely Early-Maturation Region In The Northeast China

Cotton is an important crop in our national economy. The cotton extremely early-maturation region in the Northeast China is one important base for early-season cotton breeding and planting. Optimizing of planting population and nitrogen application rate are two key ways to improve fiber yield and fiber quality. To determine the effects of planting population and nitrogen rates on accumulation and distribution of biomass and nitrogen for short-season cotton, field experiments with three nitrogen levels and different population were carried out in Liaoyang using two cotton cultivars Liaomian19and NuCTON33B as materials from2007to2009. Based on the critical N dilution model and the plant biomass accumulation model, the critical N accumulation model, the critical N demanding model, the N absorption model and the N diagnosis model were developed. And subsequently, plant nutrition status of the cotton in different population was diagnosed.1. Effects of planting population on cotton biomass and nitrogen accumulation in the cotton extremely early-maturation region in the northeast China.The dynamic of cotton plant biomass and nitrogen accumulation followed the "S" shape curve, and planting population variation might change the characters of the biomass and nitrogen accumulation progress, and subsequently influenced fiber yield and fiber quality. The beginning time or the ending time of the high speed accumulation stage for nitrogen was about10days earlier than that for the biomass. Fiber yield and fiber quality was the highest in the97500plant/hm2population for both the two cultivars, and reduction of fiber yield would be caused in excessive higher population though biomass and nitrogen accumulation would be increased. The results suggested that nitrogen was not synchro-accumulated with biomass in cotton plants, mass accumulation of plant biomass would started in condition that mass nitrogen had already been accumulated. Reproductive growth stage could be advanced by set fitting planting population, and the97500plant/hm2population setting could lead to higher fiber yield than that in the two other population conditions by advancing the reproductive growth stage in the cotton extremely early-maturation region.2. Effects of nitrogen application rates on biomass and nitrogen accumulation of cotton in the cotton extremely early-maturation region in the northeast China.The accumulated dynamic of biomass and nitrogen of cotton were described by logistic curve equation. The beginning time of speed accumulation for nitrogen was10-12days earlier than that for biomass. At nitrogen240kg·hm-2, the biomass and nitrogen accumulation amount were the highest, the eigenvalues of the dynamic accumulation model of cotton were the most harmonious, the nitrogen recovery rate was the highest, thus the lint yield was highest and the cotton fiber quality was the best. At nitrogen480kg·hm-2, the accumulation amount and rate of biomass and nitrogen decreased, the distributive indices of biomass in reproductive organ and lint yield reduced.3. Effect of nitrogen application rates and planting population on biomass, nitrogen accumulation and nitrogen fertilization recovery rate of cotton in the cotton extremely early-maturation region in the northeast China.The total dry matter and nitrogen uptake amount continuously increased with the progress of plant growth, and the general pattern of crop growth followed a sigmoid function of time. Plant densities and nitrogen application rate might change the characters of biomass and nitrogen accumulation progress, and subsequently influenced fiber yield and fiber quality. The beginning times of speed accumulation period for nitrogen were about13days earlier than that for dry matter in all treatments. The eigenvalues of the dynamic accumulation model in the treatment of97500plant·hm-2×240kg/hm2were more harmonious than that of other treatments. Earlier beginning time of speed accumulation period is in favor of accumulating biomass and nitrogen, and higher yield.4. Effect of nitrogen application rates and planting population on biomass, nitrogen accumulation and nitrogen fertilization recovery rate in cotton boll in the cotton extremely early-maturation region in the northeast China.The characters of accumulation and distribution of biomass and nitrogen were influenced by population and nitrogen rates of cotton. The biggest biomass of cotton boll, cotton seed and cotton fiber were based on the following,(1) The earlier time when speed biomass or nitrogen accumulation started (t1), the earlier time when speed biomass or nitrogen accumulation terminated (t2), the earlier time when the rate of speed biomass or nitrogen accumulation reached the maximum (tm), the shorter duration of the rapid biomass or nitrogen accumulation period (T, T=t2-ti) and the higher maximal rate of speed biomass or nitrogen accumuation (Vm).(2) There was a similar regularity in eigenvalue for accumulation between nitrogen and biomass.(3) The distribution indices in cotton shell were the lowest in cotton seed and the highest in cotton fiber. Higher biomass accumulation of fiber was positively correlating to higher fiber quality. So we could try to improve fiber quality by altering the emergence time of t1, t2, tm and Vm to improve biomass accumulation. Based on the results of this study, we recommended that97500plant/hm2×240kg/hm2treatment was the best application in the cotton extremely early-maturation region.5. Development and application of critical nitrogen concentration dilution model for cotton grown in the cotton extremely early-maturation region in the northeast China. The relationship between the shoot dry matter and critical N concentration can be described by power equation. The difference of the coefficients a and b between the two genotype showed that, the NuCOTN plant had a higher capacity of N accumulation in shoot biomass than that of Liaomian19. The coefficients a increased with the increasing plant population also showed that the cotton plant in higher plant population had a higher capacity of N accumulation in shoot biomass than that in lower ones. The different estimate of b in the critical dilution curve indicates that genotypes and plant population affect the slope of the critical N dilution curve. Based on the critical N dilution model and the allometric relationships between N uptake and dry matter accumulation in shoot, the model for N nutrition index (NNI) and the model for N demand at different growth stages for potential growth and yield were developed. According to the allometric growth coefficient, NNI and N accumulation rate under critical N concentration, it could be conclude that the optimal rate of N application in97500plant/hm2should be lower than that in75000and120000plant·hm-2, and240kg/hm2was the optimal N application rate in97500plant/hm2in the cotton extremely early maturity in the northeast china.