Effects Of Different Nitrogen Ratio On Cotton

Hybrid Cotton (Gossypium hirsutum L. vs Huazamian H318) was used in both pot and field conditions with transplanting methods to make comprehensive evaluation of the effects of different proportion of nitrogen application under the condition of fixing the ratio of first bloom application for40%(labeled as4, the same is for the rest) and the remaining60%N was balanced between pre-plant and peak bloom as the treatments of this study:A,0:6; B,1:5; C,2:4; D,3:3; E,4:2; F,5:1. The nitrogen level was fixed (300kg/ha), and cotton growth, yield and its components, nutrient absorption and utilization, the impact of nitrogen use efficiency were studied. The results showed that:1. Growth periodCotton plants under higher proportion of nitrogen application before planting had earlier flowering and boll opening, but later budding. However, plants under lower proportion before planting performed inversely, and have longer period between flowering and boll opening.2. Agronomic traits, yield and its component factorsNitrogen had effects to raise plant height. Cotton plants under higher proportion of nitrogen application before planting increased fruit branch position and abscission, and there were no significant differences among6treatments. Treatment B had the highest yield of seed cotton (95.3g per plant) and lint, was6.3%-32.2%and15.6%-37.1%higher than other5treatments respectively. And also, treatment B had highest bolls per plant (27.5per plant) and lint percentage, which were both significantly different.3. Spatial and temporal distribution of cotton production and its component factorsOn the spatial distribution of cotton production, the boll number and weight in the lower part and inner side were higher, and lint percentage were lower in the higher part and external side, along with proportion of nitrogen application in peak bloom stage. On the temporal distribution of cotton production, the boll number and weight before autumn were higher; while the boll number and lint percentage of early autumn bolls increased along with proportion of nitrogen application in peak bloom stage.4. Physiological and biochemical characteristicsChlorophyll SPAD appeared fluctuating trend among6treatments, F>E>D>C>B>A within71DAE, B>A>C>D>E>F after71DAE. Soluble sugar content among different treatments had similar trends, rising in early period, reaching a peak (67DAE) then gradually decreased, higher82DAE, and F>E>D>A>C>B. So did the soluble protein content, with the trend B>C>A>D>E>F.5. Biomass accumulationThe biomass accumulation of cotton proceed slowly in all seedling growth stages, gradually accelerating in bud stages and reaching its peak between flowering to boll setting period, which met the plants "S" growth curve. The biomass accumulation of nutritive organs happened earlier, with the highest rate between65and104DAE; the biomass accumulation of reproductive organs happened later, with the highest rate between82and116DAE, The biomass accumulation of nutritive and reproductive and total organs showed that treatment A and B have the highest rate and the higher average of FAP, the days of appear and final are later, but the duration time are different.6. Nutrient assimilationThere was consistent curve for N, P, K accumulation, rising little in early period, reaching a peak in peak bloom stage and then gradually decreased in mature stage. The accumulation of N, P, K became higher with proportion of nitrogen application in peak bloom stage, and the trend was changed absolutely reversely. Treatment B had the highest values of N, P, K.N, K accumulation displayed distinctly among6treatments, with a similar trend with biomass accumulation. There was fast accumulation before nutritive stage, and lower increase after reproductive stage. The phosphorus accumulation increased with proportion of nitrogen application in bloom stage. And, there were no significant differences among6treatments in P, K accumulation.