Effect Of Once Fertilization Time On Cotton Yield And Nutrients Accumulation

Cotton is conventionally fertilized with three splits at preplant (PPA,30%N,100%P and K), first bloom (FBA,40%N) and peak bloom (PBA,30%N) stages in the Yangtze River Valley China, but multiple times of fertilization are becoming increasingly more costly. It was very significant to apply once fertilization time at flowering and boll setting stages without yield sacrifice. The objective of this study was to determine the effect of one-time fertilization of N with225kg/hm2at flowering and boll setting stages through making comparisons with yield and its components, biomass accumulation and chlorophyll content, nutrients absorption and distribution, fertilizer N utilization rate. Field and pot experiments were conducted with five treatments (FT1=0DAF (days after bloom); FT2=5DAF; FT3=10DAF; FT4=15DAF; FT5=20DAF; FT6, conventional three splits control (prelant fertilization(30%N,100%the rest of fertilization), fist bloom fertilization(40%N), peak bloom fertilization(30%N)) in2012and2013. The results were that:1Effects on cotton growth processCotton growing period was nearly not affected by N one-time application in the field and pot trials. Howere, in pot trial, the seedling and the flowering period was shortened and the squaring period was extended, so the total growth period was made to be shorter than field trial’s. In two years, seedling was not affected by N one-time application, but compared to control treatment, once application time made cotton plant squaring earlier, flowering later, opening earlier.2Effect on cotton yield and its component factorsFT1produced similar cotton yield to the conventional fertilization. That is easy to say, fixing the fertilizer rate, fertilization once produced the same (economic) yield as fertilization thrice did. Economic yield difference was derived from boll number per unit ground area, and significant difference among lint weight and lint percentage.3Effect on dry matter accumulation of cotton plantCotton plant biomass (CPB) had same trendy with cotton yield, and total plant, vegetative organs and reproductive organs accumulation accumulation process could be described by a logistic function. FT1had the similar amount of total plant, vegetative organs and reproductive organs accumulation to FT6treatment, higher than the rest. During FAP(fast accumulation period), FT1had the shortest lasting period and the highest accumulation rate, FT6was the second.4Effect on nutrient absorption on cotton plantOne-time application didn’t change the basic regulation of N、P、K uptaking and distribution in cotton. These three elements uptake regulation were similar, K>N>P. The amount decreased with application timing extending, FT6(CK) was lower than FT1, the rest decresed with development. Flowering stage was fastest, but it was slow before flowering and after opening, according to logistic formula.Pot trial had a high density of75,000plant/ha, which limited group biomass growing by space and nutrients, so single plant won’t get high plant biomass. Nitrogen partial productivity increased with application timing extending, FT6(CK) was medium Nitrogen biomass efficiency index, Nitrogen yield efficiency index increased initially and decreased later, Nitrogen demand coefficient was opposie. Fertilizer N utilization efficient is higher in FT6, highest in first flowering fertilizer and lowest in pre-plant fertilizer.5Effect on nitrogen distribution in cotton plantCotton absorbed nitrogen from the soil as the main nitrogen source during squaring period, and the whole plant accumulated the average amount of N from soil nitrogen, which was much larger than the nitrogen from fertilizer. Early flowering stage to boll opening, cotton growth and development based mainly on reproductive organs, the content and distribution percentage of fertilizer nitrogen and soil nitrogen in various organs of the cotton on early flowering were:squares and flowers>leaves> fruit branches> roots and stem. Squaring period had low nitrogen use efficiency, increased gradually after the early flowering stage, boll opening for maximum utilization of nitrogen fertilizer.