Response Of Cotton Nitrogen Metabolism To Once Fertilization Time

According to the pattern of the reduction of severe cultivation for cotton production, we presented once fertilizer application under the combined condition of "delayed sowing date, direct seeding and high density", with the objective of investigating the effects of once fertilizer application time on cotton yield and yield components, to obtain the optimum time of once fertilizer application which is of no significantly difference to conventional fertilization in yield. To achieve the goal, conducted in the field of Hua Zhong Agricultural University located in the Yangtze River Valley was a two-year experiment of2012-2013for once fertilizer application assigned to6treatments including FT1(ODAF), FT2(5DAF), FT3(10DAF), FT4(15DAF), FT5(20DAF), and CK (conventional fertilization), with5days interval sequentially and respectively. Based on the breed of Hua Hybrid Ctton H318with field experiment, we devoted ourselves to exploring intensively alteration of the cotton biological characteristics, yield and yield components, and physiological biochemical characteristics (the content of nitrate nitrogen,nitrite nitrogen, free amio acid, soluble protein,soluble sugar and the activity of nitrate reductase) in respond to the time of once fertilizer application. Acquire the following achievements:1.Compared with CK, once fertilizer application under delayed sowing date and direct seeding could significantly shorten the growth period of cotton, mainly manifesting significantly shorte seedling and squarling period but non-significant constant boll setting period. Simultaneously, high density contributed significantly to improving proportion of inner bolls in cotton plant, which was attributed to shaping cotton liking cylindrical to diminish effectively cotton lateral growth.2.FT1and FT2were makedly superior to other treatments but comparable to CK in yield.3.A similar current exsited in gradual increasing cotton growth period based on the content of NO3--N in petiole and the activity of NR in leaf, with curve performancing that it increased to the peak primarily before declining. FT1with the content of NO3--N in petiole and the activity of NR in leaf was the highest in fisrt bloom while there was no significant difference among all treatments possessing the decreasing trend in peak bloom; at the same period, in comparison to main stem leaves with the content of NO3--N in petiole and the activity of NR, fruit branch leaves were greater in lower and middle parts of cotton but inferior in upside.4.It reflected the degree of metabolism in leaves through the variation of the content of NO2--N in cotton leaves.During the period from flowering to boll setting, the trend of NO2--N content was rising obviously following with the days after fertilizer. Primarily it was ascending that the content of NO2--N during5d-10d of the days after fertilizer; then it started to descend after10d. FT1was predominant to others on the10d after fertilizer. However, the content of NO2--N of the entire treatments was strikingly decreasing in common at peak bloom without distinction.5. From first bloom to peak bloom, it appeared that the whole treatments belonged to the identical trends in the factor that it increased initially before declining for soluble protein and free amino acid content. After peak bloom, it changed little. FT1and CK were the top two on soluble protein and free amino acid content during the first bloom and boll setting period.6.For soluble sugar content in main stem leaves, it increased initially before declining. As for branch leaves, the soluble sugar rised up from beginning to the end. Also FT1and CK were the top two on soluble sugar content during the first bloom period.To the sum, once fertilizer application time had important effect on the cotton production. FT1got the highest yield, probably because of the highest NO3--N content in petioles and highest NRA in leaves. The application time of FT1met with the N absorption peak. Also FT1got the highest soluble protein, free amino acid content by NO3--N transformed. To provide photosynthesis sufficient from structure leaf, it was the precondition for the formation of high yield.