Effect On Nitrogen Use Efficiency And Ammonia Volatilization Of Cotton (Gossypium Hirsutum L.) By Different Nitrogen Applicatons

In the study, local cultivars KC-6 was chosed as test mertierals.The field experiments were carried out in 2008 and 2009 at application levels 0,150,300,450,600 kg N-ha-1 in Dongtai, Jiangsu Province (120°19'E,32°52'N). The study was focused on:(1) Effect on the yield and fiber quality of different fruiting-branch position of cotton by nitrogen applications; (2) Effect on parameters of biomass, N accumulation of cotton different organs by nitrogen applications; (3) Effect on nitrogen use efficiency on different organs of cotton by nitrogen applications; (4) Effect on ammonia volatilization of cotton and cotton soil a at florescence by nitrogen applications. The main results were as follows:1. effect on yield and fiber quality of fruiting-branch position of cotton by nitrogen applicationsYield (include different fruiting-branch position yield) increased first and then downed with nitrogen application increased, and the yield at 300 kg N·ha-1 is the biggest. The ball weight and lint percentage at 300 kg N·ha-1 are the biggest, the ball weight and lint percentage of the different fruiting-branch position at 300 kg N·ha-1 is the biggest. The fiber length increase with the fruiting branch position arise, and fiber length of 150,300 kg N·ha-1 was longest. Micronaire of different fruiting branch positions all belonged to the B2 level, which at 300,600 kg N·ha-1 was slightly higher than at 150,450 kg N·ha-1. The difference of fiber uniformity at different nitrogen applications was small, the uniformity at 300 kg N-ha-1 was slightly high. Obviously, the field and fiber quality of upper, middle and lower space fruiting branch positions was coordinated by 300 kg N·ha-1 and the field and fiber quality at 300 kg N·ha-1 was advantageous.2. Effect on parameters of biomass, N accumulation of cotton by nitrogen applicationsDynamic biomass and N accumulation of different organs of cotton (leaves, stem and branch, reproductive organ, over-ground of cotton) followed the S shape curve. The appearing time of the maximal accumulation rate was earliest, and the duration of speed accumulation was longest on biomass and N accumulation of leaves, stem and branch at 300 kg N-ha-1, and dry matter and nitrogen vegetable accumulate transport reproductive organs in good time and forming high reproductive organs. Excess nitrogen supply (600 kg N-ha-1) result as excess nitrogen accumulation of leaves, stem and branch, beginning time of fast accumulation period is latest and the duration of speed accumulation is shortened on biomass and N accumulation of leaves, stem and branch at 600 kg N·ha-1, and the nitrogen vegetable accumulates incapability transported production organ in good time. Deficient nitrogen supply caused scarcity nitrogen accumulation of the leaves, stem and branch at 0, 150 kg N-ha-1, which nitrogen accumulation cannot the demand of generative growth and to restrict growth of reproductive organ.3. Effect on nitrogen use efficiency by nitrogen applicationsTheoretic maximum accumulation, the average rate, the maximal accumulation rate of nitrogen accumulation use efficiency of leaf, stem and branch, reproductive organ at 300 kg N·ha-1 are the biggest, and the beginning time of fast accumulation period, the duration of speed accumulation, appearing time of the maximal accumulation rate of 300 kg N-ha-1 is earlier, dynamic characteristic parameter of nitrogen accumulation of 300 kg N-ha-1 is the most coordinated, and the true nitrogen accumulation use efficiency at 300 kg N-ha-1 was 57.9%(the time of sampling was 16th Oct,2008),54.9%(the time of sampling was 24th Sept, 2009) was seriously higher the true nitrogen accumulation use efficiency 41.2%(2008), 33.8%(2009) at 150 kg N-ha-1. The time of peak value of instantaneous nitrogen use efficiency at 300 kg N-ha-1 is highest. The peak value of N apparent utilization, physiological efficiency and agriculture utilization is also highest. Super nitrogen (600 kg N·ha-1) and low nitrogen (0 kg N·ha-1) treatment neither conduct to efficient cotton nitrogen absorption nor utilization. In the climate region of the middle lower reaches of Yangtze River Valley, the optimal nitrogen applications is 300 kg N·ha-1, and the critical period of nitrogen management was around 60 d after budding.4. Effect on ammonia volatilization of the over-ground and soil of cotton at florescence by nitrogen applicationsWithin 24 hours at florescence by nitrogen applications, nitrogen volatilization appeared the phenomenon of high day and low night, the ammonia volatilization in the period 0:00-6:00 in the morning is lower than other period. The ammonia volatilization of every treatment begins to increase at 9:00 am. The maximum period of volatilization begins at 12:00～17:00. The day ammonia volatilization of cotton over-ground is increasing with the growth increased during 20 d by applied nitrogen at florescence, which begin to down after 21d. And the amount of volatilization increases with the increase of nitrogen. The ammonia volatilization of cotton soil is firstly gained to mount and decreased to low with the growth increased by applied nitrogen at florescence. The amount of volatilization increases with the increase of nitrogen, and the amount of volatilization at 600 kg N·ha-1 is maximum.