Study On The Spatial And Temporal Variability Of Available Nutrient In Cotton (Gossypium Hirsutum L.) Field And Biomass Accumulation Of Cotton At Flower And Boll Stage

Flower and boll stage is a key period for lint yield and fiber quality of cotton(Gossypium hirsutum L.).In this study,we chose Nucotn 33B.The field experiments were carried out in 2004 at application levels of 0,120,240,360 and 480 kg N·hm^-2 in the typical representatives for ecological regions in China,Yellow River Valley(36.1°N,114.2°E, Anyang) and the middle lower reaches of Yangtze River Valley(32.0°N,118.5°E,Nanjing). The study focused on:(1) Effect of spatial and temporal variability of available nutrient in cotton field at flower and boll stage on lint yield and fiber quality;(2) Effect of different nitrogen application levels on spatial and temporal variability of biomass accumulation of cotton at flower and boll stage;(3) Effect of spatial and temporal variability of available nutrient in cotton field on spatial and temporal variability of biomass accumulation of cotton at flower and boll stage.The main results were as follows:1.Effect of spatial and temporal variability of available nutrient in cotton field at flower and boll stage on lint yield and fiber quality.In the process of growth,the content of soil alkali-hydrolyzable nitrogen in 0-60 cm soil layers of 0 kg N·hm^-2 treatment presented the trend of decreasing firstly and increasing then. While that of other treatments decreased firstly,increased after topdressing,decreased again, and increased after the beginning of boll opening.Soil available phosphorus and available potassium in 0-60 cm soil layers at two experimental locations presented the similar trends of decreasing firstly and increasing then.Soil available nutrients in 0-60 cm soil layers decreased with the deepening of the layer.Soil alkali-hydrolyzable nitrogen and available phosphorus had no significant variation of 0 kg N·hm^-2 treatment,in the same soil layer of other treatments in Nanjing presented the similar decreasing as the horizontal distance to cotton plant increased.The spatial and temporal variability for soil alkali-hydrolyzable nitrogen was more significant in Nanjing than in Anyang.While for soil available phosphorus,it was more significant in Anyang than in Nanjing.Soil available potassium in 0-60cm soil layers in Nanjing and in 20-60 cm soil layers in Anyang presented the similar decreasing with the increasing of horizontal distance to cotton plant,while that in 0-20cm soil layers in Anyang was increased.As a result,at the nitrogen application level of 360 kg N·hm^-2 for Anyang and 240 kg N·hm^-2 for Nanjing,yield components were relative optimal, yield was the maximum and the fiber quality of length and strength was better.2.Effect of different nitrogen application levels on spatial and temporal variability of biomass accumulation of cotton at flower and boll stage.Temporal variability of vegetative organs,reproductive organs and biomass accumulation of different fruit branch positions of cotton plant could be described by Logistic equation in Nanjing and Anyang.But the spatial variability of biomass accumulation of vegetative organs,reproductive organs and biomass accumulation of different fruit branch positions of cotton plant was different.Earlier starting date of speed accumulation period,shorter duration of speed accumulation and maximal speed were the characteristic at the nitrogen application level of 360 kg N·hm^-2 for Anyang and 240 kg N·hm^-2 for Nanjing.At the nitrogen application level of 360 kg N·hm^-2 for Anyang and 240 kg N·hm^-2 for Nanjing,yield components were relative optimal,yield were the maximum and the fiber quality of length and strength was better.3.Effect of spatial and temporal variability of available nutrient in cotton field on spatial and temporal variability of biomass accumulation of cotton at flower and boll stage.Soil available nutrient(soil alkali-hydrolysable nitrogen,available phosphorus and available potassium) in cotton field in Nanjing and Anyang had significant spatial and temporal variability.The variability significantly affected biomass accumulation of cotton at flower and boll stage.It could be seen from the spatial and temporal variability equation of soil available nutrient in cotton field that excess or deficiency nitrogen was a disadvantage for biomass accumulation of different fruit branch positions.The spatial and temporal variability of soil available nutrient in cotton field and then biomass accumulation of different fruit branch positions of cotton plant could be affected by the nitrogen application levels in order to get high yield and fiber quality.To sum up,at the nitrogen application level of 360 kg N·hm^-2 for Anyang and 240 kg N·hm^-2 for Nanjing,the spatial and temporal variability of soil available nutrient in cotton field at flower and boll stage were the optimal.Earlier starting date of speed accumulation period,shorter duration of speed accumulation and maximal speed were the characteristic and the eigenvalues were more harmonious at the nitrogen application level of 360 kg N·hm^-2 for Anyang and 240 kg N·hm^-2 for Nanjing.It was a adventage for biomass accumulation to be obtained.Yield components were relative optimal,yield was the maximum and the fiber quality of length and strength was better.