| Machine-harvested cotton is a new type of cotton varieties in order to adapt to the cultivation and harvesting machinery.Due to the difference of planting pattern and plant type structure,the cotton picking and planting of cotton should pay more attention to the rational allocation and utilization of water.So it is significant to make clear the effect of drip irrigation on the photosynthetic characteristics and yield formation mechanism.This study is a two-year continuous trial:the first year is the screening test of drip irrigation frequency and the second year is a screening test of drip irrigation quota.As for the first year study,drip irrigation quota was set to be 4500 m~3/hm~2,and the experiment set up 3 different drip irrigation times:6 times(D6),eight times(D8)and 10 times(D8).The changing characteristics of photosynthesis parameters,fluorescence kinetic parameters and yield formation of cotton under different drip irrigation times were studied.At the same time,the best allocation number was screened for drip irrigation.With data of the best number of drip irrigation in the last year,the second year study set 3 kinds of drip irrigation quota(4500 m~3/hm~2(D1)?3700 m~3/hm~2(D2)?2900 m~3/hm~2(D3).The changing characteristics of photosynthesis parameters,fluorescence kinetic parameters and yield formation of cotton under different drip irrigation times were studied again.Through two years of study on water regulation of cotton picker machine photosynthetic characteristics and yield formation,the mechanism of water saving and yield increase under the cotton-planting pattern was defined,which provided theoretical basis and technical guidance for precise water and fertilizer management of cotton under mulch drip irrigation.The main research results are as follows:1.Effect of drip irrigation frequency on Photosynthetic Characteristics and yield formation of cotton The net photosynthetic rate(D6),maximum photochemical efficiency(Fv/Fm),photochemical quantum yield(Yield)and photochemical quenching coefficient were significantly lower than those in other treatments.At the meantime,after D6 treatment,the non-photochemical quenching coefficient(NPQ)increased significantly,photosynthetic matter accumulation is limited,which will lead to the low total biomass accumulation,and phenomenon of premature.When treating with D10 method,photosynthetic fluorescence parameters increased significantly after entering the opening stage,but the photosynthate accumulation shifted to vegetative organs,which is not conducive to yield formation.On the other hand,the net photosynthetic rate of D8 was higher at the growth stage:The proportion of accumulation and distribution of photosynthetic matter is harmonious,good plant type structure can be obtained and eventually get the highest production at last.2.Effect of drip irrigation quota on Photosynthetic Characteristics and yield formation of cottonBeyond all types of treatments,under D3 treated drip irrigation quota,cotton net photosynthetic rate decreased significantly.At the same time,the maximum photochemical efficiency(Fv/Fm)and photochemical quantum yield(Yield)decreased,which could lead the significantly low of The total amount of photosynthetic matter accumulation within all the treatments.On the contrary,D1,D2 treatment significantly increased the net photosynthetic rate in the light,the proportion of biomass accumulation and allocation is more reasonable.And number,boll weight and yield of Boll was higher than D3 treatment.Comparing with D1 treatment,D2 treatment can ensure the efficient water use efficiency without affecting the yield.This shows that the drip irrigation quota treated by D2 is more conducive to the high yield and high efficiency of cotton picker.In summary,under field conditions in North Xinjiang,the use of drip irrigation treatment D2 quota(3700m~3/hm~2),distribution of drip irrigation in D8 treatment(8 times)can effectively improve the photosynthetic capacity of plant,promote the distribution of photosynthetic matter to reproductive organs,and further development of water saving and yield increasing potential of cotton picker. |
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