The Limit Effect Of Film Residue On Cotton Yield

Xinjiang is currently one of China’s three largest cotton-planting regions. Cottonplantations account for more than half of the total agricultural area in Xinjiang. All cottonplantations in Xinjiang involve film mulching. However, this leaves behind plastic filmresidue, which has become a very serious problem. Average residual percentage is24%,allowing plastic film residue to seriously harm on soil quality and cotton yield. At present,because cotton yield has been improved, little attention has been paid to the hazards of plasticfilm residue.On the basis of the complete survey of plastic film residue in the production area ofshort-staple cotton in northern Xinjiang, a gradient of no plastic film residue and filmmulching, and6density plastic film residue gradients were setted based on the number ofcontinuous years of film mulching:0kg·hm^-2（0years）,250kg·hm^-2（13years）,500kg·hm^-2（31years）,1000kg·hm^-2（68years）,1500kg·hm^-2（104years）, and2000kg·hm^-2（141years）. The paper analyzed the effects of plastic film residue accumulation on soil quality andcotton yield. The paper studied the trends in and reasons for yield variation. Differencesbetween cotton varieties with different root depths were compared. The paper quantified theeffect of film residue on cotton yield by experiments and mathematical modeling. The resultsshowed that:（1） The number and weight of residue mulch presented a tendency of straight climb with theincrease of mulching years. The number and weight of per unit area increased by40.02ten thousand hm^-2and13.66kg hm^-2per year with the mulching annual increase. On thespatial distribution, after5years of continuous mulching, residue mulch’s size and densitywill be evenly distributed in soil （0～40cm）. After10years of continuous mulching, threearea types of mulch residue（0～25cm2,25～100cm2and>100cm2） will be no differencein unit weight. The harmful mulch residue type（>25cm2） have always accounting for morethan60%with the mulching annual increase.（2） The yield of two cotton varieties have a trend of decrease with the increase of filmresidue.The density of plastic film residue can reach1000kg·hm^-2after68years ofcontinuous film mulching, and the cotton yield of “Xinluzao33” and “Xinluzao13” wasfound to decrease by18.1%and13.5%, respectively. The density of plastic film residuewas found to reach2000kg·hm^-2after141years of continuous film mulching, and theyields of two varieties decreased by38.3%and45.2%. The plastic film residue on cottonyield have a significant effect.（3） High concentrations of plastic film residue caused soil quality to deteriorate and causeduneven distribution of soil moisture. When the density of soil plastic film residueexceeded1000kg·hm^-2, the infiltration of soil moisture was hindered. Soil moisturelevels decreased significantly at depths of30～40cm. Plastic film residue was found tocause depletion of soil nutrients. When the density of soil plastic film residue reached2000kg·hm^-2, pH increased by10.1%, and organic matter, alkaline hydrolysis of N,available P, and available K decreased by16.7%,55.0%,60.3%, and17.9%, respectively.（4） We found “Xinluzao33” have better adaptability than “Xinluzao13” by comparing crowth characteristics（biomass, root to shoot ratio and root surface area） and yield andcharacters（yield, early maturity and stand establishment）. The yield of “Xinluzao13”decreased by6.9%more than “Xinluzao33” and the stand establishment of “Xinluzao13”decreased by8.1%more than “Xinluzao33” when plastic film residue was2000kg·hm^-2.（5） Increasing rate of film mulching start less than decreasing rate of plastic film residue after75years of continuous mulching of “Xinluzao33”. We will not use film mulch from the76year, and the total increasing yield of film mulching start less than increasing yield ofplastic film residue in121year of “Xinluzao33”. Increasing rate of film mulching startless than decreasing rate of plastic film residue after97years of continuous mulching of“Xinluzao13”. We will not use film mulch from the98year, and the total increasing yieldof film mulching start less than increasing yield of plastic film residue in157year of“Xinluzao13”.（6） It’s the first time that we studied the effects of plastic film residue accumulation on soilquality and cotton yield by setting density plastic film residue gradients, and made clearthe damage degree of film residue. Without timely measures, it will seriously endanger thesustainable development of cotton and the sustainable use of land. We found applying andcultivating deep root system cotton could mitigate the hazards of residual film. This studyprovided theoretical support for the reasonable preventive measures of government andcotton grower.