| The issue of white contamination is becoming more serious.To clarify the hazards of residual film to facility agriculture and realise the sustainable planting of residual film-contaminated land,facility tomatoes are used as study subjects for a two-year cultivation experiment in this study.Six residual film levels(0 kg/hm~2,200kg/hm~2,400 kg/hm~2,800 kg/hm~2,1600 kg/hm~2and 2000 kg/hm~2,which are denoted as CK,R1,R2,R3,R4 and R5)were applied and the irrigation amount was designed to be 3100 m~3/hm~2(2019)and 1300 m~3/hm~2(2020)for the simulation of different rainfall collecting conditions.The 0-50cm soil layer water content and nitrate nitrogen,enzyme activity,tomato growth and yield under the influence of residual film are measured and the variation characteristics of soil environmental factors under different residual film levels are studied.In addition,the influence mechanism of residual film on the yield and quality of greenhouse tomatoes is revealed,the source-sink relationship of facility tomatoes under residual film stress is analysed,the water consumption changes of different residual film treatments are clarified and the water production function of tomatoes under residual film stress is established.Comprehensive evaluation methods are used for reconciling soil and growth factors and the impact different levels of residue film have on tomato growth is analysed.The main conclusions are as follows:(1)The effect residual film has on soil water distribution and water consumption of tomatoes is clarified.Residual film was found to block soil continuity,hindering water infiltration.Increasing the residual film amount increased the water content of the vertical 10-30 cm soil layer and the water content of the soil layer below 30 cm was lower than that of the 10-30cm layer.The two-dimensional distribution results of water content reveal that the hindering effect of residual film caused the water convergence zone in the vertical 10-30 cm soil layer and the water convergence effect in 2020 was obviously than it was in 2019.The water content of the soil layer below30 cm under the dripper was found to decrease with residual film increased in each growth period.Due to different irrigation amounts,the soil moisture content below the ridge-furrow junction area decreased with residual film increased in 2019,while an increase in soil moisture content was observed in 2020.The hindering effect of residual film on soil water movement occurred in both horizontal and vertical directions.800 kg/hm~2and 200 kg/hm~2can be used as the thresholds of residual film amount under high irrigation and low irrigation respectively.When these thresholds are exceeded,soil moisture distribution changes significantly.(2)The effects residual film has on nitrate nitrogen concentration and soil enzyme activity are investigated.Residual film was found to indirectly affect soil nitrate nitrogen distribution and soil enzyme activity under the premise of affecting soil water distribution.Soil nitrate nitrogen content in the 0-20 cm soil layer in the flowering and fruit-bearing period and fruit swelling period initially decreased before increasing with the residual film amount increased.Due to the hindrance of residual film,the maximum nitrate nitrogen concentration of residual film treatment generally appeared in the 10-30 cm soil layer.The increase in residual film amount inhibited soil nitrate nitrogen accumulation in the 20-50 cm soil layer.The average soil nitrate concentration in 0-50 cm of residual treatments in 2019 and 2020 decreased7.49-30.85 mg/kg,8.53-26.72 mg/kg compared with CK.In 2019 and 2020,the average soil urease activity was found to initially increase before decreasing with the increasing residual film amount.The average soil invertase activity decreased with the amount of residual film increased.The increase in the amount of residual film served to promote the activity of soil alkaline phosphatase.The average soil alkaline phosphatase activity of R1 to R5 was increased by 0.169-0.454 mg/(g·24h)and0.008-0.432 mg/(g·24h)compared with CK in 2019 and 2020.(3)The internal mechanism of the effect of residual film is revealed from the perspective of symplastic growth.When the amount of residual film was more than800 kg/hm~2,the distribution centre of tomato root length density moved up,while the root length density of the soil layer below 30 cm decreased as residual film increased.The NRLD distribution model of tomatoes with residual film content was then established,and the determination coefficient was found to be 0.90,RMSE was 0.42and MRE was 23.73%.During the seedling stage of tomato growth,plant height increased with residual film amount increased,but the increase of residual film amount inhibited plant height and stem diameter growth(50 days after transplanting).In 2019,the total water consumption of R1 to R4 increased 3.41-10.08mm compared with CK and decreased by 0.56-3.41mm compared with CK in 2020.The yield of R1to R5 decreased by 3.65-17.45×10~3kg/hm~2and 7.21-24.44×10~3kg/hm~2in 2019 and2020 compared with CK.Generally,the change of root growth and distribution caused by residual film was identified as one of the reasons for differences in the aboveground growth of tomatoes in each treatment.The increase of residual film in2019 and 2020 resulted in the Vitamin C content and soluble sugar content of the tomatoes being significantly higher than CK.In comparison to CK,the water use efficiency of R1 to R5 treatment decreased by 0.56-5.24 kg/m~3in 2019 and2.10-13.81 kg/m~3in 2020.(4)The effect residual film has on the source-sink relationship of tomatoes is studied and the reason for tomato yield reduction is clarified.The average chlorophyll content of residual film treatment during the growth period was 1.83%-7.32%higher than that of CK in 2019 and 1.58%-3.37%higher in 2020.The photosynthetic rate of tomato leaves decreased with residual film increased in both years.In terms of storage performance,the dry matter quality of tomato stems and leaves increased as residual film increased at the mature period of tomato growth.The increase of residual film amount in the mature period in 2019 and 2020 reduced the quality of fruit dry material in 9.80-51.81g/strain,3.04-51.76g/strain,and reduced the proportion of dry material distribution to plant fruit.Therefore,the strong restriction of"source"caused by the decrease of net photosynthetic rate of tomato leaves under the influence of residual membrane,which then affects the material distribution ratio between vegetative growth and reproductive growth,is the main reason for the reduction of tomato production.(5)The effect residual film has on tomato growth is clarified based on water production function and comprehensive evaluation method.The water production function model of tomatoes under residual film stress was established based on the Stewart model.The results found that the coefficient of determination between the calculated value of the model and the measured value was 0.78,and the RMSE was8.68×10~3kg/hm~2.In addition,the critical value of residual film amount that starting has a significant impact on water consumption was found to be 310 kg/hm~2and the residual film amount that has the greatest impact on water consumption was identified as 620 kg/hm~2.The results of redundancy analysis found the change of soil moisture content and soil enzyme activity caused by residual film amount changes under a high irrigation amount to be the main reasons for tomato yield and fruit quality differences in different treatments.In addition,the change of soil moisture content caused by residual film amount change under a low irrigation amount was identified as the main reason for tomato yield and fruit quality differences in different treatments.The comprehensive evaluation method was used in combination with soil factors,tomato growth factors and other indicators for the comprehensive evaluation of the degree of influence of residual film.The results revealed that the comprehensive scores in 2019were ranked from high to low:CK>R2>R1>R4>R3>R5 and the order was CK>R3>R4>R2>R5>R1 in 2020.Regardless of irrigation amount,the comprehensive score of R5 treatment tomatoes was found to be lower than other treatments.In combination with soil moisture and root conditions,it was found that increasing the irrigation water amount when residual film pollution occurs reduces the impact film residue has on facility tomato growth. |
PDF Full Text Request