| Film mulching plays a very important role in soil warming, water preserving, soil conservation, reducing soil erosion and increasing yield, which is widely used in agricultural production. However, every year crop mulching with new film come into being of a large number of film residue, leading to the "white pollution", which make agricultural ecological environment degenerated. At the same time, in the Hetao region the farming practice such as plough and irrigation is after harvest in autumn that soil was completely exposed during fallow period of cropland from November to next early May (about7months), combined with climatic drought and windy, which result in excessive cropland evaporation, poor capacity of soil water, severe soil erosion, and finally the cropland deteriorated. Aiming at reducing agricultural pollution caused by plastic film, the effects of re-used plastic film mulching on soil temperatures, seed emergence and all seedlings period, sunflower’s growth and development, sunflower’s yield, soil moisture, water use efficiency and soil erosion during fallow period of cropland were studied, investigated the effects of re-used plastic film mulching on sunflower’s economic benefit, the study also investigated plastic film residue and sunflower’s yield, which compared with new plastic film mulching and bare field in Hetao region. The results were as follows:1. Re-used film could increase the soil temperatures. Compared with bare field, the soil temperature of re-used film mulching increased1.3～4.0℃and0.7～1.8℃separately in the highest and lowest temperature stage. The soil average temperature increased significantly1.7～2.1℃in upper layer (0-20cm) and1.8～2.0℃in lower layer (30-50cm); compared with new film mulching lower1.3～2.0℃in upper layer, and similar as in lower layer. Compared with bare field, Daily maximum and minimum temperatures of re-used film mulching were postponed about1hour, similar as new film mulching. Re-used plastic film mulching can increase the soil temperatures in sunflower earlier and later stage, it’s warming effect was:sowing stage> seedling stage> maturing stage>blooming stage> after flowering stage; During emergence stage (7days after sowing), effective accumulated temperature of re-used film mulching was21.6℃and23.8℃higher than that of bare field in depth of5cm and10cm. Compared with new film mulching, it was12.4℃and10.0℃lower in depth of5cm and10cm. During all stage, effective accumulated temperature of re-used film was229.5℃higher than that of open field,101℃slightly lower than new film in the depth of5cm. 2. Re-used tilm could improve the soil moisture, increasing water use efficiency. The soil moisture of re-used plastic film mulching was increased1.5percentage points in the soil depth of0-100cm and maximum of1.9or2.6higher in the soil depth of0-10cm than that of open field in sunflower’s growth stage. Soil water of re-used film was more than open field’s24.8mm or33.0mm before seeding and after soil water was replenished to same level,21.6mm or24.5mm was more than open field’s at harvest. Re-used film’s C.V of vertical soil moisture was dropped in3.6%or4.8%than that of open field. Meanwhile, water use efficiency of re-used film were higher significantly than that of open field15.7%or22.7%respectively in2010and2011, no significant with new film.3. Soil microbial biomass carbon, nitrogen and phosphorus content of re-used film mulching increased at different degree. compared with bare field and new film mulching, soil microbial biomass carbon content in0-40cm of re-used film were higher significantly (p<0.01)13.8%and12.1%respectively, soil microbial biomass nitrogen content in0-40cm of re-used film were higher significantly (p<0.05)5.0%and4.0%respectively, soil microbial biomass phosphorus content in0-40cm of re-used film were higher significantly34.2%a nd18.3%respectively(p<0.01). Growth stage changes of Soil microbial biomass carbon, nitrogen and phosphorus content are different. The soil microbial biomass carbon content decline with fluctuation effecting by irrigation; microbial biomass nitrogen content decreased; microbial biomass phosphorus content was increased first and then decreased. Vertical changes of the soil microbial biomass carbon, nitrogen, phosphorus content are reduced with increasing soil depth.4. Soil enzyme activity of re-used film mulching increased at different degree. compared with bare field and new film mulching, soil catalase activity in0-40cm of re-used film were higher significantly4.2%and2.6%respectively, soil urease activity in0-40cm of re-used film were higher no significantly1.1%and significantly7.4%respectively, invertase activity in0-40cm of re-used film were higher significantly3.8%and3.0%respectively(p<0.05). Growth stage changes of soil catalase activity, soil urease activity, soil invertase activity are different from each other. The soil catalase activity is relatively stable Beginning from sowing to squaring, decreased to a minimum in flowering, after rising up to the maximum in harvest: soil (?)rease activity beginning with a minimum in sowing rise up to the maximum in squaring: then decreased decreased to flowering; soil invertase activity was f(?)uctuating decline effecting by irrigation, and with a minimum in squaring. Vertical changes of the soil catalase activity, soil urease activity, soil invertase activity are reduced with soil deepening.5. Re-used film could also decrease sunflower’s growth and development time and increase the yield of sunflower. Mulching with re-used film could effectively shorten seed germination for1-2days. Meanwhile, growth period of re-used film was significant earlier than open field5-6days and not significant later than plastic film2days. In addition, plant height; stem diameter, disc diameter, leaf dry weight and total dry weight of re-used film mulching was significantly higher than that of bare field; Except stem diameter, plant height, disc diameter, leaf dry weight and total dry weight of re-used film mulching was slightly lower than that of new film mulching, but the difference was not significant. Compared with bare field, yield per plant of re-used film mulching was significantly increased3.3%(2010) and10.4%(2011),100-seed weight of re-used film mulching was significantly increased3.7%(2010) and5.8%(2011), and they were lower than that of new film mulching, but the difference was not significant. In addition, compared with bare field, sunflower yield of re-used film mulching was significantly increased11.4%(2010) and16.8%(2011), and compared to the new film treatment, the yield decreased3.3%(2010) and2.6%(2011)(p<0.05).6. Re-used plastic film mulching had significantly increased the economic benefit. Compared with bare field, the sunflower’s yield of re-used film mulching increased9.6to15%significantly, and lower than new film by2.6to4.9%(p<0.05). Compared with bare field, the input of re-used film mulching was reduced by5.6%to9.4%, which was1.6%to6.1%lower than that of new film mulching. The output of re-used film mulching was9.6%to18.1%significantly higher than that of bare field and2.5%to4.9%lower than that of new film mulching. The net income of re-used film mulching was22590RMB·hm-2to26914RMB·hm-2, obviously increased by19.6%to34.4%than that of open field and0.6%to2.4%less than that of new film mulching. The ratio of output to input of re-used film mulching was the highest (3.0and2.6), higher than that of open field (18.5%and19.9%) and new film (6.7%and3.2%).7. Re-used plastic film mulching can improve the ecological environment of cropland in fallow period, reduce the film pollution. Compared with bare field, the average soil moisture in0-100cm of re-used film mulching increased2.1%, the water storage capacity in0-100cm and0-20cm increased24.8～33.0mm and14.9～15.5mm separately. The soil average temperature significantly increased3.1～2.8℃, especially soil temperature in5cm and10cm increased1.7～4.6℃and2.8～4.1℃separately (p<0.05). Re-used plastic film mulching can reduce the amount of soil erosion significantly by68.77%. Compared with new plastic film mulching, the residual plastic film of re-used film mulching cropland significantly reduced50%, and the film use efficiency increased one time. |
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