Characteristics of Mulching Plastic Film Residue in Cotton Fields in the Yellow River Delta

In order to get a clear picture of distribution characteristics of mulching plastic film residue in cotton fields in the Yellow River Delta and make scientific pollution prevention and control strategies, an investigation was conducted in Dongying City. Five typical cotton fields were chosen, and then the number, distri- bution density and area of residual film were measured. The results showed that the residual film was 18. 84-53. 53 kg/hm^2 in cotton fields for more than 20 years, and the differences between fields were larger. The residual density was 225-340 thousand per hectare. There were great differences among residual pieces. The proportion of residual pieces over 25 cm^2 was 94. 1%, that between 100 cm^2 and 500 cm^2 was more than 50. 0%, and that bigger than 500 cm^2 was about 21. 0%. In the Yellow River Delta cotton region, large, thin and difficult to recovery were the main characteristics of mulching plastic film residue, and it had the possibility of mi- grating to deep soil. Thus, the ecological risk of mulching plastic film residue was higher. Key words The Yellow River Delta; Cotton field; Residue of mulching plastic film; Distribution characteristic

The status and distribution characteristics of residual mulching film in Xinjiang, China

Pollution of residual plastic film in arable lands is a severe problem in China. In this study, the status of residual film and influential factors were investigated using the methods of farm survey in combination with questionnaires and quadrat sampling at a large number of field sites in Xinjiang Uygur Autonomous Region, China. The results showed that the amount of film utilization increased largely and reached to 1.8×10~5 t in 2013. Similarly, the mulching area also substantially increased in recent decades, and reached to 2.7×10~5 ha in the same year. According to the current survey, 60.7% of the sites presented a greater mulch residue than the national film residue standard（75 kg ha^（–1））, and the maximum residual amount reached 502.2 kg ha^（–1） in Turpan, Xinjiang. The film thickness, the mulching time and the crop type all influenced mulch residue. The thickness of the film had significantly negative correlation with the amount of residual film（P0.05）, while the mulching years had significantly positive correlation with it（P0.05）. The total amount of residual film in Xinjiang was 3.43×105 t in 2011, which accounted for 15.3% of the cumulative dosage of mulching. Among all the crops, the cotton fields had the largest residual amount of mulch film（158.4 kg ha^（–1））, and also the largest contribution（2.6×10~5 tons） to the total amount of residual film in Xinjiang.

Benefits of Conservation Agriculture on Soil and Water Conservation and Its Progress in China

Conservation agriculture has been practised for three decades and has been spread widely. There are many nomenclatures surrounding conservation agriculture and differ to each other lightly. Conservation agriculture （CA） is a system approach to soil and water conservation, high crop productivity and profitability, in one word, it is a system approach to sustainable agriculture. Yet, because conservation agriculture is a knowledge-intensive and a complex system to learn and implement, and also because of traditions of intensive cultivation, adoption rates have been low, since to date, only about seven percent of the world＇s arable and permanent cropland area is farmed under conservation agriculture. The practice and wider extention of conservation agriculture thus requires a deeper understanding of its ecological underpinnings in order to manage its various elements for sustainable intensification, where the aim is to conserve soil and water and improve sustainability over the long term. This paper described terms related to conservation agriculture, presented the effects of conservation agriculture on soil and water conservation, crop productivity, progress and adoption of CA worldwide, emphasized obstacles and possible ways to increase CA adoption to accelerate sustainable development of China agriculture.

Environmental behaviors of phoxim with two formulations in bamboo forest under soil surface mulching

Phoxim（emulsifiable concentrate（EC） and granules（G）） has been widely used in bamboo forests. The persistence and magnitude of phoxim residues in the crop and soil must be investigated to ensure human and environmental safety. The environmental behaviors of the two formulations were investigated in a bamboo forest under soil surface mulching conditions（CP） and non-covered cultivation conditions（NCP）. The half-lives of phoxim in soil under the two conditions in soil were 4.1–6.2 days（EC） and 31.5–49.5 days（G）,respectively. Phoxim in EC could be leached from the topsoil into the subsoil. A minimized leaching effect was observed for G under NCP. Inversely, an enhanced leaching effect was observed for G under CP. The G formulation resulted in more parent compound（in bamboo shoots） and metabolite（in soil） residues of phoxim than in the case of EC, especially under CP conditions. In addition, the intensity and duration of the formulation effect on soil p H adjustment from G were more obvious than that from EC. Results showed that the environmental behaviors（distribution, degradation, residue） of phoxim in the bamboo forest were significantly influenced by the type of formulation. The prolongation effect from phoxim G might cause persistence and long-term environmental risk. However,bamboo shoot consumption could be considered relatively safe after applying the recommended dose of the two phoxim formulations.

Separation and mechanical properties of residual film and soil

In Xinjiang's perennial cotton(Gossypium hirsutum)-planting soil,the average residual amount of plastic film is as high as 265.3 kg/hm2,and the problem of pollution with residual plastic film in the tillage layer has become a major problem.To explore the mechanism of the separation of residual film and soil in the tillage layer and determine the conditions favorable for the separation of residual film-soil,this study established a constitutive model of residual film-soil contact based on the discrete element method and used the established constitutive model to simulate the process of separating residual film and soil.In addition,the influence of parameters,such as soil particle size and water content,on the force to separate the residual film and soil was studied using single factor and orthogonal experiments.The simulation results showed that the changing trend of the residual film-soil separation force curve did not differ much between the simulation and the actual comparison,and the curves were roughly the same.They all decreased after the separation force reached its peak value,but the simulated separation force curve was similar to that of the actual separation force.It increased rapidly from the beginning and reached peak separation force first.The single-factor experiment showed that the separation force of the used residual mulching film was higher than that of the unused mulching film.Under the same conditions,the maximum separation force required to separate the residual membrane was proportional to the positive pressure on the surface of the residual membrane and the size of soil particles.Under the same conditions,the maximum separation force required to separate the residual film is proportional to the positive pressure on the surface of the residual film and the size of soil particles.The maximum separation force decreased first and then increased as the soil moisture content increased.The results of the orthogonal experiment showed that the soil particle size had the greatest effect on the maximum separation force,followed by positive pressure on the residual film surface,soil moisture content,and the service life of mulch.In addition,film mulch that was buried 60 mm deep in the soil,a particle size of more than 2.5 mm,and a soil moisture content of 8%was the optimal combination of parameters to effectively separate the film mulching residue from the soil.