Agricultural systems based on crop rotations favour sustainability of cultivation and productivity of the crops. Wheat-forage crops rotations (annual winter binary mixture and perennial alfalfa meadow) combined with i...Agricultural systems based on crop rotations favour sustainability of cultivation and productivity of the crops. Wheat-forage crops rotations (annual winter binary mixture and perennial alfalfa meadow) combined with irrigation are the agronomical techniques able to better exploit the weather resources in Mediterranean environments. The experiment aimed to study the effect of 18 years of combined effect of irrigation and continuous durum wheat and wheat-forage rotations on productivities of crops and organic matter of topsoil. The experiments were established through 1991-2008 under rainfed and irrigated treatments and emphasized on the effect of irrigation and continuous wheat and wheat-forage crop rotations on water use efficiency and sustainability of organic matter. The effect of irrigation increased 49.1% and 66.9% the dry matter of mixture and meadow, respectively. Continuous wheat rotation reduced seed yield, stability of production, crude protein characteristics of kernel and soil organic matter. The yearly gain in wheat after forage crops was 0.04 t (ha·yr)-1 under rainfed and 0.07 t (ha·yr)-1 under irrigation treatments. The crude protein and soil organic matter of wheat rotations, compared to those of continuous wheat under rainfed and irrigated was increase in term of point percentage by 0.8 and 0.5 in crude protein and 5.1 and 4.4 in organic matter, respectively. The rotations of mixture and meadow under both irrigated treatments increased the point of percentage of organic matter over continuous wheat (9.3.and 8.5 in mixture and 12.5 and 9.5 meadow under rainfed and irrigation, respectively). Irrigation reduce the impact of weather on crop growing reducing water use efficiency (mean over rotations) for dry mater production (15.5 in meadow and 17.5 in mixture [L water (kg·dry·matter)-1 ]) and wheat seed yield. The effect of agronomic advantages achieved by forage crops in topsoil expire its effect after three years of continuous wheat rotation.展开更多
： This paper presents the results of laboratory testing on a heavily compacted sand-bentonite mixture. To measure the soil-water retention curve （SWRC） of the mixture over a large range of suction, a pressure plate...： This paper presents the results of laboratory testing on a heavily compacted sand-bentonite mixture. To measure the soil-water retention curve （SWRC） of the mixture over a large range of suction, a pressure plate apparatus and filter papers were used. The obtained SWRC shows that the measurements via the two methods consistently agree with each other. By using a suction-controlled oedometer for unsaturated soils, a series of one-dimensional compression tests were performed on the unsaturated compacted sand-bentonite mixture at different constant suctions. The testing results indicate that the yield stress increases and compression index decreases with the increase of imposed suction. The results also demonstrate that the mixture wetted to saturation and subsequently dried to a certain suction level has a lower yield stress than that wetted directly to the same suction.展开更多
Composts are considered to be one of the best soil amendments. However, the effects of composts with added polymeric materials on soil physical,hydraulic, and micromorphological properties have not been widely discuss...Composts are considered to be one of the best soil amendments. However, the effects of composts with added polymeric materials on soil physical,hydraulic, and micromorphological properties have not been widely discussed. Changes in soil physical properties influence the numerous services that soils provide. We studied the impacts of composts with the addition of three different polymers(F1–F3) produced from polyethylene and thermoplastic corn starch on the physical, hydraulic, and micromorphological properties of two soils, a Cambic Phaeozem and a Luvic Phaeozem. Applying composts with polymers had limited or no significant effect on soil bulk density and porosity, but increased the field water capacity by 18%–82% and 3%–6% and the plant-available water content by 15%–23% and 4%–17% for the Cambic Phaeozem and Luvic Phaeozem, respectively. The application of composts with polymers had a greater effect on the Cambic Phaeozem than on the Luvic Phaeozem. It was suggested that the use of modified composts led to changes in soil physical properties and micromorphological features and this effect was dependent on the compost application rate. Composts made with the addition of composite synthetic and natural material-derived polymers during composting were found to be a composite mixture that can be successfully used in agriculture.展开更多
The contents of both water and rock particles are important factors affecting the mechanical strength of a soil–rock mixture(SRM)filled subgrade in the western mountainous area of China.Therefore,the purpose of this ...The contents of both water and rock particles are important factors affecting the mechanical strength of a soil–rock mixture(SRM)filled subgrade in the western mountainous area of China.Therefore,the purpose of this paper is to study the mechanisms of reconstituted landslide deposit samples with different water and rock particle contents by analysing the characteristics of shear strength,volumetric strain and‘jumping’phenomenon via large-scale direct shear tests.The results show that the influence of water content on shear strength is greater than the influence of rock particle content under a lower normal stress,and the results are reversed in the case of a higher normal stress.The effect of water content on the equivalent cohesion is bigger,especially for the sample with a high rock particle content.The friction angle of the specimen with same water content increases with the increasing rock particle content,but when the number of rock particles increases to a certain extent,there is a little effect on the friction angle.However,the friction angle decreases with increasing water content at the same rock particle content.Specimens with the same rock particle content change from dilation to compression with increasing water content.Finally,the continuous stage of the‘intense jumping’at different water content has been analysed.The‘jumping’phenomenon of samples with low water and rock particle content will first strengthen and then weaken the samples with increasing normal stress.展开更多
文摘Agricultural systems based on crop rotations favour sustainability of cultivation and productivity of the crops. Wheat-forage crops rotations (annual winter binary mixture and perennial alfalfa meadow) combined with irrigation are the agronomical techniques able to better exploit the weather resources in Mediterranean environments. The experiment aimed to study the effect of 18 years of combined effect of irrigation and continuous durum wheat and wheat-forage rotations on productivities of crops and organic matter of topsoil. The experiments were established through 1991-2008 under rainfed and irrigated treatments and emphasized on the effect of irrigation and continuous wheat and wheat-forage crop rotations on water use efficiency and sustainability of organic matter. The effect of irrigation increased 49.1% and 66.9% the dry matter of mixture and meadow, respectively. Continuous wheat rotation reduced seed yield, stability of production, crude protein characteristics of kernel and soil organic matter. The yearly gain in wheat after forage crops was 0.04 t (ha·yr)-1 under rainfed and 0.07 t (ha·yr)-1 under irrigation treatments. The crude protein and soil organic matter of wheat rotations, compared to those of continuous wheat under rainfed and irrigated was increase in term of point percentage by 0.8 and 0.5 in crude protein and 5.1 and 4.4 in organic matter, respectively. The rotations of mixture and meadow under both irrigated treatments increased the point of percentage of organic matter over continuous wheat (9.3.and 8.5 in mixture and 12.5 and 9.5 meadow under rainfed and irrigation, respectively). Irrigation reduce the impact of weather on crop growing reducing water use efficiency (mean over rotations) for dry mater production (15.5 in meadow and 17.5 in mixture [L water (kg·dry·matter)-1 ]) and wheat seed yield. The effect of agronomic advantages achieved by forage crops in topsoil expire its effect after three years of continuous wheat rotation.
基金Supported by the Innovative Foundation for Graduate Students at Shanghai University of China(SHUCX080168)the National Science Foundationof China(10972130)
文摘： This paper presents the results of laboratory testing on a heavily compacted sand-bentonite mixture. To measure the soil-water retention curve （SWRC） of the mixture over a large range of suction, a pressure plate apparatus and filter papers were used. The obtained SWRC shows that the measurements via the two methods consistently agree with each other. By using a suction-controlled oedometer for unsaturated soils, a series of one-dimensional compression tests were performed on the unsaturated compacted sand-bentonite mixture at different constant suctions. The testing results indicate that the yield stress increases and compression index decreases with the increase of imposed suction. The results also demonstrate that the mixture wetted to saturation and subsequently dried to a certain suction level has a lower yield stress than that wetted directly to the same suction.
基金financed by the Ministry of Science and Higher Education of the Republic of Polandwithin the framework of the project “Utilization of Biomass for the Preparation of Environmentally Friendly Polymer Materials” (BIOMASA) (No.POIG 01.01.02-10123/09),partially financed by the European Union within the European Regional Development Fund。
文摘Composts are considered to be one of the best soil amendments. However, the effects of composts with added polymeric materials on soil physical,hydraulic, and micromorphological properties have not been widely discussed. Changes in soil physical properties influence the numerous services that soils provide. We studied the impacts of composts with the addition of three different polymers(F1–F3) produced from polyethylene and thermoplastic corn starch on the physical, hydraulic, and micromorphological properties of two soils, a Cambic Phaeozem and a Luvic Phaeozem. Applying composts with polymers had limited or no significant effect on soil bulk density and porosity, but increased the field water capacity by 18%–82% and 3%–6% and the plant-available water content by 15%–23% and 4%–17% for the Cambic Phaeozem and Luvic Phaeozem, respectively. The application of composts with polymers had a greater effect on the Cambic Phaeozem than on the Luvic Phaeozem. It was suggested that the use of modified composts led to changes in soil physical properties and micromorphological features and this effect was dependent on the compost application rate. Composts made with the addition of composite synthetic and natural material-derived polymers during composting were found to be a composite mixture that can be successfully used in agriculture.
基金supported by National Natural Science Foundation of China(51378072,51878064)the Special Fund for Basic Scientific Research of Central College of Chang’an University(310821162012,310821161023)National Association of public funds of China Scholarship Council(CSC 201706560021)
文摘The contents of both water and rock particles are important factors affecting the mechanical strength of a soil–rock mixture(SRM)filled subgrade in the western mountainous area of China.Therefore,the purpose of this paper is to study the mechanisms of reconstituted landslide deposit samples with different water and rock particle contents by analysing the characteristics of shear strength,volumetric strain and‘jumping’phenomenon via large-scale direct shear tests.The results show that the influence of water content on shear strength is greater than the influence of rock particle content under a lower normal stress,and the results are reversed in the case of a higher normal stress.The effect of water content on the equivalent cohesion is bigger,especially for the sample with a high rock particle content.The friction angle of the specimen with same water content increases with the increasing rock particle content,but when the number of rock particles increases to a certain extent,there is a little effect on the friction angle.However,the friction angle decreases with increasing water content at the same rock particle content.Specimens with the same rock particle content change from dilation to compression with increasing water content.Finally,the continuous stage of the‘intense jumping’at different water content has been analysed.The‘jumping’phenomenon of samples with low water and rock particle content will first strengthen and then weaken the samples with increasing normal stress.
