Nitrogen storage in density and size fractions varied with tillage practices and cropping systems under residue return

Residue return can prevent or restore the degradation of cropland, meanwhile, additional N input from residue return inevitably result in the changes of soil nitrogen (N) pools. Our objectives were to evaluate these changes in a 16-year field experiment. The residue return experiment consisted of no-tillage (NT) and mouldboard plough (MP), combined with continuous maize (Zea mays L.) (MM) and maize-soybean (Glycine max Merr.) rotation (MS) cropping systems, that is, NTMM, NTMS, MPMM, MPMS; conventional tillage (removal of crop residue and deep plough) with continuous maize (CTMM) was included as a control. The soil was separated into density (LF, light fraction) and particle size (sand, silt and clay) fraction. In 0-5 cm and 5-10 cm layers, soil TN content in NT was higher than MP, whereas the opposite trend was observed in 10-20 cm. Thus, the stratification ratio of soil TN was greater under NT. Cropping system affected soil TN as MM > MS. Residue return increased soil N storage by 6.44%-24.85% in the plough layer. Taking CTMM as the baseline, NTMM and MPMM increased the N storage in all physical fractions, while the decrease of silt-N storage was observed in NTMS and MPMS. Under residue return, the distribution of N storage changes in LF and sand fraction was affected by tillage practice, and that in silt and clay fraction was affected by cropping system. In summary, NTMM is effective for soil N accumulation due to its highest N storage and all physical fractions of N storage was enhanced.

Effects of the Rapid Construction of a High-Quality Plough Layer Based on Woody Peat in a Newly Reclaimed Cultivated Land Area

To implement the balance system of cultivated land in occupation and supplement and to adhere to the principle of “supplement the occupied cultivated land of high quality with the one bearing same quality”, in the thesis, a field experiment was conducted to study the effects of woody peat on soil physical, chemical, and biological properties of the plough layer and its crop yield. Furthermore, the correlation between soil indexes and crop yield under the best fertilization mode through the addition of the natural material of woody peat instead of lengthy cultivation of the plough layer to rapidly construct a high-quality plough layer and solve the practical problem that the natural endowment of newly reclaimed cultivated land is far less than the occupied high-quality cultivated land was explored. The land remediation project of Fuping County, Hebei Province, was taken as the experimental area, and the five most representative and effective datasets were selected and studied. The results demonstrated that the addition of woody peat and rotten straw could reduce soil particle size and bulk density and alleviate soil viscosity and acidification. An increase in soil organic matter, soil microbial biomass carbon (MBC), alkali-hydrolyzable nitrogen, available phosphorus, and available potassium and a decrease in the heavy metal content were also observed. The results indicated that the application of woody peat achieved the expected effect of the rapid construction of a high-quality plough layer. The best mode of fertilization was A2, which provided a good reference for the rapid construction of a high-quality plough layer in the future. The analysis of the correlation between soil indexes and crop yield illustrated that the organic matter content, soil available nutrients, and crop yield had a significant positive correlation; the organic matter content and soil available nutrients showed the same tendency, which suggests that soil organic matter content and soil fertility level are closely related and that soil fertility plays a decisive role in crop yield under the same external conditions. Woody peat exerted an eminent influence on the organic matter content and soil available nutrients to determine the change in crop yield, which provides a reliable basis for future research on land improvement projects to increase crop yield.

DESIGN AND OPERATION PARAMETERS OPTIMIZATION OF 4SGMS-220 PLOUGH LAYER RESIDUAL FILM RECOVERY MACHINE

In view of the harm of residual film retention to soil environment in Xinjiang which even affected the germination of seeds and hindered the growth of crop roots in severe cases, in this paper, a 4SGMS-220 plough layer residual film recovery machine with a ground preparation device is designed. The main part of the machine is composed of a filming mechanism, a conveying mechanism, a soil crushing roller, and a film collecting box. The machine can achieve simultaneous film lifting, film stripping, collecting membrane and suppression operations. In this paper, primary focus is placed on the design of the filming mechanism, while the movement trajectory of the comb teeth and the filming condition are analysed in detail. In order to obtain the optimal combination of equipment and operating parameters, the equipment traveling speed, the filming device rotational speed, and the comb teeth depth are used as the influencing factors. Furthermore, the residual film recovery rate and impurity rates are employed as test indicators for three-factor three-level response surface experiment and optimization via Design-Expert software. The results indicate that optimal operation is achieved for the machine travel speed of 4.1 km/h, the filming device speed of 106 min-1, and the comb tooth soil penetration depth of 139.2 mm. The residual film recovery rate is equal to 74.32%, while the residual film impurity rate is equal to 7.11%. The difference between the test results and the predicted values is relatively small. Thus, it can be concluded that the optimized model is reliable.

Effects of Soil Bulk Density and Moisture Content on the Physico-Mechanical Properties of Paddy Soil in Plough Layer

For paddy-upland rotation areas in the middle and lower reaches of the Yangtze River, the paddy soil has undesired physico-mechanical properties of tillage during the dry season. The purpose of this study is to determine the effects of soil bulk density and moisture content on the physico-mechanical properties of paddy soil in the plough layer. The bulk density and moisture content were selected as experimental factors, and the cohesion, tangential adhesion, plasticity index, and soil swelling rate were chosen as experimental indices from physico-mechanical properties of paddy soil in the plough layer. The experimental factors were quantitatively analyzed to explore the change characteristics of the physico-mechanical properties of paddy soil in the plough layer. Conclusions were obtained that show that when the bulk density increased in the range of 1 to 1.6 g·cm−3, the cohesion, tangential adhesion, plasticity index, and swelling rate of paddy soil increased in different degrees. Between 15% and 35% moisture content, the cohesion increased first and then decreased with the increase of moisture content, while the peak cohesion value occurred at the moisture content of 20%. Moisture content was positively correlated with tangential adhesion and negatively correlated with soil swelling rate. This study provides a reference for the regulation of paddy soil tillability in the middle and lower reaches of the Yangtze River Basin.

The Pyrogenic Archives of Anthropogenically Transformed Soils in Central Russia

Charred materials (anthracomass) stored within a soil constitute a major part of its pyrogenic archive and could provide evidence of past fire events, both natural and anthropogenic. However, the dynamics of man-made contributions to the total anthracomass of soil at different time scales are insufficiently understood. In this study, we determined the anthracomass concentrations, stocks, and particle-size distribution in anthropogenically transformed soils of different genesis and ages. Materials were collected from the following archaeological sites within Central Russia—3 Upper Paleolithic sites (Avdeevo, Khotylevo-2 and Yudinovo-1), 2 Early Iron Age settlements (Khotylevo-2 and Yaroslavl), and 1 Medieval site (Yaroslavl). Samples from different cultural layers (CLs), plough layers, and native soils (control) were studied. We identified anthracomass accumulation over a wide chronological scale starting from the Upper Paleolithic Period. The high degree of preservation of anthracomass in ancient anthropogenically transformed soils was explained by the presence of large fragments of charred bones, which are more durable in comparison to wood charcoal. The anthracomass concentrations and stocks in the Early Iron Age plough layer were lower than those in the Medieval plough layer. CLs were generally more enriched in the anthracomass than plough layers, due to their sedimentational genesis, which is more favorable for anthracomass preservation than the turbational genesis of plough layers. However, the differences between charred particle sizes in synlithogenic CLs and turbational plough layers were less clear than expected, due to the specific conditions of formation of each particular layer, e.g., burial rate, duration of ploughing, and type of agricultural land use.

Smash-ridging cultivation improves crop production

Smash-ridging cultivation is an efficient farming method that was recently developed in China. The technique involves vertically cutting by using a spiral drill, causing the soil to ‘suspend’ as ridges, thereby breaking through the traditional plough pan, and thickening the plough layer up to 30–50 cm. Smash-ridging cultivation has effectively improved soil quality and has increased the water and nutrient retention capacity. Loose soil enables the plant’s root system to optimally develop and more efficiently absorb nutrients. This facilitates the growth of the above ground parts of plant, leading to a significant increase in crop yield. This method has been successfully applied on 40 crops and tested in 26 provinces. The yield increase within a single season ranges from 10.0% to 54.8%. This technique may have a positive and extensive impact on food safety and agricultural production in China and the rest of the world.

Characterizing macropore structure of agrosoddy-podzolic soil using computed tomography

The agrosoddy-podzolic soil (Eutric Albic Glossic Retisol (Abruptic, Loamic, Aric, Cutanic)) is typical for Moscow Oblast and is used for agricultural purposes, resulting in use of various agrochemicals and pesticides. The presence of macropores and cracks in such soils leads to preferential water and substance transfer and nonequilibrium conditions. Therefore, it is important to study the numerical characteristics of the pore space of soils to adjust mathematical models of substance transfer. Undisturbed soil monoliths 10 cm in diameter taken from Ap (from 0 to 30 cm) and E, BE horizons (from 30 to 50 cm) were investigated under the field moisture conditions and after saturation using the tomographic core analyzer RKT-180 with the resolution of 200 μm/pixel. Using the X-ray computer tomography, it has been established that the plough layer of the agrosoddy-podzolic soil contains over 7% of macropores larger than 1 mm, while the subsurface layer has a porosity of about 3%. After saturation, some of the inter-aggregate pores overlap, which leads to a decrease in the total porosity to 4% in the upper and 2% in lower horizons, as well as increase in the average pore diameter. The number of macropores determined by tomographic analysis is one third higher than the values calculated using pedotransfer functions for this soil. The data obtained in this paper are recommended for use in national scenarios of migration of substances (pesticides, agrochemicals, salts) in soils.