Effects of Conservation Tillage on Soil Physicochemical Properties and Crop Yield in an Arid Loess Plateau, China.

Conservation tillage can improve soil physical structure and water storage, protect moisture, and increase crop yield. However, the long-term adoption of a single tillage method may have some adverse effects on soil and ecological environment, although crop yields have increased. Through informed allocation of soil tillage techniques, the combination and configuration of soil tillage measures, such as rotary tillage, subsoiling, and no tillage may reduce the shortcomings of traditional long-term farming. To explore the long-term production mode suitable for production of maize in the loess dryland area, a long-term experiment was conducted in Fuping County, Shaanxi Province, from 2013 to 2018. Six farming modes were used in the experiment: no tillage/subsoiling (N ↔ S), subsoiling/rotary tillage (S ↔ R), rotary tillage/no tillage (R ↔ N), continuous no tillage (N ↔ N), continuous subsoiling (S ↔ S), and continuous rotary tillage (R ↔ R). The changes in soil physical and chemical properties, soil water use patterns, soil water storage, conservation effects during the fallow and growth period, and the effects on farmland yield increase were analyzed. The results showed that rotary tillage can effectively improved soil structure and reduced soil bulk density, where N ↔ S treatment soil bulk density is low and in 0-60 cm soil layer averaged 1.31 g/cm3. Different tillage treatments could be used during the fallow period to store additional soil moisture: the N ↔ S treatment showed good water storage effect. Compared to traditional tillage, different tillage methods provided better soil moisture conditions for crops during the growth period, where N ↔ S treatment showed good soil moisture status during the growth period of spring maize. Among all the treatments, N ↔ S treatment effectively increased the organic carbon storage in the 0-60 cm soil layer, which was 54.3 t/hm2. Compared with traditional tillage, different tillage treatments effectively increased plant height and dry matter accumulation of spring maize, where N ↔ S treatment was found to be the best. Compared with the traditional rotary tillage model, the N ↔ S treatment significantly increased crop yield and water use efficiency (WUE) in continuous cropping fields of corn, the average yield of spring corn was 9340.2 kg/hm2, and the average WUE was 22.9 kg/(hm2·mm). In summary, for long-term sustainable development, the N ↔ S model is the best rotational tillage mode for continuous maize cropping in loess soil.

[Estimation of Topsoil Carbon Sequestration Potential of Cropland Through Different Methods: A Case Study in Zhuanglang County, Gansu Province].

By analyzing the sampled data and the SOC data of the second national soil survey by the mid 80s and the national cultivated land quality evaluation in 2006 in Zhuanglang County, the article studied the cropland topsoil organic carbon sequestration potential estimation using several different methods. The results showed that: (1) There was no significant difference among different estimation methods about cropland carbon sequestration potential in the same region. Taking cropland carbon sequestration potential in Zhuanglang County for example, the theoretical values estimated by maximum value method and classification grading method were 1. 13 Mt and 1.09 Mt, respectively. (2) The real values estimated by classification grading method, saturation method, weighting method were 0.37 Mt, 0.32 Mt, 0.28 Mt, respectively, which were about 1/3 of the theoretical value. (3) The SOC density increments to reach the real level of carbon sequestration potential estimated by classification grading method, saturation method and weighting method were 6.76 t · hm⁻², 5.21 t · hm⁻², 4.56 t · hm⁻² respectively. According to the topsoil carbon sequestration rate of cropland in Zhuanglang county in the recent 30 a, it would need about 24-34 a to achieve the real level. (4) At the county scale, the weighted method was superior to the saturation value method, and the saturation value method was better than the classification grading method in the actual carbon sequestration potential estimation. The classification grading method was better than the maximum value method in the ideal carbon sequestration potential estimation.

[Changes and influencing factors of the soil organic carbon in farmland in the last 30 years on Hilly Loess Plateau: a case study in Zhuanglang County, Gansu Province].

By analysing the sampled data and the results of the second national soil survey by the mid 80 s in Zhuanglang County, the article studied on the changes and influencing factors of the soil organic carbon in farmland of this area in the last 30 years. Farmland samples of top soil (0-20 cm) were collected and analyzed in July 2011. The results showed that (1) The average contents of the soil organic carbon in the county's farmlands were 6.80 g x kg(-1) in 1985 and 8.90 g x kg(-1) in 2011. It increased by 30.9% in the past 30 years, which appeared as a carbon sink effect. The area of increasing contents of soil organic carbon accounted for about 90% of the county's farmland area. (2) Under the available management measures and farmland input, the loessal soil organic carbon stability level was 11.0 g x kg(-1), The SOC accumulation rate showed that the farther the SOC was from the stability level the more quickly it changed, and the closer the SOC was from the stability level the slower it changed. (3) The SOC changes was affected by the altitude, the primary content of organic carbon, and the soil types and so on, in which the greatest contribution factor was the altitude, the influence of the primary content of organic carbon, soil type, production and organic fertilizer on soil organic carbon change was smaller, and the slope aspect had the smallest effect on soil organic carbon change.