Monoculture and improper management may reduce soil fertility and deteriorate soil structure in Black soils (Mollisols) of Northeast China. The experiment was carried out from 2015 to 2016 in Black Soils comprising five cropping systems: continuous corn (CC), soybean-corn rotation (SC), corn-soybean rotation (CS), fallow-corn (FC), and fallow-soybean (FS). Our results showed that CS and FS treatments significantly increased mean weight diameter (MWD) and fractal dimension (D) in mechanical stability aggregates (MSAs), and increased MWD and geometric mean diameter (GMD) in water-stable aggregates (WSAs) compared with CC treatment. These two treatments were also significantly increased water-stable aggregates stability rate (WSAR), but decreased percentage of aggregates destruction (PAD) than CC treatment. Meanwhile, CS and FS treatments exhibited a higher carbon accumulation than CC treatment in bulk soils. Soil organic carbon (SOC) concentration in WSA_0.106-0.25,WSA_{2-5 mm}and WSA_{0.5-1 mm}had a dominant effect on aggregate stability. Simutaneously, SOC in WSA_{>5 mm}affected SOC concentration in bulk soils. As a whole, the CS and FS treatments can increase the percentage of macro-aggregates, enhance aggregate stability, as well as increase SOC concentration in bulk soils and all soil aggregate sizes.

Although the effect of elevated CO₂ (eCO₂) on soybean yield has been well documented, few studies have addressed seed quality, particularly at the fresh edible (R6) and mature stages (R8). Under the current global scenario of increasing CO₂ levels, this potentially threatens the nutritional content and quality of food crops. Using four soybean cultivars, we assessed the effects of eCO₂ on the concentrations of crude protein, crude oil, and isoflavones and analyzed the changes in free amino acids, fatty acids, and mineral elements in seeds. At R6, eCO₂ had no influence on soybean seed protein and oil concentrations. At R8, eCO₂ significantly decreased seed protein concentration but increased seed oil concentration; it also significantly decreased total free amino acid concentration. However, at the same stage, the proportion of oleic acid (18:1) among fatty acids increased in response to eCO₂ in the cultivars of Zhongke-maodou 2 (ZK-2) and Zhongke-maodou 3 (ZK-3), and a similar trend was found for linoleic acid (18:2) in Zhongke-maodou 1 (ZK-1) and Hei-maodou (HD). Total isoflavone concentrations increased significantly at both the R6 and R8 stages in response to eCO₂. Compared with ambient CO₂, the concentrations of K, Ca, Mg, P, and S increased significantly under eCO₂ at R6, while the Fe concentration decreased significantly. The response of Zn and Mn concentrations to eCO₂ varied among cultivars. At R8 and under eCO₂, Mg, S, and Ca concentrations increased significantly, while Zn and Fe concentrations decreased significantly. These findings suggest that eCO₂ is likely to benefit from the accumulation of seed fat and isoflavone but not from that of protein. In this study, the response of seed mineral nutrients to eCO₂ varied between cultivars.

Gully erosion is the destructive and dramatic form of land degradation in Northeast China. The region is the grain production and ecological security base of China where the fertile and productive Mollisols are distributed. Though the region was agriculturally developed relatively recently, it went through high intensity cultivation and fast succession processes within short-time scales. Coupled with irrational farming practice choice and land use, hillslope erosion and gully erosion are seriously threatening agricultural production and environmental stability in the region. The awareness of gully erosion by the local governments started in the 1970s, and conservation measures were thus implemented. In this paper, based on our survey, communications with local farmers and stakeholders as well as investigation for gully erosion for the past three years, we summarize the practical and efficient practices to manage gully erosion developed by researchers and farmers in Northeast China during the past 50 years. These practices include various drop structures, soil check dams, masonry check dams, gabion check dams, wicker check dams, continuous live wicker, a shrub plant enclosure, and an arbor plant enclosure. We specifically expound how a gully erosion practice is set up and identify the site conditions for which they are well-suited. The application of these practices depends on topography, gully size, and local economy. Bioengineering techniques in Northeast China, such as continuous live wicker, a shrub plant enclosure, and an arbor plant enclosure, are highly effective in controlling gully erosion. Problems and challenges are also presented.