Soil respiration is an important component of the carbon cycle and is also recognized as one of the primary pathways that release CO₂ from the soil into the atmosphere in terrestrial ecosystems. Soil CO₂ flux resulting from soil microbial activity and root respiration is one of the major components of the total carbon flux in agro-ecosystems. However, the impact of agronomic practices such as mulching on soil respiration in greenhouses has been less thoroughly studied. Consequently, field experiments were conducted during the growing seasons of 2011 and 2012 in greenhouse to evaluate soil respiration and the biotic and abiotic factors that influence it in hot pepper cultivation under four types of mulch practices (without mulch, wheat straw mulch, plastic film mulch, and combined mulch with plastic film and wheat straw). Soil water content had an overriding influence on soil respiration in hot pepper culture during the growing season under mulching treatments in a greenhouse, whereas the influence of soil temperature was relatively less. Additionally, the study showed that root biomass and root vigor should also be incorporated as predictor variables for soil respiration under mulching in greenhouses.

Soil degradation has been a very serious problem for sustainable production, especially by a re-cropping of greenhouse-cultivated cucumber (Cucumis statirus L.). The aim of this research was to expound the actuality for soil degradation, at the same time, put forward some suggestion for preventing from soil degradation and maintain sustainable production in greenhouse basic on the two experiments conducted in a solar greenhouse during 2001-2008 suburb area of Yan'an, Shaanxi province in North China. The result shown that cucumber fruit productivity increased as the increasing of re-cropping years, but decreased after 5years continuously cropping. As increasing of re-cropping years, the population of fungus and bacteria increased, which was assumingly main factor of soil degradation. There was significant difference in cropping models on soil bio-characteristics and system productivity. The productivity were the highest in cropping model between cucumber and greengrocery, cucumber and cowpea (Vigna sinensis L), the second higher were in cropping model between cucumber and maize (Zea mays) for green manure, cucumber and kidney bean (Phaseolus vulgaris). That was the best way to reduce soil bacteria and epiphyte amount to follow lasting three or four months during summer season after cucumber harvest, the better method was planting cowpea or other leguminous crops. Basic on the experiment, the optimums approaches to preventive soil degradation were put forward.

The conversion of farmland to forestland not only changes the ecological environment but also enriches the soil with organic matter and affects the global carbon cycle. This paper reviews the influence of land use changes on the soil organic carbon sink to determine whether the Chinese “Grain-for-Green” (conversion of farmland to forestland) project increased the rate of SOC content during its implementation between 1999 and 2010 in the hilly and gully areas of the Loess Plateau in north-central China. The carbon sink was quantified, and the effects of the main species were assessed. The carbon sink increased from 2.26×10⁶ kg in 1999 to 8.32×10⁶ kg in 2010 with the sustainable growth of the converted areas. The black locust (Robinia pseudoacacia L.) and alfalfa (Medicago sativa L.) soil increased SOC content in the top soil (0–100 cm) in the initial 7-yr period, while the sequestration occurred later (>7 yr) in the 100–120 cm layer after the “Grain-for-Green” project was implemented. The carbon sink function measured for the afforested land provides evidence that the Grain-for-Green project has successfully excavated the carbon sink potential of the Shaanxi province and served as an important milestone for establishing an effective organic carbon management program.

Selenium (Se) deficiency in humans could be improved by biofortification of food with selenium, 1-Methylcyclopropene (1-MCP) treatment is beneficial for the non-sulfur storage of fresh fruit. This study investigated fruit quality of table grape (Hutai No.8) with foliar Se fertilizer at maturity, and fruit quality changes of table grape during shelf life stages that caused by postharvest 1-MCP treatment in 2016 and 2017. The results showed that foliar Se fertilizer application significantly increased Se content in grape berries at maturity, and the raised rate were 43.09% and 33.24% compared to that of control in 2016 and 2017 respectively, meanwhile it increased the nutritional components in grape berries, including soluble proteins, soluble sugars, Vitamin C, total soluble solids, proanthocyanidin content and so on, and decreased the titratable acidity content. During shelf life stages, 1-MCP application decreased the decay number of grapes, and SE + 1-MCP treatment had the most excellent fruit quality among all treatments in two consecutive vintages. In conclusion, Se fertilizer application could increase Se content in grape berries, also improved the fruit nutritional and health care values at maturity. 1-MCP application could delay the process of ripening and senescence for Se-enriched grape and maintaining the postharvest quality of table grape during shelf life stages, it allows us to market the fruit at a more advanced ripening stage without quality loss.

To understand the response of grape (Hutai No.8) quality and soil respiration (R_s) to different soil relative water contents (SRWCs), this study was designed with three soil moisture levels (A: 80–95%, B: 60–75%, and C: 40–55% of SRWC) for grape cultivation. Meanwhile, environmental factors, including air temperature (T_a), air relative humidity, and light intensity, were also recorded. The results showed the following: (1) Through the comprehensive analysis of fruit quality by the method of subordinate function, we concluded that the optimum soil moisture treatment was 60–75% SRWC, and the soluble sugars, proanthocyanidin, and resveratrol were most abundant. In addition, vitamin C (Vc) content was the largest under C treatment. (2) Photosynthetic characteristic under high soil moisture was better than those under low soil moisture condition during grape coloring periods, and it was largest under A treatment in 2015. R_s rate was in accordance with the trend of grape photosynthesis. High soil moisture could accelerate the photosynthetic rate of grape leaves and increase R_s. (3) Correlation analysis showed that higher soil moisture and air humidity and lower soil temperature (T_s) and T_a could promote the accumulation of more nutrients in grape berries; it also could increase photosynthetic rate and R_s during grape coloring periods. In conclusion, 60–75% SRWC was the optimum soil moisture condition, which could improve the nutrient contents and accumulate more bioactive substances. Of course, keeping a lower T_s and T_a, as well as higher air humidity, was also necessary. Abbreviations: SRWC: soil relative water content; A, 90-95% SRWC; B, 70-75% SRWC; C, 40-55% SRWC; Rs: soil respiration; Ta: air temperature; Ts: soil temperature; OPC: proanthocyanidin; TSS: total soluble solids.