Water resource potential for large-scale sweet sorghum production as bioenergy feedstock in Northern China.

This study investigated the water resource potential for bioenergy production from sweet sorghum (Sorghum bicolor (L.)) in Northern China according to the distribution of water resources, climate conditions and the total water consumption of bioenergy based on sweet sorghum, which consisted of blue water, green water and grey water. At a case study site in Inner Mongolia, simulation with a plant phenological model was used to determine whether sweet sorghum could reach the harvestable stage for sugar juice production. The blue water in the agricultural phase was estimated according to the potential crop evapotranspiration (ETc), the drought sensitivity of sweet sorghum in different stages and the precipitation during the growing season. The results showed that the irrigation water was significantly different among the districts, ranging from 730 to 5500 m3/ha and 2060 to 6680 m3/ha for early-maturing and late-maturing varieties, respectively. To avoid the water pressure level to be exacerbated and the severe reallocation of water resources resulting in negative effects on other sectors, the maximal annual water withdrawal was set to not surpass the upper threshold of water stress level of 40%. That makes the maximum area for the production of sweet sorghum cannot exceed 1.95 × 104 ha, representing only 0.24% of the total marginal land area in Inner Mongolia. However, the economic benefits of bioenergy production from sweet sorghum would be negative due to the high labour input. Therefore, not only the availability of marginal land, the climate conditions and local water resources but also the improvement of mechanisation and agricultural production techniques should be considered to attain the sustainable development of bioenergy production and address global energy and environmental crises.

Assessment of promising agricultural management practices.

iSQAPER project - Interactive Soil Quality Assessment in Europe and China for Agricultural Productivity and Environmental Resilience - aims to develop an app to advise farmers on selecting the best Agriculture Management Practice (AMPs) to improve soil quality. For this purpose, a soil quality index has to be developed to account for the changes in soil quality as impacted by the implementation of the AMPs. Some promising AMPs have been suggested over the time to prevent soil degradation. These practices have been randomly adopted by farmers but which practices are most used by farmers and where they are mostly adopted remains unclear. This study is part of the iSQAPER project with the specific aims: 1) map the current distribution of previously selected 18 promising AMPs in several pedo-climatic regions and farming systems located in ten and four study site areas (SSA) along Europe and China, respectively; and 2) identify the soil threats occurring in those areas. In each SSA, farmers using promising AMP's were identified and questionnaires were used to assess farmer's perception on soil threats significance in the area. 138 plots/farms using 18 promising AMPs, were identified in Europe (112) and China (26).Results show that promising AMPs used in Europe are Crop rotation (15%), Manuring & Composting (15%) and Min-till (14%), whereas in China are Manuring & Composting (18%), Residue maintenance (18%) and Integrated pest and disease management (12%). In Europe, soil erosion is the main threat in agricultural Mediterranean areas while soil-borne pests and diseases is more frequent in the SSAs from France and The Netherlands. In China, soil erosion, SOM decline, compaction and poor soil structure are among the most significant. This work provides important information for policy makers and the development of strategies to support and promote agricultural management practices with benefits for soil quality.

Combinations of soil properties, carbon inputs and climate control the saturation deficit dynamics of stable soil carbon over 17-year fertilizaiton.

The soil organic carbon (SOC) saturation deficit (Csd) of silt and clay fractions represents the potential for SOC sequestration in a stable form and can influence organic C stabilization efficiency. Little is known, however, about temporal changes of stable soil Csd and how it is affected by soil properties, climate and C inputs. We investigated the temporal changes in the Csd of fine fractions (<53 µm) and examined the factors controlling these changes at three dry-land sites with 17-year fertilizer management histories in China. The rates of change in the stable soil Csd under manure treatments varied from -0.72 to -1.24% yr-1 after 17 years of fertilization, indicating that stable C levels under manure treatments were significantly higher than those under other treatments. Stable soil Csd was controlled by a combination of soil properties, temperature, and C inputs at all sites, and the higher variance of Csd of fine fractions can be explained by the soil properties (up to 50%). Furthermore, the quantity of C inputs was the most influential variable for stable soil Csd. These results revealed key controls on stable C sequestration potential and indicated the need to develop management strategies to promote stable C sequestration under long-term intensive fertilization.