Soil Quality in Relation to Agricultural Production in the North China Plain

Sustainable agricultural production is of vital importance to food supply security. This study aimed to investigate crop yield response to spatial variability of soil quality at a county scale in the North China Plain （NCP） and subsequently derive key soil quality indicators. Soil samples were geo-referenced and taken in 2008 from both surface （0-20 cm） and subsurface （20-40 cm） layers in 132 fields throughout the Fengqiu County, located in the centre of the NCP, for subsequent soil properties＇ analyses. Annum crop yields were obtained from the same fields where soil samples were collected. Soil quality was evaluated based on a fuzzy set with 13 soil properties, and its spatial distributions were investigated by integrating geostatistical analysis and geographic information system （GIS） techniques. Soil quality indices were classified into five grades, and their spatial distributions were mapped within the county. The surface soil qualities were about one to two grades higher than the subsurface soil. The quality indices for surface and subsurface soils were positively associated with the annual crop yields, suggesting the importance of both. Soil organic matter, total nitrogen, available P, and available K contributed 50% of the combined weight to the soil quality index and were identified as key indicators of soil quality status in the area in terms of sustainability.

Nutrient cycling and greenhouse gas emissions from soil amended with biochar-manure mixtures

Integrating biochar into cattle diets has recently emerged as a potential management practice for improving on-farm productivity.Yet,information concerning the cycling of biochar-manure mixtures is scarce.A 70-d incubation experiment was conducted within two surface(0–15 cm)Mollisols with contrasting textures,i.e.,sandy clay loam(Raymond)and clayey(Lethbridge),to evaluate the effects of biochar(3 Mg ha^(-1))on cumulative greenhouse gas(GHG)emissions and related fertility attributes in the presence or absence of cattle manure(120 Mg ha^(-1)).Five treatments were included:i)non-amended soil(control,CK),ii)soil amended with pinewood biochar(B),iii)soil amended with beef cattle manure(M)(manure from cattle on a control diet),iv)soil amended with biochar-manure(BM)(manure from cattle on a control diet,with pinewood biochar added at 20 g kg^(-1)of diet dry matter),and v)soil amended with B and M at the aforementioned rates(B+M).A total of 40 soil columns were prepared and incubated at 21℃and 60%–80%water-holding capacity.On average,total CO_(2)fluxes increased by 2.2-and 3.8-fold under manure treatments(i.e.,M,BM,and B+M),within Raymond and Lethbridge soils,respectively,relative to CK and B.Similarly,total CH4 fluxes were the highest(P<0.05)in Raymond soil under B+M and BM relative to CK and B,and in Lethbridge soil under M and BM relative to CK and B.In Lethbridge soil,application of BM increased cumulative N_(2)O emissions by 1.8-fold relative to CK.After 70-d incubation,amendment with BM increased(P<0.05)PO_4-P and NO_3-N+NH_4-N availability in Raymond and Lethbridge soils compared with B.A similar pattern was observed for water-extractable organic carbon in both soils,with BM augmenting(P<0.05)the occurrence of labile carbon over CK and B.It can be concluded that biochar,manure,and/or biochar-manure have contrasting short-term effects on the biogeochemistry of Mollisols.At relatively low application rates,biochar does not necessarily counterbalance manure-derived inputs.Although BM did not mitigate the flux of GHGs over M,biochar-manure has the potential to recycle soil nutrients in semiarid drylands.

Greenhouse gas emissions during co-composting of cattle feedlot manure with construction and demolition （C＆D） waste

Manure management strategies should reflect current animal feeding practices and encourage recycling of organic waste to help protect our environment. This research investigated greenhouse gas （GHG） emissions during cattle manure stockpiling or composting with and without construction and demolition （C＆D） waste. Manure was collected from cattle fed a typical finishing diet （CK manure） and from cattle on diets which included 30% dried distillers grains with solubles （DG manure）. The CK and DG manures were co-composted with （4：1） C＆D waste （treatments： CK CD, DG CD）, composted alone （treatments： CK and DG） in 13 m3 bins or stockpiled without C＆D ~vaste （treatments： CK ST and DGST） for 99 days. Manure type （CK vs. DG manure） had no effect on GHG emissions-over the 99 day manure composting or stockpiling. Composting with C＆D waste 2 produced similar CO2 emissions, about double that from manure stockpthng （7.9 kgC.m^-2）. In contrast, CH4 emissions were reduced by the inclusion of C＆D waste （64 gC.m^-1 with C＆D vs. 244 gC.m 2 without C＆D） while the manure stockpile emitted the greatest amount of CH4 （464 gC. m 2）. Additionally, only 0.48% of C was emitted in CH4 form with C＆D waste, compared to 1.68% when composting without C＆D waste and 7.00% when cattle manure was stockpiled. The N2O emissions （12.4 to 18.0 gN.m ） were similar across all treatments. The lower CH4 emissions with C＆D waste are beneficial in reducing overall GHG emissions from manure composting, while reducing the amount of material entering landfills.