Fumigation is a widely applied approach to mitigate the soil-borne diseases.  However, the potential effects of currently applied fumigants on ammonification remain unclear.  An 84-day incubation experiment was conducted based on non-fumigated soil (CK) and fumigated soil using three common fumigants, i.e., chloropicrin (CP), 1,3-dichloropropene (1,3-D), and metam sodium (MS).  The results showed that, the three fumigants all decreased the microbial C, and the largest reduction (84.7%) occurred with the application of CP.  After fumigation, the microbial diversity in the CP treatment rapidly recovered, but that in the 1,3-D treatment decreased and did not recover by the end of the experiment.  The application of MS showed no impact on the microbial diversity during the assay, indicating that significantly different microbial diversity can be achieved by choosing different fumigants.  Furthermore, the three fumigants showed divergent effects on the enzymes involved in ammonification.  The analysis showed that the enzyme variation with CP application was mainly associated with the changed microbial C and N (P<0.05), and not with the microbial community, which was different from the observed effects of 1,3-D or MS application.  In addition, the soil quality index showed that CP was still significantly harmful at the end of incubation compared with the good resilience of MS, indicating that CP may not be a suitable fumigant.

Five crop straws (wheat, rice, maize, oil-rape, and cotton) were first steam-exploded for 2 min at 210°C, 2.5 MPa and then pyrolyzed at 500°C for 2 h.  Steam explosion (SE) induced 47–95% and 5–16% reduction of hemicellulose and cellulose, respectively, in the crop straws.  The biochars derived from SE-treated feedstocks had a lower specific surface area (SSA) and pore volume, compared to those from pristine feedstocks, with one exception that SE enhanced SSA of oil-rape straw biochar by approximately 16 times.  After SE, biochars had significant higher anion exchange capacity (AEC) (6.88–11.44 cmol kg^–1) and point of zero net charges (PZNC) (pH 3.61–5.32) values.  It can thus be speculated that these biochars may have higher potential for anions adsorption.  In addition, oil-rape straw might be suitable to SE pretreatment for preparing biochar as a soil amendment and sorbent as well.  Further work is required for testing its application in soil.

 

It is not certain that long-term grazing exclusion influences arbuscular mycorrhizal (AM) fungi and their association with steppe vegetation.  In this study, soil and plant samples were collected from two sites of grazing exclusion since 1983 (E83) and 1996 (E96), and one site of free-grazing (FG) in the typical steppe of Xilinguole League, Inner Mongolia, China, and assayed for soil basic physicochemical properties, AM fungal parameters, aboveground biomass and shoot phosphorus (P) uptake as well.  The results showed that long-term grazing exclusion of E83 and E96 led to less drastic seasonal changes and significant increases in spore density, hyphal length density and root colonization intensity of AM fungi and even soil alkaline phosphatase activity, by up to 300, 168, 110 and 102%, respectively, compared with those of FG site.  In addition, the total aboveground biomass and shoot P uptake of E83 and E96 were 75–992% and 58–645%, respectively, higher than those of FG.  Generally, the root colonization intensity, spore density, and hyphal length density of AM fungi were all positively correlated with the aboveground biomass and even shoot P uptake of plant.  These results may imply that grazing exclusion play a critical role in increasing the growth of AM fungi, and subsequently, may increase plant P uptake and aboveground biomass production.  Moreover, the spore density could sensitively reflect the impacts of long-term grazing exclusion on AM fungi since survival strategy of spores in soil.