Effects of plastic film mulching on soil greenhouse gases(CO2,CH4 and N2O) concentration within soil profiles in maize fields on the Loess Plateau,China

To better understand the effects of plastic film mulching on soil greenhouse gases（GHGs） emissions,we compared seasonal and vertical variations of GHG concentrations at seven soil depths in maize（Zea mays L.） fields at Changwu station in Shaanxi,a semi-humid region,between 2012 and 2013.Gas samples were taken simultaneously every one week from non-mulched（BP） and plastic film-mulched（FM） field plots.The results showed that the concentration of GHGs varied distinctly at the soil-atmosphere interface and in the soil profile during the maize growing season（MS）.Both carbon dioxide（CO_2） and nitrous oxide（N_2O） concentrations increased with increasement of soil depth,while the methane（CH_4）concentrations decreased with increasement of soil depth.A strong seasonal variation pattern was found for CO_2 and N_2O concentrations,as compared to an inconspicuous seasonal variation of CH_4 concentrations.The mean CO_2 and N_2O concentrations were higher,but the mean CH_4 concentration in the soil profiles was lower in the FM plots than in the BP plots.The results of this study suggested that plastic film mulching significantly increased the potential emissions of CO_2and N_2O from the soil,and promoted CH_4 absorption by the soil,particularly during the MS.

Application of Mulching Materials of Rainfall Harvesting System for Improving Soil Water and Corn Growth in Northwest of China

The ridge and furrow rainfall harvesting（RFRH） system is used for dryland crop production in northwest of China.To determine the effects of RFRH using different mulching materials on corn growth and water use efficiency（WUE）,a field experiment was conducted during 2008-2010 at the Heyang Dryland Experimental Station,China.Four treatments were used in the study.Furrows received uncovered mulching in all RFRH treatments whereas ridges were mulched with plastic film（PF）,biodegradable film（BF） or liquid film（LF）.A conventional flat field without mulching was used as the control（CK）.The results indicated that the average soil water storage at depths of 0-200 cm were 8.2 and 7.3%,respectively higher with PF and BF than with CK.However,LF improved soil water storage during the early growth stage of the crop.Compared with CK,the corn yields with PF and BF were increased by 20.4 and 19.4%,respectively,and WUE with each treatment increased by 23.3 and 21.7%,respectively.There were no significant differences in corn yield or WUE with the PF and BF treatments.The net income was the highest with PF,followed by BF,and the 3-yr average net incomes with these treatments were increased by 2 559 and 2 430 CNY ha-1,respectively,compared with CK.BF and PF had similar effects in enhancing the soil water content,crop yield and net income.Therefore,it can be concluded that biodegradable film may be a sustainable ecological alternative to plastic film for use in the RFRH system in northwest of China.

Allelopathic Potential of Orange Jessamine （Murraya paniculata L.） against Weeds

The use of allelopathic plants is an alternative technique for controlling weeds in sustainable crop production. This experiment evaluated the allelopathic potential of Murraya paniculata （L.） against four weeds viz., Bidens pilosa L., Amarathus spinosus L., Echinochloa crusgalli （L.） Beauv. and Chloris barbata Sw.. In laboratory test, aqueous extracts from M. paniculata leaves at concentrations of 12.5, 25, 50 and 100 g/L were tested on germination and seedling growth of the weeds. The extracts showed inhibitory effect, varying with weed species and extract concentration. Increase in concentrations increased the degree of inhibition. Concentration at 50 g/L and 100 g/L, completely inhibited seed germination of C. barbara and A. spinosus. Pot experiments were done in a glasshouse, with dry leaf powder as mulch on the soil surface at levels of 2, 4 and 8 t/ha. Dry leaf powder reduced the emergence and growth of all tested weeds, varying with dose and species. Chloris barbara is the most sensitive to M paniculata leaf mulch while E. crus-galli is the most resistant. These results suggest that M. paniculata had the potential lbr weed control and might be the source of a natural herbicide.

Environmental behaviors of phoxim with two formulations in bamboo forest under soil surface mulching

Phoxim（emulsifiable concentrate（EC） and granules（G）） has been widely used in bamboo forests. The persistence and magnitude of phoxim residues in the crop and soil must be investigated to ensure human and environmental safety. The environmental behaviors of the two formulations were investigated in a bamboo forest under soil surface mulching conditions（CP） and non-covered cultivation conditions（NCP）. The half-lives of phoxim in soil under the two conditions in soil were 4.1–6.2 days（EC） and 31.5–49.5 days（G）,respectively. Phoxim in EC could be leached from the topsoil into the subsoil. A minimized leaching effect was observed for G under NCP. Inversely, an enhanced leaching effect was observed for G under CP. The G formulation resulted in more parent compound（in bamboo shoots） and metabolite（in soil） residues of phoxim than in the case of EC, especially under CP conditions. In addition, the intensity and duration of the formulation effect on soil p H adjustment from G were more obvious than that from EC. Results showed that the environmental behaviors（distribution, degradation, residue） of phoxim in the bamboo forest were significantly influenced by the type of formulation. The prolongation effect from phoxim G might cause persistence and long-term environmental risk. However,bamboo shoot consumption could be considered relatively safe after applying the recommended dose of the two phoxim formulations.