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BACKGROUND Crop residue management and nitrogen loss are two important environmental problems in the rice-wheat rotation system in China. This study investigated the effects of burial of straw on water percolation, nitrogen loss by leaching, crop growth and yield. Greenhouse mesocosm experiments were conducted over the course of three simulated cropping seasons in a rice1-wheat-rice2 rotation. RESULTS Greater amounts of straw resulted in more water percolation, irrespective of crop season. Burial at 20 and 35 cm significantly reduced, but burial at 50 cm increased nitrogen leaching. Straw at 500 kg ha−1 reduced, but at 1000 kg ha−1 and at 1500 kg ha−1 straw increased nitrogen leaching in three consecutive crop rotations. In addition, straw at 500 kg ha−1 buried at 35 cm significantly increased yield and its components for both crops. CONCLUSIONS This study suggests that N losses via leaching from the rice-wheat rotation may be reduced by the burial of the appropriate amount of straw at the appropriate depth. Greater amounts of buried straw, however, may promote nitrogen leaching and negatively affect crop growth and yields. Complementary field experiments must be performed to make specific agronomic recommendations. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Naturally, simultaneous interactions occurred among plants, herbivores, and soil biota, that is, arbuscular mycorrhizal fungi (AMF), nematodes, and fungal pathogens. These multiple interactions play fundamental roles in driving process, structure, and functioning of ecosystems. In this study, we conducted a meta-analysis with 144 papers to investigate the interactions between AMF and plant biotic stressors and their effects on plant growth performance. We found that AMF enhanced plant tolerance to herbivores, nematodes, and fungal pathogens. We also found reciprocal inhibition between AMF and nematodes as well as fungal pathogens, but unidirectional inhibition for AMF on herbivores. Negative effects of AMF on biotic stressors of plants depended on herbivore feeding sites and actioning modes of fungal pathogens. More performance was reduced in root-feeding than in shoot-feeding herbivores and in rotting- than in wilt-fungal pathogens. However, no difference was found for AMF negative effects between migratory and sedentary nematodes. In return, nematodes and fungal pathogens generated more reduction of root colonization in Non-Glomeraceae than in Glomeraceae. Our results suggested that AMF positive effects on plants might be indirectly mediated by competitive inhibition with biotic stressors of plants. These positive and negative interactions make potential contributions to maintaining ecosystem stability and functioning. [ABSTRACT FROM AUTHOR]

Drip irrigation is broadly extended in order to save water in the arid cotton production region of China. Biochar is thought to be a useful soil amendment to reduce greenhouse gas (GHG) emissions. Here, a field study was conducted to compare the emissions of nitrous oxide (N2O) and methane (CH4) under different irrigation methods (drip irrigation (D) and furrow irrigation (F)) and fertilization regimes (conventional fertilization (C) and conventional fertilization + biochar (B)) during the cotton growth season. The accumulated N2O emissions were significantly lower with FB, DC, and DB than with FC by 28.8%, 36.1%, and 37.6%, while accumulated CH4 uptake was 264.5%, 226.7%, and 154.2% higher with DC, DB, and FC than that with FB, respectively. Irrigation methods showed a significant effect on total global warming potential (GWP) and yield-scaled GWP (P < 0.01). DC and DB showed higher cotton yield, water use efficiency (WUE), and lower yield-scaled GWP, as compared with FC and FB. This suggests that in northwestern China mulched-drip irrigation should be a better approach to increase cotton yield with depressed GHG. In addition, biochar addition increased CH4 emissions while it decreased N2O emissions. [ABSTRACT FROM AUTHOR]

A novel straw return method (ditch-buried straw return, DB-SR) with a four-year field experiment was implemented to investigate the carbon sequestration effect under various burial depths and with different amounts in a rice–wheat rotation system. The DB-SR significantly increased the soil total organic carbon (TOC) and labile organic carbon (LOC) contents. In the two soil layers 10 cm above and below the straw layer, the TOC and LOC levels increased. The DB-SR treatment using the total amount of straw showed higher TOC, LOC and carbon pool management index (CPMI) values than when half and twice the amount of straw were used. The rice yield was significantly higher when the total amount was used with the DB-SR to depth of 20 cm than at other soil depth treatments. However, the DB-SR with twice the amount showed a negative, but not significant, effect on rice yields. These results suggest that DB-SR might be a better straw return method to increase soil organic carbon (SOC) and improve soil quality, particularly when returning the total amount of straw to a soil depth of 20 cm. [ABSTRACT FROM AUTHOR]

Abstract: Increasing evidences have shown that dissolved organic components are responsible for the significant C and N exports from terrestrial ecosystems to the surrounding aquatic ecosystems and very sensitive to CO2 enrichment. However, there is still a lack of direct evidence about CO2-led effects on these components at the ecosystem scale, especially in wetlands. We, therefore, simultaneously investigated the contents of dissolved organic carbon (DOC) and dissolved nitrogen (DN) in the surface water and soil layer in a paddy field under FACE facility in Eastern China. Elevated CO2 significantly increased the contents of DOC and DN in the surface water by 18.0% and 14.3% on average. Elevated CO2 also increased DOC content in the soil, but decreased DN content. The contents of DOC and DN in the soil–water interface of 0–1cm soil layer were on average 22.4% and 47.5% higher than in the 5–15cm soil layer. Besides, significant higher DOC and DN contents existed in the soil porewater than in the surface water. Due to multiple drainage regime and rainstorm-induced runoffs in rice cropping regions, CO2-led DOC and DN increments in the surface water may increase C and N exports from paddies to the surrounding aquatic ecosystems under future climate patterns. [Copyright &y& Elsevier]