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Great efforts have been made on the assessment of the effects of straw managements or tillage practices on rice yield and greenhouse gas (GHG) emissions. However, their interactive effects were not well documented. Based on a seven-year field experiment under a double rice system, we tested the effects of rotary tillage (RT) vs. plough tillage (PT) on rice yield, methane (CH 4 ) and nitrous oxide (N 2 O) emissions with or without straw incorporation. As compared to straw removal, straw incorporation increased rice yield by 12.7% and 1.3% under the PT and the RT, respectively. Straw incorporation significantly stimulated CH 4 emissions under both tillage regimes in the late rice season, while no significant effect occurred in the early rice season. Compared to the RT, PT significantly decreased DOC concentrations and methanogen abundances, resulting in a reduction in CH 4 emission. The PT decreased yield-scaled global warming potential (GWP) with or without straw incorporation by 31.0% and 15.5%, respectively, as compared to the RT. Together, our results indicate that straw incorporation with plough tillage benefits rice production for higher-yield with less GHG emissions in double rice cropping areas. [ABSTRACT FROM AUTHOR]

Mechanical planting is replacing manual transplanting in the major Asian rice cropping areas, however, few are known about the impacts of mechanical planting on rice yield and greenhouse gas (GHG) emission. Therefore, a two-year experiment was conducted to examine the impacts of dry direct-seeding (MDS), wet direct-seeding (MWS) and transplanting (MTP) in Jianghuai area, China. The results showed that CH 4 emission was significantly lower in the MDS than the MWS and MTP both with and without straw incorporation. No significant difference in N 2 O emission was found among the planting methods. Straw incorporation significantly stimulated CH 4 emission in the MWS and MTP, but not in the MDS. The lowest rice yield was found in the MWS, while there was no significant difference in grain yield between the MDS and MTP methods. The area-scaled emission of CH 4 and N 2 O in CO 2 -equivalent unit was respectively 78.5 and 89.6% lower in the MDS than those in the MWS and MTP without straw incorporation, and 87.7 and 94.1% lower with straw incorporation. The yield-scaled emission was correspondingly 80.4 and 88.1% lower without straw incorporation, and 89.0 and 93.4% lower with straw incorporation, respectively. Our results indicate that MDS can get an acceptable yield with a large reduction in GHGs emissions in the test location. [ABSTRACT FROM AUTHOR]

A high-temperature Ti-6.8Al-6.8Zr-2.3V-2.1Mo-0.7Nb alloy suitable for laser additive manufacturing is designed on the basis of the cluster formula of Ti–6Al–4V, composed of twelve α-[Al–Ti 12 ](AlTi 2) units and five β-[Al–Ti 12 Zr 2 ](AlV 1.2 Mo 0.6 Nb 0.2) ones, featuring enhanced β stability via Zr, Mo, Nb, and V co-alloying. Using pre-alloyed powders, this alloy shows a fine surface roughness about 83 μm, which is comparable to that of reported Ti–6Al–4V. The as-deposited alloy exhibits a typical bimodal basket-weave microstructure and superior mechanical properties at room temperature (ultimate tensile strength (UTS) of 1348 MPa, yield strength (YS) of 1253 MPa, and elongation of 4.4%) as well as at 600 °C (UTS of 657 MPa, YS of 578 MPa, and elongation of 44.6%), which are comparable to wrought-state high-temperature Ti alloys. At 650 °C, its UTS of 424 MPa and YS of 337 MPa still maintains a high level. [ABSTRACT FROM AUTHOR]

Breeding high-yielding rice cultivars through increasing biomass is a key strategy to meet rising global food demands. Yet, increasing rice growth can stimulate methane ( CH4) emissions, exacerbating global climate change, as rice cultivation is a major source of this powerful greenhouse gas. Here, we show in a series of experiments that high-yielding rice cultivars actually reduce CH4 emissions from typical paddy soils. Averaged across 33 rice cultivars, a biomass increase of 10% resulted in a 10.3% decrease in CH4 emissions in a soil with a high carbon (C) content. Compared to a low-yielding cultivar, a high-yielding cultivar significantly increased root porosity and the abundance of methane-consuming microorganisms, suggesting that the larger and more porous root systems of high-yielding cultivars facilitated CH4 oxidation by promoting O2 transport to soils. Our results were further supported by a meta-analysis, showing that high-yielding rice cultivars strongly decrease CH4 emissions from paddy soils with high organic C contents. Based on our results, increasing rice biomass by 10% could reduce annual CH4 emissions from Chinese rice agriculture by 7.1%. Our findings suggest that modern rice breeding strategies for high-yielding cultivars can substantially mitigate paddy CH4 emission in China and other rice growing regions. [ABSTRACT FROM AUTHOR]

Many efforts have been made to learn the fertilization effects on greenhouse gas (GHG) emissions in the current crop season of multiple cropping systems, however, residual effects on the succeeding crop season are not clear. Based on a thirty-year fertilization experiment, we investigated the impacts of wheat fertilization on GHG emissions in the succeeding soybean season. There were five fertilization regimes for the wheat-soybean cropping system, including sole organic manure (M), balanced chemical NPK fertilizer (NPK), chemical NPK plus manure (NPKM), chemical NP plus wheat straw (NPS), and no fertilizer application (CK). Fertilization significantly affected GHG emissions not only in the current fertilizing season of winter wheat but also in the non-fertilizing season of summer soybean. Compared to the NPK treatment, the M and NPKM treatments stimulated annual soil CO 2 and N 2 O emissions, and reduced CH 4 emissions. The M and NPKM treatments also significantly increased soil organic C and total N contents, soil microbial biomass C and N, and NH 4 N and NO 3 N concentrations, especially in the soybean season. Although fertilizers were only applied in wheat season, the emissions of CO 2 and N 2 O were higher in the soybean season. At the cropping system scale, the treatments of M and NPKM significantly increased annual global warming potential (GWP) by 75.5% and 38.3%, respectively, compared to the NPK. Sole manure application (M) significantly increased greenhouse gas intensity (GHGI) in comparison with the NPK, while there was no significant increment in the GHGI caused by the treatments of chemical fertilizer plus manure (NPKM) and crop straw (NPS). [ABSTRACT FROM AUTHOR]

Developing large rice ( Oryza sativa L.) panicles has been widely regarded as an effective approach to increasing rice yield. However, it is unclear whether panicle size affects CH emissions from rice fields, especially during the reproductive stage. Here, we conducted two experiments (rice variety and mutant) to examine the effects of rice panicle size on CH emissions. The variety experiment under field conditions at two sites showed that rice yield was significantly and positively correlated with the spikelet number. Mean CH emissions during the reproductive stage were significantly and negatively correlated with spikelet number. The rice mutant experiment under pot and field conditions using a wild-type rice variety (WT) and its mutant (Mutant) demonstrated that CH emissions were significantly lower in the former with large panicles than in the later with small panicles, during the reproductive and grain filling stages ( P < 0.01), whereas the rice yields showed an opposite. Root exudates and soil dissolved organic C concentration were significantly lower under the WT than under the Mutant. Soil CH production potential and mcrA gene copy number of the soil under Mutant were significantly higher than those of the soil under WT. There was no significant difference in soil CH oxidation potential and pmoA gene copy number between soils of these two rice varieties. Our results suggest that developing large panicles would benefit rice production for high yield with low CH emission. [ABSTRACT FROM AUTHOR]

High-yield varieties with low methane emissions will benefit sustainable rice ( Oryza sativa L.) production. However, no specific plant characteristics have been identified to be primarily responsible for rice variety impacts on the CH 4 emission. We conducted a comprehensive study through comparing effects of 66 varieties on CH 4 under both greenhouse and field conditions to identify rice plant characteristics that may significantly affect soil CH 4 emission. Although there were significant differences in CH 4 emissions among the tested rice varieties, no significant and consistent relationships were observed between aboveground traits and CH 4 fluxes or dissolved CH 4 concentrations in soil solutions. Yet dissolved CH 4 concentrations were significantly correlated with the mean CH 4 flux over the growing season. In addition, cutting rice plants 5 cm off above the floodwater did not increase CH 4 fluxes, indicating that the CH 4 transport through the removed part of rice plant contributed little to the total CH 4 emission. Taken together, our results indicate that differences in CH 4 emissions among rice varieties primarily stem from the differential effects of rice plants on the belowground CH 4 production and oxidation. Aboveground plant traits do not provide reliable predictions of variety effects on CH 4 emissions. Future efforts should be focused on understanding belowground processes and the underlying mechanisms that govern rice variety impacts on the CH 4 emission. [ABSTRACT FROM AUTHOR]

The vegetation cover during the non-cropping season could have important implications for the maintenance and recovery of soil fertility, as well as for biodiversity conservation in croplands. In this study, five fertilization regimes (control: non-fertilization; N: inorganic N fertilization; P: inorganic P fertilization; NPK: balanced fertilization with inorganic N, P and K; NPKM: balanced NPK plus farmyard manure) were conducted from 1981 in a double-rice ( Oryza sativa L.)-cropping system in subtropical China. The effects of long-term fertilization were investigated on the weed growth, diversity and community structure during the fallow period. The results showed that, relative to the control, both inorganic fertilization alone ( N, P and NPK) and NPKM in the rice-growing season significantly increased the weed density and biomass during the fallow period in the paddy field. There was no significant difference in the weed species richness (the number of species) among the treatments. Compared with the control, fertilization tended to reduce the weed diversity ( Shannon's H′) and evenness ( Shannon's E), especially in the N treatment. Long-term fertilization resulted in a significant shift in weed community's composition during the fallow period. The weed community's structure was affected by soil nutrients in the order P > N > K. [ABSTRACT FROM AUTHOR]