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Rice cultivation consumes more than half of the planet's 70% freshwater supply used in agricultural production. Competing water uses and climate change globally are putting more pressure on the limited water resources. Therefore, water-saving irrigation (WSI) is recommended for rice production in water scares areas. The impact of WSI techniques on direct-seeding rice production and greenhouse gas emissions in North China is becoming increasingly important in the era of climate change. Therefore, we conducted a two-year field experiment on directly seeded rice to assess the impact of traditional flooding irrigation (CK) and three water saving irrigation (WSI) methods, including drip irrigation with an irrigation amount of 50 mm (DI1) and 35 mm (DI2) at each watering time and furrow wetting irrigation (FWI), on rice yield and greenhouse emissions. Generally, the WSI techniques decreased the number of rice panicles per m−2, spikelet per panicle, 1000-grain weight and rice yield compared to CK. Rice yield and yield components of (DI1) were significantly higher than (DI2). The adoption of either (DI1) or (FWI) showed insignificant variation in terms of rice yield and its yield components measured except for 1000-grain weight. The water productivity was 88.9, 16.4 and 11.4% higher in the FWI plot than the CK, DI1 and DI2 plots, respectively. The WSI decreased cumulative CH4 emission significantly by 73.0, 84.7 and 64.4% in DI1, DI2 and FWI, respectively, in comparison with CK. The usage of DI2 triggered 1.4 and 2.0-fold more cumulative N2O emission compared to DI1 and FWI, respectively. Area-scaled emission among the water-saving irrigation methods showed no significance. The yield-scaled emission in DI1 and DI2 and FWI were 101, 67.5 and 102%, respectively, significantly lower than CK. The adoption of FWI produced an acceptable rice yield with the lowest yield-scaled emission and highest water productivity among the irrigation practices. Our experiment demonstrates that dry direct-seeding with furrow irrigation can impact triple-wins of sustainable rice yield, high water-use efficiency and low GHG emissions in North China. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) stocks and nutrient availability are key indicators of soil quality, and both can be influenced by land‐use change. However, it is still unclear whether the impact of land‐use change on SOC and nutrient stocks differs between ecoregions. Grasslands near the northeast border of the Qinghai‐Tibetan Plateau (QTP) occur across several ecoregions that have recently been subjected to substantial land‐use change. Based on long‐term land‐use history, we conducted a field investigation comparing soil C and nutrient stocks between natural grassland (NGL) and three types of converted grassland (agricultural grassland, AGL; farmland, FL; and abandoned farmland, AFL) in three ecoregions along a climate gradient: alpine meadow, temperate steppe and temperate desert. Compared with NGL, soil C stocks in converted grasslands were 22%–30% lower in the alpine meadow, but 60–82% higher in the temperate steppe and 6%–76% higher in the temperate desert. Converted grasslands also contained higher stocks of available nitrogen and phosphorus than NGL in the temperate steppe and desert. Soils (0–40 cm) in NGL contained 14.8 ± 0.1 kg C m−2 in alpine meadow, 6.7 ± 0.6 kg C m−2 in temperate steppe and 1.7 ± 0.3 kg C m−2 in temperate desert. Together, our results indicate that the responses of soil C and nutrients to grassland conversion differed between ecoregions. Thus, to optimize soil C sequestration rates and overall soil quality, we suggest that land‐use policies in this area should take into account local environmental conditions. [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]

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]

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]