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Dry direct-seeded rice is an alternative cropping technique that should require less water and labor than classical transplanted-flooded rice. Here, we studied growth, yield and resource use efficiency of rice cultivation in Central China, in 2012 and 2013. We compared dry direct-seeded rice and transplanted-flooded rice. For dry direct-seeded rice, we maintained aerobic conditions up to five-leaf stage followed by anaerobic conditions until maturity. We grew three rice cultivars: Lvhan1, Huanghuazhan, and Yangliangyou6. We measured grain yield, yield components, water consumed, water productivity and nitrogen use efficiency for grain production (NUEg). Our results show that grain yield of dry direct-seeded rice, of 9.01 Mg/ha, is identical to grain yield of transplanted-flooded rice, across cultivars and for both years. The grain yield of dry direct-seeded rice is mainly controlled by the panicle number. Moreover, dry direct-seeded rice uses 15.3 % less water than transplanted-flooded rice. Dry direct-seeded rice increased the grain nitrogen use efficiency by 20.3 % in 2012 and 11.2 % in 2013. [ABSTRACT FROM AUTHOR]

Although diazotrophs are important in the nitrogen (N)-cycle and contribute to the pool of plant available N, the population response to long-term inorganic fertilization is largely unknown. Here, we investigated the diazotrophic populations in both the bulk and rhizosphere soils of maize grown in an acidic farmland soil that experienced 25 years of inorganic fertilization. The fertilization regimes included unfertilized control, N fertilizer alone, N fertilizer with quicklime, phosphorus (P) and potassium (K) fertilizers, N + P + K fertilizers, and N + P + K fertilizers with quicklime. Quantitative PCR and high-throughput pyrosequencing of the nifH gene were used to analyze diazotrophic abundance and community composition. All of the fertilizer treatments improved soil nutrient availability, but those without quicklime caused soil acidification. Maize biomasses and nifH copy numbers were significantly lower under N and N + P + K treatments but increased under P + K fertilization. Quicklime applications effectively alleviated the inhibitory effect of N input. Fertilization led to decreases in operational taxonomic unit richness and shifts in diazotrophic community composition. Soil pH and nutrient availability had a cooperative effect on diazotrophic abundance, while soil nutrient availability appeared to be the main factor shaping diazotrophic community structure. Rhizosphere effects increased the nifH gene copy number but did not obviously change the diazotrophic community composition on the current research scale. Overall, the long-term inorganic fertilization affected both diazotrophic abundance and community composition, and the fertilizer treatment had a greater influence than quicklime remediation or crop cultivation on community composition. [ABSTRACT FROM AUTHOR]