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Aims and background: Soil fertility quality index is a useful indicator that helps to improve sustainable land use management and achieve economical yield in agriculture production. The objectives of this study were to evaluate the changes of soil fertility quality between the 1980s and 2000s in different cropping systems and its significance to crop productivity and sustainability. Methods: We collected all published data on crop yields and soil parameters from 58 long-term experiments in three typical double-cropping systems in China, including maize-wheat (M-W), rice-rice (R-R) and rice-wheat (R-W) cropping systems, and selected seven fertilizer treatments in each experiment, including inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), phosphorus and potassium fertilizer (PK) and balanced mineral fertilizer (NPK)], combined NPK with farmyard manure (NPKM) or crop straw (NPKS), and no fertilizer application (served as control). For comparison, an integrated fertility quality index (IFQI) was used to estimate the variations in soil fertility in different cropping systems. Moreover, the mean production variability index (PVI, %) in each cropping system was calculated to evaluate the stability of crop production. Results: Over cropping systems, the averaged relative yields of PK, NK and NP ranged from 38.0 to 97.4 %, while the mean yields can be increased by 2.4-5.1 % in NPKM, compared to NPK. The mean yields were similar between NPK and NPKS for maize and wheat crops, but the yield was increased by 4.3-10.0 % in NPKS. Among the different treatments, the highest variability of cereal productivity was obtained in NK, PK or Control, while the lowest value was mostly recorded in NPKM or NPKS in these three cropping systems. Relative to the control, the IFQIs in fertilization treatments were increased by 9.4-150.0 %, 6.2-41.5 % and 1.3-17.5 % in M-W, R-W and R-R systems, respectively (except for PK treatment in R-R system). However, changes of IFQI in topsoil differed among fertilizer treatments, and greater increases existed in the treatments receiving organic residues (NPKM and NPKS). Conclusions: The increase in crop yield is exponentially correlated with the increased IFQI over treatments in three cropping systems. Over the treatments and systems, production variability among years is shown to be negatively, linearly related to IFQI ( P < 0.001). Therefore, the high grain yield and low production variability can be simultaneously achieved by increasing soil fertility in all three cropping systems. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer-induced direct nitrous oxide (N2O) emissions depend on water regimes in paddy fields, such as seasonal continuous flooding (F), flooding–midseason drainage–reflooding (F-D-F), and flooding–midseason drainage–reflooding–moist intermittent irrigation but without water logging (F-D-F-M). In order to estimate the changes in direct N2O emission from paddy fields during the rice-growing season in Mainland of China between the 1950s and the 1990s, the country-specific emission factors of N2O-N under different water regimes combined with rice production data were adopted in the present study. Census statistics on rice production showed that water management and nitrogen input regimes have changed in rice paddies since the 1950s. During the 1950s–1970s, about 20–25% of the rice paddy was continuously waterlogged, and 75–80% under the water regime of F-D-F. Since the 1980s, about 12–16%, 77%, and 7–12% of paddy fields were under the water regimes of F, F-D-F, and F-D-F-M, respectively. Total nitrogen input during the rice-growing season has increased from 87.5 kg N ha−1 in the 1950s to 224.6 kg N ha−1 in the 1990s. The emission factors of N2O-N were estimated to be 0.02%, 0.42%, and 0.73% for rice paddies under the F, F-D-F, and F-D-F-M water regimes, respectively. Seasonal N2O emissions have increased from 9.6 Gg N2O-N each year in the 1950s to 32.3 Gg N2O-N in the 1990s, which is accompanied by the increase in rice yield over the period 1950s–1990s. The uncertainties in N2O estimate were estimated to be 59.8% in the 1950s and 37.5% in the 1990s. In the 1990s, N2O emissions during the rice-growing season accounted for 8–11% of the reported annual total of N2O emissions from croplands in China, suggesting that paddy rice development could have contributed to mitigating agricultural N2O emissions in the past decades. However, seasonal N2O emissions would be increased, given that saving-water irrigation and nitrogen inputs are increasingly adopted in rice paddies in China. [ABSTRACT FROM AUTHOR]

Closing yield (YG) and nitrogen use efficiency (NUE) gaps amongst smallholder farmers are critical to ensuring food security and environmental sustainability. Here we report a comprehensive analysis of a data set derived from farm-surveys and previously published studies in a typical high N input area of China. Using scenario analysis, farmers from both sources were divided into four rice production levels to assess the YG and NUE of smallholder farmers. Farm surveys showed that rice yield and partial factor productivity of applied N (PFPN) averaged 8273 kg ha−1 and 23.1 kg kg−1 at regional-scale, with a potential increase of 21–43% and 33–52%, respectively. A wide variation in yield and PFPN across different types of farmer was observed. Optimized N management significantly narrowed YGs by 3.7% and PFPN gap by 63.5% on average based on the published literature. Multiple factors, including excessive N rates, small rice planting area (0.33 ha), the aging (51 years old) and low education level (6 years of education) of the major labor force, can partly explain causes of yield and NUE gaps. These findings provide farm-based evidence that centralized management, good agronomy plus advances in knowledge and technologies are essential for future agricultural development. [ABSTRACT FROM AUTHOR]

A 3-year field experiment was conducted to investigate the effects of different organic fertilization strategies for rice–wheat annual rotation systems on net global warming potential (net GWP) and greenhouse gas intensity (GHGI) by incorporating methane, nitrous oxide emissions, the changes in soil organic carbon (SOC) derived from the net ecosystem carbon budget (NECB), and the CO 2 equivalent emissions from manure and chemical nitrogen (N) fertilizer manufacturing. Six fertilization strategies were studied, including control (CK), N fertilizer (CF), pig manure compost + N fertilizer (MC), straw + N fertilizer (SC), straw + pig manure compost + N fertilizer (SM), and straw + straw-decomposing inoculant + N fertilizer (SI). The results indicated that the application of organic amendments did not change the seasonal pattern of GHG emissions but significantly affected their seasonal quantities. Averaged over the 3 cycles, the annual SOC sequestration rates contributed significantly to the net GWPs and were estimated to be 1.01 t C ha −1  yr −1 for the control and 1.13–1.27 t C ha −1  yr −1 for the fertilized plots. Compared to CF, the MC strategy significantly increased SOC while had similar size of net GWP and GHGI, thus deserving recommendation regarding sustainable soil productivity and GHGs mitigations. However, the other proposed organic strategies of SC, SM, and SI significantly increased net GWP and GHGI as well as SOC thus requiring further researches for GHGs mitigations. Therefore, we recommend that the application of manure substituting half chemical fertilizer be an effective strategy while straw returning in any currently studied strategies should be re-examined in the rice–wheat annual rotation system. [ABSTRACT FROM AUTHOR]