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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]

Background and aims: The rice production is experiencing a shift from conventionally seedling-transplanted (TPR) to direct-seeded (DSR) cropping systems in Southeast Asia. Besides the difference in rice crop establishment, water regime is typically characterized as water-saving moist irrigation for DSR and flooding-midseason drainage-reflooding and moist irrigation for TPR fields, respectively. A field experiment was conducted to quantify methane (CH) and nitrous oxide (NO) emissions from the DSR and TPR rice paddies in southeast China. Methods: Seasonal measurements of CH and NO fluxes from the DSR and TPR plots were simultaneously taken by static chamber-GC technique. Results: Seasonal fluxes of CH averaged 1.58 mg m h and 1.02 mg m h across treatments in TPR and DSR rice paddies, respectively. Compared with TPR cropping systems, seasonal NO emissions from DSR cropping systems were increased by 49 % and 46 % for the plots with or without N application, respectively. The emission factors of NO were estimated to be 0.45 % and 0.69 % of N application, with a background emission of 0.65 and 0.95 kg NO-N ha under the TPR and DSR cropping regimes, respectively. Rice biomass and grain yield were significantly greater in the DSR than in the TPR cropping systems. The net global warming potential (GWP) of CH and NO emissions were comparable between the two cropping systems, while the greenhouse gas intensity (GHGI) was significantly lower in the DSR than in the TPR cropping systems. Conclusions: Higher grain yield, comparable GWP, and lower GHGI suggest that the DSR instead of conventional TPR rice cropping regime would weaken the radiative forcing of rice production in terms of per unit of rice grain yield in China, and DSR rice cropping regime could be a promising rice development alternative in mainland China. [ABSTRACT FROM AUTHOR]

Aims: A field experiment was conducted to quantify annual nitrous oxide (NO) fluxes from control and fertilized plots under open-air and greenhouse vegetable cropping systems in southeast China. We compiled the reported global field annual NO flux measurements to estimate the emission factor of N fertilizer for NO and its background emissions from vegetable fields. Methods: Fluxes of NO were measured using static chamber-GC techniques over the 2010-2011 annual cycle with multiple cropping seasons. Results: The mean annual NO fluxes from the controls were 46.1 ± 2.3 μg NO-N m hr and 68.3 ± 4.1 μg NO-N m hr in the open-air and greenhouse vegetable systems, respectively. For the plots receiving 900 kg N ha, annual NO emissions averaged 90.6 ± 8.9 μg NO-N m hr and 106.4 ± 6.6 μg NO-N m hr in the open-air and greenhouse vegetable systems, respectively. By pooling published field NO flux measurements taken over or close to a full year, the NO emission factor for N fertilizer averaged 0.63 ± 0.09 %, with a background emission of 2.67 ± 0.80 kg NO-N ha in Chinese vegetable fields. Annual NO emissions from Chinese vegetable systems were estimated to be 84.7 Gg NO-N yr, consisting of 72.5 Gg NO-N yr and 12.2 Gg NO-N yr in the open-air and greenhouse vegetable systems, respectively. Conclusions: While NO emissions from the greenhouse vegetable cropping system tended to be slightly higher compared to the open-air system in our experiment, the synthesis of literature data suggests that NO emissions would be greater at low N-rates but smaller at high N-rates in greenhouse systems than in open-air vegetable cropping systems. The estimates of this study suggest that vegetable cropping systems covering 11.4 % in national total cropping area, contributed 21-25 % to the total NO emission from Chinese croplands. [ABSTRACT FROM AUTHOR]