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Accurate modelling of agricultural management impacts on greenhouse gas emissions and the cycling of carbon and nitrogen is complicated due to interactions between various processes and the disturbance caused by field management. In this study, a process-based model, the Soil-Plant-Atmosphere Continuum System (SPACSYS), was used to simulate the effects of different fertilisation regimes on crop yields, the dynamics of soil organic carbon (SOC) and total nitrogen (SN) stocks from 1990 to 2010, and soil CO 2 (2007–2010) and N 2 O (2007–2008) emissions based on a long-term fertilisation experiment with a winter-wheat ( Triticum Aestivum L.) and summer-maize ( Zea mays L.) intercropping system in Eutric Cambisol (FAO) soil in southern China. Three fertilisation treatments were 1) unfertilised (Control), 2) chemical nitrogen, phosphorus and potassium (NPK), and 3) NPK plus pig manure (NPKM). Statistical analyses indicated that the SPACSYS model can reasonably simulate the yields of wheat and maize, the evolution of SOC and SN stocks and soil CO 2 and N 2 O emissions. The simulations showed that the NPKM treatment had the highest values of crop yields, SOC and SN stocks, and soil CO 2 and N 2 O emissions were the lowest from the Control treatment. Furthermore, the simulated results showed that manure amendment along with chemical fertiliser applications led to both C (1017 ± 470 kg C ha −1 yr −1 ) and N gains (91.7 ± 15.1 kg N ha −1 yr −1 ) in the plant-soil system, while the Control treatment caused a slight loss in C and N. In conclusion, the SPACSYS model can accurately simulate the processes of C and N as affected by various fertilisation treatments in the red soil. Furthermore, application of chemical fertilisers plus manure could be a suitable management for ensuring crop yield and sustaining soil fertility in the red soil region, but the ratio of chemical fertilisers to manure should be optimized to reduce C and N losses to the environment. [ABSTRACT FROM AUTHOR]

Soil chloropicrin (CP) fumigation helps to increase crop yields by eliminating soil-borne diseases which inhibit plant growth. However, little is known about the effect of the CP fumigation combined with fungicide application on plant growth and nutrient uptake. In this study, we conducted a mesocosm experiment with six treatments: CK (untreated soil), AZO1 (a single application of azoxystrobin (AZO)), AZO2 (double applications of AZO), CP (CP fumigation with no AZO), CP+AZO1 (CP combined with AZO1) and CP+AZO2 (CP combined with AZO2) to investigate the effects of CP fumigation and AZO application on ginger growth and phosphorus (P) uptake. Results showed that a single application of AZO had no significant effect on ginger height, biomass and P uptake whether treated with or without CP fumigation, whereas double applications of AZO combined with CP fumigation significantly improved ginger height and the total amount of P in root (P < 0.05). Meanwhile, AZO residues were similar in all treatments with the same number of applications, with less than 50% remaining in the soil after 7 days applied, indicating that CP fumigation treatment did not influence AZO degradation in ginger cultivation. In addition, although the differences in P use efficiency observed across the different treatments were not significant, they nevertheless suggest that the P budget and soil microbial activity may contribute to those differences. Therefore, further studies should be done to link P cycling with microbial communities, and how these related to fumigation and fungicide application. [Display omitted] • We studied effects of chloropicrin and azoxystrobin on ginger growth and P uptake. • The half-life of AZO in soil was 7 days, which was not influenced by CP fumigation. • The ginger plants in CP-treated soil were 18.9–32.8 cm higher than that in CK. • Ginger biomass was not affected by CP and AZO applied alone or in combination. • CP combined with double applications of AZO promoted the ginger rhizome P amount. [ABSTRACT FROM AUTHOR]

A pot trial was conducted to assess the efficiency of P-induced metal immobilization in soils. Natural hydroxyapatite (HA), phosphate rock (PR), triple-superphosphate (TSP), and diammonium phosphate (DAP) were evaluated for their ability to reduce cadmium (Cd), lead (Pb), and zinc (Zn) bioavailability in an artificially metal-contaminated soil with three addition levels: T0 (without metals added), T1 (Cd/Pb/Zn:0.6/100/66mgkg−1), and T2 (Cd/Pb/Zn: 1.5/300/200mgkg−1). Phosphate compounds were applied at 2500mg P2O5 kg−1 soil for each metal level with five treatments: CK (control), TSP, DAP, PR, and HA, respectively. The immobilization and bioavailability of Cd, Pb, and Zn were determined by plant (Brassica campestris L.) uptake, scanning electron microscope (SEM), and sequential extraction. The results showed that HA was superior to all other materials for reducing Pb, Zn, and Cd uptake in shoot with reductions of 34.6–53.3% for Pb, 31.2–47.3% for Zn, and 39.1–42.4% for Cd, respectively, as compared with the control treatment. The mechanisms of Pb immobilization in the soil and the decreased Pb translocation from the plant root to shoot induced by added phosphate were identified with scanning electron microscope (SEM) equipped with energy dispersive X-ray elemental spectrometry (EDS). Sequential extraction results indicated that the phosphate amendments converted significant amounts of the soil Pb, Zn, and Cd from exchangeable (EX), organic bound (OC), carbonate bound (CB), amorphous Fe and Al oxides-bound (OX) (non-residual (RES) fractions) to RES fraction. In general, the effect of different phosphates on plant uptake of Pb, Zn, and Cd followed the order: HA>PR>DAP>TSP. The results suggested that HA and PR amendments could significantly reduce the bioavailability and increase the geochemical stability of soil Pb, Zn, and Cd in contaminated soils. [Copyright &y& Elsevier]

Mineral-associated organic carbon (MOC), that is stabilized by fine soil particles (i.e., silt plus clay, <53 μm), is important for soil organic carbon (SOC) persistence and sequestration, due to its large contribution to total SOC (TSOC) and long turnover time. Our objectives were to investigate how climate, soil type, soil texture, and agricultural managements affect MOC contributions to TSOC in China. We created a dataset from 103 published papers, including 1106 data points pairing MOC and TSOC across three major land use types: cropland, grassland, and forest. Overall, the MOC/TSOC ratio ranged from 0.27 to 0.80 and varied significantly among soil groups in cropland, grassland, and forest. Croplands and forest exhibited significantly higher median MOC/TSOC ratios than in grassland. Moreover, forest and grassland soils in temperate regions had higher MOC/TSOC ratios than in subtropical regions. Furthermore, the MOC/TSOC ratio was much higher in ultisol, compared with the other soil types. Both the MOC content and MOC/TSOC ratio were positively correlated with the amount of fine fraction (silt plus clay) in soil, highlighting the importance of soil texture in stabilizing organic carbon across various climate zones. In cropland, different fertilization practices and land uses (e.g., upland, paddy, and upland-paddy rotation) significantly altered MOC/TSOC ratios, but not in cropping systems (e.g., mono- and double-cropping) characterized by climatic differences. This study demonstrates that the MOC/TSOC ratio is mainly driven by soil texture, soil types, and related climate and land uses, and thus the variations in MOC/TSOC ratios should be taken into account when quantitatively estimating soil C sequestration potential of silt plus clay particles on a large scale. [ABSTRACT FROM AUTHOR]