ABSTRACTDamage to soil structures and depletions of soil carbon under paddy cultivation are concerns for the sustenance of food security in Bangladesh. Long-term organic amendment in paddy field plays an important role in improving soil properties and crop productivity, but no such study has yet been conducted under rice-fallow-rice. A field experiment was carried out with or without the addition of cow dung (CD) and poultry manure (PM) as integrated plant nutrient systems (IPNS) to evaluate soil organic carbon (SOC) budget, net ecosystem carbon stock, and aggregate stability. The experiment was established in 2009 and continued until 2016 under the rice-fallow-rice system. Soil bulk density reduced from 1.39 to 1.37 g cm?3 and soil aggregate size increased from 6.78 to 7.05 mm with organic amendments. Both carbon (C) and nitrogen (N) contents increased with the addition of CD and PM, which varied with aggregate size. The highest C (1.6–2.15%) and N (0.11–0.24%) contents were observed in 0.30 mm aggregate than other fractions. Soil organic C contents showed polynomial relationships with aggregate size and organic amendment. The SOC sequestration ranged from 94 to 168 kg ha?1 depending on organic materials used. The C balances were negative for control (?99 to ?201 kg ha?1) and chemical fertilizers alone (?58 to ?91 kg ha?1). In comparison to control treatment, grain yield of rice increased significantly with the addition of organic substances. Balanced application of CD and PM with IPNS-based inorganic fertilizers was the best management option for yield and sustainable soil health. 相似文献
In the Sahel region of West Africa, the traditional organization of the population and the grazing land avoided overexploitation of pastures. Since independence in the 1960s, grazing lands have been opened to all without specific guidance, and the vulnerability of the pastures to degradation has increased. Rotational grazing is postulated as a possible solution to provide higher pasture productivity, higher animal loads per unit land, and perhaps improved soil carbon storage. The objective of this study was to conduct a simulation-based assessment of the impact of rotational grazing management on pasture biomass production, grazing efficiency, animal grazing requirement satisfaction, and soil carbon storage in the Madiama Commune, Mali. The results showed that grazing intensity is the primary factor influencing the productivity of annual pastures and their capacity to provide for animal grazing requirements. Rotating the animals in paddocks is a positive practice for pasture protection that showed advantage as the grazing pressure increased. Increasing the size of the reserve biomass not available for grazing, which triggers the decision of taking the animals off the field, provided better pasture protection but reduced animal grazing requirements satisfaction. In terms of soil carbon storage, all management scenarios led to reduction of soil carbon at the end of the 50-year simulation periods, ranging between 4% and 5% of the initial storage. The differences in reduction as a function of grazing intensity were of no practical significance in these soils with very low organic matter content, mostly resistant to decomposition. 相似文献
The effects of three cotton-based cropping systems on soil properties, black root rot severity, and growth of cotton in a Vertisol were evaluated after a series of floods in eastern Australia. The experimental treatments, which had been imposed since 1985, were conventionally and minimum-tilled continuous cotton, and minimum-tilled cotton–wheat rotation. Frequent rainfall and flooding during the winter of 1998 resulted in near saturated soil at spring sowing in October. Although conventional tillage operations were completed before flooding, minimum tillage operations were not possible due to excessive moisture and cotton was sown onto the old beds with no-tillage. Soil specific volume (electrical conductivity of a 1:5 soil:water suspension) EC1:5, exchangeable Na content, pH and organic C were determined for the top 0.6 m of the profile in summer 1998 and again in 1999. Organic C in the surface 0.10 m was also evaluated during 1998–2000. Black root rot severity and mycorrhizal fungal colonisation were evaluated at 6 weeks after sowing. Tissue nutrient concentrations were measured in mature cotton plants. Cotton lint yield and fibre quality were evaluated after picking and ginning.
In comparison with either minimum- or conventionally tilled continuous cotton, minimum-tilled cotton–wheat rotation had the lowest exchangeable Na content and severity of bacterial black root rot, best surface structure and the highest crop growth, nutrient uptake and lint yields. Subsoil structure was the best with conventionally tilled continuous cotton. The 1998 floods appear to have decreased exchangeable Na and increased soil pH in all treatments. Surface organic C also decreased between 1998 and 2000. Soil structural damage was minimised by avoiding tillage and trafficking in wet conditions. Compared with 1998, average yield decreases in 1999 were of the order of 43%. Cotton lint fibre quality was also poorer in 1999. 相似文献
AIM: To study the subtype of metabotropic glutamate receptors (mGluRs) which induce contralateral rotations of rats after mGluRs activation.METHODS:Turning movement was measured at 6 h after agonist or antagonist of mGluRs was microinjected into rat striatum. RESULTS: tACPD, an agonist of mGluRs, at 500 nmol and 1 000 nmol induced contralateral rotations of rats. L-AP3, MCPG and dantrolene attenuated the turning effect of tACPD. DHPG, a selective agonist of group I mGluRs, mimicked the effect of tACPD. The effect of DHPG was blocked by MCPG, LY367385 (antagonist of mGluR1) and MPEP (antagonist of mGluR5), and abolished by pretreatment with reserpine (5mg/kg). CONCLUSION:These results indicated the activation of group I mGluRs in rat striatum induced turning effect, which may be associated with the mobilization of intracellular Ca2+ stores and dependant on the existence of dopamine. 相似文献