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Rafeza BEGUM Mohammad M. R. JAHANGIR Mohammad JAHIRUDDIN Mohammad Rafiqul ISLAM Shaikh M. BOKHTIAR Khandakar R. ISLAM 《土壤圈》2022,32(6):916-927
Soil total organic carbon (TOC) is a composite indicator of soil quality with implications for crop production and the regulation of soil ecosystem services. Research reports on the dynamics of TOC as a consequence of soil management practices in subtropical climatic conditions, where microbial carbon (C) loss is high, are very limited. The objective of our study was to evaluate the impact of seven years of continuous tillage and residue management on soil TOC dynamics (quantitative and qualitative) with respect to lability and stratification under an annual wheat-mung bean-rice cropping sequence. Composite soil samples were collected at 0-15 and 15-30 cm depths from a three-replicate split-plot experiment with tillage treatment as the main plots and crop residue levels as the sub-plots. The tillage treatments included conventional tillage (CT) and strip tillage (ST). Residue levels were high residue level (HR), 30% of the plant height, and low residue level (LR), 15%. In addition to TOC, soil samples were analyzed for particulate organic C (POC), permanganate oxidizable C (POXC), basal respiration (BR), specific maintenance respiration rate (qCO2), microbial biomass C (MBC), potentially mineralizable C (PMC), and TOC lability and management indices. The ST treatment significantly increased the TOC and labile C pools at both depths compared with the CT treatment, with the effect being more pronounced in the surface layer. The HR treatment increased TOC and labile C pools compared with the LR treatment. The ST + HR treatment showed significant increases in MBC, metabolic quotient (qR), C pool index (CPI), C lability index (CLI), and C management index (CMI), indicating improved and efficient soil biological activities in such systems compared with the CT treatment. Similarly, the stratification values, a measure of soil quality improvement, for POC and MBC were > 2, indicating improved soil quality in the ST + HR treatment compared with the CT treatment. The ST + HR treatment not only significantly increased the contents of TOC pools, but also their stocks. The CMI was correlated with qCO2, BR, and MBC, suggesting that these are sensitive indicators of early changes in TOC. The qCO2 was significantly higher in the CT + LR treatment and negatively correlated with MBC and CMI, indicating a biologically stressed soil condition in this treatment. Our findings highlight that medium-term reduced tillage with HR management has profound consequences on soil TOC quality and dynamics as mediated by alterations in labile C pools. 相似文献
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MAHFUZA BEGUM ABDUL S. JURAIMI RAJAN AMARTALINGAM AZMI BIN MAN SYED OMAR BIN SYED RASTANS 《Weed Biology and Management》2006,6(3):157-164
Glasshouse experiments were conducted from March to July 2003 to determine the effects of sowing depth, and the time, duration, and depth of flooding on the emergence, survival, and growth of Fimbristylis miliacea (L.) Vahl. The treatments that were evaluated in the first experiment were three seeding depths (0, 0.5, and 1.0 cm), while in the second experiment, three flooding depths (saturated soil with no standing water and soil with water depths of 5 and 10 cm) and three flooding durations (7, 14, and 21 days from sowing) were evaluated. In the third experiment, three flooding depths (saturated soil with no standing water, and soil with water depths of 5 and 10 cm) and four flooding regimes (7, 14, 21 or 28 days after sowing [DAS]) were evaluated. Surface seeding gave the highest emergence rate compared to the 0.5 cm and 1.0 cm soil depths. A significantly higher emergence rate was recorded with the saturated conditions than with the flooded conditions. A flooding duration of ≥ 14 days showed a clear trend of reduced emergence with increasing flooding depth. A significantly higher survival rate, plant height, root length, number of leaves, and dry matter were recorded at soil saturation followed by the 5 cm and 10 cm flooding depths when flooding was simulated at 7 and 14 DAS. When the flooding was delayed to 21 and 28 DAS, the 10 cm flooding depth was required to suppress this weed. The results provide sufficient evidence to confirm that from deeper seed burial (1 cm sowing depth), flooding depths of ≥ 5 cm of durations of 14 and 21 days and at the onset of flooding within 14 DAS were effective in suppressing the emergence and growth of F. miliacea . 相似文献
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镁(Ⅱ): 水溶态镁在中国粘土上的吸附及复合物形成的稳定常数 总被引：9，自引：2，他引：7
Techniques for measurement of the N status of rice can be an aid to making manaement decisions with economic and environmental implications.A field experiment was conuced to identify spectral variables most sensitive to N deficiency detection in rice canopy with the possibiliy for their use as a management tool. Spectral and agronomic measurements were collected in the evaluation experiment of N status from rice canopy under vive N treatments in a silt loam soil ,Nitroen fertilization effects were seen across the entire wavelength measured .Red refectance decreased and near infrared reflectance increased with increasing N fertilizer application.Spectral differences between treatments were seen throughout the test period.The naer infrared refectnce/red reflectance ration (RVI) differed mored between treatment than between single bands.Variations in canopy reflectances due to other environmental factors were reduced by the use of RVI.In the spectral variables examined ,the RVI separated the treatments most effectively,and three or four treatments can be separated.Differences in spetral responses betwenn the treatments were attributable to leaf area index ,leaf chlorophyll concentration and phtomass,wich all changed with N fertilization. 相似文献
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