Effects of Cropping Pattern on Carbon Sequestration And Aggregate Stability of Soil in Long Term Agricultural Fields in Khulna, Bangladesh

Effects of cropping pattern on soil carbon sequestration and their aggregate stability in long term agricultural fields was investigated in 2018. Four cropping patterns were selected that have been cultivated for last ten years. Results showed that Soil organic carbon (SOC) value was improved for vegetable field from 4.06 to 9.11 g/kg and carbon stock (20.14 Mg C ha/yr) as well as soil carbon sequestration rate was the highest in vegetable field (1.12 Mg C ha/yr). The logarithmic relationship between the C input and C sequestration rate showed the strong correlation (r = 0.72, p < 0.05). In terms of aggregate stability, vegetable field put the best result (0.41 mm) (p > 0.05). The straight-line relation between aggregate stability and Cstock established that they are strongly correlated (r = 0.81, p < 0.05). Finally, results indicated that Vegetable-Vegetable-Vegetable cropping pattern was the best soil carbon sequester along with the best aggregate stability. Bangladesh J. Bot. 50(4): 1029-1034, 2021 (December)

Ecological and Health Risk Assessment of Trace Metal Pollution in Vegetable Field Soils from the Eastern Nile Delta, Egypt

The accumulation of trace metals in vegetable field soils is of expanding worry because of the potential health hazards and its detrimental effects on soil ecosystems. To investigate the state of trace metal pollution in vegetable field soils, 60 surface soil samples were collected from vegetable fields across the Eastern Nile Delta region, Egypt. The results explained that the concentrations of Cu, Mn and Ni were lesser than their corresponding background values, while the concentrations of Cd, Co, Pb and Zn were exceed their background values. The pollution indices showed that the study soil experienced low to moderate contamination, and the Cd and Cr contamination was serious. The hazard index values of nine trace metals signified that there no adverse non-carcinogenic risk for adults and children. The carcinogenic risk of Cd, Co, Ni and Pb for both age groups was within the acceptable limits, while Cr had critical carcinogenic hazard to children. Overall, the quality of studied soils is relative safety, although some samples impose serious pollution problems by Cd and Cr. Thus, properly monitor trace metals and soil management action should be applied to reduce further soil pollution in vegetable fields in the Eastern Nile Delta.

Increases of Temperature Response for CO2 Emission in a Biochar-Amended Vegetable Field Soil

To explore the effects of biochar application on CO2 and CH4 emission as well as the temperature response of CO2 emission, an one-year experiment was conducted with three treatments (Control; CF, chemical fertilizer only; BCF, biochar combined with chemical fertilizer) in a vegetable field. Results shown that (1) compared with CF, short-term application of biochar significantly enhancing the cumulative CO2 emission by 27.5% from soil-plant system, via increasing the soil microbial biomass (e.g., MBC) and C substrates (e.g., SOC). (2) A lowest emission of CH4 was observed in BCF treatment, and an increase CH4 consumption and reduce competition with NH4+ may be responsible for the significant reduction in CH4 source strength in biochar amended soil. (3) Activation energy (Ea) was identified as an important factor influencing the temperature sensitivity (Q10) of CO2 emission. Fertilization (CF and BCF) reduced the average Q10 and Ea values of CO2 emission by 9.0-26.7% and 23.5-10.1%, relative to the control, respectively. Besides, the average of Ea value in BCF treatment (51.9 KJ mol-1) was significantly higher than those in control and CF treatment. The increase in Q10 and Ea values following biochar application possibly contributed to the supplement of limit labile C and nutrient but highly resistant C following biochar application. Soil pH and crop cultivation may play key roles in influencing the change of Ea. Our study concludes that biochar amendment increased CO2 emission and temperature response of CO2 emission from soil-plant system, while reduced CH4 emission.

Effects of long-term integrated agri-aquaculture on the soil fungal community structure and function in vegetable fields

The diversity and community structure of soil fungi play an important role in crop production and ecosystem balance, especially in paddy-upland vegetable field systems. High-throughput sequencing was used to study changes in the soil fungal community structure and function in paddy-upland vegetable field systems. The results showed that compared with traditional planting, the diversity and community structure of soil fungi were changed by the combination of flooding and drought, the Shannon index increased by 11.07%, and the proportion of the dominant species, Mortierella, decreased by 22.74%. Soil available nitrogen, total phosphorus, available phosphorus, total nitrogen and organic matter played a leading role in the initial stage of the experiment, while the dominant factor changed to total potassium 3 years later and then to soil pH and water content 6 years later. FUNGuild analysis showed that the proportion of three independent trophic modes of soil fungi were increased by the combined flooded-drought model, and there were multiple interaction factors, For example, nutrient supply, pH and planting pattern. This study showed that soil fertility, crop yield and economic benefits were better than the traditional model after three years of planting and breeding. The longer the time, the better the effect.