Arsenic stress on photosynthesis and growth in Ipomoea aquatica

An experiment was conducted to understand the effect of arsenic (As) on photosynthetic pigments in Ipomoea aquatica leaves, its growth performance and As uptake in edible plant parts. The experiment was designed with three levels of As treatments, viz. 10, 20, and 40 mg As kg-1 soil along with control, and three biological replications. I. aquatica was grown for six weeks after seed germination. Chlorophyll-a, chlorophyll-b, carotenoid, plant height and weight increased at lower rate of As application (10 mg kg-1) in soil. Higher As (20 and 40 mg As kg-1 soil) in soil significantly decreased all the parameters except carotenoid. Both plant height and weight were significantly reduced at 20 mg As kg-1 in soil. Chlorophyll-a and chlorophyll-b content were significantly reduced at 40 mg As kg-1 in soil. Arsenic concentration in plant parts increased significantly at higher As concentration and exceeded the maximum limit of As (0.5 mg kg-1) for vegetables at 20 mg As kg-1 soil and above. Arsenic uptake (µg plant-1) also increased significantly with elevated levels of soil As (40 mg kg-1). Considering the growth performance, I. aquatica should not be recommended to grow where the soil As concentration is 20 mg kg-1 and above

Effects of straw incorporation and straw-burning on aggregate stability and soil organic carbon in a clay soil of Bangladesh

The clay soil of Bangladesh is typically low in soil organic carbon (SOC) and generally has poor soil aggregate stability (measured as mean weight diameter, MWD). The addition of organic amendments in the field has the potential to increase soil organic matter (SOM) and MWD. However, the influence of organic amendments on aggregation in the clay soils of Bangladesh is largely unknown. A short-term (105 days) field study has been conducted to evaluate the effects of straw incorporation and straw-burning treatments on MWD and SOC in clay soil under eggplant (Solanum melongena L.). This study consisted of three treatments: (i) control (no amendments), (ii) rice straw (straw applied at 21 t ha−1), (iii) rice straw-burning (ash retained after burning at 7.4 t ha−1). Soil samples were collected after plant harvest, and then MWD, SOC, glomalin-related soil protein (GRSP), microbial biomass carbon (MBC), Fe-oxides, and available soil nutrients (e.g., N, P, K, S, Na, Ca, and Mg) were determined. Our results showed that MWD in straw addition treatment was on average 2 times higher, whereas SOC was 1.3 times higher compared to the control and straw-burning treatments, respectively (P  0.05). Our study demonstrates that the incorporation of rice straw has the potential to increase soil aggregation and SOC stock, at least for the short term in the clay soils of Bangladesh