Seasonal changes in the abundance and activity of bacterial and fungal denitrifying communities associated with different compost amendments

Composts can be efficient organic amendments in potato culture as they can supply carbon and nutrients to the soil. However, more information is required to the effects of composts on denitrification and nitrous oxide emissions (N2O) and the emission-producing denitrifying communities. The effect of three compost amendments (municipal source separated organic waste compost (SSOC), forestry waste mixed with poultry manure compost (FPMC), and forestry residues compost (FRC)) on fungal and bacterial denitrifying communities and activity was examined in an agricultural field cropped to potatoes in during the fall, spring and summer seasons. The denitrification enzyme activity (DEA), N2O emissions and respiration were measured in parallel. N2O emission rates were greater in FRC-amended soils in the fall and summer, while soil respiration was highest in SSOC-amended soil in the fall. A large number of <i>nirK</i> denitrifying fungal transcripts was detected in the fall, coinciding with compost application while the greatest <i>nirK</i> bacterial transcripts were measured in the summer when plants were actively growing. Denitrifying community and transcript levels were poor predictors of DEA, N2O emissions or respiration rates in compost-amended soil. Overall, the sampling date was driving the population and activity levels of the three denitrifying communities under study.

Alleviation of Chlorpyrifos Toxicity in Maize (Zea mays L.) by Reducing Its Uptake and Oxidative Stress in Response to Soil-Applied Compost and Biochar Amendments

Chlorpyrifos (CP) is a pesticide used extensively in agricultural crops. Residual CP has been found in a variety of soils, vegetables and fruits indicating a serious danger to humans. Therefore, it is necessary to restrict its entry into agricultural products for food safety. A wire-house pot experiment was conducted with maize plants in biochar- and compost-amended soil (at 0.25% and 0.50%, respectively, in weight-by-weight composition) contaminated with 100 and 200 mg kg−1 of CP, respectively. Results indicated toxicity at both CP levels (with 84% growth reduction) at CP 200 mg kg−1. However, application of compost and biochar at the 0.50% level improved the fresh weight (2.8- and 4-fold, respectively). Stimulated superoxide dismutase (SOD) and peroxidase (POX) activities and depressed catalase (CAT) activity were recorded in response to CP contamination and were significantly recovered by the amendments. Both amendments significantly decreased the CP phytoavailability. With biochar, 91% and 76% reduction in the CP concentration in maize shoots and with compost 72% and 68% reduction was recorded, at a 0.50% level in 100 and 200 mg kg−1 contaminated treatments respectively. Compost accelerated the CP degradation in postharvest soil. Therefore, biochar and compost amendments can effectively be used to decrease CP entry in agricultural produce by reducing its phytoavailability.

Amelioration of Adverse Effect of Drought on Rice (Oryza sativa L.) Variety BRRI Dhan28 through Application of Poultry Litter Based Compost

An experiment was carried out at the research field of Crop Physiology and Ecology Department, Hajee Mohammad Danesh Science and Technology University, Dinajpur during January 2017 to May 2017 to evaluate the effects of poultry litter based composts on morpho-physiological, yield and yield contributing characters of BRRI dhan28, a mega rice variety of Boro season in Bangladesh, under different water stress conditions. The plants were grown in pots, and the experiment was laid out in a factorial complete randomized design (CRD) with three replications. Factor A included three levels of fertilizer and compost amendments i.e. control (recommended inorganic fertilizer), compost (10 t ha-1) + inorganic fertilizer, compost (20 t ha-1) + without inorganic fertilizers, and factor B comprised of three water levels (continuous flooding, 100% field capacity and 75% field capacity). Different parameters such as plant height, tiller number, leaf number, leaf area, chlorophyll content, proline content and yield contributing characters were measured during the experiment. Most of the measured parameters were significantly influenced by irrigation levels with different fertilizer and compost amendments. The highest plant height and leaf number per hill were found in the treatment of compost (10 t ha-1) + inorganic fertilizer with 100% field capacity, though the maximum tiller number were produced by the interaction of control with flooding irrigation. The total chlorophyll was observed more in flag leaf by the interaction of control with 100% field capacity. The Proline content was observed more in flag leaf by the interaction of control with 75% field capacity. Relative water content was found more with the interaction of compost (10 t ha-1) + inorganic fertilizer with 75% field capacity. The highest effective tiller number hill-1 was found from control (19.33) at harvest. It was also observed that irrigation with 75% field capacity produced the lowest effective tiller (15.89) hill-1 at harvest. The longest panicle length (23.12 cm) was observed with the combined effect of compost (10 t ha-1) +inorganic with 75% field capacity. Thousand grain weight was found highest (18.83 g) in the interaction of compost (20 t ha-1 + without inorganic) with 75% field capacity. The interaction of compost (20 t ha-1 + without inorganic) and flooding irrigation gave the highest grain yield (33.17 g pot-1), which was statistically similar to the treatment of compost (10 t ha-1 + inorganic) with flooding irrigation. The highest harvest index was found from compost (20 t ha-1 + without inorganic) with flooding irrigation. The Agriculturists 2020; 18(1) 42-55