RESUMEN
Biochar is an effective soil amendment with capabilities of boosting carbon sequestration and enhancing soil fertility, thus enhancing plant growth and productivity. While numerous studies have documented the positive effects of biochar on improving soil properties, a number of studies have reported conflicting results. Therefore, the current study was conducted to evaluate the impact of Prosopis juliflora biochar (0, 2.5, 5.0, and 7.5 t ha-1) on soil biochemical properties in Coastal Kenya to ascertain biochar's potential for soil fertility improvement. A randomized complete block design was used for setting up the experiment with three replicates, while Casuarina equisetifolia L. was planted as the test crop. Soil sampling for nutrient analysis was conducted quarterly for 12 months to assess nutrient dynamics under different biochar rates in the current study. Compared to soil untreated with Prosopis juliflora biochar, the results showed that there was a significant increase in soil pH by 21% following biochar utilization at the rate of 7.5 t ha-1. Total nitrogen was increased by 32% after the biochar application, whereas the total organic carbon was increased by four folds in comparison to biochar-untreated soil. Available phosphorus was increased by 264% following biochar application in comparison to the control treatment. In addition, the application of biochar resulted in an increment in the soil exchangeable cations (Ca2+, K+, Mg2+) across the assessment periods. Soil cation exchange capacity (CEC), bacteria and fungi were enhanced by 95, 33 and 48%, respectively, following biochar application at 7.5 t ha-1 in comparison to untreated soil. In conclusion, these results strongly suggest improvement of soil biochemical properties following Prosopis juliflora biochar application, thus providing potential for soil fertility improvement in regions such as the one in the study.
RESUMEN
The concentration of greenhouse gases (GHGs) in the atmosphere has been increasing since the beginning of the industrial revolution. Nitrous oxide (N2O) is one of the mightiest GHGs, and agriculture is one of the main sources of N2O emissions. In this paper, we reviewed the mechanisms triggering N2O emissions and the role of agricultural practices in their mitigation. The amount of N2O produced from the soil through the combined processes of nitrification and denitrification is profoundly influenced by temperature, moisture, carbon, nitrogen and oxygen contents. These factors can be manipulated to a significant extent through field management practices, influencing N2O emission. The relationships between N2O occurrence and factors regulating it are an important premise for devising mitigation strategies. Here, we evaluated various options in the literature and found that N2O emissions can be effectively reduced by intervening on time and through the method of N supply (30-40%, with peaks up to 80%), tillage and irrigation practices (both in non-univocal way), use of amendments, such as biochar and lime (up to 80%), use of slow-release fertilizers and/or nitrification inhibitors (up to 50%), plant treatment with arbuscular mycorrhizal fungi (up to 75%), appropriate crop rotations and schemes (up to 50%), and integrated nutrient management (in a non-univocal way). In conclusion, acting on N supply (fertilizer type, dose, time, method, etc.) is the most straightforward way to achieve significant N2O reductions without compromising crop yields. However, tuning the rest of crop management (tillage, irrigation, rotation, etc.) to principles of good agricultural practices is also advisable, as it can fetch significant N2O abatement vs. the risk of unexpected rise, which can be incurred by unwary management.
