Effects of rice husk biochar on selected soil properties and nitrate leaching in loamy sand and clay soil

Biochar is a product of pyrolysis of biomass in the absence of oxygen and has a high potential to sequester carbon into more stable soil organic carbon (OC). Despite the large number of studies on biochar and soil properties, few studies have investigated the effects of biochar in contrasting soils. The current research was conducted to evaluate the effects of different biochar levels (0 (as control), 1% and 3%) on several soil physiochemical properties and nitrate leaching in two soil types (loamy sand and clay) under greenhouse conditions and wet-dry cycles. The experiment was performed using a randomized design with three levels of biochar produced from rice husks at 500 °C in three replications. Cation exchange capacity increased significantly, by 20% and 30% in 1% and 3% biochar-amended loamy sand soil, respectively, and increases were 9% and 19% in 1% and 3% biochar-amended clay soil, respectively. Loamy sand soil did not show improvement in aggregate indices, including mean weight diameter, geometric mean diameter, water stable aggregates and fractal dimension, which was contrary to the results for the clay soil. Rice husk biochar application at the both rates decreased nitrate leaching in the clay soil more than in the loamy sand. Our study highlights the importance of soil type in determining the value of biochar as a soil amendment to improve soil properties, particularly soil aggregation and reduced nitrate leaching. The benefits of the biochar in the clay soil were greater than in the loamy sand soil. Keywords: Soil incubation study, Carbon sequestration, Biochar rates, Soil texture, Water stable aggregat

Land leveling and cover cropping impacts on chemical and biological properties of paddy soil

Aim of study: To examine the impact of solitary land leveling and its combination with cover cropping on the chemical and biological characteristics of paddy soil. Area of study: This research focused on paddy fields located in Guilan Province, situated in northern Iran. Specifically, two sites were chosen for investigation, where land leveling had been conducted 5 years and 2 years prior to this study, respectively. Furthermore, cover cropping was implemented during the second year after the latter area's land leveling. Material and methods: A total of 80 composite soil samples were collected, with 20 samples gathered from both leveled and unleveled plots at the designated study sites. Various soil chemical and biological properties such as organic carbon, total nitrogen, available phosphorus, exchangeable potassium, microbial respiration, and biomass carbon were quantified. Subsequently, a paired t-test was employed to analyze the impact of land leveling and the combined effects of land leveling with cover cropping on soil attributes. Main results: The study revealed that five years after land leveling, there was a significant decrease in organic carbon, total nitrogen, microbial respiration, and biomass carbon. In contrast, the area leveled and cover cropped for two years exhibited higher levels of these attributes compared to adjacent unleveled parcels. Research highlights: This study highlights the distinct effects that solitary land leveling and land leveling combined with sustainable practices like cover cropping have on soil attributes