Influence of Organic and Inorganic Soil Amendments on Temporal Improvement of Formation of Soil Aggregates in Eleusine coracana Cultivated soil

Abstract

Soil aggregation is related to biological, physical, and chemical activities in soil. Agriculture-based soil amendments may enco-mpass hydrophobic properties that interfere with soil aggregation. This study examined the influence of soil amendments and their hydro-phobicity on soil aggregation in Eleusine coracana-grown soil. Cattle manure (CM), hydrophobic leaf litter (Casuarina equisetifolia, CE), biochar from CE (BCCE) (450 ℃, 20 minutes), and quick lime (CaO) were mixed with sieved surface soil (3% CM, 3% CE, 3% BCCE and 1% CaO in air-dry weight basis). The control was primarily surface soil (Rhodudults with grass-dominated vegetation). The study involved five treatments (triplicated), including the control. The hydrophobicity was examined using the water drop penetration time (WDPT) test. Initially, CM and CE-added samples were slightly repellent, while control, BCCE, and CaO-added samples were non-repellent. The samples were filled into the polybags (3750 g per bag) and moistened up to 80% of the soil’s field capacity. Sprouted E. coracana seeds were transplanted in polybags, and the moisture content was maintained by adding water (first 2 weeks: once every 4 days; after two weeks: twice a week). After 10 weeks, formed aggregates were separated by sieving. The percentage of total aggregate formation was calculated as the total soil in a polybag (air-dry basis). The highest and the lowest aggregate formation were recorded in the CE-amended sample (21.4%) and BCCE-added sample (4.1%), respectively. The CE and CM-amended samples (slightly repellent mixtures) showed significantly higher aggregate formation compared to the control (p<0.05). The BCCE-added sample showed the lowest aggregate formation despite biochar being a soil improve-ment agent. The exact mechanism for the reduced aggregation by BCCE has not been fully addressed; it can be related to the presence of sodium, which discourages flocculation. Future studies considering various soil amendments and biochar applications would provide a more comprehensive understanding.