Abstract:
Stability of aggregates plays a crucial role in determining the physical health of soils. Soil
amendments applied in agriculture may induce various properties, such as soil water
repellency (SWR), which can influence the stability of aggregates. This study examined the
effects of different soil amendments and their SWR on aggregate stability in Eleusine
coracana (finger millet) grown soil. Cattle manure (CM), water-repellent leaf litter
(Casuarina equisetifolia, CE), CE-derived biochar (BCCE), and quick lime (CaO) were mixed
with sieved surface soil (3% CM, 3% CE, 3% BCCE, 1% CaO). Only soil was used as the
control. The experiment followed completely randomized design with treatments in
triplicate. Soil mixtures were filled into polybags (3750 g per bag) while maintaining the
homogeneity of the bulk density for treatments. The moisture content was initially
maintained at 80% of the field capacity of soil (450 cm3 per polybag) to ensure initial
homogeneity. Germinated E. coracana seeds were transplanted and kept in a protected
house. Initially, the SWR of mixtures was determined using the water drop penetration
time (WDPT) test. At the 10th week, all aggregates were separated into two-equal (7 cm)
layers (TL: top layer and BL: bottom layer) of each polybag and the percentage of water
stable aggregates (% WSA) was determined using wet sieving apparatus. The 3% CE
amended sample showed slight SWR, while others were non-repellent. The 3% CE
amended sample showed the highest % WSA (TL: 99.21% and BL: 99.23%, p<0.05) due to
the high initial hydrophobicity of CE. The control showed the lowest % WSA (TL: 76.17%
and BL: 75.52%, p<0.05). Results showed that the slightly repellent 3% CE significantly
enhanced the % WSA. SWR reduces the water entry into the aggregates and lowers
pressure buildup, enhancing their resistance to disruption. Results validation under field
conditions is required to ensure field applicability.
