Abstract:
Soil physical degradation and rapid moisture loss are major constraints to vegetable
production in the dry zone of Sri Lanka. Although mulching is widely used to conserve
soil moisture, information on its effects on soil physical properties under local
conditions is limited. This study evaluated the impact of different mulching materials
on soil moisture storage, soil temperature, bulk density, and soil organic matter during
Knol-khol (Brassica oleracea var. gongylodes) cultivation in Kilinochchi District, Sri
Lanka. A field experiment was conducted using a Randomized Complete Block Design
(RCBD) with four treatments: paddy straw mulch, palmyra dry leaves mulch, polythene
mulch, and a no-mulch control, each with three replicates. Organic mulches were
applied at a thickness of 15 cm one week before transplanting. Soil moisture storage,
soil temperature, bulk density, and soil organic matter were measured throughout the
cropping period using standard field and laboratory methods. Data were analyzed
using analysis of variance (ANOVA), and treatment means were compared using
Dunnett’s test at a 95% confidence level (p ≤ 0.05). Mulching significantly improved
soil physical properties. Mean soil moisture storage was highest under palmyra dry
leaves mulch (23.8 ± 1.9%), followed by paddy straw (21.6 ± 1.7%), polythene mulch
(20.2 ± 1.5%), and the control (17.4 ± 1.6%). Organic mulches also moderated soil
temperature, recording lower values under palmyra dry leaves (27.1 ± 0.8 °C) and
paddy straw (27.8 ± 0.9 °C) than under polythene mulch (29.4 ± 1.0 °C) and the control
(30.2 ± 1.2 °C). Bulk density was lowest under palmyra dry leaves (1.42 ± 0.05 g cm⁻³),
while soil organic matter increased to 1.26 ± 0.08% compared with 1.02 ± 0.05% in the
control. The results demonstrate that organic mulching, particularly palmyra dry
leaves, is an effective and sustainable option for improving soil physical conditions,
conserving moisture, and supporting Knol-khol cultivation in dry-zone environments.
