Title: Soil organic matter control of water transmission properties of coarse-textured soils under contrasting land-use types in tropical rainforest

Authors: Paul C. Oguike; Brown M. Onwuka; Sunday E. Obalum

Addresses: Department of Soil Science and Meteorology, Michael Okpara University of Agriculture, Umudike, Nigeria ' Department of Soil Science and Meteorology, Michael Okpara University of Agriculture, Umudike, Nigeria ' Department of Soil Science, University of Nigeria, Nsukka, Nigeria

Abstract: Infiltration rate (I) and saturated hydraulic conductivity (K_s) depend on soil organic matter (SOM) in a manner that is poorly known for genetically similar soils of the humid tropics. This study examined I and K_s dependence on SOM under continuous cultivation (CCT), bush fallow (BFL) and secondary forest (SFT) on deep coarse-textured Nigerian soils using linear regressions. Soil texture, SOM and K_s varied by both land use and depth zone, while I was lower under CCT (0.20 cm/h) than BFL/SFT (0.30 cm/h). For K_s, trends were CCT (0.72 cm/h) < BFL (0.82 cm/h) < SFT (1.02 cm/h), and topsoils > subsoils. The SOM was lower in CCT (19.65 g/kg) than BFL/SFT (35.60-39.70 g/kg). Topsoil SOM and subsoil SOM had similar influence on I (82-85%), while SOM influenced K_s less in topsoils (51%) than subsoils (81%). Clay correlated positively with SOM, I and K_s. Land-use practices that promote SOM accretion increase clay-SOM complexation into silt/sand-sized stable aggregates forming 'porous' granular structure in these soils, enhancing their permeability.

Keywords: bush fallow; drainable pores; granular structure; infiltration rate; soil depth zone.

DOI: 10.1504/IJHST.2023.131833

International Journal of Hydrology Science and Technology, 2023 Vol.16 No.1, pp.93 - 106

Received: 02 Mar 2021
Accepted: 15 Feb 2022
Published online: 04 Jul 2023 *

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