Changes in Soil Water Retention and Micromorphological Properties Induced by Wetting and Drying Cycles

Abstract

Wetting and drying (W-D) cycles are responsible for significant changes in soil structure. Soil often undergoes irreversible changes affecting infiltration and solute retention through W-D cycles. Thus, it becomes essential to evaluate how soils under natural conditions are altered by W-D cycles. This study analyzed two non-cultivated (from grassland and secondary forest) Oxisols (Typic Hapludox and Rhodic Hapludox) of different textures under 0 and 6 W-D cycles. The main results obtained showed that soil water retention was mainly affected in the driest regions (smaller pore sizes). The contribution of residual pores to total porosity increased with 6 W-D and transmission pores decreased in both soils. The Rhodic Hapludox presented differences in water content at field capacity (increase), while the Typic Hapludox showed alterations at the permanent wilting point (increase), affecting the amount of free water (Rhodic Hapludox) and water available to plants (Typic Hapludox). Both soils showed increases in imaged porosity with 6 W-D. Variations in the contribution of small and medium rounded pores, mainly large and irregular (with an increase in both soils not significant in the Rhodic Hapludox), could explain the results observed. The micromorphological properties were mainly influenced by changes in the number of pores, in which smaller pores joined, forming larger ones, increasing the areas occupied by larger pores. Overall, this study showed that the investigated soils presented pore systems with adequate water infiltration and retention capacities before and after continuous W-D cycles.

Evaluation and classification of soil infiltration capacity, hydrologic soil groups and suitability rating classes for irrigation application of fadama soils

“…This partly explains the lowest infiltration rates of soil units 3, 4, and 10 (2.4-3.9 cm/hr). Similarly, the functional infiltration recorded from soil units 9, 11, 13, 14, and 15, could be partly attributed to the surface wetting front condition of the soil as noted in other similar studies [9,17,47].…”

“…Soil units 9, 11, 13, 14, and 15 have moderate infiltration values, which ranged between 5.75 cm/hr and 8.85 cm/hr. This result suggests that soil properties could have influenced the hydrological behaviour between the soils of the study sites, and probably affected the wetting and drying cycles [17].…”

“…The promotion of faster/slower water infiltration into soils of the individual sites, depends largely on soil physical properties [18], primarily due to the fact that the dryness and wetting condition of soil texture and soil structure control a great part of soil profile development [17,[34][35]. Physically, the surface soil conditions of the study sites vary significantly in terms of dryness and wetness at the time of assessment in the field.…”

“…However, the development and growth performance of crops growing under fadama irrigation depend significantly on the available groundwater in the soil [16]. Agricultural production under irrigation principles and practices required the full knowledge of the underground soil-water relationship for proper water use and management [17]. Without monitoring water movement in the soil through for example infiltration studies, this knowledge cannot be attained anymore [18].…”

Land Valuation Systems in Relation to Water Retention

“…Here, farming practice is unclear, since a certain form of agrotechnical interventions can have a positive impact on this property. According to the research undertaken, the size of pores can influence water retention in soil in the driest areas in particular [48], and although this would have a positive effect, it is a long-term process and the end result may be more negative for many crops, since clay soil is unsuitable for many food crops. Finally, in terms of significant influences, it is also a good idea to note the conflicting influence of humus in the soil.…”