Short-Term Effects of Combining Minimum Tillage and Manure Application on Water Retention Curve and Pore Size Distribution of a Ferralsol in Limpopo Province of South Africa

Little is known how the combination of minimum tillage and manure affects soil hydraulic properties. The aim of this study was to investigate the effects of combining minimum tillage (MT) and cattle manure application on soil water retention curve (SWRC), van Genuchten (vG) equation parameters, soil pore size distribution (PSD) and soil bulk density. Manual form of MT was tested. The study was configured as split plot design with tillage (conventional (CT) and minimum (MT)) as main plots and manure application rate (0, 5, 10 t/ha) as subplots. Undisturbed soil samples were collected from 0-5-, 10-15-, and 20-30 cm depths and subjected to different matric potentials for the determination of SWRC. The SWRC was fitted to vG equation using the RETC code. Equivalent pore size diameters were estimated from capillary rise equation. Compared to CT, bulk density in MT was significantly lower at all depths. Manure effects were non-significant. None of the vG parameters were significant in the 0-5 cm whereas the α, n parameters and PSD were significantly influenced by the tillage x manure interaction at 10-15- and 20-30 cm depths, but the results were inconsistent, highlighting the need for long- term experiments and higher manure rates.