Impacts Of Sustainable Land Management Practices On Soil Physical Properties And Agricultural Drought Adaptation In Eastern Cape, South Africa
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Intensive removal of soil resources through the use of repeated tillage, crop residue removal, intensive aftermath grazing in croplands, biomass burning, use of crop straw and animal pats for fuel, deforestation and mono-cropping practices cannot ensure farm productivity and food security in the coming years. Reasons for low yields in rain fed agriculture include the occurrence of dry spells during the growing season and lack of sustainable agriculture management practices that do not adversely affect the soil properties. This study investigated the effects of a sustainable land use management practice, CA practice on soil moisture, cumulative infiltration, hydraulic conductivity, soil bulk density and infiltration rate on a sandy loam soil at Fort Hare experimental farm in Eastern Cape, South Africa. Also the study analyzed long-term (1980-2016) monthly rainfall data on a monthly and annual basis to assess water shortage occurrence. The experiment was laid out as a split split-plot design in an RCBD replicated three times with 18 treatment combinations. The main plots were allocated to tillage at two levels (conventional tillage and no tillage). The sub-plots were allocated to crop rotations at three levels. Crop rotation was practiced in accordance to what the farmers in the locality do. Infiltration and unsaturated hydraulic conductivity were measured using the mini disk infiltrometer, whilst soil samples for bulk density determination were collected using sampling cores. Soil moisture and temperature were measured using DFM probes. Results obtained revealed that NT resulted in more moisture down the 0 - 30 cm profile (59.87%) compared to CT (55.34%). Application of crop residues also led to higher soil moisture content compared to residue removal. Higher soil moisture was recorded in NT treatments with crop residues followed by CT treatments with crop residues, NT treatments with no residues and the least was in conventional tillage with no residues. Rotation of maize legume and maize led to higher soil moisture than maize fallow maize rotation. Contrary to soil moisture results, cumulative infiltration and hydraulic conductivity were higher in conventional tillage compared to conservation agriculture. Bulk density was lower in conventional tillage practices (1.31g cm-3) compared to conservation agriculture (1.38g cm-3). This was attributed to that infiltration and bulk density measurements were done soon after tillage had been done in the CT practices. Biochar addition and residue retention resulted in more favorable effects on infiltration rate, cumulative infiltration and unsaturated hydraulic conductivity compared to residue removal. Residue type significantly (P < 0.001) affected cumulative infiltration, infiltration rate and unsaturated hydraulic conductivity. This study demonstrated that CA practices improved soil moisture in the crop root zone and this can assist in mitigation of the effect of droughts during critical periods of crop growth. Treatments with residues were also noted to lead to higher soil moisture contents than treatments with no residues. Most of the changes observed are attributed to improved soil structural condition resulting from practicing conservation agriculture. However, there is a need for more research as the impacts of conservation agriculture have been reported to be realized after several years of adoption. From the 37 years of rainfall data analyzed, 19 % were found to be drought years, 16 % wet years and 65 % normal years. It was observed from the study that the 1 month SPI, 3 months SPI and 6 months SPI gave progressive indication of water shortage levels. The SPI can therefore be used as a progressive water shortage warning tool, with the 3 month SPI being for indication of agricultural drought occurrence. Depending on the type of crops grown and seasonal lengths a suitable SPI metric can be selected for the monitoring of either water shortage or excess in agricultural production. Periods of water deficit/droughts can thus be mitigated through adoption of CA practices.