Plant Science

Biography

Biography: Leon D van Rensburg

Abstract

Statement of the Problem: Irrigation through its addition of salts poses a continuous threat to the functioning of natural resources. Estimates indicated that of the total land being irrigated in South Africa, 1-12% is severely waterlogged or salt affected, and 5-20% moderately affected. The affected areas need to be reduced through sound water management. Fortunately, recent advances in EMI technology opened new opportunities for site-specific crop management. The objectives of this study were (i) to evaluate the reliability of the EM38-MK2 to infer soil properties, like particle sizes, electrical conductivity (EC), sodium adsorption ratio (SAR) and soil water, and (ii) to delineate salt affected zones. Methodology & Theoretical Orientation: The 56 ha crop field is located on the banks of the Vaal River in the Northern Cape Province, South Africa. The long-term water quality of the river is good (EC of 52 mS m^⁻¹ and sodium adsorption ratio of 1.2). The soils of the field vary from sandy to clay. The field was scanned with an EM38-MK2 during September 2016 to a depth of 1.5 m with inter-row spacing of 20 m. Twelve soil profiles were sampled to a depth of 1.5 m over 0.3 m increments. The soils were analyzed for soil water, particle sizes and the saturated paste was used for measuring EC, cations (to calculate SAR) and pH. These values were then correlated with the apparent EC recorded by the EM38-MK2. Findings: Results showed that all the soil properties, except pH, correlated significantly with the measured ECa. Spatial maps for the properties were drawn and the salt affected areas delineated. Conclusion & Significance: The research demonstrated that the EM38-MK2 can be used to infer the spatial distribution of salts in crop fields, which is a critical step in the amelioration proses.