Characterization of soils using infrared scanning in South kivu province, Democratic Republic of Congo
Bigabwa, Janvier Bashagaluke
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Understanding soil properties is an essential pre-requisite for sustainable land management. Assessment of soil properties has long been done through conventional laboratory analysis, which is costly and time consuming. Therefore, there is a need to develop alternative cheaper and faster techniques for soil analysis. In recent years, special attention has been given to Infrared Reflectance Spectroscopy and chemometrics. ear Infrared Reflectance (NIR) and mid-infrared (MIR) spectroscopy techniques are rapid, convenient and simple non-destructive techniques for quantifying several soil properties. This study aims to characterized soil based on based on infrared spectroscopy. This method were to predict soil pH, soil organic C, total N, exchangeable AI, Ca, Mg, and K, CEC and soil texture for soil samples collected in Sud-Kivu province, Democratic Republic of Congo. A total of 530 composite soil samples were taken from two locations (Burhale and Luhihi) at two depths (0-20 and 20-40 ern) using a spatially-stratified random sampling design within an area of 100 km2. After minimal sample preparation, the MIR spectrum of a soil takes about two minutes for the analyses. Ddifferences in characteristics were evaluated between the two locations, land use (cultivated vs. non-agricultural land) and soil depth. A random subset of the samples (10%) were analyzed using standard wet chemistry methods, and calibration models developed using MIR data to estimate soil properties for the full soil sample set. Partial least squares regression (PLS) method gave acceptable coefficients of determination between 0.71 and 0.93 for all parameters hence good prediction. Soil organic matter levels were higher in cultivated plots in Luhihi (3.9% C) than in Burhale (3.0% C), suggesting lower levels of soil fertility in the latter area. For both sites, soil pH (water) was generally very low (less than 4.8) This indicates high levels of acidity, which is likely to limit crop production in the area. Phosphorus deficiency was acute for both locations but more for Burhale (2.4 mg P kg') than Luhihi (5.4 mg P kg"). Aluminium toxicity was prevalent in both sites which is attributed to low pH values. The recommended soil management strategies therefore involve liming with dolomite material since Ca/Mg > 4. In both locations, low levels. of Ca and Mg indicate that soils may be susceptible to " deficiencies of both elements. No risk ofK deficiency was observed in the area. These findings suggest new opportunities for monitoring soil quality in the region which can benefit multiple actors in the agricultural and environmental sectors. More efforts are needed to improve the use of these new technologies of monitoring soil and land degradation across developing countries.