Assessing the spatial variability of soil properties in the semiarid areas of Hintalo Wejerat District, Tigray region, Ethiopia

Abstract

Abstract Knowledge of soil spatial variability and mapping is essential. It helps determine the effects of agricultural activities on soil properties, develop appropriate soil management techniques, and promote site-specific agricultural practices. The present study was conducted in the semiarid areas of Northern Ethiopia in the Gumselassa watershed to assess the status, nutrient indexing and variability of selected soil properties. Based on geology, soil type, slope gradient and to a lesser extent soil management practices ten land mapping units (LMUs) were delineated. Soil samples were collected from two depths (0–15 and 15–30 cm). Overall, 60 composite soil samples were collected from the 10 LMUs. The soil samples were air-dried, crushed and passed through a 2 mm sieve before analysing the soil's physical and chemical properties. The results revealed that all the analysed soil properties, except bulk density and porosity, varied significantly (P < 0.05) among the LMUs. The soils of all LMUs are strongly alkaline (ranging from 7.8 to 8.5), low in soil organic matter (OM) content (< 3%) and total nitrogen (TN). Similarly, the available phosphorus (AP), available (Fe) and zinc (Zn) contents of all LMUs were very low. Based on the nutrient indices, the soil of the watershed had low OM (1.17%), TN (1.27%), AP (1 mg kg−1) and high Ex. K (2.97 cmol ( +)/kg). The study concluded that the overall fertility status of the soils was deficient and unable to support sustainable crop production under smallholder farming. Consequently, integrated soil fertility management practices which help build up the soil OM content and essential nutrients; and ameliorate the elevated alkaline soil pH should be implemented. Future studies should focus on soil spectroscopy and geostatistical models due to the high cost of soil wet chemistry and environmental pollution.

Keywords

• Environmental factors
• Land mapping unit
• Nutrient indexing
• Semiarid areas
• Soil fertility
• Soil properties