Soil erosion and nutrient depletion have been the major challenges in Ethiopia that adversely affect soil fertility and crop productivity. With the aim of curbing land degradation problems, efforts are underway on the implementation of soil and water conservation (SWC) practices. This research investigated the effects of SWC practices on soil properties and crop productivity in cultivated lands of Bashe micro-watershed, Wolaita Zone, Southern Ethiopia. Data were collected from five different practices viz. non-conserved land, physical SWC (2 and 5 years age); and physical SWC integrated with biological practices (2 and 5 years age). The result revealed that integrated SWC for 5 years reduced the soil bulk density; and increased soil pH (5.87 to 6.60), organic carbon (1.34 to 1.74%) and available phosphorous (8.06 to 25.23 mg kg−1) by 12%, 30% and 203% compared to non-conserved land, respectively. Agronomic analysis also indicted that SWC practices significantly (p < 0.05) enhanced plant height, tiller formation, spike length, thousand seed weight, biomass, and grain yield of wheat. Integrated SWC for 5 years increased grain yield by 72.8% than control. It is concluded that SWC practices have positive impacts on soil and crop productivity of cultivated lands; however, their effect is more pronounced when physical SWC practices are integrated with biological SWC practices and at a longer establishment.

Potassium (K) availability depends on exchangeable K and relative amounts of other cations. Yet, the latter has mostly been overlooked. Thus, this study was conducted to evaluate availability and spatial distribution of soil K in Nitisols of Wolaita area, southern Ethiopia, with particular regard to emphasis on assessing the potential for magnesium (Mg)-induced K deficiency. About 789 soil samples were investigated and mapped using ordinary kriging method. The result showed that 14.8% of the samples were K-deficient based on exchangeable K rating, whereas the K deficiency due to antagonistic effects of Mg was 54%. The spatial analysis also revealed that 68% of the study area (i.e., 57, 120 ha) has shown Mg-induced K deficiency. The finding is against the long belief that soils of the study area and the country contain sufficient quantity of K. The findings of this study imply the need for inclusive approach while assessing the K status of soils and also call for greater attention toward K fertilizer intervention that was not in place in the study area. Nonetheless, further study including fertilizer application rates is suggested.

Understanding the landscape features of agricultural lands and soil management practices is pertinent to verify the potential and limitations of the soil resources; and devise relevant land management strategies. However, information is lacking in Wolaita, Southern Ethiopia. Thus, this study aimed at investigating the physiographic characteristics of agricultural lands, farmers’ soil fertility management practices and their influences on soil fertility and crop productivity was conducted. The survey involved 789 randomly sampled agricultural lands. Soil sample as well as data on slope, topography, land use, crop rotation, fallowing, cropping intensity, crop residue management, fertilizer use and farmers’ estimated crop yield were collected and evaluated. The result indicated that agriculture has been practiced under diverse slope positions (1–58%). This significantly influenced most of soil physico-chemical properties in which an increase in soil bulk density, and decrease in available phosphorous, exchangeable calcium, extractable boron, copper, iron and zinc with an increase in slope positions were recorded. Furthermore, continuous cultivation without any fallow periods and complete crop residue removal (96%) were common practices. Fertilizer use was not sufficient. The average use (kg ha−1) was 30 and 9 for di-ammonium phosphate (DAP) and urea, respectively, and about 89% of study area received manure below 1.5 t ha−1. All these limitations made farmers to experience lower crop yield than the national average estimates. Based on the result, it is possible to conclude that the following soil management interventions such as soil conservation, application of sufficient organic and inorganic fertilizers are recommended to restore the soil fertility and improve crop productivity.

This study investigates the soil–plant nutrient status and relationship in Wolaita, Southern Ethiopia. Maize leaves, soil samples and field history were collected. The result indicated that continuous cultivation without fallowing, complete crop residue removal and inadequate fertilization were common practices. The soil was low in organic carbon, total nitrogen, available phosphorus, potassium, sulfur, boron and copper. Tissue analysis indicated 100, 84, 54 and 28% deficiency of nitrogen, phosphorus, potassium and copper, respectively. Significant and positive correlations (r = 0.70, 0.40 and 0.50) of soil phosphorus, calcium and copper with tissue content were observed. Soil pH was correlated with tissue phosphorus (r = 0.4), iron (r =—0.3) and manganese (r = −0.7). Overall, the levels of calcium, magnesium, iron, manganese and zinc were adequate for maize. Therefore, fertilizer application addressing nitrogen, phosphorus, potassium and copper deficiencies is recommended for the study area.

This study assesses soil spatial variability and maps fertilizer types using geostatistics. A total of 789 soil samples were collected from Wolaita area, Southern Ethiopia. Ordinary kriging was employed. The result considering coefficient of variation exhibited diverse soil variability (10% to 236%). Exponential semivariogram model described spatial structure of organic carbon (OC), total nitrogen (N), phosphorus (P), magnesium (Mg), boron (B), iron (Fe), zinc (Zn), cation exchange capacity (CEC) and potassium(K)/Mg. Semivariogram model was spherical for pH, calcium (Ca), manganese (Mn), and Gaussian for sulfur (S) and K. Spatial dependence was strong (Cu, Fe and Zn), moderate (pH, OC, N, S, Ca, Mg, B, Mn and CEC), and weak (P and K). Autocorrelation was between 276 and 15,118 meters. Overall, 46% of nutrients (N, P, K, S, B, and Cu) obtained from soil were deficient. Thus, for site-specific nutrient interventions, three fertilizer types (NPKSBCu, NPSBCu, and NPKSB) are suggested.

Soil quality serves as the basis for both food security and environmental sustainability. To optimize production and implement soil management interventions, understanding the state of the soil quality is fundamental. Thus, this study was conducted to assess the soil quality of arable lands situated in the Nitisols and Luvisols using different assessment techniques. A total of 57 georeferenced soil samples were taken at a depth of 20 cm (18 from Nitisols and 39 from Luvisols land). The soil samples were analyzed for particle size distribution (PSD), texture, pH, organic carbon (OC), total nitrogen (TN), available phosphorus (P), sulfur (S), exchangeable bases (calcium (Ca), magnesium (Mg), and potassium (K)), soil micronutrients (boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn)), and cation exchange capacity (CEC). The techniques used to estimate soil quality includes principal component analysis (PCA), a normalized PCA, and common soil parameters (soil texture, pH, OC, N, P, and K). The results were expressed in terms of soil quality index (SQI). In addition, the soil fertility/nutrient/index (NI) approach was used. The result showed that the SQI values using the common parameters approach were 0.17 and 0.30 for the lands belonging to Nitisols and Luvisols and categorized as very poor (<0.2) and poor (0.2–0.4) quality soils, respectively. PCA-SQI and normalized PCA-SQI values for lands in the Nitisols were 0.36 and 0.42, while for Luvisols they were 0.38 and 0.40, respectively. The soil quality of lands in the Luvisols was rated low (0.38–0.44), while lands in the Nitisols qualified under very low (<0.38) and low soil quality, respectively. In addition, the value of 1.42 and 1.78 in their order for lands belonging to Nitisols and Luvisols were recorded using the NI method that indicated low and medium soil quality. In conclusion, PCA and common soil parameters techniques regardless of soil types offered consistently similar information and could be taken as useful techniques for aiding soil management interventions. Furthermore, the result also calls for the need for applying soil management practices.