Micronutrients are important for crop growth, production and their deficiency and toxicity affect crop yield. However, the up dated information about their status and spatial distribution in Ethiopian soils is scarce. Therefore, fertilizer recommendation for crops in the country has until recently focused on nitrogen and phosphorus macronutrients only. But many studies have revealed the deficiency of some micronutrients in soils of different parts of Ethiopia. To narrow this gap, this study was conducted in Kedida Gamela, Kecha Bira and Damboya districts of Kambata Tambaro (KT) Zone, Southern Ethiopia, through assessing and mapping the status and spatial distribution of micronutrients. The micronutrients were extracted by using Mehlich-III multi-nutrient extraction method and their concentrations were measured by using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The fertility maps and predication were prepared by co-Kriging method using Arc map 10.0 tools and the status of Melich-III extractable iron (Fe), Zinc (Zn), boron (B), copper (Cu) and molybdenum (Mo) were indicated on the map. The extracted Fe ranged from 50.04 to 209.72 mg/kg, 60.08 to 240 mg/kg and 46.84 to 412.23 mg/kg in Kedida Gamela, Kecha Bira and Damboya districts soils, respectively. Zn ranged from 1.3 to 28 mg/kg, 0.9 to 47 mg/kg and 1.0 to 39 mg/kg for Kedida Gamela, Kecha Bira and Damboya districts, respectively. The calculated manganese activity index (MnAI) indicated that Mn is in excess and even toxic. B ranged from 0.02 to 1.83 mg/kg, 0.4 to 1.44 mg/kg and 0.06 to 2.03 mg/kg in soils of Kedida Gamela, Kecha Bira and Damboya woredas, respectively indicating that most of soils were deficient in B. Cu ranged from 0.6 to 2.9 mg/kg, 0.5-1.44 mg/kg and 0.8 to 3.4 mg/kg in Kedida Gamela, Kecha Bira and Damboya districts indicating its status fall between low and optimum category. Mo ranged from 2.21 to 18.71 mg/kg in the soils of the study area indicating that all soils were sufficient in Mo content. The means of all micronutrients except B showed significant differences among districts and showed moderate spatial dependences. The range of semivariogram for all studied micronutrients was greater than the average sampling distance indicating that it was adequate enough to catch spatial variability of them. In order to strengthen this result, plant sample analysis and calibration of micronutrients with plant response are recommended.

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Potassium dynamics of soils is constituted by constantly changing relationship between soil K forms, and this relation is affected by some soil physical and chemical properties. Most Sidama (south Ethiopia) farmers grow enset crops which have high K requirements. The soils were collected from Awassa-Zuriya and Dale districts; 'Woinadega' (warm subtropical climate) and Hula district 'Dega' (wet, cool temperate climate). Overview of K dynamics in soils via Quantity-Intensity (Q/I) curves was used to evaluate the dynamics of K in fifteen soil samples representing the enset farming systems of Sidama. All of the Hula district soils and half of the Dale district soils had low percent K saturation. There were significant correlations between some soil properties and Q/I parameters and among equilibrium solution parameters and Q/I parameters. Variations among the mean quantity (±∆K) values of the soils were not significant. The Dale and Hula district soils had higher K intensity than the Awassa-Zuriya district soils; where the Hula (Adola kura kebele) soil had the highest value. Therefore, the Dale and Hula district soils will require frequent and split K applications since they have lower capacity to maintain long-term supply of K. On the other hand, Awassa-Zuriya district soils had high K quantity than the Dale and Hula district soils. This shows that the Awassa-Zuriya district soils have a higher potential to supply K for a longer period of time from the exchangeable pool. However, the AwassaZuriya district soils require less frequent and higher K fertilization to saturate the exchangeable pool to meet immediate potassium requirement of crops. The low equilibrium activity ratio of potassium and low potassium replenishing capacity of nearly all of the soils studied also indicated the need for K application.

Information on soil fertility status of acid soil of a particular area as affected by land use type is important for developing sound soil management systems for improved and sustainable agricultural productivity. The main objective of this study was to assess the fertility status and effect of land use change on soil physicochemical properties. In this study, adjacent three land use types, namely, enset-coffee, crop, and grazing land use were considered in four districts (i.e., Bolos Sore, Damot Gale, Damot Sore, and Sodo Zuria) of Wolaita Zone, southern Ethiopia. Soil samples were collected from a depth of 0–20 cm from each land use type of the respective districts for physicochemical analyses. The results showed that land use types significantly affected ( P ≤ 0.05 ) soil properties such as bulk density, available P, exchangeable potassium, exchangeable acidity, exchangeable bases (Na, K, Ca, Mg), exchangeable acidity, and CEC. Besides, soil pH, OC, and TN were influenced significantly ( P ≤ 0.05 ) both by districts and land use types. The very strongly acidic soils were found predominantly in the crop and grazing lands whereas a neutral acidity level was found in the enset-coffee land use type of four districts. In conclusion, the study proves that land use type change within the same geographic setting can affect the severity of soil acidity due to over cultivation and rapid organic matter decomposition. Finally, the study recommends an in-depth study and analysis on the root causes in aggravating soil acidity under crop and grazing land use types.

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