Adsorption isotherm is essential for predicting its mechanisms, which are important for potassium (K) fertilizer application and to recommendation appropriate rates for acidic soils. Thus, the objective of this study was to evaluate K adsorption characteristic of the selected soils by comparing different adsorption models with soil properties of the soil in different districts (Sodo Zurie, Damot Gale, Damot Sore and Boloso Sore) in the Wolaita Zone of Southern Ethiopia. Four adsorption isotherms are: Langmuir, Freundlich, Temkin, and Van Huay were used to describe adsorption processes. Composite surface (0-20 cm) depth soil samples from four districts sites were collected. The results revealed that the K adsorption data coincide with both models with (r² = 0.99). However, Freundlich model was better in describing K adsorption than the other model. The adsorption maxima(ad_(max), distribution coefficient, buffer capacity (BC), and adsorption capacity(a_(capacity) values of soils ranged from -333 to334.5,0.54 to78.7,159.9 to 389.3, and 327 to 417mg Kkg^-1 respectively, these results showed that Sodo Zurie, Bolos Sore and Demote Sore were effective model parameters. Van Huay a_(capacity) 417mg Kkg^-1 while the bonding energy constant Langmuir is -0.075mg Kkg^-1 in Bolos Sore soil compared to other soils, which were found to be more valuable in discriminating between high K adsorption soils. Correlation between some soil properties with ad_(max) were positively a highly correlated with clay, pH, organic carbon (OC) and exchangeable potassium with r² = 0.92**, 0.93**, 0.95** and 0.96 ** respectively, but negatively correlated with bonding energy with r²= -0.79, -0.80,-0.77 and -0.72 respectively, while calcium carbonate (CaCO3) was very highly correlated with ad_(max) r²= 0.99***). The Freundlich constant, Temkin BC, and Van Hauy a_(capacity) were correlated with CaCO3 content soils with r²=0.12,-0.01,and 0.12,respectively, while slope (1/n) was significantly negatively correlated with soil cation exchange capacity (CEC), CaCO₃, clay contents and exchangeable K and Mg²⁺ with r²= 0.04, -0.67, -0.78, -0.69, and –0.69, respectively. These findings reveal the extent of K depletion in the soils of Wolaita providing a baseline for K rates required for crop production and validation of all models through real-time experiments in the field; this is recommended before the models are used on a large scale basis.

Quantity-intensity (Q/I) characteristics are among conventional approaches for studying potassium dynamics and its availability. This was assessed to determine availability in four districts: namely, Sodo Zuria, Damot Gale, Damot Sore, and Boloso Sore, at three different land use systems (enset-coffee, crop land, and grazing land). Fractionation and dynamics of K sources were studied in soil samples, which were collected from 020cm depth of each land system. The study revealed that water extractable K (H₂O-K) concentrations ranged from 0.13 to 0.34 cmolc kg⁻¹ soils at enset-coffee and grazing land use systems, respectively, and had a mean value of 0.28 cmolc kg⁻¹ soils ammonium acetate extractable (NH₄OAC-K) and nitric acid extract (HNO₃-K) had a mean value of 0.25 cmolc kg⁻¹ soils. In this study, the means of nonexchangeable- and exchangeable-K concentrations were of 0.11 and 0.14 cmolc kg⁻¹ soils for land use types. Significant correlations were found between soil properties and Q/I parameters and among equilibrium solution parameters and Q/I parameters. There was no significant variation among the mean quantity values of the soils. The soils had higher change in exchangeable-K and potential buffering capacity than the enset-coffee land use soils, and the cop land had the highest values for these parameters. However, the enset-coffee land use soils had higher K-intensity. Therefore, application of site specific soil fertility management practices and research can improve soil K status and Q/I parameters to sustain productivity soils.

Bambara groundnut, a future emerging legume, is usually known as a poor man’s crop or as “women’s crop” and newly noted as crop for new millennium. In this context, a field experiment was conducted during 2019/20 cropping season at Sonka testing site of Asosa zone in northwestern Ethiopia with objective to estimate the variability of Bambara groundnut genotypes with respect to important quantitative and qualitative traits. Treatments consisted in 20 accessions collected from five distracts of Benishangul Gumuz province in northwestern Ethiopia. The treatments were laid out in a randomized block design with three replications. All the qualitative characteristics recorded for genotypes showed different modalities and frequencies at vegetative stage with 70.12% of the fully expanded leaflet colour, 74.26% oval terminal leaflet shape, 76.24% petiole green colour, 78.22% stem green colour, 88.27% sparse hair on their stems, 70.41% spreading types, 81.33% rounded base with a point at the top, 90.11% yellowish brown pods at harvest, and 90.06% oval shaped seeds. With respect to quantitative traits, genotypes AMN/04/013, AMN/04/014, AMN/04/015, AMN/04/019, and AMN/04/020 gave relatively higher grain yield (>2000 kg/ha) with the highest grain yield recorded for genotype AMN/04/016. Thus, these genotypes showed relatively better adaptation at tested location. Higher correlation values were observed for days to maturity, plant height, number of stems per plant, pods per plant, seed per pod, and HSW, indicating that these traits are very important to be used in selection for the crop improvement. Agronomic and morphological evaluations have provided more accurate estimation of genetic diversity, the raw material of plant breeding. In general, this study enabled to determine how the influential traits direct to improve Bambara groundnut genotypes.

A field experiment was conducted at Damot Gale District, Wolaita Zone, SNNPRS to evaluate the response of barely varieties to nitrogen and phosphorus fertilizer application since the response varies from location to location due to several factors. Thus, there is a need to determine specific nitrogen and phosphorus fertilizer requirement of specific variety. The barley varieties (HB1370 and Shage) were used as test crop and the experiment contained factorial combination of four levels of N/P (0/0, 23/10, 46/20, 69/30 kg ha^-1) and was laid out in randomized complete block design with three replications. The results from this study indicated that nitrogen and phosphorus fertilizer showed no significant effect on number of days to heading while number of fertile tillers, total biomass and yield were significantly increased by application of nitrogen and phosphorus. However, the effects of nitrogen and phosphorus were significant (P < 0.05) on plant height, spike length, number of seeds per spike and grain yield. In general, grain yield tended to be higher under NP 69/30 kg ha^-1 treatment (2.02t/ha). In contrast, the lowest grain yield (0.86t/ha) was obtained from 0/0 NP treatment, although the interaction effects of nitrogen and phosphorus were significant on treatments with varieties and balanced amount of nitrogen and phosphorus. The future studies should articulate towards the studies involving more varieties, multi-location and additional rates of nitrogen and phosphorus applications, under diverse management practices such as research and farmer’s field’s conditions, which may facilitate fine-tuning of fertilizer recommendations.

Although Ethiopia is a center of barley domestication and diversity, and barley has an important place in African dry land agriculture due to its resilience to wide-ranging stresses; the average yield continues to be low, mainly due to low soil fertility. Site-specific fertilizer recommendation for barley in Wolaita, Ethiopia, has a pivotal role not only in optimizing barley productivity but also in maintaining ecological balance. Thus, this study was conducted to assess the relationship between grain yield and site-specific nutrient requirements for a target yield using a Quantitative Evaluation of the Fertility of Tropical Soil (QUEFTS) model. The data input was derived from field experiments predominantly in the major barley production areas of Wolaita, Ethiopia. Calibration of the QUEFTS model was estimated by describing the two boundary lines of the maximum accumulation and dilution of N, P, and K contents targeting the barley grain yield. The study revealed that balanced nutrient requirements estimated by the QUEFTS model had a good correlation between the simulated and observed grain yields (r2 = 0.82*, 0.88*, and 0.83*) for different sites, namely, Doga Mashido, Kokate, and Gurimo Koyisha, respectively, while evaluation of the QUEFTS model by U-Theil values showed a good agreement between the simulated and observed yields. Therefore, the study concluded that the QUEFTS model can be used for determining nutrient requirements of crops, thereby contributing to the development of site-specific fertilizer recommendations.

Blended Nitrogen, Phosphorus, Sulfur, and Boron fertilizer calibration foxr optimum common bean (Phaseolus vulgaris L.) varieties yield was used to assess the effect of different rates of blended fertilizer on growth, yield and yield components, and nutrient use efficiency of common bean varieties and to identify economically feasible rates of blended fertilizer at Meskan District, Southern Ethiopia during 2020 crop season. The experiment had six treatment levels of blended fertilizer (0, 50, 100, 150, 200, and 250 kg·ha⁻¹), and two common bean varieties were arranged in a randomized complete block design with three replications. Soil samples of the experimental plots were analyzed and used as blended fertilizer calibration to estimate soil nutrient supplies and recommend fertilizer. The results revealed that growth, yield, and yield components were highly significantly affected by the main effect of varieties and application of blended NPSB rates. The interaction of varieties and blended fertilizer shown a significant effect on all parameters. The partial budget analysis indicated that the highest net benefit of 67665 ETB ha⁻¹ was obtained from the Nasir variety with the application of 100 kg·ha⁻¹. Therefore, growing the Nasir variety with blended fertilizer rates of 100 kg·ha⁻¹ is economically feasible for the studied soil type and different locations.