Dynamics of soil properties as impacted by contrasting lithology, slope class, and land use types: a case study in semi-arid highlands of northern Ethiopia.

Soil characterization is crucial in creating sustainable platforms for land users to identify areas vulnerable to anthropogenic activities. This study was conducted to investigate the impacts of lithology, slope, and land use on soil properties of a semi-arid highland in northern Ethiopia. Disturbed and undisturbed soil samples collected from 0 to 30 cm depth were analyzed. Most of the assessed physical and biochemical soil properties varied significantly (p < 0.05) with lithology, slope class, and land use type. Shale-originated soils were richer in nutrients than soils of other lithologies. A decrease in slope gradient accounted for an increase in most soil properties, while a reverse trend was observed for sand content, bulk density (BD), water stable aggregates (WSA), mean weight diameter (MWD), structural stability index (SSI), soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP). Silt and clay fractions, total porosity, moisture content at field capacity and wilting point, visual evaluation of soil structure, pH, electrical conductivity, calcium carbonate, exchangeable bases, cation exchange capacity, and percent base saturation were found to be higher for cultivated land soils compared to grass land and shrub land soils. Shrub land soils, in contrast, had higher WSA, MWD, SSI, SOC, TN, and AP relative to grass land and cultivated land soils. In summary, slope class and land use type stood out as the major drivers influencing the dynamics and distribution of soil properties other than lithology and their interactions in semi-arid highlands of northern Ethiopia. Thus, from sustainability point of view and in the light of their nutrient retention capability and limitation, more attention should be paid toward ensuring periodic assessment and sustainable management of soils in steep cultivated lands.

Potentials of legumes rotation on yield and nitrogen uptake of subsequent wheat crop in northern Ethiopia.

Nitrogen has becoming the most limiting nutrient in the northern highlands of Ethiopia due to continuous cropping with application of limited external inputs. To improve soil nutrient availability, farmers have been using legumes in crop rotation. However, the roles of various legumes on subsequent wheat (Triticum aestivum) crop are unknown in northern Ethiopia. The objective of this study was to investigate impacts of legumes on yield and N uptake of subsequent wheat crop. Experiment was conducted at farmer's field with faba bean (Vicia faba L.), 'dekeko' field pea (Pisum sativum var. abyssinicum), field pea (Pisum sativum), lentil (Lens culinaris) and wheat (Triticum spp.) in the first season and all plots were rotated by wheat in the second season. Yield of subsequent wheat crop was recorded and N uptake was analyzed. The result revealed that grain yield and dry biomass yields of subsequent wheat crop were significantly (p < 0.05) higher in the legume-wheat rotations than in the wheat-wheat rotation. The wheat yield is increased by 2196, 1616, 1254 and 1065 kg ha-1 and the N uptake is increased by 71.4%, 51.0%, 49.2% and 29.8% in the faba bean-wheat, 'dekeko'-wheat, field pea-wheat and lentil-wheat rotation plots compared to the wheat continuous cropping, respectively. The findings indicated that legumes improved yield and N uptake of the subsequent wheat crop. Thus, soil fertility management policy need to consider legume crop rotations as nutrient management option to improve sustainable soil fertility and yield.

Soil organic carbon, total nitrogen stocks and CO2 emissions in top- and subsoils with contrasting management regimes in semi-arid environments.

This study aims to investigate soil organic carbon (SOC) and total nitrogen (TN) contents and stocks, CO2 emissions and selected soil properties in croplands, grazing lands, exclosures and forest lands of semi-arid Ethiopia. Sampling was done at 0-30, 30-60 and 60-90 cm soil depths and concentration and stocks of SOC, TN and selected soil properties were determined using standard routine laboratory procedures. There were variations in distribution of SOC and TN stock over 90 cm depth across land use types and locations, decreasing from topsoils to subsoil, with average values ranging from 48.68 Mg C ha-1 and 4.80 Mg N ha-1 in Hugumburda cropland to 303.53 Mg C ha-1 and 24.99 Mg N ha-1 in Desa'a forest respectively. Forest sequestered significant higher SOC and TN stock, decreasing with depth, compared with other land use types. In Desa'a and Hugumburda, the conversion of forest to cropland resulted in a total loss of SOC stock of 9.04 Mg C ha-1 and 2.05 Mg C ha-1, respectively, and an increase in CO2 emission of 33.16 Mg C ha-1 and 7.52 Mg C ha-1 yr-1, respectively. The establishment of 10 years (Geregera) and 6 years (Haikihelet) exclosures on degraded grazing land increased SOC stock by 13% and 37% respectively.

Soil type and fertilizer rate affect wheat (Triticum aestivum L.) yield, quality and nutrient use efficiency in Ayiba, northern Ethiopia.

The blanket NP fertilizer recommendation over the past five decades in Ethiopia did not result in a significant increment of crop productivity. The main lack of success was highly linked to the extrapolating approach of one site success to others without considering the climate, soil, and ecological setting and variations. As a result, a new fertilization approach was desperately needed, and with this premise, new blended fertilizers are now being introduced to replace the conventional approach. Thus, the objective of this study was to examine the effect of NPSZnB blended fertilizer on bread wheat yield attributes, quality traits and use efficiency in two different soil types under rain-fed conditions in Ayiba, northern Ethiopia. Relevant agronomic data were evaluated and recorded from plots of each soil types for analysis. The analysis of variance revealed a significant (p < 0.001) variation on all the agronomic and grain quality traits due to the main and interaction effects of soil type and fertilizer treatment factors. Most agronomic and quality characteristics recorded the highest result in the highest treatment applications (175 and 150 kg NPSZnB ha-1) in both soils. Yield and grain quality traits of bread wheat was also found better under fertilized plots than unfertilized plots. In both soil types increasing application of the new blended fertilizer rate from 50-175 kg NPSZnB ha-1 showed an increasing trend in grain yield from 1.6 to 4.3 and 2.5 to 5.4 t ha-1 in Vertisol and Cambisol soils, respectively. The varied yield as a response of fertilizer treatments across soils signifies soil-specific fertilization approach is critically important for production increment. On the other hand, based on the partial budget analysis the highest net benefit with the highest marginal rate of return in both Vertisol and Cambisol soils were obtained when treated with 100 and 125 kg NPSZnB ha-1, respectively. Therefore, to produce optimum bread wheat yield under rainfed conditions in Ayiba (northern Ethiopia) fertilizing Vertisols with 100 kg NPSZnB ha-1 and fertilizing Cambisols with 125 kg NPSZnB ha-1 is recommended.

Establishment and validation of site specific fertilizer recommendation for increased barley (Hordeum spp.) yield, northern Ethiopia.

Establishing model based balanced nutrient requirements for barley (Hordeum spp.) in the northern Ethiopia can solve the fertilizer recommendation problems and enhance crop yield. The Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model was used to estimate balanced nitrogen (N), phosphorus (P) and potassium (K) requirements for barley production in Alaje, northern Ethiopia. The objectives were to (i) quantify soil N, P and K supply and recommend fertilizers using QUEFTS model; (ii) investigate response of QUEFTS fertilizer application on yield and nutrient uptake and (iii) validate QUEFTS model performance. The experiment had four treatments: (T1) model based fertilization; (T2) blended fertilization; (T3) farmers' fertilization practices and (T4) control/no fertilizer. Soil information of the experimental plots were analyzed and used as model input to estimate soil nutrient supplies and recommend fertilizer. Yield and agronomic data were recorded and nutrient uptake and use efficiencies were analyzed. Model performance and accuracy were also checked using root mean square error, coefficient of determination, index of agreement and percent bias. The result revealed that the N, P and K soil supply ratio in the field experimental plots were 9:1:6. The higher grain yield of 4747 kg ha-1 was recorded in the QUEFTS based fertilization plots. Validation results indicated that there is a good correlation between the QUEFTS predicted and observed grain yields implying that the QUEFTS model can be a base for development of simple and cost-effective decision support tools for nutrient management and fertilizer recommendations. Thus, the model performance and prediction accuracy is promising and can help farmers to adjust fertilizer application rates based on crop requirements.

Impact of land use type and altitudinal gradient on topsoil organic carbon and nitrogen stocks in the semi-arid watershed of northern Ethiopia.

Understanding the role of soils in the soil organic carbon (SOC) and total nitrogen (TN) cycle is essential, assumed that these parameters are among the key soil quality indicators in a given landscape. Nothing but their status is in a state of continual flux due to land-use, soil management practices, and nature of topographic features. Thus, this study has evaluated the effect of land-use types and altitudinal gradient on SOC and TN concentrations and stocks at a watershed scale in northern Ethiopia. A total of 450 topsoil samples (0-30 cm depth) were collected from four different land-use types (Fig.3) across three elevational categories (Fig.1(b)), and their SOC and TN distributions were studied using descriptive statistics and geostatistical methods. Results revealed significant (p < 0.05) differences in SOC and TN concentrations and stocks by land-use type, elevation, and their interactions. The highest SOC stock was recorded at the lower elevation in GL (7.24 Mg C ha-1), followed by PF (4.65 Mg C ha-1) in the middle and GL (4.61 Mg C ha-1) in the upper elevations, respectively. On the other hand, the lowest SOC stock was observed in the BL areas of the upper (2.34 Mg C ha-1) and middle (2.75 Mg C ha-1) elevations. Spatially, the mean SOC stocks of the different land-uses were in the following order: GL > PF > CL > BL in upper elevation, PF > GL > CL > BL in middle elevation, and GL˃CL in lower elevation, respectively. The estimated total SOC and TN stocks of the study watershed were about 46,868.66 ± 7747.38 Mg C and 7,008.02 ± 441.25 Mg N, respectively. The notable difference is attributable to lack of vegetation cover, unsustainable land-use system, and land degradation via water erosion. Hence, these physical landscape disturbances result in disruption of SOC and TN's storage and stability. The SOC and TN stocks have shown a significant (p < 0.05) negative correlation with soil bulk density in the study watershed. The study concludes that variations in the land-use along topographic gradients drive the soils' SOC and TN storage. Therefore, land suitability planning, soil and water conservation measures, and reforestation practices are needed and practical worth increasing SOC and TN storage in the watershed.

Potential, quality and quantity assessment of sesame plant residue in dry land vertisols of Tigrai, Ethiopia; Approach for sustainability of dry-land farming.

In dryland areas, the increasing demand for sustainable production needs to effectively utilize and manage residue. The aim of this study was to evaluate the potential, quality, and quantity assessment of sesame residue in dryland areas. Quantification of residue potential was performed at <650, 650-850, 850-1050, and >1050 m elevation by summing the weight of stack, standing residue, and straw. Whereas, assessment in the residues nutrient content was performed at <650, 650-850, 850-1050, and >1050 m elevation and age of residue (fresh and old). The TN, S and P in the residue were determined by Kjeldahl digestion Method, wet acid digestion Method, and two percent acetic acid (CH3COOH) as extracting to extract PO4 respectively. Atomic absorption spectrophotometer was used to determine micronutrient cations such as Fe, Zn, and Cu. B was determined by extraction using a mixture of hydrochloric (HCl) and hydrofluoric (HF) acids to plant tissue digests. The nutrient potential was calculated by multiplying nutrient content in residue with the amount of residue estimated ha-1. R software (R version 3.5.2) was used to analyze the data. The result indicates that during the last 20 years, the total cultivated land size covered by sesame was 170,000 (ha) and total grain yield of 0.09 Mt. This implies that the size of cultivated land put under sesame cultivation has increased by 79.5%. On average 2.01 t ha- 1 of residue was produced annually and about 0.34 Mt yr-1 of residue was harvested from sesame production. The age of residue differed significantly (p < 0.05) on TN, S, P, Zn, Fe, Cu, and B content of sesame residue. Nutrient content in residue was ranged from 34.55-24.53 g TN/kg, 9.6-4.2 g S/kg, 5.2-4.3 g P/kg, 23-14.6 mg Zn/kg, 130.23-94.78 mg Fe/kg, 17-6.2 mg Cu/kg and 10.67-9.12 mg B/kg during fresh and old residue analysis respectively. Elevation differed significantly (p < 0.05) for TN, S, P, Zn, and Fe. Nutrient content in residue was ranged from 27.1-32.2 g TN/kg, 6-8.5 g S/kg, 6.6-4.1 g P/kg, 20.8-17 mg Zn/kg, 109-116 mg Fe/kg, 12.9-10.4 mg Cu/kg and 10.1-9.6 mg B/kg for the elevation range of <650 m and >1050 m respectively. The TN, S, P, Zn, Fe, Cu, and B potentially produced from sesame residue were in the range of 49.4-69.6 kg N ha-1, 8.5-19.3 kg S ha-1, 8.7-10.5 kg P ha-1, 294-463 mg Zn ha-1, 1.99-2.62 g Fe ha-1, 125-342 mg Cu ha-1 and 183-214 mg B ha-1 respectively. This study clearly concludes that fresh and old residue as well as elevation are critical factors that need to be considered for exploring crop residue and its nutrient potential, quality, and quantity aspects in dryland farming systems.