Soil Properties, and Soil Organic Carbon Stocks of Tropical Andosol under Different Land Uses

Land use effect of tropical Andosol, with two from crop lands (Site 1 and Site 2) and one from Agroforestry coffee plantation (Site 3) was explored under laboratory conditions to understand their physical, chemical and biological properties and soil organic carbon (SOC) stocks from the rift valley of Ethiopia. Site 3 that acquired less cultivation than others exhibited better aggregate size fraction (AF, 55%), higher aggregate stability (AS, 91%), and greater active microbial biomass (AMB), reflecting better soil structure development. Comparatively, higher total carbon (TC), organic carbon (OC) and total nitrogen (TN) concentrations were recorded in bulk soils and microaggregate fractions of Site 2 and Site 3 than in intensively cultivated Site 1. As expected, microaggregate fractions displayed greater OC and TN than bulk soils across all land uses. Site 1 revealed higher metabolic quotient (qCO2) and lower SOC stock (2.1 Mg·ha-1), suggesting microbial stress, while micro nutrients deficiencies were observed with the alkaline soil (Site 2). Conversely, the highest SOC stock was exhibited with Site 3 (4.2 Mg·ha-1), indicating the importance of coffee land use in C sequestration. Crop lands, depleted much of their native carbon stocks had significant CO2 sink capacity. Hence, management practices that increase the input of organic resources should be adopted to build SOM and enhance soil fertility.

Response of Tef (<i>Eragrostis tef</i>(Zucc.) Trotter) to Balanced Fertilizer in Wolaita Zone, Southern Ethiopia

Tef is grown as an important domestic cereal in Ethiopia. Currently, global attention is given for it particularly as a “health food” due to the absence of gluten and gluten like proteins in its grains. Regardless of its wider adaptation, productivity of tef is low in the country with the national average grain yield of 1.379 tons·ha-1. This is mainly because of low soil fertility and severe organic matter depletion intensified by low rate of chemical fertilizer application. This study was conducted to evaluate effects of balanced fertilizers on the yield, yield components of tef and to determine economic feasibility for tef production in Wolaita. The experiment was laid out in a randomized complete block design (RCBD) with sixteen treatments replicated three times. The treatments consist of factorial combinations of four rates of K (Potassium) (0, 25, 50, and 100 kg/ha) and four rates of NPSB (Nitrogen, Phosphorus, Sulfur and Boron) (0, 50, 100, 200 kg/ha) fertilizers. Fertilizer types such as urea (46-0-0), NPSB (18.9-37.7-6.95-0.1) and K (0-0-60) were used as a source of nutrients. The soil analysis result indicated that, most of the nutrients are below optimum level to support the potential crop production. This may be related with reduced farm management practices and continuous cropping with little or no fertilizers input. In this study, it was found that, the combined application of NPSB and K fertilizers had a significant effect on growth, yield and yield components of tef. Among the treatments studied, NPSB (100 Kg/ha) and K (50 Kg/ha) gave greater grain yield. Furthermore, this treatment enhanced growth and yield related parameters compared to the control treatment. Thus, it is conceivable to recommend each to attain greater grain yield of tef in the study area. However, it is desirable to undertake further research across soil type, years and locations to appeal comprehensive recommendation on a wider scale.

Impacts of fire suppression on above‐ground carbon stock and soil properties in Borana rangelands,southern Ethiopia

Background:Fire is a natural disturbance that releases carbon back into the atmosphere.Pastoralists have used fire for many thousands of years for rangeland management.The use of fire in the Borana rangelands of southern Ethiopia was a common practice to improve the productivity of the rangelands.However,the use of fire as a tool to manage rangeland was prohibited by government policy in the early 1970s.Methods:In this study,we assessed the long‐term impacts of fire suppression on aboveground carbon stocks of woody and herbaceous biomass,soil organic carbon stocks,and total nitrogen stocks at burned versus adjacent unburned areas in the Borana rangelands of southern Ethiopia.The investigation was conducted in two locations:Dikale and Sanke.The upland location was represented by Dikale,while the bottomland location was represented by Sanke.Each study site was replicated three times,with burned versus adjacent unburned areas representing each replicate.Soil samples were collected in three soil depths(0–5,5–15,and 15–30 cm),while vegetation attributes were collected from 60 plots within three burned and three adjacent unburned sites in each landscape.Results:The soil organic carbon stock and pooled carbon stock between burned and unburned sites across the two landscapes showed minimal variation.The above‐ground carbon biomass accumulation for woody and herbaceous plants did not show any significant difference between burned and unburned sites both at the bottomland and upland areas.The total nitrogen contents recorded at uplands in burned sites were significantly(p<0.05)higher than the total nitrogen stocks for the unburned adjacent sites.Conclusions:Burned areas accumulated relatively more carbon stocks in terms of herbaceous biomass(3.27±0.43 Mg ha^(−1))than the adjacent unburned areas(0.98±0.43 Mg ha^(−1)).The results of the current study suggest that burning improved the carbon sequestration potential of herbaceous plants in arid savanna ecosystems.