Potential for soil organic carbon sequestration in grasslands in East African countries: A review

Grasslands occupy almost half of the world's land area. Soil organic carbon (SOC) is a key indicator of soil fertility and grassland productivity. Increasing SOC stocks (so‐called SOC sequestration) improves soil fertility and contributes to climate change mitigation by binding atmospheric carbon dioxide (CO2). Grasslands constitute about 70% of all agricultural land, but their potential for SOC sequestration is largely unknown. This review paper quantitatively summarizes observation‐based studies on the SOC sequestration potential of grasslands in six East African countries (Burundi, Ethiopia, Kenya, Rwanda, Tanzania and Uganda) and seeks to identify knowledge gaps related to SOC sequestration potential in the region. In the studies reviewed, SOC stocks in grasslands range from 3 to 93 Mg C/ha in the upper 0.3 m of the soil profile, while SOC sequestration rate ranges from 0.1 to 3.1 Mg C ha‐1 year‐1 under different management strategies. Grazing management is reported to have a considerable impact on SOC sequestration rates, and grassland regeneration and protection are recommended as options to stimulate SOC sequestration. However, a very limited number of relevant studies are available (n = 23) and there is a need for fundamental information on SOC sequestration potential in the region. The effectiveness of potential incentive mechanisms, such as payments for environmental services, to foster uptake of SOC‐enhancing practices should also be assessed

Sensor Data Fusion for Topsoil Clay Mapping of an Agricultural Field

Abstract Data from proximal sensors for gamma (γ) radiation and apparent electrical conductivity (ECa) was combined with elevation, radiance and drainage data. Predictions of clay content were made with different combinations of predictor variables. Predictions from ECa were improved by using multitemporal measurements or multiple measurements with different depth responses. They were also improved by addition of radiance data. Predictions from γ radiation were found to be accurate and was not much improved by adding ECa or any other ancillary data. Predictions by a k Nearest Neighbor algorithm were somewhat better than predictions by Partial Least Squares regression

Impact of elevated O3, and CO2 exposure on potato (Solanum tuberosum L. cv. Bintje) tuber macronutrients (N, P, K, Mg, Ca)

v2007okMAAMYKMP

The grain quality of spring wheat (Triticum aestivum L.) in relation to elevated ozone uptake and carbon dioxide exposure

vokMY

The importance of soil fertility constraints in modeling crop suitability under progressive climate change in Tanzania

AbstractSpatial crop suitability models are important planning tools for agricultural development, especially regarding climate change adaptation. The original version of the EcoCrop model predicts crop suitability based on monthly temperature and precipitation, without taking into account soil constraints. Recently, continuous soil property maps of Tanzania were produced (Vagen et al, submitted) based on data from systematic surveys across sub-Saharan Africa. The aim of the present study was to assess the effects of incorporating information on soil fertility constraints, such as low soil organic carbon content (SOC) into the EcoCrop model. Crop suitability maps derived with and without consideration of low SOC were compared. SOC values were extracted for 1036 locations of common bean (Phaseolus vulgaris L.) presence and the 2-percentile (0.9% SOC) was taken as a lower limit for suitability. The EcoCrop model was then run with current climate data, with and without SOC as a limiting factor, to create suitability maps. An independent spatial point dataset of registered bean presence/absence (n=1113), and regional production statistics were used for validation. The agreement between bean presence and bean suitability was higher (Cohen's unweighted kappa=0.06) when low SOC was included in the model compared to when only climate was considered (kappa=0.02). The regional statistics showed that the proportion of the area where low SOC restricted the suitability was negatively correlated with the proportion of the area planted with beans (r =-0.42, p=0.07). In summary, we identified a lower limit of SOC for the soil to be suitable for common beans production and investigated the importance of taking this soil fertility constraint into account for accurate suitability modelling. It was concluded that for more accurate suitability modelling, e.g. for decision support for adaptation to climate change, low SOC should be considered as a constraining factor

Development of a Soil Organic Carbon Baseline for Otjozondjupa, Namibia

Land Degradation Neutrality (LDN) has been piloted in 14 countries and will be scaled up to over 120 countries. As a LDN pilot country, Namibia developed sub-national LDN baselines in Otjozondjupa Region. In addition to the three LDN indicators (soil organic carbon, land productivity and land cover change), Namibia also regards bush encroachment as an important form of land degradation. We collected 219 soil profiles and used Random Forest modelling to develop the soil organic carbon stock baseline. Values range between 0.53 and 4.27 kg/m2 in the sandy Otjozondjupa soils. LDN baselines were integrated into other national planning processes to add value to LDN products. Analyses of the relationship between soil carbon and land cover change, especially from grassland to bushland, increased the usefulness of soil carbon maps for the Integrated Regional Land Use Planning process. Local ownership of LDN baseline development, from data collection to digital soil mapping, was crucial for local stakeholders