Suchergebnisse

When assessing soil organic carbon (SOC) sequestration and its climate change (CC) mitigation potential at global scale, the dynamic nature of soil carbon storage and interventions to foster it should be taken into account. Firstly, adoption of SOC-sequestration measures will take time, and reasonably such schemes could only be implemented gradually at large-scale. Secondly, if soils are managed as carbon sinks, then SOC will increase only over a limited time, up to the point when a new SOC equilibrium is reached. This paper combines these two processes and predicts potential SOC sequestration dynamics in agricultural land at global scale and the corresponding CC mitigation potential. Assuming that global governments would agree on a worldwide effort to gradually change land use practices towards turning agricultural soils into carbon sinks starting 2014, the projected 87-year (2014–2100) global SOC sequestration potential of agricultural land ranged between 31 and 64 Gt. This is equal to 1.9–3.9% of the SRES-A2 projected 87-year anthropogenic emissions. SOC sequestration would peak 2032–33, at that time reaching 4.3–8.9% of the projected annual SRES-A2 emission. About 30 years later the sequestration rate would have reduced by half. Thus, SOC sequestration is not a C wedge that could contribute increasingly to mitigating CC. Rather, the mitigation potential is limited, contributing very little to solving the climate problem of the coming decades. However, we deliberately did not elaborate on the importance of maintaining or increasing SOC for sustaining soil health, agro-ecosystem functioning and productivity; an issue of global significance that deserves proper consideration irrespectively of any potential additional sequestration of SOC.

The premise of this paper is that the key to effective water resources management is understanding that the water cycle and land management are inextricably linked: that every land use decision is a water use decision. Gains in agricultural water productivity, therefore, will only be obtained alongside improvements in land use management. Expected increases in food demands by 2050 insist that agricultural production - and agricultural water use - must increase. At the same time, competition for water between agricultural and urban sectors will also increase; and the problem is further compounded by land degradation. A global survey suggests that 40% of agricultural land is already degraded to the point that yields are greatly reduced, and a further 9% is degraded to the point that it cannot be reclaimed for productive use by farm level measures. Soil erosion, nutrient depletion and other forms of land degradation reduce water productivity and affect water availability, quality, and storage. Reversing these trends entails tackling the underlying social, economic, political and institutional drivers of unsustainable land use. This paper is based on a review of global experiences, and its recommendations for improving water management by addressing land degradation include focusing on small scale agriculture; investing in rehabilitating degraded land to increase water productivity; and enhancing the multifunctionality of agricultural landscapes. These options can improve water management and water productivity, while also improving the livelihoods of the rural poor.

Agriculture is the most significant contributor to Ethiopia?s economy. Most of the agricultural production is under rainfed conditions and thus extremely sensitive to rainfall variability. Irrigation development, including smallholder irrigation, is used by the Ethiopian Government to attempt to mitigate the effects of rainfall variability. In this study, we look at smallholder irrigation - modern and traditional irrigation systems. A detailed description of the cropping patterns is given. The stochastic frontier production function approach is used to estimate technical inefficiency, and constraints to production are analyzed. Since the traditional system is found to be efficient but on a lower production frontier, the study shows that significant gains can be made by raising the frontier of the traditional systems and increasing the efficiency of the modern systems. Among the production constraints studied were land preparation, soil fertility, weed control, pests and diseases, soil erosion, input access and moisture deficiency. The most significant constraints on the irrigated systems were input access and moisture deficiency.