Policy brief Botswana's agriculture and water resources May 2015

This is the fourth policy brief in a series, which is based on the results of Botswana’s recent water accounting efforts carried out by Department of Water Affairs (DWA) and Centre for Applied research (CAR). Earlier policy briefs dealt with ‘scarcity of water resources’ (2013), ‘water and the mining sector’ (2014) and ‘water and irrigation’ (2014). This policy brief on agriculture covers both the livestock and irrigation sectors. Dryland crop production is not covered as it does not abstract water from the environment for the economy

Long-term Impact of sewage sludge application on rhizobium leguminosarum biovar trifolii: an evaluation using meta-analysis

The Long-Term Sludge Experiment (LTSE) began in 1994 at nine UK field sites as part of continuing research into the effects of sludge-borne heavy metals on soil fertility. The long-term effects of Zn, Cu, and Cd on the most probable numbers of cells (MPN) of Rhizobium leguminosarum biovar trifolii were monitored for 8 yr in sludge-amended soils. To assess the statutory limits set by the UK Sludge (Use in Agriculture) Regulations, the experimental data were reviewed using statistical methods of meta-analysis. Previous LTSE studies have focused predominantly on statistical significance rather than effect size, whereas meta-analysis focuses on the magnitude and direction of an effect, i.e., the practical significance rather than its statistical significance. Results showed Zn to be the most toxic element causing an overall significant decrease in Rhizobium MPN of −26.6% during the LTSE. The effect of Cu showed no significant effect on Rhizobium MPN at concentrations below the UK limits, although a −5% decrease in Rhizobium MPN was observed in soils where total Cu ranged from 100 to <135 mg kg−1. Overall, there was nothing to indicate that Cd had a significant effect on Rhizobium MPN below the current UK statutory limit. In summary, the UK statutory limit for Zn appears to be insufficient for protecting Rhizobium from Zn toxicity effects

Waste to energy in the UK: policy and institutional issues

A sustainable waste management policy is necessary to manage the growing stream of municipal solid waste in ecologically sustainable ways. Although landfill has been the dominant form of waste management in the UK there is a need to comply with the European Union landfill directive. Waste to energy (WtE) is a viable waste management option to reduce the reliance on landfills and reap the energy benefits of waste. The first waste-fired power plant was built in the UK in 1885 but several barriers have constrained the use of WtE. This paper assesses the policy and institutional context for the development of WtE in the UK. It discusses how public opinion and choice of technology are important factors in achieving a wider acceptance of WtE in the UK. There is a need to devise coordinated policies on sustainable waste management at the regional and local levels. Furthermore, making all WtE technologies eligible for renewable obligation certificates could support the development of the technology and divert waste from landfills. The absence of efficient heat delivery networks is also a barrier to fulfilling the potential for WtE in the UK

Scenario-based sustainable water management and urban regeneration

Copyright © ICE PublishingDeployable output (source availability) from water resources in north west England is predicted to decrease over the next 25 years. Alternative supply management strategies are planned to help avoid a deficit in the supply–demand balance within the region but have yet to be considered in detail. This paper assesses the contribution of such an alternative supply strategy at local level on the water resource supply–demand balance at regional level based on a proposed urban regeneration site in north west England. Various water conservation and reuse measures are investigated considering local and regional conditions and constraints. Four future scenarios are presented and used to describe how the future might be (rather than how it will be), to allow an assessment to be made of how current ‘sustainable solutions’ might cope whatever the future holds. The analysis determines the solution contributions under each future and indicates that some strategies will deliver their full intended benefits under scenarios least expected but most needed. It is recommended that to help reduce the regional supply–demand deficit and maximise system resilience to future change, a wide range of water demand management measures should be incorporated on this and other sites

Environmental benefits of improved water and nitrogen management in irrigated sugar cane : a combined crop modelling and life cycle assessment approach

The application of irrigation water and nitrogen (N) fertilizer in excess of crop demand reduces profitability and has multiple detrimental impacts on the environment. N dynamics in agroecosystems are extremely complex, and mechanistic crop models are most often required to quantify the impact of improved management practices on reducing fertilizer N losses. In this study, Life Cycle Assessment (LCA) methodology and mechanistic modelling was used to quantify the environmental benefits of improved management of water and fertilizer N by sugarcane farmers in a case study in Pongola, South Africa. A baseline scenario, representing farmer intuition-based irrigation scheduling management, and two additional scenarios in which water, and water and N were more rationally managed, were compared. Results show that improved water and N management can lead to a 20% reduction in non-renewable energy consumption per functional unit (FU), with sustained or even increased yields. Total GHG emissions can potentially be reduced by 25% through more efficient water and N management. Limiting the rates of fertilizer N applied, made possible by decreasing N leaching through improved irrigation scheduling, resulted in the highest reductions for both impact categories. While total water consumption was very similar between the scenarios, more efficient use of rainfall was achieved through accurate scheduling, reducing blue water requirements. Through the simultaneous consideration of multiple environmental impacts, combining mechanistic crop modelling and LCA shows potential to identify improved management practices as well as to establish environmental stewardship incentives.L'application d'eau d'irrigation et d'engrais azotés (N) en excès par rapport à la demande des cultures réduit la profitabilité et a de multiples impacts négatifs sur l'environnement. La dynamique de l'azote dans les agrosystèmes est extrèmement complexe, et des modèles de culture mécanistes sont souvent nécessaires pour quantifier l'impact de pratiques de gestion améliorées sur la réduction des pertes en azote. Cette étude utilise la méthodologie de l'Analyse du Cycle de Vie (ACV) combinée à la modélisation mécaniste pour quantifier les bénéfices environnementaux d'une gestion améliorée de l'eau et des fertilisants azotés par des producteurs de canne à sucre, dans une étude de cas à Pongola, Afrique du Sud. Un scénario de base représente les pratiques courantes et intuitives des producteurs en termes d'irrigation, et deux scénarios supplémentaires représentent des pratiques de gestion plus rationnelles de l'eau, et de l'eau et des engrais, respectivement. Les résultats montrent qu'une meilleure gestion de l'eau et de l'azote peut générer une réduction de 20% de la consommation en énergie non-renouvelable, avec des rendements maintenus voire améliorés. Les émissions totales de GES peuvent potentiellement être réduites de 25%. La réduction des applications d'engrais, rendue possible par le moindre lessivage de l'azote sous irrigation raisonnée, résulte en de fortes réductions de ces deux catégories d'impacts. La consommation totale en eau est similaire entre scénario de base et scénarios de meilleure gestion de l'eau; cependant l'utilisation de l'eau de pluie est plus efficiente avec les irrigations raisonnées, réduisant ainsi les besoins d'extraction de la ressource. Par la prise en compte simultanée d'impacts environnementaux multiples, la combinaison de l'ACV et de la modélisation mécaniste de culture montre un potentiel pour identifier les pratiques améliorées et pour développer un accompagnement en éco-conception de systèmes.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1531-03612016-04-30hb201