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Over the past decades, the number of certified organic farms have increased significantly in Uganda. One assumption is that certified organic agriculture contributes to economic, social and ecological health of agroecosystems. In the literature, however, there is thin empirical evidence to support such claims. We therefore developed health indicators and contrasted data from four Ugandan farming systems with principles and objectives of organic agriculture. We identified four health patterns (ecology-driven, economically struggling, socially-driven, and hanging in) demonstrating the impact of farm management on agroecosystem health and trade-offs between health domains. Ecological farm health is strengthened only if the conversion goes beyond 'organic by default'. Marketoriented specialization can create lock-in situations if production strategies cannot be changed easily. Food shortages occur when additional income from certified production does not compensate for the reduced area and effort devoted to food crops. We conclude that the positive effects of organic certification on agroecosystem health cannot be taken for granted. Interventions promoting organic agriculture should acknowledge risks smallholder farmers take by converting to cash crop-oriented certified organic farming. A challenging question will be how aspects of wellbeing and social health can be translated into certification standards and thus product attributes.

Abstract:The effect of soil and water conservation (SWC) practices on controlling surface runoff and soil loss was studied in drought prone banana growing areas of Uganda, during the two major rainy seasons of 2014. The study was conducted at two sitesNtungamo (Southwest) and Sembabule (Central), with comparable slopes of about 13%-25%. The treatments included mulch, manure, manure + mulch and a control with no conservation. Results indicated that conservation practices of mulch and manure + mulch significantly reduced surface runoff and soil loss by about 72%-85%, when compared to farmers' up-and-down cultivation practice (control). It was also observed that significantly greater amounts of soil loss occurred from manure and control plots than the ones with mulch. Thus, the combination of manure and mulch is recommended for uptake by crop farmers in the study areas, if they are to overcome drought stress and adapt to changes in climate. More research is needed to quantify nutrient losses resulting from runoff under the different SWC techniques. Modeling such effects is essential in assessing the impacts of SWC practices on soil and crop productivity.

Despite the global interest to increase the world's carbon stocks, most carbon sequestration strategies have largely depended on woody ecosystems whose production is threatened by the continuous shortage of land, hence the need to explore viable alternatives. The potential of bananas to sequester carbon has been reported but there is limited knowledge on the performance of various cultivars as specific carbon stocks are often lost in global assessments. Therefore, this study aimed at exploring the potential of and variability in carbon stocks of selected East African Highland Banana (EAHB) cultivars. Plant and soil data were collected using destructive and non-destructive techniques in 30×30m 2 sampling plots for 4 cultivars Kibuzi, Nakitembe, Enyeru and Nakinyika growing in two agroecological zones of Uganda being the L.Victoria Crescent and the South-western region. Total carbon and Soil Organic Carbon (SOC) stocks did not differ considerably across cultivars (P>0.05). However, there was significant variation (P<0.05) in plant carbon stock being lowest in two cultivars: Nakinyika at 0.37±0. . The SOC stock variation difference across depth was 2.9-8.5 Mgha -1 being higher in top soil than sub-soil. Despite the small plant carbon stock amounts, the system enables much more carbon to be stored in the soil considering the proportion of what is contained in the plant to that in the soil across all cultivars (0.4-2%). The study therefore recommends revision of existing carbon frameworks to incorporate the contribution of non-woody perennials like bananas in the carbon cycle so that the poor small scale farmers who cannot afford large acreages to establish tree plantations can also benefit from such initiatives.

Globally, interests to increase carbon stocks have gained momentum in both woody and non-woody ecosystems. Despite efforts made to generate appropriate methods to estimate these stocks, most equations developed do not cater for intraspecific variabilities across e.g. species, regions or growth stages; especially in the case of bananas. Therefore, there is need to develop more robust equations to improve on the precision of biomass-carbon prediction especially at local scales to facilitate estimation of specific carbon stocks often lost in global assessments. This study aimed at developing cultivarspecific biomass estimation relationships and determining carbon content of EAHB cultivars at two growth stages. Plant data were collected purposively using destructive sampling techniques on farmers' plots for 4 cultivars (Kibuzi, Nakitembe, Enyeru and Nakinyika) in two agro-ecological zones: the L. Victoria crescent and the South-western farmlands in the districts of Lwengo and Mbarara respectively. Results show that biomass differed across cultivars (P<0.001); hence four equations (Enyeru, Nakinyika, Kibuzi_Nakitembe and Generic) were developed following an exponential function, y=Aexp(ax), using diameter at breast height (DBH) as the predictor variable with an R 2 range of 82-94%. EAHB mean carbon content varied significantly with growth stage (P<0.05) (47.6% for maiden plants before flowering and 48.8% for mature plants with a developed bunch). This study concludes that it is important to develop cultivar-specific equations for biomass-carbon estimation of EAHB cultivars to help assess their contribution to the carbon cycle especially in future studies.