Suchergebnisse

Böden sind in Raum und Zeit variable Naturkörper. Sie erfüllen zahlreiche Funktionen im Naturhaushalt und für den Menschen. Durch Flächeninanspruchnahme und andere vielfältige Einwirkungen sind Böden in sehr unterschiedlicher Weise beansprucht und gefährdet. Dies erfordert eine nachhaltige Bewirtschaftung und einen adäquaten Schutz.

In East Africa, soil nutrient depletion and low yields jeopardise the food security of smallholder farming families and exacerbate poverty. The main reasons for the depletion of soil nutrients are overuse due to population growth, limited land, and increasing uncertainty in agricultural production caused by climate change. This study aims to analyse and optimise nutrient flows and stocks in the homegardens of smallholder banana-coffee-based farming systems in the Kagera region in NW Tanzania.The plant nutrients nitrogen (N), phosphorus (P), and potassium (K) in plant-based biomass and organic farm waste are under investigation. We used data from a farm household survey (150 households) and from focus group discussions with 22 trainers who had been training about750 farm households in sustainable land management (SLM) at a local farmer field school. In total, we identified six farm household types and calculated a nutrient balance (NB) for the homegardens of each household type. The NB was calculated for the following five management scenarios: S0: business as usual; S1: the use of 80% of the available human urine; S2: the incorporation of 0.5 tyr−1 of the herbaceous legume species Crotalaria grahamiana into the soil; S3: the production of 5m3 yr−1 CaSa-compost (human excreta and biochar) and its application on 600 m2 land; and S4: a combination of S1, S2, and S3. The results show that the NB varies considerably depending on whether farmers have implemented the SLM training, apply nutrient-preserving manure collection and storage methods, and purchase fodder (imported nutrients), or whether they do not collect manure or do not purchase fodder. Trained farm households are more likely to have a positive NB than untrained households because they have already improved the nutrient management of their farms through the successful implementation of SLM practices. Untrained households would improve the NB in their homegardens under all management scenarios. However, the NB depends on labour-intensive manure collection and compost production, labour shortages, prolonged dry seasons, and socio-economic imbalances. As long as these constraints remain, nutrient deficiencies will not be overcome with mineral fertilisers alone, because soils have to be further enriched with organic matter first. In this paper, we also emphasise the importance of the system boundary, because only a complete NB can give an estimate of actual nutrient removal and the resulting nutrient demand (including removals by fodder and trees). Further improvements in the SLM training may be achieved by (i) measuring the current nutrient status of soils, (ii) analysing the need for the coexistence of free-range livestock on the grassland and zero-grazing in trained households, and (iii) conducting anin-depth analysis of the socio-economic differences between successful and unsuccessful households. In conclusion, if smallholder farmers were to integrate further improved SLM training and optimised nutrient management (S1 to S4), we assume that the NB would turn positive. Last but not least, the SLM training by the farmer field school may serve as a best-practice example for training and policy recommendations made by government institutions.

This study examines how smallholder farmers operate degraded banana-coffee-based farming systems and apply organic farm waste. We surveyed 150 farm households in two districts of the Kagera region in north-west Tanzania (Karagwe and Kyerwa districts). An expert-based typology revealed three groups of farm households that differ in biomass production (high, moderate, low). Households producing high amounts of biomass have integrated a sophisticated farm waste management system, but do not exploit the full potential of organic farm waste as a soil fertiliser and conditioner. The integration of farm waste management decreases in farm house-holds with medium and low biomass production. None of the households is food secure, as they experience seasonality in food production and lack food storage technologies. In farm households with high and medium biomass production, the optimised use of organic farm waste could potentially lead to food security if food storage capacities were also improved. However, farm households with low biomass production will not become food secure with the introduction of organic farm waste management alone, as the land size is too small, and the socio-economic basis for it is lacking. Limited labour remains a major restriction to improving farm waste management. In the future, the safe use of human excreta needs to be fostered in engineering and research, holistic material flow analyses integrating (low-tech) agricultural solutions and concepts investigated, e.g., biochar production, safe use of mineral fertiliser and climate-smart agriculture, and the socio-economic status of female-headed households strengthened, e.g., in farmer field schools and governmental programmes.