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Open AccessArticle

Optimising Nutrient Cycles to Improve Food Security in Smallholder Farming Families—A Case Study from Banana-Coffee-Based Farming in the Kagera Region, NW Tanzania

1
United Nations University Institute for Integrated Management of Material Fluxes and of Resources (UNU-FLORES), Ammonstraße 74, 01067 Dresden, Germany
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Institute of Waste Management and Circular Economy, Technische Universität Dresden, Pratzschwitzer Str. 15, 01796 Pirna, Germany
3
Institute of Soil Science and Site Ecology, Technische Universität Dresden, Pienner Str. 19, 01735 Tharandt, Germany
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Thünen Institute of Forest Ecosystems, Alfred-Möller Str. 1, 16225 Eberswalde, Germany
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National Land Use Planning Commission, 1147 Kivukoni Front, 1 Ardhi Street, P.O. Box 76550 Dar es Salaam, Tanzania
*
Author to whom correspondence should be addressed.
Sustainability 2020, 12(21), 9105; https://doi.org/10.3390/su12219105
Received: 1 May 2020 / Revised: 7 September 2020 / Accepted: 15 September 2020 / Published: 2 November 2020
(This article belongs to the Special Issue Transitioning to a Circular Economy with Sustainable Waste Management)
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 about 750 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 t yr−1 of the herbaceous legume species Crotalaria grahamiana into the soil; S3: the production of 5 m3 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 an in-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. View Full-Text
Keywords: sustainable land management; soil fertility management; farm waste management; agroforestry; nutrient balances; human urine; legume; biochar; CaSa-compost; food security sustainable land management; soil fertility management; farm waste management; agroforestry; nutrient balances; human urine; legume; biochar; CaSa-compost; food security
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  • Externally hosted supplementary file 1
    Doi: 10.1594/PANGAEA.914713
    Link: https://doi.pangaea.de/10.1594/PANGAEA.914713
    Description: Reetsch, Anika; Schwärzel, Kai; Kapp, Gerald; Dornack, Christina; Masisi, Juma; Alichard, Leinalida; Robert, Harriet; Byamungu, Godson; Stephene, Shadrack; Feger, Karl-Heinz (2020): Survey of 150 smallholder farm households in banana-coffee-based farming systems containing data on farm households, agricultural production and use of farm waste. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.914713 (dataset in review)
MDPI and ACS Style

Reetsch, A.; Schwärzel, K.; Dornack, C.; Stephene, S.; Feger, K.-H. Optimising Nutrient Cycles to Improve Food Security in Smallholder Farming Families—A Case Study from Banana-Coffee-Based Farming in the Kagera Region, NW Tanzania. Sustainability 2020, 12, 9105. https://doi.org/10.3390/su12219105

AMA Style

Reetsch A, Schwärzel K, Dornack C, Stephene S, Feger K-H. Optimising Nutrient Cycles to Improve Food Security in Smallholder Farming Families—A Case Study from Banana-Coffee-Based Farming in the Kagera Region, NW Tanzania. Sustainability. 2020; 12(21):9105. https://doi.org/10.3390/su12219105

Chicago/Turabian Style

Reetsch, Anika; Schwärzel, Kai; Dornack, Christina; Stephene, Shadrack; Feger, Karl-Heinz. 2020. "Optimising Nutrient Cycles to Improve Food Security in Smallholder Farming Families—A Case Study from Banana-Coffee-Based Farming in the Kagera Region, NW Tanzania" Sustainability 12, no. 21: 9105. https://doi.org/10.3390/su12219105

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