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Agriculture 2018, 8(3), 31; https://doi.org/10.3390/agriculture8030031

Recycling Improves Soil Fertility Management in Smallholdings in Tanzania

1
Postgraduate program ‘Microenergy Systems Research Group’, Center for Technology & Society, Technische Universität (TU) Berlin, 10623 Berlin, Germany
2
Department of Environmental Technology, Chair of Circular Economy and Recycling Technology, TU Berlin, 10623 Berlin, Germany
*
Author to whom correspondence should be addressed.
Received: 21 December 2017 / Revised: 12 February 2018 / Accepted: 21 February 2018 / Published: 26 February 2018
(This article belongs to the Special Issue Energy and Agriculture)
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Abstract

Residues from bioenergy and ecological sanitation (EcoSan) can be utilized to sustain soil fertility and productivity. With regard to certain cooking and sanitation technologies used in smallholder households (hh), we systematically analyzed how utilization of the respective potentials to recover residues for farming affects (i) soil nutrient balances, (ii) the potential for subsistence production of composts, and (iii) environmental emissions. On the example of an intercropping farming system in Karagwe, Tanzania, we studied specific farming practices including (1) current practices of using standard compost only; (2) a combination of using biogas slurry, urine, and standard compost; (3) a combination of using so-called “CaSa-compost” (containing biochar and sanitized human excreta, Project “Carbonization and Sanitation”), urine, and standard compost. The system analysis combines a soil nutrient balance (SNB) with material flow analysis (MFA). Currently, nitrogen (N) and phosphorus (P) are depleted by −54 ± 3 and −8 ± 1 kg∙ha−1∙year−1, respectively. Our analysis shows, however, a clear potential to reduce depletion rates of N, and to reverse the SNB of P, to bring about a positive outcome. Composts and biogas slurry supply sufficient P to crops, while urine effectively supplements N. By using resources recovered from cooking and sanitation, sufficient compost for subsistence farming may be produced. Human excreta contribute especially to total N and total P in CaSa-compost, whilst biochar recovered from cooking with microgasifier stoves adds to total carbon (C) and total P. We conclude that the combined recycling of household residues from cooking and from sanitation, and CaSa-compost in particular, is especially suitable for sustainable soil management, as it mitigates existing P-deficiency and soil acidity, and also restores soil organic matter. View Full-Text
Keywords: integrated plant nutrient management; counteracting soil nutrient depletion; biochar; biogas slurry; carbon recovery; ecological sanitation; vegan organic farming integrated plant nutrient management; counteracting soil nutrient depletion; biochar; biogas slurry; carbon recovery; ecological sanitation; vegan organic farming
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Krause, A.; Rotter, V.S. Recycling Improves Soil Fertility Management in Smallholdings in Tanzania. Agriculture 2018, 8, 31.

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