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Universiteit van Amsterdam (2016)

What Comes Out, Must Go In : Macronutrient balance assessment of transitioning home garden systems in southern Ethiopia

Galle N.J.

Titre : What Comes Out, Must Go In : Macronutrient balance assessment of transitioning home garden systems in southern Ethiopia

Auteur : Galle N.J.

Université de soutenance : Universiteit van Amsterdam - Institute for Biodiversity and Ecosystem Dynamics (IBED)

Grade : Master programme : Environmental Management 2016

Descriptif
Smallholder-operated home garden agroforestry systems are the backbone of Ethiopia’s agricultural sector. In southern Ethiopia, enset (Enset ventricosum) and coffee (Coffea arabica) based home gardens have sustained millions of livelihoods for centuries, combining subsistence agriculture with a small cash crop income. Enset withstands drought, produces large volumes of food per unit area and is exclusively fertilized with organic matter, an internal input. The resilience of these systems relies on efficient nutrient cycling and multi-species composition. However, population growth induced land fragmentation has led to rapid replacement of enset and coffee with khat (Catha edulis), a lucrative cash crop and popular stimulant. Khat has expanded at the expense of land allocated to enset and coffee and threatens well-established internal nutrient flows within home gardens. The transition called for the definition of five distinct home garden types : four enset-oriented (enset-based, enset- coffee, enset-cereal-vegetable, and enset-livestock) and one khat-based. This paper describes macronutrient (NPK) balances calculated at component and farm level in Sidama and Gedeo, southern Ethiopia. Fields with the same or similar crop were grouped into five farm ‘components’. Livestock was also a component. Representative farms for each home garden type were conceived based on component land use. Processes quantified included mineral fertilizer, organic matter, internal fodder, external fodder and harvested products, removed crop residues, household livestock consumption, harvested products sold off-farm and whole livestock and livestock products sold off-farm. Component level balances added value to the study by permitting the comparison of internal flows, demonstrating the inherent diversity and complexity within home garden systems. Nutrient balances at the farm level showed positive nitrogen (N) balances, fluctuating phosphorus (P) balances and deficient potassium (K) balances, amongst all representative farms. Component level balances were similar but revealed the most severe K deficiencies were in the khat component. Measurements to address nutrient deficiencies, such as enset leaves as crop residue and proper manure handling, were presented and the urgency to develop strategies to reverse khat expansion at the expense of enset was stressed.

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Page publiée le 7 novembre 2016, mise à jour le 13 octobre 2018