Nitrogen allocation and recycling in peri-urban mixed crop–livestock farms in Ethiopia

Abstract

Mixed crop-livestock (MC-LS) farms are assumed to be more environmental friendly than specialized livestock systems, due to their better options for internal nutrient recycling. However, there are large differences among MC-LS farms in nutrient allocation and recycling. Here, we posit that the relative allocation of nitrogen to crop and livestock compartments, expressed as crop-livestock ratio (CLS), determines the performance of MC-LS farms. Among 300 urban and peri-urban farms studied in 2014, 42 MC-LS farms (Addis Ababa: 20; Jimma: 22) were re-interviewed in 2016, using MonQIt (monitoring tool) questionnaire. The performances of these farms were evaluated using partial nitrogen balance (PNB), N use efficiency (NUE), N recycling index and net farm income (NFI). CLS was negatively related to N input, PNB and NFI. Livestock oriented MC-LS farms had 4-5 times higher N input and 7 times higher PNB than crop oriented MC-LS farms, because they had 2-4 times higher NFI and purchased more external N input. This indicated that N allocation has significant environmental and economic implications. Sensitivity analyses suggested that NUE at farm system level can be improved by 20-25% and N recycling (NR) by 10-20% over the current condition. In conclusion, MC-LS farms are diverse, and much of the diversity can be captured by the CLS indicator. NUE and NR of peri-urban MC-LS farms in Ethiopia can be significantly improved through NUE enhancing measures: targeted exchange of crop residues and manure between crop and livestock activities within and between farms and improving animal NUE through breeding and precision feeding. Keywords Crop-livestock ratio (CLS) Á Smallholder Á NUE Á Food security Á Circular economy

Manure recycling from urban livestock farms for closing the urban–rural nutrient loops

“…These crop farms had on average 1.7 ha of land and 4 TLU per farm (Table 2), and had negative N and K balances and slightly positive P balances (Table 3), despite 2 TLU ha -1 . Likely, most feed was produced on-farm and little imported, because mixed farms with relatively large area of crop land invest relatively little in animal production (Tadesse et al 2019); the N, P and K excretion coefficients applicable for the livestock in these mixed crop farms were likely at the lower end of the range used in our calculations (Table 4). The negative N and K balances indicate that there was little exchange of manure between livestock farms and crop farms in the urban zone; crop farms with nutrient depletion co-existed next to livestock farms with large manure nutrient surpluses.…”

“…The two cities differ in their bio-physical characteristics and agro-ecology. Addis Ababa has ten sub-cities; most of the UPA farms are found in five sub cities (Abdalla et al 2011;Tadesse et al 2019) and these were selected for this study. In Jimma, all eight urban woredas (districts) within the city were selected (Table S1).…”

“…Bicudo 2009and Sutton (1994) reported recovery fractions of 0.4-0.6 for N, 0.6-0.8 for P and 0.5-0.7 for K in manures from open manure storages. Most livestock farms in Addis Ababa and Jimma have no leak-tight stables and manure storage systems (Tadesse et al 2019), but recovery fractions have not been quantified. Based on this data, we used two sets of recovery fractions for N, P and K in manure: 0.3-0.5 for N, 0.6-0.8 for P, and 0.5-0.7 for K. The recyclable amounts of N, P and K in manure were estimated from the manure N, P and K production per zone and the recovery fractions.…”

Urban nitrogen budgets: flows and stock changes of potentially polluting nitrogen compounds in cities and their surroundings – a review

“…Again characterized by huge variability, average application rates of almost 100 kg N ha −1 yr −1 were determined for systems that would not target for production. Analyses also were available under N deficit conditions (Tadesse et al 2019) in two periurban regions in Ethiopia. Livestock-oriented mixed farms had higher income, obtained external sources of N and hence 4-5 times higher N input, but a poor nitrogen use efficiency (NUE) compared to crop-oriented mixed farms.…”

Exploring the Recycling of Manure From Urban Livestock Farms: A Case Study in Ethiopia

“…These manure disposal practices may create serious environmental [11,14] and human health problems [15] and are not sustainable because they waste non-renewable resources (e.g., phosphorus extracted from finite mineral deposits) [16] . Thus, urban livestock manures and household wastes have to be seen as resources for enhancing crop yields and soil health [13,17,18] , and for realizing a circular economy [19] .…”