Abstract
Conservation
agriculture (CA) is promoted extensively to increase the productivity
and environmental sustainability of maize production systems across
sub-Saharan Africa and is often listed as a climate-smart agriculture
(CSA) practice.
However, the impacts of CA on food security,
resilience/adaptive capacity and climate change mitigation are
location-dependent and it is unknown whether CA can simultaneously
address CSA’s multiple objectives. Here we evaluate four variations of
CA: reduced tillage plus mulch (mulch), reduced tillage plus mulch and
leguminous cover crop (Lablab), reduced tillage plus mulch and
leguminous trees (CAWT), and reduced tillage plus mulch and nitrogen
fertilizer (CA + F)—for their effect on CSA-relevant outcomes in
highland Tanzania maize production. By comparison to conventional
practice in the region, intensification of maize production by Lablab,
CAWT, and CA + F significantly increases yields by 40, 89 and 77 %,
respectively. Likewise, rainfall use efficiency was highest in these
three treatments and significantly greater than conventional practices
in 7 of 12 comparisons. Seasonal and annual greenhouse gas fluxes were
similar across all treatments; however, yield-scaled global warming
potential (Mg CO2 eq Mg grain−1) was lower in CAWT
(2.1–3.1) and CA + F (1.9–2.3) than conventional practice (1.9–8.3),
averaging 62 and 68 % of the emission intensity of conventional
practice, respectively. The findings demonstrate that CA can deliver
benefits consistent with the objectives of CSA for farmers in this
region, particularly when soil nitrogen limitation is alleviated,
providing other constraints to adoption are removed.
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