creating virtuous cycles in soil management to reduce fertilizer use in africa

Creating Virtuous Cycles in Soil Management to Reduce

Fertilizer Use in AfricaProf. dr. Paul Mapfumo

Department of Soil Science & Agricultural Engineering

UNIVERSITY OF ZIMBABWE&

Soil Fertility Consortium for Southern Africa (SOFECSA)

University of Zimbabwe


“Our focus is on transforming African agriculture and food systems through management of soil ecological processes: as a fundamental precondition for the continent’s sustainable development”

Food and nutrition insecurity is at the core of Africa’s development problem

80% for food production attributable to smallholders Huge yield gaps continue to exist due to poor soil fertility Large scale-scale commercial entities not necessarily benefiting

the vulnerable farming families (e.g. have no access to output markets)

Potential benefits local ecological diversity ignored in favour of external input agriculture based on monoculture : even against all odds

Introduction


Back then... We were poor but not hungry..... Now we are ‘Poor and Hungry’?

Common Quote from farmers in Southern Africa

lamenting the loss of agroecology?..


Less obvious links between soil biogeochemical processes and poverty traps: lamenting the loss of agroecology Nutrient mining and ‘Maize poverty traps’ in E &

SAfrica Shrinking arable/grazing lands: Soil erosion &

land degradation Extensification and nutrient transfers in crop-

livestock systems (e.g. semi-arid agro-ecologies) Soil organic carbon depletion: degradation of

wetlands (loss of ‘food supply buffers’) Breaking of tight nutrient cycles in fragile

environments: e.g. declining soil productivity in miombo-ecozones)


Mazhanje (Kg fresh weight) per year

0 100 200 300 400

Resource Endowed

Intermediate

Resource Constrained

Consumed (SED =6.81) Sold (SED=13.95)

Vulnerable households more dependent on local ecological

diversity

Chagumaira et al 2015Woittiez et al., 2013


1. Harnessing local ecological diversity: The Indigenous legume

fallow (Indifallow) Concept Naturally growing indigenous

legumes collected by farmers Local technique (by smell)

developed to enable farmers to distinguish between legumes & non-leguminous plants in the field (Mapfumo et al 2005)

Mixed stands of legumes sown on farmers’ abandoned fields & left for 1 or 2 seasons

Dominant and competitive species defined the biomass yield


2. Managing different quality organic resources for improved soil health

and efficient use of external inputs using ISFM Farm-available organic resource

chemically classified into three different quality soil organic matter inputs: Pinus patula sawdust: low (<2%

N, >15% lignin and >4% Polyphenols)

Maize stover, cattle manure & Calliandra: medium

Crotalaria : high (> 2% N, <15% lignin and < 4% polyphenols)

Applied to soil annually in same quantities into maize plots over 12 years


Experiment demonstrated:

Unsustainability of monocropping despite consistent fertilizer use

Continuous decline in exchangeable base nutrients

Declining use efficiency of macronutrients supplied in fertilizers (hence increased rated)


Organic matter management for enhanced soil health: Case of nematodes

and N-rich organic resources in maize

Callian

dra Callo

thyrsu

s

Crotala

ria jun

cea

Zea m

ays (M

aize)

stover

Cattle m

anure

Pinus

patul

a saw

dust

Contro

l 0

20406080

Mean Nematode Count (10g-1 maize root dry

matter)

Callian

dra Callo

thyrsu

s

Crotala

ria jun

cea

Zea m

ays (M

aize)

stover

Cattle m

anure

Pinus

patul

a saw

dust

Contro

l -5050

150250350

Change in Mean Nema-tode Count (100g-1 soil)


3. Using agro-ecological principles to reclaim

degraded soils: Farmers often abandon field due to loss

of productivityKick-starting productivity through Indifallows (Nezomba et al., 2010)


Restoration of degraded soils...Sequencing of ISFM options enhanced crop yield response to fertilizer application: reducing demand for high external inputs (Nezomba, Mapfumo et al., 2015)


ISFM sequencing helping to build soil P capital in the short-medium term

Nezomba et al., 2014, Exp.Agriculture


4.Intercropping, rotational and mixed cropping systems sustaining yields and food provision for most African

farming families

Potential for integrating trees - which species???


5. Soil geochemistry applications for for agriculture and health

Study focusing on soil geochemistry and agrobiodiversity with empahasis on Zn, Fe, Se and I in southern Africa

Funded by DFID and Royal Society (UK) The agroecology framework seen as holding

promise against industrial bio-fortification for improved human health and wellbeing in Southern Africa

Three countries participating

“There is a critical need for investment into more scientific research to support agro-ecology in Africa and improve food and nutrition security for millions of households”


THANK YOU

creating virtuous cycles in soil management to reduce fertilizer use in africa

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