Grain Legumes and Green Manures for Soil Fertility in ... - cimmyt

RISK DIVERSIFICATION OPPORTUNITIES THROUGH LEGUMES IN
SMALLHOLDER FARMING SYSTEMS IN THE
SEMI-ARID AREAS OF ZIMBABWE
RICHARD FOTI, JOSEPH RUSIKE and JOHN DIMES
feR/SA T-Bu/a wa yo, PO Box 776, Matopos Research Station, Bu/awayo, Zimbabwe
Abstract
This paper uses a simulation modeling approach to evaluate the long-term diversification gains and risks associated with
adoption of a range of fertility options, including legumes, manure, and small doses of inorganic fertilizer in semi-arid
areas. These options were tested by the Department of Agricultural Research and Extension (AREX), the International
Crops Research Institute for the Semi-Arid Tropics (ICRISAT), the Tropical Soil Biology and Fertility Programme
(TSBF), the International Maize and Wheat Improvement Center (CIMMYT) and the Smallholder Dry Areas Resource
Management Project (SDARMP) in farmer participatonj research trials during the 1999/2000 and 2000/2001 cropping
seasons in pilot areas in three semi-arid regions in Zimbabwe. The study tests the hypothesis that legume-based soil fertility
technologies wi(l benefit farmers if diversification into legumes complements farmers' current investments compared
to alternative investments and the demand on resources is within the boundaries of the resource-endowments of
the fanners.
Results indicate that maize-cowpea and maize-groundnut rotations and maize-pigeon pea intercrops and rotations are
good investment opportunties for diversification from the traditional maize and sorghum soil-mining practices currently
being pursued by the majority of farm households.
Key words: Legumes, intercropping, rotation, risk simulation, diversification, return on investment
Introduction
During the past decade, there has been growing interest
in the use of legume-based technologies as
nutrient sources in smallholder farming systems in
Sub-Saharan Africa because of constraints on expanded
use of inorganic fertilizers. Historically,
legumes were grown as intercrops with cereals, especially
during pre-colonial times. In Zimbabwe,
agricultural extension has discouraged intercropping
in the pasf5() years and encouraged farmers to
grow pure crops targeted at commercial markets.
Despite this advice, farmers have continued to grow
legwnes intercropped with cereals albeit in small
areas. To re-introduce legumes into the system at
large enough scale to enable farmers to capture potential
benefits of biological i'h-fixation (BNF), the
legume technologies need to give a competitive rate
of return on investment compared to alternative investment
options available to households, meet
farmers' requirements for risk, and fit within the
boundaries of resource er~dowments of smallholders.
This paper uses a simulation modeling approach to
evaluate the long-term diversification gains and
risks associated with adoption of a range of soil fertility
options, including legumes, animal manure,
small doses of inorganic fertilizer and water management.
These were tested by the Department of
Agricultural Research and Extension (AREX), the
International Crops Research Institute for the Semi­
Arid Tropics (ICRISAT), the Tropical Soil Biology
and Fertility Programme (TSBF), the International
Maize and Wheat Improvement Center (CIMMYT)
and the Smallholder Dry Areas Resource Management
Project (SDARMP) in farmer participatory research
during the 1999/2000 and 2000/2001 cropping
seasons in pilot areas in the semi-arid regions
in Zimbabwe.
Objectives
The general objective of the study was to assess the
potential for adoption of legume-based soil fertility
improvement technologies. The specific objectives
are to:
o Estimate expected profitability and riskiness of
alternative legume technologies
o Determine the benefits offered by legume-based
soil fertility management tedmologies through
diversification to households with different resource
endowments and risk preferences.
Research Approach: Theory and Methods
The conceptual framework used for guiding the
study is derived from portfolio choice theory. Portfolio
theory provides analytical tools and methods
for analyzing farmers' decision-making under risk
Grain legumes and Green Manures for Soil Fertility in Southern Africa 79