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

PIGEON PEA/COWPEA INTERCROP + MAIZE + CASSAVA ROTATIONS
ON SMALLHOLDER FARMS IN THE SOUTHERN
COASTAL AREA OF MOZAMBIQUE
Abstract
CANDIDA CUEMBELO
INIA, Caixa Postal 3658, A v. Das FPLM, 2698,
Mavalane, Maputo 8, Mozambique
Low soil fertility is a limiting factor for agriculture production in Mozambique that is aggravated by unsustainable
cropping systems used bysmallholding farmers. They practice rainfed low input agriculture on land areas that range
from 0.5 to 4 hectares.
This paper gives the background and brief information on results from a very initial set of on going on-farm rotation
experiments on nutrient management carried out in Inharrime district within Inhambane province in southern Mozambique.
The experiments are conducted on farmers' fields located in smallholder farming areas surrounding Nhacoongo
Research Station and are based on legumes in rotation and intercropped with maize and cassava. Crop residue incorporation
was considered part of the technology. Of the five sites (one farmer=one site), harvesting of cowpea took place in
three sites only because of environmental stresses and yields were low..
Key words: Legume, maize, cassava, intercrop, rotation, lin farm experiment
Introduction
Low soil fertility is one of the most limiting factors
for agricultural production in Mozambique, plus
climatic irregularity and adversity and soil erosion,
aggravated by unsustainable cropping systems used
by small-holding· farmers. In general, the soils of'
Mozambique are low to moderate fertility.
Inadequate soil fertility is one of the major biophy,?ical
constraints for crop production. Soil fertility de­
pletion is continuous due to nutrient losses caused
by poor soil husbandry and extractive traditional
methods of cultivation with no replacement of nu­
trients by smallholder farrriers. They practice rain
fed agriculture in land areas that range from 0.5 to 4
hectares. On average, smallholder farmer maize
yields are very low (about 200-400 kg/ha) and inorganic
fertilizers are unaffordable, aggravated by
constrained access to credit systems.
In addition, Mozambique's agriculture production
has been greatly affected by the civil war that ended
in 1992 followed by adverse conditions such as
droughts and floods resulting in a large food deficit.
Thus, there is a need to increase crop production,
particularly at the level of small farmers. Sustain­
able soil fertility management practices have to be
developed, recommended and adopted if the objectives
of food security and sustainable natural re­
source management are to be achieved.
Inharrime district is located on soils that are representative
of soils in the coastal belt where low fertility
is the major constraint to crop yields. Sandy soilS
are predominant that are characterized by low nu­
trient reserves, low organic matter content and low
cation exchange capacity. Nhacoongo research sta­
tion is located within this district and it was the
ideal place within Inhambane province for the experiment
on rotations.
In Mozambique, about 90 percent of food production
is from Tainfed systems. The major food crops
are maize, sorghum, millet, rice, cassava, bean and
groundnut and other additional crops and fruit
trees mostly intercropped. The major part of crop
production is subsistence and low input/low out­
put in nature. Commercial farming contributes only
about four percent of total production. The highest
human population density of the agricultural re­
gions is in the coastal belt south of the river Save.
There is no correlation, in the south, between population
density and envirorunental conditions, particularly.
climate and soils. However, there is a
strong correlation between climate and crop distri­
bution. Cassava and maize are the basic staples of
this area, and they are known to deplete soil nutrients.
Mainly because of the environmental conditions,
maize production has declined in some areas
and cassava has expanded. For many areas, the introduction
of new technologies for soil fertility im­
provement may reverse the situation.
Grain legumes and Green Manures for Soil Fertility in Southern Africa 155