IN the previous instalment, as we tried to demystify soya bean and turn it into a people’s crop, we looked at what kind of soils are suitable.
We also touched on some important agro-climatic conditions required, such as amount of rainfall.
We saw that, generally, soya bean yields increase as the clay and organic matter content of a soil increases.
Soils with textures ranging from loamy sands, clay loams to red and black clays will support soya bean production.
Yields increase with rainfall from a minimum of around 600 mm per annum.
As a general rule, rainfall that is enough for a good maize harvest is also sufficient for soya bean cropping.
The crop is sensitive to the day length and grows best in summer when the days are long and there is plenty of sunshine with warm to hot temperatures .
Soya bean cannot be grown in winter when the days are short and temperatures tend to be lower too.
In this our third episode looking at the soya bean story in Zimbabwe, we shall look at some of our experiences leading the formation of the University of Zimbabwe (UZ)-led Soya Bean Promotion Programme from 1996 to 2006.
The experiences will hopefully inform future soya bean promotion initiatives.
When we first thought about promoting soya bean production among small-holder farmers, seeds, fertilisers and other agro-chemicals were cited as the main constraints.
My own experience with soya under experimental research conditions (laboratory and greenhouse) was cultivated through postgraduate training, while my field experience was limited to highly mechanised systems encountered as a research student on commercial farms in the US.
In the circumstances I could not jump into the field to promote soya bean among small-holder farmers in Zimbabwe without first testing the waters.
I started small with just two farmers; one on distinctly sandy soils and the other on light red clay soils in Musana Communal Lands.
The work was part of my doctoral thesis research.
I worked with two undergraduate students who looked at the response to inoculation of several commercial soya bean varieties.
Soya bean was completely new to the farmers.
We quickly discovered that soya bean grew better if the soil had more clay content and very poorly in pit sand such as that used for building.
As part of the studies, we checked the local soils for the presence of the nitrogen-fixing nodule bacteria (rhizobia). Different legumes have different rhizobia suited to them.
For example, soya bean rhizobia will not form nodules on cowpea and vice-versa.
We found that groundnut and cowpea roots had many nodules showing that the soils contained large quantities of rhizobia.
These legumes grew well and had dark green leaves, a clear signs that the plants were receiving adequate amounts of nitrogen fertiliser supplied by the nodule bacteria.
On the other hand, soya bean plants looked yellowish and miserable.
When we dug up and examined the roots, there were no nodules.
The plants showed nitrogen deficiency.
These observations told us two things: First that the soils did not have rhizobia for soya bean; that is why the roots had no nodules and second, that the nodules on the groundnuts and cowpeas were supplying the plants with nitrogen fertilisers since the plants looked green.
We also became aware that soya bean had never been grown in these soils in Musana Communal Lands.
That might explain why soya bean had no nodules on its roots. The indigenous rhizobia did not ‘know’ this strange new plant, the soya bean.
So they did not touch it!
Local legumes have become adapted to indigenous rhizobia in our soils, hence they are well-nodulated.
Anyway let us get back to the soya bean story.
Through our research trials in Musana Communal Lands from 1990 up to 1995, we learnt many things about soya bean.
Soya bean grew well on the red soils near Musiiwa Growth Point but poorly in the sandy soils in neighbouring Guwa Village.
Since most communal area soils across Zimbabwe are sandy, we felt that more research was needed to see how best soya bean could be produced in these areas.
We shall find time to describe some of these research trials that we carried out to identify the best management practices for a good soya crop.
We also found that soya bean rhizobia applied as inoculant survived poorly in the sandy soils resulting in very low nodule numbers on the soya bean plants.
But in the red clay soils, the roots were thickly covered with nodules with the plants looking green and healthy.
In fact, in subsequent research years later, we found out that if we increased the amount of inoculant, the number of nodules on the roots increased as did the yield of soya beans.
In 1995, we felt that we had learnt enough about growing soya in communal area soils to consider promoting the crop.
We wanted farmers to benefit from soya bean’s soil fertility improving properties.
We called a big meeting of stakeholders from both the public and private sector.
This meeting highlighted the merits of producing soya bean for both local consumption and export.
It was pointed out that soya has many uses ranging from food for humans and livestock as well as its ability to improve soil fertility through nitrogen fixed in root nodules by rhizobia, the nodule bacteria.
The workshop participants decided to set up a Soya bean Promotion Task Force to spearhead promotion of the crop. The UZ was tasked with mobilising funding and carrying out appropriate research on the best ways of growing the crop under communal area cropping conditions.
The department of AGRITEX undertook the co-ordination of soya bean promotion work in the rural target areas.
In fact, no training session was carried out unless AGRITEX staff were involved.
This was a deliberate strategy for sustainability.
Extension staff are found in every ward of the country.
The Task Force consisted of representatives from agro-based private sector companies, public sector entities such as AGRITEX and the Department of Research and Specialist Services as well as farmers unions.
The Soya bean Promotion Programme became a truly collaborative effort.
We recruited volunteer neighbouring farmers who were clustered in groups of fives for a total of 50 farmers in the pilot first year.
We gave the farmers a one-day training course and provided them with inputs to plant 0,4 ha (one acre).
These inputs were provided as starter packs.
Each consisted of 10 kg each of four varieties, basal fertiliser, rhizobium inoculant and lime.
The lime was provided to neutralise soil acidity which we found to be common in most communal sandy soils.
All the plots were farmer-managed from land preparation, inoculation of seed with rhizobium, planting by hand, weeding after plant germination and harvesting.
In the very first season (1996/97) farmers produced wonderful crops.
The results literally blew out the myth that soya bean is too sophisticated for communal farmers.
Given adequate inputs and training, black communal farmers are capable of successfully growing soya bean.
In the next episode we shall go to the ground and describe some of the crop management practices that farmers followed to get good crops. This, we hope, will encourage others to adopt this lucrative crop – soya bean.