THE SOIL PRODUCTIVITY RESEARCH LABORATORY (SPRL)

INTRODUCTION

SPRL is a unit of the Chemistry & Soils Research Institute under the Ministry of Agriculture, Mechanization & Irrigation Development (MAMID). SPRL composes of 4 subsections, viz; Chemistry Laboratory, Physics Laboratory, Microbiology Laboratory and the Legume Inoculant Factory

The Factory is based at Grasslands Research Station in Marondera, 74 km East of Harare.  It was established in 1962 with the mandate to provide Rhizobium inoculants farmers.  It is the sole producer of inoculants in Zimbabwe and one of the largest in Africa.  The factory is

supported by an independent but publicly owned microbiology laboratory which in addition to maintaining the Grasslands rhizobium culture collection and setting standards is also responsible for quality control, research and development and preparation of the rhizobial mother cultures.

Legume biological nitrogen fixation (BNF) is recognised as the cornerstone of sustainable agricultural systems in Africa.  The BNF process occurs through a unique, natural symbiosis between leguminous plants and the nitrogen-fixing bacteria rhizobia.  Seed inoculation with selected rhizobia is a cheaper and usually more effective agronomic practice for ensuring adequate nitrogen fixation than the application of fertilizer nitrogen.  But these benefits are dependent on the reliable production of high quality and affordable inoculants.

The Microbiology Laboratory

In addition to setting standards and performing Quality control duties, the microbiology laboratory maintains one of the largest culture collections of Tropical Rhizobia in the world, known as the Grasslands Rhizobium collection which currently stands at more than 500 strains.

Maintenance of the Grasslands Rhizobium culture collection

The collection is one of the 10 largest in the world and is included in the world catalogue of Rhizobium collections and in the World Directory of Collections of Cultures of Micro-organisms as collection no. 34, acronym MAR.  Regular sub-culturing is done twice, at yearly intervals on all the collections maintained at various sites and temperatures underground in a fire-proof box to ensure the collection remains intact.  The collection was started in 1958 by Dr DHL Corby and built up mainly from locally isolated strains as well as imported ones.  Until 1968 it contained 709 strains from 360 species of legume.  Removal of ineffective isolates and duplicates and the dying out of some strains has now reduced the number of strains to 543 strains from 230 legumes.  Cultures of strains from the Grasslands collection are sent on request to research workers in other parts of the world.

Rhizobium Inoculant Production

Upon establishment in 1962, the factory was producing modest quantities of inoculants (less than 5000 units per annum) for a few pasture legumes, mainly lucerne and clover species.  In 1967 production of soyabean began and as the Grasslands Rhizobium Collection grew, inoculant production expanded to include almost all grain and pasture legumes grown in Zimbabwe. Although currently the factory produces about 50,000 packs (each pack weighing 100g) of legume inoculants annually, it has an annual production capacity of over 200,000 packs.  The amount produced is governed by demand. About 90% of the inoculant produced is for soyabean and is sold to farmers at a cost of $5.00 per unit.

Since 1962 inoculant was produced on agar based medium in glass bottles.  Increasing costs of bottles, chemical ingredients and agar led to the development of solid-based inoculants.  From 1981, inoculant has been produced using ‘bagasillo’, a fine bagasse dust and by-product of the sugar industry, packed in sterilizable polythene bags.

DISTRIBUTION AND MARKETING

Inoculants are sold directly from Soil Productivity Research Laboratory in Marondera and Chemistry and Soil Research Institute at Harare Research Station along 5^th St Extension (Opposite Royal Harare Golf Club adjacent to the State House).  Inoculants are also made available at various Agritex Provincial and District offices throughout the country. Agro-distributors approved by the Institute also sell inoculants using their outlets in different parts of the country at a flat price of $5 per unit. These include Seed-co, ZFC, Shallom Distributors, Vet Distributors, Windmill, Zim Gold just to mention a few.  The bulk of the inoculant is sold within Zimbabwe; however, Seedco exports some of the inoculant for sale in Zambia and there are also buyers from Mozambique who buy directly from SPRL.