Dr Bruce Knight of the legume Technology, UK, was in Zimbabwe on 26th June-2nd July 2011 to work with staff of the inoculant production plant at the Soil Productivity and Research Laboratory (SPRL), Marondera. Legume Technology Ltd is the producer of LegumeFix inoculants for various legume crops and Bruce was engaged by N2Africa as a consultant for his tremendous experience in the inoculant manufacturing industry. His task was to familiarise himself with the technical aspect of production and recommend changes in production process, equipment and other resources that will result in a more efficient and cost-effective process of production and a high quality product.
Working with Ms Mazvita Murwira of SPRL, Bruce looked at the major production steps and made some useful observations and far-reaching recommendations which, if implemented, could bring about a tremendous cut in production costs and a substantial enhancement in the shelf-life of the inoculants from the current 6 months to as much as 2 years. Some of the major highlights of the recommendations include the following:
- Improve the particle size of the inoculant carrier by milling: Currently, SPRL uses bagasse, a sugarcane by-product, as the inoculant carrier. The raw bagasse arrives the factory made up of a mixture of fibrous materials and finer particles with a wide range in particle size. This raw material is passed through a sieve to give a finer grade material. However, the sieved material was observed to still contain coarse particles which will require milling to finer grades. Milling will result in a more consistent particle size, higher moisture and nutrient retention and less wastage of bagasse because less of the material is retained on the sieve and thrown out.
- Introduce a full- or semi-automation of the sachet filling step: The current practice is that the processed carrier is weighed into the sachets manually. Automating this step will hasten the process, reduce man hours and result in a more consistent weight.
- Adopt a 2 cycle heat sterilising process with a longer dwell time at 121oC: The existing practice is to sterilise the sachets using an autoclave at 121oC for about 15 minutes. This may not achieve full sterility. An additional cycle and longer periods of sterilisation will ensure a more sterile product and hence result in a longer shelf life.
- Train staff on how to use the freeze dryer in the laboratory: At present there is no member of staff trained on how to use this equipment and this means that the rhizobial strains in SPRL’s culture collection are being eroded with no practice in place to maintain the stocks.
The recommendations also looked at various options available in modifying certain production methods and the quality assurance process. One of the exciting observations made by Bruce is the endorsement of the microbiological practice in the laboratory. According to Bruce, ‘’The Head Technician, Catherine, working at Maronderra has a good grasp of technique and the demonstration - using the starter medicine bottles to inoculate the 1.5L flasks included a QC test of the medicine bottle culture. After 3 days of growth, the CRYMA (Congo Red – yeast extract mannitol agar) plate was clean and showed growth exactly as you would expect from a Bradyrhizobium culture’’. This is one of the many strengths that N2Africa hopes to build on to get the inoculants produced at SPRL globally competitive. Given that SPRL is the longest established inoculant manufacturer in Africa and has remained in production even under very difficult and trying periods, this is the least the project can do to reward commitment to service, self belief and perseverance.
By Mazvita Murwira and Abdullahi Bala