The TRFCA adopted a project based research programme from 2004. Below are research highlights of the projects conducted from 2004 to 2011. Some projects were suspended due to budgetary limitations while a few were sustained and are continuing.

Project 1a: Genetic improvement of tea (yield and quality attributes)

The project was conducted with the aim of establishing rapid and reliable selection criteria for cultivars with desired traits such as tolerance to drought; high temperature and high made tea quality. This would facilitate the development of drought tolerant and high quality vegetatively propagated (VP) cultivars with good growth characteristics in the cold and hot seasons. Results from this research showed a positive relationship between taster’s valuation and colour of the flush on the bush and fermentation rate determined by the chloroform test. Long and deep rooting as well as high starch content in the roots were good indicators of drought tolerance whereas low leaf to root ratio was important for tolerance to high temperature. Molecular studies identified three random amplified polymorphic DNA (RAPD) markers associated with drought tolerance (RAPD 7, RAPD 27 and RAPD 44), two markers associated with high quality (RAPD 16 and RAPD 21), one marker negatively associated with poor tea quality (RAPD 29), while another marker associated with good growth in the cold season. Use of these screening methods will help to improve efficiency in the tea breeding programme.

Project 1b: Field Gene-bank

This project aims to conserve tea germplasm that could be lost through replanting with improved vegetatively propagated cultivars.  This will likely be useful in future breeding and development of elite tea cultivars. A total of 267 accessions collected from the tea estates in Malawi were planted in a field gene bank at Mimosa and have been characterized for various morphological, physiological and biochemical characteristics. This information will be useful in stratifying the selections for future use in the breeding programme. TRFCA released cultivars and some of the parental stocks used in the breeding programme have also been planted in one field  close to the gene bank for demonstration purposes and monitoring of some field attributes.

 

Project 2: Upgrading of nursery facilities and production of rooted plants

This project was conducted with the aim of upgrading the propagation facilities at TRFCA in order to facilitate research in tea propagation as well as large scale production of plants for sell to growers. Funding for the upgrade was provided by the European Union.

 

Project 3: Enhancement of nursery plant growth and early field establishment

The project aimed at developing technologies for enhancing rooting and growth of plants in the nursery as well as good establishment and high productivity in the field. The results showed that use of rootstim rooting hormone enhanced early rooting of tea cuttings whereas foliar application of Calmag+B and magnesium sulphate enhanced post-rooting growth in the nursery. Field planting at young age (4-6 months old plants) was feasible under optimal field management. Digging big hole or trenching was only beneficial under marginal soil conditions. Plants propagated from plucking shoots planted in the field at young age would only require 2- 3 prunes in the first six years. The first prune could be delayed up to the third year especially for cultivars with a spreading growth habit provided the plants are kept under plucking in the first two years.

 

Project 4: Tea shoot growth and optimum plucking round

Among the factors that affect made tea yield and quality is the length of the plucking round which can either be cultivar or season or location dependent. Some cultivars require a longer plucking round length than others.  In the cool dry season in Malawi, rate of shoot growth is slow and the cycle is longer than 10/11 days..

The objective of this project was to establish optimum shoot age and optimum plucking round for the different commercial cultivars so that plucking is done at the right time when majority of the shoots have reached the required plucking standard and when the proportion of  2 + bud and 3 + bud shoots is highest.

Results showed that most of the cultivars have a shoot replacement cycle of 42 days while others have a replacement cycle of 38 / 39 or up to 49 days depending on the growing conditions. The 42 days replacement cycle validates the current plucking rounds of 10/11 days or 14 days. Optimum plucking round experiments showed that 16/17 days was the optimum plucking round length for SFS 150 at Mimosa during the rainy season. Yields from the 10/11 days round, the current commonly used plucking round, were not significantly different from those of other tested rounds for SFS 204 at Mimosa and Satemwa, suggesting that growers could plan to put some fields under longer rounds to cope with labour shortages during the main season.

Project 5: Mechanical harvesting of tea

Availability of labour to pluck tea at most estates is a critical constraint to production of tea, and successful machine plucking could address this problem. The objective of this project was to generate information and procedures on how plucking of tea could be successfully mechanized by reducing the negative effects of machine plucking on yield and quality.

The results showed that made tea yield declined with time under mechanical plucking on seedling and vegetatively propagated cultivars. Physiological studies done later revealed that the yield decline was due to continuous removal of immature shoots and buds by the machines which created a sink-limitation on photosynthesis on the bush. A 14-day plucking round and raising the plucking blade after every 2nd or 3rd round gave the best compromise for yield and green leaf quality of the plucked leaf.

 

Project 6: Management of high soil acidity,

Low and high soil pH can be major impediments to increased made tea yields. It was suspected that low yield at some estates was caused by low soil pH but there was no information about the extent of this problem at estate level. It was further suspected that the soil pH was decreasing at some estates due to long-term use of nitrogenous fertilizers and some growers had subsequently started liming their fields in order to reduce the effect of this problem on yield. The objective of this project was to determine the magnitude of the problem at all estates in Malawi and thereafter find ways of redressing it.

Soil pH survey conducted in 2006 showed that soil acidity was widespread on tea estates in Malawi.  There was positive correlation between pH and yield. The results further revealed that other factors were responsible for limiting tea yields than soil acidity at pH levels of 4.

 

Project 7: Crop management of yield and quality of tea,

Despite the recommendations from the Tea Research Foundation of Central Africa on good agricultural practices for optimal yields, tea production practices vary between estates. The objective of the project was to identify the most important production factors and establish database of these factors for use by the tea industry. Growers would then intervene with appropriate practices to raise the total value (productivity and quality) of the existing seedling and vegetatively propagated (VP) cultivars.

A survey was conducted at all tea estates. Data was recorded by estate on production practices including: the levels of fertiliser application, plucking methods, pruning cycles, the rainfall, temperature and other environmental conditions. These data variables were correlated to tea yields at each estate. The survey further documented growers’ own practices not recommended by the Foundation.

The results showed that yield was negatively affected by an increase in altitude and plant population,  method of harvesting, heat units and maximum temperature. On the other hand increase in nitrogen and number of years after down pruning had positive influence on yield. Differences in yield between estates were mainly due to type of cultivar, plucking methods, nitrogen rate and plant population.

Field practices not found in the Planters' Hand book but were done by some growers included pruning during the main season from November to January,  and lung pruning.

Project 10: Tea Quality

This project was done to identify critical market requirements on tea and to characterize Malawi teas for the desired characteristics in order to increase profit margin through production of high quality teas and tea by-products. The study established that Malawi teas are characterized as plain (without aroma), with coppery red colour of the infused leaf, and its liquor being bright, strong, brisk and taking milk well. The study also established that tea quality is negatively influenced by fast growth of the shoots in the main growing season, high nitrogen rates, shade and coarse plucking.


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