| dc.description.abstract | Tea (Camelia sinensis L (O) Kuntze) is a major cash crop in Kenya contributing to the economy majorly through exports. Plant parasitic nematodes are widely distributed in tea fields and cause significant yield losses. In an effort to maximize production of green leaves from tea fields, farmers practice various cultural practices. Studies were carried out to determine the influence of farming practices and soil chemical properties on the abundance and diversity of nematodes as well as to evaluate the reaction of different tea clones to root knot nematodes. The experiments were carried out in Kangaita, Kirinyaga County, Weru, Tharaka Nithi County and Kionyo, Meru County. Three farming practices namely neglected, manure applied farms and inorganic fertilizer applied farms were used to assess the abundance and diversity of nematodes as well as the chemical properties of soil. Soil samples were randomly collected from the farms, nematodes were extracted, identified and quantified and chemical analysis was conducted on the soil samples. Tea clones TRFK 31/8, TRFK 430/90, TRFK301/4, TRFK 371/3, and TRFK 306/1 were assessed for reaction to root knot nematode infestation. Growth parameters assessed included stem girth, length of internode (internode space) and number of new (harvestable) leaves. Randomized complete block design was used. In both Kangaita and Weru sites, nematodes from all the five feeding groups (plant feeders, bacterial feeders, fungal feeders, predatory and omnivorous) were recovered. Nematode numbers decreased from neglected farms to manure applied farms to standard farms. There was a general reduction of the number of leaves produced, stem girth and internode space on clones TRFK 430/90, TRFK301/4, TRFK 371/3, and TRFK 306/1. Clone TRFK 430/90 was the most severely affected as most of the plants died while clone TRFK 31/8 did not show any significant effect on growth parameters. The farming practices had a significant effect on the soil pH, N, P, K and other trace elements in
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the soil. Soil acidity increased from neglected farms to manure applied farms and to NPK fertilizer applied (Standard) farms. There was a positive correlation between the soil pH and nematode abundance, species diversity and all the five nematode trophic levels. There was a negative correlation between exchangeable acidity and total organic carbon with nematode abundance and species diversity. The soils had generally low levels of potassium, magnesium and zinc due to rapid removal through harvesting of the young shoots and leaves. PPNs led to reduction in crop productivity and general physical health of tea plants. Clone 430/90 is highly susceptible to nematode attack while Clone TFRK 31/8 is tolerant to nematode infestation. The high use of NPK fertilizer led to acidifying of the soil. High soil acidity negatively affects both nematode abundance and species diversity. Farmers should follow good agricultural practices to realize maximum benefit from their farms. These includes application of inorganic fertilizers using recommended rates and use of farmyard manure to avert increase in soil acidity. Use of resistant/tolerant plant cultivars/ tea clones will also help the farmers maximize yield and returns from their farms. Clone 31/8 can be recommended for planting in areas with incidence of plant parasitic nematodes. Clone 430/90 is highly susceptible to plant parasitic nematode attack and can only be grown when methods of nematode control are employed. More research is recommended on clone 430/90 to incorporate resistance to nematode attack. Manure application can be recommended as the most appropriate farming practice to maximize yield and reduce nematode numbers in farms. | en_US |
