Abstract:
Weed competition is one of the most important limiting factors in
tea crop cultivation in Sri umka. Nearly 80% of the total tea
area is under seedling tea with poor crop-canopies, creating
an ideal environment for weed growth as weeds can compete with tea
crop for applied and soil borne nutrients soil moisture and
sunlight, and can adapt to extreme climatic conditions.
There is a scarcity of available information on th~ nutrient
removal by weeds in tea fields. The main objective of this thesis
f . was therefore to study the removal of applied fertiliser nutrient&
and soil-borne nutrients .by weeds grown in both vegetatively
propagated and seedling tea fields, following NPl fertiliser
application, at different growth stages.
In this study, a good canopy VP tea field trial and a poor
canopy seedling tea trial, were used, to study the growth of
all the available weeds, their N-, P-, K-, Ca-, Mg and Alconcentrations and uptake of these nutrients, 3-, 6-, 9- and 12
weeks after NPK fertiliser application. These results were
rationalised with respective tea-crop parameters obtained from
these 2-field trials. In addition, a glass house experiment was
carried out with Commellina diffusa, Crassocephalus crepidioides,
Panicum repens and Conyza floribunda with 2xdifferent levels of
Nand K fertiliser, to study the above parameters at similar
time intervals.
All the available we-ed shoots have removed upto about 6% of N,
13%of P, 10% of K and 25% of Mg of the total N,P,K and Mg removal
of both VP tea + weeds in the mature VP tea field, and have
r~moved upto about 12% of N, 12%of P &22% of K of the total N,P
and K removal of both seedling tea+weeds in the seedling tea field.
II
This greatest removal of applied fertiliser nutrients
observed about 3-6 weeks after NPK fertiliser application.
was
This study showed the need for controlling weeds in both VP and.
seedling tea fields after about 3-6. weeks period from the NPK
and Mg fertiliser application, in additio~ to the weed control
measures presently being adopted, generally before fertiliser
application, due to the removal of considerable amounts of these
nutrients by growing weeds, in order to improve the availability
of soil nutrients for tea crop which inturn would improve the
tea crop yield.
