Agriculture Reference
In-Depth Information
Fig. 4.6   Interpolation of groundwater and soil pH
Basically, Ratnapura belongs to low-country wet zone which receives more than
3,000 mm annual rainfall. It causes extensive leaching of basic cations from the top
soil to make it acidic. However, groundwater and soil are slightly acidic in the area
where the pH is ranging from 5.7 to 6.8 and 5.1 to 6.5, respectively (Fig. 4.6 ).
Tea is better grown in slightly acidic soils where growth is optimum at 4.5-5.5
pH range. Considering the fact (optimum pH), major part of the study area which
shows soil pH less than 5.7 is therefore suitable for tea plantations. Interpolation of
water and soil electric conductivity is given in Fig. 4.6 .
Calcium and magnesium are macronutrients which are required in large quanti-
ties for better plant growth and productivity, hence, tea yield shows positive cor-
relation to dolomite and kieserite application (Krishnapillai 1991 ). Sivapalan and
Krishnapillai ( 1988 ) reported that tea growing soils contain lower Mg concentra-
tions. Furthermore, this is claimed as a possible limiting factor for better yield.
Therefore, general recommendation was to add Mg-enriched fertilizer mixtures,
particularly when soil pH is 4.2 or low. Mg in the study area is found in the inter-
polation plate 14. According to this, Mg concentration is less than 4.1 ppm in major
part of the study area. Compared to upcountry tea, Mg concentration is higher in
low-country tea (Hasselo 1965 ). Soil Ca concentration in the study area ranges from
8.4 to 28.8 ppm. Typically, Ca concentration in fresh water falls below 10 ppm (Ra-
mesh 1996 ). The groundwater Ca concentration in the study area is at its lower side,
where major part of the area shows less than 4 ppm. However, it was in the range
from 0.3 to 11.9 ppm. So, it can be inferred that carbonate rocks like limestone,
dolomite, etc., are present in SE part of the study area, precisely in the Palm Garden
Estate. Also, anomalies of soil Mg and Ca concentration account for high fertilizer
input in those regions.
Soil pH and texture play a significant role in Zinc (Zn) availability. Alkaline and
coarse textural soils with low organic matter content are marginal in Zn. The Zn
deficiency is basically observed all over the country and the affected plants exhibit
Search WWH ::




Custom Search