Abstract: Tea growers who have large area under tea find it difficult to manage land fertility solely with summary soil test reports and maps would be an ideal tool for them. Unlike ordinary maps, Geographic Information System (GIS) can manage large collection of land resources data necessary for tea production. The data on primary nutrients status and organic matter content are important for maintaining sustainable productivity. The Anamallais (Coimbatore District) has the second largest area under tea in Tamil Nadu, next only to the Nilgiris. The soil samples were analysed for pH, organic matter, phosphorus and potassium and the results were categorised in to low, medium and high. Digitized maps were prepared for individual tea estates using the Arc MAP software. It is indicated that fields having pH more than 5.5 may require measures to reduce the pH to the desired level. A few fields had low pH, which warranted application of dolomitic lime. Majority of the tea fields fell under the high category of available phosphorus content, because of the present practice of broadcasting of rock phosphate along with NK. Most of the tea fields were of medium category in potassium content, because the latosol tea soils easily release exchangeable potassium to available form of potassium. The fields at higher elevation have high organic matter content. Fields with low organic matter content needed improvement through external application of organic manures. The fields situated near forest area had high organic matter status The study revealed that 2% of the samples were under low and high categories each while the remaining 96% of the samples belonged to medium category.
INTRODUCTION
Optimal utilisation of soil resources is necessary maintain sustained productivity of soils over a long period of time. Information on soil resources relating to their spatial extent, variability, availability and usage of nutrients are required for optimum utilisation. Development of technology like Geographical Information System (GIS) is providing valuable support to handle voluminous data being generated through conventional and spatial format and for the integration of these data sets (Rao, 2007; Vadivelu, 2007).
In Tamil Nadu, Anamallais has the second largest area of tea, next only to the Nilgiris. The elevation of this range of hills varies from 900 to 1200 m above mean sea level. The weather, soil and lay of the land are extremely favorable for the cultivation of tea. The annual rainfall ranges from 2000 to 6000 mm and annual tea production is around 32 million kg. For the purpose of this study Anamallais region was divided into three agro climatic areas namely Eastern facing, Western facing and Intermediate.
Tea growers who have larger area under tea, find it difficult to manage soil fertility solely with summary soil test reports and maps would be an ideal tool for them. However, the change in soil fertility status over a period of two or three years makes the paper maps invalid. The GIS technique uses a digital map which allows the users to view, update, query, analyse and manipulate the spatial and tabular data either alone or together, within a few minutes. Unlike paper maps, GIS can manage large collection of land resource data necessary for tea production. The soil available nutrients and organic matter status are important for sustainable productivity. The variations occurring in these parameters will cause remarkable changes in soil fertility and affect the yield levels of tea. Continued use of nitrogenous fertilisers and high rainfall (>3000 mm year-1) make the soil more acidic. However, the information available on GIS technique in tea is very much limited particularly in south India, while there are many studies using GIS on cultivation practices of various other crops (Deosthali et al., 2005; Rao et al., 1995; Osborne et al., 2002; Adams et al., 2000; Rao, 2007). The present study was aimed to create digitized maps of the tea estates of the Anamallais from the existing paper maps and documents. An attempt was also made to create the status maps of tea soils of the Anamallais on pH, potassium, phosphorus and organic matter, which would be beneficial to the tea growers for calculating the fertiliser requirements.
MATERIALS AND METHODS
Soil Sampling
Composite soil samples were collected using sampling auger, from each field
of the selected estate, at the rate of one sample per hectare. The individual
soil samples collected from a particular field were mixed together by hand on
a polythene sheet. The bulk quantity of the collected samples was reduced to
1/3 of its volume by quartering method. The samples were air dried and passed
through 2 mm sieve. The experiment was conducted during 2008 and 2009.
Digitizing Process
Soil samples were collected from 0-22.5 cm depth and GPS (Global Positioning
System) coordinates of the sampling points were recorded using a GARMIN GPS
Map 60 instrument. In each estate, 10 to 15 geo-coordinate points like estate
boundary, division boundary, factory, estate corner, swamp, road junction, leaf
shed, muster, school, temple, manager’s bungalow, office and other important
land marks, if any, were shown on the map. These geo-coordinates were used to
digitize the maps. Initially all the minute geo-coordinates were subjected to
degree conversion for uniform universal unit and then all the maps were geo-coordinated
using R2V software. Each layer of individual estates like estate boundary, division
boundary, buildings, contour lines and government road lines were traced with
Easy Trace software 7.4 version and all the layers were merged and digitized
using Arc Map software.
Physico-Chemical Analysis
The soil characteristics of the Anamallais site are given in Table
1. Soil pH was determined in 1: 2 soil : water mixture using Orion pH meter
(Orion, 950) as per Schofield and Taylor (1955), electrical
conductivity was measured using conductivity meter (Systronics, 304) following
the method given by Mason and Obenshain (1939), organic
matter by Wakley and Black (1934) procedure, available
P by Bray and Kurtz (1945) method, K as per Hanway
and Heidal (1952) and soil particle distribution (sand, silt and clay) by
international pipette method (Baver et al., 1972).
| Table 1: | Physico-chemical properties of Anamallais soils |
| EC: Electrical conductivity, OM: Organic matter | |
Nutrient Status
The soil test results of the tea estates of the Anamallais were classified
into low, medium and high category (Verma and Palani, 1997).
The soil pH was classified in to; < 4.5 : Low; 4.5-5.5: Medium and >5.5:
high, the organic matter of tea soils was classified as; <2.6%: Low; 2.6-7.8%
Medium and >7.8% : High, potassium status as follows; <100 ppm: Low; 100-300
ppm: Medium and >300 ppm: High and phosphorus status as; <4.4 ppm: Low;
4.4-21.0 ppm: Medium; 22.0-44.0 ppm : High and >44 ppm: Very high.
RESULTS AND DISCUSSION
Physico Chemical Properties of Tea Soils in Anamallais
The soils of different zones in Anamallais showed differences in their physical
and chemical properties (Table 1), which justified the need
for a separate study at different locations of Anamallais. The geographical
location of certain estates in Anamallais is provided in Table
2.
Soil pH
The ideal soil pH for growing tea is between 4.5 and 5.5. The results indicated
that pH status of most of the fields fell under the ideal category while some
of them had slightly higher pH. The fields with pH more than 5.5 required aluminium
sulphate application to reduce the pH to desired level (Table
3). The soil pH was low in a few fields which warranted application of dolomitic
lime. The nutrient uptake is optimum only when the soil pH is between 4.5 and
5.5 (Verma and Palani, 1997). About 17% of the soils from
tea estates were under low category, 78% under medium (or) ideal category and
the remaining samples had high pH.
Phosphorus
Majority of the tea fields fell under high category of available phosphorus
content, because of the regular application of rock phosphate with citric acid
along with NK broadcasting as recommended in the recent past (Venkatesan,
2006). A few fields fell under the low category of P status indicating the
need for application of phosphorus through soil (Table 4).
| Table 2: | Geographical location of certain estates under tea cultivation in the Anamallais |
| Table 3: | Soil pH and Organic matter status of certain estates under tea cultivation in the Anamallais |
| pH status: <4.5-Low; 4.5-5.5: Ideal; >5.5-High, Organic Matter Status: 0-2.6 (%): Low; 2.6-7.8 (%): Medium; >7.8 (%): High for 500-1500 m above MSL | |
| Table 4: | Soil potassium and phosphorus status of certain estates under tea cultivation in the Anamallais |
| Potassium status: 0-100 ppm: Low; 100-300 ppm: Medium and >301 ppm: High. Phosphorus status: 0.0-4.4 ppm: Low; 4.4-21.0 ppm: Medium; 22.0-44.0 ppm: High and >44: Very high. | |
About 2% of the soils were under low category, 13% samples fell under the medium category, 24% of under high category and the remaining 61% samples were under very high P category.
Potassium
The tea soils are highly weathered with kaolinite as predominant clay mineral,
where there is hardly any binding site for potassium. Hence, it is necessary
to apply potassium fertiliser frequently. Certain fields belonged low potassium
category, which required immediate attention for the application of NK fertilizer.
Most of the tea fields had potassium content in medium category and few fields
were of low and high category (Table 4). Since south Indian
tea soils are laterite, most of the applied potassium was in available pool
which could be the main reason for most of the fields coming under medium potassium
category (Venkatesan and Senthurpandian, 2006). About
2% of the soils were under low category, 80% samples fell under the medium (or)
ideal category and the remaining 18% of the samples were under high category.
Organic Matter Status
The variations occurring soil available micro nutrient and organic carbon
will cause remarkable changes in soil fertility and affect the yield levels
of tea. Most of the tea fields were at medium organic matter content and a few
fields were in high category. The higher elevation fields had high organic matter
content. Similar observation on high elevation fields were made by Verma
and Venkatesan (2001), Deosthali et al. (2005)
and Rao et al. (1995). The organic matter content
was low in some of the fields which indicated the need for the improvement of
organic matter through external application of organic manure. Organic matter
content was higher in the fields nearer to forest area (Table
3). This study revealed that 2% of the fields were under low and high categories
each while the remaining 96% of the samples fell under the medium category (Table
3).
CONCLUSION
This study revealed that most of the soils of Anamallais have ideal pH range suitable for growing tea and the nutrient contents were in medium and high category. This work proved the feasibility of using GIS as a technique to study the nutrient status of individual fields to arrive at specific requirements for external application of nutrients. This study assumes significance in view of the possibility to update the data based on the exact soil test value once in three to four years. Although current study has dealt with only pH, P, K and OM status, it can be taken as a model for studying the status of other nutrients.
ACKNOWLEDGMENTS
The authors are grateful to Dr. P. Mohankumar, Director, UPASI Tea Research Foundation for providing the facilities. The authors also wish to express their sincere thanks to Dr. S. Vadivelu and Dr. L.G.K. Naidu Head and Mrs K.V Archana Regional Centre, Hebbal, National Bureau of Soil Survey and Land Use Planning, Bangalore for their help in digitizing the maps. The financial assistance provided by the Department of Science and Technology (DST), New Delhi is gratefully acknowledged.