Eco-Chronicle 59
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ECO-CHRONICLE 59 ECO CHRONICLE ISSN: 0973-4155 Vol. 12, No. 3, September, 2017 PP: 59 - 65 SPATIO-TEMPORAL VARIABILITY IN SOIL CHARACTERISTICS AND ITS INFLUENCE ON THE RETENTION OF CHLORPYRIPHOS AND QUINALPHOS IN CARDAMOM GROWING SOILS OF IDUKKI DISTRICT, KERALA Bindumol, G. P. and Harilal, C. C. Division of Environmental Science, Department of Botany, University of Calicut, Kerala. Corresponding author: [email protected] ABSTRACT A study was conducted for a period of one year to evaluate the zonal and seasonal variations in the physico-chemical characteristics of soil and their influence on the retention of pesticides like chlorpyriphos and quinalphos. Fifty four soil samples were collected from large and medium sized cardamom plantations falling in three zones of Cardamom Hill Reserve during pre-monsoon, monsoon and post-monsoon seasons and analysed for various physico-chemical properties and residues of chlorpyriphos (O, O-diethyl O-3, 5, 6- trichloro-2-pyridyl phosphorothioate) and quinalphos (O, O-diethyl O-quinoxalin-2-yl phosphorothioate) following standard methods. The extent of pesticide residues in the study area were then correlated with soil characteristics and meteorological data. Cardamom growing soils from the study area are of sandy clay loam type with acidic nature. Spatio-temporal variation was observed in the residues of chlorpyriphos and quinalphos. Seasonal variability was noticed in the concentration of pesticide residues and total phosphorus content, whereas it was not much reflected in organic matter content and cation exchange capacity of soil samples. Pesticide residues in soil were positively correlated with clay content in all seasons except monsoon. Soil organic matter has not found to have any influence on the retention of pesticide residues in soil. Low soil pH, high clay content and rainfall pattern has great influence in the persistence and leaching of pesticide residues in soils of the Cardamom Hill Reserve. Keywords: Chlorpyriphos, Quinalphos, total phosphorus, persistence. INTRODUCTION Kerala, the land of spices, surrounded by Western Ghats Major pesticide consuming crops in India are rice and in the east and Lakshadweep Sea in the west (between 80 cotton. Cardamom is not an exemption. Various chemicals to 120 N and 740 to 770 E) enjoys humid tropical climate. are frequently applied in cardamom plantations either as The major land forms are highland, midland and lowland, foliar spray or through soil drenching (George et al. 2013). each with its own geomorphic features. Idukki district of Among such chemicals, Chlorpyriphos is the widely used Kerala is famous for its scenic beauty and largest area organophosphorus insecticides in cardamom plantations. under forest cover. It is situated completely under Western Chlorpyriphos is used both by soil drenching and foliar Ghat region. The annual average rainfall is 3555.6 mm spray for the control of root grub and root borers. and temperature is 21.330C (Premachandran, 2007). The Quinalphos is yet another pesticide widely used for the district is popularly known as the spice district of Kerala, management of cardamom trips and other pests. owing to the cultivation of high yielding varieties of spices such as cardamom, pepper, turmeric, ginger etc. together On the basis of soil productivity and other factors governing with other plantation crops. All these crops demand the yield, cardamom hill reserve of the state of Kerala is divided usage of considerable quantity of chemicals for crop into three zones; zone A, B, and C. Zone A having highest protection and production. productivity, which includes Peerumedu Taluk excluding Peruvanthanam and Kokkayar villages and Chakkupallam, Synthetic pesticides have become one of the important Ayyappankovil and Vandenmedu villages of parts of integrated pest management for last few decades. Udumbanchola taluk. Zone B has comparatively lower A wide range of chemicals are being used in this category. productivity and includes Chathurangappara, Rajakkad, 60 ECO-CHRONICLE Santhanpara, Pampadumpara, Parathode and intervals during 2014-15 (figure.1). Soil samples were Udumbanchola villages of Udumbanchola taluk. The rest collected from root zone area of cardamom plants, of cardamom growing area comes under zone C (MSSRF, according to the cardamom package of practices of Spices 2008). Board, Cochin. Each soil sample has been collected from a 5acre plot, leaving 30 cm from plant base. Selected sites Pesticides, in addition to their activity on target organisms, for sampling were cleaned from weeds, dry leaves and will have multi-dimensional impacts on non-target other mulch materials. Soil was taken using a spade, after organisms. They may even persist in associated domains cutting and removing a V shaped hole at a depth of 15 cm like soil, water and air for a longer period of time. with the help of a spatula. Soil was scraped from both the Cardamom growing regions of Kerala have an undulating sides of V shaped pit in a thin layer of 2 cm along the terrain. Moreover they also form catchment basins of cutting of the full length (Jackson, 1973). From each 5 important rivers. Surveillance on the persistence and acre plot, 10 sub samples were collected diagonally and reactivity of applied chemicals is a major concern in most samples were gathered in a polythene sheet. It was then agro ecosystems. Hence a study has been undertaken to mixed well, removed all plant materials and spread in a assess the spatio-temporal variation in the physico- square shape in thin layer and sectioned to four quarters chemical characteristics of soils and to assess their impact by drawing diagonal lines. The two quarters falling on the retention of major pesticides such as chlorpyriphos opposite were discarded. The process was continued till and quinalphos in cardamom growing ecosystems. the sample become 500 g. From each sample, 10g was taken for the determination of moisture content. The soil MATERIALS AND METHODS sample thus collected from the field was dried under shade Soil samples were collected from cardamom plantations and sieved using 2mm sieve. The material on the sieve in zone A, B, and C, for a period of one year at bimonthly was again ground and sieved till all the aggregate particles were fine enough to pass through and only stones and organic matter remain on the sieve. The whole samples Figure 1. Cardamom cultivating areas in Idukki district were kept in plastic containers. Accordingly, three soil samples were collected from each zone at bimonthly interval for a period of one year. Altogether 54 soil samples Zone were collected. The samples were then analysed for soil C physical constants and texture (Clarson, 2002), chemical properties such as pH, electrical conductivity, organic matter content, cation exchange capacity and total phosphorus content (Jackson, 1973) and residues of chlorpyriphos and quinalphos following extraction (Kumari et al., 2008). The extracted pesticides were estimated Zone B using GC –FPD. Pesticide concentrations were measured using Shimadzu GLC 2014 equipped with Flame Photometric detector and Zone a RESTEK 30 m x 0.25 mm RTX -5 fused silica capillary A column with 0.25 µm film of phenyldimethylpolysiloxane. The injector was kept at 290 0C throughout the analysis within a split ratio of 1:10. The column head pressure of Table 1. Seasonal variation in soil physical properties of cardamom cultivating zones in Idukki. Zone pH Moisture content (%) Electrical conductivity (dS/cm) PRM M POM PRM M POM PRM M POM A 4.85 5.37 4.80 19.04 20.72 15.15 0.276 0.238 0.221 ±0.16 ±0.23 ±0.0 ±3.2 ±1.0 ±3.5 ±0.01 ±0.06 ±0.01 B 4.94 5.15 5.22 18.78 17.95 14.62 0.217 0.166 0.205 ±0.37 ±0.12 ±0.09 ±2.4 ±1.2 ±0.0 ±0.01 ±0.04 ±0.0 C 5.01 5.62 5.46 22.76 20.74 18.43 0.195 0.145 0.157 ±0.18 ±0.12 ±0.41 ±0.5 ±0.1 ±0.1 ±0.02 ±0.03 ±0.04 PRM - Pre Monsoon; M - Monsoon; POM - Post Monsoon ECO-CHRONICLE 61 carrier gas (nitrogen) was maintained at 169.7 kPa. The to May at an interval of 10 to 15 days until the onset of oven temperature was initially maintained at 200 0C for 1 monsoon. Since flowering season commences from min and then increased and held at 290 0C for 15 min. February onwards, irrigation is essential for flower setting Pesticide residues (µg g-1) in soil samples were calculated and yield setting. Hence most of the cardamom plantations as per George et al. (2013). are under irrigation. The soil moisture remains constant throughout the year due to constant irrigation practices. RESULTS AND DISCUSSION Organic matter content is a measure of soil health. Since The results of pH, moisture content and electrical cardamom plants grow under canopy, organic matter conductivity of soil samples are presented in Table 1. content in these plantations will be comparatively higher Seasonal changes in soil organic matter and cation than any other crop. The optimum soil organic carbon exchange capacity are given in Table 2 and those of bulk content for cardamom cultivation is 1.5 to 2.0 %, which density, particle density and water holding capacity in Table corresponds to 2.6 to 3.5 % of soil organic matter. The 3. Spatial variation in soil texture is depicted in Table 4. analytical data shows that all soil samples from the study site have high organic matter content. pH value of soils collected from the study area ranged from very acidic to near normal range (4.80 to 5.62). Soil Decomposition of organic matter is an integral part of any samples collected during pre-monsoon season showed natural process. Microbial decomposition of litter low pH compared to monsoon and post monsoon seasons.