Mapping of nutrient status of rice soils in Visakhapatnam district using GIS techniques

An Asian Journal of Soil Science Volume 8 Issue 2 December, 2013 Research Article Mapping of nutrient status of rice soils in Visakhapatnam district using GIS techniques Y. SUDHA RANI, G. JAYASREE AND M.V.R. SESHA SAI Received : 23.08.2013; Revised : 25.09.2013; Accepted : 05.10.2013 MEMBERS OF RESEARCH FORUM : Summary Corresponding author : A study was undertaken to map the nutrient status of rice growing soils of Visakhapatnam district of Andhra Y. SUDHA RANI, Department of Soil Pradesh. Spatial distribution of nitrogen, phosphorus, potassium and organic carbon was studied by collecting Science and Agricultural Chemistry, geo-referenced surface (1-15 cm) and sub surface (15-30 cm) samples from 69 sites representing intensively Acharya N.G. Ranga Agricultural rice growing soils using global positioning system (GPS) and mapped in GIS environment. These samples University, HYDERABAD (A.P.) INDIA were analyzed for physical, physico-chemical and chemical properties of the soils. The content of available Email: sudhayarramasu@gmail.com nitrogen varied from 125 to 392 kg ha -1, available P from 9.0 to 39.0 kg ha -1, available K from 98 to 420 kg ha -1 and organic carbon varied from low to medium. The maps of various nutrient elements clearly indicated Co-authors : the specific locations, where deficiency of nutrients constrained crop production. G. JAYASREE, Department of Soil Science and Agricultural Chemistry, Key words : Soil fertility, Mapping, Spatial variability, Geographic information system Acharya N.G. Ranga Agricultural University, How to cite this article : Rani, Y. Sudha, Jayasree, G. and Sai, M.V.R. Sesha (2013). Mapping of nutrient status of rice HYDERABAD (A.P.) INDIA soils in Visakhapatnam district using GIS techniques. Asian J. Soil Sci., 8(2):. M.V.R. SESHA SAI, National Remote Sensing Centre, Balanagar, HYDERABAD (A.P.) INDIA Introduction Rice crop requires application of heavy doses of nutrients, particularly nitrogen (N), to achieve full yield potential. Application of fertilizers by the farmers in the fields without prior knowledge of soil fertility status might result in adverse effects on soils as well as crops both in terms of nutrient deficiency and toxicity either by the adequate or over use of fertilizers (Sharma, 2004). A scant attention was paid to collect the geo-referenced samples and whole district was taken as a single mapping unit. With the invent of modern technologies of remote sensing, GIS and GPS, it is now possible to monitor the changes in fertility status of the study area with site-specific nutrient requirement of the crop. Keeping this in view, present study was taken up in Visakhapatnam district of Andhra Pradesh to study the spatial distribution of soil nutrients. Resource and Research Methods In Visakhapatnam district, rice is cultivated in 97000 ha with a total production of 1.46 lakh tons and productivity of 1494 kg/ha. Surface soil samples from 0-15 cm and sub surface soil samples from 15-30 cm depth were drawn from the ground truth sites from rice growing areas. Sixty nine geo-referenced soil samples were collected and location of soil sampling sites of the district were worked out with the help of global positioning system (GPS) used during collection of soil samples. The soil samples were ground and passed through a 2 mm sieve. Soil ph was measured in 1:2.5 soil water suspension using glass electrode ph meter. Particle size analysis by bouyoucos hydrometer method, cation exchange capacity (CEC) was determined by using neutral sodium acetate and organic carbon by rapid titration method (Walkley and Black, 1934). The available nitrogen was estimated by alkaline permanganate method of Subbiah and Asija (1956). Available phosphorus was extracted with 0.5M NaHCO3 solution buffered at ph 8.5 (Olsen et al., 1954). Phosphorus in the extract was determined by developing blue colour using ascorbic acid method (Watanabe and Olsen, 1965). Available potassium (K) was extracted by shaking the requisite amount HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE

Y. SUDHA RANI, G. JAYASREE AND M.V.R. SESHA SAI of soil sample with 1N NH 4 OAc (ph 7.0) solution (1:5 soil solution ratio) (Pratt, 1982). The soil samples were collected based on the type of the soil, and the method of growing of rice (transplanted or rainfed) and drawn from 15 mandals of rice growing regions in Visakhapatnam district (Fig. A). 20 Fig. A : 10 0 Kharif rice Spatial distribution of rice crop in Visakhapatnam district The soils samples were taken using GPS to mark the location of samples. These point locations are fed into categories based on criteria given in Table A. The points having same category were grouped into class as a polygon and the maps for individual nutrients were generated in Arc GIS. Even though map showing the entire district, the area was calculated for rice growing areas using rice mask of the district. Table A: Criteria for assessment of organic carbon and macronutrients in soils (Tandon, 1993) Parameter Low Medium High Organic carbon (per cent) <0.5 0.5-0.75 >0.75 Available nitrogen (kg ha -1 ) <280 280-560 >560 Available phosphorus (kg ha -1 ) <22.5 22.5-56 >56.0 Available potassium (kg ha -1 ) <135 135-335 >335 Research Findings and Discussion The texture of the surface soils varied from sandy loams to clay. More than 51per cent of the soils were sandy clay loam in nature and 39 per cent of the soils were clayey in nature. The clay content varied from 11.0 to 56.0 per cent with a mean value of 30.1 per cent while the sand fraction varied from 25.0 to 79.0 per cent with a mean value of 53.7 per cent (Table 1). The silt content of these soils varied from 5.0 to 30.0 per cent with a mean value of 15.8 per cent. The texture of the subsurface soils varied from sandy clay loam to clay in nature. As the depth of the soil increases, the per cent of clay increased, the sand content decreased and silt content did not follow with depth. The clay content of subsurface soils varied from 13.0 to 50.0 per cent with a mean value of 34.6 and standard deviation of 9.7. The sand fraction varied from 23.0 to 78.0 per cent with a mean value of 46.2 with a standard deviation of 12.9. The silt content of these soils varied from 6.0 to 35.0 per cent with a mean value of 19.4 and a standard deviation of 6.5. Increase in clay content with depth might be due to more intensive weathering at deeper layer and impoverishment of finer particles from surface horizon leaving behind coarse sand particles in surface layers. The variation in texture was mainly because of deposition of finer fraction. Similarly, the illuviation process also affected the vertical distribution of silt and sand content. Similar observations were also made by Sharma (2004). The results of soil reaction revealed that the surface soils under study fall under slightly acidic to alkaline in range (Table 1). The ph of soils under the study varied from 5.0 to 8.7 with a mean value of 6.8 and standard deviation of 1.04. The soil reaction of subsurface soils was ranged from 5.0 to 8.5 with a mean value of 7.0. Majority of the soils had slightly acidic to alkaline ph with an average ph of 6.8 which is ideally suited for cultivation of wide range of crops with no limitation. The soils are slightly acidic to alkaline ph may be attributed to the reaction of applied fertilizer material with soil colloids, which resulted in the retention of basic cations on the exchangeable complex of the soil. Sharma et al. (2008) and Madhuvani et al. (2000) also reported the similar results. The alkaline ph values in surface and subsurface soils might be due to efficient recycling of basic cations and also due to presence of sodium as dominant cation on exchangeable complex (Prasad et al., 1998). The variation in soil ph was related to parent material, rainfall and topography. Similar results were reported by Thangasamy et al. (2005). Electrical conductivity of the surface and subsurface soils are non saline (Table 1). The electrical conductivity of the soil samples was increased with depth. The slight increase in EC values in subsurface soils, might be due to high soluble salt content with depth due to translocation of soluble salts from surface horizons to deeper layers. The normal EC may be ascribed to leaching of salts to lower horizon (Sharma et al., 2008). Similar results were reported by Sahu et al. (1990). The results of the organic carbon revealed that the soils under study fall under low to high. The organic carbon content of the surface soils varied from 1.0 to 8.9 mg kg -1 with a mean value of 4.27 mg kg -1 (Table 1). The organic carbon content of subsurface soils was low and varied from 0.4 to 5.1 per cent with a mean value of 2.2 mg kg -1 and standard deviation of 1.03. For presentation purpose, rice growing soils were mapped in Arc GIS. The variations in organic carbon status was mapped under GIS environment (Fig. 1). It is observed that, the soils in district are low in organic carbon content (Table 2). The organic carbon content of surface soil was greater than sub surface soils. This was attributed to the addition of organic manures and plant residues to surface soils which resulted in higher organic carbon content in HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 326 Asian J. Soil Sci., (Dec., 2013) 8 (2) :

MAPPING OF NUTRIENT STATUS OF RICE SOILS IN VISAKHAPATNAM USING GIS TECHNIQUES surface horizons than subsurface soils. These observations are in accordance with results of Basavaraju et al. (2005). low in respect of their available nitrogen. The entire area was classified with low nitrogen level was may be due to type of soil where the water holding capacity of the soil was less and run off losses were more. Nitrogen is the most limiting nutrient and is dependent on temperature and rainfall. The loss of nitrogen is mainly due to various mechanisms like mineralization of organic nitrogen, nitrification of ammonia originating from both native and fertilizer sources, denitrification, immobilization and leaching (Dasog et al., 2006). Fig. 1: 20 10 0 Low <5.0 g kg -1 Medium 5.0 7.5 g kg -1 Spatial distribution of organic carbon (g kg -1 ) content in surface soils of rice growing regions in Visakhapatnam district The results of the available nitrogen revealed that the surface soils under study fell under low to medium range. The available nitrogen in the soils varied from 125 to 392 kg ha -1, with a mean value of 226 kg ha -1 (Table 1). The available nitrogen in irrigated soils varied from 125 to 392 kg ha -1, with a mean value of 239 kg ha -1 and standard deviation of 61.8 (Table 1). The available nitrogen content of subsurface soils decreased with increase in depth. The available nitrogen content of the subsurface soils varied from 79 to 289 kg ha -1, with a mean value of 148 kg ha -1. The variations in nitrogen status were mapped under GIS environment. For presentation purpose, low level was further categorized into 3 levels for map presentation (Fig. 2). Since organic matter contents is an indicator of available nitrogen status of soils, thus the soils of the area are also dominantly 20 10 0 <212 kg/ha 212-240 kg/ha 240-285 kg/ha Fig. 2: Spatial distribution of available nitrogen (kg ha -1 ) in surface soils of rice growing regions in Visakhapatnam district The results revealed that the phosphorus status of surface soils (Table 1) under study was low to medium and Table 1: Physico-chemical and chemical characteristics soils of Visakhapatnam district Surface soil Sub surface soil Min. Max. Mean SD Min. Max. Mean SD ph (1:2.5) 5.0 8.7 6.8 1.04 5.0 8.5 7.0 1.04 EC(dS m -1 ) 0.03 0.9 0.26 0.17 0.03 1.12 0.2 0.18 Organic carbon (per cent) 1.0 8.9 4.27 1.74 0.4 5.1 2.2 1.03 Sand (per cent) 25 79 53.7 13.5 23 78 46.2 12.9 Silt (per cent) 5 30 15.8 5.4 6.0 35.0 19.4 6.5 Clay (per cent) 11 56 30.1 10.3 13 50 34.6 9.7 Available nitrogen (kg ha -1 ) 125 392 226 61.8 79.0 289 148 50.4 Available phosphorus (kg ha -1 ) 9.0 39.0 20.8 8.33 5.0 32.8 14.7 7.7 Available potassium (kg ha -1 ) 98 420 230 87.8 56 309 164 79.5 CEC (c mol (p+) kg -1 ) 1.26 40.5 8.9 9.9 7.0 41.0 20.9 8.4 HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 327 Asian J. Soil Sci., (Dec., 2013) 8 (2) :

Y. SUDHA RANI, G. JAYASREE AND M.V.R. SESHA SAI the values ranged from 9.0 to 39.0 kg ha -1, with a mean value of 20.8 kg ha -1 with standard deviation of 8.33. The variations in phosphorus were mapped under GIS environment (Fig. 3). Most of the soils (58 %) fell under low in available phosphorus content. The available phosphorus status in subsurface soils ranged from 5.0 to 32.8 kg ha -1 with a mean value of 14.7 kg ha -1 (Table 1). Majority of subsurface soils were low in available P. Due to acidic nature of the soil reaction, the availability of phosphorus was less (Dasog et al., 2006). Fig. 4 : Spatial distribution of available potassium (K 2 O) content in surface soils of rice growing regions in Visakhapatnam district (kg ha -1 ) Fig. 3 : 20 10 0 Available phosphorus Low <22.5 kg ha -1 Medium 22.5 56.0 kg ha -1 Spatial distribution of available phosphorus (P 2 O 5 ) content in surface soils of rice growing regions in Visakhapatnam district (kg ha -1 ) The available potassium in surface soils varied from 98 to 420 kg ha -1, with a mean value of 230 kg ha -1 (Table 1). Majority of soils were medium in available potassium. The variations in potassium were mapped under GIS environment (Fig. 4). There was decrease in available potassium with increasing depth. The available potassium in subsurface soils ranged from 56 to 309 kg ha -1 with a mean value of 164. The standard deviation of 79.5 showed variability of this nutrient. Adequate available K in these soils may be attributed to the prevalence of potassium rich minerals like illite and feldspars (Sharma et al., 2008). Black soils shown high values due to predominance of K rich micaceous and feldspars minerals in parent material. Similar results were observed by Ravi Kumar (2006). The results revealed that the cation exchange capacity of surface soils under the study were in a range of 1.26 to 40.5 c mol (p + ) kg -1 and 7.0 to 41.0 c mol (p + ) kg -1 soil in surface and subsurface soils, respectively. The CEC content of the subsurface soils varied from 7.0 to 41.0 c mol (p + ) kg -1 soil, with a mean value of 20.9 and standard deviation of 8.4. The increasing trend in CEC with depth was due to increased clay content in deeper layers besides higher accumulation of fine clay in deeper layers. Similar results were reported by Gangopadhyay et al. (1998) and Mandal et al. (2003). Conclusion : The generation of soil properties maps by GIS technique depicts their spatial variability and provide a strong base for site-specific nutrient management to optimize crop production and input use efficiency. The results of the study are of potential practical use in determining site specific nutrient management practices, that would help in improving fertilizer use efficiency, reducing cost of cultivation and preventing environmental pollution. The deficient nutrients have to be restored through chemical fertilizers and/or organic manures to maintain soil health. For efficient and sustainable crop production in these soils, a farming system that is both soil enriching and restoring needs to be developed. Literature Cited Basava Raju, D., Naidu, M.V.S., Ramavatharam, N., Venkaiah, K., Rama Rao, G. and Reddy, K.S. (2005). Characterization, classification and evaluation of soils in Chandragirimandal of Chittoor district, Andhra Pradesh. Agropedology, 15 : 55 62. Gangopadhyay, S.K., Walia, C.S., Chamuah, G.S. and Baruah, U. (1998). Rice growing soils of upper Brahmaputra valley of Assam their characteristics and suitability. J. Indian Soc. Soil Sci., 46 : 103-109. HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 328 Asian J. Soil Sci., (Dec., 2013) 8 (2) :

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