) and to kg ha -1 (K 2

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1 Indian J. Agric. Res., 50 (5) 2016 : Print ISSN: / Online ISSN: X AGRICULTURAL RESEARCH COMMUNICATION CENTRE Soil nutrient status mapping of Nagenahalli micro-watershed under Eastern Dry Zone of Karnataka by remote sensing, detailed soil survey and GIS techniques C.N. Nalina 1, K.S. Anil Kumar* 2, M. Chandrakala 2, S. Sheela Rani, K. Sujata, K.G. Shilpa Shree, Rajendra Hegde 2 and S.K. Singh 3 Department of Soil Science and Agricultural Chemistry, UAS, GKVK, Bangalore , India. Received: Accepted: DOI: /ijare.v0iOF.3762 ABSTRACT Soil nutrients are essential for crop growth. Spatial variability of nutrients can occur in various scales, between regions, between fields or within the field. RS and GIS techniques enables farm management based on small-scale spatial variability of soil and crop parameters in the field. The present study was carried out in Nagenahalli microwatershed, Doddaballapur taluk, Bangalore rural district with the objective to determine and map the macronutrient status of soils in the watershed using GIS technique. The NPK was analyzed and mapped using Arc GIS to quantify the level of spatial nutrients availability. Results indicated that NPK ranged from to kg ha -1 (N), to kg ha -1 (P 2 ) and to kg ha -1 (K 2 O) respectively in the surface soils. Nutrient map showed that the soils were poor in available nitrogen and available potassium whereas sufficient in available phosphorous content. Furthermore NPK map can be used to identify deficient or sufficient areas for efficient fertilizer management. Key words: Detailed soil survey, Eastern dry zone, Nutrient status, Spatial variability. INTRODUCTION Overexploitation of productive lands with increasing population pressure creates serious problem of lowering the fertility status of soil and it leads to deterioration of soil. The deficiency of nutrients directly affects on the growth of crops and crop response become poor. Hence it is necessary to assess the fertility status of soil with the consideration of available nutrients in soils and to recommend the specific nutrients for the proper management of soil. Information on soil fertility status in crop field is very important and useful for fertilizer requirement and also to the specific management of the crop and soil. The availability of nitrogen, phosphorus and potassium (NPK), whether in soils or plants is among most of the nutrient studied for precision agriculture (Malek et al., 2007). Soil testing plays an important role in the use of fertilizers and other agricultural inputs. Soil test summaries and soil fertility maps are of vital necessity as reference materials for scientific management of soil. This information will also help to adopt effective strategy on fertilizer use and cropping pattern. Agroclimatic zones vary widely in their soils and their potentials, behaviour and response to management and soil based fertilizer recommendations should be preferred to achieve precision in farming and to maximise crop production, maintain soil health and minimise fertilizer misapplication (Ramamurthy et al., 2009) MATERIALS AND METHODS Nagenahalli is located between " N to " N latitude and " E to " E longitude covering an area of ha. in Doddaballapur taluk, Bangalore Rural district, representing Eastern Dry Zone in Karnataka. Extensive traverse of the village was carried out as the first step to identify field boundaries and to study external land features. Survey numbers given in the cadastral map were identified in the field. A total of 50 surface samples were collected plot wise according to survey numbers (GPS based) for laboratory analysis. Using base maps, google earth images, satellite imagery and toposheets, physiographic delineations were marked in the study area. Traversing was done to confirm the delineations and main physiographic units of the study area were identified. Soil profiles were excavated representing each identified *Corresponding author s anilsoils@yahoo.co.in 1 Department of Soil Science and Agricultural Chemistry, UAS,GKVK, Bangalore ICAR-National Bureau of Soil Survey and Land Use Planning, Hebbal, Bangalore ICAR-National Bureau of Soil Survey and Land Use Planning, Amravati Road,University P.O. Nagpur

2 390 INDIAN JOURNAL OF AGRICULTURAL RESEARCH physiographic unit in transects. Horizon-wise soil samples from each pedon depth-wise were also collected and analysed. Soil samples were analyzed using standard procedures for the status of available nitrogen (Subbaiah and Asija, 1956), available phosphorus (Bray and Kurtz, 1945; Watanabe and Olsen, 1965), available potassium (Jackson, 1973). Soil fertility maps showing plot wise status of available major nutrients were prepared in GIS environment to know the fertility status of the soils of study area. GIS processing involved geo-referencing of various thematic maps and vectorisation of the features using Arc GIS software. Simultaneously the attribute coding and the description for all feature classes were organized in master database tables. The topography was created and the master database was linked to respective themes. All the features were referenced with the standard codes. The soil, land use and watershed themes were built as polygon features, whereas streams and roads were built as line features. The water resources include line features as well as point features and these were included as shape files. RESULTS AND DISCUSSION Soil reaction: Soil ph varied from very strongly acid to moderately alkaline. The ph was increasing with depth in all the pedons (Table 2). Similar result was recorded by Walia and Rao (1997) in red soil. It might be attributed to intense leaching of bases throughout the profile. Lower ph in the surface was recorded in the pedon 2 (4.7), heavy leaching of bases in the gentle slope might have contributed for the low ph in the pedon. Pedon-4 and pedon-5 located in nearly level land recorded higher ph than the pedons located in slopes. Surface soil reaction of plots of Nagenahalli (Table 3) revealed that 9.9 per cent very strongly acidic, 24.7 per cent strongly acidic, 33.2 per cent of area were moderately acidic, 9 per cent are slightly acidic in reaction followed by 12.2 per cent neutral and 1.9 per cent moderately alkaline. Most of the soils are acidic in reaction leaching of bases in the gentle slope might have contributed for the lower ph. Available nitrogen: The available nitrogen status was low in almost all the pedons (Table 2). It ranged from to kg/ha. Pedon-1 recorded highest nitrogen range and highest was recorded in the surface horizon as the land is under cultivation. Application of fertilizers and manures might have increased the N-content. Pedon-2 recorded the minimum variation in its nitrogen content. It was kg/ ha in surface horizons and increased to kg/ha in Bt4 horizon. Through this area was affected by erosion, following of conservation practices (Eucalytus plantations) in the recent years was resulted in growth of grasses and other vegetation and increased the level of organic matter accumulation (Rajan, 2008). Pedon-4 located in the ploughed land recorded the nitrogen content in the range of to 282 kg/ha. Pedon-5 showed increasing trend with depth. The land is not under cultivation at present though it was cultivated earlier, leaving the land as fallow for many years led to the leaching of nitrogen from surface to the lower layers (Rajan, 2008). The spatial variability of macronutrients (NPK) in the study area is shown in Table 1, Fig 1. Available nitrogen status of the surface soils studied revealed that 75.7 per cent of the surface soils studied was very low, while 13.2 per cent of the soils studied were low and 2.1 per cent of the soils studied were medium in available nitrogen status (Table 4 and Fig 2). The soils were poor in available nitrogen, range from 31.4 to kg/ha. Semi-arid environment with low rainfall and low organic carbon status of the soils are contributing towards very low or low available nitrogen status of the soils, confirming the study of Anil Kumar et.al. (2002). Available phosphorus: Available phosphorus of soil pedons varied from 2.6 to kg/ha (Table 2). Pedon-1 recorded high available P the value was decreasing with depth. The land is under intensive cultivation with maize and ragi crops. Further fertilizers and manures were added every year during cultivation. This might be the reason for the accumulation of available phosphorus in the surface horizon. Similar trend was observed in Pedon-4, but the content of available phosphorus was less compared to pedon-1. Low amount of available phosphorus was observed in pedon-2, pedon-3 and pedon-5, which are not under cultivation during the current year. In surface soils most of the areas have sufficient available phosphorous (21.3 to kg/ha) recording high to very high phosphorus content (Table 1). Available phosphorus status of the surface soil studied revealed that 75.6 per cent of the surface soil studied was very high. While 12.0 per cent of the soils were high, 3.30 percent of the soils were medium in available phosphorus status (Table 5 and Fig 3). Semi-arid environment with low rainfall, the continuous use of high analysis fertilizers especially SSP in the study area resulting in the phosphorus build up and contributing towards high available phosphorus status of the soils. Anil Kumar et al.(2002) also found similar observations. Available potassium: The available potassium of pedons ranged from 73.2 to kg/ha (Table 2). The available potassium values are higher in surface horizons of pedon-1

3 Volume 50 Issue 5 (2016) 391 Table 1: Major nutrient status of surface soils of the study area Sl. No. Survey No. ph Macronutrients Sl. No. Survey No. ph Macronutrients N P 2 K 2 O N P 2 K 2 O 1 Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Ngh Min Min Max Max Mean Mean SD SD

4 392 INDIAN JOURNAL OF AGRICULTURAL RESEARCH Table 2: Major nutrient status of soil pedons of the study area Depth (cm) Horizon Major available nutrients (Kg ha -1 ) ph N P 2 K 2 O Pedon Ap Bt Bt Bt Bt4C Bt5C Bt6C Pedon A Bt Bt Bt Bt Bt Pedon Ap Bt Bt CB CB CB Pedon Ap Bt Bt Bt3C Bt4C Bt5C Pedon Ap Bt Bt Bt Bt Table 3: Surface soil reaction classes in the study area Classes Soil reaction Area (%) Very strongly acid Strongly acid Moderately acid Slightly acid Neutral Moderately alkaline Miscellaneous 9.0 Total Table 4: Classification of available nitrogen in the study area Classes N (Kg/ha) Area (%) Very low < Low Medium Miscellaneous 9.00 Total Table 5: Classification of available phosphorus in the study area Classes P 2 (Kg/ha) Area (%) Medium High Very high > Miscellaneous 9.00 Total (133.7 kg/ha) and pedon -4 (165.9 kg/ha) might be due the intensive root growth supplemented with potassic fertilizers. Pedon-2, pedon-3 and pedon-5 showed increased potassium content with depth may be due to leaching and accumulation from surface to lower layers under uncultivated situation. The study of surface soils revealed that about ha area was low in K content, the content of potassium was varied from 55.1 to kg/ha (Table 1). The study revealed that 10.6 per cent of the surface soils studied were very low

5 Volume 50 Issue 5 (2016) 393 Fig 1: Location map of the study area in Doddaballapur taluk, Bangalore Rural District. in available potassium, while 69.9 percent of the soils were low, 11.1 per cent of the soils were medium and only 1.3 percent of the soils studied were high in available potassium (Table 6 and Fig 4). Semi-arid environment with low rainfall and intensive agriculture with maize and vegetable crops may be the reason to decline in fertility. Anil Kumar et al. Table 6: Classification of available potassium in the study area Classes K 2 O (Kg/ha) Area (%) Very low < Low Medium High > Miscellaneous 9.00 Total (2002) also found similar results. Sustainable management of water, soil and sediment resources at the catchment level is a key to integrated nutrient management as well as urbanrural balance (Gunnel and Krishnamurthy, 2003) as loss of nitrogen and potassium rich top soil due to sheet erosion and its siltation in viable tank beds is rampant in eastern dry zone of peninsular India. CONCLUSIONS Very low to low status of available nitrogen, very high to high available phosphorus and low to medium available potassium indicates that the soils are poor in plant available nutrients. Fertilizer sources were urea for nitrogen, single super phosphate for phosphorus and muriate of potash for potassium. Frequent use of imbalanced chemica l

6 394 INDIAN JOURNAL OF AGRICULTURAL RESEARCH Fig 2: Available Nitrogen Status (Plot wise) of Nagenahalli Village Very low class is included to depict the severity of fertility problem

7 Volume 50 Issue 5 (2016) 395 Fig 3: Available Phosphorous Status (Plot wise) of Nagenahalli Village Very high class is included to depict the intensity of high availability

8 396 INDIAN JOURNAL OF AGRICULTURAL RESEARCH Fig 4: Available Potassium Status (Plot wise) of Nagenahalli Village Very low class is included to depict the severity of fertility problem

9 Volume 50 Issue 5 (2016) 397 fertilizers to soil without addition of organic inputs may be the reason to steady decline in organic carbon status, available nitrogen and potassium levels but phenomenal increase in available phosphorus levels and acidification of surface as well as sub-soils. Application of organic manures, nitrogen and potassic fertilizers on site specific recommended dosage within the required areas with periodic skipping of phosphorus fertilizers can improve the soil quality and nutrient status thereby increased crop productivity. The information thus generated can be used for issue of soil health cards and the maps can be used to arrive at meaningful and workable land management practices and alternative land use plans for the village for sustainable agriculture. REFERENCES Anil Kumar, K.S., Characterization, classification and suitability evaluation of coffee-growing soils of Karnataka. P. hd. (Agri.) thesis submitted to UAS, Bangalore. Bray, R.H. and Kurtz, L.T., Determination of total, organic and available forms of phosphorous in soils. Soil Sci., 59: Gunnel, Yanni and Krishnamurthy, Anupama, Past and present status of runoff harvesting systems in dryland Peninsular India: A critical review, Royal Swedish Academy of Sciences Ambio Vol. 32: Jackson, M.L., Soil Chemical Analysis. Prentice Hall of India (pvt) Ltd., New Delhi. Malek, M.Y, Kamaruzaman, J. and Mohd, H. I., Soil nutrient variability mapping inuitm research station, Arau, Perlis Using Landsat TM7 and Geostatistical analysis, WSES Transaction on SignalProcessing. Greece., 502: Rajan, K., Impact of erosion and salinity on soil and land quality indicators in southern Karnataka. Ph.D. (Agri.) thesis submitted to UAS, Bangalore. Ramamurthy, V., Naidu, L.G.K., Ramesh Kumar, S.C., Srinivas, S., Hegde, Rajendra, Soil-based fertilizer recommendations for precision farming, Curr. Sci. 97: Subbaih B.V. and Asija, G.L A rapid procedure for the determination of available nitrogen in soils. Curr. Sci. 25: Walia, C. S. and Rao, Y. S., Genesis, Characterisitation and taxonomic classification of some red soils of Bundelkhand region of UP. J. Indian Soc. Soil Sci., 44: Watanabe, F.S. and Olsen, S.R., Test of ascorbic acid methods for determining phosphorous in water and sodium bicabbonate extracts of soil. Soil Sci. Soc. Am. Proc., 29: