Denis Magnus Ken Amara^1*, Sheikh Dyphan Abass Massaquoi² and Parameshgouda L Patil³  

1Department of Soil Science, School of Agriculture, Njala University, Njala Campus, Sierra Leone. 2Department of Agricultural Economics, School of Social Sciences, Njala University, Njala Campus, Sierra Leone. 3Department of Soil Science & Agricultural Chemistry, College of Agriculture, University of Agricultural Sciences, Dharwad, 580005, Karnataka, India.  

*Corresponding author. E-mail: E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.. Tel: +23279905400   

Received April, 2015; Accepted 20 May, 2015  

 

Knowledge of spatial variability in soil fertility is important for site specific nutrient management. In the present study, spatial variability in properties that influence soil fertility such as soil organic carbon, available N, available P2O5 and available K2O in 133 surface samples (comprising of 108 soil samples from red soils and 25 soil samples from black soils) from farmers' fields in Singhanhalli-Bogur microwatershed of Dharwad taluk in Dharwad district of Karnataka (India) were quantified. Based on the ratings of soil nutrients, the respective thematic maps (soil fertility maps) were prepared using Arc Map 10.1 with spatial analyst function of Arc GIS software through spline interpolation method. Soils were non-gravelly to gravelly with the red soils showing high gravel content (2.0 to 60.6%) than black soils (2.6 to 15.3%). The pH of the study area was slightly acidic to alkaline with normal electrical conductivity. The red soils were slightly acidic to alkaline with pH of 5.2 to 8.3 while the black soils were neutral to alkaline with pH of 6.4 to 8.6. The available N, P, K and S varied from low to medium, with majority of samples showing low values. The available Mn status of soils was sufficient (2.8 to 36.1 ppm for black soils and 0.2 to 88.7 ppm for red soils). The available iron was deficient to excess (0.5 to 7.1 ppm and 0.5 to 3.0 ppm for red and black soils, respectively), with majority of the samples deficient to sufficient in iron. Only 16.5 per cent of the study area was found to contain excess Fe. The available Zn and Cu was deficient to sufficient but major portion of the study area showed deficiency of available zinc and copper. The exchangeable Ca was moderate to high (3.2 to 28.6 cmol (p+) kg-1 and 8.6 to 35.8 cmol (p+) kg-1 for red and black soils respectively) but major portion of the study area was sufficient in exchangeable Ca while exchangeable Mg ranged from low to medium (1.9 to 16.5 cmol(p+) kg-1 and 6.0 to 23.2 cmol(p+) kg-1 for red and black soils respectively) . The observed spatial variability in various soil properties that influence soil fertility will help farmers in making crop management decisions that would help to increase crop productivity and improve farmers’ livelihood.  

Key words: Spatial variability, soil properties, India, remote sensing, geographic information system. 

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