AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com/www.legumeresearch.in LR-3957 [1-6] *Corresponding author’s e-mail: sunitamahapatra@yahoo.co.in Legume Research, Print ISSN:0250-5371 / Online ISSN:0976-0571 Effect of different levels of nitrogen and potassium against leaf spots disease of groundnut in different fertility gradient soil in field Trina Sandham, Sunita Mahapatra* and Srikanta Das Department of Plant Pathology, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur-741 252, West Bangal, India. Received: 26-10-2017 Accepted: 10-02-2018 DOI: 10.18805/LR-3957 ABSTRACT The occurrence of early and late leaf spots of groundnut under influence of variable soil fertility states with further interaction to different levels of nitrogen and potassium was measured and the same was correlated with the yield attributing parameters. Two different nitrogen and potassium combinations (20; 40 kg ha -1 ) applied on four different fertility gradient soil (low ,S 1 ; medium ,S 2 ; moderate ,S 3 and high ,S 4 ) showed minimum leaf spot disease severity and maximum diseases reduction in (S 1 ) N 40 K 20 (AUDPC 34.48 and 16.06% reduction); (S 2 ) N 40 K 40 (AUDPC- 32.88 and 13.68% reduction ); (S 3 ) N 20 K 40 (AUDPC 31.51 and 11.44% reduction) and (S 4 ) N 20 K 20 (AUDPC-25.40 and 11.58% reduction). The yield attributes like kernel number and weight per plant and kernel yield were also high in above combinations and fertility gradient soil. The linear regression value between disease severity and yield parameters showed a high co-relation regression and negatively significant at all fertility gradient soil and more responsive at low, medium and high fertility gradient soil irrespective of different N and K levels. Key words: Disease severity, Fertility gradient, Groundnut, Kernel yield, Leaf spot severity, N & K levels, Yield characters. INTRODUCTION Groundnut (Arachis hypogea L.) is one of the principal economic oilseed crops in India next to mustard. It is the most important summer season cash crop as well as oil seed crop in the world (Mensah and Obadoni, 2007). In comparison with other oilseed crops, groundnut stands highest in area, production and productivity in India (7572 ha, 9164 thousand tonnes, 1210 Kg ha -1 respectively (Anonymous, 2000). Groundnut suffers from different diseases of biotic and abiotic origin. Among the biotic constraints, fungal diseases are one of the major hindrance affecting the qualitative and quantitative yield of the crop. The leaf spot or tikka diease (Cercospora arachidicola and personatum) of groundnut (Arachis hypogea L.) is a predominant, devastating and economically important foliar fungal disease and a major yield reducing factor of groundnut in the world (Hasan et al., 2016). Cercospora leaf spot disease decline the kernel yield from 5.78 to 5.50 g m -2 plot in every 1% increase in disease severity (Das and Roy, 1995). To achieve increasing demand of oilseed production the farmers traditionally follow staggered and inappropriate application of chemical fertilizers without considering fertility status of the soil. But the increased use of chemical fertilizers in different regions predisposes the cultivated crop towards infection by various diseases in low to severe form. Nutrition plays an important role in the resistance or susceptibility of host against different pathogens. A disease can be eliminated by application of different nutrition but the severity of many diseases is reduced by specific levels of fertility gradient, arranged by soil treatment with different NPK and organic matter like FYM before cultivation. With increasing level of N and decreasing level of K maximum disease severity and poor yield were obtained in wheat infected with Helminthosporium sativum (Devi et al., 2012). Similarly maximum tuber yield and minimum foliar disease were observed in moderate level of N (150kg ha -1 ) and maximum potassium (125kg ha -1 ) in low, medium and high fertility gradient soil (Mahapatra et al., 2012). The present investigation has been conducted to find out the actual doses of nitrogen and potassium required under different soil fertility status to obtain higher yield of groundnut with less disease. MATERIALS AND METHODS The experiment was conducted at the Regional Research Station, Gayeshpur, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal during the pre-kharif season for three consecutive years 2012 to 2014. Soil was sandy loam in texture and latitude 22º93N and longitude 88º33E. Four fertility gradients in the experimental field were prepared and maintained by cultivation of maize during rabi season. The field consisted of 4 strips each divided into four equal plots covering a total area of 2000 m 2 and individual strip of 500 m 2 . Each of the plots was separated by one meter irrigation channel. The fertility gradient strips were made by applying different doses (kg ha -1 ) of NPK viz. low (S 1 )-(0:0:0), medium (S 2 )-(50:31:67), moderate (S 3 ) -