Author(s):

Maneesh Kumar, SK Singh and SS Jatav

Abstract: Field experiments were conducted for three years in sandy loam soil to study the direct effect of organic manures i.e. sewage sludge (SS), vermicompos (VC) and sesbania (SB) with chemical fertilizers on rice (Oryza sativa) and their residual effect on wheat (Triticum aestivum) grown in sequence in winter (Rabi) and summer (Kharif) season during 2015-16 and 2016-17 at Varanasi, Uttar Pradesh. Twenty five percent nitrogen through supplement organic sources with 75% recommended dose of fertilizers, customized fertilizer, 100% RDF with S, Zn, B applied to rice and their effects were compared with the recommended dose of fertilizers i.e., 150, 60 and 60 kg N, P₂O₅ and K₂O ha⁻¹ and control, respectively. There was significant increase the concentration of Cd and Pb (straw and grain) of both the crops (grain and straw) with application of 75% RDF + 25% N through sewage sludge. The highest concentration of Cr in I rice grain was recorded in customized fertilizer and in I rice straw was highest in 75% RDF + 25% N through sesbania and minimum in control. The highest Cr concentration of I wheat grain increased 78% at residual effect of sludge application of previous rice over 100% RDF (T₂) similar trend was recorded in concentration of Cr in I wheat straw. During second year the highest Cr content in II rice grain and straw was varied between 1.49 to 4.03 mg kg^-1 and 3.82 to 7.93 mg kg^-1. The highest (4.03 mg kg^-1) content of Cr in II rice grain was recorded in 75% RDF with 25% N through sewage sludge which was 1.7 times increased respectively, over 100% RDF. The treatment T₅, T₆ and T₇ which receive 25% N supplement through organic sources were statistically at par with each other in II rice grain. Application of 75% RDF + 25% N through vermicompost increased the Cr content in II rice straw followed by 100% RDF + S, Zn, B which was 28 and 18% respectively, over 100% RDF. All the treatment of statistically at par with each other in II rice Cr content of straw. The Cr content in II wheat (grain and straw) which was statistically at par with each other. The Ni content in I rice grain was highest (4.32 mg kg^-1) in customized fertilizer and minimum in control. The treatment T₂ to T₇ show no significantly change from one other but increased in 100% RDF. Similar result was found in I rice straw content of Ni. The similar result was found that no significantly change with all seven treatment in Ni content of I wheat (grain and straw). The highest (4.49 mg kg^-1) content of Ni grain in II rice was recorded in customized fertilizer followed by sewage sludge treated plot and then vermicompost which was 1.9, 1.8 and 1.6 times increased respectively, over 100% RDF and control was 0.65% decreased over control. The Ni content of II rice straw was recorded no significant changes in all the seven treatments. The highest (17.21 mg kg^-1) Ni content in II wheat grain was recorded in residual effect of supplement through sewage sludge and minimum was in control. Treatment T₃ to T₇ was recorded in no significant changes one other in II wheat Ni grain content. The highest Ni content in II straw was recorded in 25% N supplement through sesbania with RDF and minimum was recorded in control. The minimum Ni content in II wheat straw was recorded in control which was 31% decreased over 100% RDF.

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