Author(s):

Renu Gupta, AP Rai and Sanjay Swami

Abstract: A field trial was conducted for two consecutive years to evaluate onion (Allium cepa L.) performance, soil fertility build-up and estimation of soil enzymes, soil microbial biomass and microbial population under integrated nutrient management with two organic manures viz. vermicompost and farmyard manure (FYM) in combination with NPK fertilizers in sub-tropical zone of Jammu. The treatments tested were: T₁- control; T₂ - 100% NPK alone; T₃ - 100% NPK + 12.5 t FYM ha^-1; T₄ - 100% NPK + 25 t FYM ha^-1; T₅ - 100% NPK + 12.5 t vermicompost ha^-1; T₆ - 100% NPK + 25 t vermicompost ha^-1. The maximum onion yield was recorded with the application of 100% NPK + 25 t vermicompost ha^-1 (T₆) during both the years i.e. 9.63 and 10.34 t ha^-1. The application of FYM @ 25 t ha^-1 (T₄) recorded 23 and 18% increase in yield of onion over 100% NPK alone (T₂) during 2012-13 and 2013-14, respectively, whereas vermicompost @ 25 t ha^-1 (T₆) recorded 39 and 31% increased onion yield. A comparison between FYM and vermicompost receiving treatments revealed that the treatments receiving same quantity of vermicompost recorded higher yield in comparison to FYM. Furthermore, yield of onion obtained with 12.5 t vermicompost ha^-1 plus 100% NPK (T₅) during both the years was at par with that received under 25 t FYM ha^-1 plus 100% NPK (T₄) demonstrating superiority of vermicompost over FYM. Application of vermicompost @ 25 t ha^-1 plus 100% NPK (T₆) also increased N uptake over 100% NPK alone (T₂) by 120 and 138% by onion during both the consecutive years, respectively. The corresponding increase in P uptake was 164 and 130% whereas in case of K, it was 112 and 171%. The highest soil available N, P and K content was observed with T₆, as 296, 25.7 and 343 kg ha^-1. The treatment T₆ also increased organic carbon content over 100% NPK treated plots (T₂) by 58%. Microbial population increased by 149% cfu × 10^-4 and 70% cfu × 10^-4 in T₆ over control and T₂, respectively. Soil microbial biomass varied considerably among treatments and ranged from 41 to 143 mg kg^-1 and the highest microbial biomass was recorded in T₆. Phosphatase activity exhibited increasing trend with the application of both FYM and vermicompost and the highest value was observed in T_6. NPK fertilizers alone recorded significantly higher phosphatase activity and it increased by 36% over control. Use of chemical fertilizers alone i.e. 100% NPK exhibited a lower dehydrogenase activity compared with conjoined use of inorganic and organic treatments.

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