Author(s):

Debabrata Dhar, Niladri Paul, Ashim Datta and Dipankar Saha

Abstract: The influence of organic matter vis-a-vis humic acids on soil nitrogen status and its availability and economic impact, during the cultivation of rice (variety MTU 1010) followed by mustard (variety B-9), was studied in the soil of Typic <em>Fluvaquents </em>situated in old alluvial soil of West Bengal, India. The status of soil texture, bulk density, oxidizable organic carbon, pH, total nitrogen, available nitrogen and microbial biomass nitrogen were sandy clay loam, 1.34mg m^–3, 1.16 g 100g^–1, 6.34, 0.14 g 100 g^–1, 231.36 kg ha^–1, 11.86 µg g^–1 respectively. The C: N ratio of the added FYM, commercial and FYM extracted humic acid were 32.11, 32.61, 13.53 respectively. Along with recommended dose of fertilizers, basal soil of paddy (N:P₂O₅:K₂O:: 60:30:30) followed by mustard (N:P₂O₅:K₂O :: 80:40:40) was treated with FYM (@ 5.0 and 2.5 t ha^–1), commercial humic acid (@ 0.5, 0.25 kg ha^-1) and FYM extracted humic acid (@ 0.5, 0.25 kg ha^–1) respectively. The experiment was undertaken with three replications with plot size of (3 × 4) =12 sq.m. Following the randomized block design (RBD). Rhizosphere (0-15 cm) soil-plant samples were collected and analysed for total nitrogen, available nitrogen, microbial biomass nitrogen, plant uptake and their overall effect on economic yield of crops. As panicle initiation and branching stages of paddy and mustard highest content of total nitrogen was recorded which gradually decline towards harvesting stage. FYM extracted humic acid increased N-availability, MBN in soil which signified N-uptake within plants resulted significant yield of paddy. Residual effect of FYM along with additional dose to mustard resulted highest significant yield of plant biomass whereas irrespective of treatments the yield of mustard is similar.

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