Relation between different organic sources and N-mineralization in ricemustard cropping sequence

Department of Soil Science and Agricultural Chemistry, College of Agriculture, Agartala-799 210, Tripura, India E-mail : nilupaul82@rediffmail.com Former, Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur-741 252, Nadia, West Bengal, India Manuscript received 17 February 2016, accepted 26 August 2016 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 Fluvaquent 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, 1.34 Mg m–3, 1.16 g 100 gm–1, 6.34, 0.14 g 100 gm–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 doses of fertilizers (N : P2O5 : K2O :: 60 : 30 : 30 and 80 : 40 : 40) basal soil of paddy followed by mustard was treated with FYM (@ 10 and 5 t ha–1), Commercial humic acid (@ 1.0, 0.5 kg ha–1) and FYM extracted humic acid (@ 1.0, 0.5 kg ha–1), respectively. The experiment was undertaken with 3 replications with plot size of (3×4 =) 12 sqm 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 yield of crops. At 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 effects from paddy irrespective of additional dose to mustard resulted similar yield effect on mustard and its biomass