Field experiments on cabbage (variety-Atlas 70) was carried out in the rabi season of 2015-2016 at the Bangladesh Agricultural Research Institute (BARI), Joydebpur (24° 00′ N, 90° 25′ E and 8.4 m asl). Joydebpur soil belongs to the Chhiata series of Grey Terrace Soil (Inceptisol; AEZ-28) (BARC 2005). The experiment was laid out in a randomized complete block design (RCBD) with six treatments replicated three times. The 6 treatments were: T1 = Vermicompost 2.5 t ha-1 + IPNS basis inorganic fertilizers, T2 = Vermicompost 5 t ha-1 + IPNS basis inorganic fertilizers, T3 = Composted FYM 2.5 t ha-1 + IPNS basis inorganic fertilizers, T4 = Composted FYM 5 t ha-1 + IPNS basis inorganic fertilizers, T5 = Recommended inorganic fertilizers, T6 = control. The unit plot size was 3m x 3m. Equal sized healthy thirty days old seedlings of cabbage were transplanted on 13th November, 2015 with a spacing of 60 cm from row to row and 50 cm from plant to plant. The recommended dose of chemical fertilizer (RDCF) for cabbage was N240 P35K60S30B1 kg ha-1.
Initial soils and organic materials were analyzed to know the organic C and other nutrient status (Table 1and 2). Urea, TSP, MP, Gypsum and Boric acid were used as a source of N, P, K, S and B, respectively. All P, K, S, B, VC and FYM and 1/3 N were applied at the time of final land preparation and the remaining 2/3 N was applied in two equal installments at 25 and 45 days after transplanting. The vermicompost and composted farmyard manure was used as organic supplement for crop production.
The vermicompost was prepared from cow dung by using earthworm Eisenia fetida in chari method. Farmyard manure was collected (2 week old) from a local farmers house, mainly consisted of discarded cattle feed, chopped fodder and animal excreta, dumped in the boundary of it. The farmyard manure was composted by following popular pit method. All the intercultural operations were done per requirement.
Harvesting of cabbage was done when the head attained proper size and at full maturity. Five plants from each plot were tagged at random to take records on different agronomic parameters of cabbage. Data on growth, yield and yield contributing parameters were recorded and statistically analyzed with the help of statistical package MSTAT-C and mean separation was tested by Duncan’s Multiple Range Test (DMRT) (Steel and Torrie, 1960). Post harvest soils were also collected (up to 15 cm depth) and analyzed for nutrient study following the standard procedure. Plant samples including roots of the respective treatment were also collected and analyzed.
Methods of chemical analyses
For initial and post harvest soil of cabbage analysis, soil pH was measured by a combined glass calomel electrode (Jakson, 1958). Organic carbon determination was by wet oxidation method (Walkley and Black). Total N was determined by modified Kjeldahl method. Ca and Mg were determined by KCl extractable method. K, Cu, Fe, Mn and Zn were determined by NaHCO3 extraction followed by AAS reading. Boron was determined by CaCl2 extraction method. Phosphorus was determined by Bray and Kurtz method while S by turbidimetric method with BaCl2.
The plant samples from each plot were dried at 65°C in an electric oven for 72 h then ground to pass through a 20 mesh sieve and analyzed following standard procedures. Plant samples were digested with H2SO4 for N and HNO3-HClO4 (3: 1) for other nutrients determination. Nutrient uptake was calculated by multiplying the concentration of the nutrients in the plant samples with the corresponding plant dry weights for input parameters for Translocation Factor (TF) and Biological Accumulation Coefficient (BAC).
At the end of the experiment C and other nutrients including micronutrients accumulation rates in soils was calculated using the following equation 1.
Rates of C accumulation (%) = {(C contents in compost applied plots – C contents in the control plot)/Carbon applied through compost} x 100 ………………………………............................................................................ (1)
Micronutrient translocation and bioaccumulation coefficients was calculated using the following equations (Cui et al., 2007; Li et al., 2007).
Translocation Factor (TF) was determined as ratio of micronutrients in plant shoot to that in plant root given in equation 2
TF = [micronutrients]shoot/[ micronutrients]root ................................................……………….. (2)
Biological Accumulation Coefficient (BAC) was calculated as ratio of micronutrients in shoots to that in soil given in equation 3.
BAC = [micronutrients]shoot/[ micronutrients]soil ……………………………..……………….. (3)