Experimental site and soil:
The research work was conducted at the Soil Science Field Laboratory of Bangladesh Agricultural University (BAU), Mymensingh during Rabi season from November 2017 to February 2018. The geographical location of the field is 24°75′ N latitude and 90°50′ E longitude at the elevation of 18 m above the sea level. The land topography was medium-high belonging to the Sonatala series of Non-Calcareous Dark Grey Floodplain Soils of AEZ-9 named Old Brahmaputra Floodplain (FAO, 1988). The land was moderately well-drained and sufficient sunshine was available throughout the experimental period. The soil was silt loam in texture having pH 6.28, organic matter content 1.12%, total N 0.152%, available P 11.08 ppm, exchangeable K 0.053 me% and available S 9.83 ppm.
Treatments and experimental design:
The experiment was laid out in a randomized complete block design (RCBD) with three replications. The four treatment combinations were T1 Foliar spray with water (control), T2 (MLE foliar spray at 2 weeks after transplanting), T3 (MLE foliar spray at 2 weeks and 4 weeks after transplanting), T4 (MLE foliar spray at 2 weeks after transplanting and after every two weeks thereafter). The experimental area was divided into three blocks representing the replication and each block was subdivided into four-unit plots. The treatments were randomly distributed to the unit plots in each block. The total number of plots was 4×3 = 12. The unit plot size was 2.5m × 2m. The spacing between blocks was 0.8 m and the plots were separated from each other by a space of 0.5 m.
Seedling transplanting:
In this experiment, cabbage (hybrid variety named Atlas 70) was used as test crop. About 25-days-old cabbage seedlings were transplanted in the experimental plots on the 14th of November 2017. The seedlings were uprooted from the seedbed carefully to avoid damage of the root system and transplanted in the afternoon followed by light irrigation for their better establishment. The line to line distance was 60 cm and plant to plant distance was 50 cm.
Fertilizer application:
The full amount of triple superphosphate (TSP), muriate of potash (MoP), gypsum, zinc oxide and boric acid were added during final land preparation as basal dose at the rate of 66, 70, 24, 3 and 1 kg ha-1, respectively according to the Fertilizer Recommendation Guide (FRG, 2012). Urea was applied in three installments and the rate was 180 kg ha-1. The first split was applied as basal during final land preparation, while the second and third split were applied as top dressing at 30 and 45 DAT (days after transplanting), respectively.
Collection and preparation of MLE:
Fresh young leaves were collected from matured trees located at different places of Bangladesh Agricultural University Campus, Mymensingh for preparation of MLE. About 100 g of collected leaves were taken into a mortar with a pinch of water (10 mL/100 g fresh material) and ground with a pestle. The juice was extracted by pressing with hand and was filtered through a cheese cloth followed by re-filtering using Whatman filter paper No. 2. Following the method developed by Fuglie, the extract was then diluted with distilled water at a ratio of 1:32 (v/v) and sprayed directly onto the cabbage plants. The remaining extract was stored at 0ºC temperature and taken out only when needed for use.
Foliar application of MLE in cabbage:
The prepared MLE was sprayed @ 25 mL plant-1 as per treatments using hand sprayer in the late afternoon with special attention for complete coverage of plants with MLE. In the control plots water was sprayed instead of MLE and special attention was given to avoid drifting of spray materials from one plot to another.
Intercultural operations:
Light watering was done by using a watering can at every morning and afternoon following seedling transplanting and was continued for a week for rapid and well established of the transplanted seedlings. In the field, flood irrigation was given at 30 DAT and 45 DAT after the establishment of seedlings. Other intercultural operations such as weeding, fencing, gap filling, and application of pesticide were done as and when necessary.
Harvesting and data collection:
The crop under investigation was harvested on the 16th February 2018 at full maturity stage. Data on growth and yield parameters such as plant height, leaf number, length, breadth and weight of the largest leaf, weight of root and stem, head thickness, head diameter, head weight, total weight of plant, gross yield and marketable yield were recorded at the time of harvesting.
Preparation and analysis of plant samples: The head samples of cabbage were dried in an oven at 65° C temperature for about 48 hours and then ground by a grinding machine to pass through a 20-mesh sieve. The ground plant materials were stored in paper bags separately, placed in a desiccator and analyzed for the determination of macronutrient contents namely N, P, K and S. The total N, available P, exchangeable K and available S of plant samples were determined following semi-micro Kjeldahl method, modified Olsen method, NH4OAc extraction method and CaCl2 extraction method, respectively. After chemical analysis of head samples, the nutrient uptake was calculated from the nutrient content and yield of the crop.
Statistical analysis:
The collected data on different parameters were analyzed statistically to get the level of significance using the MSTAT–computer package program (Russell, 1986). The differences among treatment means were compared by Duncan's New Multiple Range Test (DMRT) at 5% level of probability (Gomez and Gomez, 1984).