Experimental Site The experimental site is located in the agro-ecological zone (AEZ) 28 that lied at 23°59'13.53"N Latitude and 90°24'53.35"E Longitude. The elevation of the experimental site is 15 m above mean sea level. The soil of the experimental field belonged to the Madhupur Tract (BARC 2005) and it is silt loam underlain by sandy loam. The organic matter content of the experimental soil is 0.85 %. The climate of the experimental site falls under the sub-tropical, which is characterized by high temperature, high humidity, and average rainfall of 2376 mm with occasional gusty winds in kharif season (April–September). Whereas, less rainfall associated with moderately low temperature exists during the rabi season (October–March).
The experimental plots were laid out with split plot design (SPD) having three irrigation treatments and four tillage treatments. There were three replications of combinations of both the treatments. According to the split plot design, tillage treatment was assigned in the main plot and the irrigation in the sub plots. All of these events were randomly chosen to avoid any biasness towards the selection. Irrigation treatments were:I1: 17-21 DAS (Day after sowing), I2: 17-21 DAS + 50-55 DAS, I3: 17-21 DAS +50-55 DAS + 75-80 DAS; and tillage treatments were: T1 (bed planting), T2 (Power tiller operated seeder), T3 (strip tillage) and T4 (zero/no tillage).These methods are briefly explained below Bed Planting (T1): Power tiller operated bed planter was used to make raised beds of 12–13 cm height where row (in between two beds) to row spacing was 55–56 cm. Seeding was done in two rows on each raised bed. Power Tiller Operated Seeder (PTOS) (T2): The main function of PTOS is to form broad beds and simultaneously undertake sowing in rows on the bed. Broad beds were separated by furrows at a spacing of 160 cm. Strip tillage (T3): It is a minimum tillage technique where seedbed is divided into seedling zone. The seedling zone (5–8 cm wide) was mechanically tilled to optimize the soil and microclimate environment for germination and seedling establishment. Zero tillage (T4): It is a way of growing crops without disturbing the soil. Seeding was done in rows by opening soil with the help of power tiller mounted zero tillage planter.
Sowing of seeds and application of fertilizer Bangladesh Agricultural Research Institute (BARI) developed wheat variety- Prodip (BARI GAM-24) was sown in the experimental plots having different tillage conditions at the rate of 120 kg ha-1. Seeds were sown in rows at 2–3 cm depth with 20 cm row to row spacing in all tillage treatments except bed planting. Two rows of seeds on each raised bed were maintained in case of bed planting where bed to bed spacing was 55–56 cm. Fertilizers were applied at the rate of 100 kg N, 26 kg P, 40 kg K, 20 kg S, and 1 kg B ha-1. Urea, TSP, MoP, gypsum, and boric acid were used as sources for N, P, K, S, and B, respectively. Two-thirds of N and total amount of other fertilizers were applied at the time of sowing and the remaining N was top-dressed after first irrigation.
Determination of crop water requirement (WR) The water requirement for wheat was computed by the following equation having three components: total irrigation required (IR), effective rainfall (ER), and soil moisture contribution which comprises the last part of the equation.
Experimental Data Collection Data on different yield contributing characteristics (spike, plant height, spike length, spike lets/spike, grains/spike, thousand grain weight, etc.) were recorded after harvesting of 5 sample plants from each plot. For calculation of grain yield, plants from 2x 1 m2 sample areaof each plot for zero tillage, PTOS, strip tillage, and 2x 1.1 m2 area for bed planting were harvested.Grains obtained from sample areas of the respective plot were dried in the sun and weighed at 12% moisture content to determine the grain yield per plot and was expressed in t ha-1. Soil samples were collected from 0 – 15, 15 – 30, and 30 –45 cm depth of the experimental plots and average soil moisture content was calculated by gravimetric method.
Statistical analysis of data An analysis of variance (ANOVA) was done for the data to sort out significant difference among treatments and DMRT was used to compare treatment means by using MSTAT-C program. Necessary graphs were made by using XLSTAT 2016 software.