The experiments were conducted during 2016-2017 and 2017-2018 at the farmers' fields of the village of Pankhali and Khatail at Dacope, Khulna and Sikandorkhali at Amtali, Barguna under the ACIAR-KGF project which is situated in the coastal regions of Bangladesh. The experiments were carried out at two farmer’s field at Pankhali and three farmers’ field with six irrigation treatments and replicated thrice. The plot size was (30 m2) which depended on existing farmers’ plot.
Experimental design and treatments:
The field experiment was laid out in randomized complete block design (RCBD) with six treatments replicated thrice. The treatments consisted of two and three irrigation levels were:
T1= 2 irrigations (IR) at vegetative stage and grain development stages with FW
T2 = 2 IR at vegetative stage with FW and grain development stage with SW
T3 = 2 IR at vegetative stage with FW and tasseling stage with SW
T4 = 3 IR at vegetative, tasseling and grain development stages with FW
T5 = 3 IR at vegetative stage with FW and tasseling and grain development stages with SW
T6 = 3 IR at vegetative and tasseling with FW and grain development stages with SW
Soil physical and chemical properties:
Before crop sowing, soil samples were randomly collected from the desired depth (0-60 cm) of the experimental plots to determine the soil physical and chemical properties at the farmers' field of the village of Pankhali at Dacope, Khulna and Sikandorkhali at Amtali, Barguna under the ACIAR-KGF project sites. The physical properties of field capacity (%), percentage of clay and silt and soil texture were determined from the Soil Science Laboratory, BARI, Gazipur. The percentage of organic matter (OM), pH, total nitrogen (N), phosphorous (P), potassium (K), sulpher (S), zinc (Zn) and Boron (B) were also determined in the Soil Science Laboratory, BARI, Gazipur. All chemical properties were found greater than critical values. The bulk density and initial gravimetric soil water content and soil salinity were measured in both locations.
Crop management:
Standard crop management practices were followed. Recommended fertilizer dose and applied in the form of urea, triple supper phosphate, muriate of potash, gypsum, zinc sulfate and borax, respectively (Fertilizer Recommendation Guide, 2012) and application methods were applied. In this study, ZT is considered as one of the many types of CT for row crops. Mixed fertilizers were placed into the soil uniformly and soil packed to minimize fertilizers tie up with manually. Sub-surface placement of band fertilizer was placed. Half of the nitrogen and potassium and all phosphorous, sulphur, zinc and boron were applied as basal doses below the soil surface as horizontal and vertical separation of seed during planting. Remaining nitrogen and potassium were applied as earthing up operation followed by irrigation. Adequate plant protection measures were taken at vegetative stages.
Application of irrigation water and water use:
Irrigation scheduled was followed according to BARI IWM recommendations. Irrigation frequency was considered at every certain interval depending on the different growth stages (initial stage, vegetative stage, flowering and grain development stages (Sarker et al, 2016) from plant establish to before final harvest. Irrigation water was applied based on the pan evaporation method at Dacope at different crop growth stages. A class A pan evaporation was placed near to the experiment was used to estimate irrigation water requirement (I, mm) for full irrigation using the following equation.
p Kp A. Where, I is the amount of irrigation water amount (litre), A is the area of the plot (m2), Ep is the cumulative pan evaporation (mm) and Kp is the pan coefficient and was considered 0.7 (Michael, 1978).
Yield and water productivity:
The yield contributing characters and seed yield of maize were recorded from the plants during the experimental period. Five plants were randomly chosen to measure the seed yield components from each treatment. Economical grain yield (t/ha) were measured from the plants harvested from the selected two rows of each plot. Maize grain yield was manually harvested. Water productivity (WP) was calculated as the ratio of seed yield and total seasonal water use which was expressed by the following equation: WP = (GY x100) / (SCWU)
Where, WP is the water productivity (kg/m3), GY is the seed yield of maize (t/ha) and SCWU is the amount of seasonal crop water use (mm).
Statistical analysis:
Data on yield attributes, crop yield and water productivity were statistically analyzed to test the effects of irrigation levels and methods using R software version 3.5.0. All the treatment means were analyzed and compared for any significant differences using R-statistical models at 5% (P≤0.05) probability level of significant.