The experiment was conducted at RARS, Rahmatpur, Barishal during 30 November, 2016 to 25 April, 2017 to study the effects of deficit irrigation on yield and water productivity of different maize varieties. The test crop was different high yielding variety of maize: BARI hybrid Maize 9 (BHM−9), BARI Hybrid Maize 5 (BHM−5), BARI Hybrid Maize 7 (BHM−7) and two commercial varieties NK-40 and Pacific-984. These varietes are popular due to their high yield potential and stress tolerant characteristics. The recommended doses of urea, triple super phosphate, muriate of potash, gypsum, zinc sulphate, borc acid, cowdung at the rate of 500, 240, 180, 240, 10, 5 kg/ha and 6 t/ha were applied. One-third of urea and the entire doses of other fertilizers were applied at the time of final land preparation. The rest two-thirds of urea was top dressed in two equal splits at 30 and 50 DAS. The first weeding was done manually at 20 DAS and also the thinning was done on the same day keeping only one healthy plant per hill; the rest of the plants were uprooted carefully to avoid disturbance to the nearby plants. At the next time, weeding was done only at 64 DAS during the growing season of the crop.
Experimental design
The experiment consisted of two factors: irrigation and variety. Irrigation and variety had five levels or treatments. Irrigation was scheduled based on the depth of water required. The irrigation treatments were allocated to the main plot and the varieties in the subplot. The irrigation and variety treatments were:
Main plot: Irrigation (5).
I1: Full irrigation at initial, vegetative, silking and grain filling (20-25 DAS, 50-60 DAS, 75-80 DAS and 110-120 DAS) stages (Farmer Practice)
I2: Full irrigation at initial stage (20-25 DAS)
I3: 50 % irrigation both at initial and vegetative (20-25 DAS and 50-60 DAS) stages
I4: 75% irrigation at initial, vegetative stage and silking (20-25 DAS, 50-60 DAS and 75-80 DAS) stages
I5: 50% irrigation at initial, vegetative, silking and grain filling (20-25 DAS, 50-60 DAS, 75-80 DAS and 110-120 DAS) stages
Subplot: Variety (5)
V1: BARI Hybrid Maize- 9
V2: BARI Hybrid Maize- 5
V3: BARI Hybrid Maize- 7
V4: NK-40
V5: Pacific-984
Water productivity
The water use of a crop field is generally described in terms of water productivity (WP), which is the ratio of the crop yield to the total amount of water used in the field during the entire growing period of the crop. The WP demonstrates the productivity of water in producing crop yield. WP for maize was calculated by:
WP = Y/(SWU), Where, WP = Water Productivity, kg/m3, Y= Grain yield, kg/m2, SWU = Seasonal water use in the crop field, m
The WU was calculated by summing up the water applied in irrigation (taking into account the rainfall) and soil moisture contribution.
Data analysis
The collected data were analyzed using MSTAT statistical package and the mean differences were adjusted by LSD.