Effects of Deficit Irrigation Strategies on Growth and Yield of Maize in Arid Area of Pakistan
Field experiment was carried out to study the comparative effects of partial root-zone drying and deficit irrigation techniques on growth and yield of maize (Zea mays L.). The experiment was conducted on Sakhani Agricultural Experimental Station D.G. Khan in Punjab, Pakistan, which is hot subtropical continental arid area with mean annual precipitation ranging from 150-250 mm and its temperature in summer rises up to 40-44℃and in winter it ranges from 6-8℃. The soil type of the site is clay with pH of 8.48 and organic matter 1.56%, ECw 2.45 dSm-1 and sodium absorption ratio 0.4%, Irrigation were carried out with well water having pH of 7.82, ECw 1.112 dSm-1 and sodium absorption ratio 0.4%. Hybrid maize [Hycorn 984] was grown in rows under drip irrigation system in three replications.
Studied treatments were alternate partial root-zone drying (APRD), fixed partial root-zone drying (FPRD) and deficit irrigation (DI) compared with full irrigation (FI). Root-zone of the FI treatment was kept close to the field capacity while all other treatments were irrigated with 50% quantity of the water applied to the FI through out the growing season, but the distribution of that 50% water in DI was made in such a way that it received more water at reproductive stage than vegetative stages.
Data indicated that, among all the treatments APRD has the highest value of both grain yield water use efficiency (WUEy) and dry biomass water use efficiency (WUEb) and was increased 73% and 80% respectively from FI. The values of both WUEy and WUEb were significantly lower in FPRD and DI as compared to APRD and there was no any significant difference between FPRD and DI regarding both WUEy and WUEb. Lowest values for both WUEy and WUEb were obtained in FI.
Highest root biomass was produced under FI and its production was less in APRD, but APRD was better than either FPRD or DI in terms of root biomass production. There was no any significant difference between FPRD and DI regarding root biomass. The results of the experiment showed that APRD did not severally inhibit the root growth neither the root-shoot ratio as compared to FI. Highest root-shoot ratio was obtained under FI and root-shoot ratio was significantly lower in DI and FPRD when compared to FI. There was no any statistical difference between FPRD and DI in case of root-shoot ratio.
Water stress in APRD, FPRD and DI treatments significantly reduced the plant height as compared to FI, and among the deficit irrigation treatments maximum plant height was obtained under APRD. There was no any significant difference between FPRD and DI regarding plant height. Total biological weight was high in FI as compared to APRD, FPRD and DI and it was ranked as FIAPRDDIFPRD, but there was no statistical difference between the values of DI and FPRD.
There was no significant decrease in the number of leaves per plant in APRD as compared to FI. And the number of leaves per plant was statistically same among FPRD and DI but it was decreased in both of them as compared to FI and APRD. Highest leaf area per plant was produced by the plants of FI treatments, and it was decreased in APRD as compared to FI. There was no any significant difference in leaf area per plant among the plants of FPRD and DI but it was significantly lower in both of them as compared to FI and APRD.
Grain yield per plant was significantly reduced under deficit irrigation strategies as compared to the FI. It was ranked as FIAPRD FPRD DI, and the reduction in grain yield per plant in APRD, FPRD and DI was 13.47,24.19 and 25.55% respectively. The number of cobs per plant was same in all the treatments. Production of maize grains per hectare was higher in FI followed by APRD. Grain yield per hectare was significantly lower in FPRD and DI as compared to FI and APRD, and there was no any significant difference between FPRD and DI regarding grain yield per hectare.
Results showed that 50% reduction in the irrigation water reduced the grain yield and inhabited plant growth but increased the water use efficiency. APRD performed well in dry biomass production, plant height, leaf area per plant, number of leaf per plant, root development, grain yield per plant and yield per hectare as compared to FPRD and DI treatments. There was no any significant difference between FPRD and DI treatments neither in vegetative growth nor in reproductive growth.