EFFECTS OF AVAILABLE SOIL MOISTURE DEPLETION LEVELS AND SOME FOLIAR – SPRAYED ORGANIC ACIDS ADDITIONS ON YIELD AND SOME CROP WATER RELATIONS OF DRIP-IRRIGATED MAIZE

A field experiment was conducted at ElAreish Agricultural Research Station, North Sinai Governorate, Egypt, during 2010 and 2011 summer seasons to study the effect of available soil moisture depletion levels and foliar spray with some organic acids on grain yield, yield components, nutrient contents in grains and some crop-water relations for drip – irrigated maize (SC-10 Hybrid) . Three irrigation regimes i.e. irrigation at 75, 60 and 45% of available soil moisture depletion(ASMD) as interacted with citric, salicylic and ascorbic acids besides the control, applied as foliar spray, at 35 and 50 days after sowing in the concentration of 1g/L. The adopted treatments were assessed in split plot design with four replicates. The main obtained results were as follows:1. The maize grain yield significantly affected due to the adopted irrigation treatments in both seasons and irrigation at 45% ASMD regime resulted in higher grain yield and yield components values. On the contrary, the lowest values were obtained from irrigation at 75% ASMD regime. 2. Foliar spray with the tested organic acids significantly affected grain yield and most yield components in the two seasons of study and higher values were resulted from foliar sprayed ascorbic acid. 3. Interaction of the adopted treatments significantly did not influence grain yield and yield components attributes in the two seasons of study. 4. The tested irrigation treatments insignificantly affected N, P, and K grains contents, however, higher values were noticed due to irrigation at 45% ASMD regime. Foliar spray with ascorbic acid resulted in the highest grains N and P figures. In addition, interaction of the adopted treatments insignificantly altered grains N, P and K contents, however, higher values of grains N and P contents were noticed due to interaction of irrigation at 45% ASMD and foliar spray of ascorbic acid. 5Seasonal evapotranspiration (ETc) values as a function of assessed treatments were 54.82 and 55.45 cm in 2010 and 2011 seasons, respectively. Irrigation at 45% ASMD resulted in the highest ETc values, while, the lowest ones were obtained due to irrigation at 75% ASMD regime. Foliar spray with the tested organic acids slightly reduced ETc values, comparable with the control. Interaction of irrigation at 45% ASMD and no-foliar spray with organic acids (control) gave the highest ETc values which comprised 55.38 and 56.06 cm in 2010 and 2011 seasons, whereas the lowest ones were detected from irrigation at 75% ASMD and foliar application of ascorbic acid in 2010 season and with irrigation at 75% ASMD and foliar spray with citric acid in 2011 season (35.55 and 37.17cm, respectively). 6The calculated crop coefficients were 0.22, 0.43, 1.14, 1.02 and 0.34 for May, June, July, August and September (Mean of two seasons). Abd El-Latif, K. M. et al. 1186 7The highest water use efficiency values resulted from irrigating maize at 75% ASMD which reached 1.57 and 1.37 kg grains m -3 water consumed, while irrigation at 45% ASMD gave the lowest values which comprised 1.44 and 1.31 grains m -3 water consumed in the two seasons, respectively. The tested organic acids resulted in higher WUE values, comparable with the control, and ascorbic acid gave the highest values which comprised 1.90 and 1.67 kg grains m -3 water consumed in the two seasons, respectively. Higher WUE could be achieved due to irrigating maize plants at 75% ASMD as interacted with foliar spray of ascorbic acid . Under the trial conditions and on achieving higher water productivity and reasonable maize grain yield as well, its advisable to irrigate maize crop at 60% ASMD regime with foliar spray of citric, salicylic or ascorbic acids.