The maize (Zea mays, L.) was grown on a clay soil at Irrigation Development Area of Alwezaria, Kafrelshiekh, Egypt, during 2012 and 2013 seasons, to study the effect of irrigation regimes during different growth stages on growth, grain yield and water relations. Irrigation was applied at 50% (high level, H) and 65% (low level, L) depletion of available soil moisture (DAM) during different growth stages [vegetative stage (S1) from the third leaf (V3) to onset tasseling (VT) stages, reproductive stage I (S2) from VT to mid-milk (R3) stages, reproductive stage II (S3) from mid R3 to physiological maturity (R6)].
IHHH treatment (Irrigated at 50% DAM during three growth stages) or IHHL (Irrigated with 65% DAM at S3 stage only and 50% DAM was used during S1 and S2 growth stages), ILHH (Irrigated with 65% DAM at S1 growth stage only and 50% DAM was observed during S2 and S3 growth stages) and ILHL (Irrigated with 50% DAM at S2 growth stage only and 65% DAM was observed during S1 and S3 growth stages) resulted in significant increase in leaf area index (LAI) and dry weight/plant at 99 days after sowing (DAS), crop growth rate (CGR) at the period of 81-99 DAS, ear length, ear diameter, kernels number/ear, grain weight/ear, 100-grain weight and grain yield compared with ILLL (Irrigated with 65% DAM during three growth stages ) in the two seasons. There were no significant differences in grain yield among the irrigation treatments IHHH, IHHL, ILHH and ILHL in the mentioned traits in both seasons.
Abundance soil moisture in root zone during S2 stage (containing tasseling, silking, blister and mid-milk stages) is necessary to achieve high grain yield equal to that during entire season. IHHH treatment recorded the highest values of applied water (7286 and 7321m3/ha), while ILLL recorded the lowest values 6171 and 6198 m3/ha in the two seasons. Although, the treatments received irrigation at 50% DAM during S2 stage (IHHL, ILHH and ILHL treatments) were equivalent to those received irrigation at 50% DAM during entire seasons (IHHH treatment), they were lower in amount of applied irrigation water and water consumptive use. They saved at least 11.3, 16.0 and 19.9% applied water parallel with the yield decrease at the most 3.1, 3.2 and 5.3% than IHHH treatment, respectively. Also, they increased the productivity of applied water (WPwater applied) and water consumptive use (WP WCU) (kg grain/m3 water) compared with IHHH in both seasons.
At North Delta, Penman Monteith equation can be used in determining the actual consumptive use and the average of crop Coefficient (Kc) for the two seasons was found to be 0.43, 0.54, 0.64, 0.58 and 0.51 during emergence, vegetative, tasseling to milk, milk to dent and dent to maturity stages, respectively. Therefore, when irrigation water becomes a limited factor for agriculture, we can apply ILHL treatment which resulted in high grain yield and water productivity equal to IHHH with less amount of applied irrigation water and consumptive use in Kafrelshiekh Governorate.