Response of Two Maize Hybrids to Urea Fertilization under Application of Hydroquinone Urease Inhibitor

TWO FIELD experiments were conducted during 2006 and 2007 summer seasons at Gaziret-Hanout,Kafr Sakr District, Sharkia Governorate, Egypt to study the response of two maize hybrids (SC 122 and TWC 310) to three levels of urea fertilization, i.e.75,100 and 125 kgN/fad(1ha=2.381fad) under application of three hydroquinone (HQ) urease inhibitor levels (0, 1.5 and 3.0 kg HQ/100 kg N). The adopted experimental design was split-split plot with three replicates.
The results revealed that TWC 310 maize hybrid was superior in most of studied characters compared to SC122 which superior in ear length and protein percentage. However, both tested hybrids gave almost the same protein yield/fad. Increasing N levels from 75 to 100kg N/fad resulted in a significant increase in plant height, 100-grain weight, protein percentage and protein yield/fad, while the increase in urea-N levels up to 125kgN/fad increased significantly all other studied characters, except oil percentage which significantly decreased by any increase in N levels up to 125kgN/fad. Treating urea fertilizer with HQ urease inhibitor at the rate of 1.5kgHQ/100 kg N increased significantly both plant height and 100-grain weight, while increasing HQ levels up to 3.0kgHQ/100 kg N resulted in a significant increase in the other most studied characters compared with untreated urea. Any further HQ increment caused further reduction in oil percentage.
Regarding the interaction effects, TWC 310 gave the higher number of grains/ ear when urea was treated with 3.0kgHQ/100kgN with a response rate of 25.66 grain yield/ fad was responded to urea-N up to 100 kg N/fad when 1.5 or 3.0kg HQ/100kg N was added. The highest oil yield / fad was attained when 125 kg N/fad was applied and when urea treated with 3.0 kg HQ/100 kg N.
The results revealed positive and significant correlation coefficients between grain yield/ fad, and most of studied characters, while negative and significant correlation was found for grain yield related to oil percentage. The path analysis revealed that the direct effect of number of ears/plant was 17.06% being higher than that of 100-grain weight and number of grains/ear which was 15.18 and 5.11% of maize grain yield variation, respectively. Regression analysis revealed that number of ears/ plant and number of grains/ ear are similar to that of grain yield and each is of quadratic relationship with urea-N fertilization, while the response of 100-grain weight to urea-Nfertilizer had a linear relationship.