IMPACT OF HUMIC ACID APPLICATION AND NITROGEN FERTILIZER LEVEL ON BREAD WHEAT ‎PRODUCTIVITY UNDER SANDY SOIL CONDITIONS

Two field experiments were carried out at the Agricultural Research Station, Faculty of Agriculture, Zagazig University, El-Khattara region, Sharkia Governorate, Egypt during the two successive seasons of 2014/2015 and 2015/2016 to investigate the effect of three rates of humic acid application (0, 2 and 4 kg humic acid/fad.) and five nitrogen fertilizer levels (0, 30, 60, 90 and 120 kg N/fad.) on bread wheat (Triticum aestivum L. cv. Sids 12) grown in sandy soil under sprinkler irrigation system. Results of the combined analysis indicated that application of humic acid at 2 kg/ fad., significantly increased plant height (cm), flag leaf area (cm²), spike length (cm), number of spikes/m², straw yield (ton/fad.) and harvest index as compared to control treatment. Furthermore, flag leaf chlorophyll content (SPAD), number of grains/spike, weight of grains/spike (g), 1000-grain weight (g), grain and biological yields (ton/fad.) showed significant increase due to raising humic acid application up to 4 kg/fad. On the other hand, it was found that plant height, spike length, number and weight of grains/spike, number of spikes/m², 1000-grain weight, straw yield and harvest index were significantly increased by increasing nitrogen fertilizer levels up to 90 kg N/fad. Whereas, flag leaf area, flag leaf chlorophyll content, grain and biological yields per fad responded to each N increment up to 120 kg N/fad. Most studied traits were significantly affected by the interaction between humic acid and nitrogen fertilizer levels. It could be noticed that, application of humic acid resulted in reducing the requirement to N fertilizer application. The highest grain yield (16.25 ardab/fad.) was achieved by soil application of 4 kg humic acid with 90 kg N/fad.