EFFECT OF EXCESS NITROGEN FERTILIZATION ON TRITICALE PRODUCTION UNDER RAINFED AND SUPPLEMENTAL IRRIGATION CONDITIONS

Abstract

Triticale (Triticosecale Wittmack) is an annual human-made cereal that belongs to the family Poaceae. It is an important crop in various regions of the world, known for its high forage potential, with little known about its water and nutrients requirements. This research presents the results of two adjacent field experiments that were conducted in the fall and spring of 2020-2021 at the Advancing Research Enabling Communities Center (AREC) in the Beqaa plain at the American University of Beirut, Lebanon to examine the effect of various rates of nitrogen fertilizer on growth parameters and yield quantity and quality of triticale under rainfed and supplementary irrigation. Each of the field experiments consisted of seven fertilizer treatments (0, NPK at 100 kg/ha, nitrogen at 40, 80, 120, 160, and 200 kg/ha). Supplementary irrigation was applied three times during the growing season starting 148, 157, and 172 days after planting (DAP). Data collected were plant height, shoot number, shoot fresh and dry weight, grain yield, spike number and weight, hay dry weight, and various grain parameters such as protein, fiber, starch, ash, fat, moisture and morphology. Results showed that supplementary irrigation increased crop height, shoot fresh weight, and grain yield, compared to the rain-fed regardless of NPK or nitrogen applications. While it did not increase shoot dry weight in comparison to the rainfed. Neither nitrogen treatments nor supplementary irrigation alone enhanced hay dry weight, compared to rainfed. The addition of nitrogen at all tested rates had no significant effect on triticale shoot dry weight and grain yield under both irrigation systems. A higher yield was obtained under supplementary irrigation than in the rainfed system regardless of the nitrogen application. The average grain yield of triticale under supplementary irrigation was 5.8 tons/ha while it was 4.9 tons/ha under rainfed conditions. Spike number and weight with or without nitrogen fertilizers were higher under supplementary irrigation than in the rainfed system. Grain protein content under rainfed conditions with or without nitrogen was higher than supplementary irrigation. While the grain starch content under supplementary irrigation with or without nitrogen was higher than the rain-fed. The addition of nitrogen fertilizer did not enhance grain starch content. Results show a negative relationship between grain starch and protein content under both irrigation systems. Supplementary irrigation with or without nitrogen did not increase the grain ash content of grain in comparison to all rain-fed treatments. Application of nitrogen at all tested rates increased the grain moisture content under rain-fed compared to the supplementary irrigation. Morphological measurements of 3 supplementary irrigation alone or with nitrogen were higher than under rainfed conditions. Nitrogen at all tested rates increased the grain area of triticale under supplementary irrigation, compared to the same treatments under rainfed conditions. Supplementary irrigation alone significantly increased the grain area and grain length and width in comparison to all nitrogen treatments under both irrigation systems. Results showed that supplementary irrigation alone or with NPK resulted in higher plant biomass and yield (quantity and quality) than other nitrogen fertilizers under rainfed conditions.