Mixed Nitrogen Nutrition and Productivity of Wheat Grown in Hydroponics

The objective of this study was to study the effects of nitrogen(N) supplied as either mixtures of NO₃ and NH₄ or as all NO₃on the final yield of spring wheat. Two separate greenhouseexperiments evaluated the durum spring wheat (Triticum durumL.) cultivar ‘Inbar’ in 1986, and the hard red springwheat (Triticum aestmum L.) cultivar ‘Len’ in 1987.Nitrogen treatments consisted of all NO, or mixtures (75/25or 50/50) of NO₃ and NH₄. At maturity, plants were harvested,separated into leaves, stems, roots, and grain, and each partanalysed for dry matter and chemical composition Compared to plants receiving only NO₃ as the source of N, mixedN nutrition resulted in greater accumulation of whole plantreduced-N (49 to 108% more), phosphorus (38 to 69% more), andpotassium (25% more) for both cultivars. In all cases, plantsproduced higher grain yields (28% for Len to 78% for Inbar)when grown with mixed N nutrition than with only NO₃. The yieldincrease was not associated with heavier grains or more grainsper ear, but rather with an increase in the number of ear-bearingtillers per plant. For both cultivars, the higher yields withmixed N resulted from the production of more total biomass (36to 76%) as the partitioning of dry matter between plant partswas not altered by N treatment. Under the hydroponic conditionsof this experiment, the utilization of both NO₃ and NH₄ resultedin greater growth, nutrient absorption, and yield than NO₃ alone,which was primarily associated with an enhancement in tillerdevelopment Triticum aestivum L., Triticum durum L., spring wheat, hydroponics, ammonium nutrition, nitrate nutrition, tillering, yield components, partitioning