Abstract
Late-season N application through foliar spraying is recognized as an efficient agronomic practice for improving grain quality in common wheat, although the major part of N is still supplied by soil fertilization. This study assessed the impact of various N doses entirely applied by repeated foliar sprayings on wheat growth, yield and quality, in comparison with conventional soil fertilization management with a recommended dose of 160 kg N ha−1 as ammonium nitrate (C-M). Doses of 96, 104 and 120 kg N ha−1 as both UAN (urea-ammonium-nitrate) and urea applied by foliar spraying were evaluated in a 2-year field trial in Northern Italy in a silty loam soil with 1.7% organic matter. Here, it was demonstrated that the canopy greenness was similar in all treatments, with slight grain yield increases by the lowest foliar N dose vs. C-M. The higher N foliar doses mainly improved the grain protein content and both high- and low-molecular-weight glutenin subunits (HMW-GS, LMW-GS), particularly with urea. It is concluded that in our fertile soil, managing N fertilization exclusively through foliar spraying is feasible without compromising grain yield and ameliorating quality at the same time. Improved nutrient use efficiency and beneficial environmental effects are also expected by reducing the nitrogen load on the agricultural fields by 25–40%.
Highlights
Foliar fertilization consists in the application—via spraying—of nutrients to the crop canopy, allowing their absorption by leaves and stems [1]
We evaluated the thousand seed weight (TSW) by weighing 1000 kernel samples obtained from a counting machine (Numigral Seed Counter, Chopin Technologies, Villeneuvela-Garenne, France), and the testing weight through Near-InfraRed Spectroscopy (NIRS) technology with Infratec-1241 instrumentation (Foss Analytical, Hillerød, Denmark)
Our results indicate that reduced N doses sprayed on the canopy, slightly altering leaf chlorophyll content and possibly photosynthesis compared to soil application, did not compromise the final yield and grain quality, to what was previously reported by other authors [22,29]
Summary
Foliar fertilization consists in the application—via spraying—of nutrients to the crop canopy, allowing their absorption by leaves and stems [1]. This agronomic practice was firstly applied in the early 1900s and mainly limited to micronutrient application in highvalue horticultural crops such as potato and tomato [2]. Foliar fertilization is able to alleviate nutrient deficiency faster than soil application [2,4] It can be successfully used for both macro- and micronutrients, with large benefits for low-mobile elements in dry soils and with poor root growth [5,6,7]. Following the high leaf absorption, improved fertilization efficiency and reduced nutrient losses are expected, with nitrogen [9]
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