Dynamics of nitrogen uptake and root quality in sugarbeet
1997
Mambelli, S. | Dal Rio, M.P. | Grandi, S. | Amaducci, M.T. | Venturi, G. (Bologna Univ. (Italy). Dept. of Agronomy)
Nitrogen is one of the essential nutrient involved in growth, yield and quality of sugarbeet crops. It enhances the interception of radiation by increasing leaf expansion thus enabling canopies to produce more total dry matter and sugar. On the other end, excessive uptakes of N result in higher accumulation of alpha-amino nitrogen compounds into the root paralleled, occasionally, by a reduced concentration of sucrose. In several sites and years, different fertilization practices were examined for dynamics of nitrogen crop uptake and accumulation into storage roots. Depletion of soil nitrogen along the soil profile was also monitored from sowing to harvest. Crop uptake patterns followed different trends during the growing seasons and final values ranged from around 200 up to more than 300 kg per ha. Initial phase of uptake, until mid-growing season, was always rapid and was regulated by crop demand. Later uptakes were mainly determined by soil supply thus varying with site and season. Biomass and sugar yield were linearly related to nitrogen supply only after the early stages of growth, frequently 80-90 days after sowing. Usual fertilization practices resulted in poorer root quality and substantial losses of nitrates through leaching. To produce recommendations to optimize the nitrogen nutrition of sugarbeet it seems particularly important to quantify the ability of the soil to supply nitrogen.
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