STUDY OF EARLY SUGAR BEET NITROGEN UPTAKE

SUMMARY Although much work has been carried out on nitrogen absorption by sugar beet during the advanced stages of vegetation, very few studies have focused on early absorption of nitrogen by the crop Field plots were carried out during two years in France to better characterise early nitrogen absorption Nitrogen was brought at rates of 100, 200 and 300 kg/ha in irrigated (drop by drop) and non­ irrigated plots, three weeks before sowing. It was also added at a rate of 100 kg/ ha just before sowing in localised and generalised modes Seedling emergence was observed and leaf areas were measured from emergence to the 16 leaf stage Growth curves were established by sampling beets at different stages during the crop Time was calculated as thermal time (base 3.5 oc) from 80% emergence. Nitrogen concentrations in the 0-60 em layers in the ground and the roots of the beets were also measured The results showed early differentiation between the various nitrogen treatments regarding the level of fresh and dry matter and regarding the level of the quantity of nitrogen in the leaves and roots The drop by drop irrigated beets showed faster growth and higher absorption of qnitrogen. These results could be used to define nitrogen application methods, making it possible to reduce the nitrogen amount brought before sowing without decreasing growth and productivity.