The dynamics of nitrogen uptake and its remobilization during the growth of sugar beet

Abstract

The uptake and distribution of N were examined in a series of sugar-beet crops grown on different sites (Broom's Barn, Suffolk and Trefloyne, Dyfed) or with 0 (N o ) or 125 kg N/ha (N m ) between 1978 and 1982. Depletion of soil N was followed in some years.Initial rates of N uptake in spring for the N 126 crops at Broom's Barn ranged from 2-3 kg/ha per day in 1980 to 5-8 kg/ha per day in 1981 and 1982 and at Trefloyne from 4-7 kg/ha per day in 1980 to 5-4 kg/ha per day in 1979. The initial phase of N uptake in N o crops was shorter and at Broom's Barn the rate ranged from 1-6 kg/ha per day in 1979 to 5-1 kg/ha per day in 1982. Crops with high initial uptake rates had somewhat greater shoot N concentrations. There was no relation between the initial uptake rates or the total N uptake and the amounts of mineral N in the soil at the start of rapid growth in June. Simulations of early crop growth coupled with analysis of changes in the total N in the crop-plus-soil system showed that the rate of N uptake by the N 125 crops was regulated by crop demand for N as determined by growth rate in 4 of the years and by soil supply in the 5th. The analysis of the crop-plus-soil N also showed that substantial losses of N occurred when the crop was actively growing in June and July in 1979 and 1980 due to excessive rainfall following early irrigations. There were serious consequences for N uptake, N concentration in developing leaves and the overall growth of these crops.N uptake rates in autumn ranged from no net uptake in 1979 and 1980 to 0-6 kg/ha per day in the other 3 years at Broom's Barn and 1-0 kg/ha per day at Trefloyne. Large amounts of N were remobilized from the shoot to sustain the growth of the storage root in years when uptakes from the soil in autumn were small. Remobilized N represented 80, 50 and 30 % of the net increase in storage-root N between the end of August and harvest in 1979, 1980 and 1981 respectively. The amounts remobilized from shoots ranged from 8 to 18 kg N/ha and may therefore also represent a source of amino-N impurities in harvested beet. An analysis of N in individual leaves showed that remobilized N probably originated from leaf protein and that remobilization started at full expansion rather than at the onset of leaf senescence, which was often many weeks later. INTRODUCTION8 U g a r b e e t i m P r o v e s vield > excessive use has deleterious effects on the quality of the harvested beet Greater use of nitrogen fertilizer has been a major that make the crop less profitable for both grower factor in increasing yields of British arable crops, and processor. In particular, beet given too much During the past 30 years, rates applied to cereals fertilizer N contains smaller concentrations of sugar have increased five-fold and those to potatoes and higher concentrations of a-amino nitrogen three-fold, whereas applications to sugar beet have compounds, both of which decrease the efficiency only doubled (Cooke, 1972). Nevertheless, there is of sucrose extraction. concern within the sugar industry...

Nutrient uptake by potato crops grown on two soils with contrasting physical properties

“…It is likely also to be a reflection of the rapid depletion of available nutrients in the upper layers of the soil (e.g. Armstrong et al, 1986;Millard and Robinson 1990).…”

Response of sugar beet (Beta vulgaris L.) yield and biochemical composition to elevated CO2 and temperature at two nitrogen applications

“…Elevated CO 2 often decreases the concentration of nitrogen-containing components in plants, and the response of sugar beet is important. Sugar beet accumulates glycinebetaine, a quaternary ammonium compound with an osmoregulatory role in halophytes, and compounds containing α-amino-N (amino acids predominantly) with a similar role which may also provide a means of buffering demand for and supply of N during growth (Armstrong et al 1986). These compounds interfere with commercial sucrose extraction (Lohaus, Burba & Heldt 1994) and its economics.…”

Agronomic consequences of potential management zones delineated on the basis of EM38DD measurements

“…This could be expected, as Armstrong et al . () reported that sugar beet plants might need to take up as much as 5 kg N ha −1 day −1 for rapid leaf expansion. Only a small amount (15–25 kg N ha −1 ) remained in all classes with overlapping ± 1 intervals.…”