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...

S U M M A R YIncorporation of large amounts of straw (8-15 t/ha dry matter) into the soil had no effect on the incidence of soil pests and diseases or sugarbeet seedling population densities in experiments performed over three seasons (1984/85 to 1986/87) in Suffolk. Straw incorporation had no effect on sugar yield at the recommended rate of nitrogen fertilizer application, but the sugar yield and nitrogen uptake were reduced in one year by the incorporation of straw when the rate of applied nitrogen was low. It is probable that incorporating straw reduced the amount of nitrogen leached over the winter; however, the longer-term implications of straw incorporation remain to be assessed.

SUMMARY The increase of leaf area index (L) was examined in a series of sugar‐beet crops grown on different sites (Broom's Barn, Suffolk and Trefloyne, Dyfed) or with different husbandry treatments (sowing dates and nitrogen rates) between 1978 and 1982. The development of L could be described as a function of thermal time using three parameters; DE, which was essentially an estimate of the thermal time required for crop establishment, and rHL and DL, the thermal rate and duration, respectively, of the increase of L. Variations in DE between seasons and with sowing date were small, but significant; they were attributed to factors affecting the condition of the seedbed. There were much larger variations in rHL, especially between seasons, sites and crops given different rates of nitrogen fertiliser, and there was a strong negative relationship between rHL and DL. Much of the variation in rHL was associated with differences in the concentrations of nitrogen in the lamina dry matter. Faster rates for rHL at Trefloyne than at Broom's Barn, and in the crop grown in 1982 as compared with other years, were also partly attributable to particularly warm conditions during the early development of some of the larger, faster‐growing leaves within the canopy. The wider application of the relationships established from these experiments was tested with data from a series of crops grown on other sites between 1960 and 1962. The relationships held particularly well for beet grown on soils with high water‐holding capacity but not for those on soils of low water‐holding capacity.

SUMMARYThe use of the correct N dressing for beet is important, as any excess decreases juice purity and profit, and may decrease sugar yield, but no analytical method will at present predict the best dressing in any particular field. The concentration of nitrate in leaves and petioles of beet was determined to test if it would determine the need for top-dressings of N. Beet on seventeen field trials in 3 years testing N were sampled. Nitrate in a wet tissue extract was determined by reducing to ammonia with titanous sulphate and subsequent distillation.The petiole nitrate concentration decreased sharply with time, from around 1000 ppm in wet tissue in early June to less than 100 ppm in early September. The nitrate concentrations were closely related to nitrogen dressing, and the rapid decline in concentration was decreased by top-dressings. Comparison of samples taken in June showed that most of the variation between the experiments could be accounted for by the different ages of the plants. Sodium fertilizer had no effect on nitrate content.Petiole nitrate was inversely related to juice purity and sugar concentration, especially when the nitrate content exceeded 700 ppm in June.On average, petiole nitrate concentrations about 800 ppm in June were associated with the largest sugar yields, but the content could not be used to predict nitrogen top-dressing requirement accurately at individual sites.Measuring NO3-N cannot at present be recommended as a method for deciding how much nitrogen fertilizer to use, but it has value for detecting severe deficiencies and in research.

S U M M A R YField experiments in 1987 and 1988 on peaty-loam, Mn-deficient soils of the Adventurers series in Cambridgeshire, UK, tested the response of sugarbeet to three forms of manganese fertilizer supplied as foliar sprays. The influence of a wetter and an adjuvant on manganese absorption and growth was also investigated.Cutonic and chelated forms of Mn, when applied at standard rates, were inefficient at increasing Mn concentrations in plants and alleviating deficiency symptoms during early summer. Mn concentrations in foliage increased rapidly after spraying with manganese sulphate, and most of the deficiency symptoms disappeared. These benefits were usually enhanced when manganese sulphate sprays were used with an adjuvant.Averaged over both years, yield without Mn was 8-83 t sugar/ha; the largest yield, 9-56 t/ha, was obtained with manganese sulphate plus adjuvant. Smaller benefits were obtained with the other forms of Mn. The adjuvant, when used with chelated Mn, appeared to depress sugar yields in both years. The likelihood of reducing the number of sprays required to control Mn deficiency on Fen soils was improved by using an adjuvant with manganous sulphate sprays.