A. P. Draycott

Nitrogen requirement of sugar beet grown on mineral soils

The effect of nitrogen fertilizer on the yield of sugar beet was tested in 170 experiments done between 1957 and 1966; results of 88 experiments, some testing five and six amounts of N, have not previously been published. On most sites, nitrogen increased sugar yields sharply and almost linearly up to an optimum beyond which yield changed little or decreased only slightly up to 1·8 cwt N/acre, the largest amount tested. In the two series of experiments giving most information, the mean increase from sub-optimal amounts of N was 2·5 cwt sugar/0·1 cwt N/acre. Usually 0·4–0·8 cwt N/acre was enough for maximum yield; more was needed on a few sites and on about a fifth of them nitrogen fertilizer was not needed. In 7 of the 10 years, the average optimum was 0·6–0·8 cwt N/acre; less was needed in the other years, the driest three years of the decade. In most, though not all, years, site-to-site differences in response between 0·9 and 1·8 cwt N/acre were no greater than could be expected from experimental error alone; much of the apparent difference in response between seasons were also attributable to this source. After taking account of experimental error, there were substantial between-site differences in response to amounts of N up to 0·9 cwt/acre, but attempts to explain them in terms of weather, soil and husbandry factors had little success. There was slight evidence of diminished responses to N where sugar beet followed crops other than cereals, and of responses somewhat greater than average on Chalky Boulder Clay soils of the Hanslope and Stretham Series; no other relationships were large or consistent enough to be useful for prediction. As between-site differences in response are largely unpredictable, and because a grower risks much greater crop losses by applying too little N than by applying too much, the recommended dressing is 1·0 cwt N/acre, substantially more than is needed, on the average, to obtain maximum yield. More N should be given on soils of the Hanslope and Stretham Series and on light sands poor in organic matter; less need be applied where crop residues are likely to supply much nitrogen.

Effects of nitrogen fertilizer, plant population and irrigation on sugar beet: I. Yields

Five experiments (1965–9) on calcareous sandy loam tested all combinations of four amounts of nitrogen (0–1·8 cwt/acre N) and four plant populations (8000–54 000 plants/ acre) given to sugar beet grown with and without irrigation. On average, nitrogen and plant population influenced yields greatly but irrigation relatively little. In all years between 0·6 and 1·2 cwt/acre N and between 17000 and 32000 plants/acre gave largest sugar yield. Giving more nitrogen or increasing the plant population neither increased nor decreased sugar yield much in any year. Irrigation was beneficial in only two out of five years. Sugar yield was linearly related to root dry-matter yield. Although total dry matter was greatest when the largest plant population was given the largest dressing of nitrogen and irrigation, the proportion of dry matter in the roots was decreased by all three factors.

Response by sugar beet to irrigation, 1965–75

Sugar yield increases from irrigation in 19 experiments on a sandy-loam soil at Brooms Barn over an 11-year period were examined in relation to rainfall and to both potential and measured soil moisture deficit. Irrigation increased average yield from 7·6 to 8·3 t sugar/ha and in six of the years significantly increased yield by more than 1 t sugar/ha (15%). The experiments also tested plant density, nitrogen, harvest date and time and amount of irrigation. Without irrigation, maximum sugar yield was from a density of 74000 plants/ha but larger densities gave slightly more yield when irrigated. Irrigation affected the magnitude of response to nitrogen but 100 kg N/ha gave the most profitable yield increase, both with and without irrigation. Yield increases of about 1 t sugar/ha (15%) between early and late harvesting were also independent of irrigation. Early irrigation of 25 mm and 50 mm in June and July respectively increased yield in 4 of the 5 years but in all years applications in late summer did not increase sugar yield. The main factors controlling the yield response to irrigation were period and size of deficit. The soil type and summer rainfall at Brooms Barn were compared with those in 36 other experiments at five localities between 1947 and 1973; yield increases at Brooms Barn were smaller, probably because the others were on lighter soils.

Changes in the weight and quality of sugarbeet ( Beta vulgaris ) roots in storage clamps on farms

The changes in weight and quality of sugarbeet roots stored in 18 clamps, mostly in eastern England during the winters of 1992/93 to 1994/95, were studied on farms using best commercial practice. Storage usually started in early December, at about the last recommended date of harvesting, and continued until the end of the beet-processing campaign at the local sugar factory (usually in February). Random samples of beet, in open-weave nets, were either analysed at the outset or were buried in a predetermined pattern in the clamp for up to 84 days. Periodically, samples were removed from the clamps for analysis. Beet weight hardly changed but sugar was lost as a reduction in sugar concentration: this declined at c . 0·02% per day. The concentration of reducing sugars, which are important impurities, increased fourfold during storage. Most other beet quality parameters remained unchanged. Sugar and adjusted weight was lost at 0·143 and 0·187% per day respectively. This relationship was highly significant, but a relationship between sugar loss and accumulated thermal time (0·0188% per °C day) accounted for more of the variation (73%). Temperature changes within the clamps, and the differences between clamps in accumulated thermal time, were not predictable. Some clamp insulation materials appear to allow more heat to accumulate than is desirable.

Response by sugar beet to various amounts and times of application of sodium chloride fertilizer in relation to soil type

Two-thirds of the sugar-beet crop in the U.K. receives sodium chloride as part of the fertilizer programme. It is well known that the crop responds profitably on sandy soils which contain relatively little sodium and potassium, and most of these fields now receive sodium chloride. Few crops on clays, silts and organic soils are treated because the value of sodium chloride has never been clearly defined. Thus 36 field experiments were made over the 5 years 1975–9 on contrasting soil types testing five amounts of sodium chloride, 0, 100, 200, 400 and 800 kg/ha, and at two times, either autumn or spring. All the fields chosen were in continuous arable rotations where potassium chloride was applied regularly and nearly all the soils contained more than 120 mg exchangeable K/l. Sodium chloride (400 kg/ha costing £12) increased sugar yield on average by about 0·2 t/ha (worth £40) on the mineral soils but no crop responded on organic soil. Exchangeable soil sodium concentration was not a good predictive test of which fields would respond but all the large increases in yield were on fields with less than 20 mg Na/1. A few crops responded on soils with 20–40 mg Na/1 but no crop responded on soil with more than 40 mg Na/1. A survey of sodium concentrations in 800 soils showed that most mineral soils contained less than 40 mg Na/1 so it is suggested that all mineral soils regardless of texture should receive 400 kg sodium chloride/ha. Crops on organic soils did not respond to sodium chloride because the soils already contained sufficient. Autumn and spring applications of sodium chloride on mineral soils gave similar increases in yield provided the fertilizer was not applied just before sowing, when in 2 years it decreased plant establishment. This effect was particularly damaging on clays and silts where it is frequently difficult for other reasons to obtain good seed beds and full establishment. It is concluded that sodium-containing fertilizers should always be applied well ahead of sowing to allow rainfall and cultivations to incorporate them into the soil. On clays and silts it is suggested that they should be applied before ploughing to avoid soil compaction but on sands there may be advantages in post-ploughing application.

The effect of soil type and related factors on sugar beet yield

Yields of sugar and responses to fertilizers were determined in about 400 fertilizer experiments on farms throughout the sugar-beet growing areas of Britain during 14 years from 1957 to 1970. The soil at each experimental site was described and classified and the records of the experiments have been examined to determine which properties of the soil influence sugar yield. The effect of year, rainfall, elevation, region and other factors such as sowing and harvesting date were also investigated. Year-to-year variation accounted for 20 % of all variation in yield; increasing amounts of rainfall during the growing season appeared to decrease yield. There was a significant long-term trend of increasing sugar yield from the experiments of 0·042 t/ha/year. The experimental yields closely followed national yields each year but were always greater. Delay in sowing and early harvesting depressed yield by 0–02 and 0·01 t sugar/ ha/day respectively. Yields in Scotland (average 5·23 t/ha) were approximately 1·4 t/ha less than in England and Wales, but there were no evident regional differences within England and Wales. Soil regarded as moderately drained yielded better than either well-drained or imperfectly drained soil, which in turn yielded better than droughty and poorly drained soil. The difference in the adjusted yield between drainage classes was 1·0 t/ha. Surprisingly, topsoil texture had no consistent effect on mean yield (as distinct from response to fertilizer). Subsoil texture, however, had an appreciable effect, the crop on sandy subsoil and chalk or limestone yielding poorly whilst that on silt or peat yielded best. The range of differences in sugar yield due to subsoil texture was almost 2 t/ha. Yields were also examined in relation to soil profile type. Broad division into major soil groups gave meaningful differences but fine division by soil series was only useful for the 11 series on which at least ten experiments had been made. The crop yielded most sugar on gleyed calcareous soils, peats and humic gleys, and least on rendzinas and brown calcareous soils. Responses to nitrogen and potassium but not to phosphorus were affected by both topsoil and subsoil texture. Nitrogen and potassium both increased yield most on sandy soils and least on fine silts and peats. The morphology, chemical and physical condition of soil clearly affect sugar yield greatly and further research is needed in experiments planned specifically to measure their influence and provide more precise guidance for selecting the best land for the crop.

Effects of nitrogen fertilizer, plant population and irrigation on sugar beet: III. Water consumption

A neutron moderation meter was used to measure soil moisture 0–4 feet deep in plots of sugar beet carrying two plant populations (8800 and 54000 plants/acre), each with and without irrigation. Recordings began in April or May in each of three years (1967–9) after sowing the crop and continued at 1 or 2-;week intervals until harvest in October. The measured soil moisture deficits were very similar to potential deficits calculated from meteorological measurements. This indicates that the crop could extract the water needed for transpiration from the soil even when the deficits were quite large (more than 5 in in 1967), which probably explains the small response to irrigation by sugar beet in England. When the soil moisture deficit increased rapidly early during the season (1967), the crop extracted water from the soil by exhausting the available water from progressively deeper horizons, whereas when the deficit increased rapidly late during the season (1969) water was still being extracted from all horizons until harvest. Both decreasing the plant population and irrigating decreased the amount of water used from depth in the profile every year. The total amount of water used (evaporation plus transpiration), on average, from soil reserves and rainfall, was 12·2 in by the small population and 13·4 in by the large population. When irrigated, the consumption increased to 14·2 and 15·4 in. respectively. The difference in usage between populations was almost entirely from the difference in leaf cover early during the season. The water consumption in 1968, when the summer was wet, was only two-thirds of that in 1967 and 1969 when the summers were drier.

The effect of time of sowing and harvesting on growth, yield and nitrogen fertilizer requirement of sugar beet

Four field experiments (1968–71) investigated the effect of changing the length of the growing period on the nitrogen fertilizer requirement of sugar beet. The crop was sown on three occasions (March–May), harvested on three occasions (September–December) and given four amounts of fertilizer (0–225 kg N/ha). Plant samples were analysed at several stages of growth (1969–71) in an attempt to predict the amount of nitrogen fertilizer needed for maximum sugar yield and also at the end of the season to determine the nitrogen uptake. Increasing the length of the growing period increased sugar yield greatly but the amount of nitrogen fertilizer needed for maximum sugar yield was unchanged. The crop given the largest dressing of nitrogen and with the longest growing period contained most total nitrogen, but in every experiment, giving more than 75 kg N/ha neither increased nor decreased the sugar yield significantly. As a result of the small variations in nitrogen requirement, the plant analyses during the growing season were of little value in predicting the needs of the crop.

Comparisons of kieserite and calcined magnesite for sugar beet grown on sandy soils

Twenty-three experiments between 1968 and 1971 compared the effect of no magnesium, 50 and 100 kg/ha magnesium as kieserite and 100 and 200 kg/ha magnesium as calcined magnesite, on yield and magnesium uptake by sugar beet. On average, 100 kg/ha magnesium as kieserite increased the mean sugar yield of 7·55 t/ha by 0·17 t/ha whereas 200 kg/ha magnesium as calcined magnesite increased it by only 0·08 t/ha; on fields with less than 15 ppm exchangeable magnesium the magnesium fertilizers increased sugar yield by 0·34 and 0·10 t/ha respectively and there was no response to either fertilizer when the soil contained more than 25 ppm of exchangeable magnesium. 100 kg/ha magnesium as kieserite or calcined magnesite increased magnesium in the dry matter of tops by 0·091 and 0·040% and of roots by 0·013 and 0·004% respectively. Giving 100 kg/ha magnesium as kieserite or calcined magnesite increased uptake of the element in August by 5·1 and 2·6 kg/ha respectively. Differences in soil pH did not influence the uptake of magnesium from kieserite but they greatly affected uptake from calcined magnesite. On the slightly acid soils, the fertilizers were almost equally effective but at pH > 7·6 little magnesium was taken up from calcined magnesite. Glasshouse experiments showed that grinding the calcined magnesite increased the availability of the magnesium.

The effects of magnesium fertilizers on yield and chemical composition of sugar beet

Nineteen experiments were made between 1964 and 1967 on fields where previous sugar beet crops showed symptoms of magnesium deficiency. None, 2·5 or 5 cwt/acre kieserite or 20 cwt/acre dolomitic limestone were tested in a factorial design with none or 3 cwt/acre agricultural salt (crude sodium chloride), and 0.8 or 1.2 cwt/acre nitrogen as ‘Nitro-Chalk’. Additional plots tested kainit (7 cwt/acre) and a large dressing of potash (2 cwt/acre) as muriate of potash. Kieserite and dolomitic limestone increased sugar yield and the most effective dressing was 5 cwt/acre kieserite, which gave 3·1 cwt/acre more sugar than the crop without magnesium fertilizer. Agricultural salt and the larger dressing of nitrogen were profitable, and neither interacted with magnesium on average; the large dressing of potash also increased yield. The magnesium in the kainit increased yield slightly, but the dressing tested supplied too little to satisfy the crops requirement of magnesium. Each year in late summer the percentage of plants showing magnesium-deficiency symptoms was recorded, and a sample of twenty-four plants harvested from each of the magnesium treatments and analysed. All the magnesium fertilizers increased the concentration of magnesium in leaves, petioles and roots, and also decreased the number of plants showing deficiency symptoms. The magnesium concentrations in plants grown without magnesium differed widely and were related both to the yield response to magnesium fertilizer and to the percentage of plants with deficiency symptoms. Both relationships showed a similar ‘transition zone’ from deficiency to adequate supply, for leaves this was 0·2–0·4% Mg, for petioles 0·1–0·2 Mg and for roots 0·075–0·125 % Mg in the dry matter.