Yield, Quality, and Sucrose Recovery from Sugarbeet Root and Crown1
R. c. Z I ELKE2
Receivedfor publication May 15, 1973
Since the advent of mechanical harvesting in the late 1940's, all increasing amount ofcrown tissue has been processed by the factories. The introduction of crowns into factory processes has long been considered undesirable because they contain higher concentrations of impurities than roots and, consequently, further reduce crystallization of sucrose from thejuice (6,12)3. Data compiled from the late 1800's by Stehlik (14) established that the crown con tained a concentration of sucrose only somewhat less than that of the root. It would be desirable if the sucrose in the crown could be crystallized at a net gain to factory operations instead of losing it to molasses production. Early investigators lacked formulae and analyses to determine whether sucrose could be recove red if crowns were processed. Now formulae are available for calculating sucrose recovery from simulated factory operations (2 , 15) and improvements have been made in the laboratory analyses of certain juice impurities. The objectives of these studies were to ascertain the relationship between root and crown in yield sucrose content, juice purity, and recovery ofsucrose. Nitrogen fertiliza tion, harvest dates, plant popula tions, and varietal differences wen.: incorporated into the experiments because they affect sucrose recovery.
Methods and Materials
1967 field experiment A factorial split-split-plot design with six replications wa s arranged with two N levels serving as the main-unit treatment. The 24:lb/A rate of N was supplied by using 200 Ib/A of 12-6-6 4 as a row fertilizer at planting time. The 150-lb rate was the basic rate plus 126 Ib of addi tional N applied as ammonium nitrate on the soil surface at thinning time and cultivated into the soil. Additional amounts of P and K were uniformly applied before planting according to soil test recommenda tions. Beets were thinned to a uniform 120 plants per 100 feet o frow.
'Cooperative investigation by the; Agricultural Research Service, U. S. Department of Agricul ture and the Michigan Agricultural Experiment Station. Approved for publication as Journal article #6165, Michigan Agricultural Experiment Station. 'Research Agronomist, Agricultural Research Service, U. S. Department of Agr;culture, East Lansing. Michigan 48823 3i\umbers in parentheses refer LO literature cited. 'P alld K expressed on ox id e basis. VOL. 17, No.4, OCTOBL R 1973 333
Three cultivars of sugarbeet (Beta vulgaris L.), composing the subunit treatment, were planted on May 2 near Sebewaing, \1ichigan. The cultivars were 'SP63194-0' (No. 1 in the tables), an open-pol linated monogerm; '02 clone' (r\o. 2), an open-pollinated multigerm; and 'CS H20' (No.3), a commercial monogerm hybrid. Each plot was four rows wide (28-inch rows) and 76 feet long. One interior-posi tioned row was randomly divided into four sections for harvest. A 13-foot sample of beets was harvested from each culrivar on Sept. 14, Oct. 5, Oct. 24, and Nov. 7 for yield and laboratory analyses.
1968 f ield experiment A factorial design involving two"\: levels, two in-row spacings of beets, two cultivars, and two harvest dates was used with six replica tions. Nitrogen levels were arranged as a split-plot and the remaining eight treatment combinations were randomly distributed within each split-plot level. Each treatment was 18 feet long and six rows wide (28-inch rows). Two rates of ,30 and 150 lbl A, were established. Row fertilizer (500 lbl A of6-24-12)4 supplied the basic rate. An additional 120 lb ofN was applied as in 1967 to provide the 150-lb rate. Because the P and K soil test readings were high, no additional amounts of these two nutrients were applied. Row fertilizer was placed 2 to 3 inches below the seed both years. Two in-row spacings of beets were esta blished to represent differences in commercial beet stands. At harvest, the narrow plant spacing averaged 9.8 inches (122 plants per 100 feet ofrow) and the wide spacing 15.4 inches (78 plants). Two hybrid cultivars planted on April 30 near Saginaw, Michigan used the Fl monogerm female SL(l29x 133)cms. 'SP6322-0' was the pollinator for cultivar No. 3 (US H20) and 02 clone for cultivar No.4. The harvest dates were Se pt. 23 and Oct. 21 . Seventeen feet of row were harvested from each plot with the wide in-row spaEing and 13.5 feet from each with narrow spacing to provide] 4 to 16 beets for yield and laboratory analyses.
Laboratory analyses and techniques Beets without leaf blades and petioles were delivered to the laboratory within 4 hours after harvesting. The crowns were prepared as suggested by Jorritsma and Oldfield (8) , i.e., petiole stubs and leaf buds were removed with a knife to expose the white crown tissue. The beets were washed free of adhering soil and air-dried briefly. Crowns were separated from the roots at the lowest original leaf (7) and both parts weighed. Brei samples were collected by cutting each root in half 334 JOURNA L OF THJ:: A. S. S. B. T. with a single-bladed saw (16-in. diam.). Crowns were quartered with the same saw to obtain sufficient brei. Juice samples were obtained, quickly frozen in a dry ice-alcohol bath, and later clarified and analyzed according to the DFS method (3). Apparent sucrose contents of brei and clarified juice were deter mined polarimetrically. Analyses for reducing sugars and raffinose were made to correct apparent sucrose, clear juice purity (eJP), and recoverable sucrose as outlined in (4, 16).
Results and Discussion
Yield and proportions of root and crown Root yields (exclusive ofcrown) were significantly different within the harvest date and cultivar treatments but did not differ for beet spacings or nitrogen levels (Table 1) . The lack of response in root yield to the high N levels reported in the last decade (1, 10, 11, 13) may be attributed to the greater residual N levels and total fertility now found in soils of beet-growing areas of Michigan and Ohio. Crowns accounted for 22% ofthe total yield harvested in 1967 and 17% in 1968. These percentages cannot be compared with commercial factory crown tare values because the roots in our tests wer-e separated from the crowns with a straight cut across the root instead of the usual cone-shaped cut. All treatments differed significantly for yield of crown. Crown material each year was about 1.5 tons per acre (35%) more at the high N levels than at the low N levels. The overall crown/root ratios (0.29 in 1967 and 0.21 in 1968) show that a sizable portion of the total growth can be attributed to crowns. The difference between the two ratios (0.08) suggests that environ mental effects condition the development of root and crown in respect to each other. Another indication of environmental effects is that the crown/root ratio was higher in 1967, when the overall stand of beets was denser (120 per 100 feet) rather than in 1968, when stands were less dense (100 per 100 feet). Results of the spacing treatment in 1968 indicate that the ratio should be higher when beets are spaced farther apart. In addition to environmental effects, the crownlroot ratio varied significantly with all treatments except harvest dates. The greatest divergence in ratios for each year was between the two N levels (0 .09 in 1967 and 0.06 in 1968) and reflects, primarily, the large increase in crown yield at high N with little increase in root yield. Fort and Stout (5) and Loomis and Ulrich (9) also reported large increases in crown yield at high N levels. Growth rates of the root and crown are apparently proportional during the harvest season because the crownlroot ratio did not change significantly between mid-September and mid-Novem ber in 1967. < 0 r
.-..J Table I.-Effect of nitrogen, plant spacing, cultivar, and harvest date on yield of sugarbeet root and crown. Z 1967 Yield Crown/Root 1968 Yield Crown/Root 0 Treatment Root Crown Total Ratio Treatment Root Crown Total Ratio .... ------Tons/Acre ------Tons/Acre ------0 n N Applied N Applied .., 0.18 0 241b/A 17.9 4.4 22.3 0.25 30lblA 17.9 3.3 21.2 to 150lb/A 17.5 5.9 23.4 0.34 150lb/A 18.9 4.6' 23.5 0.24 '":>:J ns ** •• ns • * * • Spacing
(>:) (>:) <.n 336 JOCRNAL OF THE A. S. S. B. T.
The technique for topping experimental beets should be thor oughly considered before harvesting begins because the proportion of crown to root, sucrose content, andjuice purity can be easily influenced by treatments and location (year) effects.
SUCTOse content Average sucrose content for root and crown differed by 2.0 percentage points in 1967 and 1.7 in 1968 but the weighted average sucrose contents for the whole beet were only 0.4 lower than for roots alone (Table 2) . Thus, sucrose content for the whole beet was not seriously lowered by the addition of crown material. Overall crown/root sucrose content ratios (0.88 both years) indi cate a stable, environmentally independent relationship between the root and crown for sucrose content. :-.litrogen treatments did not affect the crown/root ratio, which is in contrast to their effect on the yield ratio. Sucrose contents of the root and crown were significantly lower at the high N level. Contents were 0.7 percentage point less in 1967 and about 1.0 less in 1968. Loomis and Urich (9) reported greater differ ences in sucrose content between the root and crown at low N levels when beets were grown in pots but differences between the root and crown were the same in both of my tests. During the harvest season, sucrose increased in both the root and crown in nearly a proportional manner as evidenced by the narrow range in crown/root ratios.
Clear juice purity (CJP) CJP for roots averaged 94.3 in 1967 and 93.8 in 1968 (Table 3). Purities for crowns were lower than for roots in both tests, but those for the whole beet were well within the range needed for processing fresh beets. Crown CJP/root CJP indicated only a small range in ratios (0.946 to 0.966) for the two tests. Roots and crowns had lower CJP at the high N level than at the low N. High N, however, caused a proportionately greater concentration of impurities in the crown than in the root as compared with low N. In contrast, a previous report indicated greater differences between the root and crown at a low N level (9). In 1967, CJP of root and crown increased 1.9 and 1.6 percentage points, respectively, between the first two harvest dates; but after the second harvest, CJP tended to stabilize. Substantial raffinose and invert corrections were made on apparent sucrose and on apparent CJP in 1967 as harvest dates pro . '-;'
" ' :;" < C r
,:>~~.. , :,t,':' :-.J Table 2'-7Eff~~t of nitrogen, plant spacing, cultivar, and harvest date on sucrose content of sugarbeet root and crown. Z 1967 -~,: :/ .. ~" f!:;" Sucrose Content CrownJRoot 1968 Sucrose Content CrownJRoot ~ Treatment Root Crown WtdAvg Ratio Treatment Root Crown WtdAvg Ratio .... 0 - ) ------Percent ------ ------ Percent - ------ n N Applied ~~~~.~ N Applied -l 0 241b1A 16.6 !]j , .~ : . 14 .6 16.2 0.88 30lblA 15.2 13 .6 15.0 0.89 M 150lb/A i5.9 13.9 15,4 0.87 150lb/A 14.2 12,4 13.8 0.87 :>0 ," ** ** ns ** ** ** ns vo vo --J <..>:> <..>:> 00 Table 3.-Effect of nitrogen, plant spacing, cultivar, and harvest date on clear juice purity (CJP) of sugarbeet root and crown. 1967 CJP 1968 CJP Treatment Root Crown WtdAyg 1 reatment Root Crown WtdAvg N Applied N Applied 24 1b/A 94.8 90.6 94.0 30 lb/A 94.5 90.9 93.9 150lb/A 93.8 890 92.6 150lb/A 93 1 89.2_. 92.3 .. • * •• •• •• Spacing ~ 94.2 90.1 93.5 15.4 in. 934 90.0 92.8 .. ns .. Culti var Culli var I 94.U 90.2 93. 1 3 93.8 89.6 93.0 2 94.1 89.4 93.2 4 938 90.5 93.2 3 948 89.7 93.6 ns ** ns •• -. Ha rvesl Harvest Sept 14 92.9 88.9 92.0 Sept 23 93.6 89.3 92.8 t. 0 OCl.5 94.8 90.5 93.8 OCL 2 1 94.0 90.8 934 c:: Oct. 24 94.7 897 93.6 .. *B ** Z Nov. 7 94.8 90.1 93_.. 7 :>" _. *. r 0 Test Avg. 94.3 89.8 93.3 Test Avg. 93.8 90.1 Y3 . 1 ." -l " •• F test significa nt al the 5 and I percent levels of probability. res pectivelv. :t ns F test not sign ifica nt t"l > (fJ (fJ 1:0 :-l VOL. 17, No.4, OCTOBER 1973 33 \:J gressed. For example, apparent CJP values for roots were adjusted downward by 1.4 percentage points and for crowns by 2.2 percentage points for the third harvest in 1967. On the comparable date (late October) in 1968, root values were reduced an average of 0.6 per centage points and crown values by 0.8 percentage points. The correc tions were due to increases in raffinose concentration during colder weather. Corrections for the September harvests were small in 1967 and negligible in 1968. Recoverable SUCTOse per ton (RSPT) 5 Crowns yielded 226 pounds of RSPT in 1967 and 208 pounds in 1968 (Table 4). The RSPT for roots was about 50 pounds higher than for crowns both years. Weighted average RSPT yields, which include the proportionate weight ofcrowns per ton of whole beets sliced, were only 10 to 15 pounds less than for roots alone. The high N level lowered the overall beet quality. Roots grown at high ;\I produced 18 pounds less RSPT in 1967 and 26 pounds less in 1968 and crowns produced 20 pounds less in 1967 and 27 less in 1968. The RSPT of roots and of crowns increased more between the two harvests in 1968 than between any two harvest dates in 1967. A period of rainy weather in early October 1967 resulted jn static sucrose ac cumulation and RSPT did not increase for the last two harvest dates. ;\Iitrogen x harvest date interactions for roots were significant both years. RSPT from roots was considerably less (27 pounds in 1967 and 26 pounds in 1968) at high than at low N for the first harvest each year. Differences between low and high \I on other dates both years were about 15 pounds per ton. Thus, roots accumulate less sugar at high 1\ levels than at low N, especially in the early harvest season. A nitrogen x cultivar interaction in 1967 showed that cultivars differ in sensitivity to high N. Sucrose per ton was 27 pounds lowe,- at high N as compared with low N for cultivar 2, 17 pounds for cultivar 3, and only 10 pounds for cultivar 1. Recoverable SUCTOse per acre (RSPA) Ofthe total RSPA produced, crowns contributed 1160 pounds per acre in 1967 and 801 pounds in 1968 (Table 5). The respective average percentage contributions of 19% and 14% from crowns were slightly lower than the percentage weight contributions of 22% and 17% from crowns because of the lower quality inherent in the crown material. The RSP A from roots was 415 pounds greater at the low ~ level than at high N in 1967 and 189 pounds greater in 1968. Sucrose yields from crowns were higher both years at high 1\ because of the large increases in crown weight. Total RSP A was, however, not significantly different for the two N levels either year. 'The term "recoverable" as used in this paper refers solely to white crystallized sugar. uo..,. o Table 4.-Effect ofnitrogen, plant spacing, cultivar, and harvest date on recoverable sucrose per ton (RSPT) ofsugarbeet root and crown. Treatment Root Crown WtGAvg Treatment Root Crown WtdAvg Lb------Lb------ N Applied N Applied 24 1b1A 296 236 284 30lb/A 270 221 262 150 lblA 278 216 262 150lb/A 244 194 234 •• •• •• ** •• " Spacing 9.8 in. 262 209 253 15.4 in. 251 207 243 •• ns ., Cultivar Cultivar I 280 230 269 3 254 202 245 2 289 224 277 4 259 2 13 25 1 3 290 224 274 ns ,. •• ' •• • •• 0 Harvest Harvest c Sept. 14 268 220 258 Sept. 23 237 184 227 z '";!> Oct. 5 290 229 276 Oct. 21 276 232 269 r- Oct. 24 292 223 277 •• •• .* 0 " -.J Table 5.-Effect of nitrogen, plant spacing, cuitivar, and harvest date on recoverable sucrose per acre (RSPA) from sugarbeet root, crown, Z and whole beet. o 1967 RSPA 1968 RSPA *'" Treatment Root Crown Total Treatment Root Crown Total o n Lb ------Lb - -l o N Applied N Applied CO 5547 M 241b1A 5299 1047 6346 30 lblA 4818 729 ; ()O *'" 342 JOURNAL OF THE A. S. S. B. T. Sucrose yields increased substantially between the early and late harvest dates each year. In 1967, increases for both the root and crown were highest between the first two dates because of a complementary combination of increasing weight and RSPT. After October 5, in creases in weight of root and crown were more important than quality factors in increasing the RSPA. Summary Crowns contributed substantially to total sucrose yields. Average sucrose percentage in the crown was 14.2 in 1967 and 13.0 in 1968, and clear juice purities were about 90% both years. With these sucrose contents and juice purities, a ton ofcrowns would produce an average of217 pounds of recoverable sucrose. Harvesting 4 to 5 tons ofcrowns per acre would, then, increase the average RSPA by 800 to 1000 pounds. Nitrogen fertilization affected yields, sucrose content, and juice purity of roots and crowns. Although root yields were not significantly different at the two N levels in either test, 200 to 400 more pounds of sucrose per acre were produced in the root at the low N level because of higher sucrose and juice purity. Crown yields were 35% greater at the high N level both years; despite lower sucrose and juice purity, this gave 150 to 230 more pounds of sucrose per acre from crowns at the high N level than at the low. Total RSP A produced in either test did not differ significantly between low and high N. Delaying harvest from mid-September to late October both years increased root and crown yields, sucrose content, and juice purity and increased total RSPA approximately 1700 pounds. Spacing plants 9.8 and 15.4 inches apart in 1968 subtly but significantly affected roots and crowns. Root yields were not different at the two spacings but both sucrose content and clearjuice purity were higher at the close spacing. Yield of crowns was slightly higher at the wide spacing but sucrose content and juice purity were not different at the two spacings. The increase in crown weight at wide sp,!cing only partly offset the influence of higher root quality at close spacing so that total RSPA was slightly, but not significantly, higher at close spacing. The results indicated that cultivars or hybrids could be developed that would produce smaller proportions of crown to root. Even using different pollinators on the same Fl female altered the proportion of crown. Root yields would have to be increased, at least proportionately, to compensate for reduction in crown weight so that total RSPA can be maintained or increased. VOL. 17, No.4, OCTOBER 1973 343 Acknowledgments My sincere gratitude and appreciation is expressed to F. W. Snyder for his guidance and assistance on this research, which was completed as partial fulfillment for the Ph.D. degree. Also, the help of R. E. Wyse and M. G. Frakes in conducting the tests and performing essential laboratory determinations is gratefully acknowledged. Bibliography (I) BALDWIN, C. S. 1967. :--.Jitrogen and sugarbeet culture. Proe. 14th E. Reg. Meetings Am. Soc. Sugar Beet Techno!.; pp. 42-46. (2) CARRUTHERS, A., and J. F. T OLDFI ELD. 1962. Methods for the assess ment of beet quality. In : The Technological Va lue of the Sugar Beet. Elsevier Publishing Company, r\ew York, New York. (3) DEXTER, s. T, M. G. FRAKES, and F. W. S;-';YD ER. 1967. A rapid and practical method of determining extraclable white suga r as may be applied to the evaluation ofagronomic practices and grower deliveries in the sugar beer industry. J. Am. Soc. Sugar Beet Techno!. 14(5): 433-454. (4) DEXTER, S. T., M. G. FRAKES, and R. E. WYS E. 1969. Damage to sugar beet roots from various degrees o f wilting a l various temperatures. J. Am. Soc. Suga r Beet Techno!. 15(6):480-488. (5) FORT, C. A., and M. STOUT. 1948. Comparative composition of differ ent parts o f the sugar beet root. Proc. Am. Soc. Sugar Beet Techno!. 5:651-659. (6) HADDOCK , J. L., P. B. SMITH, A. R. DOW NIE, j. T ALEXA NDER , B. E. EASTOr-; , a nd VER NAL J £;\'S£:'I. 1959. The influence of cultural practices on the quality of suga r beets. J. Am. Soe. Sugar Beet Technol. 10(4): 290-301. (7) HAYWARD , H. E. 1938. The Structure of Economic Plants. The Mac Millan Company, "Jew York, "Jew York. (8) JORRITSMA , j., andj. F. T OLDFI ELD . 1969. F.ffect of sugar beet cultiva tion and extent of to pping on processing value. j. Institut Interna tional De Recherches Betteravieres 3(4):226-238. . (9) LOOMIS , R. S., and A. ULRICH. 1959. Response ofsugar beets to nitrogen depletion in relation to root size. j. Am. Soc. Sugar Beet Techno!. 10(6):499-512. (10) NICHOL, G. E. 1965. Progress report on the effect of nitrogen on yield, sucrose content, and purity ofsugar beets. Proe. 13th E. Reg. Meetings Am. Soc. Sugat· Beet Techno!.; pp. 50-57. (11) RUSSELL, FRED. 1965. The effect of varying rates of nitrogen on beet yields a nd sugar pro duction. Proc. 13th E. Reg. Meetings Am. Soc. Sugar Beet Technol.; pp. 44-49. (12) SKUDERA, A. W. 1952. The sugar beet industry. Proe. Am. Soc. Sugar Beet Techno!. 7:22-24. (13) SNY DER, F. W. 1967. Nitrogen as related to sugar beet quality and yield. Proc. 14th E. Reg. :vfeetings Am. Soc. Sugar Beet Techno!.; pp. 55-57. 344 JOURNAL OF THE A. S. S. B. T. (14) STEHLIK, V. 1923. Studies on the distribution of sugar in the beet at the time of harvest and in regard to individual differences. Zeitschrift Fur Die Zuckerindustrie Der Chechoslovakischen Republik. (Translated by H . A. Kuyper.) (15) Sugar Beet Research, 1964 Report. 1964. Determination of recoverable sugar using a formula proposed by the Great Western Sugat· Company Research Laboratory, Denver, Colorado. CSDA-ARS Bluebook, CR-4-64, p. 155. (16) WYSE, R. E. 1969. Storage of sugar beets: agronomic, physiological and quality aspects. Ph.D. Thesis. Michigan State University, E. Lansing, Michigan.