EFFECT OF SUGAR BEET SEED TREATMENTS ON THE COURSE OF FIELD EMERGENCE, YIELD AND VARIABILITY

Aleksandra Orzeszko-Rywka¹, Sławomir Podlaski^2
1 Department of Plant Physiology, Warsaw University of Life Sciences, Poland
² Department of Plant Physiology, Warsaw University of Life Sciences – SGGW, Poland

ABSTRACT

Sugar beet seeds were treated by four different methods: rubbing, washing, priming and priming in combination with rubbing. Seeds were sown in a field for estimation of field emergence, yield and variability of single root weight. Each year the faster and more regular plant emergence was from primed or rubbed and primed seeds. Values of single root variability coefficient ranged from 53.3 to 73.9%. Priming and priming with rubbing decreased the coefficient of root weight variability by 7.1 to 9.2% compared to other methods. Root weight variability coefficient was strongly correlated to the time of field emergence. The shorter the mean time to emergence, the lower the root variability during the harvest. Sugar beet plants which emerged first produced the heaviest roots. Time and sequence of emergence influenced final root weight more than the mean distance to the neighbouring beets in the rows and their mean weight.

Key words: field emergence, seed treatment, sugar beet seed, root weight variability.

INTRODUCTION

Rubbing of the sugar beet pericarp, washing and pelleting of seeds are standard treatments used by seed companies. Priming is becoming the most common treatment improving sugar beet seed vigour. Seed characteristics such as density [15] or chemical composition [12] change during the process of priming. Seed germination and field emergence are faster and more uniform [11], resulting in uniform plant weight.

The dynamics of field emergence might influence both the development of single plants as well as the development of the crop. Buchse (1999) (according to Stibbe and Märländer [20]) concluded that the effect of intraspecific competition could mainly be explained by competition for light among plants of various sizes.

Early growth is exponential and the relative growth rate during early growth is only slightly affected by date of emergence, but the effect on total dry matter was highly significant [20]. Even two days' delay in emergence slightly decreases the yield by about 1.86 t·ha^-1. Differences in plant emergence time were significant with a delay of 12 or more days. This is connected with the fact that dry-matter production is proportional to the amount of solar radiation intercepted by the crop [1,18], which in turn is determined by the amount incident on the crop and leaf area index (LAI) or leaf cover of the ground. Dry-matter production is slow in spring because cool temperature and small, slow-growing leaves limit the interception of light [8,19].

Sugar beet seed is very often treated by seed companies before sowing. The sequence and exact method of treatment (like priming or pelleting) are patented and kept secret. Taking into account the fact cited in literature that seed germination can be improved after some standard seed treatments, experiments on determination of the influence of various complex methods of seed treatment on the course of field emergence, root yield and variation in single root weight of sugar beet were carried out.

MATERIAL AND METHODS

Seeds of diameter 3.5–4.0 mm of three sugar beet varieties, Kujawska, Lubelska and Jamona from the Polish company Kutnowska Hodowla Buraka Cukrowego were treated by four different methods: partial rubbing of the pericarp by use of rubbing paper (the seed diameter decreasing by 0.25 mm), seed washing at a temperature of 20ºC for two hours, priming with the solid matrix substance zeolith (patented method) and rubbing followed by priming. Different sugar beet varieties were chosen in order to identify the variableness in seed quality. The fifth combination consisted of control seeds of each variety not prepared with any of the described methods. Before sowing, the seeds of all the combinations were dressed with Thiuram (a 12 g dose per 1 kg of seeds).

For assessment of the course of field emergence, 100 seeds were sown in six replications in 10 m rows (spacing 10 cm) with a Wintersteiger hand drill. The sowing date was about 20th April each year. After 30 days from the half time of emergence (more than 50% of plants having emerged), the plants were dug out from two replications and their root, leaf blades and petiole dry mass, leaf area and number were assessed. The leaf area was measured by comparison to the control plants, whose area was estimated by planimetery methods.

Each day newly emerged plants were marked with colour sticks so that the date of emergence, counted in days past sowing, of each single plant could be identified during the vegetation period. Additionally, the distance between plants in rows and single root weight during the harvest were assessed.

For the determination of field emergence course, the speed and spread of emergence were measured. Field emergence was determined as the percentage of emerged seedlings to the number of seeds sown. Speed and spread of emergence was counted by the Pieper coefficient [13] i.e. the mean time of one seed germination (or plant emergence). When assessing the spread of germination (emergence), the assumption is that the first day of germination (emergence) is the day when the first radicles of a given seed sample germinate (the first plant emerges).

To estimate the effect of seed treatment on the course of field emergence, separate experiments were conducted. Seeds were sown with a precision drill in six rows (spacing in rows 12 cm, between rows 50 cm) in four replications. Methods of cultivation were typical, the forecrop being cereals.

Climatic conditions (temperature an rainfall) in the years of study are presented in Table 1. The effect of prolonged field emergence on the coefficient of variability of root weight was calculated by linear functions y = a + bx, y representing the coefficient of variability, x representing spread of field emergence (in days).

RESULTS

Sugar beet seedling growth at the beginning of the vegetation period differed greatly in the years of study depending on the air temperature and water availability in the soil (Table 2). Each year the sugar beet plants which emerged first produced heavier roots than the ones emerging in the middle or at the end of the field emergence period. These relations remained to the end of vegetation time. There was also strong correlation between root weight at harvest time and the number of days from sowing to emergence (Table 2). The time and sequence of emergence measured by the number of days from sowing to emergence influences final root weight much more strongly than the mean distance to the neighbours in the rows and mean weight of the neighbours. Pair correlation coefficients between the root weight during the harvest and the number of days from sowing to emergence ranged from –0.42 to –0.65 in the years of the study (Table 3). However, pair correlation coefficients between the root weight during the harvest and the mean distance to the neighbouring sugar beet plants in the row and their weight were not statistically proved.

On average in the three years of study there were no significant differences in field emergence after sowing of seeds treated in different ways. Lower field emergence (58.8%) was observed in the case of rubbed seeds, but it was significantly higher than that for the control combination (54.0%).

The average time of single plant emergence differed considerably in separate years of the experiment and ranged from 6.02 days in 2001 to 12.1 days in 2002 (Fig. 1). On average, during the three-year study, seedlings from primed or rubbed and primed seeds emerged in 8.70-8.71 days, whereas from the other seed types between 9.62 and 9.73 days.

Uniformity of field emergence ranged from 2.77 days in 2003 to 4.82 days in 2001 (LSD = 0.31). Seed priming and priming with rubbing improved uniformity of field emergence for each year of the experiment and on average (Fig. 2).

The field emergence time of plants from primed or rubbed and primed seeds was shorter by 0.88 to 0.45 days than in the case of other types of seeds.

During three years of study root yield ranged from 53.4 to 54.6 t·ha^-1. Each year seed treatments caused a yield increase compared to the control combination of non-treated seeds. In consequence the yield increased from 3.1 to 4.1 t·ha^-1 in comparison to the control seeds (Fig. 3). The lowest yield increase compared to the raw seeds (on the margin of significance) was obtained for rubbed and for primed seeds. Seeds of different varieties showed similar reaction to the particular methods of seed treatment.

Values of root weight variability coefficient ranged from 53.3 to 73.9% in the years 2001-2003. Variety had no influence on the root weight variability coefficient. In 2001, 2002 and 2003 the variability coefficient varied significantly and was equal to 67.8%, 66.6% and 55.9% respectively (LSD = 5.1). The method of seed treatment also greatly influenced sugar beet root weight variability coefficient in 2001-2003. Sugar beet plants grown from control seeds had root weight variability coefficient equal to 65.2%, from rubbed seeds 67.3%, from primed seeds 59.4%, from washed seeds 67.2% and from rubbed and primed seeds 58.1%, (LSD = 5.5) (Fig. 4). Priming and priming together with rubbing decreased the coefficient of root weight variability significantly.

Root weight variability coefficient was strongly correlated to the mean time of field emergence. For all the five types of seeds and three varieties during the three years of study, the correlation coefficient between root weight variability and mean time of emergence was 0.68 (R² = 46.6%). However, there were significant differences (P = 0.01) in the correlation coefficient values depending on the seed treatment: 0.77, 0.84, 0.53, 0.88 and 0.73, for control, rubbed, primed, washed, or rubbed and primed seed respectively.

These data show clearly that seed priming causing accelerated and more uniform field emergence at the same time causes a decrease in relation between root weight variability and spread of emergence. Moreover, the shorter the mean time of emergence, so the more uniform the sugar beet plants' emergence, the lower the root weight variability during the harvest.

The equation of linear regression between the root weight variability coefficient (y), and the spread of field emergence (x) for the three varieties and the three years of the study was y = 38.8 + 6.0x. This means that one day's increase in uniformity of emergence (decrease of the value by 1) causes a decrease of root weight variability coefficient by 6.0% (Fig. 5).

DISCUSSION

Complex technologies of sugar beet treatment are patented and kept in secret by seed companies. Seed quality improvement is usually obtained using methods which change physical seed properties, like rubbing or polishing [5] with seed priming. The commercial results of implementation of such methods are for instance Quick Beet [2,3] or XBEET [7] seed. Experiments on seed priming and seed priming in combinations with other methods of seed quality improvement are still important and carried out.

The main result of seed priming and priming together with rubbing was acceleration of field emergence and shortening of emergence time resulting in an improvement in uniformity. These results are in accordance with those of Redfearn et al. [16], Redfearn and Osborne [17], and Kawakatsu et al. [9]. The acceleration of field emergence caused an increase in root yield. According to the work of Zdunek [21] it is possible to state that acceleration of field emergence causes faster development of leaf area [21]. Similarly, Day [4] has shown that description of increasing growth of sugar beet in terms of leaf area and radiation interception is a good method of characterizing early growth.

There was also a strong correlation between the coefficient of single root weight variability during the harvest and mean time of field emergence. This relation can be explained by the influence of emergence time within the plant population on the final root weight. The more delayed the emergence of particular plants, the lower the weight of single roots [14]. However, the favourable influence of seed priming on field emergence and yield depends on environmental conditions and is not always visible. Sometimes it can also be unfavourable (oral information from seed company representative).

Different sugar beet varieties were chosen in order to identify the variableness in seed quality. There are usually large discrepancies in seed vigour among varieties and seed lots [10].

Harper [6] elaborated a general rule of plant emergence sequence and its influence on final weight. According to this rule, the first plant emerging (before its neighbours) has a greater chance of dominating the environment and using its resources. This rule explains the differences in final weight of plants from one population through intraspecific competition.

CONCLUSIONS

1. Washing, rubbing and priming of seeds affects mostly the speed and spread of field emergence.

2. There is a strong correlation between mean time of emergence and root weight variability during the harvest. The more extended the field emergence, the more variable the root weight.

3. Time of single plant emergence has a great influence on final root weight during the harvest. Plants emerging first have the highest root weight. The influence of emergence time on root weight is stronger than that of the distance in rows or of the mean weight of the two neighbouring roots.

REFERENCES

1. Bell C.I., Milford G.F.J., Leigh R.A., 1996. Sugar Beet. [In:] Photoassimilate distribution in plants and crops. Source-sink relationships, E. Zamski, A.A. Schaffer (eds.), Marcel Dekker Inc., USA, New York, 691–707.

2. Chrobak Z., 2008. Doświadczenia z szybkimi burakami – Quick Beet z KHBC w roku 2007 zakończone [Quick Beet Experiments – KHBC Quick Beet of 2007 completed]. Poradnik Plantatora Buraka Cukrowego 2, 39–41 [in Polish].

3. Chrobak Z., 2009. Doświadczenia z nasionami Quick Beet trwają [Quick Beet seed experiments in progress]. Poradnik Plantatora Buraka Cukrowego 2, 24–25 [in Polish].

4. Day W., 1986. A simple model to describe variation between years in the early growth of sugar beet. Field Crops Res. 14. 213–220.

5. Doronin V.A., Busol N.V., Karpuk L.M., 2007. Effect polishing regimes on sugarbeet seed quality. Sakharnaya Svekla 1, 13–15.

6. Harper J.L., 1977. Population biology of plants. Academic Press, London.

7. Hemb R.L., Stewart J.F., Hubbell L.A., Fogg R.A., Guza C.J., Wishowski D.B., Poindexter S.S., 2007. Evaluation of XBEET, an enhanced sugarbeet priming system. International Sugar Journal 109 (1306), 640–642.

8. Jaggard K.W., 1992. Remote sensing to forecast yield in England. Proc. IIRB 55^th Winter Congress, 253–260.

9. Kawakatsu M., Sekimura K., Ogata N., Tanaka M., 1997. Study on sugarbeet seed quality. 2. Effects of processing and storage on seed germination. 37^th Meeting of the Japanese Society of Sugar Beet Technologists, Sapporo, Japan, Proc. of Japanese Soc. of Sugar Beet Technologists 39, 42–47.

10. McGrath J.M., Derrico C.A., Morales M., Copeland L.O., Christenson D.R., 2000. Germination of sugar beet (Beta vulgaris L.) seed submerged in hydrogen peroxide and water as a means to discriminate cultivar and seedlot vigor. Seed Sci. Technol. 28(3), 607–620.

11. Mukasa Y., Takahashi H., Taguchi K., 2001. Seed priming treatment promoting early growth and resulting in uniform plant weight in sugarbeet. Proc. of the Japanese Soc. of Sugar Beet Technologists 43, 108–115.

12. Mukasa Y., Takahashi H., Taguchi K., Ogata N., Okazaki K., Tanaka M., 2003. Accumulation of soluble sugar in true seeds by priming of sugar beet seeds and the effects of priming on growth and yield of drilled plants. Plant Prod. Sci. 6(1), 74–82.

13. Pieper H., 1952. Das Saatgűt. P. Parey Verlag, Berlin.

14. Podlaski S., 1990. Właściwości owoców buraków cukrowych mające wpływ na kiełkowanie, wschody polowe oraz wzrost roślin [The properties of sugar beet fruits affecting germination, field emergence and growth of plants]. Treatises and Monographs. Wyd. SGGW-AR, Warszawa [in Polish].

15. Podlaski S., Grabowska M., 1995. Technologiczne i fizjologiczne sposoby poprawy jakości nasion rzepaku [Technological and physiological aspects of oilseed rape seed treatment]. Biul. IHAR 193, 103–112 [in Polish].

16. Redfearn M., Clarke N.A., Osborne D.J., Halmer P., Thomas T.H, 1997. DNA integrity and synthesis in relation to seed vigour in sugar beet. [In:] Basic and applied aspects of seed biology, R.H. Ellis, M. Black, A.J. Murdoch, T.D. Hong (eds.), Kluwer Academic Publisher, Dordrecht, The Netherlands, 413–420.

17. Redfearn M., Osborne D.J., 1997. Effect of advancement on nucleic acids in sugarbeet (Beta vulgaris) seeds. Seeds Sci. Res. 7(3), 261–267.

18. Scott R.K., Jaggard K.W., 1978. Theoretical criteria for maximum yield. Proc. IIRB 41^st Winter Congress, 179–198.

19. Scott R.K., Jaggard K.W., 1992. Crop growth and weather: can yield forecasts be reliable? Proc. IIRB 55^th Winter Congress, 169–187.

20. Stibbe C., Märländer B., 2002. Field emergence dynamics significance to intraspecific competition and growth efficiency in sugar beet (Beta vulgaris L.). Variety Trials in Sugar Beet. Methodology and Design. Advances in Sugar Beet Research 4, 109–124.

21. Zdunek E., 2003. Wpływ siedliskowych warunków reprodukcji nasion buraka cukrowego na ich właściwości [Effect of the sugar beet seed reproduction habitat conditions on their properties]. SGGW, Warszawa, rozprawa doktorska [in Polish].

Accepted for print: 28.07.2010

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