Sugar beet genotype response to soil compaction stress
T.A. Gemtos
a,*, C. Goulas
b, T. Lellis
caLaboratory of Farm Mechanization,Uni6ersity of Thessaly,Pedio Areos Str.,38334Volos,Greece bLaboratory of Plant Breeding,Uni
6ersity of Thessaly,Pedio Areos Str., 38334Volos,Greece cTEI of Larissa,Larissa,Greece
Received 23 March 1999; received in revised form 27 October 1999; accepted 26 January 2000
Abstract
Eleven sugar beet genotypes were tested for their performance under different soil compaction levels. The genotypes used were three inbreds, three commercial varieties widely cropped in Greece, four experimental hybrid varieties and two multigerm OP lines. The experiment was conducted in pots in glasshouse. Pots were filled with soil and after placing the seed at a depth of 3 cm, the compaction pressure was applied. Two soil types, two initial soil water contents and seven pressure levels ranging from a minimum pressure up to 400 kPa were the factors studied in a randomised complete block experiment with four replications. Results showed that sugar beet is sensitive to compaction although low compaction pressures (less than 200 kPa) seemed to be beneficial. From the genotypes tested inbreds were more sensitive to pressure effects than hybrids. Differences among hybrid varieties were observed indicating that response to soil compaction effect could be genotypically affected. This was further confirmed by the different response between the multigerm open polinated varieties © 2000 Elsevier Science B.V. All rights reserved.
Keywords:Sugar beet; Soil compaction; Plant emergence; Plant growth; Genotypes
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1. Introduction
Sugar beet is considered as a sensitive crop to compaction (Tijink and Maerlaender, 1998). Re-duced emergence, initial growth and final yields were reported in compacted soils (Chancellor, 1976; Gemtos and Lellis, 1997). Chancellor (1976 and references therein) referred to data showing that sugar beet yield was significantly reduced in a certain soil type when penetration resistance was
increased but in another soil type was not af-fected. He referred also to data where compacted corn plots irrigated weekly had no significant effect on crop growth and yield but in the less frequently irrigated plots early root development was severely retarded. Furthermore, in later stages root growth was faster in compacted plots but the adverse effects remained. Based on these data, Chancellor (1976) concluded that although the relation between crop yield and soil compaction is not straightforward, seedlings emergence and root development were affected by compaction. Kub-ota and Williams (1967) showed that even light compaction in a wet seedbed interfered with beet * Corresponding author. Tel.: +30-421-742-46; fax: +
30-421-742-70.
E-mail address:gemtos@uth.gr (T.A. Gemtos)
germination while heavier compaction generally reduced yields even in insensitive crops like bar-ley. Soane et al. (1982) indicated that cereal plants’ growth and yield are likely to show opti-mum response to certain soil compaction level. This optimum is related to soil type, crop growth stage and climatic conditions. They referred to data by Jaggart (1972) showing that compaction at 0 – 160 mm depth causing an increase of dry bulk density from 1.3 to 1.6 Mg/m3affected beets
and reduced sugar yield by 0.9 Mg/ha. Soane et al. (1982) mentioned data reported by Cooke and Jaggart (1974) which indicated that compaction reduced sugar yield by 1.9 Mg/ha and tops yield by 7 Mg/ha. Hebblethwaite and McGowan (1980) showed that compaction affects inversely sugar beet population and yields. Gemtos and Lellis (1997) showed that sugar beets growing in pots in a glasshouse are sensitive to compaction in the initial stages of growth and only very light com-paction (around 100 kPa) was beneficial to the crop.
Compaction is considered as a factor adversely affecting crop growth and yields although that contradicting results have been reported (Soane et al., 1982). Differences in rainfall over the years along with soil type are the two factors probably explaining the contradicting results. Genotypic ef-fects could be considered as well but to our knowledge data have not been reported. Modern varieties were developed under optimum soil con-ditions resulting from continuous soil tillage mainly by ploughing. It is then reasonable to be expected that they are adapted to conditions of minimum soil compaction. Taking into account the variety of existing agronomic factors, and the complex genotype×environment interactions, genotypic differences for adaptation to soil condi-tions and especially response to soil compaction stress could not be ruled out. The aim of this research was a preliminary attempt to study the response of 11 sugar beet genotypes to stresses imposed by soil compaction.
2. Material and methods
Eleven sugar beet genotypes representing differ-ent ploidy, inbreeding levels and seed morphology were used (Table 1). There were five lines, propri-etary of Hellenic Sugar Industry and three experi-mental varieties using these lines in some hybrid combinations. Lines 031 and 009 are diploid, monogerm, broad based inbreds whereas line 002 is diploid, monogerm, nearly inbred. Lines 782 and 795 are tetraploid, multigerm, narrow based synthetics. Genotype P104 is a diploid, monogerm single cross hybrid (002×009), genotype S562 is triploid, monogerm, single top cross hybrid (031×765), whereas genotype T1504 is a triploid, monogerm, three way top cross hybrid (P104× 782). RIZOR and VERGINA are commercial monogerm triploid hybrid varieties largely grown in Greece whereas genotype A1991 represents seed lot of a monogerm commercial hybrid vari-ety produced in 1991.
The soil compaction effects were studied in pots as follows. Plastic bags placed in a metal tube of 80 mm diameter and 120 mm height were filled with soil up to 3 cm under the cylinder top. Three Table 1
Description of genotypes used in the soil compaction effect study
Entry Identification Description
031
1 Monogerm, inbred (S3),diploid
male sterile
002 Monogerm, inbred line, diploid 2
male sterile
3 009 Monogerm, inbred (S3), diploid
4 P104 002×009, monogerm, single cross, diploid hybrid
S-562 Triploid, monogerm, single cross 5
(031×765), experimental hybrid variety
782
6 Multigerm, OP line, tetraploid 7 VERGINA Commercial monogerm triploid
hybrid variety RIZOR
8 Commercial monogerm triploid hybrid variety
765
9 Multigerm, OP line tetraploid T1594
10 Triploid, monogerm, three way top cross experimental hybrid variety (P104×782)
A1991
sugar beet seeds were placed on the top of the soil. Then 3 cm of soil were added on the top of the seed to fill up the tube in such a way to secure that initial soil volume was equal to that of the tube. Soil bags were compacted using the equip-ment and the procedure described by Gemtos and Lellis (1997) at pressures varying from minimum compaction (it is considered as compaction of 1 kPa) up to 400 kPa. The equipment consisted of a metal frame and a hydraulic jack. The metal tube with the soil was secured in the frame and the jack applied the pressure. A pressure gauge measured the hydraulic fluid pressure in the jack. The pres-sure gauge was calibrated with known weights for each applied force, and later was divided by the soil core surface area to give compaction pressure. Seven pressure levels were applied. In the lower level (1 kPa), the soil was just levelled by hand causing a minimum pressure. The other six pres-sures levels were equivalent to 50, 125, 200, 280, 340 and 400 kPa. After compaction the sinking of the soil surface was measured and the final vol-ume was calculated. The soil was weighted just after compaction and before watering and the specific weight of the compacted soil was calcu-lated. The procedure followed allowed for a wide range of compaction pressures to be tested. The lower pressures corresponded to those applied by drilling machines or cylinders used after drilling. Tractors’ compacting pressures depend on their weight and tyre size, which usually range between 100 and 200 kPa. Heavy harvesting machinery, heavy compaction cylinders, spraying tankers or other similar machinery, cause higher compaction pressures (Gemtos et al., 1999). Compaction is applied to the whole soil mass permitting the studying of the effects of the compacted surface layer (affecting emergence) and of the deeper lay-ers (affecting root growth). The procedure was used in many experiments and no damage to the seeds was observed even in larger seeds such as cotton. Two soil types, a sandy loam (sand 72.6%, clay 12.9%, silt 14.5% and organic matter content 1.2%) and a clay loam (sand 37.3%, clay 27.0%, silt 35.7% and organic matter content 0.98%), were used, at two initial water contents each. The water contents were 10 and 16% for the sandy loam, and 12 and 18% for the clay loam giving
dry and wet initial soil conditions. Thus there were 7×2×2×11 (compaction pressure× water content×soil type×genotypes) treatments analysed as a factorial experimental design with four replications. The single pot was the experi-mental unit. The pots, after soil compaction, were placed in a glasshouse in order to avoid weather effects. Only one plant was left in each pot (the first to emerge). The pots were watered every other day up to the field capacity of the soil. The experimental period was 30 days and the follow-ing observations were recorded:
1. Time to shoot emergence. Observations were taken twice every day.
2. Daily growth as measured by the height in-crease of the plant. Observations taken every other day.
3. Above ground and root dry matter. At the end of the experiment the aerial part was cut at ground level and oven dried at 72°C for 48 h. The soil was washed out from the root by running water and then the wet root was oven dried, in the same manner as for the aerial part.
4. In addition, before drying, root dimensions were recorded as follows: root diameter at the soil surface and at the bottom of the pot along with the main root length.
Fig. 1. Effect of compaction pressure on the soil dry bulk density.
rate was 72.6% meaning that in 362 out 1320 pots (27.4%) were empty that is having no emerged plants. The frequency of empty pots, averaged over genotypes for soil water content, was 62% under high initial water content condi-tion and 38% for the low water content. The corresponding frequencies for sandy loam and clay loam soil types were 42 and 58%, respec-tively. These frequency estimates indicated a wa-ter content and soil type effect on emergence. In the same manner a compaction pressure effect (Fig. 2) was indicating that compaction pressure higher than 125 kPa resulted in 3 – 9% increase of empty pots.
Variable genotypes, empty pots, showed the expected response with the inbreeds being affected more severely due to inbreeding depression (Fig. 3). Besides this expected response some differ-ences were evident within the group of outcrossed genotypes indicating possible genotypic differ-ences. Main effects were highly significant for all variables and some interaction effects, as well (Table 2). In spite of some interaction effects and especially those for the root diameter being sig-nificant, interaction effects generally contributed no more than 3.5% to the total variance for each main effect. This means that the average main effects could be considered disregarding interac-tions (Table 3).
Time to shoot emergence was affected by the factors studied, as well (Tables 2 and 3). Com-Fig. 2. Frequency histogram of empty pots versus compaction
pressure.
3. Results
The soil compaction effect on soil dry bulk density is shown in Fig. 1. The overall emergence
Table 2
Analysis of variance for the sugar beet growth parametersa
Plant dry matter Root dry matter Root diameter
Plant height Root length
Main effects
ans, not significant effect. *Effect significant atP=0.05. **Effect significant atP=0.01.
paction pressures 1 – 125 kPa did not seem to affect time to emergence but when the pressure exceeded a threshold point of 200 kPa the emer-gence time increased linearly. Concerning the genotypic response, although the average geno-typic effect did not show differences (Table 3), the clustering of genotypes in groups indicated geno-typic differences which were in the range of about 2 days (data not shown) showing that genotypes could be grouped in fast and slow emerging. These differences could not be clearly attributed to inbreeding versus outcrossing effects, since some of the differences could be attributed to fruit shape (genotype 782 being multigerm) and some other to hybrid vigor (P104). Also the slow emerging genotypes included an inbred line (031) and a hybrid variety (Rizor) whereas all other genotypes ranged between fast and slow. Vari-ables related to performance like plant height, aerial dry matter and root traits (diameter, length) were affected by soil water, compaction pressure and soil type. Genotypic differences were ob-served, as well. The average plant height was significantly lower (87 vs. 138 mm) under high soil water and in the sandy loam soil type (Table 3). The same holds true for the compaction pressure effect. Thus compaction pressure from 1 to 125
kPa resulted in higher plants as compared to pressures higher than 200 kPa (Table 3).
Concerning plant height averaged over factors, genotypes showed a different response. Three groups were evident as confirmed by data pre-sented in Table 3. The inbred group (genotypes 031, 002 and 009) as expected, had the smaller height, the hybrid one (genotypes P104, S-582 and 782) the larger, whereas the remaining genotypes were of intermediate height. The soil water con-tent had a significant effect on dry matter pro-duced by the aerial part of plants (Table 2). Increased initial soil water resulted in a substan-tial reduction (0.41 vs. 0.79 g) whereas the com-paction pressure resulted in a detrimental effect in the same direction. Thus, pressures from 0 to 125 kPa did not seem to influence the dry matter production whereas beyond the threshold point of 200 kPa that dry matter showed a linear decrease (Table 3).
direc-T
Performance of each parameter studied under the conditions tested
Time to emergence
Average main Final plant height Plant dry matter Root dry matter Diameter at soil level Root length (mean (mm))
(mean (g)) (mean (mm))
(mean (g)) (mean (days)) (mean (mm))
effects
Initial soil water content
3.6890.10 52.291.25
Soil compaction pressure(kPa)
53.392.34
Sandy loam 6.090.12
Genotype Vergina 6.190.27
tion as those observed for the above ground dry matter production. High initial soil water and the high compaction pressure resulted in the same detrimental effects whereas the genotypic differ-ences were observed in the same manner as previ-ously. Root diameter at soil level (Tables 2 and 3) was larger under low soil water, and clay loam soil type whereas low compaction pressures (0 – 125 kPa) resulted in larger diameter as compared to high pressure. Genotypes reacted in different manner indicating genetic effects (Table 3). Thus inbreds (genotypes 031, 002 and 009) had the smaller diameter, hybrid (P104) the largest and all other genotypes intermediate. Finally, root length was affected by soil water content and com-paction pressure, but not by soil type (Tables 2 and 3). High initial soil water with high com-paction pressure resulted in decreased root length, whereas the genotypic differences observed for all other traits were evident, for the root length as well. Thus inbreds (genotypes 031, 002 and 009) had the smaller root length as compared to the other genotypes.
4. Discussion
Results indicated that soil compaction caused by pressure and/or enhanced by high initial soil water content, resulted in an overall 27.4% re-duced seed emergence. Data indicated that the soil water content had a threshold point between the studied values and the compaction pressure corresponding to pressures of around 125 kPa above which it became detrimental. These data provided some information on the condition, which could cause detrimental effect on emer-gence and thus affect final stands especially when planting to a stand. Soil type, averaged over other factors, resulted in erratic emergence, as well. Higher losses were found in the sandy loam soil as compared to clay loam. We could hypothesise that the higher compaction pressure interacted with the coarser sandy soil type and thus the lower emergence was manifested.
Sugar beet seed field emergence capacity is mostly interesting to both seed industry and growers. Although the final emergence percentage
depends on the seedbed conditions, i.e. soil mois-ture, compaction, temperamois-ture, etc., prevailing during planting and emerging time (Durrant, 1981) genotype differences and seed processing effects seem to influence it, as well (McFarlane, 1975; Lexander, 1981; Brown, 1981; Apostolides and Goulas, 1998). The soil compaction stress effect on the genotypes studied, as it was esti-mated by the number of empty pots, differenti-ated them into three groups, mainly inbred, open pollinated and hybrid. The inbred group (031, 002, 009) suffered on the average two-fold higher emergence losses as compared to the open polli-nated (782 and 765). This expected response indi-cated genetic effect mainly attributed to the inbreeding depression whereas the difference in ploidy (2× vs. 4×) and fruit shape (monogerm vs. multigerm) must be taken into account. This was further corroborated by the hybrid group performance. Thus hybrids P104 (002×009), S562 (031×765) and T1594 (P104×782) suffered losses in the range of those observed for the open pollinated group indicating genetic effects due to heterosis. Furthermore differences for empty pots were observed within the hybrid group (experi-mental and commercial hybrid varieties) which provide evidence that genotype differences for field emergence under soil compaction stress are existing. This indication is in accordance with genotype difference observed among and within sugarbeet populations and among open pollinated lines and hybrids (Goulas, unpublished data). Furthermore they are in agreement with the dif-ferences among maize inbred lines and hybrids for germination and field emergence under cold stress condition (Hodges et al., 1995, 1997), among maize inbreds and within maize population (Ko-rkovelos et al., 1998)
in-bred – hybrid performance under cold stress. Ac-cordingly genotypic differences in the speed of germination among maize inbred lines grown un-der cold stress condition have been reported (Mock and Eberhart, 1972), whereas the speed of germination under cold stress laboratory germina-tion condigermina-tion differentiated maize inbreeds from the corresponding hybrids implying inbreeding depression versus heterosis effects (Karagiozopou-lou, 1999).
It seems then that our data provide experimen-tal evidence that emergence either as final phe-nomenon or as speed of germination under soil compaction stress could be used as selection crite-rion for sugarbeet breeding purposes. The overall 30 days performance as expressed by plant height, dry matter production (root and above ground) and root characteristics (diameter and length) was affected by soil compaction stress and indicated genotype differences. The inbred group on the average, as expected, was of smaller height as compared to the hybrid group, reflecting to a major extend inbreeding depression effects, whereas the within hybrid group differences could indicate some genotype differences to soil com-paction stress. The dry matter performance and the root characteristics of the plant followed the same pattern as the discussed for plant height. Our data present evidence that genotype differ-ences for early growth traits are existing under the stress condition studied and could be used as early selection criterion for breeding purposes.
This statement is in agreement with data indi-cating that early growth expressed as total plant performance could be used as reelection criterion in sugarbeet (Goulas and Maslaris, 1994), al-though the root hypocotyl diameter was reported to be an effective predictor of genotype’s final performance and worth using as selection crite-rion (Doney and Theurer, 1976).
Simple phenotypic correlation coefficients be-tween early growth traits as expected were high and practically of the same magnitude for each pair of traits (data not shown) indicating that any single trait could be used to predict genotypes’ early performance but we feel that the over all performance based on more traits should be more effective.
In conclusion our data presented preliminary evidence that genetic variation among sugar beet genotypes for response to soil pressure com-paction stress is existing. Genotypes tolerant to this stress seemed to be existing and selection of the promising ones seems to be feasible based on their performance for field emergence and early growth traits under the stress conditions. Thus the possibility to develop sugar beet varieties tolerant to compaction stress might be of interest for the reduced tillage and no-tillage cultivation tech-niques.
References
Apostolides, G., Goulas, C., 1998. Seed crop environment and processing effects on sugar beet (Beta6ulgarisL.) certified
hybrid variety seed quality. Seed Sci. Technol. 26, 223 – 235.
Brown, S.I., 1981. Germination and emergence of sugar beet at low temperature. Proceedings, 44th winter Congress, IIRB, pp. 93 – 103.
Chancellor, W.C., 1976. Compaction of soil by agricultural equipment. Div. Agric. Sci., Univ. of California, Davies, Bull., 1881.
Doney, D.C., Theurer, J.C., 1976. Hypocotyl diameter as a predictive selection criterion in sugar beet. Crop Sci. 16, 513 – 515.
Durrant, M.J., 1981. Some causes of the variations in plant establishment Proceedings, 44th winter Congress, IIRB, pp. 7 – 20.
Gemtos, T.A., Lellis, T., 1997. Effects of soil compaction, water and organic matter contents on emergence and initial plant growth of cotton and sugar beet. J. Agric. Engng. Res. 66, 121 – 134.
Gemtos, T.A., Chouliaras, N., Marakis, St., 1999. Vinasse rate, time of application and compaction effect on soil properties and durum wheat crop. J. Agric. Engng. Res 73, 283 – 296.
Goulas, C.C., Maslaris, N.C., 1994. Genotypic differences in sugar beet seasonal growth patterns and their implications in population improvement breeding schemes. 5th Panhel-lenic Congress of the HelPanhel-lenic Plant Breeding and Genetics Society, Volos, pp. 116 – 123.
Hallauer, A.R., 1988. Modern methods in maize breeding. In maize breeding and maize production, Euromaize, Maize Research Institute, Zemun Polje, Belgrade, Yougoslavia, pp. 1 – 10.
Hebblethwaite, P.D., McGowan, M., 1980. The effects of soil compaction on the emergence, growth and yield of sugar beet and peas. J. Sci. Food Agric. 31, 1131 – 1142. Hodges, D.M., Hamilton, R.I., Charest, C., 1995. A chilling
Hodges, D.M., Adrews, C.J., Johnson, D.A., Hamilton, R.I., 1997. Sensitivity of maize hybrids to chilling and their combining abilities at two developmental stages. Crop Sci. 37, 850 – 856.
Karagiozopoulou, A., 1999. Determination of genetic purity of certified maize hybrid seed. Degree dissertation, Faculty of Agriculture, Plant and Animal Production, University of Thessaly, Volos, Greece.
Korkovelos, A.E.Z., Mamouris, A.G., Agorastos, A. Goulas, Chr., 1998. Screening maize inbred lines for tolerance to low/high temperature stresses during early growth using rapid molecular markers. 20th Panehellenic Meeting of the Society of Biological Sciences, pp. 137 – 138.
Kubota, T., Williams, R.J.B., 1967. The effects of changes of soil compaction and porosity on germination, establish-ment and yield of barley and globe beet. J. Agric. Sci. Camb. 68, 227 – 242.
Lexander, K., 1981. Physical and physiological seed character-istics influencing field emergence of sugar beet 44th Winter Congress, IIRB, pp. 21 – 36
McFarlane, J., 1975. Factors affecting sugar beet seed germi-nation in North America. J. Int. Inst. Sugar Beet Res. 7, 1 – 9.
Mock, J.J., Eberhart, S.A., 1972. Cold tolerance in adapted maize populations. Crop Sci. 12, 466 – 469.
Soane, B.D., Dickson, J.W., Campbell, D.J., 1982. Com-paction by agricultural vehicle: III Incidence and control of compaction in crop production. Soil Tillage Res. 2, 3 – 36. Tijink, F.G.J., Maerlaender, B., 1998. Introduction in soil compaction and compression in relation to sugar beet. In: B. Maerlaender, F.G.J. Tijink, C. Hoffman, R. Becker (Eds.), I.I.R.B. Advances in Sugar Beet Research, Vol. 1. Brussels, Belgium.
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