Agronomy Journal 92:1206-1210 (2000)
© 2000 American Society of Agronomy
FORAGES
Chicory and English Plantain Seedling Emergence at Different Planting Depths
Matt A. Sanderson and
Gerald F. Elwinger
USDA-ARS, Pasture Systems and Watershed Management Res. Unit, Building 3702, Curtin Rd., University Park, PA 16802-3702 USA
mas44{at}psu.edu
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ABSTRACT
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Chicory (Cichorium intybus L.) and English plantain (Plantago lanceolata L.) have been introduced in the USA as perennial herbs for pastures. A knowledge of seedling emergence and the structure of these species under different planting conditions is necessary for developing planting recommendations. We conducted controlled environment and field studies to compare the emergence and morphology of chicory and plantain seedlings from three planting depths. `Grasslands Puna', `La Certa', and `Forage Feast' chicory, and `Ceres Tonic' and `Grasslands Lancelot' plantain were sown at 1, 3, and 6 cm depths in the growth chamber and greenhouse. The seedlings were destructively sampled 14 d after emergence, and the number and mass of leaves and roots (primary, lateral, basal, and adventitious) were recorded. The same cultivars were sown in field plots in July and September 1998 to determine seedling size and emergence from 1-, 3-, or 6-cm planting depths. Controlled environment studies showed that deeper planting reduced the root weight, length, and number more in chicory than in plantain. Planting at 3 and 6 cm in the field reduced seedling emergence by 34 and 60% (avg. of cultivars), respectively, compared with the 1-cm planting depth. Differences in seedling size among cultivars within species were mainly related to differences in seed mass. Plantain had better seedling emergence in the field than chicory (54 vs. 27% in July and 60 vs. 17% in Sept.), and these differences were not related to differences in seed mass. Both chicory and plantain should be planted no deeper than 1 cm for rapid establishment.
Abbreviations: DAP, days after planting
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INTRODUCTION
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PRODUCERS IN THE NORTHEASTERN USA would like pasture species that are productive during the summer slump period of July, August, and early September. Chicory (cv. Grasslands Puna) has been investigated as an alternative pasture herb because of its reported drought tolerance and good production in summer (Belesky et al., 1999; Kunelius and MacRae, 1999). Data on the proper planting depth for chicory are limited. Moloney and Milne (1993) recommended 1 cm as the optimum planting depth for Grasslands Puna.
English plantain (narrow-leaf plantain, buckhorn plantain, ribwort, and ribgrass) commonly occurs as an occasional weed in temperate-region pastures (Grime et al., 1990). It is palatable to livestock (Foster, 1988; Ivins, 1952) and is described as deep rooting and drought resistant (Sagar and Harper, 1964). Recently, domesticated cultivars of plantain have been selected for pasture production in New Zealand (Rumball et al., 1997; Stewart, 1996). Data on the planting depth for these plantain cultivars are lacking; however, some ecological research has shown that plantain establishes best on uncompacted soils (Blom, 1978). Both chicory and plantain have epigeal seedling emergence (Sanderson and Elwinger, 2000).
Rapid development of the leaf area and the establishment of a critical number and mass of roots are necessary to ensure the survival of forage seedlings. Planting small-seeded forages too deep in the soil reduces emergence, seedling vigor, and ultimately the established stand (Martin et al., 1976). Thus, a knowledge of the optimum seeding depth for individual forage species is critical for establishing productive stands in pastures. The objective of this research was to determine the ability of several cultivars of chicory and plantain to emerge from different planting depths. We conducted growth chamber and greenhouse experiments to examine the seedling morphology when planted at three depths and conducted field experiments in two different environments to verify the responses.
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Materials and methods
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Greenhouse and Growth Chamber Trials
In the growth chamber, three seeds of each cultivar (Grasslands Puna and La Certa chicory and Ceres Tonic and Grasslands Lancelot plantain) were planted at 1, 3, or 6 cm depths in 5 cm diameter by 21 cm deep containers filled with sand. The containers were packed to a bulk density of 1.92 g cm-3, with a field capacity of 0.21 m3 m-3. Fifteen containers of each cultivar/seeding-depth combination were planted. The seedlings were thinned to one per container soon after emergence. Because of the number of containers, two growth chambers were used and treatments were blocked by chambers and within chambers. The temperatures in the growth chambers were maintained at 25°C during the day and 15°C at night. The daylength was 16 h, and the relative humidity ranged from 50 to 70%. Light in the chambers was provided by a mixture of incandescent and fluorescent bulbs at 216 µmol photosynthetic photon flux density m-2 s-1 with a red/farred ratio of 1.61. Plants were watered daily to about field capacity with half-strength Hoagland's solution.
The experiment was repeated in the greenhouse during February 1999. The same procedures were used, except that Forage Feast chicory was included and containers were filled with a mixture of potting soil (Scots-Sierra Hortic. Products, Marysville, OH)1
and Morrison soil (fine-loamy, mixed, mesic Ultic Hapludalfs). The containers were packed to a bulk density of 1.51 g cm-3, with a field capacity of 0.24 m3 m-3. The experimental design was a randomized complete block with 15 replicates. The temperature in the greenhouse varied from 23 to 41°C during the day and from 13 to 24°C at night. The relative humidity ranged from 10 (day) to 100% (night). Natural light was supplemented (but the natural daylength was not extended) with artificial light from 400-W lamps that provided 260 µmol photosynthetic photon flux density m-2 s-1 at plant height during the experiment. Red/farred light ratio of the supplemental light was 1.61 compared with 1.31 for natural light levels. Plants were watered daily to about field capacity, and no additional nutrients were added.
The date of seedling emergence was recorded for each container in both trials. At 14 d after planting (DAP), the number of leaves per plant were counted, plants were removed from the container, and the soil was washed from the roots in cold running water. The area of the cotyledons and leaves was determined with a Li-Cor 3000 leaf area meter (Li-Cor, Lincoln, NE). The root length was measured from the cotyledonary node to the tip of the longest root. In the growth chamber trial, roots were classified as primary (taproot), lateral, basal, or adventitious as described by Stofella et al. (1979) and Zobel (1991), and the number of roots in each category were counted. The shoots and roots were separated at the cotyledon node and dried at 55°C for 48 h to determine the dry mass.
Field Trials
Two field trials were conducted at the Russell E. Larson Agricultural Research Center near Rock Springs, PA (40°48' N, 77°52' W, 350 m above sea level) to determine seedling emergence from three depths. The soil at the site was a Hagerstown silt loam (fine, mixed, semiactive, mesic Typic Hapludalfs) with a pH of 6.5 and 122 and 179 kg ha-1 of available P and K. No fertilizer was applied in either trial, and the plots were not irrigated.
The trials were planted on 1 July and 1 Sept. 1998. The experimental site was cultivated and rototilled to a 15-cm depth. For the July planting, furrows that were 0.5 m long were made in the soil to the appropriate depth (1, 3, or 6 cm) with a calibrated board. Then, 100 seeds were placed into the furrow and covered with soil. The experimental area was then rolled twice (at right angles) with a water-filled drum to pack the soil. The procedures were the same at the September planting, except that the row length was increased to 1 m and only 50 seeds were planted per row. There was 0.5 m between the rows and blocks in each experiment. The experimental design was a randomized complete block with four blocks.
The emerged seedlings in each row were counted daily or every other day for 2 wk, then they were counted weekly for 3 wk. On 4 August (1 July planting, 35 DAP) and 16 October (1 Sept. planting, 45 DAP), all seedlings in each row were excavated to a 10-cm depth, and the number of live emerged seedlings were counted. Five seedlings were selected at random, and the number of leaves and seedling dry mass (55°C for 48 h) were determined. The number of emerged seedlings was normalized to the number of potential seedlings based on laboratory estimates of the germination percentage of each cultivar.
Data for the growth chamber, greenhouse, and field trials were checked for heteroscedasticity and normality and then transformed as necessary. Data are presented on the original scale with footnotes indicating when significance tests were calculated on a transformed scale. All experiments were analyzed as a randomized complete block design. Preplanned comparisons were used to compare treatment means. The comparisons for the growth chamber experiment were (i) chicory vs. plantain, (ii) Lancelot vs. Tonic plantain, and (iii) Puna vs. La Certa chicory. The contrasts for the greenhouse and field experiments were (i) chicory vs. plantain, (ii) Lancelot vs. Tonic plantain, (iii) Puna vs. other chicory, and (iv) Forage Feast vs. La Certa chicory.
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Results and discussion
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Greenhouse and Growth Chamber Trials
Forage Feast chicory did not emerge from the 6-cm planting depth in the growth chamber; therefore, it was deleted from the analysis to balance the data set. An increased planting depth decreased the seedling leaf number, leaf mass, leaf area, cotyledon area (data not shown), root number, root length, and root weight, and it increased the number of days to emergence for all cultivars (Table 1)
. The responses of the cotyledon area and mass to the planting depth were the same as leaf attribute responses in both trials (data not shown) and will not be discussed further.
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Table 1 Least-squares means of the plantain and chicory seedling leaf attributes in the growth chamber and greenhouse
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Chicory and plantain cultivars differed significantly in leaf number, mass, and area in the growth chamber (Table 1). Chicory had more and heavier (P < 0.01) leaves than plantain, with the leaves of Puna chicory larger than those of La Certa. There was no cultivar x planting-depth interaction for the leaf attributes. The number of days to emergence was similar for all cultivars
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There was a cultivar x planting-depth interaction (P < 0.05) for root length, number, and weight in the growth chamber (Fig. 1) . The interaction resulted from a change in the ranking of chicory and plantain with planting depth. Chicory had longer and heavier roots (P < 0.05) than plantain at 1 and 3 cm; however, the differences were not as large at 6 cm. Chicory had more (P < 0.05) lateral roots at 1 cm, but plantain had more roots at the 3- and 6-cm depths.
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Fig. 1 Least-squares means of plantain and chicory seedling root attributes in the growth chamber trial
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In the greenhouse, the seedlings did not emerge from the 6-cm planting depth. This may have resulted from differences in the growth media and environment between the greenhouse and growth chamber. The soil used in the greenhouse was a mix of potting media and sandy soil, which may have had a different structure than the sand used in the growth chamber. As in the growth chamber trial, the seedling size and mass were reduced when the seeds were planted deeper (Tables 1 and 2)
. The entries did not differ (P > 0.05) in leaf number, but Chicory had larger (P < 0.01) leaves than plantain, and Tonic plantain had larger (P < 0.05) leaves than Lancelot. The number of days to emergence increased from 18.5 to 24 as the planting depth increased (data not shown).
The number of adventitious and basal roots increased with deeper planting; however, the number of lateral roots was not affected by the planting depth even though the primary roots were shorter at greater depths (Table 2). Chicory had longer and heavier (P < 0.05) roots than plantain in the greenhouse, probably because of the dominant primary root in chicory (Sanderson and Elwinger, 2000). Tonic plantain had more and heavier (P < 0.01) roots than Lancelot. Plantain had more (P < 0.05) adventitious roots than chicory, which confirms earlier research (Sanderson and Elwinger, 2000).
Field Trials
The emergence percentage decreased (P < 0.05) with an increased planting depth in July, but there was no effect on the seedling leaf number or mass (Table 3)
. Chicory and plantain cultivars differed in emergence and seedling attributes. Plantain had greater (P < 0.01) emergence than chicory, but the leaf number and seedling mass did not differ between the species. Puna chicory had greater (P < 0.01) emergence, seedling mass, and leaf number than La Certa and Forage Feast.
During the September trial, there was very erratic emergence at the 3-cm planting depth, with only Lancelot plantain, Tonic plantain, and Puna chicory emerging from that depth (Table 4)
. Only Tonic plantain emerged from the 6-cm depth (data not shown). Differences between the planting dates probably resulted from differences in rainfall and soil moisture (Fig. 2 and 3)
. In July, a total of 4.7 cm of rain fell within 7 DAP. The period of most rapid increase in seedling emergence occurred from 5 to 8 DAP (data not shown). The early rainfall probably maintained soil moisture at greater depths for several days. Dry conditions before the 1 September planting (5.0 cm of rain fell on 10 Aug. and 1.0 cm fell on 14 Aug., but no rain fell from 14 Aug. to 2 Sept.) and relatively low rainfall during the fall trial resulted in much drier soil conditions (Fig. 3) and probably reduced the overall emergence compared with the July planting. The light rains that occurred during the September trial probably wetted only the surface and did not benefit the seeds planted at 6 cm. The period of most rapid seedling emergence occurred in September at 16 to 24 DAP for plantain and 20 to 31 DAP for chicory (data not shown). Plantain had better emergence earlier, and thus had greater seedling mass than chicory at 45 DAP. The results from both field trials indicate that plantain will germinate and emerge better than chicory under adverse field conditions.
Sanderson and Elwinger (2000) reported that development of three to four leaves was required for the successful establishment of chicory and plantain seedlings. According to this criterion, all cultivars were established by 35 DAP in the July planting, but seedlings in the September planting were not fully established by 45 DAP and probably would not have survived the winter.
The differences in seedling attributes among cultivars in the greenhouse, growth chamber, and field trials may be explained by differences in the seed mass. Seedling vigor and seed mass are often positively correlated (Martin et al., 1976). The seed masses of La Certa and Forage Feast chicory were 1.18 and 1.57 mg seed-1, respectively, whereas the seed masses of Lancelot and Tonic plantain were 1.45 and 2.19 mg seed-1, respectively (avg. of four replicate determinations on lots of 100 seeds for each entry). Tonic plantain often had a larger seedling size than Lancelot plantain (Tables 1, 2, and 3), which may be related to differences in the seed mass. The Puna chicory seeds that we obtained came with a CaCO3 coating that was used to enhance seed flow, which prevented us from obtaining accurate seed mass estimates. The coating did not appear to benefit Puna seedling emergence in the field in September (Table 4), but it may have benefited emergence in July (Table 3) compared with other chicory cultivars. The seed mass did not appear to affect the seedling emergence in the field because there were no significant differences between Tonic and Lancelot plantain or La Certa and Forage Feast chicory in emergence even though the cultivars differed in seed mass.
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Conclusions
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Deep planting reduced emergence in both chicory and plantain. Plantain had better seedling emergence in the field than chicory. Controlled environment studies showed that deeper planting reduced the root weight, length, and number more in chicory than plantain, perhaps explaining the differences in field emergence. Our results show that chicory and plantain should be planted no deeper than 1 cm for rapid establishment.
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ACKNOWLEDGMENTS
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Thanks to John Everhart, agricultural research technician, and several Penn State University undergraduate students for their help in conducting this study.
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NOTES
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1 Reference to a trade or company name is for specific information only and does not imply approval or recommendation of the company or product by the USDA to the exclusion of others that may be suitable. 
Received for publication January 18, 2000.
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REFERENCES
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- Foster L. Herbs in pastures. Development and research in Britain 1988;1850-1984.(Biol. Agric. Hortic. 5):97-133.
- Grime J.P., Hodgson J.G., Hunt R. Comparative plant ecology. Cambridge, MA: Unwin Hyman, 1990.
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ABSTRACT
INTRODUCTION
