RESEARCH
Planting Rate and Depth Effects on Tifton 85 Bermudagrass Establishment using Rhizomes Matheus Baseggio, Yoana Newman,* Lynn E. Sollenberger, Clyde Fraisse, and Thomas Obreza
ABSTRACT As with stolons, planting rate of rhizomes is important for successful establishment of cultivar Tifton 85 bermudagrass (Cynodon spp.). Planting depth is another aspect to be considered when establishing rhizomes in soils with low moisture retention. Shallow planting can increase sprouting and emergence; but if rhizomes are placed too shallow they may dry out without irrigation. The overall objective was to evaluate the effect of rhizome planting rate and depth on establishment success. Treatments were the factorial combinations of three planting rates (Low–2.6 m3 ha –1, Medium–5.2 m3 ha –1, and High–10.4 m3 ha –1) and two planting depths (6 and 12 cm). High planting rate increased Tifton 85 frequency, ground cover, and herbage dry matter (DM), independent of planting depth. In both years, the High rate resulted in 100% grass frequency and ground cover before 120 d after planting. Also, this treatment produced more than 2300 kg DM ha –1 in the establishment year, and this was greater than the Medium and Low rates (1230 and 900 kg ha–1, respectively) when planted at 6 cm, or than the Low rate planted at 12 cm (1430 kg ha –1). When using Low or Medium rates, planting at a 12-cm depth, improved overall performance compared with 6 cm. Medium rhizome planting rate of ~5 m3 ha –1 at a 12-cm depth provided satisfactory ground cover and herbage DM at lower cost than High and thus is recommended for the sandy soils in the Suwanee River basin.
M. Baseggio, Plant Breeding and Genetics, Cornell Univ., Ithaca, NY 14853; Y. Newman, Plant and Earth Science, Univ. of Wisconsin– River Falls, WI 54022; L.E. Sollenberger, Agronomy, Univ. of Florida, Gainesville, FL 32611; C. Fraisse, Agriculture and Biological Engineering, Univ. of Florida, Gainesville, FL 32611; and T. Obreza, Soil and Water Science, Univ. of Florida, Gainesville, FL 32611. Received 4 Sept. 2014. Accepted 20 Oct. 2014. *Corresponding author (
[email protected]). Abbreviations: DAP, days after planting; DM, dry matter.
H
ybrid bermudagrasses are highly productive warm-season perennials, and Tifton 85, although considered an elite cultivar, requires vegetative propagation using either stolons or rhizomes (Burton et al., 1993; Hanna and Anderson, 2008). Planting rate of rhizomes is an important factor for successful establishment. Greater planting rates typically result in faster establishment (Stichler and Bade, 2003) and planting rate is often positively related to forage yield in the first year. Recommended rhizome planting rates range from 1.7 to 3.5 m3 ha–1, but these rates were determined on sandy-clay loam soils with good moisture and nutrient retention (Evers et al., 2002; Cosgrove and Collins, 2003). Following these recommendations on deep, sandy soils, which is where most hybrid bermudagrasses are used in Florida, can result in establishment failure (Newman et al., 2011). Information on appropriate planting rates under these conditions is needed. Additionally, one problem using dormant rhizomes is that half or more of them may be dead when planted and live ones may not have enough carbohydrate reserves to establish a live plant (Burton, 2011). Taliaferro et al. (2004) reported that planting rate can range up to 5.2 m3 ha–1 and Mueller et al. (1993) indicated that bermudagrass is usually planted at rates of 4.5 to 5.3 m3 ha–1.
Published in Crop Sci. 55:1338–1345 (2015). doi: 10.2135/cropsci2014.09.0605 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
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The faster a stand is desired, the more rhizomes should be planted (Stichler and Bade, 2003) and greater yields are expected in the first year. However, higher planting rates are only recommended if rhizomes are readily available or can be obtained at a low cost. Another important aspect of bermudagrass establishment using rhizomes is planting depth. Shallow planting can increase rhizome survival, sprouting and emergence, ground cover, and DM production (Chiles et al., 1966; Bourdôt, 1984; Chamblee et al., 1989). Placed too shallow, however, the rhizome may dry out without irrigation (Stichler and Bade, 2003) or be damaged by freezing temperatures (Burton et al., 1993). Although deep planting aids in winter survival and soil moisture retention, if planted too deep the new growth may die before emerging (Stichler and Bade, 2003). The different stratification of vegetative material in the soil profile has a strong influence on the establishment rate (Rizzo and Satorre, 1999). Stems distributed deeply in the soil require more thermal time than shallow planting to reach similar level of emergence (Satorre et al., 1996). The depth of planting is determined by the availability of moisture and the texture of the soil. Rizzo and Satorre (1999) observed an increase in the time for shoot emergence with a decrease in soil moisture. Chamblee et al. (1989) studied several hybrid bermudagrass cultivars and noticed a delay in sprout emergence and a decrease in percentage of rhizomes sprouting as planting depth increased from 2.5 to 10 cm. Phillips and Moaisi (1993) observed only a few shoots of bermudagrass emerged from rhizomes placed below 10 cm. Rizzo and Satorre (1999) observed a positive linear relationship of planting depth (to a maximum of 18 cm) and time to achieve 50% emergence. Montesbravo et al. (1985) observed greatest emergence when stolons and rhizomes were planted superficially or at a 5-cm depth, and emergence decreased at 10- and 15-cm depths. Chiles et al. (1966) and Bourdôt (1984) also found that rhizome survival, emergence, and DM production by aerial shoots decreased and time of emergence of the first shoots was delayed with increased planting depth. Deep (7.6 cm) horizontal placement of cultivar Coastal bermudagrass in March plantings resulted in May stands of only 36%, compared with 81% from the shallow depth (3.8 cm) and 70% from the vertical orientation (Chamblee et al., 1989). Under dry land conditions, planting rhizomes 5- to 8-cm deep is generally adequate, whereas under irrigation, planting should be at a depth of 4 to 5 cm with occasional rhizomes showing aboveground (Burton, 2011). Although this is the general recommendation, sandy soils with high permeability such as those in the Suwanee River basin may not hold enough moisture and thus deeper planting could be required. Considering those conditions, the hypothesis of this study was that deep planting and higher planting rates will improve establishment of Tifton 85 in excessively crop science, vol. 55, may– june 2015
drained coastal plain sandy soils. The objective was to quantify the effects of planting rates and depths on Tifton 85 plant frequency, ground cover, and herbage DM harvested.
MATERIALS AND METHODS Experimental Site This study was conducted from March 2012 to July 2013 in North Central Florida. In 2012, the study was located on a commercial cattle farm near Chiefland, Levy County (29°3037 N, 82°4849 W). In 2013, the experiment was conducted on a commercial dairy farm near Trenton, Gilchrist County (29°3212.47 N, 82°478.50 W). Both sites were within the Suwanee River basin and the soils were classified as Otela-Candler complex (loamy, siliceous, semiactive, thermic Grossarenic Paleudalf and hyperthermic, uncoated Lamellic Quartzipsamment), sandy and loamy marine deposits, with deep, rapidly permeable sands with very low water retention (Soil Survey Staff, 2013). At the first site, soil pH was 6 and organic matter was 4.1 g kg–1. Mehlich-3 extractable P, K, Mg, and Ca were 82 (High), 45 (Low), 65 (Medium), and 400 g kg–1, respectively, in 2011. At the second site, soil pH was 6.2, and Mehlich-1 extractable P, K, Mg, and Ca were 38 (optimum), 97 (medium), 65 (optimum), and 469 (optimum) g kg–1, respectively, in 2013.
Experimental Variables and Statistical Design The experimental variables were three rhizome planting rates (Low–2.6 m 3 ha–1; Medium– 5.2 m 3 ha–1; and High–10.4 m 3 ha–1) and two planting depths (6 and 12 cm). Treatments were arranged as random strips with four replicates, for a total of 24 experimental units. Each strip corresponded to a planting rate due to the restrictions imposed by planting equipment used. Depths were assigned to main plots and rates to subplots. Plots were 3 by 4.5 m (13.5 m 2). Planting rates were selected based on those used by producers. The Low rate (2.6 m 3 ha–1) is commonly used in the sandy soils of Florida. Greater rates were added to assess their establishment advantages. Depths were selected to avoid desiccation based on a range of possible settings of the planting implement.
Field Procedures Planting was conducted on 15 Mar. 2012 and 2 Mar. 2013. The material consisted of dormant rhizomes, which were dug from a nursery of Tifton 85 bermudagrass on a nearby farm and kept on ice until planted later that day to preserve their viability. Rhizomes were placed (without compressing) inside a small bucket with a volume of ~0.0223 m 3 (~0.66 bushel) to determine the average weight of planting material. The calculation to estimate the weight of one bushel was based on the average of 15 measurements. Rhizomes were planted using a 3-m wide Bermuda King sprig planter and followed with a rollerpacker to ensure good sprig-soil contact. Irrigation was applied using a center pivot and based on soil moisture. Irrigation began when estimated volumetric water concentration was 7% until it reached 10% or a maximum of 12 mm per irrigation cycle. Rainfall, evapotranspiration, and average daily minimum and maximum air temperature are shown in Fig. 1.
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Figure 1. Rainfall, evapotranspiration (ET), and average daily minimum and maximum air temperature (2 m) at Bronson station (FAWN, 2013). Horizontal bars indicate data collection period.
Response Variables and Sampling The response variables measured in this study were shoot emergence, bermudagrass frequency and ground cover percent, and herbage DM harvested, and they were evaluated as described in Baseggio et al. (2014). Emergence was evaluated by the number of new shoots in a 1- by 1-m quadrat placed in a fixed location in the middle of the plot. Shoots were counted every other week for 8 wk. After the first month, frequency and ground cover percentage were assessed weekly until harvest. Frequency and ground cover percentage were assessed in the middle of the plot using a 1 by 1-m frame divided into 25 squares and measured as described by Elzinga et al. (1998). Frequency was determined by the presence/absence of bermudagrass in each square, while cover percentage was assessed by the effective bermudagrass ground cover in the frame area. Frequency and ground cover were considered complete when percentage was above 80. Dry matter harvested was assessed about 4 mo after planting on 5 July 2012 and 24 June 2013. Samples from two circular quadrats of 45-cm diam., ~ 0.16-m 2 each, were hand 1340
clipped to 8-cm stubble height. Fresh weight was determined and the samples were dried at 60°C until constant weight to determine dry weight. Soil water content was taken using a FieldScout TDR moisture meter and two measurements were done at depths of 6 and 12 cm in each plot.
Statistical Analysis Emergence and herbage DM harvested data were analyzed using PROC MIXED procedures of SAS (SAS Institute, 2008). In all models, year, depth, and planting rate were considered fixed effects; replicates and their interactions were modeled as random effects; days after planting (DAP) was analyzed as repeated measure with a compound symmetry structure. For frequency and ground cover, data were analyzed for each year separately. When comparing more than two levels, mean separation was further accomplished using least-squares means and the PDIFF option in SAS, which gives a table of P values for all possible pairwise comparisons. All test differences were
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considered significant at P 0.05, while values at P 0.10 were further discussed as trends. Frequency and ground cover percent presented a sigmoidal shape characteristic of a logistic growth curve. Values started at zero and increased to a plateau at 100%. The nonlinear logistic model used is represented by the following equation: Frequency =
(1)
(1 + expx )
where x = + × DAP. The logistic regression was created using PROC NLIN procedure of SAS, and the approach is described by SAS Institute (2008). The comparison of curves was performed using a sum of squares reduction test, as described by UCLA: Statistical Consulting Group (2014).
RESULTS AND DISCUSSION Weight of Planting Material The weight of one bushel was highly variable throughout the measurements. It was very dependent on the amount of sand and moisture aggregated with the rhizomes and roots. The average weight of one bushel was 6.1 kg when considering the same material (rhizome + sand) and compression used at planting. If rhizomes were compressed as is commonly done by commercial sprig sellers that value could go to 8 kg per bushel. Taliaferro et al. (2004) indicated that the amount of rhizomes in a given volume varies with degree of compaction and physical characteristics. In fact, when only the material was used, without sand, the weight of one bushel was considerably lower (data not shown). This indicates the necessity of recommendation by volume instead of mass, as is already done for rhizomes. Since the mass is highly variable and a function of the amount of sand plus planting material, variation in actual planting rate can be decreased by using planting rates based on volume.
Emergence Emergence was assessed in 2012 and was affected by the interaction of DAP and treatment combination. First shoots started emerging earlier than 30 DAP. Fernandez (2003) reported bermudagrass emergence as soon as 11 DAP when using rhizome fragments. Phillips and Moaisi (1993) observed that emergence started 13 to 25 DAP bermudagrass rhizomes in Botswana, and Montesbravo et al. (1985) observed greatest emergence of bermudagrass occurred between 16 and 30 DAP. There was no difference among treatments at 29 DAP. At 36 DAP, the High rate planted at 12 cm presented the greatest emergence; other treatments did not differ. At 51 DAP, the same treatment still showed the greatest emergence, followed by the High rate at 6 cm and Medium rate at 12 cm. These results differ from those of Phillips and Moaisi (1993) who observed that only a few shoots emerged crop science, vol. 55, may– june 2015
from bermudagrass rhizomes placed below 10 cm in a sandy loam soil. The different soil type, with the presence of more clay, may have affected emergence in that study.
Frequency
There was interaction of DAP ´ depth ´ rate; therefore data were analyzed by treatment combination of rate ´ cover. Frequency demonstrated a logistic response (Fig. 2). Increase in frequency was slow initially, but was followed by a steep increase and then a gradual slowing to reach a plateau at 100%. When comparing within each planting rate, depth of planting was significantly different for Low and Medium rates in both years (Fig. 2). By increasing the planting depth from 6 to 12 cm, the frequency was improved when using both Low and Medium planting rates. At the 12-cm depth, the frequency started increasing considerably earlier and reached 100% before the 6-cm planting depth. Also, when using Low rate at a 6-cm depth, the frequency never surpassed 80% in both years, even after 114 DAP. For the High rate, however, difference between planting depths was less pronounced (2012) or nonexistent (2013). Both depths presented comparable frequency across the sampling dates and reached 80 or 100% at about the same time. This suggests that planting depth is important only when lower planting rates are used. If planting material is not readily available, a deeper planting depth should be used. It was expected that deep planting would delay the emergence and thus protect the new shoots from adverse environmental conditions that may happen if plants were to emerge too early. However, in this experiment, the response was actually the opposite, with the deep planting presenting higher number of shoots initially. Probably deeper planting allowed for moisture preservation under limited irrigation, contributing to increased emergence of rhizomes planted deeply compared with a more shallow planting (6 cm). Even under irrigated conditions, the sandy soils in this environment can dry rapidly leading to desiccation of planting material near the surface. Therefore, planting at 12 cm would keep more moisture close to the rhizome and thus favor its rooting and emergence. Soil moisture content was sampled at different depths on 17 July 2013, 5 d after a 14-mm rain. Moisture at the 6-cm depth was 8.3%, while at 12 cm it was 13.3%. Even though the water content at 6 cm was above the threshold to trigger an irrigation event (7%), it was significantly lower than at 12 cm, which means that planting material placed at the greater depth had more water available. After few days without a substantial rain or irrigation, soil moisture at 6 cm decreases faster than at 12 cm. Although we did not test if this reduction would be detrimental to the material planted at a shallow depth, our frequency and ground cover results suggest that the greater water content at 12 cm could have played a major role in the
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Figure 2. Bermudagrass frequency of occurrence following planting for two planting depths at each of three planting rates (Low, 2.6 m3 ha–1; Medium, 5.2 m3 ha–1; and High, 10.4 m3 ha–1) in 2012 and 2013. Curves with the same letter do not differ (P > 0.05).
better performance of this treatment. Rizzo and Satorre (1999) reported an increase in time for emergence with a decrease in soil moisture.
Ground Cover
There was interaction of DAP ´ depth ´ rate and data were analyzed by the six combinations of depth and rate. Ground cover also demonstrated a logistic response to DAP (Fig. 3). Similar to frequency, planting depth was only significant for Low and Medium rates. When planted at a 6-cm depth, ground cover was not satisfactory until the last sampling date (about 114 DAP) for Low and Medium rates. In 2012, the Low rate at 6 cm presented ground cover lower than 3%, indicating that most of the material died before emerging. The following year, this treatment performed better, but still had only about 60% 1342
ground cover, whereas the same planting rate at 12 cm showed more than 90% ground cover. With greater planting rates, however, no difference between planting depths was observed either in 2012 or 2013. Ground cover for the High rate was similar for both depths across the sampling period and reached 80% at about 85 and 101 DAP in 2012 and 2013, respectively. Rodriguez et al. (2001) tested different fertilizer ratios on a sandy soil and found 100% of ground cover during bermudagrass establishment over a range of 5 to 11 wk after planting. Treatments in the current experiment took more than 14 wk to reach 100%. The rapid establishment in their experiment, however, was achieved using a very high fertilization of 49 kg N ha–1 wk–1. In general, High planting rate presented greater ground cover during the growing season. In some cases
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Figure 3. Bermudagrass ground cover following planting for two planting depths at each of three planting rates (Low, 2.6 m3 ha–1; Medium, 5.2 m3 ha–1; and High, 10.4 m3 ha–1) in 2012 and 2013. Curves with the same letter do not differ (P > 0.05).
when less planting material was used but depth was greater, ground cover was comparable to that when using higher rates. This occurred in 2013 when Medium and High rates planted at a 12-cm depth showed similar ground cover. Therefore, when material is not readily available, deep planting at 12 cm seems to improve establishment.
Herbage Dry Matter Harvested
There was planting depth ´ planting rate interaction for herbage DM harvested; main effect of year was also significant. Although the first year presented in general lower DM than in 2013, treatments showed a similar pattern of response in both years. When planted at 6 cm, the High rate had greater DM than both Medium and Low rates, and the latter treatments did not differ (Table 1). At 12 cm, there was no difference among rates (P < 0.05); crop science, vol. 55, may– june 2015
Table 1. Rhizome planting depth ´ planting rate interaction for dry matter harvested measured 115 d after planting. Planting rate†
Depth, cm 6
12
—————— kg ha —————— 900b§ 1430b 1230b 2206a 2700a 2303a
P value‡
–1
Low Medium High
0.2363 0.0205 0.3232
†
Low–2.6 m3 ha –1, Medium–5.2 m3 ha –1, and High–10.4 m3 ha –1.
‡
P value for comparison of planting depth means within a planting rate.
§
Means within a column followed by the same letter do not differ (P > 0.10).
however, Medium and High rates approached superior performance relative to Low (P < 0.10). When comparing depths within each rate, it was significant only for the Medium rate. When planted at 12 cm, the Medium
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Figure 4. Regression for dry matter (DM) harvested in response to planting rate measured 115 d after planting in 2012 and 2013.
rate yielded 2200 kg ha–1, while at 6 cm the DM for this treatment was only 1230 kg ha–1. Similar to frequency and ground cover, when the planting rate was High, there was no effect of planting depth. When planting rate was Medium, DM harvested increased at 12 vs. 6 cm. Using the Low rate, however, there was no increase in DM when using the 12-cm depth, in contrast to what was observed for frequency and ground cover. When analyzed using regression, there was a linear increase in herbage DM harvested with an increase in the planting rate for both years (Fig. 4). In 2012, each additional cubic meter planted resulted in 120 kg ha–1 more DM harvested 4 mo later. In 2013, all planting rates performed better and the increase per unit of additional planting material was also greater; for each 1 m 3, the DM increased about 225 kg ha–1. Bermudagrass herbage DM production in 2012 was lower than found by Keeley and Thullen (1989), who planted bermudagrass using plugs in a fine sandy loam soil in California. Following planting on 1 March, oven-dry weight of culms and stolons was 1870 kg ha–1 about 3 mo after planting. Their methods, however, are not clear, and it seems they harvested the whole plant (above and below parts). If so, this dry weight would take into account stolons that are close to the ground and that were not harvested in the present study. In 2013, however, our study showed yields above 1900 kg ha–1 even for the Low rate.
Rhizome Planting Costs Rhizome planting material is the greatest expense associated with establishment. Depending on the planting rate used, the size of the field that can be planted varies considerably. The approximate rhizome yield of a nursery ranges from 130 to 174 m3 ha–1. For the following calculations we will consider the average rhizomes yield to be 152 m3 ha–1. Considering planting rates used in this study, with 1 ha of nursery 1344
Table 2. Number of hectares that can be planted with a 1-ha nursery and cost of planting material for each planting rate using rhizomes. Planting rate Low Medium High
Rate
1 ha of nursery can plant
Cost
m3 ha –1 2.6 5.2 10.4
ha 58 29 15
$ ha –1 295 590 1181
it would be possible to plant 58 ha using the Low rate (2.6 m3 ha–1; Table 2). On the other hand, if the High rate (10.4 m3 ha–1) is used, only 15 ha can be planted from the same nursery. Therefore, about 3.9 times additional nursery land is required to plant the same amount of new land. In addition, if the producer does not have area available to keep a nursery, he will have to buy the material or hire somebody to do the work and then the costs will be even higher. Considering the price of each bushel (0.035 m 3) of Tifton 85 rhizomes is US$4 ($114 m–3), the costs of planting material alone are presented in Table 2. Also, the price to plant into a prepared seedbed is about $185 ha–1. Therefore, using a recommended rate of 2.6 to 3.3 m 3 ha–1, the cost of planting, including the rhizomes, is $482 to $561 ha–1. Additional costs for spraying herbicide before and after planting apply as well as disking and rolling. Although the High rate produced twice as much DM as the Medium rate at 6 cm (Table 1), there was no difference when planted at 12 cm. In this manner, if equipment is available, the recommendation would be to plant at 12-cm deep using Medium rate. Considering the Low rate, it costs 38% less than Medium rate ($480 vs. $775). However, the low rate produced only 65% as much DM harvested as the Medium rate, even at 12 cm. Because of this and since the Medium rate showed significantly greater ground cover than Low rate, the Low
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rate is not recommended for sandy soil conditions like those in the current study. In general, the Medium rate provided the greatest cost-benefit among the rates studied.
CONCLUSIONS AND IMPLICATIONS Use of the High rhizome planting rate resulted in more shoots m–2 than Medium and Low rates. Deep rhizome planting improved the emergence for Medium rate at 51 DAP. For bermudagrass frequency and ground cover, depth of planting had an effect only for Low and Medium rates. Planting at 12 cm accelerated the development of ground cover and the planted area was totally covered more quickly. Using the High rate, both depths performed similarly. When planted at a 6-cm depth, the High rate had greater DM harvested than Medium and Low rates, which did not differ. When planted at 12 cm, the Medium rate produced similar DM as the High rate and both yielded more than the Low rate. The Medium rate appears to provide the best compromise between establishment performance and costs associated with planting. Under sandy soil conditions such as those in the Suwanee River basin, the Medium rhizome planting rate (~5 m 3 ha–1) is recommended in conjunction with a planting depth of 12 cm. Low rate is not recommended for sandy soil conditions similar to those in the current study. References Baseggio, M., Y.C. Newman, L.E. Sollenberger, C. Fraisse, and T. Obreza. 2014. Stolon type and soil burial effects on Tifton 85 bermudagrass establishment. Crop Sci. 54:2386–2393. doi:10.2135/ cropsci2014.01.0089 Bourdôt, G.W. 1984. Regeneration of yarrow (Achilleamillefolium L.) rhizome fragments of different length from various depths in the soil. Weed Res. 24:421–429. doi:10.1111/j.1365-3180.1984. tb00605.x Burton, G.W. 2011. Establishing and managing the Tifton forage bermudagrasses. The Univ. of Georgia. www.tifton.uga.edu/ fat/formanag.htm (accessed 23 May 2013). Burton, G.W., R.N. Gates, and G.M. Hill. 1993. Registration of ‘Tifton 85’ bermudagrass. Crop Sci. 33:644. doi:10.2135/cropsci 1993.0011183X003300030045x Chamblee, D.S., J.P. Mueller, and D.H. Timothy. 1989. Vegetative establishment of three warm-season perennial grasses in late fall and late winter. Agron. J. 81:687–691. doi:10.2134/agronj1989.0 0021962008100040025x Chiles, R.E., W. Huffine, and J.Q. Lynd. 1966. Differential response of Cynodon varieties to type of sprig storage and planting depth. Agron. J. 58:231–234. doi:10.2134/agronj1966.00021962005800020036x Cosgrove, D.R., and M. Collins. 2003. Forage establishment. In: R.F Barnes et al., editors, Forages: An introduction to grassland agriculture. Vol. 1, 6th ed. Iowa State Press, Ames. p. 239–261.
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Elzinga, C.L., D.W. Salzer, and J.W. Willoughby. 1998. Measuring and monitoring plant populations. Technical Reference 1730-1. U.S. Dep. of the Interior, Bureau of Land Management, Denver, CO. Evers, G.W., M.J. Parsons, and T.J. Butler. 2002. Comparison of seeded and vegetatively planted bermudagrasses. Research Center Technical Rep. no. 2002-1.Texas A&M Univ., Overton. p. 41–42. FAWN. 2013. Florida automated weather network. http://fawn.ifas. ufl.edu/data/reports (accessed 5 May 2013). Fernandez, O.N. 2003. Establishment of Cynodon dactylon from stolon and rhizome fragments. Weed Res. 43:130–138. doi:10.1046/ j.1365-3180.2003.00324.x Hanna, W.W., and W.F. Anderson. 2008. Development and impact of vegetative propagation in forage and turf bermudagrasses. Agron. J. 100:103–107. doi:10.2134/agronj2007.0135 Keeley, P.E., and R.J. Thullen. 1989. Influence of planting date on growth of bermudagrass (Cynodon dactylon). Weed Sci. 37:531–537. Montesbravo, E.P., R. Labrada, and M. Duarte. 1985. Aspectos biológicos de Cynodon dactylon. I. Germinación y brotación de semillas y de partes vegetativas. Agrotecnia de Cuba 17:69–77. Mueller, J.P., J.T. Green, Jr., D.S. Chamblee, J.C. Burns, J.E. Bailey, and R.L. Brandenburg. 1993. Bermudagrass management in North Carolina. AG-493. North Carolina Coop. Ext., North Carolina State Univ., Raleigh. Newman, Y.C., J.M.B. Vendramini, C.G. Chambliss, F.A. Johnson, and M.B. Adjei. 2011. Bermudagrass production in Florida. Univ. of Florida Inst. of Food and Agric. Sci., Gainesville. http:// edis.ifas.ufl.edu/aa200 (accessed 26 May 2013). Phillips, M.C., and K. Moaisi. 1993. Distribution of rhizomes and roots of Cynodon dactylon in the soil profile and effect of depth of burial on regrowth of rhizome fragments. Brighton Int. Crop Protection Conference, Weeds. Vol. 3, Brighton, UK. 22–25 Nov. 1993. p. 1167–1170. Rizzo, F.A., and E.H. Satorre. 1999. Establecimiento de gramón (Cynodon dactylon L. Pers.) a partir de estructuras vegetativas. Rev. Facultad de Agronomía.19:11–20. Rodriguez, I.R., G.L. Miller, and L.B. McCarty. 2001. Bermudagrass establishment on high sand-content soils using various N-P-K ratios. HortScience 37:208–209. SAS Institute. 2008. SAS/STAT® 9.2 user’s guide. SAS Inst., Cary, NC. Satorre, E.H., F.A. Rizzo, and S.P. Arias. 1996. The effect of temperature on sprouting and early establishment of Cynodon dactylon. Weed Res. 36:431–440. doi:10.1111/j.1365-3180.1996.tb01672.x Soil Survey Staff. 2013. Web soil survey. USDA, NRCS. http://websoilsurvey.nrcs.usda.gov/ (accessed 10 Apr. 2013). Stichler, C., and D. Bade. 2003. Forage bermudagrass: Selection, establishment and management. E-179 4-03. Texas A&M Univ., College Station. Taliaferro, C.T., F.M. Rouquette, and P. Mislevy. 2004. Bermudagrass and stargrass. In: L.E. Moser, B.L. Burson, and L.E. Sollenberger, editors, Warm-season (C4) grasses. ASA, CSSA, and SSSA, Madison, WI. p. 417–475. UCLA: Statistical Consulting Group. 2014. Nonlinear regression in SAS. Inst. for Digital Res. and Education-Univ. of California, Los Angeles. www.ats.ucla.edu/stat/sas/library/SASNLin_ os.htm (accessed 18 June 2014).
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