Crop Science Journal of Natural Resources and Life Sciences Education
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online 24 February 2006
Published in Crop Sci 46:847-853 (2006)
© 2006 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Paré, K.
Right arrow Articles by Dionne, J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Paré, K.
Right arrow Articles by Dionne, J.
Agricola
Right arrow Articles by Paré, K.
Right arrow Articles by Dionne, J.
Related Collections
Right arrow Turfgrass Management
Right arrow Nitrogen
Right arrow Turfgrass
Right arrow Nutrient Management

TURFGRASS SCIENCE

Nitrogen Uptake and Leaching under Annual Bluegrass Ecotypes and Bentgrass Species

A Lysimeter Experiment

K. Paréa, M. H. Chantignyb, K. Careyc, W. J. Johnstona and J. Dionned,*

a Dep. of Crop and Soil Sciences, Washington State Univ., Pullman, WA 99164-6420
b Agriculture and Agri-Food Canada, Sainte-Foy, QC, Canada G1V 2J3
c Dep. of Plant Agriculture, Univ. of Guelph, Guelph, ON, Canada N1G 2W1
d Royal Canadian Golf Assoc., Golf House, 1333 Dorval Dr., Oakville, ON, Canada L6M 4X7

* Corresponding author (jdionne{at}rcga.org)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Nitrate (NO3–) can leach from golf greens, potentially causing the degradation of surface and ground water quality. A greenhouse experiment was conducted with 11 annual bluegrass (Poa annua var. reptans Hausskn.) ecotypes from eastern Canada (Quebec and Ontario) and the USA, and three bentgrass (Agrostis spp.) species to compare N uptake and potential for N leaching. Two-month-old grasses were established for a 6-wk period in lysimeter columns simulating a golf-green profile. An unplanted root zone control was included. Water-soluble fertilizer was applied at 25 kg N ha–1 (NH4NO3) every 14 d for 57 d. Leachate samples were collected every second day and analyzed for NO3–N and ammonium N (NH4–N) content. Dry weight and N concentration were determined on clippings, shoots, and roots. Ammonium N leaching was negligible for all grasses. Less NO3–N leaching losses occurred under bentgrasses (6–11% of applied N) than under annual bluegrasses (28–71% of applied N). Differences in NO3–N leaching were also found within annual bluegrasses; Quebec P. annua > Ontario P. annua > USA P. annua. Grasses with a greater aboveground biomass developed a larger and deeper root system and were associated with a greater N uptake (r = 0.94) and, therefore, a lower NO3–N leaching (r = –0.94). Breeding programs and management practices to improve turfgrass root development appear to be critical to reduce fertilizer N leaching under sand-based putting greens.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
GOLF COURSES may represent a significant environmental issue because of the potential for ground water contamination by NO3– from fertilizers (Petrovic, 1990). Putting greens are of particular concern because the root zone is often made of high-porosity sand mixtures to prevent compaction and water logging. Sand-based root zones have little capacity to retain nutrients or water, and frequent N applications and irrigations are required (Brown et al., 1982; Bigelow et al., 2001). Under these conditions, NO3– leaching can be high (Brown et al., 1982; Mancino and Troll, 1990; Shuman, 2001).

Management factors known to affect NO3– leaching under golf green conditions include irrigation volume, application rate and timing, and source of N fertilizers (Petrovic, 1990). Management practices need to optimize N uptake by turfgrasses to reduce the risk of NO3– leaching. Petrovic (1990) reported N uptake ranging from 5 to 74% of applied N. Differences in N uptake and utilization as well as differences in N leaching patterns have been reported among turfgrass species and cultivars (Cisar et al., 1989; Liu et al., 1997; Jiang and Hull, 1998; Jiang et al., 2000; Bowman et al., 2002). Some of the variations in N uptake efficiency may be due to morphological and physiological differences among grasses (Carrow et al., 2001). The morphology and the depth of root development appear to be important factors affecting N uptake (Bowman et al., 1998; Sullivan et al., 2000).

In Canada, creeping bentgrass (A. stolonifera L.) and annual bluegrass are cultivated on 53 and 36% of the golf greens, respectively (Royal Canadian Golf Association, 2003). However, little is known about N uptake efficiency and N leaching under golf greens cultivated with bentgrass or annual bluegrass. The objective of this research was to compare, in a greenhouse experiment, N uptake and potential mineral N leaching among various annual bluegrass ecotypes and bentgrass species grown in lysimeter columns simulating a golf-green profile.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
A lysimeter experiment was conducted in a greenhouse at the Univ. of Guelph, Guelph, ON, Canada. During the 57-d experimental period (October to December 2002), air and root zone temperatures were monitored with a data logger (HOBO, PRO series, Onset Computer Corporation, Bourne, MA). The mean daily air and root zone temperatures at the 5-cm depth were 22.8 ± 2.1°C and 17.0 ± 0.6°C, respectively. The photoperiod was 16 h d–1 with supplemental high-pressure sodium lighting (PAR, 80 µmol m–2 s–1) for the duration of the experiment.

Plant Material and Culture
The plant material consisted of 11 annual bluegrass ecotypes and three bentgrass species. Six annual bluegrass ecotypes were grown from tillers selected from golf greens, at different geographical locations, on the basis of their potentially superior turf characteristics. Three ecotypes were selected in the province of Quebec, Canada (Bic, Québec City, and Montebello; mean annual temperature, 4.7°C; mean annual precipitation, 1011 mm), and three were selected in the Guelph area in Ontario, Canada (mean annual temperature, 6.5°C; mean annual precipitation, 769 mm). Finally, five USA ecotypes were selected from tillers grown for 6 wk from seeds planted in 10-cm-diam. pots containing sand–peat root zone mixture. The seeds were provided by Dr. David Huff (Pennsylvania State Univ.) and the ecotypes were originally collected in the Mid-East region of the USA (mean annual temperature, 9.5°C; mean annual precipitation, 813 mm).

The bentgrass species were creeping bentgrass (‘Penncross’ and ‘Penn-A4’), dryland bentgrass (A. castellana Boiss. & Reut. cv. ‘Highland’), and velvet bentgrass (A. canina L. cv. ‘Vesper’). As with the USA annual bluegrass ecotypes, the bentgrasses were selected from tillers grown from commercial seeds planted in 10-cm-diam. pots for a 6-wk period.

All individual tillers were transplanted into 3.8-cm-diam., 14.0-cm-high cylindrical containers (conetainers, RL C7 Stuby Cell, Stuewe and Sons, Inc., Corvallis, OR) filled with a 80:20 sand–peat mix (v/v) and were grown in a greenhouse. Plants were irrigated as needed, fertilized twice a week (20–8–20; 250 mg N L–1, Plant-Prod, Plant Products Co. Ltd., Brampton, ON, Canada) and clipped weekly with scissors to approximately 1 cm.

Lysimeter Columns and Plant Establishment
Lysimeters were constructed using opaque polyvinyl chloride columns (10-cm diam., 40-cm depth). A cone collector was sealed to the bottom of each lysimeter and was connected to a 500-mL bottle by a tygon tube. The cone collector section of each lysimeter was filled with 10 cm of pea gravel ({approx}6- to 10-mm diam.) overlaid with 30 cm of a 80:20 (v/v) sand–peat root zone mixture. Materials used in the root zone mixture (Table 1) were selected to meet the standards of a golf green profile as stipulated by the United State Golf Association (USGA Green Section Staff, 1993). After {approx}2 mo of growth, turfgrass from seven containers of the same species, cultivar, or ecotype were transplanted into each lysimeter (experimental unit); four lysimeter columns (replications) were prepared for each turfgrass. In addition, four unplanted root zone lysimeters were included as a control treatment for a total of 64 lysimeter columns.


View this table:
[in this window]
[in a new window]
  		Table 1. Physical properties of the root zone mix used in lysimeter columns.{dagger}

 
At initiation of the experiment the turf was approximately 3.5 mo old; that is, 2 mo of growth in containers and a 6-wk establishment period to obtain a solid stand of grass in the lysimeters. During the 6-wk establishment period, plants were irrigated twice a day with 150 mL of deionized water, fertilized twice a week with 75 mL of a fertilizer solution (20–8–20, equivalent to 24 kg N ha–1), and clipped once a week to {approx}1 cm. Two weeks before starting the experiment, fertilization was stopped and the lysimeters were irrigated with 150 mL of deionized water twice a day to leach residual fertilizer N from the lysimeters.

Fertilizer Application, Irrigation, and Leachate Sampling
One hundred fifty milliliters of a water-soluble fertilizer was applied every 14 d, and the lysimeters were manually irrigated with 150 mL of deionized water poured from a beaker every other day. This is equivalent to a depth of 1.9 cm lysimeter–1 per application. Nitrogen was applied as ammonium nitrate (34–0–0; 25 kg N ha–1) and P and K were supplied using mono-potassium phosphate (0–52–34; 5.5 kg P ha–1 and 6.8 kg K ha–1) and potassium chloride (0–0–62; 8.8 kg K ha–1). This would compare to yearly application rates of 350 kg N ha–1, 77 kg P ha–1, and 218.4 kg K ha–1 based on a 7-mo growing season, which is typical of golf green management in the Quebec and Ontario areas. Micronutrients were supplied according to the manufacturer's (Micronutrient Mix For Turf, Plant Products Co. Ltd., Brampton, ON, Canada) recommendation (21 g Micronutrient Mix 100 m–2; Fe 7.0%, Mg 2.9%, Mn 2.0%, B 1.0%, Cu 0.1%, Zn 0.4%, and Mo 0.06%). For each lysimeter, the total volume of leachate was measured the day following each irrigation and a subsample was collected and stored in a 15-mL-polypropylene tube at 4°C for later quantification of mineral N concentration.

Plant and Root Zone Sampling
Plants were clipped once a week to approximately 1 cm; only a few millimeters of shoot tissues were removed at each clipping. The harvested clippings were dried at 60°C (48–72 h), weighed, and pooled over the duration of the experiment for analysis. At the end of the experiment, the root zone core in each lysimeter column was divided into three sections: 0- to 5-, 5- to 10-, and 10- to 40-cm depth; the last section included the gravel layer. Roots were manually separated from the root zone in each section and then gently washed with tap water to remove any adhering material, which was discarded. Shoots were cut to the crown, weighed after drying at 60°C (48–72 h), and combined with the clippings for analysis; the crown was included with roots in the 0- to 5-cm section. Root dry weight was measured for each section after drying at 60°C (48–72 h). A root zone sample was also collected from each section and air-dried for later N analysis.

Leachate, Plant, and Root Zone Analyses
All leachate samples were analyzed for NO3–N and NH4–N concentration with a segmented flow colorimeter (Technicon Model Traacs 800, Pulse Instrumentation, Ltd., Saskatoon, SK, Canada). Ammonium N concentration in leachates was typically below the detection limit (<0.5 mg L–1). Total amount of NO3–N in each leachate sample was calculated by multiplying NO3–N concentration by the total volume of leachate. Cumulative NO3–N losses were calculated by summing the amounts of NO3–N collected from each lysimeter. For each lysimeter, a linear regression curve was fitted to the cumulative NO3–N data and the slope of the curve was used as an estimate of the mean daily rate of NO3–N leaching.

Root zone, plant aboveground biomass (clippings plus shoots), and roots were analyzed for total N content by dry combustion with an elemental analyzer (Model LECO CNS-1000, Leco Corp., St. Joseph, MI). Nitrogen concentration in the root zone samples was below the detection limit (<0.05% dry wt.) for all lysimeter columns. N uptake was calculated by multiplying the dry weight of the clippings plus shoots and roots by their respective N concentrations. Total plant N uptake was not corrected for N in shoots and roots at the beginning of the experiment.

Experimental Design and Statistical Analyses
The experiment consisted of 16 treatments (11 annual bluegrasses, four bentgrasses, and one unplanted root zone control) and four replicates arranged as a randomized complete-block design. All statistical analyses were performed using SAS v. 8 (SAS Institute, 1999). Slopes of the cumulative NO3–N losses were obtained by linear regression using the REG procedure. An ANOVA was performed using the GLM procedure. Treatment means were compared using a priori contrasts with the CONTRAST option of the GLM procedure. Type I error rate was set at P = 0.05 for all statistical tests.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Nitrate and Ammonium Leaching
Nitrate N accounted for >99% of total mineral N found in leachates. Ammonium N leaching was negligible under all grasses studied, most likely because of plant assimilation and rapid microbial immobilization and nitrification in the root zone. This is consistent with results from other greenhouse and field studies (Brown et al., 1982; Mancino and Troll, 1990; Bowman et al., 2002). In a laboratory experiment, Bigelow et al. (2001) found that sand amended with 20% by volume of sphagnum peat (the same sand–peat mixture used in our experiment) reduced NH4–N leaching loss by 59% when compared with a pure sand root zone.

The concentration of NO3–N in leachates fluctuated during each 14-d fertilizer application period (Fig. 1 ). In general, including the unplanted control, NO3–N concentration in the leachate increased 3 d after fertilizer application, peaked after 7 d ({approx}1–15, 20–40, and 40–55 mg NO3–N L–1 for the bentgrasses, annual bluegrasses, and unplanted control, respectively) and then decreased to {approx}3 and 10 mg L–1 for the grasses and unplanted control, respectively, until the next fertilizer application. This cyclic pattern in NO3–N leaching is reflected in the sigmoidal shapes of the cumulative NO3–N leaching curves (Fig. 2 ). Total NO3–N leaching losses, using single degree of freedom contrasts, were in the following order: unplanted control > Quebec P. annua > Ontario P. annua > USA P. annua > Agrostis spp. (Table 2).


Figure 1
View larger version (34K):
[in this window]
[in a new window]
  		Fig. 1. Concentration of NO3–N in leachates collected under annual bluegrass ecotypes from Canada and the USA, and bentgrass (Agrostis spp.) species grown in lysimeter columns for 57 d with fertilizer application every 14 d during 2002 at Guelph, ON, Canada. Arrows indicate the fertilizer treatment application day. Concentrations are averaged across ecotypes or cultivars.

 

Figure 2
View larger version (25K):
[in this window]
[in a new window]
  		Fig. 2. Cumulative NO3–N leaching under annual bluegrass ecotypes from Canada and the USA, and bentgrass species grown in lysimeter columns for 57 d with fertilizer application every 14 d during 2002 at Guelph, ON, Canada. Cumulative leaching is averaged across ecotypes or cultivars.

 

View this table:
[in this window]
[in a new window]
  		Table 2. Mean daily rate and total nitrate N (NO3–N) leaching under annual bluegrass ecotypes and bentgrass species grown in lysimeter columns for 57 d with fertilizer application every 14 d during 2002 at Guelph, ON, Canada.

 
As expected, the unplanted control resulted in the greatest NO3–N leaching with losses representing 116% of the N applied (Table 2). Although some experimental error might have occurred in measuring total NO3–N leaching, cumulative losses > 100% of the applied N in the control lysimeters could also be attributed to mineralization and subsequent leaching of organic N present in the lysimeters at initiation of the experiment. Chapman (1994) and Brauen and Stahnke (1995) found NO3–N leachate concentrations > 15 mg L–1 under a sand-based putting green during bentgrass seedling establishment. This demonstrates the importance of N uptake in regulating fertilizer N leaching and stresses the need for careful adjustment of N fertilization during the establishment period of grasses to prevent excessive NO3– leaching when N uptake is low.

Differences in mean daily rate and total (cumulative value at 57 d) NO3–N leaching losses were observed among the grasses (Table 2). Total NO3–N leaching varied from 5 to 56 mg lysimeter–1, representing 6 to 71% of the N applied. In a 3-yr N leaching study on a golf green at Coeur d’Alene, ID, 48% of the applied N was recovered in creeping bentgrass clippings and 11% was recovered in the leachate (Johnston et al., 2001). This is in agreement with our work where 10 to 11% of the applied N was recovered in the leachates under creeping bentgrass (Table 2). P. annua Quebec ecotype 2 had the greatest numerical mean daily rate and total NO3–N leaching, while A. canina had the smallest values. Mean daily rate and total NO3–N leaching were greater under annual bluegrasses than under bentgrasses (Table 2). In addition, intraspecific differences were found among annual bluegrass ecotypes. Both the mean daily rate and total NO3–N leaching were as follows: Quebec P. annua > Ontario P. annua > USA P. annua. Differences in NO3–N leaching observed among the annual bluegrass ecotype groups could be a consequence of their adaptation to climatic conditions in their region of origin. Poole et al. (2005) reported that differences in P. annua morphology were related to regional climatic conditions. Interspecific differences were also observed among the bentgrasses. Both the mean daily rate and total NO3–N leaching under A. canina were smaller than under A. castellana and A. stolonifera; there were no differences between A. castellana and A. stolonifera (Table 2).

Plant Growth Characteristics and Nitrogen Uptake
Differences in growth characteristics were observed among the grasses (Table 3). Overall, annual bluegrasses had less clipping, shoot, and root dry weight when compared with the bentgrass species. The only exceptions were found with the Ontario and USA ecotypes, which had shoot dry weight similar to Agrostis spp. In addition, Ontario ecotypes had a root dry weight in the 0- to 5-cm depth similar to Agrostis spp. Total biomass production was as follows: A. canina > A. stolonifera = A. castellana > Ontario P. annua > USA P. annua > Quebec P. annua. For all grasses evaluated, the major portion of the total root biomass (65–90%) was located in the top 5 cm of the root zone; this is partly due to the inclusion of the crown with root materials at this depth. Total root biomass of the bentgrasses was also larger than the annual bluegrasses and developed deeper in the root zone (Table 3). Overall, total root biomass was in the following order: A. canina > A. stolonifera = A. castellana > Ontario P. annua = USA P. annua > Quebec P. annua.


View this table:
[in this window]
[in a new window]
  		Table 3. Dry weight characteristics of annual bluegrass ecotypes and bentgrass species grown in lysimeter columns for 57 d with fertilizer application every 14 d during 2002 at Guelph, ON, Canada.

 
The bentgrasses had a greater N uptake than annual bluegrasses for all parameters (Table 4). The only exceptions were for P. annua from Ontario and USA, which demonstrated N uptake in the roots similar to Agrostis spp. Quebec P. annua ecotypes had the smallest N uptake. This intraspecific and interspecific variability in N uptake agrees with the different N uptake efficiencies previously found among various grass species and cultivars (Liu et al., 1997; Jiang and Hull, 1998; Jiang et al., 2000).


View this table:
[in this window]
[in a new window]
  		Table 4. Nitrogen uptake of annual bluegrass ecotypes and bentgrass species grown in lysimeter columns for 57 d with fertilizer application every 14 d during 2002 at Guelph, ON, Canada.

 
Total N uptake was closely and positively correlated to total biomass (Fig. 3a ), whereas it was closely and negatively correlated to total NO3–N leaching (Fig. 3b). Thus, interspecific and intraspecific differences in NO3–N leaching were mainly attributed to differences in plant biomass. Grasses with a greater aboveground biomass generally had a greater root biomass (Table 3). In putting greens, where grass is mowed at short heights on a daily basis and exposed to stresses such as traffic and pests, the root system plays an important role in plant maintenance, recovery, and survival. It is logical to believe that plants with a larger root system exploit a greater root zone volume and have a greater potential to absorb nutrients. Sullivan et al. (2000) found that root morphological traits, such as length, surface, and volume are positively correlated with NO3– uptake rate in Kentucky bluegrass (Poa pratensis L.). In our experiment, the extensive root development in bentgrasses, compared to annual bluegrasses, was critical to reduce potential NO3–N leaching. Similarly, in a greenhouse experiment, Bowman et al. (1998) found that a deep-rooted creeping bentgrass genotype had half as much NO3–N leaching when compared with a shallow-rooted one. Since Lehman and Engelke (1991) found rooting characteristics to be a heritable trait in turfgrass, selection of ecotypes or cultivars with superior root development should be possible and could be used in turfgrass breeding programs.


Figure 3
View larger version (17K):
[in this window]
[in a new window]
  		Fig. 3. Relationships between (a) total N uptake and total biomass and (b) total N uptake and total NO3–N leached under various annual bluegrass ecotypes and bentgrass species grown in lysimeter columns for 57 d with fertilizer application every 14 d during 2002 at Guelph, ON, Canada.

 

   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
Bentgrasses were more efficient at preventing NO3–N leaching losses under sand-based root zones than annual bluegrasses, which could be explained by a greater aboveground biomass and root development (both total root biomass and its distribution deeper in the profile). Interspecific differences in NO3–N leaching were also found among bentgrasses; A. canina had less NO3–N leaching than A. castellana or A. stolonifera. In addition, intraspecific differences in NO3–N leaching were found within annual bluegrasses; Quebec P. annua > Ontario P. annua > USA P. annua. Consequently, identification of annual bluegrass ecotypes or bentgrass cultivars with improved root development is possible and can be used in breeding programs along with management practices to reduce N leaching under sand-based putting greens.


   ACKNOWLEDGMENTS
 
The authors would like to recognize assistance of Ms. Johanne Tremblay, Agriculture and Agri-food Canada, and Dr. David R. Huff, Pennsylvania State Univ. The Natural Sciences and Engineering Council of Canada, Royal Canadian Golf Assoc. Foundation, and Canadian Turfgrass Research Foundation provided financial support for this project.

Received for publication July 12, 2005.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 




This article has been cited by other articles:


Home page
 Crop Sci.Home page
E. C. Knight, E. A. Guertal, and C. W. Wood
Mowing and Nitrogen Source Effects on Ammonia Volatilization from Turfgrass
Crop Sci., July 30, 2007; 47(4): 1628 - 1634.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Paré, K.
Right arrow Articles by Dionne, J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Paré, K.
Right arrow Articles by Dionne, J.
Agricola
Right arrow Articles by Paré, K.
Right arrow Articles by Dionne, J.
Related Collections
Right arrow Turfgrass Management
Right arrow Nitrogen
Right arrow Turfgrass
Right arrow Nutrient Management

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Vadose Zone Journal
Journal of Natural Resources
and Life Sciences Education		 Soil Science Society of America Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome