Agronomy Journal 92:1117-1124 (2000)
© 2000 American Society of Agronomy
SOIL MANAGEMENT
Tillage Intensity, Mycorrhizal and Nonmycorrhizal Fungi, and Nutrient Concentrations in Maize, Wheat, and Canola
Ahmad Mozafara,
Thomas Ankenb,
Richard Ruha and
Emmanuel Frossarda
a Institute of Plant Sciences, Swiss Federal Inst. of Technology (ETH), Eschikon Experiment Station, Lindau, CH-8315 Switzerland
b Swiss Federal Research Station (FAT), Tänikon, CH-8356 Switzerland
ahmad.mozafar{at}ipw.agrl.ethz.ch
 |
ABSTRACT
|
|---|
Reduced tillage can change numerous physico-chemical properties of soil and the activity of various microorganisms including mycorrhizal and pathogenic soil fungi, and thus influence nutrient uptake by plant roots. We studied the colonization of roots by mycorrhizal and nonmycorrhizal fungi and nutrient concentrations in plant tops grown during a 3-yr rotation of maize (Zea mays L.), winter wheat (Triticum aestivum L.), and canola (Brassica napus L.) in two sites in Switzerland where fields have been under three tillage treatments (conventional, CT; chisel plow, CP; and no-tillage, NT) since 1987. Maize roots were colonized to a greater extent by mycorrhizal fungi with NT than with CP or CT treatments. Wheat roots were equally and weakly colonized by mycorrhizal fungi in all treatments but were relatively heavily (up to 35% of the root length) colonized by several nonmycorrhizal fungi such as Olpidium, Polymyxa, and Gaeumannomyces–Phialophora complex. Canola roots, as expected, were not colonized by any mycorrhizal fungi but were colonized by O. brassicae. Reduced tillage intensity altered the concentration of some nutrients in the leaves of mycorrhizal host plants (maize and wheat) but did not change those in nonhost canola. Changes in nutrient concentrations in maize and wheat leaves were likely due to the combined effects of colonization of their roots by various mycorrhizal and nonmycorrhizal fungi and not to some changes in the physical or chemical properties of soils. Cluster analysis showed that Mn concentration in wheat leaves was closely related to the Gaeumannomyces–Phialophora complex and concentrations of Ca, K, and Zn were related to tillage intensity and to the Polymyxa colonization of roots. We conclude that the colonization of roots by nonmycorrhizal root parasites, and especially by nonfilamentous obligate fungi, need to be taken into account in mycorrhizal studies conducted under field conditions.
|
INTRODUCTION
|
|---|
REDUCED SOIL TILLAGE increases the mycorrhizal colonization of plant roots (Douds et al., 1995; Kabir et al., 1997; McGonigle and Miller, 1996; Mulligan et al., 1985) and increases the concentration of P in plants (McGonigle and Miller, 1996; Miller et al., 1995). It is suggested that reduced tillage, by keeping the hyphal networks in soil intact, increases mycorrhizal activity in soil and thus increases nutrient uptake by plants (Miller et al., 1995). Reduced tillage intensity, however, can affect soil temperature (Carter and Barnett, 1987; Cox et al., 1990; Fortin, 1993; Drury et al., 1999) water content (Fortin, 1993; Drury et al., 1999), bulk density (Moreno et al., 1997), amount of organic C near the surface (Matowo et al., 1999), activity of phosphatases (Deng and Tabatabai, 1997), and the relative activity of soil fungi (Beare et al., 1997; Frey et al., 1999). Reduced soil tillage can also alter the activity of pathogenic fungi such as Gaeumannomyces graminis (agent of take-all disease) (Prew, 1981; Sturz et al., 1997) and its antagonist (Phialophora radicicola) (Yarham, 1979). Since infection of roots by G. graminis is shown to change the uptake of P, Ca, and K by plant roots (Hornby and Fitt, 1981), it is thus possible that part of the changes in nutrient concentration in plants under reduced tillage might be due to factors related to changes in the activity of nonmycorrhizal fungi colonizing the plant roots or in the soil's physico-chemical properties. One way of testing this would be to compare the effect of tillage intensity on the nutrient contents in mycorrhizal host plants (e.g., wheat and maize) with nonmycorrhizal plants (e.g., canola) and monitor colonization of roots by mycorrhizal and other soil fungi. We conducted such an experiment using field sites in Switzerland that have been under different tillage intensities since 1987.
|
Materials and methods
|
|---|
Experimental sites were two locations (Langwiese and Hausweid) at the Tänikon Experiment Station (46°30'N, 8°50'E) in the canton of Thurgau in Switzerland; since 1987 three tillage intensity treatments (conventional, CT; chisel plow, CP; and no-tillage, NT), in combination with two residue removal treatments (residues removed or left on soil surface), have been used. This field trial was set up to study the effect of long-term soil tillage on the chemical, physical, and biological properties of soils in Switzerland (Anken et al., 1997). In this area of Switzerland, crops are grown without irrigation since, on the average, there is enough rain during the growing season to cover the plant's need. For this study we took soil and plant samples from plots where plant residues were left on the soil surface. The 4-yr crop rotation has been winter wheat, maize, winter wheat, and canola. The experimental design is a randomized complete plot with four replications and the size of each subplot is 6 by 18 m. Planting density, weed control, and the amount of fertilizers applied to different treatments were according to the recommendation of Reckenholz Experiment Station (Switzerland) and were conducted similarly in all plots with the obvious difference that in the no-till method the fertilizers were left on the soil surface and not mixed into the soil by tillage operations, which resulted in the accumulation of P in the topsoil layers (Table 1)
. Other chemical and physical properties of these soils are shown in Table 2
.
View this table:
[in this window]
[in a new window]
|
Table 1 Concentrations of P at different soil depths at the two locations in response to conventional tillage (CT), chisel plow (CP), and no-tillage (NT) measured in August 1994 (7 yr after the start of different tillage treatments)
|
|
View this table:
[in this window]
[in a new window]
|
Table 2 Some properties of the dystric gleysol soils (0 to 25-cm depth) in Hausweid and Langwiese, which have been under different tillage intensity since 1987
|
|
We collected root and leaf samples from three crops grown in rotation during 3 consecutive years: maize cv. LG 22.53 (in 1996 from both locations), winter wheat cv. Boval (in 1997 from both locations), and canola cv. Capitol (in 1998 from Hausweid only). The trial at Langwiese, because of the high clay content in its soil, was considered too difficult to continue and was thus terminated in 1997. Depending on the size of the plants, between 5 and 10 plants (including the roots to the depth of 30 cm) were randomly sampled from each of the four replicated plots 4 to 5 times during the plant growth. Tops and subsamples of roots were dried at 85°C for 48 h and weighed. Samples of dried and ground plant tops were digested in a microwave digester (25 mg ground plant material, 2 mL H2O, 4 mL 65% HNO3, and 2 mL H2O2) and nutrients were measured with an inductively coupled plasma spectrophotometer (Perkin-Elmer ICP model 5500). Subsamples of mixed roots were stored in 2.5% acetic acid, stained by the method of Phillips and Hayman (1970), and the degree of root colonization (by mycorrhizal and nonmycorrhizal structures) was measured according to the magnified intersections method of McGonigle et al. (1990). All the nonmycorrhizal structures were counted collectively except on the last sampling date of wheat when four nonmycorrhizal structures could be identified and were thus counted individually. Analysis of variance was performed using the General Linear Model (GLM) procedure available from SAS (SAS Inst., 1985). Data for percent colonization of roots by mycorrhizal and nonmycorrhizal fungi were subjected to an arcsine transformation before ANOVA. Cluster analysis was performed using Statgraphics program.
|
Results and discussion
|
|---|
Yield
Yields of all three crops were significantly different between the two locations. Tillage and tillage x location effects were significant for the yields of wheat and canola, but not for maize. No-till reduced the yield of maize at Hausweid but did not affect the yields of wheat and canola (Table 3)
. Yield of winter wheat and canola at Langwiese were lower in the NT plots because of heavy weed infestation. Long-term data collected on the yield of different crops in rotation since 1988 at the two locations, however, show that, on the average, crop yields in location Hausweid have not been significantly affected by the tillage intensity. Yields were often lower in the NT than in other treatments at Langwiese, however, which has a heavier soil (Anken et al., 1997).
View this table:
[in this window]
[in a new window]
|
Table 3 Grain yield of maize, wheat, and canola in response to conventional tillage (CT), chisel plow (CP), and no-tillage (NT) measured in Hausweid and Langwiese
|
|
Mycorrhizal Fungus Colonization
No-till treatment significantly increased the colonization of maize roots by mycorrhizal fungi but did not affect that in wheat roots (Fig. 1
, Table 4)
. Mycorrhizal fungi (data not shown), as expected, did not colonize the roots of canola. The data are consistent with the other reports on the positive effect of reduced tillage on the colonization of roots of maize by mycorrhizal fungi (Douds et al., 1995; McGonigle and Miller, 1996) although the results are not always consistent (Gavito and Miller, 1998).
View larger version (34K):
[in this window]
[in a new window]
|
Fig. 1 Effect of soil tillage intensity (conventional, CT; no-till, NT) in Hausweid on the colonization of maize and wheat roots with mycorrhizal structures (hyphae, arbuscules, and vesicles) and nonmycorrhizal fungi during the plant growth in 1996 and 1997, respectively. For the sake of clarity of graphs, the graphs for chisel plow, which were mostly intermediate between the other graphs, are not shown. Error bars indicate ±1 SE
|
|
View this table:
[in this window]
[in a new window]
|
Table 4 Analysis of variance significance levels for colonization of plant roots by mycorrhizal hyphae (Hyp), arbuscule (Arb), and vesicle (Ves) and nonmycorrhizal fungal structures (non-vam) and nutrient concentrations in the plant tops
|
|
Nonmycorrhizal Fungi
Almost all of the roots studied contained one or more nonmycorrhizal fungi. Canola roots contained the lowest and those of wheat the highest number of nonmycorrhizal fungi (Tables 4–6)
. The most common of these fungi were O. radicale, O. brassicae, P. graminis, and G. graminis–P. radicicola complex (Fig. 2 , Table 5). Olpidium and Polymyxa species are obligate root parasites and are vectors of numerous soil-borne viruses of cereals and other crops (Agrios, 1997). Although colonization of roots by G. graminis–P. radicicola complex was increased in CP as compared with CT and NT, we did not notice any incidence of take-all disease (G. graminis) in the fields. A previous study on these fields, which monitored the incidence of eyespot disease of wheat (Pseudocercosporella herpotrichoides) during 1991, 1993, and 1995, showed that NT decreases the incidence of eyespot disease compared with CP and CT (Anken et al., 1997). Finally, it was very difficult to discern between mycorrhizal and nonmycorrhizal hyphae in the roots, especially in wheat roots that were strongly colonized by nonmycorrhizal structures. Thus, the data on the percentage of roots colonized by mycorrhizal hyphae (Fig. 1) need to be interpreted with due caution.
View this table:
[in this window]
[in a new window]
|
Table 5 Analysis of variance for the effects of location, tillage intensity, and interactions between them on the degree of colonization of wheat roots with mycorrhizal and some of the most frequent nonmycorrhizal fungi and the nutrient concentration in wheat leaf sampled on 18 June 1997
|
|
View this table:
[in this window]
[in a new window]
|
Table 6 Colonization of roots (% root length) of maize, wheat, and canola by nonmycorrhizal fungi in response to conventional tillage (CT), chisel plow (CP), and no-tillage (NT).
|
|
View larger version (78K):
[in this window]
[in a new window]
|
Fig. 2 Nonmycorrhizal fungi found on/in wheat roots. (Top) Groups of pigmented cells formed on root surface in response to halting of penetration by Gaeumannomyces–Phialophora and hyphe of these fungi on the root surface. (Bottom) Resting spores of Olpidium and cystosori of Polymyxa inside the root cells
|
|
Nutrient Concentration
The concentrations of nutrients in plants, depending on the crop under consideration and the sampling date (plant age), were affected differently by the soil tillage intensity (Table 4). Only the data for the concentrations of P, K, Ca, Mn, Zn, and Cu from CT and NT treatments from Hausweid are presented and will be discussed for the sake of clarity of graphs and brevity of discussions (Fig. 3 and 4)
.
View larger version (33K):
[in this window]
[in a new window]
|
Fig. 3 Effect of soil tillage intensity on the concentrations of P, K, and Ca in the tops of maize, wheat, and canola during the plant growth in Hausweid. For the sake of clarity of graphs, the graphs for chisel plow, which were mostly intermediate between the other graphs, are not shown. Error bars indicate ±1 SE
|
|
View larger version (35K):
[in this window]
[in a new window]
|
Fig. 4 Effect of soil tillage intensity on the concentrations of Mn, Zn, and Cu in the tops of maize, wheat, and canola during the growing season in Hausweid. For the sake of clarity of graphs, the graphs for chisel plow, which were mostly intermediate between the other graphs, are not shown. Error bars indicate ±1 SE
|
|
The concentrations of P, Ca, Fe, Mn, Zn, and Cu in maize and those of P, K, Ca, Mg, Mn, and Zn in wheat were affected by soil tillage intensity. Concentration of no element in canola was affected by the tillage intensity (Table 4). The concentrations of P, Zn, and Cu in maize and those of P, K, Mn, and Zn in wheat were higher in the tops of plants under NT than under CT at most sampling dates. In contrast, and especially at the early stages of growth, the concentrations of Ca and Mn in maize and that of Ca in wheat were higher in CT than in NT.
Considering the reports that obligate parasitic fungi of roots may also affect the uptake of some nutrients by plant roots (Hornby and Fitt, 1981), we performed cluster analysis on the relationships between the percent colonization of wheat roots by various mycorrhizal and nonmycorrhizal structures and the concentration of nutrients in the wheat tops using the data from the last sampling date of wheat. The results show four distinct clusters: (i) mycorrhizal structures are clustered together with Olpidium; (ii) location of growth is clustered with Mg, P, Cu, and Fe; (iii) Mn is clustered with the Gaeumannomyces–Phialophora complex; and (iv) tillage is clustered with Polymyxa fungi and Ca, K, and Zn (Fig. 5)
. As expected, a close relationship existed between the occurrence of mycorrhizal hyphae, arbuscules, and vesicles in the roots. The clustering of Olpidium species with these mycorrhizal structures is surprising. Schönbeck and Dehne (1979) noted that lettuce (Lactuca sativa L.) root sections heavily infected with mycorrhiza were less colonized by O. brassicae. Since at no time were both Olpidium and mycorrhizal structures present in the same cell, this may be related to the effect of mycorrhizal fungi in changing the resistance of cells to other fungal parasites. St. Arnaud and coworkers (St. Arnaud et al., 1994) found that the pathogenic fungus Pythium ultimum did not affect the colonization of Tagetes patula roots with mycorrhizal fungi (Glomus intraradices) but G. intraradices reduced the colonization of plant roots with Pythium ultimum and that this effect was not related to the P nutrition of the plants. Our observation on the clustering of Polymyxa with tillage intensity and the concentrations of K and Zn indicates a possible effect of this fungus, whose presence was strongly affected by tillage as observed by ANOVA (Tables 5 and 6), upon uptake or translocation of these nutrients. Another nutrient whose concentration in wheat was related to a nonmycorrhizal fungus was that of Mn, which showed a relationship with Gaeumannomyces– Phialophora complex in the roots. This finding is consistent with other reports on the role of G. graminis in the Mn nutrition of plants. For example, Mn deficiency in wheat was noted to increase its susceptibility to G. graminis (Brennan, 1992; Graham and Rovira, 1984) and Mn fertilization can decrease take-all disease (Wilhelm et al., 1988). Wheat roots infected with G. graminis were shown to cause a strong oxidation of Mn2+ to Mn4+, which precipitates and was observed in the interior of roots (Schulze et al., 1995). Rengel (1997) noted that the lower the capacity of an isolate of this fungi to oxidize Mn2+ into plant-unavailable Mn3+ and/or Mn4+, the lower its virulence to cause take-all disease.
View larger version (24K):
[in this window]
[in a new window]
|
Fig. 5 Dendrogram from the cluster analysis (using Ward's linkage and Squared Euclidean) for the colonization of wheat roots by various mycorrhizal structures and nonmycorrhizal fungi and the concentrations of various mineral nutrients in the plants tops
|
|
Reports on the activity of mycorrhizal fungi in relation to plant growth or nutrient uptake under nonsterile field conditions have almost unanimously ignored the possible roles of nonmycorrhizal and other root-colonizing fungi. These include reports on the effect of reduced soil tillage and fertilization (Fairchild and Miller, 1990; Gavito and Miller, 1998; Kabir et al., 1997; McGonigle and Miller, 1996; Tarkalson et al., 1998); cropping systems (Johnson et al., 1992; Khalil et al., 1992; Kurle and Pfleger, 1996; Rillig et al., 1998) and the uptake of nutrients using unsterile field soil plus some mycorrhizal isolates (Kim et al., 1998). The rooting substrate is sterilized in almost all studies involving mycorrhiza. In some cases only a filtrate of soil, which conceivably contained only soil bacteria, is added. These procedures, despite their merits, simply ignore the role other fungi may play under natural field conditions.
Our observations show that under field conditions one or more nonmycorrhizal fungi may always be concomitantly present with mycorrhizal fungi in the roots of most plants. It is thus very hard to draw any inferences as to the specific and direct role of increased activity of mycorrhizal fungi under reduced tillage for the changes observed in nutrient concentration. This view is supported by the finding that tillage intensity did not affect the concentrations of most nutrients in a nonmycorrhizal plant such as canola. Furthermore, cluster analysis showed that although the concentrations of K and Zn were related to tillage and Polymyxa and that of Mn was related to Gaeumannomyces–Phialophora complex, mycorrhizal structures were not closely related to any nutrients in the wheat tops. Based on the above, we conclude that the effect of reduced soil tillage on nutrient content in mycorrhizal plants may not be related to the activity of mycorrhizal fungi alone, especially in a crop such as wheat whose roots are heavily colonized by nonmycorrhizal structures. The situation could be different in maize, where roots were much less colonized by nonmycorrhizal fungi; there was a significant increase in the colonization by mycorrhizal fungi under reduced tillage (Fig. 1), and changes occurred in nutrient concentration in tops due to tillage intensity (Fig. 3 and 4).
Finally, although 83% of hyphae measured in soil were considered to belong to mycorrhizal fungi (Kabir et al., 1996), it should be noted that the fungi we frequently observed in roots, such as Polymyxa and Oplidium species, are nonfilamentous and thus would not be accounted for if only hyphae were considered as criteria for fungal activity in soil. Increased occurrence of Polymyxa in wheat roots under NT may be because the resting spores of this fungus produce zoospores when soils are very moist (Agrios, 1997) and that soils under NT often retain more moisture than those under CT (Fortin, 1993; Drury et al., 1999).
|
Conclusions
|
|---|
Reduced tillage intensity altered the colonization of roots of maize and wheat by mycorrhizal structures and those of maize, wheat, and canola by nonmycorrhizal fungi. It also changed the concentration of several nutrients in the leaves of maize and wheat but none in the leaves of canola. It is suggested that not only the mycorrhizal fungus colonization but also the concomitant colonization of roots by nonmycorrhizal fungi needs to be taken into account in studies on the effects of tillage intensity on the nutrient concentration in plant tops.SAS Institute 1985
|
ACKNOWLEDGMENTS
|
|---|
The authors gratefully acknowledge the valuable assistance of Ms.Theres Rösch in this study.
Received for publication June 15, 1999.
|
REFERENCES
|
|---|
- Agrios G.N. Plant pathology, 4th ed San Diego, CA: Academic Press, 1997.
- Anken, T., J. Heuser, P. Weisskopf, A. Mozafar, and W. Sturny. 1997. Bodenbearbeitungssysteme, Dirktsaat stellt höchste Anforderungen. Rep. 501. Swiss Federal Res. Stn. for Agric. Economics and Engineering, Tänikon, Switzerland.
- Beare M.H., Hu S., Coleman D.C., Hendrix P.F. Influence of mycelial fungi on soil aggregation and agronomic matter storage in conventional and no-tillage soils. Appl. Soil Ecol. 1997;5:211-219.
- Brennan R.F. The role of manganese and nitrogen nutrition in the susceptibility of wheat plants to take-all in Western Australia. Fert. Res. 1992;31:35-41.
- Carter P.R., Barnett K.H. Corn-hybrid performance under conventional and no-tillage systems after thinning. Agron. J. 1987;79:919-926.[Abstract/Free Full Text]
- Cox W.J., Zobel R.W., van Es H.M., Otis D.J. Tillage effects on some soil physical and corn physiological characteristics. Agron. J. 1990;82:806-812.[Abstract/Free Full Text]
- Deng S.P., Tabatabai M.A. Effect of tillage and residue management on enzyme activities in soils phosphatases and arylsulfatase. Biol. Fert. Soil 1997;24:141-146.
- Dirks B., Scheffer F. Der Kohlensaüre-Bikarbonatauszug und der Wasserauszug als Grundlage zur Ermittlung der Phosphorsaürebedurftigkeit der Böden. Landwirtsch. Jahrb. 1930;71:73-99.
- Douds D.D., Jr., Galvez L., Janke R.R., Wagoner P. Effect of tillage and farming system upon populations and distribution of vesicular–arbuscular mycorrhizal fungi. Agric. Ecosyst. Environ. 1995;52:111-118.
- Drury C.F., Tan C.S., Welacky T.W., Oloya T.O., Hamill A.S., Weaver S.E. Red clover and tillage influence on soil temperature, water content, and corn emergence. Agron. J. 1999;91:101-108.[Abstract/Free Full Text]
- Fairchild M.H., Miller G.L. Vesicular–arbuscular mycorrhizas and the soil-disturbance-induced reduction of nutrient absorption in maize. New Phytol. 1990;114:641-650.
- Fortin M.C. Soil temperature, soil water, and no-till corn development following in-row residue removal. Agron. J. 1993;85:571-576.[Abstract/Free Full Text]
- Frey S.D., Elliott E.T., Paustian K. Bacterial and fungal abundance and biomass in conventional and no-tillage agroecosystems along two climatic gradients. Soil Biol. Biochem. 1999;31:573-585.
- Gavito M.E., Miller M.H. Changes in mycorrhiza development in maize induced by crop management practices. Plant Soil 1998;198:185-192.
- Graham R.D., Rovira A.D. A role of manganese in the resistance of wheat plants to take-all. Plant Soil 1984;78:441-444.
- Hornby D., Fitt B.D.L. Effects of root-infecting fungi on structure and function of cereal roots. In: Ayers P.G., ed. Effects of disease on the physiology of the plant growth. Cambridge: Cambridge Univ. Press, 1981:101-130.
- Johnson N.C., Copeland P.J., Crookston R.K., Pfleger F.L. Mycorrhizae: Possible explanation for yield decline with continuous corn and soybean. Agron. J. 1992;84:387-390.[Abstract/Free Full Text]
- Kabir Z., O'Halloran I.P., Fyles J.W., Hamel C. Seasonal changes of arbuscular mycorrhizal fungi as affected by tillage practices and fertilization: Hyphal density and mycorrhizal root colonization. Plant Soil 1997;192:285-293.
- Kabir Z., O'Haaoran I.P., Hamel C. The proliferation of fungal hyphae in soils supporting mycorrhizal and non-mycorrhizal plants. Mycorrhiza 1996;6:477-480.
- Khalil S., Loynachan T.E., McNabb H.S., Jr. Colonization of soybean by mycorrhizal fungi and spore populations in Iowa soils. Agron. J. 1992;84:832-836.[Abstract/Free Full Text]
- Kim K.Y., Jordan D., McDonald G.A. Effect of phosphate-solubilizing bacteria and vesicular–arbuscular mycorrhizae on tomato growth and soil microbial activity. Biol. Fert. Soils 1998;26:79-87.
- Kurle J.E., Pfleger F.L. Management influences on arbuscular mycorrhizal fungal species composition in a corn–soybean rotation. Agron. J. 1996;88:155-161.[Abstract/Free Full Text]
- Matowo P.T., Pierzynski G.M., Whitney D., Lamond R.E. Soil chemical properties as influenced by tillage and nitrogen source, placement, and rates after 10 years of continuous sorghum. Soil Tillage Res. 1999;50:11-19.
- McGonigle T.P., Miller M.H. Mycorrhizae, phosphorus absorption, and yield of maize in response to tillage. Soil Sci. Soc. Am. J. 1996;60:1856-1861.[Abstract/Free Full Text]
- McGonigle T.P., Miller M.H., Evans D.G., Fairchild G.L., Swan J.A. A new method which gives an objective measure of colonization of roots by vesicular–arbuscular mycorrhizal fungi. New Phytol. 1990;115:495-501.
- Miller M.H., McGonigle T.P., Addy H.D. Functional ecology of vesicular arbuscular mycorrhizas as influenced by phosphate fertilization and tillage in an agricultural ecosystem. Crit. Rev. Biotechnol. 1995;15:241-255.[Web of Science]
- Moreno F., Pelegrín F., Fernández J.E., Murillo J.M. Soil physical properties, water depletion and crop development under traditional and conservation tillage in southern Spain. Soil Tillage Res. 1997;41:25-42.
- Mulligan M.F., Smucker A.J.M., Safir G.F. Tillage modifications of dry edible bean root colonization by VAM fungi. Agron. J. 1985;77:140-144.[Abstract/Free Full Text]
- Phillips J.M., Hayman D.S. Improved procedures for clearing roots and staining parasitic and vesicular–arbuscular mycorrhizal fungi for rapid assessment of infection. Trans. Brit. Mycol. Soc. 1970;55:158-161.
- Prew R.D. The effect of minimum cultivation on the incidence of take-all down the root profile of winter wheat. Ann. Appl. Biol. 1981;98:217-226.
- Rengel Z. Decreased capacity of take-all fungus to oxidize manganous ions is associated with take-all decline. J. Plant Nutr. 1997;20:455-460.
- Rillig M.C., Allen M.F., Klironomos J.N., Field C.B. Arbuscular mycorrhizal percent root infection and infection intensity of Bromus hordeaceus grown in elevated atmospheric CO2. Mycologia 1998;90:199-205.
- SAS Institute. SAS/STAT guide for personal computer, 6th ed Cary, NC: SAS Inst, 1985.
- Schönbeck F., Dehne H.-W. The influence of endotrophic mycorrhiza on plant diseases: IV. Fungal parasites on aerial plant parts, Olpidium brassicae, TMV. J. Plant Dis. Protection 1979;86:103-112.
- Schulze D.G., McCay-Buis T., Sutton S.R., Huber D.M. Manganese oxidation states in Gaeumannomyces-infested wheat rhizospheres probed by micro-xanes specroscopy. Phytopathology 1995;85:990-994.[Web of Science]
- St. Arnaud M., Caron H.M., Fortin J.A. Inhibition of Phytium ultimum in roots and growth substrate of mycorrhizal Tagetes patula colonized with Glomus intraradices. Can. J. Plant Pathol. 1994;16:187-194.
- Sturz A.V., Carter M.R., Johnston H.W. A review of plant disease, pathogen interactions and microbial antagonism under conventional tillage in temperate humid agriculture. Soil Tillage Res. 1997;41:169-189.
- Tarkalson D.D., Jolley V.D., Robbins C.W., Terry R.E. Mycorrhizal colonization and nutrition of wheat and sweet corn grown in manure-treated and untreated topsoil and subsoil. J. Plant Nutr. 1998;21:1985-1999.[Web of Science]
- Wilhelm N.S., Graham R.D., Rovira A.D. Application of different sources of manganese sulfate decreases take-all (Gaeumannomyces graminis var. tritici) of wheat grown in a manganese deficient soil. Aust. J. Agric. Res. 1988;39:1-10.
- Yarham D.J. The effect on soil-borne diseases of changes in crop and soil management. In: Schippers B., Gams W., eds. Soil-borne plant pathogens. London: Academic Press, 1979:371-383.
This article has been cited by other articles:
|
|
|
|
 
C. S. Wortmann, J. A. Quincke, R. A. Drijber, M. Mamo, and T. Franti
Soil Microbial Community Change and Recovery after One-Time Tillage of Continuous No-Till
Agron. J.,
November 7, 2008;
100(6):
1681 - 1686.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Mazzoncini, C. Di Bene, A. Coli, D. Antichi, M. Petri, and E. Bonari
Rainfed Wheat and Soybean Productivity in a Long-Term Tillage Experiment in Central Italy
Agron. J.,
September 8, 2008;
100(5):
1418 - 1429.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. P. Garcia, C. S. Wortmann, M. Mamo, R. Drijber, and D. Tarkalson
One-Time Tillage of No-Till: Effects on Nutrients, Mycorrhizae, and Phosphorus Uptake
Agron. J.,
June 26, 2007;
99(4):
1093 - 1103.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Jansa, A. Wiemken, and E. Frossard
The effects of agricultural practices on arbuscular mycorrhizal fungi
Geological Society, London, Special Publications,
January 1, 2006;
266(1):
89 - 115.
[Abstract]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
