Studies on antagonism betweenFusarium udum Butler and root region microflora of pigeon-pea

Antagonism betweenFusarium udum Butler causing wilt of pigeon-pea (Cajanus cajan (L.) Millsp.) and the saprophytic microflora of the root region of the host was studied with reference to colony interaction, hyphal interference, volatile and non-volatile metabolites and staling growth products. Studies were extended to screen potential antagonists against the wilt pathogen in soil. Aspergillus flavus, A. niger, A. terreus, Penicillium citrinum andMicromonospora globosa (an actinomycete) were antagonistic againstF. udum, whereas the pathogen parasitized and killedAspergillus luchuensis, Cunninghamella echinulata, Curvularia lunata, Mortierella subtilissima andSyncephalastrum racemosum. The pattern of growth of microorganisms on nutrient agar staled by rhizosphere soil inocula of healthy or wilted pigeon-pea plants was found to be different.F. udum colonized and grew on nutrient agar staled by the rhizosphere inoculum of the wilted plants upto 120h of incubation. However, it could not colonise and grow on the nutrient agar staled by rhizosphere microflora of healthy plants after 48h of incubation because of the presence of antagonists likeA. niger, A. flavus, A. terreus and a few species ofPenicillium in the soil inoculum. When pure cultures in soil ofF. udum was mixed with those of antagonists in different ratios,A. niger, A. flavus andM. globosa significantly suppressed the population ofF. udum, whereasA. terreus markedly reduced the population. When inoculated in soil, the antagonists exhibited a high fungistatic activity againstF. udum.     

Tolerance to higher temperature byAspergillus nidulans and its possible implication in biological control of wilt disease of pigeon-pea

Summary During the course of studies on the ecology ofFusarium udum Butler, the incitant of wilt disease of pigeon-pea (Cajanus cajan (L.) Millsp.),Aspergillus nidulans was found to tolerate higher temperatures of summer, and other species includingF. udum were suppressed in field soil. The population ofA. nidulans increased in the soil incubated at 40±2°C at pH6 and 7 while the population ofF. udum was highly suppressed. The wilt disease of pigeon-pea was significantly suppressed at 38±2°C in the soil having a mixture of the inocula ofF. udum andA. nidulans whereas at lower temperature (25±2°C) no significant impact ofA. nidulans on the disease was found. On the basis of this study an integrated use of higher temperature, alkaline pH andA. nidulans has been suggested for biological control of wilt disease of pigeon-pea.     

FUNGISTASIS IN SOILS

1. Fungistasis in soil is a widespread phenomenon affecting most fungal propagules, though some are insensitive. In most instances, it is coexistent with the presence of living microorganisms, and is annulled by energy-yielding nutrients. Fungistasis with characteristics similar to that in soil may also occur on leaves of plants. 2. Germination and growth of bacteria and actinomycetes is also restricted in soils. The characteristics of their inhibition appear to be the same as those for fungi. Therefore, the concept of a widespread microbial inhibition in soil can be applied to all three groups of microorganisms. 3. Fungistasis can be detected by various direct methods, or indirectly by methods involving the use of porous or permeable carriers. It may be expressed as a restriction on the final amount of germination (the usual parameter), germination rate (with time), and rate of germ-tube or hyphal growth. Since the expression of fungistasis is often complete in soil, titration with nutrients may be required to distinguish between the sensitivities of different fungi. 4. Fungistasis generally is expressed most strongly at soil moisture contents somewhat less than saturation. Its expression usually is maximal in neutral or slightly alkaline soils. In acidic conditions fungistasis may be lessened because of suppression of bacterial and actinomycete activity. Increased sensitivity of some fungi in soils of pH > 7.0 may be caused by a directly unfavourable effect of pH on the fungus. 5. Fungal species with small spores tend to be highly sensitive to fungistasis. These spores tend to germinate slowly and to require exogenous nutrients for germination. By contrast, species with larger spores and sclerotia often do not require exogenous nutrients for germination. The larger spores tend to germinate rapidly and to exhibit low sensitivity, as compared with small spores. A few nutrient-independent spores are insensitive to fungistasis. At least a part of the difference in sensitivity is related to germination time; spores which germinate slowly compete poorly with the soil micro-flora for their nutrients. 6. Fungistasis is often temporarily annulled by enriching the soil with energy-yielding nutrients. Usually, complex materials such as plant residues are most effective. A few weeks after such treatment, the level of fungistasis may, however, be increased. Annulment of fungistasis by compounds not utilized as energy sources has not yet been demonstrated. 7. Several soils naturally suppressive to Fusarium wilt diseases were more fungistatic to Fusarium than soils conducive to wilt. Potential means by which fungistasis may be manipulated to control root-infecting fungi are (a) through stimulation of germination with nutrients, thus exposing the germ tube to lysis, and (b) by increasing the fungistatic level of soil through appropriate amendments. 8. Volatile substances identified in soils, some of which are potentially inhibitory to fungi include (a) ammonia, which apparently is evolved from ammonium salts in some arid soils of high pH, (b) ethylene, which has been identified in some soils of pH < 7.0 (though high levels of this gas seem to be tolerated by most fungi), (c) allyl alcohol, and (d) other unidentified substances. Non-volatile inhibitors include high molecular weight substances revealed by molecular sieve chromatography of soil extracts. Microbial metabolites such as those present in staled fungal cultures also have been proposed to account for fungistasis. In a few soils fungistasis persists after sterilization because of the presence of inhibitory concentrations of calcium carbonate, iron or aluminium. Inherent in the proposition that inhibitory substances provide the primary mechanism of fungistasis is the concept of a highly complex phenomenon, involving various highly specific inhibitory and counteracting stimulatory substances, with the outcome for the fungus depending on the kinds and relative amounts of each present. 9. By the nutrient-deficiency hypothesis, the level of available nutrients in soil is insufficient to support germination of nutrient-dependent propagules, except in nutrient-rich microsites. Inhibition of nutrient-independent propagules is explained by loss of endogenous nutrients required for germination, through microbial nutrient competition. Evidence for this hypothesis is (a) the imposition of fungistasis on numerous nutrient-independent propagules during incubation on leaching model systems designed to simulate microbial nutrient competition in soil, (b) similar losses of endogenous nutrients occurring on soil and the leaching system, and (c) the fact that soils are chronically deficient in energy in relation to the microbial populations present, with the consequence that enforced inactivity is imposed upon most of the population at any given time for this reason alone, regardless of the presence or absence of fungistatic substances. Journal series article no. 7747 from the Michigan Agricultural Experiment Station.     

THE EFFECT OF ASSOCIATED SOIL MICROFLORA ON FUSARIUM UDUM BUTL., THE FUNGUS CAUSING WILT OF PIGEON-PEA (CAJANUS CAJAN (L.) MILLSP.)

Inoculation with Fusarium udum Butl. produced more wilt of pigeon-pea in sterilized than in unsterilized soils at the same pH. From unsterilized soils with low disease incidence, nine fungi, Bacillus subtilis and an Actinomyces were isolated. The number of isolations of a particular organism varied from month to month during the cropping season of pigeon-pea in Delhi. Interaction of Fusarium udum and other organisms isolated was studied. Aspergillus niger and A. terreus secreted inhibitory substances in potato-dextrose broth: Bacillus subtilis inhibited growth on solid medium and also produced a toxic substance in potato-dextrose broth. The nature of the medium employed and period of growth were important factors in the production of the inhibitory principle, which is thermostable. The low incidence of pigeon-pea wilt in unsterilized soils may result from the inhibitory activity of the associated microflora in the soil.     

固相微萃取-气质法测定土壤挥发性抑菌物质

运用固相微萃取．气相色谱,质谱法(SPME-GC／MS),测定了参与土壤抑真菌作用的土壤挥发性成分和土壤细菌挥发性代谢物。通过比较土壤来源和土壤细菌来源的挥发性抑菌成分,发现在强挥发性抑菌土壤和土壤细菌代谢物中普遍存在着三甲胺、二甲基二硫醚、3-甲基-2-戊酮、甲基吡嗪、2,5-二甲基吡嗪、N,N-二甲基辛胺、十九烷等化合物。这些化合物很有可能就是参与土壤抑菌作用,特别是挥发性物质抑菌作用的主要成分。另外,为深入了解土壤中参与抑菌作用的挥发性化合物提供了简便有效的方法。     

Soil fungistasis: elevation of the exogenous carbon and nitrogen requirements for spore germination by fungistatic volatiles in soils.

Axenic, washed conidia of Fusarium solani f. sp. phaseoli, Aspergillus flavus, and Verticillium albo-atrum were placed on washed Difco purified agar discs along with an inorganic salt solution containing various levels of carbon and nitrogen substrates. These discs were exposed to volatiles from six soils (pH 5.1-8.6). Fusarium solani macroconidial germination was inhibited mostly by volatiles from soils of pH 5.1, 6.1, 7.0, and 7.5, but high levels of glucose and NH4Cl reversed this inhibition, raising germination to that of no-soil, no-carbon or nitrogen controls. Conidial germination of A. flavus was inhibited mainly by volatiles from high pH (7.0, 7.8, and 8.6) soils, and increased levels of glucose plus an amino acid mixture nullified this inhibition. Volatiles from soils of pH 5.1, 6.1, and 7.5 stimulated A. flavus conidial germination. Assays after the removal of CO2 from the air above soil of pH 5.1 demonstrated that volatiles inhibitory to A. flavus were produced by this soil. Assays indicated that a KOH-soluble compound was a fungistatic soil volatile to F. solani macroconidial germination. The nullification by carbon and nitrogen substrates of F. solani and A. flavus inhibition caused by soil volatiles parallels that for soil fungistasis. Conidial germination of V. albo-atrum was markedly stimulated by volatiles in all soils tested, and was not affected by removal of CO2. Inhibitory soil volatiles may increase the nutritional requirements for spore germination of certain fungi.     

Rhizosphere microflora ofCajanus cajan in relation to Fusarium wilt resistance

Summary Studies were made to find out the factors responsible for resistance inCajanus cajan (L.) Millsp. variety C-11-6 against wilt caused byFusarium udum Butl. It was thought to be either due to associated antagonistic microflora in the rhizosphere or due to biochemical constituents in the plant itself. Screening of the rhizosphere isolates revealed the absence of any potent antagonists againstF. udum suggesting that the resistance in C-11-6 variety is not due to antagonistic organisms in the rhizosphere.     

Ecology of soil fungi of a sal forest with emphasis on fungistasis

Summary An ecological study of the soil micro-fungi in three forest regions of different age was undertaken. The pH of the soil varied from 6.6 to 6.9. Soil samples were collected from three different depthsviz 0–6, 7–12, and 13–18 inches with aseptic precautions and were studied by a dilution-plate method using peptone-dextrose agar with rose bengal for the fungal analysis. Determinations were made of physico-chemical characters of soil such as organic matter, total nitrogen, phosphorus, water-holding capacity and pH of the soil. The organic matter and nitrogen favoured the growth of fungi in the soil. The upper horizon contained more of the organic matter, nitrogen, phosphorus, and perhaps other elements, which in turn favoured the growth of fungi in soil. The number of fungi decreased according to increase in depth of the soil samples. The frequency and abundance of some dominant fungi have been calculated and the fungal population has been represented both qualitatively and quantitatively. The pattern of colonization of nutrient agar by fungi from soil inocula changed with the increase of concentration of staling products produced by earlier established fungal colonies. At the highest concentration of staling the fungi colonizing the agar disks were species ofTrichoderma, Aspergillus, Penicillium, Curvularia, Alternaria andFusarium. The capacity of species to colonize the staled nutrient medium was due partly to tolerance of the metabolic products diffused in agar disks and partly to density of the population in the inoculated soil. The comparative account of germinated spores on unsterilized and sterilized soil and in controlled condition shows that fungistatic activity is higher in unsterilized soil. In Table 4 the F₃, an oldest soil sample has more fungistatic activity than F₁ and F₂, due to more litter deposition on the floor, which increases the population of micro-organisms and fungistatic activity.     

Studies on soil fungistasis: Effect of certain physical and biological factors

Summary The effect of different physical and biological factors like soil sterilization, incubation period of soil, spore age, amendment of certain fungal species and their metabolites on soil fungistasis has been investigated.Different degree of sterilization affected the fugistasis differently. Soil heating above 80°C completely annulled the fungistasis. No fungistasis was recorded in soil samples steamed for 15 mts in an autoclave.Incubation of soil samples to longer duration resulted in increased fungistasis. Maximum fungistatic value was noted in samples incubated for 15 days at 25±1°C.Spore age also played important role in fungistasis. A positive relation was noted in the spore age and fungistasis upto 30 days of age and thereafter the increase in fungistasis was not well marked.Varying inhibitory effect was noted on the spore germination of the test fungi in relation to amendment of certain fungi individually and in different combinations to the soil.Aspergillus flavus alone and in combination ofAspergillus niger proved most inhibitory. The filtrate of the different fungi also induced fungistasis in soil. In this case alsoA. flavus was most effective.     

Mycoparasitism ofFusarium SPP. onRhizoctonia solani Kühn

Summary Experiments on nutrient and staled agar were carried out to investigate the mycoparasitic activity of some fusaria againstRhizoctonia solani Kühn. Penetration and coiling byFusarium oxysporum Sch.,F. semitectum Berk & Rav. andF. udum Butler in and around theR. solani hyphae was observed. Lysis ofF. udum hyphae was observed inside theR. solani hyphae showing the reverse of the normal direction of necrotrophic mycoparasitic relationships. The mycoparasitic activity ofFusarium spp. was much affected in staled agar plates.     

Factors affecting the occurrence and distribution of entomopathogenic fungi in natural and cultivated soils

Factors affecting the occurrence and distribution of entomopathogenic fungi in 244 soil samples collected from natural and cultivated areas in Spain were studied using an integrated approach based on univariate and multivariate analyses. Entomopathogenic fungi were isolated from 175 of the 244 (71.7 %) soil samples, with only two species found, Beauveria bassiana and Metarhizium anisopliae. Of the 244 soil samples, 104 yielded B. bassiana (42.6 %), 18 yielded M. anisopliae (7.3 %), and 53 soil samples (21.7 %) harboured both fungi. Log-linear models indicated no significant effect of habitat on the occurrence of B. bassiana, but a strong association between M. anisopliae and soils from cultivated habitats, particularly field crops. Also, irrespective of habitat type, B. bassiana predominated over M. anisopliae in soils with a higher clay content, higher pH, and lower organic matter content. Logistic regression analyses showed that pH and clay content were predictive variables for the occurrence of B. bassiana, whereas organic matter content was the predictive variable for M. anisopliae. Also, latitude and longitude predicted the occurrence of these same species, but in opposite directions. Altitude was found to be predictive for the occurrence of B. bassiana. Using principal component analysis, four factors (1 to 4) accounted for 86 % of the total variance; 32.8, 22.9, 19.6 and 10.4 % of the cumulative variance explained, respectively. Factor 1 was associated with high positive weights for soil clay and silt content and high negative weights for soil sand content. Factor 2 was associated with high positive weights for soil organic matter content and high negative weights for soil pH. Factor 3 was associated with high positive weights for latitude and longitude of the sampled localities and factor 4, had high positive weights only for the altitude. Bi-plot displays representing soil samples were developed for different factor combinations and indicated that, irrespective of geographical location, absence of both fungal species was determined by alkaline sandy soils with low organic matter content, whereas heaviness of soil texture, acidity and increasing organic matter content led to progressively higher percentages of samples harbouring entomopathogenic fungi. These results could aid decision-making as to whether or not a particular cultivated or natural soil is suitable for using entomopathogenic fungi as a pest control measure and for selecting the fungal species best suited to a particular soil.     

Selenium uptake by plants as a function of soil type,organic matter content and pH

In pots containing sandy soils at two levels (pH 5 and 7) to which 0.5 mg Se L^-1 soil had been added, an increase in the proportion of clay soil or peat soil led to a decrease in the uptake of Se by spring wheat grain (Triticum aestivum L., var. Drabant) and winter rape plants (Brassica napus L., var. Emil). The effect was most pronounced for the smallest additions of clay and peat soils. Differences in Se uptake between the two pH levels were greatest in treatments where the additions of clay and peat soils were small. At the high pH, an increase in clay content from 7% to 39% resulted in a decrease in Se uptake of 79% for wheat and 70% for rape. At the low pH, the uptake decreased by 72% and 77%, respectively. At the higher pH, an increase in the content of organic matter from 1.4% to 39% resulted in decreases in Se uptake of 88% for wheat grain and 69% for rape. At the low pH, Se uptake decreased by 63% and 48%, respectively. Adding peat soil to clay soil had little effect on Se uptake. Among the limed, unmixed clay, sand and peat soils to which Se had not been added, uptake was highest from the sandy soil, i.e. 8.3 ng Se/g wheat grain and 42 ng Se/g rape. The lowest uptake rates were obtained in the clay soil, i.e. 3.0 ng Se/g for wheat grain and 9.0 ng Se/g for rape.     

Soil fungistasis: role of the microbial nutrient sink and of fungistatic substances in two soils.

Sensitivity of conidia of Cochliobolus victoriae to fungistasis decreased markedly following incubation on moist sand for at least 1 h. Germination was greater on Conover loam or on sand being leached with water than on an alkaline clay loam soil known to produce a volatile fungistatic substance. Evolution of 14CO2 began within 3 min after [14C]glucose was applied to the soils; the rate of 14CO2 evolution was faster with Conover loam. Germination of Thielaviopsis basicola conidia per unit of glucose remaining in agar discs initially containing 0-1% glucose, was lower for discs incubated on the clay loam soil than on Conover loam, and was greatest on a bed of sand undergoing aqueous leaching. Germination of ascospores of Neurospora tetrasperma and conidia of C. victoriae was suppressed on discs of washed, Purified Agar or polyacrylamide gel incubated on or over the clay loam soil, but no suppression resulted when discs were incubated on Conover loam. Extensive aeration of either soil did not remove its fungistatic effect. Fungistasis in Conover loam appears to be caused primarily by nutrient deprivation, whereas volatile fungistatic substances may play a major role in the clay loam soil.     

Effectiveness of Hirsutella minnesotensis and H. rhossiliensis in control of the soybean cyst nematode in four soils with various pH,texture, and organic matter

The parasitism of soybean cyst nematode, Heterodera glycines, by the fungi Hirsutella rhossiliensis and Hirsutella minnesotensis and their biocontrol effectiveness against the nematode were investigated in four soils with various pH, texture, and organic matter. Fungal parasitism was assayed in the soils in 25 mL vials. As expected, percentage of H. glycines second-stage juveniles (J2) parasitized by either fungus increased with increasing number of fungus-colonized J2 initially added into the soils. Parasitism of J2 by the fungi was negatively related with soil pH. Both positive and negative relationships with fungal parasitism were observed for soil sandiness and organic matter. In greenhouse study, both fungi at 0.2–0.8 g fresh mycelium of liquid culture per 0.3 L pot and 1% corn-grits culture effectively reduced nematode population density. The relationship between biocontrol effectiveness and the soil factors depended on fungal species and inoculation levels. In general, percentage reduction of egg population density in the soil was negatively correlated with soil pH and positively correlated with sandiness. There was no or weak correlation between egg reduction and organic matter. The percentage of J2 parasitized by the fungi 2 months after planting did not correlate with the soil factors. Plant growth was better in the two soils with intermediate pH and sand than the soil with high pH and low sand or with low pH and high sand. It appeared that soil pH and/or texture are important in influencing biocontrol effectiveness, but further studies are needed to determine the effect of individual factors because they are correlated.     

Effect of cultival practices and soil treatments on incidence of wilt disease of pigeon pea

Summary The incidence of wilt disease of pigeon pea (Cajanus cajan (L.) Millsp.) caused byFusarium udum under soil treatments with various substances was studied under field conditions. The disease incidence was highly suppressed under mixed cropping withCrotalaria medicaginea. Phygon XL was found to be the most effective fungicide to reduce the incidence of the disease. The incidence of wilt disease also decreased in case of soil amended with the leaves ofC. medicaginea. Wilt incidence increased in the soil amended with the roots of pigeon pea.     

STUDIES ON THE EFFECT OF ASSOCIATED SOIL MICROFLORA ON FUSARIUM UDUM BUTL., THE FUNGUS CAUSING WILT OF PIGEON-PEA (CAJANUS CAJAN (L.) MILLSP.), WITH SPECIAL REFERENCE TO ITS PATHOGENICITY

The interaction of certain soil saprophytes and Fusarium udum , the wilt organism of pigeon-pea, with special reference to their effect on pathogenicity, has been studied. The filtrates of Aspergillus niger, Rhizopus nigricans and mixed filtrates of all the saprophytes inhibited the growth of Fusarium udum on solid medium. This inhibition of F. udum has been shown to be due to unfavourable reaction of the medium rather than to food exhaustion or the presence of toxic substances. The culture filtrates after passage through soil beds failed to affect adversely the growth of F. udum because of the change in pH. Inoculation experiments have indicated that only Rhizopus nigricans is effective in reducing the incidence of wilt because of its faster rate of growth. The mixed inocula of the organisms and mixed filtrates of all the saprophytes have also been observed to be effective in reducing wilt incidence. Aspergillus terreus appears to enhance the virulence of Fusarium udum.     

Interrelationship betweenCoprinus lagopus andFusarium udum in soil in relation to competitive saprophytic ability and microbial antagonism

Summary The interrelationship between the growth ofCoprinus lagopus andFusarium udum on pigeon pea substrates in soil was studied at 22-2°C and 30±2°C in relation to their competitive saprophytic ability and antagonism.C. lagopus was observed to be a potent and frequent colonizer of pigeon pea substrates in soil along withF. udum. Saprophytic colonization of pigeon pea substrate byF. udum precolonized byC. lagopus was inhibited in all inoculum soil mixtures. Saprophytic colonization of the substrate byF. udum was better at 22°C than at 30°C and that byC. lagopus better at 30°C than at 22°C. The colonization of substrate by each fungus was suppressed by the other fungus depending upon the temperature used. Hyphal parasitism and colony interactions between these fungi and also with a number of other saprophytic fungi were investigated. No antagonistic reaction was observed betweenF. udum andC. lagopus. However, these fungi were observed to be potent antagonists against other microfungi tested. The formation of fruiting bodies ofC. lagopus was also observed in the laboratory on nutrient media but more frequently on pigeon pea substrates.     

Microbial Community Composition Affects Soil Fungistasis

Most soils inhibit fungal germination and growth to a certain extent, a phenomenon known as soil fungistasis. Previous observations have implicated microorganisms as the causal agents of fungistasis, with their action mediated either by available carbon limitation (nutrient deprivation hypothesis) or production of antifungal compounds (antibiosis hypothesis). To obtain evidence for either of these hypotheses, we measured soil respiration and microbial numbers (as indicators of nutrient stress) and bacterial community composition (as an indicator of potential differences in the composition of antifungal components) during the development of fungistasis. This was done for two fungistatic dune soils in which fungistasis was initially fully or partly relieved by partial sterilization treatment or nutrient addition. Fungistasis development was measured as restriction of the ability of the fungi Chaetomium globosum, Fusarium culmorum, Fusarium oxysporum, and Trichoderma harzianum to colonize soils. Fungistasis did not always reappear after soil treatments despite intense competition for carbon, suggesting that microbial community composition is important in the development of fungistasis. Both microbial community analysis and in vitro antagonism tests indicated that the presence of pseudomonads might be essential for the development of fungistasis. Overall, the results lend support to the antibiosis hypothesis.     

Effect of certain chemicals on soil fungistasis

Summary Fungistatic property of soil sample amended with certain chemicals has been studied. The fungistatic property was found to be highest in soil samples amended with potassium permanganate and copper sulphate. The remaining chemicals also caused different levels of fungistasis. Thus presence of various chemicals in the microbial products seems to be the possible cause of soil fungistasis.     

The effect of level of CaCO3, inoculation and lime pelleting on the nodulation and growth of beans in five acid soils

Summary The effect of level of CaCO₃, inoculation and lime pelleting on the nodulation, dry matter yield and % N content of common bean plants (Phaseolus vulgaris) grown in five acid soils was investigated in a greenhouse study. The soils represented a range in pH from 3.9 to 5.1, in exchangeable Al from 0.0 to 4 meq/100 gm, in exchangeable Mn from 0.35 to 2.32 me/100 gm, and in %C from 0.69 to 5.60.Nodule weight decreased with increasing %C and for the soil with highest %C (5.60) no nodules were observed. In soils with low organic matter and low exchangeable Al and Mn, inoculation increased nodule weight, dry matter yield and %N especially at the lowest pH level. Where the seeds were not inoculated, nodule weight and dry matter yield increased with soil pH. No such increases were observed where the seeds were inoculated. There was no apparent advantage in lime pelleting in such soils.In soils with low organic matter content and with substantial amounts of Al and/or Mn, liming increased nodule weight and dry matter yield, and decreased exchangeable Al and/or Mn. Lime pelleting was superior to mere inoculation in increasing nodule weight particularly at low lime rates.In soils with relatively high organic matter content, nodulation was very low or none at all. Low lime rates had little effect on exchangeable Al and Ca and dry matter yield. Higher lime rates, however, decreased exchangeable Al and dry matter yield but increased exchangeable Ca.