Comparative Performance of Geographical Isolates of Glomus mosseae in Field Crops under Low-Input Intensive P-Deficient Acid Alfisol

Comparative performance of five geographical isolates of Glomus mosseae screened from maize fields, soybean fields, vegetable fields, tea orchard, and citrus orchard was assessed in three major field crops (wheat, maize, and soybean) under low-input management in three glass-house pot experiments in a phosphorus (P)–deficient acid Alfisol. These geographical isolates of Glomus mosseae varied with respect to vesicular arbuscular mycorrhizal (VAM) spore count and root colonization in these crops with greatest spore count (240 per 250 g soil) and root colonization (28–34%) using previously screened local Glomus mosseae culture (VAM_L) of CSK Himachal Pradesh Agricultural University, Palampur, India, followed in order by VAM isolate from vegetable-based cropping system, Glomus mosseae isolate from soybean fields, and Glomus mosseae isolate from tea farm. Glomus mosseae isolate from vegetable-based cropping system remaining at par with local VAM culture (VAM_L), resulting in significantly greatest grain productivity in these field crops under low-input management. There was a considerable reduction in soil fertility with respect to NPK status over the control and initial status in pot soils inoculated with Glomus mosseae isolate from vegetable-based cropping system followed by local VAM strain (VAM_L), thereby indicating greater nutrient mobilization and productivity as well through this efficient Glomus mosseae strain in P-deficient acid Alfisol. In addition, Glomus mosseae isolates from different farming situations resulted in differential productivity and soil fertility under these field crops. Overall, Glomus mosseae isolate from vegetable-based cropping system proved its superiority in realizing greater productivity and nutrient mobilization compared to local Glomus mosseae VAM culture under low-input management in P-deficient acid Alfisol.     

Glycine–Glomus–Phosphate Solubilizing Bacteria Interactions Lead to Fertilizer Phosphorus Economy in Soybean in a Himalayan Acid Alfisol

Effects of Glycine–Glomus–phosphate solubilizing bacteria (PSB) interactions were studied on productivity, nutrient dynamics, and root colonization in soybean in a phosphorus (P)–deficient Himalayan acidic Alfisol in a greenhouse experiment. Treatments consisted of three vesicular arbuscular mycorrhizae (VAM) cultures, VAM_L [VAM culture, Glomus mosseae, developed by CSK Himachal Pradesh Agricultural University, Palampur, India], VAM_T [VAM culture, Glomus intraradices, developed by Centre for Mycorrhizal Research, The Energy and Resources Institute (TERI), New Delhi, India], and VAM_I [VAM culture, Glomus mosseae, developed by Indian Agricultural Research Institute (IARI), New Delhi, India], and a local PSB culture (Pseudomonas striata) alone or in combination with or without 75% of recommended phosphorus pentoxide (P₂O₅) dose based on targeted yield concept following the soil-test crop response (STCR) precision model. Sole application of PSB or either of the above VAM cultures considerably enhanced VA-mycorrhizal root colonization and root weight besides crop productivity and nutrient uptake over control. A similar stimulatory effect with significant enhancement on mycorrhizal root colonization and root weight was observed with coinoculation of PSB and VAM cultures over the control. Dual inoculation of VAM and PSB cultures also resulted in significant improvement in grain and straw yield besides grain protein content, thereby revealing a synergistic interaction between VAM and PSB. Coinoculation with either of VAM_T (Glomus intraradices) or VAM_I (Glomus mosseae) + PSB + 75% P₂O₅ dose remained at par with sole application of 100% P₂O₅ dose with respect to crop productivity, nutrient content, nutrient uptake, and soil fertility status besides the greatest root colonization and root weight at flowering, indicating that Glycine–Glomus–PSB interactions in combination with 75% P₂O₅ dose based on STCR precision model lead to economization of fertilizer P by about one-fourth without impairing crop productivity and soil fertility in soybean in a Himalayan acidic Alfisol.     

Effects of Vesicular Arbuscular Mycorrhizae and Applied Phosphorus through Targeted Yield Precision Model on Root Morphology,Productivity, and Nutrient Dynamics in Soybean in an Acid Alfisol

A field experiment was conducted in a phosphorus (P)–deficient acidic Alfisol in northwestern Himalayas to study the effect of three vesicular arbuscular mycorrhizae (VAM) cultures [VAM_L, local VAM culture (Glomus mosseae) developed by CSK Himachal Pradesh Agricultural University, Palampur, India; VAM_T, VAM culture (Glomus intraradices) developed by Centre for Mycorrhizal Research, The Energy and Resources Institute (TERI), New Delhi, India; and VAM_I, VAM culture (Glomus mosseae) developed by Indian Agricultural Research Institute (IARI), New Delhi, India] on growth, productivity, and nutrient dynamics in rainfed soybean. Plant height, aboveground dry matter, root dry matter, total dry matter, root length, root weight density, Rhizobium root nodule count, root colonization, yield attributes, yield, and nutrient uptake of soybean increased consistently and significantly with increase in inorganic P levels from 25 to 75% of recommended P₂O₅ dose based on targeted yield precision model coupled with various VAM cultures. VAM_T (Glomus intraradices) at each P level showed its superiority over VAM_I and VAM_L. Sole application of any of the three VAM cultures produced similar growth and development parameters as well as grain yield (18.68 to 19.08 q ha^?1) as produced through farmers’ practice (nitrogen at 20 kg ha^?1), indicating that VAM has a vital role in root morphology and nutrient dynamics in a soil–plant system, though significantly greater productivity was obtained with 100% of the recommended P₂O₅ dose based on soil-test crop response (STCR) precision model without VAM inoculation. Targeted grain yield of soybean (25 q ha^?1) was achievable with 75% of the recommended P₂O₅ dose applied with any of the three VAM fungi cultures without impairing soil fertility, thereby indicating that VAM fungi can save about 25% P fertilizer in soybean in P-deficient acidic Alfisols of northwestern Himalayas.     

Fertilizer Economy through Vesicular Arbuscular Mycorrhizae Fungi under Soil-Test Crop Response Targeted Yield Model in Maize–Wheat–Maize Crop Sequence in Himalayan Acid Alfisol

The effect of three vesicular arbuscular mycorrhizae (VAM) cultures with or without inorganic phosphorus (P) was studied in a maize–wheat–maize crop sequence in a P-deficient acidic Alfisol. Application of these three VAM cultures (Glomus mosseae, developed by CSK Himachal Pradesh Agricultural University, Palampur; Glomus intraradices, developed by the Energy and Resources Institute, New Delhi; and Glomus mosseae, developed by the Indian Agricultural Research Institute, New Delhi) alone or with 25% to 75% of recommended P₂O₅ dose based on soil-test crop response (STCR) precision model along with 100% of recommended nitrogen (N) and potassium (K) caused significantly greater grain and straw yield, NPK uptake, and soil nutrient buildup over the control and also increased crop yield and NPK uptake consistently and significantly with increases in applied P from 25% to 75% P₂O₅ dose. Results implied that application of either of the three VAM cultures with 75% P₂O₅ dose can economize the yield-targeted fertilizer P dose to the extent of about one fourth of the P requirement in maize–wheat–maize crop sequence without impairing yield targets and soil fertility in a P-deficient acidic alfisol.     

Improving Phosphorus Use through Co-inoculation of Vesicular Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria in Maize in an Acidic Alfisol

Performance of three vesicular arbuscular mycorrhizal (VAM) fungi cultures and a phosphate-solubilizing bacteria (PSB) culture alone or in combination with or without 75% of the recommended P₂O₅ dose based on soil-test crop response model was examined in maize in a phosphorus (P)-deficient acidic Alfisol in a glasshouse pot experiment. Sole application of VAM besides co-inoculation with PSB (Pseudomonas striata) and inorganic P stimulated mycorrhizal root colonization. Sole application of PSB, VAM_T (Glomus intraradices), and VAM_I (Glomus mosseae) as well as co-inoculation of VAM with PSB significantly improved crop productivity besides grain protein content, thus indicating a synergistic interaction between VAM and PSB. Application of VAM_T or VAM_I + PSB + 75% P₂O₅ remained at par with sole application of 100% P₂O₅ dose with regard to productivity, nutrient uptake, and soil fertility status (particularly P), thus indicating economization of fertilizer P to the tune of about 25% without compromising crop productivity and soil fertility in an acidic Alfisol.     

Influence of Vesicular Arbuscular Mycorrhizal Fungi and Applied Phosphorus on Root Colonization in Wheat and Plant Nutrient Dynamics in a Phosphorus-Deficient Acid Alfisol of Western Himalayas

Vesicular arbuscular mycorrhizal (VAM) fungi symbiosis confers benefits directly to the host plant's growth and yield through acquisition of phosphorus and other macro- and micronutrients, especially from phosphorus (P)–deficient acidic soils. The inoculation of three VAM cultures [viz., local culture (Glomus mosseae), VAM culture from Indian Agricultural Research Institute (IARI), New Delhi (Glomus mosseae), and a culture from the Centre for Mycorrhizal Research, Energy Research Institute (TERI), New Delhi (Glomus intraradices)] along with P fertilization in wheat in a P-deficient acidic alfisol improved the root colonization by 16–24% while grain and straw yields increased by 12.6–15.7% and 13.4–15.4%, respectively, over the control. Uptake of nitrogen (N), P, potassium (K), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) was also improved with VAM inoculation over control, but the magnitude of uptake was significantly greater only in the cases of P, Fe, Zn, and Cu. Inoculation of wheat with three VAM cultures in combination with increasing inorganic P application from 50% to 75% of the recommended P₂O₅ dose to wheat through the targeted yield concept following the soil-test crop response (STCR) precision model resulted in consistent and significant improvement in grain and straw yield, macronutrient (NPK) uptake, and micronutrient (Fe, Mn, Zn, Cu) uptake in wheat though root colonization did not improve at P₂O₅ doses beyond 50% of the recommended dose. The VAM cultures alone or in combination with increasing P levels from 50% to 75% P₂O₅ dose resulted in reduction of diethylenetriaminepentaacetic acid (DTPA)–extractable micronutrient (Fe, Mn, Zn, Cu) contents in P-deficient acidic soil over the control and initial fertility status, although micronutrient contents were relatively greater in VAM-supplied plots alone or in combination with 50% to 75% P₂O₅ dose over sole application of 100% P₂O₅ dose, thereby indicating the positive role of VAM in nutrient mobilization and nutrient dynamics in the soil–plant system. There was significant improvement in available N and P status in soil with VAM inoculation coupled with increasing P levels upto 75% P₂O₅ dose, although the greatest P buildup was obtained with sole application of 100% P₂O₅ dose. The TERI VAM culture (Glomus intraradices) showed its superiority over the other two cultures (Glomus mosseae) in terms of crop yield and nutrient uptake in wheat though the differences were nonsignificant among the VAM cultures alone or at each P level. Overall, it was inferred that use of VA-mycorrhizal fungi is beneficial under low soil P or in low input (nutrient)–intensive agroecosystems.     

Influence of Inorganic Phosphorus,VAM Fungi,and Irrigation Regimes on Crop Productivity and Phosphorus Transformations in Okra (Abelmoschus esculentus L.)–Pea (Pisum sativum L.) Cropping System in an Acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, India, during 2009–2011 to economize inorganic phosphorus (P) and water needs of an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through vesicular arbuscular mycorrhizal (VAM) fungi (Glomus mosseae) in a Himalayan acid Alfisol. The field experiment was replicated three times in a randomized block design comprising 14 treatments consisting of 12 treatment combinations of two VAM levels [0 and 12 kg ha^?1], three phosphorus levels [50, 75, and 100% of recommended soil-test-based nitrogen (N)–P–potassium (K)], and two irrigation regimes [40 and 80% of available water-holding capacity of field soil (AWC)], in addition to one treatment with “generalized recommended NPK dose with generalized recommended irrigations (GRD)” and one treatment based on “farmers’ practice of plant nutrition and irrigation management in the region.” This article presents crop productivity and P dynamics studies during the second crop cycle of okra–pea sequence (2010–2011) and statuses of different P fractions in the soil after the second pea crop harvest during 2010–2011. Crop productivity and P uptake data in okra–pea sequence indicated that application of VAM + 75% P dose at either of two irrigation regimes did not differ significantly than GRD treatment and VAM + 100% P dose. It suggests an economy of about 25% inorganic P dose through VAM fungi. The treatments imbedded with VAM inoculation enhanced the P uptake in okra–pea system, on an average by 21% over the GRD and non-VAM-inoculated counterparts. Further, integrated application of P, VAM, and irrigation regimes evaluated in okra–pea sequence for 2 years led to greater status of water-soluble P (21%), sodium bicarbonate (NaHCO₃)–inorganic phosphorus (Pi) (11%), sodium hydroxide (NaOH)–Pi (9%), hydrochloric acid (HCl)–extractable–P (20%) over non-VAM-inoculated counterparts and low status of organic P (NaHCO₃-P_o and NaOH-P_o), all of which appreciably contributed to available P supply to plants in the present study in an acid Alfisol. The correlation coefficient reveals that contribution of inorganic P forms is highly correlated to crop productivity and total P uptake in okra and pea crops besides soil available P in the present study. Overall, it is concluded that VAM inoculation in okra–pea cropping system significantly enhanced the P availability to plants by way of enriching the labile-P pool such as water-soluble P and P loosely bound to aluminium (Al-P) and iron (Fe-P) on adsorption complexes and by P mineralization from organic matter in an Himalayan acid Alfisol.     

Effect of Vesicular Arbuscular–Mycorrhizal Fungi and Phosphorus Application through Soil-Test Crop Response Precision Model on Crop Productivity,Nutrient Dynamics,and Soil Fertility in Soybean–Wheat–Soybean Crop Sequence in an Acidic Alfisol

A field experiment was conducted in a phosphorus (P)–deficient acidic alfisol of the northwestern Himalayas using three vesicular arbuscular mycorrhizal (VAM) cultures: a local culture developed by CSK Himachal Pradesh Agricultural University, Palampur (Glomus mosseae), VAM culture from Indian Agricultural Research Institute (IARI), New Delhi (Glomus mosseae), and a culture from the Centre for Mycorrhizal Research, The Energy Research Institute (TERI), New Delhi (Glomus intraradices). These were applied alone or in combination with 25 to 75% of recommended P₂O₅ and recommended nitrogen (N) and potassium (K) based on soil-test crop response (STCR) precision model with an absolute control, farmers’ practice, and 100% of recommended P₂O₅ dose based on the STCR model. The results revealed that sole application of either of the three VAM cultures have produced 2.68 to 9.81% and 25.06 to 28.62% greater grain yield than the control in soybean and wheat crops, respectively. Besides greater straw yield, NPK uptake as well as soil nutrient buildup increased. Increase in P fertilization from 25 to 75% of recommended P₂O₅ dose coupled with VAM inoculation with either of the three VAM cultures resulted in consistent and significant improvement in crop productivity (grain and straw yields), NPK uptake, and improved soil nutrient status, though significantly greatest magnitude was obtained with sole application of 100% of the recommended P₂O₅ dose. The targeted grain yields of soybean (25 q ha^?1) and wheat (30 q ha^?1) were achievable with 75% of recommended P₂O₅ dose along with mycorrhizal biofertilizers, thereby indicating that application of efficient VAM fungi with 75% of recommended P₂O₅ dose can economize the STCR precision model fertilizer P dose by about 25% without impairing crop yield targets or soil fertility in a soybean-based cropping system in an acidic alfisol.     

The effect of vesicular-arbuscular mycorrhizal inoculation on nutrient uptake and yield of alley-cropped cassava in a degraded Alfisol of southwestern Nigeria

Leaf and root (tuber) nutrient uptake patterns of cassava (Manihot esculenta Crantz) alley-cropped with gliricidia (Gliricidia sepium), leucaena (Leucaena leucocephala), and senna [(Senna (syn. Cassia) siamea] as influenced by vesicular-arbuscular mycorrhizal (VAM) inoculation in a degraded Alfisol were investigated in consecutive years. The cassava plants were mulched with fresh prunings of each hedgerow tree species at 2-month intervals in the second and third years of alley cropping. While VAM inoculation significantly influenced the root uptake of nutrients, the leaf uptake was not affected except for the uptake of P. In most cases, there was no difference in the nutrient concentration between inoculated and uninoculated plants, either in the leaf or in the root, indicating that the productivity of cassava was regulated by the amount of nutrients the roots could absorb. In spite of similar total soil N in all inoculated and uninoculated alley-cropped cassava plots and similar exchange-able soil K contents in inoculated and uninoculated alley-cropped cassava plots with leucaena and senna, greater uptake of N, P, and K and greater concentrations of K were observed in roots of inoculated alley-cropped cassava with gliricidia and leucaena than with senna. These results indicated that greater mineralization and availability of nutrients to cassava roots from prunings of nodulating gliricidia and leucaena than from non-nodulating senna may be important, particularly with efficient VAM inoculation, in these alley-cropping systems. Also, for similar nutrients in the inoculated and uninoculated cassava soils alley-cropped with each hedgerow species, VAM inoculation significantly enhanced cassava root dry weights, indicating that an effective VAM fungus can be an agent of greater nutrient uptake in a competitive environment.     

Influence of AM fungi,inorganic phosphorus and irrigation regimes on plant water relations and soil physical properties in okra (Abelmoschus esculentus L.) – pea (Pisum sativum L.) cropping system in Himalayan acid alfisol

Present investigation studied plant water relations and soil physical properties through AM fungi (Glomus mosseae) to mitigate drought stress in Himalayan acid Alfisol having low water retentivity. Experimentation was carried out at Palampur, India during 2009–2011 in okra–pea cropping system in randomized block design (RBD) replicated thrice with 14 treatments comprising arbuscular mycorrhizal (AM) fungi, varying phosphorus nutrition and irrigation regimes at 40 and 80% available water holding capacity. Integrated use of AM fungi at varying phosphorus (P) levels and irrigation regimes led to significantly higher relative leaf water content (3% each) in okra and pea besides significantly higher xylem water potential (27%) in pea over non-AM fungi counterparts. AM fungi enhanced water-use-efficiency in okra (5–17%) and pea (12–35%) over non–AM fungi counterparts. AM fungi also improved water holding capacity (5–6%) and mean weight diameter of soil particles (4–9%) over non–AM fungi counterparts; but, had nominal or no effect on bulk density. Mycorrhizal plants maintained higher tissue water content imparting greater drought resistance to plants over non–mycorrhizal plants at moisture stress. It is inferred that integrated application of AM fungi and P at varying irrigation regimes improved the plant water relations vis-à-vis drought resistance, crop productivity, WUE, soil aggregation and water holding capacity in okra–pea sequence in Himalayan acid Alfisol.     

Effects of excess aluminum on mineral uptake in mycorrhizal sorghum

Soil acidity is often associated with toxic aluminum (Al), and mineral uptake usually decreases in plants grown with excess Al. This study was conducted to evaluate the effects of Al (0, 35, 70, and 105 μM) on Al, phsophorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn,) and copper (Cu) uptake in shoots and roots of sorghum [Sorghum bicolor (L.) Moench, cv. SC283] colonized with the vesicular‐arbuscular mycorrhizal (VAM) fungi isolates Glomus intraradices UT143–2 (UT143) and Glomus etunicatum UT316A‐2 (UT316) and grown in sand (pH 4.8). Mycorrhizal (+VAM) plants had higher shoot and root dry matter (DM) than nonmycorrhizal (‐VAM) plants. The VAM treatment had significant effects on shoot concentrations of P, K, Ca, Fe, Mn, and Zn; shoot contents of P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu; root concentrations of P, S, K, Ca, Mn, Zn, and Cu; and root contents of Al, P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu. The VAM effects on nutrient concentrations and contents and DM generally followed the sequence of UT316 > UT143 > ‐VAM. The VAM isolate UT143 particularly enhanced Zn uptake, and both VAM isolates enhanced uptake of P and Cu in shoots and roots, and various other nutrients in shoots or roots.     

AM fungi lead to fertilizer phosphorus economy and enhanced system productivity and profitability in okra (Abelmoschus esculentus L.)–pea (Pisum sativum L.) cropping system in Himalayan acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, Himachal Pradesh, India, during 2009–2011 to economize inorganic phosphorus (P) and enhance profitability of okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through arbuscular mycorrhizal fungi (AMF). A field experiment was replicated thrice in a randomized block design comprising 14 treatments involving AMF (Glomus mosseae) at varying inorganic P (50%, 75%, and 100% of recommended soil test-based P dose) and irrigation regimes (40% and 80% available water capacity] in a Himalayan acid Alfisol. In okra, AMF inoculation at varying P and irrigation regimes registered higher P response ratio (PRR), net returns (10–18%), and benefit:cost (B:C) ratio (17–49%) compared to “generalized recommended P dose (GRD)” and their non-AMF counterparts. Similarly in pea, AMF inoculation at varying P and irrigation regimes again registered higher PRR, net returns (14–23%), and B:C ratio (10–58%) compared to GRD and non-AMF counterparts. Higher system productivity (7–16%) and profitability in terms of net returns (9–23%) and B:C ratio (10–54%) were also registered in AMF-imbedded treatments compared to non-AMF counterparts. Further, “AMF + 75% soil test-based P dose” at either of these irrigation regimes registered statistically similar okra–pea system productivity and profitability as that obtained under “100% soil test-based P dose” at either of two irrigation regimes, thus indicating an economy of soil test-based applied P dose by about 25%. Overall, the current study suggests that practice of AMF inoculation has great potential in enhancing system productivity and profitability besides cutting down about 25% inorganic P requirement in okra–pea production system in the Himalayan acid Alfisol.     

Interactive effects of co-inoculation of Bradyrhizobium japonicum strains and mycorrhiza species on soybean growth and nutrient contents in plant

The main objective of this study was to investigate the effects of co-inoculation with different strains of Bradyrhizobium japonicum (i.e. Helinitro, Rizoking, and Nitragin) and arbuscular mycorrhizal fungi (AMF) species (i.e. Glomus fasciculatum, Glomus versiforme, Glomus intraradices, Glomus mosseae, and Glomus etunicatum) on soybean growth, fungal root colonization, and nutrient uptake of nitrogen (N), phosphorus (P), zinc (Zn), iron (Fe), and copper (Cu). Co-inoculation with various AMF species and rhizobia significantly (p<0.01) increased the soybean biomass production as compared to the non-inoculated controls. Furthermore, AMF colonization of roots of soybean plants increased by 79, 70.1, 67, 63, 57.5, and 50.1% in the presence of G. fasciculatum (GF), G. versiforme (GV), G. intraradices (GI), G. mosseae (GM), and G. etunicatum (GE), and Gmix (a mixed culture of fungi), respectively. Higher nutrient contents were observed in plants co-inoculated with Helinitro and GF. More insight into these results will enable optimization of the effective use of AM fungi in combination with their bacterial partners as a tool for increasing soybean yields in Iran; however, its general analytical framework could be applied to other parts of the world.     

The relationship between vesicular-arbuscular mycorrhiza and lime: Associated effects on the growth and nutrition of brachiaria grass (Brachiaria decumbens)

Summary We studied the effects of limining on growth and nutrient concentrations of Brachiaria decumbens inoculated with five vesicular-arbuscular mycorrhizal (VAM) fungal assemblages which orginated from soils with different acidity. Liming increased plant growth when applied at rates up to 3 g kg^-1 soil and depressed growth at higher rates. Mycorrhizal plants grew better than non-mycorrhizal ones in unlimed soil and also liming rates of 4.5 and 6.0 g kg^-1 soil. The growth amelioration effects of VAM in highly acid or over-limed soils were related to nutrient uptake. VAM fungi isolated from an acidic soil exhibited a high symbiotic effectiveness and were better adapted to unlimed soil than those that originated from non-acidic soils. VAM root colonization, 90 days after planting, was little affected by liming. Fungal spore production and species compositions were highly affected by liming. A mixture of Glomus diaphanum and Glomus occultum predominated in unlimed soils inoculated with VAM assemblages isolated from non-acidic soils. In these fungal assemblages, an increased liming rate favored Glomus etunicatum over the other VAM fungi. Gigaspora margarita sporulated abundantly when introduced into unlimed soils, but rarely in limed soils. VAM appear to be crucial for the establishment of brachiaria pastures in the nutrient-deficient acidic soils of Central Brazil. It is suggested that liming may cause striking shifts in VAM populations which may, in turn, have a long-term impact on agricultural productivity in the tropics.     

Effects of excess manganese on mineral uptake in mycorrhizal sorghum

Associations between vesicular‐arbuscular mycorrhizal (VAM) fungi and manganese (Mn) nutrition/toxicity are not clear. This study was conducted to determine the effects of excess levels of Mn on mineral nutrient uptake in shoots and roots of mycorrhizal (+VAM) and non‐mycorrhizal (‐VAM) sorghum [Sorghum bicolor (L) Moench, cv. NB9040]. Plants colonized with and without two VAM isolates [Glomus intraradices UT143–2 (UT1 43) and Gl. etunicatum UT316A‐2 (UT316)] were grown in sand irrigated with nutrient solution at pH 4.8 containing 0, 270, 540, and 1080 μM of added Mn (as manganese chloride) above the basal solution (18 μM). Shoot and root dry matter followed the sequence of UT316 > UT143 > ‐VAM, and shoots had greater differences than roots. Shoot and root concentrations and contents of Mn, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and copper (Cu were determined. The +VAM plants generally had higher mineral nutrient concentrations and contents than ‐VAM plants, although ‐VAM plants had higher concentrations and contents of some minerals than +VAM plants at some Mn levels. Plants colonized with UT143 had higher concentrations of shoot P, Ca, Zn, and Cu and higher root Mg, Zn, and Cu than UT316 colonized plants, while UT316 colonized plants had higher shoot and root K concentrations than UT143 colonized plants. These results showed that VAM isolates differ in enhancement of mineral nutrient uptake by sorghum.     

Effects of mes [2(n‐morpholino)‐ethanesulfonic acid] and ph on mineral nutrient uptake by mycor‐rhizal and nonmycorrhizal maize

Mycorrhizal (+VAM) and nonmycorrhizal (‐VAM) maize (Zea mays L.) plants were grown in sand culture in a greenhouse to determine effects of MES [2(N‐morpholino)‐ethanesulfonic acid] (2.0 mM) and pH (4.0, 5.0, 6.0, and 7.0) on mineral nutrient uptake. Plants were inoculated with the vesicular‐arbuscular mycorrhizal (VAM) isolate Glomus intraradices UT143. Shoot and root dry matter yields were lower in plants grown with MES (+MES) than without MES (‐MES), and decreased as pH increased. Shoot concentrations of N, Ca, Mg, Mn, and Zn were generally higher in +MES than in ‐MES plants, and nutrient contents of most nutrients were generally higher in + MES than in ‐MES plants. Concentrations of N, Ca, Mg, and Mn increased and P, S, and Fe decreased, while contents of all measured nutrients except Mn and Zn decreased as pH increased. Concentrations of Mn, Fe, Zn, and Cu were higher in +VAM than in ‐VAM plants, and contents of P and Ca were higher in ‐VAM than in +VAM plants and Zn content was higher in +VAM than in ‐VAM plants. MES had marked effects on mineral nutrient uptake which should be considered when MES is used to control pH of nutrient solutions for growth of maize.     

Growth Behavior,Nutrient Harvest Index,and Soil Fertility in Okra-Pea Cropping System as Influenced by AM Fungi,Applied Phosphorus,and Irrigation Regimes in Himalayan Acidic Alfisol

The impact of arbuscular mycorrhizal fungi (AMF), inorganic phosphorus (P), and irrigation regimes was studied in an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system in an acidic Alfisol. Experimentation was carried out at Palampur, India, in a randomized bock design (RBD), replicated three times with fourteen treatments comprising AM fungi (Glomus mosseae), inorganic phosphorus (50, 75, and 100% soil-test-based recommended P dose), irrigation regimes (at 40 and 80% available water capacity), generalized recommended NPK and irrigations (GRD), and farmers’ practice. Effects of AM fungi on plant height, leaf area index (LAI), and dry-matter accumulation (DMA) were nominal at early crop growth stage, i.e., 50 DAS (days after sowing). However, at 100 DAS, AMF imbedded treatments led to higher plant height (4%), LAI (3%), and DMA (6%) in okra, whereas in pea the magnitude of increase in these parameters following AMF inoculation was 6, 5, and 8%, respectively, over non-AMF counterparts. AMF + 75% soil-test-based P dose at either of these irrigation regimes gave statistically similar yields in both okra and pea as that obtained under 100% soil-test-based P dose at either of two irrigation regimes, thus indicating an economy of about 25% in soil-test-based P dose. Regarding nutrient harvest index in okra and pea, statistically similar values were registered with most nutrients under both AMF inoculated and non-AMF counterparts. In the case of okra, P harvest index was registered less by 3% with AMF inoculation; however, its magnitude increased by 3% in pea following AMF inoculation compared to non-AMF counterparts at similar levels of P and irrigation. At completion of two cycles of okra-pea system, AMF imbedded treatments did not alter available soil nutrient status significantly in comparison to non-AMF counterparts. Overall, current study suggests that practice of AMF inoculation has great potential in enhancing growth parameters for better productivity, fertilizer-P economy, and nutrient harvest efficiency in okra-pea production system in Himalayan acidic Alfisol.     

EXPLOITATION OF PHOSPHORUS PATCHES WITH DIFFERENT PHOSPHORUS ENRICHMENT BY THREE ARBUSCULAR MYCORRHIZAL FUNGI

The effect of three arbuscular mycorrhizal (AM) fungi on phosphorus (P) nutrient activation and acquisition by maize from spatially heterogeneous sand was investigated using dual-mesh packages enriched with different P concentrations and compared with non-mycorrhizal cotrols. As would be expected the AM fungi significantly enhanced leaf photosynthetic rate and the biomass and P concentrations in shoots and roots. All three fungi (Glomus intraradices, Glomus mosseae and Glomus etunicatum) displayed the capacity to dissolve inorganic P and promoted P nutrient availability in the packages (P patches). G. etunicatum showed the largest effect comparing with Glomus intraradices and Glomus mosseae, particularly in packages with high concentrations of P. Possible mechanisms involved include the acidification of the P patches by the AM fungi, promotion of the dissolution of the P, and more marked effects of the three fungal isolates with increasing enrichment of P in the patches. Inoculation with G. etunicatum resulted in greater acidification compared to the other two fungi. We conclude that AM fungi can promote P availability by acidifying the soil and consequently exploiting the P in nutrient patches and by facilitating the growth and development of the host plants.     

Inoculation withGlomus mosseae improves N2 fixation by field-grown soybeans

Summary A field study carried out in a sandy, relatively acid Senegalese soil with a low soluble P content (7 ppm) and low vesicular-arbuscular mycorrhizal (VAM) populations showed that soybean responded toGlomus mosseae inoculation when the soluble P level in the soil had been raised by the addition of 22 kg P ha^–1. In P-fertilized plots, N₂ fixation of soybean, assessed by the A value method, was 109 kg N₂ fixed hat when plants were inoculated withRhizobium alone and it reached 139 kg N₂ fixed ha^–1 when plants were dually inoculated withRhizobium andGlomus mosseae using an alginate bead inoculum. In addition to this N₂ fixation increase (+28%),Glomus mosseae inoculation significantly improved grain yield (+13%) and total N content of grains (+16%). This success was attributed mainly to the low infection potential of the native VAM populations in the experimental site. In treatments without solubleP or with rock phosphate, no effect of VAM inoculation was observed.     

大豆/玉米间作体系中接种AM真菌和根瘤菌对氮素吸收的促进作用

利用大豆和玉米之间根系不同分隔方式的盆栽试验,研究了在玉米/大豆间作体系中接种大豆根瘤菌、AM真菌Glomus mosseae和双接种对间作体系氮素吸收的促进作用。结果表明,双接种处理显著提高了大豆及与其间作玉米的生物量、氮含量,双接种大豆/玉米间作体系总吸氮量比单接AM菌根、根瘤菌和不接种对照平均分别增加22.6%、24.0%和54.9%。大豆促进了与其间作玉米对氮素的吸收作用,在接种AM真菌和双接种条件,间作玉米的AM真菌侵染率提高,大豆根瘤数增加; 接种AM真菌处理,不分隔和尼龙网分隔比完全分隔玉米吸氮量的净增加量是未接种对照的1.8、2.6倍,双接种处理分别是对照的1.3和1.7倍。说明在间作体系中进行有效的根瘤菌和AM真菌接种,发挥两者的协同作用对提高间作体系土壤养分利用效率,进一步提高间作体系的生产力有重要的意义。