接种根瘤菌对白格、大叶合欢和银合欢生长与结瘤的影响

Effects of inoculation of Rhizobium suspension on nodulation and plant growth were examined with Albizzia procera,Albizzia lebbeck and Leucaena leucocephala seedlings grown on sterilized and non-sterilized soil media.Inoculation resulted in nodule number increases of 28.6,29.02and 23.9 times in sterilized soil and 3.4,3.6and 3.27 times in non-sterilized soil for A.procera,A.lebbeck and L.leucocephala seedlings respectively.Total dry mass increased by 127.6%,66.7%and 60.7% in sterilized soil and 100%,95.5%and 52.65% in non-sterilized soil for these three legume trees,respectively,after a period of two months.Significantly high inoculation responses of oot length,root diameter,collar diameter,shoot length,and dry mass of root,shoot,leaves and nodules were also observed in both steilized and non-sterilized soil media as compared to respective control treatments,The response to inoculation was strong in sterilized and modest in non-sterilized soils.The significantly higher response to Rhizobium inoculation over control in all the species tested suggested that application of Rhizobium greatly enhanced plant growth ,nodulation,biomass production and nitrogen-fixing activity of the nodules.     

Mycorrhiza and soil fertility effects with growth,nodulation and nitrogen fixation of leucaena grown on a typic eutrustox

Abstract

The rapidly growing, woody perennial legume, Leucaena (Leucaena leucocephala (Lam.) de Wit), is adaptable to a wide range of neotropical soil conditions. Effective Rhizobium inoculation and endophyte mycorrhizal colonization are essential for high levels of production and symbiotic N₂ fixation. The objective of this study was to determine growth, nodulation, nitrogenase activity and nodule composition of inoculated Leucaena as affected by mycorrhizal colonization and factorial soil fertility treatments of a Typic Eutrustox. Highly significant increases in top growth, nodule fresh wt. and nitrogenase activity resulted with Glomus fasciculatum colonization, soil K and linear increases with low‐soluble P fertilization to 300 mg P kg^‐1 soil. Highly significant interactions for increased nodulation and nitrogenase activity resulted with K × mycorrhiza. Interactions of all three factors P, K and mycorrhiza were highly significant for nodule fresh wt. However, responses comparing inoculation with G. fasciculatum and with combined G. fasciculatum, G. microcarpus and G. clavium were not significant. Highly significant increases with applied K levels to 300 mg K kg^‐1 soil resulted with top and root growth, nodulation and nitrogenase when applied with soluble P at 100 mg kg^‐1 soil and 500 mg Ca kg^‐1 soil. Significant and highly significant interactions of P, Ca and K level resulted for all parameters. Plant nutrient element composition of nodules increased with the fertilization treatments for P, Ca and increased K levels. A highly significant inverse relation was apparent with decreased Na resulting with increased K levels. Half or more of total nodule K, P and Mg but less than 20% of Ca and Na were within the nodule cytosol. Sodium, Mg, P, and Ca decreased in the cytosol fraction with increased K content.     

Influence of pruning frequency of Albizia lebbeck, Gliricidia sepium and Leucaena leucocephala on nodulation and potential nitrogen fixation

The influence of four pruning frequencies on biomass, nodulation and N₂ fixation was investigated on Albizia lebbeck, Gliricidia sepium and Leucaena leucocephala grown in the screenhouse for 16 months, using acetylene reduction and ¹⁵N dilution methods. Frequent prunings at 4-month intervals had no deleterious effect on symbiotic N₂ fixation, which increased in Gliricidia and Leucaena in particular. Nodulation and nitrogenase activity varied inconsistently within species, and were not influenced by pruning frequency. Cumulative assessment of pruning effect showed higher biomass, N yield and N₂-fixing capacity of the woody species than at last harvest, and appeared to have more practical relevance. Across species, cumulative total dry matter, N yields, and both percentage and absolute amount of N₂ derived from atmosphere increased with pruning frequency, except when trees were pruned 3 times. Of the three species, G. sepium had the lowest biomass production, N₂ fixation and N accumulation. Received: 25 October 1995     

Effect of fertilizers, lime, and inoculation with rhizobia and mycorrhizal fungi on the growth of four leguminous tree species in a low-fertility soil

The aim of this study was to evaluate the effects of lime, fertilizers, mycorrhizal fungi, and selected rhizobia strains on the growth of four woody legume species, Albizia lebbeck (L.) Benth., Enterolobium contortisiliquum (Vell.) Morong., Leucaena leucocephala (Lam.) de Wit, and Sesbania virgata (Cav.) Pers. in a low-fertility soil. The experiment was conducted under greenhouse condition in plastic pots (4 kg). Eight treatments and eight replicates per treatment were performed in a completely randomized design. The treatments were: (1) complete treatment (C) (NPK fertilization?+?micronutrients?+?liming?+?MR that is inoculation with mycorrhizal fungi and rhizobia); (2) C minus N (C???N that is as C without the addition of N); (3) C???N???M (as C???N without inoculation with arbuscular mycorrhizal fungi (AMF)); (4) C???N??R (as C???N without inoculation of rhizobia); (5) C???N???liming (as C???N without liming); (6) C???N???micro (as C???N without addition of micronutrients); (7) C???N???P (as C???N without addition of P); (8) control without fertilization, liming, and without inoculation with AMF and rhizobia. After 4 months of growth, we determined the yield of individual plants, nodulation, mycorrhizal colonization, and nutrient contents. Phosphorus was the most limiting nutrient for plant growth, followed by nitrogen. L. leucocephala and S. virgata had the most robust response to the addition of micronutrients and liming, showing an increase in nutrient content, plant height, and root and shoot dry matter. When compared to the single inoculation, the dual inoculation increased growth of all plants, except that of A. lebbeck, which did not respond to either rhizobia or mycorrhizal fungi inoculation.     

Identification and characterization of salt- and thermo-tolerant Leucaena-nodulating Rhizobium strains

 Rhizobium-legume symbioses are important for their nitrogen input, but salinity and elevated temperature in arid and semi-arid areas limit their effectiveness, and therefore plant growth and productivity. Sixteen Rhizobium strains isolated from root nodules of Leucaena trees grown in different geographical areas of Egypt varied in their degree of tolerance to salinity and in their symbiotic effectiveness with Leucaena leucocephala under saline conditions. Three strains were tolerant to >3% NaCl. L. leucocephala grown in the greenhouse at concentrations of NaCl up to 1.0% and inoculated either with strain DS 78 or strain DS 158 displayed significantly better growth than those plants grown at the same levels of salinity and inoculated with reference strain TAL 583. Although nine of the Rhizobium strains grew at 42  °C, their mean generation times were lengthened two- to fourfold. When daylight growth temperatures were elevated from 30  °C to 42  °C, nodule number and mass, nitrogenase activities and shoot top dry weight of plants inoculated with strains DS 78, DS 157 and DS 158 significantly increased, whereas these parameters decreased in plants inoculated with strain TAL 583. Rhizobium strains that effectively nodulate Leucaena under adverse saline conditions and at high temperatures were thus isolated, identified and characterized. Received: 12 September 1997     

Pruning effect on nitrogen nutrient release in the root zone of Albizia lebbeck and Leucaena leucocephala

The effect of pruning on the dynamics of N release in the root zone of Albizia lebbeck and Leucaena leucocephala was studied using potted soil and minilysimeters with presterilized sand-medium supplied with N-free nutrient solution. Plants were pruned twice at 11 and 13 months and leachates were collected weekly for 16 weeks starting from first pruning, and analysed for mineral N content. Removal of plant shoots reduced nodule and root biomass by some 30–38% and halved nodule N yields, while total N yields did not differ between pruned and unpruned plants. The dynamics of N nutrient in the rhizosphere was also affected by pruning, irrespective of the growth medium. In soil culture, unpruned plants of both species maintained greater levels of total N in their rhizosphere compared to those that were pruned. In sand culture, nitrate-N was by 66–84% the predominant N form in soil leachate across the two sequential prunings. Over the 16 weeks following these prunings of A. lebbeck and L. leucocephala, cumulative mineral N in both forms was significantly higher in the root zone of unpruned plants, and was consistently greater under rhizobial inoculation. Less mineral N was released into the root zone of each species during the period after the second pruning than after the first one. L. leucocephala released significantly more N than A. lebbeck over the sampling period, but net N release beneath both species was lower than 1%, indicating that tree legumes do not release sizeable proportions of their N into root zone, and that pruning reduces their N release still further. Received: 27 September 1996     

Effects of Rhizobium and vesicular-arbuscular mycorrhiza inoculations on nodulation,symbiotic nitrogen fixation and soybean yield in subtropical-tropical fields

Summary Field experiments were carried out to determine the effects of single and mixed inoculations with Rhizobium and vesicular-arbuscular mycorrhiza (VAM) on nodulation, symbiotic N₂ fixation and yield of soybeans in six Taiwan subtropical-tropical sites. Inoculation with Rhizobium alone significantly increased nodulation, nodule weight and nitrogenase activity of nodules in three out of six experimental fields, and affected soybean yields in the range –13% to + 134%. Inoculation with VAM fungi alone did not have a significant effect on nodulation and nitrogenase activity. Mycorrhiza inoculation affected soybean yields in the range –13% to + 65%, but only the yield increases at one out of six sites with N application were statistically significant. Mixed inoculation with Rhizobium and mycorrhiza affected yields in the range –8% to + 145% A synergistic effect from mixed inoculation of Rhizobium-mycorrhiza on soybean yields was found in one out of six experimental fields. The yield response to N application (40 kg N ha^–1) in these six paddy-field trials was not significant. These results suggest that single or mixed inoculation of rhizobia can greatly assist soybean grain yields and can replace N fertilizers.     

Acid soil tolerance of leucaena species in greenhouse trials

Abstract

Lines of Leucaena leucocephala (Lam.) de Wit were grown in greenhouse pots of an acid, Al‐toxic Tatum subsoil (clayey, mixed, thermic typic Hapludult) treated with 0 or 3000 ppm CaCO₃ to give final soil pH values of 4.1 and 5.3, respectively. Lines of L. leucocephala, plus those of other Leucaena species, were also tested on an acid, Monmouth soil (clayey, mixed, mesic, typic Hapludult) treated with 0 or 1500 ppm CaCO₃ to give final soil pH values of 4.8 and 6.6, respectively. The major index of acid soil tolerance used was relative root yield (unlimed/limed %).

Relative root yields of 117 L. leucocephala lines on Tatum soil ranged from 34 to 246%. Hence, liming the soil from pH 4.1 to 5.3 was highly beneficial to some lines and highly detrimental to others. Because Tatum subsoil is 89% Al saturated at pH 4.1, line tolerance to unlimed soil indicates tolerance to Al. Causes of yield depression at pH 5.3 were not determined.

On Monmouth soil, in a test involving 148 lines of 6 Leucaena species, relative root yields (unlimed/limed %) ranged from 23 to 386%. The line showing highest tolerance to the acid soil (P.I. 279578) and that showing lowest tolerance (P.I? 281636) are both L,. leucocephala. The majority of lines used on Monmouth soil (124 of a total of 148) were from this species. Average performances of the 6 species indicated that L. diversifolia Benth. (5 lines) was most tolerant to the acid Monmouth soil and liming the soil from pH 4.8 to 6.6 actually decreased root yields. The species L.. leucocephala (124 entries) and L. pulverulenta Benth. (4 lines) were intermediate, and L. lanceolata S. Wats. (3 lines) and I., retusa Benth. (1 line) appeared more sensitive to acid Monmouth soil. The Al saturation of Monmouth soil at pH 4.8 was only 23% (compared with 89% for Tatum at pH 4.1). The major growth limiting factor in acid Monmouth soil is believed to be Al toxicity, but this soil has not been as throughly characterized as has Tatum, and other factors may well be involved in explaining differential tolerances of Leucaena lines on the unlimed versus limed soil.

Results of these studies indicate that Leucaena species and lines within species differ significantly in tolerance to acid soils having high levels of exchangeable Al. Acid soil tolerant lines of Leucaena may be useful in expanding the acreage of this crop on oxisols and ultisols of the tropics and subtropics.     

Early nitrogen fixation and utilization in albizia lebbeck,leucaena leucocephala,and gliricidia sepium using nitrogen (15n) labelling

Abstract

High nitrogen (N₂)‐fixing potential is a desirable characteristic for any candidate hedgerow tree. Thus a study was conducted to evaluate Albizia lebbeck as a N₂‐fixing tree in comparison to Gliricidia sepium and Leucaena leucocephala currently used in alley cropping. Nitrogen fixation and utilization were assessed in a screenhouse at four months after planting by the ¹⁵N dilution technique using Senna siamea as the non N₂‐fixing reference. A. lebbeck accumulated significantly more N than L. leucocephala, but G. sepium was intermediate. This superiority in N yield was mainly due to its abundant nodule dry weight production which accounted for up to 10.8% of its total N. This was equivalent to 2.5 and 6 fold that of Gliricidia and Leucaena nodules, respectively. A. lebbeck had bigger but significantly (P<0.05) lower number of nodules per plant than G. sepium, but it did not differ from Leucaena. Albizia was the best N₂ fixer with 44% Ndfa equivalent to 533 mg N per plant. G. sepium followed with 28% Ndfa and L. leucocephala with 18% Ndfa corresponding to 321 and 191 mg N fixed, respectively. However, the relatively higher N₂ fixation in Albizia was not translated into higher N or dry matter yields. As A. lebbeck fixed more N, it depended less on soil N (49.8%) than did Leucaena (72.5% Ndfs) and Gliricidia (63.9% Ndfs) and less on fertilizer N as well. Thus A. lebbeck appears to be a potential hedgerow species for alley cropping purpose.     

Relative importance of Ca,N, and P in enhancing mycorrhizal activity in leucaena leucocephala grown in an oxisol subjected to simulated erosion

Pot experiments were conducted in the greenhouse to determine the combined effects of lime, nitrogen and phosphorus and the relative importance of each of these nutrients in establishing nodulated and mycorrhizal Leucaena leucocephala (Lam.) de Wit Var. K8 in an oxisol subjected to simulated erosion. Leucaena was grown in the soil inoculated or not with the vesicular‐arbuscular mycorrhizal fungus Glomus aggregatum Schenck and Smith emend Koske, with or without a basal nutrient (basal) consisting of K, Mg, S, Zn, Cu, and B plus lime, N, and P (complete) or one of the latter three supplements.

The extent of mycorrhizal colonization of roots as well as mycorrhizal effectiveness, as measured by pinnule P content increased when the eroded soil was amended with combinations of all the nutrients and inoculated with G. aggregatum. Similar trends were observed when symbiotic effectiveness was measured in terms of shoot P, Cu, and Zn status and dry matter yield. Nodule dry matter was also responsive to amendment of the soil with the complete nutrients and to vesicular‐arbuscular mycorrhizal inoculation. Phosphorus was found to be the most important nutrient limiting mycorrhizal effectiveness in the eroded soil, followed by N and lime. It is concluded that lost nutrients, particularly P, need to be replaced before legumes can be established successfully on highly weathered eroded soils inoculated with vesicular‐arbuscular mycorrhizal fungi.     

Foliar application of molybdenum in common beans. I. Nitrogenase and reductase activities in a soil of high fertility

Although common bean (Phaseolus vulgaris L.) has a good potential for N₂ fixation, poor nodulation following inoculation, principally under field conditions, has led to increased nitrogen (N) fertilizer use in this crop. In the face of the negative environmental effects of N fertilizer, alternative methods have been studied to minimize the amount to be applied. In this sense, foliar application of molybdenum (Mo) has been cited as a promising method. Several papers show that high bean yields (1,500–2,500 kg ha^‐1), may be obtained in the southeasten region of Brazil, when there is an application of N as side dressing or Mo spray 25 days after plant emergence. A field experiment was carried out to verify the effect of Mo foliar application on nitrogenase and nitrate reductase activities and on bean yield. Treatments included Rhizobium inoculation (with and without), foliar application of Mo (0 and 40 g ha^‐1), N at planting (0 and 20 kg ha^‐1) and N applied as side dressing (0 and 30 kg ha^‐1). Molybdenum and N as side dressing were used 25 days after plant emergence. Molybdenum increased greatly the nitrogenase activity and extended the period of high nitrate reductase activity, with a consequent increase in total shoot N. Increase of nitrogenase activity did not depend on inoculation, showing that soil native rhizobia may increase in effectiveness when appropriately handled. Bean yield did not differ significantly when fertilized with either Mo or N as side dressing.     

Leucaena leucocephala seedling response to vesicular-arbuscular mycorrhizal inoculation in soils with varying levels of inherent mycorrhizal effectiveness

Summary The symbiotic effectiveness of vesicular-arbuscular mycorrhizal (VAM) fungi present in widely differring tropical soils was evaluated in a greenhouse experiment. Small volumes of field soil, a standard inoculum (Glomus aggregatum) or both were introduced into a fumigated sand-soil medium amended with nutrients for optimum VAM activity. Leucaena leucocephala (Lam.) de Wit var. K8 was grown in the medium as an indicator plant. VAM effectiveness was monitored as a function of time by determining the P status of pinnules. The soils differed from each other with respect to the time their endophytes required for the expression of initial and maximum effectiveness and in the level of maximum effectiveness they exhibited. The effect of mycorrhizal inoculation, calculated as the ratio of the areas enclosed by the effectiveness curve of G. aggregatum to that enclosed by the effectiveness curves of test soils, was found to be a good indicator of the response of L. leucocephala to inoculation of soils with G. aggregatum Hawaii Institute of Tropical Agriculture and Human Resources Journal series No. 3285     

Influence of inorganic N on mycorrhizal activity,nodulation, and growth ofLeucaena leucocephalain an oxisol subjected to simulated erosion

Abstract

The influence of inorganic N on the development of mycorrhizal symbiosis inLeucaena leucocephala(Lam.) de Wit was studied in an Oxisol subjected to simulated erosion. The plants were grown in pots containing soil samples inoculated with the VAM fungusGlomus aqgregatumand amended with 0, 25, 50 or 100 ppm N. The extent of VAM colonization of roots increased with increasing levels of N in both eroded and uneroded soils. However, the level of infection was significantly higher in the eroded soil than in the uneroded one. Mycorrhizal activity monitored in terms of P content of leucaena subleaflets increased significantly in the eroded soil when it was amended with 25 ppm N and became similar to that observed in the uneroded soil. Nodule dry matter production and shoot N concentration increased significantly with N application upto 50 ppm. Above this level of N, nodule dry weight declined while N concentration did not change. Application of 25 ppm N to the eroded soil also significantly increased shoot and root dry weights while no change was observed in the uneroded soil. A further increase in N level did not improve yield. The results illustraste the potential benefits of starter N in the establishment of mycorrhizal and nodulatedLeucaena leucocephalain eroded soils     

Mycorrhizal etiology of favorable proteoid rhizogenesis,nodulation, and nitrogenase of lupines

Lupine (Lupinus albus L.) has been cultivated as a food‐grain legume for more than 3,000 years. Persistent productivity occurs on low fertility soils within regions of drought and unfavorable temperature extremes. Distinctive rhizosphere characteristics of Proteaceae genera include development of determinate rootlet clusters termed proteoids. This unique morphology contributes to adaptive tolerance with soil‐climate duress prohibitive to most food Leguminosae. Objectives of this study were to determine tripartite components for mycorrhizal colonization and effective Rhizobium symbiosis with proteoid nodulation governing productivity, nitrogenase activity and subsequent nitrogen (N) fixation of Lupine. Highest nitrogenase activity levels with largest top growth, nodulation and seed yield resulted with mycorrhizal colonization plus calcium (Ca) treatments. Mycorrhizal colonization without soil fertility amendments resulted in higher yields and nodulation than all phosphorus (P), Ca, and potassium (K) soil fertility treatment combinations without mycorrhizae. Phosphorus+Ca soil additions were greater than either plant nutrient used separately without mycorrhizal colonization. Nodule histological determinants were highly correlated with governing cytosol enzyme activity levels. Nitrate reductase (NR)was significantly lower and phosphoenol‐pyruvate carboxylase (PEPC) was significantly higher with mycorrhizal colonization. Differences were not significant for cytosol components of amine‐amide N, aspartate transaminase (AST), glutamate dehydrogenase (GDH), glutamine syn‐thetase (GS) and glutamate oxoglutarate transaminase (GOGAT).     

菌剂与肥料配施对矿区复垦土壤白三叶草生长的影响

采用盆栽试验研究了矿区复垦土壤菌剂与肥料的不同配施对白三叶草(Trifolium repens Linn)生长的影响。结果表明: 双接种VA 菌根真菌(Glomus mossea)和根瘤菌(Rhizobium)能显著提高白三叶草根瘤数、根瘤鲜重和固氮酶活性, 根瘤数在有机肥双接种与无机肥双接种处理之间差异不显著, 而根瘤鲜重和固氮酶活性差异显著; 肥料与各菌剂组合处理中, 有机肥双接种处理的白三叶草分枝数、干物质重最大; 在白三叶草生长40 d 和150 d 时, 双接种处理的叶片数均为各处理中最大值; 接种VA 菌根真菌、根瘤菌和双接种均可增加白三叶草根系的菌根侵染率和土壤孢子数, 总体表现为双接种处理＞接种VA 菌根真菌＞接种根瘤菌, 有机肥相应处理＞无机肥相应处理＞对照; 肥料与菌剂的配合施用可有效提高植物对土壤氮、磷、钾养分的吸收。在矿区复垦土壤上有机肥与VA 菌根真菌和根瘤菌菌剂配施能显著促进白三叶草的生长, 是提高矿区复垦土壤植被恢复中比较适宜的组合方式。     

Mycorrhiza‐soil fertility effects on regrowth,nodulation and Nitrogenase activity of siratro (Macroptilium atropurpureum (DC) Urb.)

Siratro (Macroptilium atropurpureum (DC) Urb.) is a vigorous perennial forage legume with good potential for improving pastures in the extensive neotropical regions of the world. It is well adapted to a wide range of soil and climatic conditions. The objective of these studies was to determine effects of Glomus fasciculatum colonization, rigorous defoliation, and soil fertility treatments to a Psammentic Paleustalf (Eufaula) soil on growth, regrowth, nodulation, and nitrogenase activity (C₂H₂ red.) of Siratro inoculated with Rhizobium leguminosarum Frank. Top growth increased significantly with soil K and P amendment and with mycorrhiza colonization. Nodulation and nitrogenase activity were correlated with highly significant increases from G. fasciculatum, P treatments and K additions to 300 mg K kg^‐1 soil. Growth and peduncles of nonclipped plants increased about 4 fold from 90 to 225 day age with mature seed yield increasing about 10 fold; nodule mass and nitrogenase activity levels approximately doubled. Regrowth response of plants defoliated at 45 day intervals, following their initial 90 day age, was somewhat constant between clippings for magnitude of regrowth 12.3–13.8g, development in number of peduncles 4.0–6.8, seed yield 1.4–2.6g, nodulation 2.9–3.7g, and nitrogenase activity 73.9–95.8μ mol C₂H₄g^‐1 nodule. Multiple regression for nitrogenase = 0.55 g top wt. + 0.63 g nodule wt. + 1.91 day age ‐ 0.07 peduncle no., R² = 0.85 and C.V. = 14.3%. Favorable tripartite symbiosis with both effective Rhizobium and endophyte mycorrhiza were essential for high levels of symbiotic nitrogen fixation.     

Soil fertility effects with tripartite symbiosis for growth,nodulation and nitrogenase activity of vicia faba L

Fababean (Vicia faba L.) is one of the oldest known important grain legume food crops grown within the temperate and subtropical regions of the world. This species is adapted for both forage and food grain production as a cool season annual crop on a wide range of soil and climatic conditions with effective tripartite symbiosis. Both Rhizobium and endophyte mycorrhiza are essential for high levels of production and symbiotic N₂ fixation. The objective of these greenhouse and field studies was to determine effects of Glomus fasciculatum colonization with soil fertility treatments to a Psammentic Paleustalf (Eufaula series) on growth, nodulation, nitrogenase activity and nodule composition for V. faba, var. Major, fuh Rumi (Nile) inoculated with R. leguminosarum Frank.

Top growth and nodule mass were increased approximately 10 fold and nitrogenase activity about 7 fold with the highly significant effect of mycorrhiza and response to low soluble Ca₃(PO₄)₂ fertilization in greenhouse studies. With both effective mycorrhiza and Rhizobium inoculation in the field experiments, seed yields were correlated with top growth (r = 0.841). Phosphorus and Ca fertilization resulted in highly significant increases in seed yields. Nitrogenase activity was correlated with nodule wt. (r = 0.958) and highly significant increases resulted with P and Ca soil amendment. Plant nutrient element composition of nodules increased with the fertilization treatments for P, Ca and increased K levels. Sodium content decreased significantly with increased K fertilization (r = ‐0.846). Potassium composition increased significantly with P content (r = 0.523). Enhanced N₂‐fixation along with increased high protein forage and food grain production with Fababeans have much potential. However, soil fertility and management techniques for improved production include effective mycor‐rhizal colonization.     

Structural stability of an Alfisol under various fallow management practices in southwestern Nigeria

The effects of legume‐based soil management on soil dispersion were studied on an Alfisol between 1994 and 1995 in an experiment which was established in 1989 in southwestern Nigeria. The fallow systems, which constituted the main plots in the split‐plot experiment, included natural fallow, Pueraria phaseoloides (Roxb.) Benth, and Leucaena leucocephala Lam de Wit. The subplots were 25, 33, 50 and 100 per cent cropping intensities. Apart from indices of soil dispersion such as water‐dispersible clay and dispersion ratio, the fractal theory was applied to describe the fragmentation of soil aggregates less than 4 mm under the systems and cropping intensities. Although water dispersible clay was less than 60 g kg⁻¹ in the 0–15 cm soil depth because it was inherently low in clay content, the soil dispersion ratio was generally above 50 per cent. Also, the fractal dimensions, which ranged between 2.75 and 2.89, were similar among the fallow systems with cropping intensities for the surface soil. However, the interaction of slope position with season caused significant differences in fractal parameters, suggesting that the processes of soil degradation were different for the upper and lower slopes even with similar microaggregate distribution. The soil was inherently vulnerable to soil dispersion, although, the fallow management systems with less than 100 per cent cropping intensity would maintain soil structure at similar level as the forest. Copyright © 2001 John Wiley & Sons, Ltd.     

Effect of several Rhizobium strains on nodulation,nitrogen uptake and yield of chickpeas (Cicer arietinum L.)

The effect of soil sterilization, and seed inoculation with three Rhizobium strains (3889, CP5b and IC 26) were studied on 5 chickpea (Cicer arietinum L.) genotypes (Jordan local, ILC 72 from Spain, ILC 484 from Turkey, C 235 from India, and ILC 1272 from U.S.A.). The main objective of the work was to investigate the effect of inoculation with different Rhizobium strains on yield, nodulation and other agronomic characteristics of different chickpea genotypes. Inoculation with Rhizobium resulted in a significant increase in grain yield for all genotypes tested. The average increase due to inoculation was 110% over the uninoculated control. Inoculation resulted in more nodules, greater nodule fresh weight and higher nitrogen uptake. The various Rhizobium strains differed in their effects. Genotypes responded differently to inoculation.     

Reaction of Mycorrhizal and Nonmycorrhizal Leucaena leucocephala to Charcoal Amendment of Mansand and Soil

A series of experiments were conducted to evaluate the influence of charcoal on the development of arbuscular mycorrhiza (AM) on Leucaena leucocephala roots and the contribution of the symbiosis to the phosphorus (P) nutrition and growth of the legume. Arbuscular mycorrhizal fungal colonization of plants raised in Mansand (crushed basalt) in the first experiment was reduced if the medium was amended with fine charcoal and not with coarse charcoal. Charcoal amendment had no effect on AM fungal colonization, AM symbiotic effectiveness measured as pinnule (subleaflet) P content, or on growth of L. leucocephala in soil in the first experiment and in Mansand and in soil in subsequent experiments. However, AM fungal colonization of L. leucocephala roots, P content of pinnules, and growth of the legume were significantly enhanced (P < 0.05) by AM fungal inoculation in all experiments regardless of the growth medium used or charcoal amendment.