Yield of submerged paddy and uptake of Zn,P and N as affected by liming and Zn fertilizers

The effects of CaCO₃, Zn sources and levels on the yield of submerged paddy and uptake of Zn, P and N to paddy were studied in green-house at Haryana Agricultural University, Hissar. Powdered CaCO₃ was mixed at 0,4 and 8 per cent and Zn was added at 0,5 and 10 ppm through ZnSO₄.7H₂O, ZnO and Zn EDTA separately. Dry weight at tillering and heading and grain and straw at maturity decreased significantly with 4 and 8 per cent CaCO₃ in comparison to the control. Increasing Zn application increased the dry weight and grain yield. Zn EDTA gave highest yield of paddy followed by ZnSO₄.7H₂O and ZnO.Increasing the application of CaCO₃ from 0–8 per cent decreased the concentration and uptake of Zn and increasing Zn application from 0–10 ppm increased concentration and uptake of Zn in paddy at tillering, heading and maturity. Zn EDTA gave the highest concentration and uptake of Zn followed by ZnSO₄.7H₂O and ZnO. There was interaction between Zn sources and CaCO₃.The concentration and uptake of N and P in paddy dry matter at tillering and heading and straw and grain at maturity decreased as compared to control with increasing CaCO₃ addition. The concentration and uptake of N increased and that of P decreased in paddy dry matter straw and grain with increasing Zn application. The highest concentration of N was observed with ZnO, followed by ZnSO₄.7H₂O and Zn EDTA. But highest uptake of N was observed with Zn EDTA followed by ZnSO₄.7H₂O and ZnO. As regards concentration and uptake of P, it was highest with ZnO followed by ZnSO₄.7H₂O and Zn EDTA.     

Production of lactic acid and ethanol by Rhizopus oryzae integrated with cassava pulp hydrolysis

Cassava pulp was hydrolyzed with acids or enzymes. A high glucose concentration (>100 g/L) was obtained from the hydrolysis with 1 N HCl at 121 °C, 15 min or with cellulase and amylases. While a high glucose yield (>0.85 g/g dry pulp) was obtained from the hydrolysis with HCl, enzymatic hydrolysis yielded only 0.4 g glucose/g dry pulp. These hydrolysates were used as the carbon source in fermentation by Rhizopus oryzae NRRL395. R. oryzae could not grow in media containing the hydrolysates treated with 1.5 N H₂SO₄ or 2 N H₃PO₄, but no significant growth inhibition was found with the hydrolysates from HCl (1 N) and enzyme treatments. Higher ethanol yield and productivity were observed from fermentation with the hydrolysates when compared with those from fermentation with glucose in which lactic acid was the main product. This was because the extra organic nitrogen in the hydrolysates promoted cell growth and ethanol production.     

Semisolid fermentation of ryegrass straw

Candida utilis, Aureobasidium pullulans, and Trichoderma viride were grown on pretreated ryegrass straw. The pretreatment consisted of hydrolysis of straw with 0.5 N H₂SO₄ (water-substrate, 3:1) at 121 C, 100 C, and room temperature and adjustment of the hydrolysate to pH 4.5 to 5.0 with 5 N NH₄OH. The 121 C pretreatment yielded a material containing 30% sugar and 2.3% N. The fermentation was carried on semisolid substrate (moisture level, 75%) in rotating jars for 2 to 3 days at room temperature. The organisms grew rapidly during the period from 18 to 42 h of incubation. During this period the number of microbial cells increased by 20- to 200-fold, and the level of NH₃-N decreased from 1.3 to 0.9%. The fermentation resulted in a fourfold increase in protein, fivefold increase in crude fat, and 40% increase in the digestibility of straw. The best result in terms of increasing protein and digestibility of straw was obtained when C. utilis was grown on straw preheated at 121 C.     

Comparison of Seven Chemical Pretreatments of Corn Straw for Improving Methane Yield by Anaerobic Digestion

Agriculture straw is considered a renewable resource that has the potential to contribute greatly to bioenergy supplies. Chemical pretreatment prior to anaerobic digestion can increase the anaerobic digestibility of agriculture straw. The present study investigated the effects of seven chemical pretreatments on the composition and methane yield of corn straw to assess their effectiveness of digestibility. Four acid reagents (H₂SO₄, HCl, H₂O₂, and CH₃COOH) at concentrations of 1%, 2%, 3%, and 4% (w/w) and three alkaline reagents (NaOH, Ca(OH)₂, and NH₃·H₂O) at concentrations of 4%, 6%, 8%, and 10% (w/w) were used for the pretreatments. All pretreatments were effective in the biodegradation of the lignocellulosic straw structure. The straw, pretreated with 3% H₂O₂ and 8% Ca(OH)₂, acquired the highest methane yield of 216.7 and 206.6 mL CH₄ g VS ⁻¹ in the acid and alkaline pretreatments, which are 115.4% and 105.3% greater than the untreated straw. H₂O₂ and Ca(OH)₂ can be considered as the most favorable pretreatment methods for improving the methane yield of straw because of their effectiveness and low cost.     

Solid state coordination chemistry of the oxovanadium-diphosphonate system: Structural consequences of aryl tethers on materials of the type cation/VxOy/diphos, where cation = organoammonium and diphos = 1,4-phenyldiphosphonic acid

Hydrothermal reactions of V₂O₅, 1,4-phenyldiphosphonic acid and an appropriate organoamine, in the presence of HF as solubilizer, were exploited to prepare a series of materials of the general type [organoammonium cation]_n[V_xO_y(H_mO₃PC₆H₄PO₃H_p)₃]. Compound 1, [H₃N(CH₂)₄NH₃][V₂O₄(O₃PC₆H₄PO₃)], exhibits a one-dimensional V-P-O substructure, linked through the phenyl tethers of the ligand into a layer. Compound 1 is a unique example of a V(V)-diphosphonate phase. Compounds 2 and 3, [H₃N(CH₂)₂NH₃][V₂O₂(O₃PC₆H₄PO₃H)₂] and [H₂pip][V₂O₂(O₃PC₆H₄PO₃H)₂] (H₂pip = piperazinium), exhibit identical two dimensional substructures, constructed from ribbons connected through the phenyl tethers of the ligands. The three-dimensional framework of [H₃N(CH₂)₇NH₃]₂[V₃O₄(O₃PC₆H₄PO₃)₂] (4) consists of V-P-O layers characterized by trinuclear V(IV)-oxide subunits and 9 and 12 polyhedral connect rings; the layers are buttressed by the phenyl spacers to provide the typical “pillared” layer structure common to metal diphosphonate materials. Compound 5, [H₂dabco][V₂F₃O₂(O₃PC₆H₄PO₃H)]·H₂O, is also three-dimensional with oxyfluoro-vanadium(IV) chains linked through the diphosphonate ligands into a framework structure with void spacers to accommodate the {H₂dabco}²⁺ cations (dabco = diamino bicyclo octane). The magnetic properties of 2-5 reflect the structural characteristics of the materials.     

Synthesis,crystal structure and fluorescent characterization of a novel lanthanide tetraphosphonate with a layered structure

Hydrothermal reactions of Gd(III) nitrate with N,N,N′,N′-tetramethylenephosphono-1,4-diaminobutane, (H₂O₃PCH₂)₂N–(CH₂)₄–N(CH₂PO₃H₂)₂ (H₈L), afforded a novel Gd(III) phosphonate, namely, Gd[(O₃PCH₂)(HO₃PCH₂)N(H)(CH₂)₄N(H)(CH₂PO₃H)₂] · 2H₂O, [Gd(H₅L)] · 2H₂O. Its structure was established by a single-crystal X-ray diffraction study. In this compound, the Gd(III) ion is coordinated by eight phoshonate oxygen atoms from five different phosphonate groups, which belong to five different phosphonic ligands. Each Gd atom is connected with its neighboring Gd atoms by two phosphonate oxygens, forming a gadolinium phosphonate slab along the a-axis. Such slabs are bridged by tetraphosphonate H₅L anions, resulting in a 〈0 1 1〉 layer with the butane groups toward the interlayer space. These layers are further interlinked by strong hydrogen bonds formed by uncoordinated phosphonate oxygens into a 3D supermolecular structure. Luminescent studies indicate that this compound exhibits a broad blue fluorescent emission band at 441 nm.     

Synthesis, structure and characterization of two Pb(II) phosphonates with layered or 3D structures

Hydrothermal reactions of lead(II) acetate and N-cyclohexylimino-bis(methylenephosphonic acid) (C₆H₁₁N(CH₂PO₃H₂)₂, H₄L¹) or N,N′-bis(phosphonomethyl)-6-aminocaproic acid (HO₂C(CH₂)₅N(CH₂PO₃H₂)₂, H₅L²), respectively, resulted in two different new lead diphosphonates, namely, Pb₂L¹ · H₂O (1) and Pb₂[HL²] (2). Their crystal structures have been determined by single crystal X-ray diffraction. The structure of compound 1 contains a 〈0 0 1〉 lead(II) diphosphonate hybrid layer formed by Pb(II) ions interconnected by L¹ anions. Such layers are further interlinked by van der Waals force into a supramolecular structure. In compound 2, the Pb(II) ions are interconnected by the -N(CH₂PO₃H)(CH₂PO₃) and -CO₂ groups of the HL² anions forming an organic-inorganic hybrid layer. These layers are further interlinked by the -(CH₂)₅ groups of the HL² anions into a 3D structure.     

Release of monomeric sugars from Miscanthus sinensis by microwave-assisted ammonia and phosphoric acid treatments

Microwave-assisted ammonium hydroxide (NH₄OH) followed by phosphoric acid (H₃PO₄) treatments were used to release monomeric sugars from Miscanthus sinensis grown in Cha-Chueng-Sao province, Thailand. Treatment with 1.0% (w/v) NH₄OH, 15:1 liquid-to-solid ratio (LSR) at 120 °C temperature for 15 min liberated 2.9 g of monomeric sugars per 100 g of dried biomass, whereas the corresponding yield for a treatment with 1.78% v/v H₃PO₄, 15:1 LSR at 140 °C for 30 min was 62.3 g/100 g. The two-stage pretreatment, treatment with NH₄OH at 120 °C temperature for 15 min followed by treatment with H₃PO₄ at 140 °C for 30 min, impressively provided the highest total monomeric sugar yield of 71.6 g/100 g dried biomass.     

The utilization of phosphorus from muds by the phytoplankter,Scenedesmus dimorphus,and the significance of these findings to the practice of pond fertilization

Muds from 12 types of soils were used as the only source of phosphorus in cultures of Scenedesmus dimorphus. Some muds supported as much algal growth as was obtained with 0.075 to 0.5 mg/1 of phosphorus, while little or no growth occurred in cultures which contained other muds as a source of phosphorus. Algal growth was correlated with the fractions of soil phosphorus which were extracted with the following solutions; I — the phosphorus — free nutrient solution, II — 0.05N HCl plus 0.025N H₂SO₄, III — 0.002N H₂SO₄ plus 3 g/l of K₂SO₄, and IV — 0.1N HCl plus 0.03N/NH₄F. Additions of phosphorus to the soils prior to their use as muds increased the suitability of some as sources of phosphorus, but for others the added phosphorus was so tightly bound to the soil that little or none was available to S. dimorphus. The findings indicate that the type of soil in a pond will likely have a large influence on the efficiency of fertilization with phosphate fertilizers.

     

A rapid,ideal, and eco-friendlier protocol for quantifying proline

Proline, a stress marker, is routinely quantified by a protocol that essentially uses hazardous toluene. Negative impacts of toluene on human health prompted us to develop a reliable alternate protocol for proline quantification. Absorbance of the proline-ninhydrin condensation product formed by reaction of proline with ninhydrin at 100 °C in the reaction mixture was significantly higher than that recorded after its transfer to toluene, revealing that toluene lowers sensitivity of this assay. λ _max of the proline-ninhydrin complex in the reaction mixture and toluene were 508 and 513 nm, respectively. Ninhydrin in glacial acetic acid yielded higher quantity of the proline-ninhydrin condensation product compared to ninhydrin in mixture of glacial acetic acid and H₃PO₄, indicating negative impact of H₃PO₄ on proline quantification. Further, maximum yield of the proline-ninhydrin complex with ninhydrin in glacial acetic acid and ninhydrin in mixture of glacial acetic acid and H₃PO₄ was achieved within 30 and 60 min, respectively. This revealed that H₃PO₄ has negative impact on the reaction rate and quantity of the proline-ninhydrin complex formed. In brief, our proline quantification protocol involves reaction of a 1-ml proline sample with 2 ml of 1.25 % ninhydrin in glacial acetic acid at 100 °C for 30 min, followed by recording absorbance of the proline-ninhydrin condensation product in the reaction mixture itself at 508 nm. Amongst proline quantification protocols known till date, our protocol is the most simple, rapid, reliable, cost-effective, and eco-friendlier.     

Production of Glucose Isomerase by Streptomyces flavogriseus

A microorganism that produces glucose isomerase was isolated from soil and identified as a strain of Streptomyces flavogriseus. The organism produced a large quantity of glucose isomerase when grown on straw hemicellulose, xylan, xylose, and H₂SO₄ hydrolysate of ryegrass straw. The organism produced glucose isomerase both intra- and extra-cellularly. The highest level of intracellular glucose isomerase (3.5 U/ml) was obtained in about 36 h by a culture grown on straw hemicellulose; the extracellular enzyme (1.5 U/ml) appeared in cultures grown for about 72 h. About equal levels of enzyme were produced in cultures grown on straw hemicellulose, xylan, xylose, and H₂SO₄ hydrolysate of straw, but production of the enzyme was drastically reduced when the organism was grown on other carbon sources. As a nitrogen source, corn steep liquor produced the best results. Soy flour extract, yeast extract, and various peptones also were adequate substrates for glucose isomerase production. Addition of Mg²⁺, Mn²⁺, or Fe²⁺ to the growth medium significantly enhanced enzyme production. The organism, however, did not require Co²⁺, which is commonly required by microorganisms used in the production of glucose isomerase.     

Studies on fermentation of sorghum silage during storage,and its effect on milch animals

Three silages: sorghum alone (T₁); sorghum + 0.5% urea (T₂); and sorghum + wheat straw in the ratio of 4:1 (T₃), were assessed for their biochemical products and stability. The performance of milch cattle maintained on these forage diets was compared with wheat straw as a control (T₄). Animals of all four groups were given sufficient concentrate to satisfy their nutrient requirements. On the basis of fermentation products all three silages were classed as ‘good’ to ‘very good’. The palatability of these silages was relatively better than that of the control (T₄). Milk production appeared to be better with non-urea silages, but not significantly so.     

Vibrational spectra of the diammineplatinum(II) disodium 5′-uridine monophosphate blue complex

The blue complexes produced by reaction of cis-diamminediaquoplatinum(II) nitrate, [cis-Pt(NH₃)₂(H₂O)₂](NO₃)₂, with disodium 5′-uridine monophosphate, 5′-UMP(Na₂), in H₂O and D₂O have been investigated by FT-IR spectroscopy. On the basis of the spectral changes observed in the CO stretching region during the reactions, chelation of the amidate N(3)··O(2) moiety to Pt(II) appears to be more likely than N(4)··O(4) chelation. The antisymmetric PO stretching mode of the PO_3²⁻ group of 5′-UMP splits into a triplet on complex formation indicating that PO_3²⁻ plays an important role in the structure of the platinum blue complexes. In addition, the sugar moiety of 5′-UMP apparently adopts a predominantly C(3′)-endo conformation in the solid blue complex. Finally, Raman microprobe spectroscopy of the solid provides some evidence for PtN(3) bond formation.     

Effects of Some Environmental Factors on Growth Characteristics of Candida utilis on Peat Hydrolysates

Samples of peat from Pine Island and Brookston bogs in Minnesota were hydrolyzed with various concentrations of HCl or H₂SO₄ solutions, before or after debituminization (an extraction process used to remove waxy materials, bitumens, from peat), to produce peak hydrolysates as growth substrates for Candida utilis. Hydrolysates were neutralized with concentrated NaOH solution to pH 3.5, 4.5, 5.0, 5.5, 6.0, and 7.0. The precipitated humates were removed by filtration. The resulting peat hydrolysates were amended with reagent-grade K₂HPO₄, K₂SO₄, and MgSO₄, 200, 100, and 50 mg per liter of peat hydrolysate, respectively. The debituminized peat produced more total nitrogen (TN) and reducing substances (RS) than the nondebituminized peat. Peat hydrolysates produced by HCl solutions contained slightly higher RS and TN than those produced by H₂SO₄ solutions; however, the latter were better growth substrates than the former. The yield coefficients in both H₂SO₄ and HCl hydrolysates initially decreased at 12 to 24 h and then increased gradually over the remaining incubation period (24 to 96 h). As TN and RS were increased, an increase in cell density, biomass, and productivity was observed. In contrast, a decrease in specific growth rate occurred as the RS and TN were increased. The generation time of C. utilis was affected by the concentrations of RS and TN. A peak substrate yield coefficient was found at pH 5.0 in HCl hydrolysates and at pH 6.0 to 6.5 in H₂SO₄ hydrolysates. Good linear correlation coefficients were found between RS and biomass of C. utilis. The coefficients of correlation increased as the TN level in hydrolysates was increased.     

Interaction effect of sulphur and phosphorus on growth and nutrient content of moong (Phaseolus aureus L.)

Summary Sulphur-phosphorus interaction has been studied in a greenhouse experiment on a soil, deficient both in S and P with moong (Phaseolus aureus) as the test crop. The treatments were in the factorial combination of five levels of S and P (0, 5, 10, 20 and 40 ppm) applied as CaSO₄. 2H₂O and Ca(H₂PO₄)₂. H₂O respectively. A uniform treatment of N and K was made. The yield of vegetative tissues and grains increased with the application of S and P individually but decreased when S and P were applied in different combinations. Sulphur application increased S content but decreased P content in straw as well as in grains. Total P content increased with applied P and decreased with S application. Applied sulphur increased and phosphorus decreased the protein content in moong grains. Changes in N:S ratio in interaction was found to exist between S and P on the yield, grain quality, concentration and total removal of sulphur and phosphorus by Moong crop The antagonistic effect of sulphur and phosphorus fertilizer on the uptake and utilization of each other was more conspicuous when they were applied together. re]19760106     

The seasonal dynamics of amino acids and other nutrients in Alaskan Arctic tundra soils

Past research strongly indicates the importance of amino acids in the N economy of the Arctic tundra, but little is known about the seasonal dynamics of amino acids in tundra soils. We repeatedly sampled soils from tussock, shrub, and wet sedge tundra communities in the summers of 2000 and 2001 and extracted them with water (H₂O) and potassium sulfate (K₂SO₄) to determine the seasonal dynamics of soil amino acids, ammonium (NH₄⁺), nitrate (NO₃^–), dissolved organic nitrogen (DON), dissolved organic carbon (DOC), and phosphate (PO₄^2–). In the H₂O extractions mean concentrations of total free amino acids (TFAA) were higher than NH₄⁺ in all soils but shrub. TFAA and NH₄⁺ were highest in wet sedge and tussock soils and lowest in shrub soil. The most predominant amino acids were alanine, arginine, glycine, serine, and threonine. None of the highest amino acids were significantly different than NH₄⁺ in any soil but shrub, in which NH₄⁺ was significantly higher than all of the highest individual amino acids. Mean NO₃^– concentrations were not significantly different from mean TFAA and NH₄⁺ concentrations in any soil but tussock, where NO₃^– was significantly higher than NH₄⁺. In all soils amino acid and NH₄⁺ concentrations dropped to barely detectable levels in the middle of July, suggesting intense competition for N at the height of the growing season. In all soils but tussock, amino acid and NH₄⁺ concentrations rebounded in August as the end of the Arctic growing season approached and plant N demand decreased. This pattern suggests that low N concentrations in tundra soils at the height of the growing season are likely the result of an increase in soil N uptake associated with the peak in plant growth, either directly by roots or indirectly by microbes fueled by increased root C inputs in mid-July. As N availability decreased in July, PO₄^2– concentrations in the K₂SO₄ extractions increased dramatically in all soils but shrub, where there was a comparable increase in PO₄^2– later in the growing season. Previous research suggests that these increases in PO₄^2– concentrations are due to the mineralization of organic phosphorus by phosphatase enzymes associated with soil microbes and plant roots, and that they may have been caused by an increase in organic P availability.     

The influence of phosphorus and nitrogen on millet and clover growing in soils affected by salinity

Summary The growth of foxtail millet and clover in soils of varying degrees of salinity (0.5 to 13 mmhos/cm), treated with nitrogen and phosphorus, was studied. Salinity levels were achieved by addition of sodium chloride. Nitrogen (10 to 60 ppm N) and phosphorus (6.4 to 44.8 ppm P) were added as NH₄NO₃ and H₃PO₄, respectively. The growth of millet decreased sharply with increase in soil salinity, when N-P treatments were not applied. The development of this plant altered under saline conditions, however, when nitrogen and phosphorus were added; various N-P combinations affected plant growth in saline soil differently. Phosphorus, when applied at relatively high rates, significantly improved plant growth. Increased rates of nitrogen in the N-P treatments generally had no significant effect on growth; it was reduced when the N/P ration was highest. Clover ceased to grow when the salinity of the soil exceeded 7 mmhos/cm and no N-P was added. Phosphorus enhanced the growth of clover, and at high rates of its application in the N-P combinations, clover grew even at the highest salinity level tested (13 mmhos/cm). Nitrogen increase had no marked effect on plant development. Comparing enhancement of growth at high salinity levels, clover was somewhat less affected by the N-P treatment than millet. The top/root ratio of clover generally increased with increase of phosphorus in the N-P combinations. This research (Parts I and II) was supported in part by a grant from the U.S. Department of Agriculture under P. L. 480.     

Efficient itaconic acid production by Aspergillus terreus: Overcoming the strong inhibitory effect of manganese

Itaconic acid (IA), a building block platform chemical, is produced industrially by Aspergillus terreus utilizing glucose. Lignocellulosic biomass can serve as a low cost source of sugars for IA production. However, the fungus could not produce IA from dilute acid pretreated and enzymatically saccharified wheat straw hydrolyzate even at 100-fold dilution. Furfural, hydroxymethyl furfural and acetic acid were inhibitory, as is typical, but Mn²⁺ was particularly problematic for IA production. It was present in the hydrolyzate at a level that was 230 times over the inhibitory limit (50 ppb). Recently, it was found that PO₄³⁻ limitation decreased the inhibitory effect of Mn²⁺ on IA production. In the present study, a novel medium was developed for production of IA by varying PO₄³⁻, Fe³⁺ and Cu²⁺ concentrations using response surface methodology, which alleviated the strong inhibitory effect of Mn²⁺. The new medium contained 0.08 g KH₂PO₄, 3 g NH₄NO₃, 1 g MgSO₄·7H₂O, 5 g CaCl₂·2 H₂O, 0.83 mg FeCl₃·6H₂O, 8 mg ZnSO₄·7H₂O, and 45 mg CuSO₄·5H₂O per liter. The fungus was able to produce IA very well in the presence of Mn²⁺ up to 100 ppm in the medium. This medium will be extremely useful for IA production in the presence of Mn²⁺. This is the first report on the development of Mn²⁺ tolerant medium for IA production by A. terreus.     

Bioconversion of wheat straw to ethanol: Chemical modification,enzymatic hydrolysis,and fermentation

Native wheat straw (WS) was pretreated with various concentrations of H₂SO₄ and NaOH followed by secondary treatments with ethylene diamine (EDA) and NH₄OH prior to enzymatic saccharification. Conversion of the cellulosic component to sugar varied with the chemical modification steps. Treatment solely with alkali yield 51–75% conversion, depending on temperature. Acid treatment at elevated tempeatures showed a substantial decrease in the hemicellulose component, whereas EDA-treated WS (acid pretreated) showed a 69–75% decrease in the lignin component. Acid-pretreated EDA-treated straw yielded a 98% conversion rate, followed by 83% for alkali–NH₄OH treated straws. In other experiments, WS was pretreated with varying concentration of H₂SO₄ or NaOh followed by NH₄OH treatment prior to enzymatic hydrolysis. Pretreatment of straw with 2% NaOH for 4 h coupled to enzymatic hydrolysis yield a 76% conversion of the cellulosic component. Acid–base combination pretreatment yielded only 43% conversions. A reactor column was subsequently used to measure modification–saccharification–fermentation for wheat straw conversion on a larger scale. Thirty percent conversions of wheat straw cellulosics to sugar were observed with subsequent fermentation to alcohol. The crude cellulase preparation yielded considerable quantities of xylose in addition to the glucose. Saccharified materials were fermented directly with actively proliferating proliferating yeast cells without concentration of the sugars.     

Straw and Xylan Utilization by Pure Cultures of Nitrogen-Fixing Azospirillum spp

Azospirillum spp. were shown to utilize both straw and xylan, a major component of straw, for growth with an adequate combined N supply and also under N-limiting conditions. For most strains examined, a semisolid agar medium was satisfactory, but several strains appeared to be capable of slow metabolism of the agar. Subsequently, experiments were done with acid-washed sand supplemented with various carbon sources. In these experiments, authenticated laboratory strains, and all 16 recent field isolates from straw-amended soils, of both A. brasilense and A. lipoferum possessed the ability to utilize straw and xylan as energy sources for nitrogen fixation. Neither carboxymethyl cellulose nor cellulose was utilized. The strains and isolates differed in their abilities to utilize xylan and straw and in the efficiency of nitrogenase activity (CO₂/C₂H₂ ratio). Reasonable levels of activity could be maintained for at least 14 days in the sand cultures. Nitrogenase activity (acetylene reduction) was confirmed by ¹⁵N₂ incorporation. The level of nitrogenase activity observed was dependent on the time of the addition of acetylene to the culture vessels.