Characterization of soil phosphorus by anion exchange resin adsorption and P32-equilibration

Summary Adsorption of phosphate by the anion-exchange resin Dowex-2 was investigated. The resin adsorbed small quantities of P from solution quantitatively. The rate of P-adsorption by resin agitated in solution was proportional to the P-concentration in solution, and was independent of the rate of diffusion of adsorbed P in the resin. When 1 g of soil was shaken continuously with 1 g of resin in 100 ml of water, the rate of P-adsorption by the resin was controlled by the rate of P-release from the soil. Quantities of P adsorbed from soil by resin after different lengths of time were less than those equilibrated with P³² during the same time intervals. The curves showing quantity of P adsorbed vs. time could be satisfactorily described by the hypothesis that there were three simultaneous reactions differing in rate, each reaction being first-order with respect to P. The same was true of the P³²-equilibration data, except that the rate of the slowest reaction was apparently independent of time. In a group of 16 soils, the correlation between P adsorbed by the resin in 2 hours and P-availability to plants in the greenhouse, measured by the isotope-dilution method of Fried and Dean, was 0.95. The corresponding correlation between P extracted by the 0.25N HCl — 0.03N NH₄F extractant of Bray and Kurtz was 0.91.Joint contribution from the Iowa Agricultural Experiment Station and the Eastern Soil and Water Management Section, U.S. Department of Agriculture. Journal Paper No. J-2639 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 1183.Graduate Assistants, Professor of Soils, and Associate Professor of Chemistry, respectively.     

Biological transformations of phosphorus in soil

Summary Mathematical expressions were developed for calculating (1) the availability of soil phosphorus and nonradioactive inorganic fertilizer phosphorus to soil organisms, the measurements being expressed in terms of a standard source of inorganic phosphorus containing P³² added to the soil prior to incubation, and (2) the amounts of synthesized and mineralized organic phosphorus present in soils after incubation. Analytical procedures for obtaining the necessary data were described.Soil Phosphorus Research Project of the North Central Region. Contribution from the B.P.I.S.A.E., U.S. Department of Agriculture, and the Iowa Agricultural Experiment Station. Journal Paper No. J-2302 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 1183.Formerly Soil Scientist, U.S.D.A., and Collaborator, Iowa Agricultural Experiment Station; now Soil Scientist, Dow Chemical Co., Seal Beach, California. The author is indebted to Dr. L. A. Dean and Dr. C. A. Black for their many helpful suggestions in planning these investigations and preparing the data for publication.     

Penicillium urticae Bainier enumeration in soils

Summary A dilution plating method estimatedPenicillium urticae Bainier numbers in soil. This method, which used an agar layering technique and a cyclic incubation of 8 hours at room temperature (about 25°C) and 16 hours at 5°C, permitted the differential growth and sporulation in favor ofP. urticae B. over other common soil fungi.Procedures of extraction, paper chromatography, infrared analysis, and bioassay assayed for accumulated patulin. A combination of these methods routinely estimatedP. urticae B. numbers in soils and authenticated patulin production by selected isolates.Contribution from the Northern Plains Branch, Soil and Water Conservation Research Division, Agricultural Research Service, USDA, in cooperation with the Nebraska Agricultural Experiment Station, Lincoln. Published as Paper No. 2275, Journal Series, Nebraska Agricultural Experiment Station.Soil Scientist, USDA, Grand Junction, Colorado (formerly Chemist, USDA, Lincoln, Nebraska); and Microbiologist, USDA, Lincoln, Nebraska, respectively.     

The inhibition of seedling growth by crop residues in soil inoculated withPenicillium urticae Bainer

Summary Laboratory experiments were conducted to determine the effects of crop residues, without and withPenicillium urticae Bainer inoculation, on growth of wheat seedlings in soil. Fifty grams of Sharpsburg silty clay loam soil, containing 1% by weight of incorporated alfalfa, sorghum and corn stover residue, were placed in petri dishes, autoclaved, wetted to 40% moisture, and incubated at 24°C. for periods of 2, 3, and 4 weeks. One-half of the petri dishes were inoculated withP. urticae. Germination and seedling-shoot measurements were taken after 7 days of growth.The results of this study showed that (1) inoculation of soil generally reduced seedling height regardless of the residue treatment; (2) inoculation of soil containing corn and sorghum residues resulted in greater tissue production but reduced height of seedlings as compared to non-inoculated soils; and (3) in the absence of residues, the inoculated control soils were a better growth medium for wheat seedlings than were the non-inoculated control soils. In addition, alfalfa residues, especially in the presence ofP. urticae, were strongly inhibitory to the wheat seedlings, causing curling and reduced wheat-seedling root growth.Joint contribution from University of Nebraska and Soil and Water Conservation Research Division, Agricultural Research Service, U.S. Department of Agriculture, and Nebraska Agricultural Experiment Station, Lincoln, Nebraska, cooperating. Published with the approval of the Director as Paper No. 1242, Journal Series, Nebraska Agricultural Experiment Station.     

Patulin effects on wheat plants in field treatments

Summary Fall field patulin applications (500 µg/g of soil) to Cheyenne winter wheat seedlings at growth stages 0, 1, and 2, decreased germination, plant growth, winter survival, and tillering. Decreased tillering decreased the number of heads and grain yield. Spring patulin application of 250 and 500 µg/g of soil to wheat at growth stages 6, 7, 8, 9, and 10 decreased yields by decreasing the number of heads, kernels per head, and kernel weight. With fall patulin applications, yields were decreased more when patulin was applied near seeding. Spring patulin applications to wheat during sensitive heading stages decreased yield the most.Stages of wheat growth especially susceptible to patulin are the germination, stem-elongation, and flowering, which occur during the fall and spring when soil Penicillium urticae Bainier numbers are maximun and patulin has been extracted from the soil.Contribution from the Soil, Water, and Animal Waste Management Research Unit, North Central Region, Agricultural Research Service, U.S. Department of Agriculture, in cooperation with the Nebraska Agricultural Experiment Station, Lincoln. Published as Paper No. 4071, Journal Series, Nebraska Agricultural Experiment Station.Microbiologist, USDA, A.R.S. University of Nebraska, Lincoln; Soil Scientist, USDA, A.R.S. Fort Collins, Colorado; and Microbiologist, USDA, A.R.S. University of Nebraska, Lincoln, respectively.     

Root uptake coefficient for Cl ions in corn as affected by transpiration rates and solution concentration

Summary Root uptake rate and root uptake coefficient for Cl ions were determined in corn at two transpiration rates and three solution concentrations. Transpiration rate had pronounced effect on root uptake rate and root uptake coefficient especially at low solution concentration. Root uptake rate increased as the concentration of Cl ions in the solution increased. The root uptake coefficient decreased as Cl concentration in the solution increased from 20 meq/l to 40 meq/l but it did not change when the concentration was raised to 80 meq/l.Soil Physicist, Department of Soil & Water Engineering and Professor of Soils, Department of Soils, Punjab Agricultural University, Ludhiana, Punjab, India, respectively.Soil Physicist, Department of Soil & Water Engineering and Professor of Soils, Department of Soils, Punjab Agricultural University, Ludhiana, Punjab, India, respectively.     

Copper as essential to wheat reproduction

Summary The role of Cu in promoting the reproductive phase of growth was examined using Thatcher spring wheat (Triticum aestivum L.). Plants were grown in limed Bladen soil (pH 5.3) in a controlled growth room. The plants were first harvested when five leaves had developed (day 23) and some top leaves of Cu-deficient (-Cu) plants had rolled (withertip) indicating a Cu deficiency. The leaves were shorter on Cu than Cu-sufficient (+Cu) plants, and fewer leaves developed. As they entered the reproductive growth phase, +Cu plants accumulated reducing sugars and reduced 2, 3, 5- triphenyltetrazolium chloride (TTC) in their stems, while Cu plants had lower concentration of the reducing sugars and very little TTC was reduced indicating a reduction in energy and in reducing capacity. Thin-layer-chromatography showed that top leaves of Cu plants contained higher concentrations of aspartic acid, alanine, and serine; and less aminobutyric acid than +Cu plants. Nitrate, P, and K concentrations were higher, and Ca and Cu were lower in Cu than in +Cu plants.Contribution of U.S. Department of Agriculture, Agricultural Research Service, Plant Stress Laboratory, Northeast Region, Beltsville, MD 20705 and North Central Region, Department of Agronomy, University of Nebraska, Lincoln, NE 68583 as Paper No.5187, Journal Series, Nebraska Agricultural Experiment Station.Contribution of U.S. Department of Agriculture, Agricultural Research Service, Plant Stress Laboratory, Northeast Region, Beltsville, MD 20705 and North Central Region, Department of Agronomy, University of Nebraska, Lincoln, NE 68583 as Paper No.5187, Journal Series, Nebraska Agricultural Experiment Station.     

A centrifugation technique for separating ascospores from soil

Summary A centrifugation technique employing sucrose density gradient columns has been developed for separating fungus spores from soil mineral particles. Four pyrenomycetes plus a number of sterile isolates have been obtained by the use of this technique. The technique may be applicable to other types of fungi producing large, readily identifiable spores.Contribution from the Soil and Water Conservation Research Division, Agricultural Research Service, USDA, in cooperation with the Washington Agricultural Experiment Station. Scientific Paper 2830, Washington State University, College of Agriculture.     

Effect of moisture and oxidation status of alkaline rice soils on the adsorption of soil phosphorus by an anion resin

Summary Considerable effort was devoted to experimentally explaining the greater amount of anion resin-adsorbable P (ARAP) in water-saturated alkaline soils relative to moist soils with the purpose of explaining the phenomenon of increased P availability in flooded rice soils. ARAP increased when waterlogged conditions were imposed on soils, but the increase in ARAP occurred before reducing conditions were obtained. Reducing conditions did not increase ARAP. The increase in ARAP in the water-saturated alkaline soils was attributed to the enhanced P diffusion resulting from a decrease in tortuosity, thus indicating that increased P availability upon flooding could be due to increased P diffusion.Paper number 4533 of the Journal Series of the North Carolina Agricultural Experiment Station.Paper number 4533 of the Journal Series of the North Carolina Agricultural Experiment Station.     

Influence of temperature on colonization of spring barleys by vesicular arbuscular mycorrhizal fungi

The effects of three soil temperatures on growth of spring barleys (Hordeum vulgare L.) and on their root colonization by vesicular arbuscular mycorrhizal (VAM) fungi from agricultural soils in Montana (USA) or Syria at different inoculum concentrations were tested in soil incubators in the greenhouse. The number of mycorrhizal plants as well as the proportion and intensity of roots colonized increased with higher soil temperatures. VAM fungi from Montana, primarily Glomus macrocarpum, were cold tolerant at 11°C while those from Syria, primarily G. hoi, were heat tolerant at 26°C. Inoculum potential of Montana VAM fungi was higher than Syrian VAM fungi in cool soils. Harmal, selected from Syrian barley land races, had the highest colonization by mycorrhizal fungi of the cultivars tested.Journal Series Paper: J-2532 Montana Agricultural Experiment Station.     

Influence of soil oxygen and soil water on the accumulation of nutrients in avocado seedlings (Persea Americana mill.)

Summary This experiment was conducted in a greenhouse to study the influence of 2 soil-oxygen levels and 4 irrigation levels on the plant response, root decay, concentrations of 12 nutrients, as well as on total amounts of nutrients per avocado seedling (Persea americana Mill.).Reduced soil-oxygen supply to the roots significantly reduced the amount of dry weight per seedling, increased percentage of root decay, and reduced the concentrations of N, P, K, Ca, Mg, and B in the tops, while Na and Fe were increased. Concentrations of K, Mg, Na, and Cl in the roots were decreased, while N and Ca were increased with decreased soil oxygen supply to the roots. Total amounts of N, P, Ca, Mg, Na, and Cl per seedling were decreased with the low soil-oxygen supply to the roots.Only slight differences in dry weight of the tops of seedlings were found. The highest degree of root decay was caused by the irrigation treatment where a water table was present. In the tops, concentrations of N, P, K, Mg, Na, Zn, Cu, Mn, B, and Fe were significantly influenced by differential irrigation treatments; in the roots, concentrations of P, K, Ca, Mg, Na, and Cl were also significantly influenced; and total amounts of N, P, Mg, and Cl the whole seedling were likewise significantly influenced.Significant interactions were noted between the soil-oxygen and irrigation treatments on the dry weight of tops, roots, and total amounts of dry weight produced per seedling. The lowest amount of dry weight of roots and the highest degree of root decay were found in the avocado seedlings grown under low soil-oxygen supply and the irrigation treatment where a water table was present. Several significant interactions between soil oxygen and irrigation on the concentrations of N, P, K, Ca, Zn, and Mn are discussed.University of California, Citrus Research Center and Agricultural Experiment Station, Riverside, California. The research reported in this paper was supported in part by NSF Grant GB-5753x.     

A novel method to measure the effect of temperature on diffusion of plant-available nitrogen in soil

Background and aims

Soil temperature influences nitrogen (N) diffusion in soil but until now, such effects have been difficult to quantify. This study aimed at estimating the effect of temperature on the diffusive fluxes of plant-available N forms in two contrasting soils.

Methods

Using a novel technique based on micro-dialysis, we established relationships between diffusive fluxes and temperature in aqueous solutions and in soil samples.

Results

Averaged for all compounds, the decreases of diffusive fluxes from the soil to the microdialysis sampler were 3.8 and 4.7% per degree Celsius in an agricultural and a boreal forest soil, respectively. The temperature-related shift of diffusive flux was, however, significantly dependent on molecular weight of the N compound. In accordance with established functions for temperature effects on diffusive fluxes, the non-linearity of this relationship resulted in a greater temperature response for small N compounds compared to larger compounds.

Conclusions

Our results show that, all other factors being equal, the relative contribution of smaller N compounds to the diffusive flux of total plant-available N increases with increasing soil temperatures.     

Soil water potential as a factor in the ecology ofFusarium roseum f. sp.cerealis ‘Culmorum’

Summary The soil water potential (inferred from vapor pressure measurements by thermocouple psychrometry) influenced both chlamydospore germination and continuing growth of germlings ofFusarium roseum f. sp.cerealis ‘Culmorum’ the same way in two different soils. Chlamydospore germination in both Ritzville silt loam (RSL) and Palouse silt loam (PSL) amended with about 2,500 ppm C (as glucose) and 250 ppm N (as ammonium sulfate) was 40–50 per cent in 24 hours at water potentials down to −50 to −60 bars. Some germination occurred by 72 hours at −80 to −85 bars in both soils but not at lower potentials. At a potential of −10 bars or higher, germ tubes lysed or converted into new chlamydospores within 48–72 hours after germination, whereas at lower potentials germlings branched and appeared to grow for at least 6 days. Bacterial numbers/g of RSL, 24 and 72 hours after adding nutrients, were 200 to 300 times greater in soil at water potentials of −5 bars or more than in comparably treated soil at about −14 to −17 bars or less. Markedly reduced bacterial activity appeared to coincide with a water potential of about −9 to −10 bars. When streptomycin and neomycin (300 ppm each) were mixed into the soil in addition to nutrients, the survival of germlings of Culmorum was greatly enhanced, even in soil at potentials of less than −1 bar. Indications were that soil water potentials of −10 bars or more favored bacterial activity, and that this in turn repressed growth of germlings of Culmorum. Culmorum infections of below-ground parts of wheat are serious primarily in drier soils, possibly because the fungus escapes bacterial antagonism but can still extract water for growth. Cooperative investigations, Crops Research and the Water and Soil Conservation Research Divisions, Agricultural Research Service, U.S. Department of Agriculture and the Agricultural Experiment Stations of Idaho, Montana, Oregon, Utah, and Washington. Scientific Paper No.3152, College of Agriculture, Washington State University, Pullman.     

Increased P diffusion as an explanation of increased p availability in flooded rice soils

Summary Phosphorus supply factors (capacity, kinetic, intensity, and diffusivity) and plant growth were the approaches used to assess P supply of flooded rice soils. Increases in the capacity, intensity, and kinetic factors, as measured by E-value, solution P concentration, and soil P release rate to a distilled water sink respectively, were unpronouced and infrequent upon water-saturation of ten soils. However, increases in the diffusitivity factor, as measured by ³²P diffusion coefficients, were at least ten-fold as soil moisture increased. The greatest increases in P diffusion occurred as soil moisture increased beyond one-third bar.Using a P fertilized soil or P treated powdered cellulose as the P source and a minus P nutrient solution to nourish a split root system with water and nutrients, data were obtained which suggested that P uptake and rice-shoot growth (indicators of P availability) increased with increasing moisture level. Phosphorus uptake and rice-shoot growth were greatst when the soil or P treated cellulose were water-saturated. These data indicate that increased soil P availability upon flooding can be attributed to an increase in the diffusivity factor.Paper Number 4532 of the Journal Series of the North Carolina Agricultural Experiment Station.Paper Number 4532 of the Journal Series of the North Carolina Agricultural Experiment Station.     

Improving phosphorus availability in two upland soils of Vietnam using Tithonia diversifolia H.

Phosphorus was added to two acidic upland soils (a Cambisol and a Ferralsol) at two rates (9 mg P kg⁻¹ and 145 mg P kg⁻¹) either in an inorganic P form (KH₂PO₄) or as a green manure (Tithonia diversifolia H. at 2.5 g kg⁻¹ and 40 g kg⁻¹). The effect of P source on the chemical availability of P was assessed in an incubation experiment by measuring resin extractable P, soluble molybdate reactive (DMR-P) and unreactive P (DMU-P). Soil pH and extractable Al were monitored during the incubation period of 49 days. Green manure addition caused an immediate and sustained increase in soil pH and an immediate and sustained decrease in extractable Al. Labile P (resin P + DMR-P + DMU-P) was increased more by P added as a green manure than when added in inorganic form in one soil (Ferralsol), while it decreased or did not differ in the other one (Cambisol). In both soils, the concentrations of soluble DMU-P were frequently higher where Tithonia had been added. The effects of green manure amendment on physical factors governing the phosphorus supply through diffusive transport were also investigated. Aggregate size distribution was substantially changed by green manure amendment due to a shift in the percentage of microaggregates (<250 μm in diameter) to larger sizes. Changes in soil aggregation as a consequence of green manure amendment led to a reduction in specific surface area (SSA) of the whole soil. Coupled with the large increase in effective cation exchange capacity caused by green manure amendment in both soils, and the decrease in SSA, there was an increase in the net negative surface charge density in both soils. In summary, at a large addition rate – and in addition to the well-known effect derived from the extra supply in P, green manure amendment may improve the chemical availability and diffusive supply of P through the following mechanisms: (i) an increase in soil pH increasing the solubility of phosphate sources; (ii) a decrease in extractable Al reducing the fixation of added P; (iii) increased macro-aggregation and reduced specific surface area and porosity leading to fewer sorption sites for P and hence enhanced diffusion rates; and (iv) increased negative charges and reduced positive charges at the soil surface resulting in a net increase in repulsive force for P. The induced changes in most measured soil properties were smaller in the Ferralsol than in the Cambisol. This revised version was published online in June 2005 with a corrected article title.     

Relation of solute and sorbed boron to the boron hazard in irrigation water

Summary The current criteria for evaluating the boron (B) hazard of irrigation water for specified crops are based on the concentration of B in the irrigation water without consideration of soil properties or the leaching fraction. Experiments were conducted to determine the influence of B sorption capacity on plant uptake of B at rates of 0.1, 2.5, 5.0 and 10.0 ppm B in the irrigation water with a leaching fraction of 0.5. A relatively B sensitive crop, oats (Avena sativa), was grown on four arid-region soils of varying B sorption capacities. The results show that B in solution rather than sorbed B influenced B toxicity. Contribution from the Department of Soils, Water and Engineering, The University of Arizona, Tucson, Arizona 85721. Arizona Agricultural Experiment Station No. 2508. Research Associates and Associate Professor, respectively. The senior author is currently at the Department of Soils and Irrigation, American University of Beirut Beirut, Lebanon.     

氮素形态对不同专用型小麦生育后期光合特性及穗部性状的影响

采用盆栽的方法研究了氮素形态对不同专用型小麦生育后期光合特性及穗部性状的影响,结果表明：强筋型豫麦34在硝态氮处理下,生育后期衰老延缓,旗叶保持较高的光合速率、PSI活性(Fv／Fo)、PS Ⅱ最大光能转换效率(Fv／Fm)、实际光化学效率(фPSⅡ)和光化学猝灭系数(qP)较高,非光化学猝灭系数(qN)降低,发生光抑制的可能性较小,穗部性状较好,穗粒重最高。中筋型豫麦49和弱筋型豫麦50在酰胺态氮处理下,光合和荧光参数较优,穗粒重较高,有利于实现高产。     

Effects of soil water stress and twospotted spider mites on net photosynthesis and transpiration of apple leaves

Soil water stress and twospotted spider mites (Tetranychus urticae Koch) were tested for their influence on the content and activity of leaves of greenhouse grown Delicious apple trees. Soil water stress caused reductions in net photosynthesis (Pn), transpiration (Tr), and shoot growth. Leaf water potential was decreased by both water stress and mite feeding. Feeding of 15 adult mites/leaf for 28 days resulted in a 16% reduction in Pn while an initial population of 10 mites leaf/left to develop for 20 days reduced Pn by 27%. Mite feeding reduced leaf nitrogen and non-structural carbohydrate levels when sampled 20 days after placement on the leaf. There was no interaction between the changed physiology of the leaf due to soil water stress and mite feeding.Approved for publication as Journal Article No. 111-80 of the Ohio Agricultural Research and Development Center, Wooster, OH 44691.Associate Professor and Professor, Departments of Horticulture and Entomology, respectively.     

Phosphorus sorption isotherm for evaluating phosphorus requirements of lettuce at five temperature regimes

A study was conducted to determine the influence of temperature on solubility and subsequent availability of P to plants. Phosphorus sorption curves were used to fertilize the soil with six P rates corresponding to initial sorption equilibrium solution P levels in the range of 0.03 to 0.72 ppm. Yield response to P measured for temperatures was in controlled environment chambers. Growth temperatures ranged 12.7°C to 29.4°C. Sorption of added P and desorption of sorbed P increased with increase in temperature. Yields of lettuce increased with the increased sorption equilibrium solution P levels at all the temperatures. Initial sorption-equilibrium solution P levels necessary for 95% yield had to be increased from 0.20 to 0.64 ppm when temperature was lowered from 29.4° C to 12.7°C. Desorption-equilibrium solution P levels for 95% yield were nearly constant at all temperatures. The log of initial sorption equilibrium solution P as a function of temperature for 95% yield was linear between 17.2°C and 29.4°C. Comparison of the data for 95% yield in solution cultures showed that critical nutrient solution P levels were very close to the desorption equilibrium P levels for 95% yield of plants grown in soil at similar temperatures. Relative yields of lettuce and desorption equilibrium solution P levels showed the same trend to changes in temperature. The study suggests that the major role of temperature on P uptake between 17.2°C and 29.4°C is due to desorption of P from the soil. Physiological influences of temperature on plant growth and consequent P requirement play a minor role.Contribution from the Department of Plant and Soil Sciences, University of Idaho, Moscow. Approved for publication by the Director of the Agricultural Experiment Station as Research Paper No.74740. Presented before Div. S-4, Western Regional Meeting, ASA, Irvine, Calif., June 19, 1974. Part of senior author's Ph.D. dissertation.     

The effects of root temperature and Ca supply on the growth and transpiration of cotton seedlings (Gossypium hirsutum,L.)

Summary Cotton seedlings were germinated in either tap water or a CaSO₄ solution and then grown for two days in nutrient solutions containing 0.1, 1.0, or 10.0 me Ca/1. They were then transferred to cultures having the same Ca variables and the roots subjected to temperatures of 26, 18, 15 and 12°C for four days. The fresh weight of all plant parts and leaf area increased with increasing root temperatures and with increasing Ca levels, the effect of Ca being most pronounced at the higher temperatures. The dry weight was increased by increasing root temperature; the effect of Ca was rather small. Water use increased with increasing temperature and was higher for the lowest Ca level than for the higher levels. The results emphasize the overriding effect of low temperature on water uptake. Calcium had little effect on the growth depression resulting from low root temperatures. Joint contribution from the Agronomy Department, Mississippi Agricultural Experiment Station, State College and the Soil Science Department, North Carolina Agricultural Experiment Station, Raleigh. Published with the approval of the Directors of Research as Journal Contribution No.1530 and Paper No.2389 of the Journal Series, respectively. This is a report of research conducted while the author was on sabbatical leave at North Carolina State University, February 1–September 10, 1965.