Phosphate-deficient Soil Research Articles

Plant Growth-promoting Activities of Penicillium sp. NAUSF2 Ameliorate Vigna radiata Salinity Stress in Phosphate-deficient Saline Soil

Plant Growth-promoting Activities of Penicillium sp. NAUSF2 Ameliorate Vigna radiata Salinity Stress in Phosphate-deficient Saline Soil

The Ability of Streptomyces spp. Isolated from Iranian Soil to Solubilize Rock Phosphate

Many agricultural soils are deficient in plant available phosphate and hence not able to sustain optimal crop productivity. The problem is due to the ability of many soils to fix phosphate in a wide range of soil pH and ecological conditions. There is a need to search for more environmental friendly alternatives to improve soil fertility and crop production in phosphate deficient soil. The aim of this study was to isolate, screen, and characterize phosphate solubilizing actinomycetes found in different types of soil with varied pH from various sites in Iran. Phosphate solubilizing ability of the actinomycetes was evaluated both on modified Pikovskaya's (PVK) agar and into broth media containing Christmas Island Rock Phosphate (CIRP). The abilities of each isolate to solubilize phosphorus was evaluated from day 1 to day 14 after inoculation. Streptomyces spp. were identified morphologically under scanning electron microscope (SEM). About 31% (22/70) isolates of actinomycetes were found to have the ability to solubilize (CIRP). Isolates IA15 and IA31 showed high solubilizing index (SI) on agar medium whereas isolates IA61, IA59, IA38, IA35, and IA31 were determined to have high CIRP solubilizing ability in broth medium. Isolates IA11, IA31, IA10, and IA61 had high pH decrease in broth medium after 14 days of inoculation. A gradual decrease in pH was observed over a 14 day period of incubation, suggesting a slow release of phosphate from CIRP. The mechanism of solubilization was related to pH decrease in broth medium. In general, majority of phosphate solubilizing actinomycetes revealed superior ability to solubilize CIRP. Key words: rock phosphate; solubilizing phosphate; Streptomyces spp

Nitrogen mineralization as a result of phosphorus supplementation in long-term phosphate deficient soil

In red soil (with pH ≤6), high phosphorus deficiency hinders soil carbon and nitrogen cycling, and thus reduces plant nutrient use efficiency in terrestrial system. In this study, inorganic phosphate addition could accelerate litter nitrogen release and soil nitrogen mineralization through stimulating soil urease and dehydrogenase enzymatic activities. The abundance and composition of mineral N transforming genes with three levels of phosphate were assayed using quantitative real-time PCR and denaturing gradient gel electrophoresis. Soil ammonia-oxidizing bacteria (AOB) were sensitive to the inorganic phosphate supplementation level: P addition at levels lower than 25mgkg−1 accelerated soil nitrification via increased AOB activity. However, as the P level reached 50mgkg−1, higher levels of soil ammonium nitrogen from litter decomposition remained in the soil through a decrease in the activities of N-mineralization enzymes and the stabilization of the AOB community structure. Our results emphasize the importance of reasonable concentrations of P fertilization for accelerating litter N mineralization and avoiding N leaching in plant litter-amended soil where phosphate is deficient.

N–P–K ratio affects exudation of germination stimulants and resistance of tobacco seedlings to broomrapes

Nutrient deficiency is known to aggravate the infestation of broomrape in a number of plant species. This effect is hypothesised to result from the promotion of the release of germination stimulants from the roots of the host plant. In the present study, three experiments (hydroponic culture, Petri dish culture and soil culture) were conducted to investigate the effects of macro-nutrient ratios on the production and release of germination stimulants and the resistance of host tobacco cultivars to broomrapes. The hydroponic culture study showed that nitrogen/phosphate deficiency and potassium excess increased the germination-inducing activity of root exudates on Phelipanche aegyptiaca and Orobanche cumana seeds, with two tobacco cultivars showing different responses to nutrient ratios. The production of germination stimulants was significantly increased under nitrogen- and phosphate-deficient soil conditions. In the Petri dish study, increased vulnerability to P. aegyptiaca infection was observed in RG tobacco seedlings under nitrogen- and potassium-deficient conditions and in WF tobacco seedlings under nitrogen- and phosphate-deficient conditions. The results showed that macro-nutrient ratios can affect both the exudation of germination stimulants and the resistance of tobacco seedlings. Finally, we suggest that the classification of the resistance or tolerance of host species should fully consider the nutritional conditions of cultivation and the strategy of fertilisation in terms of the potential control of parasitic weeds prior to the identification of the key mechanism of parasite resistance.

Ectomycorrhizal diversity enhances growth and nitrogen fixation of Acacia mangium seedlings

Increasing interest has been given so far to the role of mycorrhizal symbiosis on plant diversity and ecosystem productivity. However much remains unknown about the effect of ectomycorrhizal fungal diversity on plant growth and rhizobial symbiosis. The purpose of this study is to investigate the influence of ectomycorrhizal diversity on root nodulation and plant nutrient uptake during plant growth. A gradient of ectomycorrhizal diversity was created (ranged from one to six fungal isolates) on Australian Acacia (Acacia mangium) seedlings grown on a phosphate-deficient soil in controlled conditions. The results clearly show (i) an enhancement of A. mangium growth due to ectomycorrhizal fungal inoculation, (ii) as well as significant effects of increasing ectomycorhizal diversity and soil ectomycorrhizal mycelium density on whole plant biomass and plant nutrient uptake. They also reveal an effect of ectomycorrhizal diversity effect on the functioning of the nitrogen-fixing symbiosis. These results emphasize the need to manage soil ectomycorrhizal potential (abundance and diversity of ectomycorrhizal mycelium) in forest management practices in order to optimize N2 fixation and seedling growth, leading thus to dramatic improvements in outplanting performances with fast-growing tree legumes on various reafforestation sites, more particularly in tropical and Mediterranean areas.

Isolation of a starch utilizing, phosphate solubilizing fungus on buffered medium and its characterization

A phosphate solubilizing fungus, Paecilomyces marquandii AA1 was isolated from phosphate deficient soil on Pikovskaya’s medium buffered with Tris–HCl pH 8. The organism was identified on the basis of morphological characterization and by sequencing of 18S rRNA gene. The organism could release phosphate from both buffered and unbuffered medium and solubilized rock phosphates from various places. The effect of concentration of ore, temperature, carbon and nitrogen sources on solubilization of rock phosphate was studied. Ammonium salts were the best nitrogen source, followed by asparagine, sodium nitrate, potassium nitrate, urea and calcium nitrate in that order.

Growth responses of mycorrhizal and non-mycorrhizal tropical forage species to different levels of soil phosphate

Three tropical forage legumes, Stylosanthes capitata, Pueraria phaseoloides and Centrosema macrocarpum, and one grass, Brachiaria dictyoneura, were grown in a sterile phosphate deficient soil amended with soluble or rock phosphate at rates ranging from 0 to 400 mg kg-1 soil. The effects of inoculation with Glomus manihotis on mycorrhizal infection and plant growth were assessed. Early growth and nodulation of P. phaseoloides in soil with and without rock phosphate fertilizer were also determined. In the legumes, mycorrhizal infection was high at all P levels and sources, except for a significant decrease of infection in S. capitata at high levels of superphosphate. Plant growth was significantly increased by phosphate fertilizer and mycorrhizal inoculation. Mycorrhizal responses were more pronounced at low P levels with both P sources. In B. dictyoneura mycorrhizal infection was decreased with increasing additions of P. No effects of mycorrhizal inoculation (except with no added P) were observed. Growth and nodulation of P. phaseoloides were greatly stimulated by mycorrhizal inoculation.

Effects of lime and phosphate additions on changes in enzyme activities, microbial biomass and levels of extractable nitrogen, sulphur and phosphorus in an acid soil

The effects of adding lime and/or phosphate to an acid, phosphate-deficient soil on microbial activity, enzyme activities and levels of biomass and extractable N, S and P were studied under laboratory conditions. Following rewetting there was, as expected, an initial flush in microbial growth and activity, as shown by large increases in CO2 evolution, in levels of biomass N, S and P and by accumulation of extractable mineral N and sulphate in the soil. Following rewetting, additions of lime and phosphate further stimulated mineralization of C, N and S. In the first 4 weeks of incubation, the mineralized N accumulated in the soil as ammonium N and there was a concomitant rise in soil pH. After this initial period, nitrification increased substantially and soil pH decreased again. Additions of lime generally increased protease and sulphatase activities but decreased phosphatase activity. Additions of phosphate decreased the activities of all three enzymes. The positive effect of liming on protease and sulphatase activities persisted for the duration of the experiment while accumulation of mineral N and sulphate effectively ceased after about 4 weeks. Furthermore, although phosphate additions decreased the activities of protease and sulphatase they increased the accumulation of mineral N and sulphate. Thus, protease and sulphatase activities were not reliable indicators of the relative amounts of mineral N and sulphate accumulated in the soil during incubation. Some uncertainty surrounded the validity of biomass S and P values estimated by the chloroform fumigation technique because differing proportions of the sulphate and phosphate released from the lysed cells may have been extracted from the different treatments.

Infectivity and effectiveness of vesicular arbuscular mycorrhizal fungi: effect of inoculum type

Plants, inoculated with four vesicular arbuscular mycorrhizal (VAM) fungi (Glomus fasciculatus, G. monospovus and two isolates of Acaulospova laevis), were grown from 4 to 16 weeks, and the development of infection and spores was followed. Infected roots from pot cultures of different ages were used to examine the effect of mycorrhiza development on the infectivity of each fungus. The effectiveness of each fungus was assessed by measuring its ability to increase the growth of subterranean clover on a phosphate-deficient soil. For all fungi, the percentage of root length infected increased rapidly up to 10 weeks after sowing, and thereafter it either increased only slightly or decreased. Infectivity of root inocula increased with increasing percentage of root length infected in the inoculum for all fungi, except where large numbers of mature spores (24/g infected root) had been produced by one isolate of A. laevis. The infectivity of inoculum roots from pots containing mature spores of this isolate declined rapidly, although it was not decreased by the onset of sporulation by A. laevis. For all fungi, irrespective of the inoculum used, the fresh weight of tops of subterranean clover grown on a phosphate-deficient soil was very closely correlated with the percentage of its root length infected at an early stage of plant growth. That is, the effectiveness of the species of fungi examined at increasing phosphorus uptake into plants was related to the infectivity of the inoculum used.

BARLEY RESPONSE TO PHOSPHORUS FROM PHOSPHOLIPIDS AND NUCLEIC ACIDS

Barley responses in a phosphate-deficient soil to 50 μg P/g soil showed DNA and KH2PO4 similarly efficient at increasing dry matter and P content per unit biomass. Phosphatidylcholine increased P content but not dry matter. DNA and phosphatidylcholine induced unusual but dissimilar plant morphological effects.

Early detection of phosphate deficiency in plants

Abstract At 3, 7 and 10 days after planting, uptake of 32P‐ orthophosphate over 15 minutes by pine seedlings grown in phosphate deficient soil was 3.0 4.8 and 5.2 times that of seedlings growing in phosphate amended soil. At 4 days and 7 days uptake over 15 minutes by phosphate deficient wheat was 1.2 and 2.4 times that of plants grown in phosphate amended soil. A rapid, sensitive, very early bioassay of available soil phosphate is suggested.

A study of soil and fertilizer phosphorus intake by Barley plants, using Radioactive tracer technique

Abstract Introduction Phosphorus applied on a phosphate deficient soil, by increasing the root development of the plant, or by stimulating the soil microflora especially in the rhizosphere, may increase the amount of phosphorus which the plant takes up from the soil. This present paper is a report on a pot culture investigation of such an effect of added phosphorus.

On the Influence of Phosphate Application upon the Susceptibility to Blast Disease in Rice Plant

A pot experiment was made to determine the effect of phosphate application upon the infection of rice seedlings by blast fungus, Piricularia oryzae.The phosphate deficiency in the soil made the rice plant susceptible to rice-blast. But, the excess of phosphate over the necessary quantity for growth gave no protective effect from riceblast. So that the application of phosphatic fertilizer in the soil is effective to the protection from rice-blast in the phosphate deficient soil. but not effective in the phosphate abundant soil, The influence of phosphate deficiency of rice plant on the infection of rice-blast was intensified with the large supplies of nitrogen. As it is known that the phosphate unavailable under low temperature becomes available for plants with the increase of temperature in the field especially in the paddy field, the appication of phosphatic fertilizer acts effectively for the control of the said disease, under the lower temperature rather than under the higher temperature.

Prevention of mineral deficiency by soaking seed in nutrient solution

SUMMARYA method is described for economizing in the use of fertilizers on deficient soil by soaking the cereal seeds in nutrient solutions containing the deficient element at a sufficiently high concentration to supply a large part of the total requirements of the plants.The result of greatest potential practical importance was obtained on oats. Soaking oats in molecular tribasic potassium phosphate brought about an increase in yield from 17 to 25 cwt./acre (46 %) on phosphate-deficient soil at the cost of 13·6 lb./acre of the potassium phosphate (or 4·6 lb. P2O6) without the addition of any phosphate to the soil. There was a correspondingly large increase in the weight of straw. Nearly 75% of the P2O5 introduced in this way was recovered from the harvested grain. Sodium phosphate appears equally efficaceous for oats. Strikingly beneficial effects were also obtained on barley and wheat.

Studies on phosphate fixation in Scottish soils. I. The recovery of added phosphate from a soil of the acid igneous group

1. A long-term investigation consisting of field, pot and laboratory experiments has been commenced to study the extent, rate, nature and significance of phosphate fixation in north Scottish soils with the ultimate objects of improving fertilizer practice and standardizing methods for determining readily soluble phosphate.2. Quantities of a phosphate-deficient soil derived mainly from granitic drift were treated with incremental dressings of phosphate and exposed in earthenware pots in the open. The soil had an initial pH of 5·80 and a total phosphate content of 0·250% of which 28% is soluble in constant-boiling HCl solution.3. The recovery of added phosphate by different methods from samples taken after varying periods of exposure has been studied. Data are given for extractions with calcium lactate, acetic acid, potassium bisulphate, citric acid, magnesium bicarbonate, sodium hydroxide, hydrochloric acid, and chloride and sulphate solutions, together with pot experiments and determinations by the Neubauer and aspergillus methods.4. Complete recovery is approached only in strongly acid and strongly alkaline extracts, and about 25% of the added phosphate is very firmly bound by the soil. The solubility varies greatly with the pH of the extracts and is very low at pH values in the region of 5. At lower pH values, however, the nature and concentration of the anions present are also of considerable importance. The results indicate a high capacity for fixing phosphate in difficultly soluble form.