Soil Pot Experiments Research Articles

Plant growth promoting rhizobacteria for winter wheat

The association of winter wheat (Triticum aestivum L. cv. Norstar) with root-colonizing bacteria (rhizobacteria) was studied in potted soil experiments in the growth chamber. Thirty-six known bacteria, some of which have been reported to stimulate plant growth, and 75 isolates obtained from the rhizosphere of winter wheat were tested for their effects on plant growth and development in two different soils. Two known bacteria and 12 isolates stimulated growth of winter wheat. Of these, the most effective were nine isolates that significantly (P < 0.01) increased plant height, root and shoot biomass, and number of tillers. The plant growth promoting effects of isolates were different in the two soils. Three of these strains were tentatively classified as Pseudomonas aeruginosa, and two each as Pseudomonas cepacia, Pseudomonas fluorescens, and Pseudomonas putida. Some isolates induced significant increases in seedling emergence rates and (or) demonstrated antagonism in vitro against Rhizoctonia solani and Leptosphaeria maculans. These results demonstrate the potential use of plant growth promoting rhizobacteria as inoculants for winter wheat. Key words: pseudomonads, plant growth promoting rhizobacteria, winter wheat, rhizosphere, bacterial inoculants.

Occurrence and nature of mixed infections in nodules of field-grown soybeans (Glycine max)

Mixed infections of Bradyrhizobium japonicum strains in early and late nodules of four soybean cultivars were studied in a field soil. Nodule occupants were identified by immunofluorescence using serogroup specific antibodies prepared against B. japonicum strains USDA 110, USDA 123, and USDA 138. Double infection was determined directly by combined examination of the same microscopic field by fluorescence and phase contrast microscopy. Double strain occupancy was observed consistently, and its occurrence did not differ substantially in pouch, soil pot, and field experiments, ranging in incidence from 12% to 32%. No significant differences in the incidence or nature of double infection could be attributed to cultivar, seed inoculation, or plant maturity. Strains reactive to strain USDA 123-fluorescent antibody were dominant in both singly and doubly infected nodules irrespective of cultivar, plant age, or seed inoculation with strain USDA 110.

Isolierung und Effektivitätsprüfung von Rhizobium-Bakterien unter den Bedingungen der DDR

Summary Methods for the isolation and the effectivity-tests of Rhizobium bacteria under the conditions of the GDR were described. A test-system was succesful, in which Rhizobium strains, which gave a positive nitrogenase reaction, were tested several times with different soils in pot experiments. The yield effect (dry matter and raw protein), tested in long-term field experiments under different natural conditions, was the decisive criterium for the effectivity.

Growth responses to lime and fertilizers and critical concentrations in herbage of white clover in Scottish hill soils

AbstractThe responses in dry matter (DM) production and changes in nutrient concentration in the shoots of white clover (cv. New Zealand Grasslands Huia) to additions of lime, N, P, K and Mg were investigated in pot and field experiments in a deep peat soil and to additions of N, P, K in two other hill soils in pot experiments. DM production and nutrient concentrations were assessed also for perennial ryegrass in the field experiment. There was no response by white clover to N, but in all soils, and in particular a deep peat, production of shoot DM was increased greatly by lime, P and K, and slightly by Mg. Interactions between lime and P and between P and K were observed. Critical concentrations of nutrients (g kg−1) for white clover appeared to be about 2.0 for P, 10·15 for K and 20 for Ca. Herbage production and nutrient contents of ryegrass and white clover grown on a deep peat in the field suggests that critical concentrations may possibly help to diagnose the need fur maintenance fertilizer dressings.

The persistence and metabolism of isoproturon in soil

SummaryThe persistence of isoproturon in soil in pot experiments was the same whether or not the soil contained growing wheat (Triticum aestivum L.) plants, Panllel) work with radioactive isoproturon showed that the breakdown products were the same in the presence and absence of plants. Persistence in the field was reasonably well predicted by a simulation model using the results of laboratory incubation studies and field meteorological data.

Requirement for magnesium fertilization in Finland

More magnesium, on average, is removed annually from agricultural soils in Finland in yields (10 kg/ha) and through leaching (20kg/ha) than is replaced as fertilizers (4 kg/ha), manure (7 kg/ha) and as wet or dry depositions from the atmosphere (1 kg/ha). The amount of magnesium which is applied in assosiation with liming agents (at the most 25 kg/ha) has a decisie effect on the magnesium balance of the soils, although liming itself reduces those magnesium reserves of the soil which are extractable in neutral ammonium acetate(1 M) or in calcium chloride (0,01 M). The effect of two amounts of nitrogen and potassium fertilizers on the spring cereal and cultivated ley yields, on the magnesium uptake and nutrient contents of the yields, and the effect of liming on the magnesium status of the soil was studied using field, pot and incubation experiments in order to gain an estimate of requirement for magnesium fertilization. The results obtained with magnesium sulphate fertilizer in the same experiments were also used as an indicator of requirement for magnesium fertilization. The ammonium acetate (1 M, pH 7) extractable magnesium in the soil appeared to be the most important source of magnesium for the plants and the best indicator of requirement for magnesium fertilization. For the intensive cultivation of grassland crops, the soil should contain about 15 mg/100g of this type of magnesium. In pot experiments, the plants took up only small amounts of not extractable magnesium. Increasing the nitrogen fertilizer dosage (pot experiments, 4,5 l soil: N1=1500 mg, N2=3000mg N per year, field experiments: N1=50 kg/ha, N2=100 kg/ha N per year) generally brought about an increase in the magnesium uptake and in the magnesium content of the grasses. When the experiments were carried out using coarse mineral soils, the magnesium uptake and magnesium content of the plants decreased during the second and third year as the amount of nitrogen fertilizer increased. This was caused by the low magnesium content of the soil (pot experiments: below 12 mg/100 g soil in neutral ammonium acetate extractable magnesium, field experiments: below 100 mg/l soil in acid ammonium acetate extractable magnesium). In these soils, magnesium fertilization (200 mg Mg for 4,5 l soil per year or 57 kg/ha per year) appeared to have a positive effect on the supply of magnesium to the plants. The heavy clay and sandy clays used in the pot experiment did not require magnesium fertilization. The magnesium in silty clays, which contain a high proportion of the silt fraction (0,02—0,2 mm), may be liberated too slowly for intensively cultivated grasses and it may be necessary to give additional magnesium as fertilizer. Increasing the potassium fertilizer level from 60 kg/ha to 240 kg/ha K per year significantly decreased the magnesium content of the plants. Judging by the quality of the crops, a high potassium fertilizer level appeared to increase the requirement for magnesium fertilization. In the case of muddy very finesand the yield and magnesium uptake of timothy decreased with an increase in the amount of potassium applied. Liming (90, 180 or 360 mg/100g soil Ca as CaCO3) decreased the amount of neutral ammonium acetate extractable magnesium, in seven mineral soils out of nine, by 2—24 % in comparison to the magnesium content of unlimed soils. Part of the fertilizer magnesium became not extractable, too.

Cellulose xanthate as a soil conditioner: Laboratory experiments

AbstractCellulose xanthate was found to be effective in reducing the strength of a crust formed under standard laboratory conditions on all soils tested, including some known to be unresponsive to conditioning by poly(vinyl alcohol). Suitable application rates were 12.5 or 25 kg (of cellulose) ha−1, as a 1% solution. It was more effective, weight for weight, than PVA or Natrosol 250 HHR. Whereas germination of seeds was either partially or completely inhibited by direct contact with 1% cellulose xanthate solution, even when its pH was adjusted with orthophosphoric acid from the initial 13.2 to 6.5, application of cellulose xanthate as a spray to the surface of the soil in pot experiments did not depress emergence of seedlings of lettuce, cabbage, onions or chicory.

The Bouma-Janssen method as a tool for the evaluation of macro and micro nutrient status of cotton soils from Nepal

The double pot technique called Bouma-Janssen method, was used to evaluate the nutrient status of three soils of the UNDP Cotton Project, Nepal. In all three soils, N deficiency could be assessed both by soil analysis and pot experiments using a double pot technique. P- and K-deficiency, which were expected from soil analysis, could be confirmed in two of the three soils. The double pot experimental technique proved to be suitable for the rapid evaluation of the macro nutrient status of cotton soils under circumstances where no laboratory facilities are available. More studies are needed in relation to micro nutrients.

Control of Ophiobolus patch in Agrostis turf using avirulent fungi and take‐all suppressive soils in pot experiments

SUMMARYThe incorporation of avirulent fungi such as Gaeumannomyces graminis var. graminis, an avirulent isolate of G. graminis var. tritici, a Phialophora sp. with lobed hyphopodia synonymous with Phialophora radiciola var. radicicola sensu Deacon and P. radicicola var. graminicola at the time of seeding Agrostis turf in pots of sterilised soil completely controlled Ophiobolus patch disease. The addition of a 5 mm layer of take‐all suppressive (TAS) soils, artifically developed by the repeated addition of live mycelium of the varieties avenae, tritici and graminis of G. graminis to soil, controlled the disease to a lesser extent. However, a 20 mm layer of a TAS soil developed from live mycelium of G. g. avenae almost completely suppressed the disease. A survey of 66 golf and bowling greens in four states of Australia showed that P. r. graminicola was the most prevalent avirulent fungus.

Rhizosphere relationships of subterranean clover. I. Interactions between strains of Rhizobium trifolii.

A study was made of a number of effective and ineffective strains of Rhizobium trifolii in association with subterranean clover (Trifolium subterraneum L.), variety Bacchus Marsh. Where these were inoculated singly into sterilized soils in pot experiments conducted in the greenhouse, typical effective, ineffective, or intermediate plant reactions were obtained. Where more than one strain was inoculated, competition between strains took place and was reflected in nodule pattern and plant reaction. Some strains consistently failed to produce appreciable nodules in the presence of other rhizobia, some showed modification to varying degrees, and some were unaffected. Such behaviour was found to be closely linked with the ability of the strain to proliferate in the rhizosphere of the host plant, and placement of inoculum was shown to influence plant reaction. The concept of "incursion" as a property of a rhizobial strain is suggested. An incursive strain is one able to migrate from the initial site of inoculation and establish an adequate population in the root zone of the susceptible host despite the presence of active elements of the indigenous microflora and microfauna, including antagonistic and predatory forms. The property of incursion is independent of considerations of efficiency of nitrogen fixation or virulence for the host plant. Strains of rhizobia which are poorly incursive may fail to infect the host upon which they have been inoculated if subject to competition from indigenous rhizobia already established in the soil. The necessity of assessing properties of virulence and incursion as well as efficiency of nitrogen fixation in selecting rhizobia for purposes of commercial inoculation is stressed, and the methods of making such tests are discussed.

Contribuição ao estudo do «vermelhão» do algodoeiro (Gossipium herbaceum)

During the years 1948, 1949 and 1951 a disease occurred in the cotton crops of the state of S. Paulo Brazil (S. Am.), which caused a severe drop in yields. The abnormality was characterized by a typical reddish - purple color of the leaves, being by this reason, called vermelhao, that is, reddening of the cotton plant. The disease was associated with a dry season. Among the several hypotheses raised to explain the causes of the disease were: insect attack, potassium deficiency - where from the name hunger was also given -, and magnesium deficiency: In order to study the problem the Department of Agricultural Chemistry of the College of Agriculture of the University of Sao Paulo, at Piracicaba, carried out a series of experiments as follows: 1. pot experiments in which soil of one of the affected regions was used (terra roxa, a red-brownish soil derived from basalt); 2. pot-soil experiments varying the moisture supplied; 3. sand culture experiments omitting certain elements from the nutrient solutions; 4. field plot experiments, conducted on a sandy soil; three different varieties were employed: Texas, Express, and I.A. 817; magnesium was applied either as sulfate or dolomitic limestone. All the experiments were completed with suitable chemical analyses. The results can be summarized as follows: 1. in the first trial, the not properly manured pots (minus Mg), symptoms were registered which were similar to the symptoms observed in the field; it was possible to establish some differences among three different types of reddening: due to lack of K in the mixed fertilizers used, the characteristic cotton rust made its appearance, the red color in the leaves of the minus Mg plants was all alike that described in the current literature as a symptom of Mg-deficiency; in all the treatments ocurred a yellow-reddish color in the leaves associated with the latest stages of maturity; 2. in the second experiment it was verified that when the plants in the pots with soil were kept 75 per cent of the water holding capacity, no symptom of deficiency showed up; was true even for the plants not receiving neither K nor Mg; however, plants supplied with only 25 per cent of the water holding capacity showed, respectively, cotton rust in the minus K treatment and the red purplish color in the minus Mg series; 3. the sand culture experiment confirmed lack of Mg as the cause of vermelhao, being potash deficiency the responsible for cotton rust; 4. in the field experiment, variety LA. 817 revealed to be the most sensitive to when Mg was omitted from the fertilizers; symptoms of K deficiency appeared when no K was supplied; both magnesium sulfate and dolomitic limestone proved to be equally effective in the control of vermelhao; 5. the analyses of material collected both in the field as well in the pots revealed that leaf petiole in the most reliable part to indicate the K and Mg status of the plant; the variation in Mg content suffered by the plants showing different stages of vermelhao was, quantitatively, at least as large as that in K content, however when one deals with K deficient plants, that is, plants showing the typical rust, no variation occurred in the Mg content, whereas K in the dry mater dropped from more than 1 per cent to less than half per cent. Then, the following general conclusions can be drawn: 1. Mg deficiency is the cause of of cotton crops; 2. K deficiency also occurred, but in a lesser degree; 3. the climate conditions - especially the lack of rain influenced the soil dynamic of K, and especially Mg, bringing a severe reduction in their assimilability; 4. the disease can be easily controlled upon additions either of magnesium sulfate or dolomitic limestone.