Partial Sterilisation Of Soil Research Articles

Recovery of soil microbial community structure and activity following partial sterilization with gamma irradiation

Sterilization (partial or full) is one of the most fundamental tools for studying the ecological roles of soil biota and notably soil fauna, but there is a lack of knowledge on how these techniques affect other soil- inhabiting micro-organisms (non-target), and on their recovery after sterilization. We investigated the effect of a partial soil sterilization with gamma (γ) irradiation (target dose of 6 kGy, proven to selectively remove the entire nematode community and higher soil fauna) on the soil microbial community and its recovery in a microcosm experiment during 12 weeks. We specifically studied the effects, following partial sterilization, of recovery time (4 sampling events after 1, 4, 8 and 12 weeks) on the microbial activity (activities of dehydrogenase and β-glucosidase, and nitrification), microbial biomass and microbial community composition (using PLFA analysis), in two soils of contrasting texture (silt loam and loamy sand). We also studied whether inoculation of finely sieved and homogenized soil powder (SP) from these same soils (containing prokaryotes, fungi and protists, but no metazoan organisms) would stimulate the microbial recovery process. Dehydrogenase activity was strongly reduced by γ-irradiation in the silt loam (and SP did not stimulate its recovery) but not in the loamy sand, whereas there was no effect of γ-irradiation on β-glucosidase activity in either soil. Nitrification was strongly affected in the loamy sand and did not yet recover by the end of the incubation (week12), but the SP inoculation brought nitrification to the level of the unirradiated control by week4. Surprisingly, nitrification rate was not affected by γ-irradiation in the silt loam. The factors “recovery time”, “irradiation” and “SP inoculation” affected the microbial community composition (based on PLFA), but the direction of these changes did not seem to follow a clear pattern. These results urge to carefully consider the re-establishment of microbial activity in studies on the roles of micro- and mesofauna following selective sterilization, even after several months. Also, SP inoculation can be a useful way to stimulate the recovery of the nitrification process, which would be crucial in studies of the role of soil fauna in N dynamics.

Sour Orange (Citrus Aurantium L.) Growth is Strongly Mycorrhizal Dependent in Terms of Phosphorus (P) Nutrition Rather than Zinc (Zn)

ABSTRACTThe partial sterilization of soil eliminates useful microorganisms, resulting in the reduced growth of mycorrhizae-dependent citrus plants, which are often unresponsive to the application of fertilizer. Research was conducted to test the hypothesis that indigenous mycorrhizae (IM) inoculation is as efficient as selected mycorrhizal inoculation under sterile and non-sterile soil conditions. Rhizophagus clarus and indigenous mycorrhiza spores, isolated from citrus orchards, were used as arbuscular mycorrhizae fungi under greenhouse conditions with sterile and non-sterile Çanakçi series (Typic xerofluvent) soils with low phosphorus (P) fertility. Different P (0 and 100 mg kg−1) and zinc (Zn) (0, 5 and 10 mg kg−1) concentrations were used at the start of the experiments. The shoot, root dry weight (RDW), root colonization, and P, Zn, iron (Fe), copper (Cu) and manganese (Mn) concentrations of the shoot were determined; mycorrhizae dependency (MD) was also calculated.The results indicate that R. clarus and indigenous mycorrhiza in sterile and non-sterile soil conditions considerably increased the growth of citrus plants. Owing to existing beneficial indigenous rhizosphere microorganisms, citrus plant growth without inoculation was better in non-sterile soils than in the sterile soils. In non-sterilized soil, the plant growth parameters of R. clarus-inoculated soils were higher than those of indigenous mycorrhiza-inoculated soils. Mycorrhizae infection increased certain citrus plant growth parameters, such as root infection, biomass and nutrient uptake (P, Zn, Fe, Mn and Cu). In sterile soil, the addition of up to 5 mg kg−1 soil Zn and the inoculation of R. clarus significantly increased plant growth; inoculation with indigenous mycorrhiza produced more dry weight upon the addition of up to 100 mg kg−1 phosphorus pentoxide (P2O5). Under sterile soil conditions, without considering fertilizer addition, MD was found to be higher than that of non-sterile soils. In general, the contribution of the indigenous soil spores is significant. However, indigenous soil mycorrhizae may need to be managed for better efficiency in increasing plant growth and nutrient uptake. The major finding was that the inoculation of citrus seedlings with mycorrhiza is necessary under both sterilized and non-sterilized soil conditions.

Control of acarid mites Tyrophagus similis Volgin by soil sterilization

Effects of partial soil sterilization for Tyrophagus similis Volgin were investigated. Soil sterilization treatments by solar heat, hot water, steam, and soil reduction were effective. Nevertheless, a few acarid mites survived in some cases in the greenhouses because of uneven heat treatment, or on the outskirts of greenhouses, and untreated areas. For that reason, we can not expect a lasting effect over a long period. It is not desirable that these soil sterilization methods be used in early summer. Short-term steam disinfection in spring or autumn will probably suppress acarid mite infestation. Use of this method will spread because of its economy and practicality if applied for prevention before mites' reproduction or as an emergency control measure after their outbreak.

The performance characteristics of the sterilization of raised beds by steam applied from the surface

The partial sterilization of soil in raised beds in glasshouses is frequently carried out by a method known as sheet steaming. Some measurements taken during the routine steaming of six beds show that the depth of heat penetration by this method is variable. At a depth of 2 in (51 mm) the process was consistent, but at a depth of 6 in (152 mm) the process was less reliable, there being a reduced rate of heating and lower soil temperatures. During the 5–6 h duration of the treatment up to 2 1 2 times more steam was supplied than would be required with a steam injection method such as Hoddesdon pipes. An initial steam supply rate of at least 3 lb h −1ft −2 (4·07 g s −1 m −2) of bed should be allowed.

Gaseous Loss of Ammonia from Prilled Urea Applied to Slash Pine

AbstractGaseous loss of NH3 from prilled urea, surface applied at 100 kg N/ha to undisturbed dry organic residue over moist soil under slash pine (Pinus elliottii Engelm. var. elliottii), averaged 4% in 7 days as compared with 2% for an area that was control‐burned 5 weeks previous, and 5% for one from which loose debris had been removed. This was approximately equivalent to removal by burning. Residual urea recovery of 41% for the burned area as compared with 16 and 12% for the undisturbed and cleaned areas, indicated urease inactivation and partial soil sterilization by burning. Where urea had been applied to moist undisturbed organic residue, hydrolysis approached completion in 3 days and was accompanied by 9% N loss as NH3. Various types and orientations of needle‐bearing portions of branches of slash pine were submitted to a 75–100 cm drop of prilled urea at 100 kg N/ha. From 0.32–0.87 g of pellets were retained per meter of branch. Aspiration tests under typical alternating night and day humidities and native urease activity showed only 3% loss of this retained urea‐N as NH3 in 4 days. At 8 days an average of 52% of the initially retained N was still dilute‐acid soluble from macerated bark plus needle stubs, with a ratio of seven parts urea N to three parts NH4+‐N. The remainder, except for the small gaseous loss, probably was assimilated.

Influence of partial soil sterilization on nodulation of alfalfa

Influence of partial soil sterilization on nodulation of alfalfa

Performance characteristics of partial sterilization of soil by steam applied from the surface and by buried pipes

An investigation into the performance characteristics of two basically different methods of partial sterilization of soil is described. When steam was applied to the cultivated soil surface beneath a sheet weighted down at its edges with and without a net staked over it, the heat penetration downwards was limited by the depth of cultivation, and the general soil condition appeared to be quite critical. Because of variations in these factors, no difference was observed between an unnetted and a netted sheet. When the steam was applied below the soil surface from perforated pipes buried as the soil was dug and from clay tile drains previously buried and which were intended to remain in position for several years, it was found that all the soil within a band of 2½–3 ft width above the buried pipes was heated.

Fumigation of potato soils in Washington

Partial soil sterilization with Picfume, Vapam, Vorlex, Terraclor, Telone and combinations of Telone and Picfume have been included in studies for one or more years between 1960 and 1963. All the chemicals tested except Terraclor resulted in yield increases statistically and economically larger than the yields of potatoes produced on the untreated check plots. Partially sterilizing the soil in the fall resulted in large increases in yield of potatoes the following year. The effect of the partial sterilization of the soil lasted for at least two years. The causes for the increases in yield are not known. “Early dying” disease caused byVerticillium alboatrum was known to be present, but increases in yield also resulted from the use of Telone which is predominantly a nematocide. Pathogenic nema were few in number. A combination of Picfume and Telone, economically feasible in Washington, produced large yield increases over a two-year period and did not produce an off flavor in the potatoes when applied in the fall.

EFFECT OF AMMONIUM NITRATE AND LIME ON GERMINATION AND EARLY GROWTH OF PINUS CARIBAEA

SUMMARY Depressive effects of nitrogen (N) salts on germination and survival of Caribbean pine (Pinus caribaea Mor.) were investigated in the glasshouse by following changes in mineral soil N after the application of lime and fertilizers. The effect of partial soil sterilization was also studied. Immobilization and subsequent nitrification of ammonium nitrate was greatly stimulated by liming. Germination and survival declined as the soil nitrate level was raised, apparently because of increased pre—and post-emergence damping-off by Fusarium spp. Seedling yield at 20 weeks was reduced by high soil nitrate levels, but this effect was reversed at 31 weeks except for the highest level of nitrate. The percentage of total N in seedling tissues was closely correlated with the concentration of soil nitrate. The effects of partial soil sterilization on plant behaviour were slight compared to those of ammonium nitrate and lime.

Rôle of blue-green algae and different methods of partial soil sterilization on rice yield

Results of experiments during three consecutive seasons on the role of blue-green algae in combination with partial soil sterilization and chemical nutrients indicate high responses to algae inoculation and a fertility build-up of the soil. It is also seen that blue-green algae tend to produce better response in soils which are poor.

The Persistence of Trithion, an Organophosphorus Insecticide, In Soil1

Studies were conducted to determine the persistence of Trithion® (S-(p-chlorophenylthio)methyl 0,0-diethyl phosphorodithioate) in there California loamy soils. The influence of partial soil sterilization, fumigation, Trithion formulation, and dosage on the rate of degradation in soil was evaluated. Trithion residues were determined by a cholinesterase inhibition method. The persistence of Trithion increased significantly in soil which was autoclaved or fumigated with Vapam® (sodium N-methyl dithiocarbamate). Its longer persistence in autoclaved and fumigated soil apparently resulted from a partial destruction of the soil microorganisms which may prevent degradation of Trithion.

The inhibition of hatching of potato root eelworm (Heterodera rostochiensis Woll.) in partially sterilized soil.

Experiments on the hatching of Heterodera rostochiensis have shown that the addition of ammonium carbonate to potato root water markedly inhibits hatching when the concentration of ammonia introduced is approximately 100 p.p.m. The strong acid salts of ammonia in equivalent amounts have no such inhibitory effect.These observations are linked with experiments on the effect of partial sterilization of soil on the hatching of H. rostochiensis, and it is demonstrated that delay of hatching in such soils is only effective so long as the ammonia concentration within the soil is maintained at a sufficiently high level.

The Partial Sterilization of Soil by Chloropicrin

The Partial Sterilization of Soil by Chloropicrin

Partial sterilisation of soil by antiseptics

1. Quantitative determinations have been made of the effect on soil protozoa and bacteria of various antiseptic substances, including benzene and its homologues and derivatives, carbon disulphide, ammonia, formaldehyde and chlorpicrin. Ammonia and nitrates were determined at the same time in many cases. The effect on fungi, eelworm, etc., was also determined roughly.2. It was found that nearly all the substances disappeared from the soil fairly quickly and at the same time the numbers of bacteria fluctuated. The usual march of events was that the bacteria were reduced in number for the first few days, then rose to a maximum and finally fell slowly towards normal. The whole fall was sometimes very slow and the whole process was much slower in field soil than in the richer, lighter and better aerated greenhouse soils.3. Aeration was found to have great influence on the rapidity of the changes.4. The increase of the bacteria during the early days of an experiment varied in the same direction as the molecular weights and heats of combustion of the antiseptics and is attributed to the latter property. Naphthalene, for instance, which has a large heat of combustion, caused enormous rises, while benzene with its lower heat caused smaller rises.5. This rise was independent of the effect of the substance on the protozoa. Both naphthalene and toluene in large doses cause high rises; the first has no effect on the protozoa, while the latter kills all amoebae and ciliates.6. Similar results were obtained when the experiments were made on soils already free from protozoa, such as a field soil which had been in bottle for 76 years, soil in which they had been killed by steaming, and soil in which they had been killed by antiseptics. If the protozoa were killed by the use of a strong dose of a suitable antiseptic and the soil were then set aside for a long period, a second dose caused an even greater rise than the first.7. It is therefore concluded that the rise in the number of the bacteria is largely due to the feeding effect of the antiseptic on the bacteria and not only to the destruction of the protozoa, and that the increased fertility observed by Russell and Hutchinson is to be attributed in large measure to the activity of the greater bacterial population in breaking down the organic matter of the soil. Bacterial rises following treatment with lime or steam are similarly caused in part by the preparation of the plant residues.8. Aliphatic compounds cause quicker but smaller rises than those of aromatic series.9. The introduction of a CH3 group into the benzene ring lessens toxicity to soil organisms, while a single Cl or nitro-group increases both toxicity and stability in the soil.

Investigations on protozoa in relation to the factor limiting bacterial activity in soil

In the course of my work on soil protozoa particularly in relation to the question of the partial sterilisation of soil, I had occasion to work with some of the old stored soils kept at the Rothamsted Experimental Station, Haependen, at which laboratory the work here recorded was commenced. These soils are remarkable for the length of time they have been stored, 67 years being the longest period, and for the fact that in many cases the original samples put up in large bottles have remained untouched since the day on which they were bottled. Preliminary cultures of some of these soils in hay-infusion were begun in 1912 to ascertain the character of the protozoan fauna, if such still persisted in them. From these cultures it was found that in a mixed sample from Broadbalk, bottled in 1846 and containing about 3 per cent. of water by weight, no protozoa were present, whilst in another mixed sample taken from six bottles of Barnfield soil, put up in 1870 and containing about 10 per cent. of water by weight, amœbæ and flagellates but no ciliates were present.

Partial Sterilisation of Soil by Volatile and Non-Volatile Antiseptics

1. The characteristics of true partial sterilisation have been found to be common to a large number of antiseptics and are(a) An initial decrease in the numbers of bacteria followed by a large sustained rise.(b) The killing of protozoa and nitrifying organisms. In no case have we observed all the usual partial sterilisation phenomena without the death of the larger protozoa which occur abundantly in cultures made from our soils.

The Effect of Partial Sterilisation of Soil on the Production of Plant Food: Part II. The Limitation of Bacterial Numbers in Normal Soils and its Consequences

The conclusions reached in our previous paper have been confirmed and extended. Fresh evidence is adduced that bacteria are not the only inhabitants of the soil, but that another group of organisms occurs, detrimental to bacteria, multiplying more slowly under soil couditions and possessing lower power of resistance to heat and to antiseptics.In consequence of the presence of these detrimental organisms the number of bacteria present in the soil at any time is not a simple function of the temperature, moisture content and other conditions of the soil. It may, indeed, show no sort of connection with them; thus rise of temperature is found to be ineffective in increasing the bacteria in the soil; increase in moisture content has also proved without action. The number of bacteria depends on the difference in activity of the bacteria and the detrimental organisms.

Investigations on “Sickness” in Soil: II. “Sickness” in Glasshouse Soils

Previous investigations in this laboratory have shown that partial sterilisation of soil leads to increased productiveness. In attempting to apply this method on the large scale two courses were open. The more obvious was to seek for methods cheap enough for use in the field, and then to conduct a number of field trials to determine which was the best; this was almost certain to prove a tedious and expensive business and would not necessarily lead to a successful issue. The alternative plan, and the one we adopted, was to find classes of growers who could afford to use our present methods of partial sterilisation and who would be willing to do so. However restricted their number of crops might be we knew that the cost of the process must fall once it was applied in commercial growing, so that the range over which it was applicable would soon begin to widen; a further advantage was that from the outset we should be gaining experience of the working of partial sterilisation in practice. Fortunately we met with a large tomato and cucumber grower in the Waltham Cross district who put us in touch with the class of growers we wanted: in this way we came across the problem of sickness in glasshouse soils which forms the subject of the present communication.

A note on the protozoa from sick soils, with some account of the life-cycle of a flagellate monad

Of recent years a great deal of attention has been attracted to the subject of sick soils, i. e. soils of which the produce has fallen off without the decrease being definitely attributable to the lack of plant-food in the soil. In this preliminary note I should like to deal shortly with some aspects of this question from a zoological point of view, and also to describe the life-cycle of a flagellate monad which happened to be one of the organisms from this source, of which I have succeeded in obtaining pure animal cultures. I hope to describe cultures of this and other forms in greater detail in a forthcoming paper. The literature on this subject from a botanical and chemical standpoint will be found in a paper by Dr. Russel and Dr. Hutchison “On the Effect of Partial Sterilisation of Soil on the Production of Plant-Food,” and it is particularly to this work that we owe the insistence on a hypothesis which is full of interest to the zoologist, namely, that the activity of protozoa in these soils may in many cases be a factor in bringing about soil-sickness.

A contribution to our knowledge of the protozoa of the soil

In the ‘Journal of Agricultural Science,’ Vol. III, Part 2, 1909, Drs. Russell and Hutchinson of this laboratory published an account of their investigations on the effect of partial sterilisation of soil on the production of plant food. In this paper it is shown that, when soils are heated or treated with certain volatile antiseptics, and brought again under conditions favourable to plant growth, they show a great increase in fertility. It is further shown that, although the bacteria are at first reduced very considerably in numbers, yet under conditions of temperature, moisture, and aëration favouring growth, they subsequently increase enormously in numbers.Pari passuwith this increase in the number of bacteria, there is an increase in the production of ammonia in the soil, and it is to this that the soil owes its greater power of production. In explanation of these results, the theory is advanced that the treatment by heating or with antiseptics has removed some factor which in the untreated soil normally limits the growth of bacteria, and thus the rate of ammonia production. This limiting factor is looked upon as being biological in character, but not of a bacterial nature.