Assessing the potential of a Trichoderma-based compost activator to hasten the decomposition of incorporated rice straw

The potential for a Trichoderma-based compost activator was tested for in-situ rice straw decomposition, under both laboratory and field conditions. Inoculation of Trichoderma caused a 50% reduction in the indigenous fungal population after 2 weeks of incubation for both laboratory and field experiments. However, the Trichoderma population declined during the latter part of the incubation. Despite the significant reduction in fungal population during the first 2 weeks of incubation, inoculated samples were found to have higher indigenous and total fungal population at the end of the experiments with as much as a 300% increase in the laboratory experiment and 50% during day-21 and day-28 samplings in the field experiment. The laboratory incubation experiment revealed that inoculated samples released an average of 16% higher amounts of CO2 compared to uninoculated straw in sterile soil samples. Unsterile soil inoculated with Trichoderma released the highest amount of CO2 in the laboratory experiment. In the field experiment, improved decomposition was observed in samples inoculated with Trichoderma and placed below ground (WTBG). From the initial value of around 35%, the C content in WTBG was down to 28.63% after 42 days of incubation and was the lowest among treatments. This is significantly lower compared with NTBG (No Trichoderma placed below ground, 31.1% C), WTSS (With Trichoderma placed on soil surface, 33.83% C), and NTSS (No Trichoderma placed on soil surface, 34.30% carbon). The WTBG treatment also had the highest N content of 1.1%. The C:N ratio of WTBG was only 26.27, 39.51% lower than the C:N ratio of NTBG, which is 43.43. These results prove that the Trichoderma-based inoculant has the potential to hasten the decomposition of incorporated rice straw.

The use of soil biostructures created by soil fauna ecosystem engineers fed with different organic matterials as inoculum source of arbuscular mycorrhiza fungi on cocoa seedling

<p><span lang="IN">Soil fauna as ecosystem engineers </span><span>have the ability to </span><span lang="IN">creat</span><span>e </span><span lang="IN">soil biostructure</span><span>s, with the capacity to </span><span lang="IN">sav</span><span>e</span><span lang="IN"> arbuscular mycorrhizal fungi (AMF) spores. </span><span>This study therefore aims to </span><span lang="IN">investigate the </span><span>AMF </span><span lang="IN">spore density in the biostructures created by cooperation between earthworms and ants with a different organic matter composition</span><span>,</span><span lang="IN"> and to analyze the </span><span>biostructures’ </span><span lang="IN">potential as a source of </span><span>AMF </span><span lang="IN">inoculum on cocoa seedlings. </span><span>In the first experiment, a </span><span lang="IN">combination of earthworms and ants composition</span><span>, as well as a </span><span lang="IN">mixture of <em>G. sepium</em> leaf (GLP), cocoa shell bean (CSB), and sago dregs (SD)</span><span>,</span><span lang="IN"> was tested</span><span>. Meanwhile, </span><span lang="IN">in the </span><span>second</span><span lang="IN"> experiment</span><span>, t</span><span lang="IN">he</span><span> effect of</span><span lang="IN"> biostructures on cocoa seedlings grown </span><span>i</span><span lang="IN">n unsterile soil</span><span>,was </span><span lang="IN">examined</span><span>. According to the results, the highest</span><span lang="IN"> AMF spore </span><span>density was obtained using </span><span lang="IN">20 earthworms+10 ants with 50%GLP+50%CSB + 0%SD treatment</span><span>. Furthermore, the t</span><span lang="IN">otal AMF spores </span><span>were </span><span lang="IN">positively correlated</span><span> with the total P value, but negatively correlated </span><span lang="IN">with </span><span>the </span><span lang="IN">C/N ratio</span><span>. Therefore, bi</span><span lang="IN">ostructure application increased AMF spores number in rhizosphere and </span><span>the cocoa seedling’s </span><span lang="IN">root infection</span><span>. Furthermore, </span><span lang="IN">biostructure</span><span>s</span><span lang="IN"> resulting from the collaborative activity </span><span>between</span><span lang="IN"> different soil fauna ecosystem engineers </span><span>were able to transmit </span><span lang="IN">AMF spore</span><span>s </span><span lang="IN">to </span><span>infected </span><span lang="IN">plant root</span><span>s</span><span lang="IN"> growing </span><span>i</span><span lang="IN">n non-sterile soil.</span></p>

Production, stability and degradation of Trichoderma gliotoxin in growth medium, irrigation water and agricultural soil

Gliotoxin produced by Trichoderma virens is inhibitory against various phytopathogenic fungi and bacteria. However, its stability in soil-ecosystem has not yet been well-defined. This study aimed to decipher its persistence and behaviour in growth media, irrigation water and soil ecosystems. Gliotoxin production was noticed at logarithmic growth phase and converted into bis-thiomethyl gliotoxin at late stationary growth phase of T. virens in acidic growth medium. But, no gliotoxin production was observed in neutral and alkaline growth medium. Gliotoxin was stable for several days in acidic water but degraded in alkaline water. Degradation of gliotoxin was more in unsterile soil than sterile soil and also that was higher under wet soil than dry soil. Degradation of gliotoxin was hastened by alkaline pH in wet soil but not in dry soil. Under unsterile soil conditions, high soil moisture increased the degradation of gliotoxin and the degradation of gliotoxin occurred quickly in alkaline soil (in 5 days) compared to acidic soil (in 10 days). Under sterile soil conditions, high soil moisture also enhanced the degradation of gliotoxin but level of degradation was less compared to unsterile conditions. Thus, gliotoxin stability is influenced mainly by the soil wetness, soil microbial community and pH conditions.

AKTIVITAS EFFECTIVE MICROORGANISMS (EM) DALAM TANAH PERTANIAN ORGANIK YANG TERPAPAR KLORPIRIFOS

One way to restore soil fertility exposed to pesticides such as chlorpyrifos is by bioremediation using Effective Microorganisms (EM). The purpose of this study was to determine EM microbial resistance and chlorpyrifos degrading enzyme activity in organic farming soil sample.The organic farming soil sample used previously has been exposed to EM for a long time. This soil sample was divided into two treatments, namely sterilized by autoclaving and not sterilized (thus indigenous microbes remain alive). The next two soil samples were with and without addition of EM with incubation time of 3, 5, and 7 days. The results of this study indicated that EM microbes could withstand exposure to chlorpyrifos to a concentration of 56 ppm. The phenomenon of chlorpyrifos degrading enzyme activity was found in sterile soil samples with EM addition of 0.017 U/mL during 7-day incubation with a decrease in chlorpyrifos levels of 16.65%. The highest activity of chlorpyrifos degrading enzyme was found in unsterile soil sample, which amounted to 0.039 U/mL during the 3-day incubation period with a decrease in chlorpyrifos levels of 74.11%. The highest decrease in chlorpyrifos was found in unsterile soil sample by 80.04% with an incubation time of 5 days. Keywords: chlorpyrifos, bioremediation, microbial EM (Effective Microorganisms)

Soil is a key factor influencing gut microbiota and its effect is comparable to that exerted by diet for mice

Exposure to an unsanitary environment increases the diversity and alters the composition of gut microbiota. To identify the key element in the unsanitary environment responsible for this phenomenon, we investigated the effect and the extent by which the soil in our environment influenced the composition of gut microbiota. Results show that adding unsterile or sterile soil to bedding, either before birth or after weaning, influences significantly the composition of mice gut microbiota. Specifically, unsterile soil increases the richness and biodiversity of gut microbiota. Interestingly, based on UniFrac distance analysis of 16S rRNA sequences, the impact of soil on gut microbiota is comparable to that exerted by diet. These findings provide a potential new strategy for intervening on the human gut microbial community and preventing disease.

Changes in DTPA extractability of added cadmium in two different soil types treated with wheat straw in sterile and unsterile conditions

Heavy metals in soluble form have the highest bioavailability and toxicity in soil. DTPA-extractable Cd was investigated in two different soil types treated with wheat straw (5%) under sterile and unsterile conditions. Soils were located in Hamadan (Iran, 48^o 28^' 23" E and 34^o 56' 48" N), a fallow cropland with a semi-arid climate, and Lahijan (Iran, 50^o 1^' 51" E and 37^o 11' 59" N), a tea plantation with a temperate climate. DTPA-extractable Cd in contaminated soils (10 mg Cd kg^-1) was measured from 1 minute to 3600 hours. During the soil incubation period, DTPA-extractable Cd was higher in the Lahijan soil, but at the end of the soil incubation period it was higher in the Hamadan soil. The positive effect of wheat residue on DTPA-extractable Cd was higher in the Lahijan unsterile soil at the end of the soil incubation period. The decrease of DTPA extractability of the added Cd was lower in the Lahijan soil incubated under unsterile conditions compared to that under sterile conditions. In contrast, Hamadan sterile soil treated and untreated with wheat residue had the highest DTPA-extractable Cd at the end of the soil incubation period. The decrease in DTPA extractability of the added Cd in soils was exponential with 3 steps. In the 1^st step the highest and the lowest rates of DTPA decrease were observed in Hamadan sterile and Lahijan unsterile soils treated with wheat residue. In the 3^rd step it was reversed, and the decrease in DTPA extractable Cd was lower in the Hamadan soil compared to the Lahijan soil.

Soil Microbial Root Colonization of Glyphosate-Treated Giant Ragweed (Ambrosia trifida), Horseweed (Conyza canadensis), and Common Lambsquarters (Chenopodium album) Biotypes

Root colonization by soil microorganisms has been shown to increase the activity of glyphosate in resistant and susceptible biotypes of giant ragweed and a susceptible common lambsquarters biotype, but not in horseweed biotypes. The objective of this study was to investigate the colonization of roots in glyphosate-resistant and -susceptible giant ragweed and horseweed biotypes, and glyphosate-tolerant and -susceptible biotypes of common lambsquarters after a sublethal glyphosate application. The three weed species were grown separately in sterile and unsterile field soil and treated with glyphosate at two sublethal rates. Soil microbes were isolated from the roots onto sterile media 3 d after the glyphosate treatment. The susceptible biotypes of giant ragweed and horseweed grown in unsterile soil were colonized by more soil microbes at the higher rate of glyphosate, compared to the resistant biotype grown in unsterile soil. Oomycetes were isolated separately on a selective media and they were also more prevalent in the roots of the susceptible biotypes of each weed species grown in the unsterile soil when glyphosate was applied at the highest rate. Therefore, the ability of these three weed species to tolerate a glyphosate application may involve differences in the susceptibility to soil microbial colonization, especially oomycetes.

Effects of Certain Isolates of Bacteria and Actinomycetes on Gaeumannomyces graminis var. tritici and Take-All of Wheat

Five isolates each of actinomycetes, bacteria and fluorescent pseudomonads from the roots of wheat were tested for antagonism against Gaeumannomyces graminis var. tritici on agar and in sterile and unsterile soil. There was no apparent correlation between the tests. Effects on the growth of the take-all fungus (TAF) on agar ranged from nil to various degrees of colony deformation and/or inhibition. In a sterile sandy subsoil growing wheat seedlings, all except one isolate had no effect on disease production by a straw inoculum of the TAF. In an unsterile soil, however, measurements of shoot weight indicated that disease was reduced by all five isolates of bacteria singly and in mixture and by four of the five isolates of actinomycetes and a mixture of all five. Although a mixture of all five isolates of fluorescent pseudomonads reduced the disease, none of them produced a similar effect when tested singly. In the absence of the pathogen none of the test organisms significantly increased the shoot weight of wheat.