Effect of Organic Amendments on Soil Mycoflora

In present study, the influences of different organic soil amendments on soil fungi was studied. Soil organisms carry a wide range of processor that are important for soil health and partially in both natural and managed agricultural scales. The total number of organisms, the diversity of species and activity of soil biota will fluctuate as soil environment changes. Three types of soil amendments and fertilizers viz., urea, FYM and vermicompost were used to amend the cultivated agricultural soil. The fungi were isolated from soil by using dilution plate technique and soil plate method. The dynamics of soil fungi were observed qualitatively as well as quantitatively. The maximum number of fungi was recorded when soil amended with FYM (40.6x10⁴ g^-1), urea (38.8x10⁴ g^-1) of dry soil at different concentration 2.0, 1.5 and 2.0%, respectively. In control where soil was not amended with any organic amendment, the number of fungi was 13.0x10⁴ to 16.8x10⁴ g^-1, 14.4x10⁴ to 16.8x10⁴ g^-1, 13.8x10⁴ to 16.8x10⁴ g^-1 in urea, FYM and Vermicompost, respectively. A total 25 fungi were observed during the experimental period. Eighteen were observed when soil amended with urea, twenty-two observed when soil amended with FYM and 20 when soil amended with vermicompost. In control soil only fifteen fungi were recorded. The result showed that the number of fungi was increased in amended soil. Qualitatively, the fungi Rhizopus stolonifer, Aspergillus niger, Aspergillus flavus, Trichoderma harzianum, Penicillium citrinum, Alternaria alternata and Curvularia lunata, White Sterile Mycelium and Black Sterile Mycelium were observed.

INTRODUCTION

The microorganisms carry out a number of transformations in the soil as part of their normal activities and at the same time they are instrumental in adding organic matter to soil (Brady and Weil, 1999). The total number of organisms, the diversity of species and the activity of the soil biota fluctuates with changing soil environment. These changes may be caused by natural or imposed systems. Plant residues provide sources of energy and nutrient for the biota, which turnover organic matter improve nutrient availability and soil structures and prevent disease and degrade pollutants. Soil biota can increase and reduce agricultural production (Badale and More, 2000). Well aggregated soils provides a better living environment for soil organisms and support larger population, soil-borne fungi not add mucus but the vast network of thread-like hyphae hold the soil particles together improving stability (Otten and Gilligan, 1998; Harris et al., 2003; Otten et al., 2004). Soil microbial activity is a biomarker of degradation of remediation (Pascual et al., 2000). The ecological studies of soil fungal flora was made by Reichardt et al. (2001), Li et al. (2001) and Marschner et al. (2003). In this respect, the soil microflora can be manipulated and protected to enhance the nutrient cycling, which improves chemical and physical properties and regulates the decomposition process in soil (Rezacova et al., 2007). Soil amendments such as plant residues, manures and composts play a major role in changing the soil ecosystem; its physio-chemical characteristics and soil microflora are of great significance in soil microbiology (Anastasi et al., 2005). Recently, several reports (Wada and Toyota, 2004; Girvan et al., 2005) have found that organic amendment may enhance soil functional stability mediated by soil microbial community. Microbial community composition cab be more sensitive to soil amendment with plant residues than microbial biomass and it is possible that the different forms of organic amendments such as organic fertilizers i.e., urea, FYM and vermicompost stimulate soil microbial growth and activity, with subsequent mineralization of soil nutrients (Randhawa et al., 2005), but the ability to deliver nutrients depends on the composition of the amendments. Since availability of carbon substrates largely controls microbial growth in soil, it is a key factor governing nitrogen, phosphorus and sulphur cycling. Previous studies have found that amendment with farmyard manure (Toyota et al., 1999) and spent mushroom compost (Piqueres et al., 2006) significantly affected soil microbial community structure. However, the effects of compost were found to vary depending on both the type of compost and the soil type (Piqueres et al., 2006). Microorganisms form a vibrant living community in the soil contributing to a number of nutrient transformations. They are involved in organic matter decomposition, nitrogen-fixation, solubilization and immobilization of several major and minor nutrients (Katayama et al., 1998; Lal, 1998; Muller et al., 1998). In the present study an attempt has been made to analyze the effect of different amendments on fungal population in soils at different-time intervals (Zaller and Koepke, 2004; Hole et al., 2005; Chang et al., 2007; Stark et al., 2007).

MATERIAL AND METHODS

The whole method was done at Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, B.H.U., Varanasi, India during 1st July 2009 to December 2009. For the study of fungal community associated with soils, different isolation techniques were adopted. The soil inhabiting fungi were studied by Dilution plate technique and soil plate method technique. Dilution plate technique gives the useful information of the number of each type of microorganism in the soil samples. The soil sample was crushed and 10 g of it was suspended in 100 mL of sterilized distilled water. Further dilution series 1:1000, 1:10,000, 1:1, 00, 000 were prepared from it. One milliliter of each dilution was poured individually in sterilized Petri plates. Then 15-20 mL of sterilized nutrient medium was added. Five replications of each dilution were prepared and all plates were incubated 25±2°C for a week. In soil plate method a plate was prepared by transferring a small amount of soil to be examined into sterile petri dish. The amount of soil should result in at convenient number of fungal colonies on each plate. The soil was transferred with help of inoculating needle 10-15 mL of melted agar medium, the dispersal was obtained by gently shaking and rotating the plate before the agar solidifies. The plates were then allowed to incubate at 25-30°C for a period of 2-3 days.

Total No. of fungi/g over dried soil was calculated on the basis of total number of fungi in particular concentration being divided by over dry weight of soil:

Frequency and abundance of fungi were determined with the help of following formula (Saksena, 1955). pH was determined with the help of Elico-Electric pH meter. Moisture content was determined on the basis of percentage loss in dry weight. Available Nitrogen was determined by alkaline permanganate method by Subbiah and Asija (1956). The method of Olsen et al. (1954) was used for determination of available Phosphorus in soil. Potassium determined by flame photo metrically (Jackson, 1973). Organic carbon in soil was determined by chronic acid rapid titration method (Walkley and Black, 1934). Organic Matter was estimated by multiplying total carbon with constant factor 1.724.

RESULTS

The data of pH, moisture content and average number of fungi per gram of dry soil is presented in Table 1, maximum pH was 7.18 at 30 and 45 days at 2%, maximum moisture was 33.20 at 15 days 1% and maximum average number of fungi 40.6x10⁴ at 15 days at 2% concentration of FYM. The maximum fungi were recorded when the soil amended with FYM (40.6x10⁴ g^-1), urea (38.8x10⁴ g^-1) and vermicompost (35.6x10⁴ g^-1) of dry soil at different concentration 2.0, 1.5 and 2.0%, respectively. In control where soil was not amended with any organic amendment, the number of fungi was 13.0x10⁴ g^-1 to 16.8x10⁴ g^-1, 14.4x10⁴ g^-1 to 16.8x10⁴ g^-1, 13.8x10⁴ to 16.8x10⁴ g^-1 in urea, FYM and Vermicompost respectively. The soil fungi were determined by dilution plate technique, recorded as frequency and abundance of fungi at different organic amendments viz., urea (Table 2), eighteen fungus were found and frequency of Aspergillus niger was maximum that is 5 at 1.5% concentration at 15 days and abundance of Aspergillus niger is maximum that is 4 at 1.5% at 15 days and 30 days respectively and Penicillium citrinum, abundance is maximum (4) at 1.5% concentration of urea at 30 days. Soil amended with FYM (Table 3), twenty-two fungus were observed and Aspergillus niger frequency (5) were maximum at 1, 1.5 and 2% concentrations of FYM at 15 days and abundance (4) were maximum at 2% concentration of FYM at 15 and 30 days,respectively.

Table 1:	The pH, moisture content, average number of fungi/g of soil in control and amended with different concentrations of urea, FYM and vermicompost

Table 2:	Isolation of fungi from soil amended with urea
F: Frequency in percent, A: Abundance in absolute number

Table 3:	Isolation of fungi from soil amended with FYM
F: Frequency in percent, A: Abundance in absolute number

Soil amended with vermicompost (Table 4), twenty fungus were observed in which Aspergillus niger frequency (5) and abundance (4) were maximum at 2% concentration at 15 days.

Table 4:	Isolation of fungi from soil amended with Vermicompost
F: Frequency in percent, A: Abundance in absolute number

Table 5:	Isolation of fungi from soil in control condition
F: Frequency in percent, A: Abundance in absolute number

In control conditions (Table 5) where soil was not amended with any organic amendment only Fifteen fungus were found in which frequency (4) of Aspergillus niger was maximum at 15 and 30 days respectively and abundance (3) of Aspergillus niger, Penicillum citrinum and Alternaria alternata were maximum at 15 days. They may be classify into three groups according to their appearance, frequency abundance and their sporulation. The values of nitrogen, phosphorus, potassium, carbon and organic matter were furnished in (Table 6). Which indicate the variation of Nitrogen 365-518 kg h^-1, Phosphorus 30.5-36.1 kg h^-1, Potassium 189-267.2 kg h^-1, Carbon 0.28-0.58 percent and Organic matter 0.48-0.99%. The values of NPK were increased in the soil amended with urea, FYM and Vermicompost.

Table 6:	Nutrient content of the soil after amended with urea, FYM and vermicompost
N: Nitrogen, P: Phosphorus, K: Potassium, C.C: Carbon content, O.M: Organic matter

The nitrogen content varies from in soil amended with urea 368-518 kg h^-1, FYM 365-398 kg h^-1 and Vermicompost 365-407 kg h^-1.

DISCUSSION

Moisture content plays an important role in microbial activity in the soil. Increasing moisture contents help in increasing microbial activities. Maximum moisture content (33.20%) was recorded at 15 days sampling amended with FYM. Madge (1965) has shown marked effect of moisture on the number of soil fungi. Moisture content is chiefly responsible for the colonization of microorganisms (Hudson, 1971; Dunn et al., 1985; Pandey et al., 1991; Marinari et al., 2000; Zaller and Koepke, 2004). The pH of the soil varied from 6.28 to 7.34. The pH of soil amended with FYM and vermicompost was higher than the soil amended with urea. The increase in pH was due to decomposition of FYM and vermicompost (Shiralipour et al., 1992; Kannan et al., 2005).

The dominant fungi were those, which appeared in almost all sampling and more in number. In this group following fungi were included: Rhizopus stolonifer, Aspergillus niger, Aspergillus flavus, Penicillium citrinum, Fusarium oxysporum and Trichoderma harzianium. In the common group of fungi are Mucor racemosus, Aspergillus sulphureus, Aspergillus terreus, Aspergillus sydowi, Aspergillus candidus, Trichoderma viridae, Alternaria alternata, Curvularia lunata and Cladosporium cladosporiodes are found they are less than 75% and more than 50%. Rare group included those fungi appeared once. These are Nigrospora sphaerica, Chaetomium globosum, Phoma hibernica and Helminthosporium oryzae. The beneficial effect of fertilizer in increasing fungal population was reported by many workers (Jadhaw et al., 1997; Gunapala and Scow, 1998; Marinari, 2000; Karmegan and Daniel, 2000; ICRISAT and APRLP, 2003) and ascribe the higher nutrient supply as the reason for it. It is also clear from the data that fungal population of amended soil decreased with the increase of incubation period. The reason for it may be that during the early phase of incubation (15 days) most of the nutrient status of fertilizers is utilized by the soil inhabitant, hence, they increased in number, but at later stages nutrient level decreased and consequently lower the fungal counts (Elmholt and Zabruriau, 2005; Singh et al., 2007; Guerrero et al., 2007; Mandal et al., 2007).

It has been attributed by several workers (Agarwal and Chauhan, 1988; Bulluck et al., 2002) that urea is a good source of nitrogen for the microbial growth and multiplication. Soil available Phosphorus varied from in soil amended with urea 31.8-36 kg h^-1, FYM 30.5-36.1 kg h^-1 and vermicompost 30.6-35 kg h^-1, while the available Potassium in soil amended with these three amendments, ranged between 189-248.5, 235.9-256.8 and 239.8-259.8 kg h^-1 in urea, FYM and vermicompost, respectively. Soil available Phosphorus, Potassium were either or higher than initial value. In most of the Indian soil the amount of organic matter is relatively less and influence on physical properties can be largeness. The soil organic amendments viz. urea, FYM and vermicompost can help to maintain or increase soil organic matter and improve the physical properties. The changes in physico-chemical properties of soil were studied by Das et al. (1947), Chander et al. (1998), Balloli et al. (2000) and Chakrabarti et al. (2000).