soil microbial biomass carbon

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Abstract IC2015 Soil Microbial biomass C and microbial activity as influenced by pesticide use in Paddy Sanjay Arora 1 , Divya Sahni 1 , Sumitra Arora 2 , M. Sehgal 2 , D.S. Srivastava 3 and A. Singh 3 1 ICAR-Central Soil Salinity Research Institute, Regional Research Station, Lucknow 226002, U.P.; 2 ICAR-NCIPM, Pusa, New Delhi; 3 KVK Sitapur II, Katia, Sitapur (U.P.) Soils and their biodiversity play a critical role in maintaining soil health. Non-return or diminished return of organic matter and residues deprive the soil biota of their food with loss of soil health and fertility. A large, diverse, and active population of soil organisms is the most important indicator of a healthy soil. The effects of physical and chemical degradation of soils are obvious. Pesticides are the important agrochemicals used for prevention of crops from pests. The application of pesticides starts from the pre sowing stage. The indiscriminate use of pesticides disturbs the soil environment by affecting flora and fauna including microflora of soil, and also the physico-chemical properties of the soil like pH, salinity, alkalinity leading to infertility of soil. When pesticides are applied, the possibilities exist that these chemicals may expert certain effects on non-target organisms, including soil micro organisms. The microbial biomass plays an important role in the soil ecosystem where they fulfill a crucial role in nutrient cycling and decomposition. A series of field experiments were conducted at farmer’s field at Sitapur with different modules of integrated pest management including safe formulations. The impact of these pesticides was assessed on the soil properties including soil microbial populations, microbial biomass carbon and enzymatic activity. It was observed that soil microbial biomass C (MBC) content and dehydrogenase activity was influenced by IPM interventions. In field conditions, soil MBC content varied from 60 mg/kg to 182 mg/kg where safer pesticides were used while in modules where

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Soil microbial biomass carbon

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Page 1: Soil microbial biomass carbon

Abstract IC2015

Soil Microbial biomass C and microbial activity as influenced by pesticide use in Paddy

Sanjay Arora1, Divya Sahni1, Sumitra Arora2, M. Sehgal2, D.S. Srivastava3 and A. Singh3

1ICAR-Central Soil Salinity Research Institute, Regional Research Station, Lucknow 226002, U.P.; 2ICAR-NCIPM, Pusa, New Delhi; 3KVK Sitapur II, Katia, Sitapur (U.P.)

Soils and their biodiversity play a critical role in maintaining soil health. Non-return or diminished return of organic matter and residues deprive the soil biota of their food with loss of soil health and fertility. A large, diverse, and active population of soil organisms is the most important indicator of a healthy soil. The effects of physical and chemical degradation of soils are obvious. Pesticides are the important agrochemicals used for prevention of crops from pests. The application of pesticides starts from the pre sowing stage. The indiscriminate use of pesticides disturbs the soil environment by affecting flora and fauna including microflora of soil, and also the physico-chemical properties of the soil like pH, salinity, alkalinity leading to infertility of soil. When pesticides are applied, the possibilities exist that these chemicals may expert certain effects on non-target organisms, including soil micro organisms. The microbial biomass plays an important role in the soil ecosystem where they fulfill a crucial role in nutrient cycling and decomposition.A series of field experiments were conducted at farmer’s field at Sitapur with different modules of integrated pest management including safe formulations. The impact of these pesticides was assessed on the soil properties including soil microbial populations, microbial biomass carbon and enzymatic activity. It was observed that soil microbial biomass C (MBC) content and dehydrogenase activity was influenced by IPM interventions. In field conditions, soil MBC content varied from 60 mg/kg to 182 mg/kg where safer pesticides were used while in modules where farmers used overdoses of pesticides, SMBC content ranged between 24 to 118 mg/kg. Soil bacterial populations were drastically reduced from 6.2x105 c.f.u./g to 1.8x104 c.f.u./g on nutrient agar after 24 hours of growth in soil from farmers practice of using pesticides. Similarly, where safer pesticides were used, bacterial load in soil enhanced from 5.4 x104c.f.u./g to 4.1x105

c.f.u./g. Similarly, in laboratory incubation, soil MBC increased from 218 mg/kg upto 28 days and thereafter decreased to 128 mg/kg at 72 days. Soil C and N mineralization was also found to be influenced by pesticides.

Keywords: soil microbes, bio-chemical properties, pesticides, IPM

Page 2: Soil microbial biomass carbon

Abstract

Diversity of Soil Microbes from Paddy soils of Sitapur and their screening for Salt and pH Tolerance

Sanjay Arora1, Divya Sahni1, Sumitra Arora2, M. Sehgal2, D.S. Srivastava3 and A. Singh3

1ICAR-Central Soil Salinity Research Institute, Regional Research Station, Lucknow 226002, U.P.; 2ICAR-NCIPM, Pusa, New Delhi; 3KVK Sitapur II, Katia, Sitapur (U.P.)

A large, diverse, and active population of soil organisms is the most important indicator of a healthy soil. A study was conducted with the objective to isolate and characterize salt and pH tolerant soil microbes. Soils samples were collected from the 20 paddy soils of Sitapur, Uttar Pradesh. The soil samples were analysed for physical, chemical and bio-chemical soil properties. Soil pH ranged from 6.35 to 8.64, EC from 0.04 to 1.11 dS/m and falling in textural class of loamy sand to silty clay loam. Organic carbon content ranged from 2.1 to 5.4 g kg-1 while microbial biomass C content ranged from 60 mg/kg to 182 mg kg-1. Available N, P and K content ranged from 81.9 to 179.8, 5.9 to 19.9 and 154.3 to 232.2 kg ha -1, respectively. From the microbiological analysis of soil samples, it was found that all soils contain abundance of microorganisms on nutrient agar plates at 37oC for 24 hours. The colony forming unit of bacterial population per gram soil ranged from 4.65×106 to 3.60x104. Fungal population on potato dextrose agar ranged between 14x104 to 102x104 MPN/g soil. Out of the total bacterial isolates, 132 isolates tolerated 5% NaCl concentration while 47 isolates were able to tolerate 10% and only 5 could tolerate 15% NaCl concentration in the media. Most of the isolated bacteria were Gram-positive and of rod shaped. There was a great variation in their colony characteristics. Gram’s staining showed 103 were cocci while 34 were bacilli. Eleven isolates were yellow pigmented and 46 were creamy or off white. The dominant fungal isolates were Aspergillus, Cladosporium, Rhizopus, Trichoderma and Penicillium.