Soil application of dinitroaniline and arylphenoxy propionic herbicides influences the activities of phosphate-solubilizing microorganisms in soil

Abstract

An experiment was conducted under laboratory conditions to investigate the effect of two systemic herbicides, viz. pendimethalin (a dinitroaniline) and quizalofop (an arylphenoxy propionic acid) at their recommended field application rates (1.0 kg and 50 g active ingredient per hectare, respectively), either separately or in a combination, on growth and activities of phosphate-solubilizing microorganisms in relation to their effects on biochemical transformations and availability of organic carbon, total and available phosphorus in a Typic Haplustept soil of West Bengal, India. Application of herbicides, in general, significantly stimulated the growth and activities of phosphate-solubilizing microorganisms which increased microbial biomass resulting in higher accumulation of oxidizable organic carbon, total and available phosphorus in soil as compared to untreated control. The combined application of both the herbicides highly stimulated the proliferations of phosphate-solubilizing microorganisms, while pendimethalin alone significantly accentuated phosphate-solubilizing capacities 36.4% as compared to untreated control and retained highest amount of total phosphorus due to greater microbial activities in soil. The separate application of quizalofop also manifested an induced effect on the proliferations of phosphate-solubilizing microorganisms and accounted significant amounts of organic carbon and available phosphorus in the soil system. The results of the present study thus indicated that the cited herbicides at their field application rates can be safely used to eradicate weeds in the crop fields.

Non-symbiotic N2-fixation and phosphate-solubility in Gangetic alluvial soil as influenced by pre-emergence herbicide residues

“…Application of both the herbicides, in general, significantly increased the phosphate-solubilizing capacities of soil up to 15 days of sampling, followed by a gradual decrease up to the end of the experiment. This was in accordance with the proliferation of the phosphate-solubilizing microorganisms (Ahemad and Khan, 2011;Das et al, 2012a) and was confirmed by the presence of significant positive correlation (r = 0.817, p < 0.01) between proliferation of phosphate-solubilizing microorganisms and their capacities in solubilizing insoluble phosphates in soil.…”

“…Sustaining the earlier reports (Jones and Oburger, 2011;Das et al, 2012a), stimulation of phosphate-solubilizing microorganisms manifested greater solubilization of insoluble phosphates in soil (Table 5), and this effect was more pronounced under pretilachlor (37.2%), in spite of exerting lower number of phosphatesolubilizers, as compared to thiobencarb (29.9%) at lower concentrations. This indicated that pretilachlor at field application rate highly induced the efficiency of the phosphate-solubilizing microorganisms rather than their growth and multiplication (Nongthombam et al, 2008).…”

Pesticides jiggling microbial transformation of phosphorus in soil

“…Following the method of Das et al (2012) Microbial biomass carbon was determined by chloroform fumigation following the method of Joergensen (1995). There were two sets of moist soil-one set in conical flasks fitted with a stopper and the other set in beakers.…”

“…Using pesticides as nutrient and energy source (Paul et al, 2010), the higher growth and activity of P-solubilizing micro-organisms as well as greater acid and alkaline phosphatase activity affected greater solubilization of insoluble inorganic phosphate compounds as well as mineralization of organic P to a larger extent. This in turn was translated to the enhancement in P availability of soil (Das and Debnath, 2006;Das et al, 2012). Even the microbial phosphorus may provide addendum to P availability in soil after mineralization of dead zymogenous organisms (Tiessen et al, 2011).…”

“…Das et al (2012) found a significant enhancement in the potentiality and growth of phosphate solubilizing microorganisms by the application of pesticides in soil. On the other hand, there are reports about the detrimental influence of pesticides on the growth and performance of phosphorus solubilizers (Das et al, 1998).…”