Effect of Different Doses of Pendimethalin on Microbial Activities and Nodulation in Chickpea

Abstract

Field trial was conducted at research farm of weed science research center, Parbhani, in split plot design with an objective to study the effect of herbicides on biochemical activities and nodulation in chickpea (maize-chickpea cropping system) during 2012–2013.The soil of experimental plot was black cotton soil with medium fertility and pH 7.9, EC 0.32 dsm⁻¹, and OC 0.57%. The treatments comprised of four weed control measures (weedy check, mechanical weeding, weed free, and pendimethalin 1.0 kg ha⁻¹). The soil samples were collected from rhizospheric soil from each plot at 30, 50 DAS and at harvest of crop and were analyzed for soil microbial biomass carbon and basal soil respiration and number of nodules and nodule dry matter. The results revealed that there were nonsignificant variations observed due to various treatments in affecting soil physicochemical properties of soil at various crop growth stages. Highest microbial population, microbial biomass carbon, and basal soil respiration were recorded in mechanical weeding, whereas lower activities were recorded in pendimethalin applied plots at 1.0 kg ha⁻¹ at 30 DAS. These values were enhanced at harvest. Application of pendimethalin1.0 kg ha⁻¹ did not influence nodal count and nodal dry matter significantly.

1 Introduction

Soil microbial populations are immersed in a framework of interactions known to affect plant fitness and soil quality. They are involved in fundamental activities that ensure the stability and productivity of both agricultural systems and natural ecosystems. The soil samples were collected from the rhizospheric layer of plant from herbicide-treated plots; it is to be used for all the microbial and biochemical analysis. It is to be collected at three stages of crop growth, viz., maximum vegetative growth stage (30 DAS), flowering stage (60 DAS), and at harvest. The soil samples were analyzed for following observations: pH, EC and organic carbon, microbial biomass carbon, basal soil respiration, total number of “N” fixers, total number of “P” solubilizers, nodule numbers, nodule dry matter, and the percent root colonization by VAM fungi.

2 Materials and Methods

The field experiment was conducted on permanent herbicide trial in maize-chickpea cropping system during kharif season of 2011–2012 in split plot design replicated three times. This investigation was an attempt to check the effect of different pre and postemergence herbicide on soil physicochemical and biological properties in relation to chickpea rhizosphere (Table 12.1).

Table 12.1 Treatments details

3 Method for Microbial Count

The soil samples were collected up to 15 cm depth and processed for microbial analysis following the dilution plate technique. The population of bacteria and fungi were determined by the standard pour plate technique using soil extract agar media for bacteria and Rose Bengal Agar media for fungi. Triplicate plates for each sample and microbial group were used for microbial population before sowing and after harvest.

4 Results and Discussion

4.1 Effect of Weed Control Treatments in Chickpea (Rabi Season)

4.1.1 Microbial Biomass Carbon and Basal Soil Respiration

The basal soil respiration was not influenced due to weed control treatment. Significantly higher basal soil respiration were observed in T₂ (mechanical weeding) followed by T₁, i.e., (weedy check), whereas significantly lowest biochemical activities were observed in treatment C4, i.e., pendimethalin at 0.75 kg ha⁻¹ fb 2,4-D at 0.5 kg ha⁻¹ followed by treatment C3 pendimethalin at 1.5 kg ha⁻¹ (Table 12.2).

Table 12.2 Effect of different doses of herbicide on soil microbial biomass and basal soil respiration in maize-chickpea cropping system

5 Total “N” Fixers and “P” Solubilizers

In chickpea a total number of “N” fixer were observed more than total number of “P” solubilizer. Both the beneficial microorganisms were increased in their numbers from initial to harvest. At initial days, beneficial microflora were significantly lowest in treatment C₄ - pendimethalin 0.75 kg ha⁻¹ fb mechanical weeding and C₃ - pendimethalin 1.00 kg/ha, whereas highest count was observed in T₂ mechanical weeding, but at the time of harvest, the number of beneficial microflora was increased, and differences were nonsignificant (Table 12.3). Similar results were also reported by Bhutada et al. (2014), Singh et al. (2013), Yadav et al. (1983), Narendra Kumar et al. (2014), and Sunil Kumar et al. (2010).

Table 12.3 Effect of different doses of herbicide on soil total “N” fixers and total “P” solubilizers in maize-chickpea cropping system

6 Nodule Number and Nodule Dry Matter

Effect of different herbicide on nodule number and nodule dry matter is shown above. Nodule number and nodule dry matter were not influenced by different herbicide in chickpea. Numerically highest nodule numbers were observed in T₂ mechanical weeding, whereas there were no significant differences in nodule numbers and nodule dry matter in herbicide treatment. Lowest nodule number and nodule dry matter were recorded in C₄ - pendimethalin 0.75 kg ha⁻¹ fb mechanical weeding (Table 12.4).

Table 12.4 Effect of different doses of herbicide on soil total nodule No and total dry matter (mg/plant) in maize-chickpea cropping system

Herbicide in the present investigation had only temporary effect on soil health parameter. The herbicide used, i.e., atrazine and pendimethalin, 2,4-D in maize-chickpea cropping system, did not lower the basal soil respiration and microbial biomass production of microbes at the harvest time of the crop. Similar results regarding beneficial microflora were found. Increasing trend in number of colonies was found from initial to harvest. Application of herbicide did not restrict the microbial growth in both the crops. There is nonsignificant effect of herbicide on number of root nodules and nodule dry matter. Total number of “N” fixers was observed more than that of “P” solubilizers.