Effect of Herbicide residues on Soil Microorganisms in Turmeric

E. Sathiyavani<sup>1</sup>; N. K. Prabhakaran<sup>2</sup>; C. Chinnusamy<sup>3</sup>; R. Shanmugasundram<sup>2</sup>; K. Soorianathsundaram<sup>4</sup>

Effect of Herbicide residues on Soil Microorganisms in Turmeric

E. Sathiyavani¹

, N. K. Prabhakaran²

, C. Chinnusamy³

, R. Shanmugasundram²

, K. Soorianathsundaram⁴

1. Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, INDIA
2. Professor, Department of Soil Science & Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, INDIA
3. Dean, Tamil Nadu Agricultural University, Madurai, Coimbatore, Tamil Nadu, INDIA
4. Professor, Department of Horticulture, HC & RI, TNAU, Coimbatore, Tamil Nadu, INDIA

Author

Correspondence author
International Journal of Horticulture, 2015, Vol. 5, No. 3 doi: 10.5376/ijh.2015.05.0003
Received: 18 Feb., 2015 Accepted: 03 Mar., 2015 Published: 12 Mar., 2015

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Preferred citation for this article:

Sathiyavani et al., 2015, Effect of Herbicide residues on Soil Microorganisms in Turmeric, International Journal of Horticulture, 2015, Vol.5, No.3 1-12 (doi: 10.5376/ijh.2015.05.0003)

Abstract

Field investigation were undertaken to evaluate the integratedweed management with pre and post emergence herbicides in turmeric at the Agricultural Research Station, Bhavanisagar of Tamil Nadu Agricultural University, during kharif season of 2012 and to elucidate information on bacterial, fungal and actinomycetes population due to the effect of herbicide residues. The bacterial, fungal and actinomycetes populations were recorded at 3, 15, 25, 50 and 75 DAP. The experiments were laid out in Randomized block design with three replications. The treatments comprised of different weed management practices wherein PE herbicides viz., metribuzin 0.7 kg ha^‑1, pendimethalin 1.0 kg ha^‑1 andatrazine 0.75 kg ha^‑1 followed by either POE fenoxaprop 67 g ha^‑1 + metsulfuron 4 g ha^‑1 (Tank mix) on 45 DAP or HW on 45 and 75 DAP or straw mulch 10 t ha^‑1 on 10 DAP + HW on 75 DAP, all PE oxyfluorfen 0.30 kg ha^‑1, PE oxadiargyl 0.25 kg ha^‑1, POE glyphosate 1.03 kg ha^‑1 and 1.54 kg ha^‑1 on 25 DAP followed by HW on 45 and 75 DAP, HW on 25, 45 and 75 DAP and unweeded check were imposed. In both the experiments, observations were recorded on soil microorganisms viz., populations of bacterial, fungal and actinomycetes were observed at different days after planting of rhizome. In this experiments showed herbicide application of PE metribuzin 0.7 kg ha^-1,PE pendimethalin 1.0 kg ha^-1, PE atrazine 0.75 kg ha^-1,PE oxyfluorfen 0.3 kg ha^-1 and PE oxadiargyl 0.25 kg ha^-1 recorded significantly lower microbial population immediately after herbicide spraying (3 DAP) than the treatments not having any herbicides and thereafter increased.

Keywords

Herbicide residues; Soil microbial populations; Turmeric

Turmeric (Curcuma longa L.), a herbaceous perennial plant, belonging to the family Zinziberaceae under the order Scitaminae is one of the most valuable spices all over the world. It is also called as “Indian saffron”. Turmeric (Curcuma longa L.) is one of the second most important spice crops after chilli. India accounts for 78 per cent in world production and 60 per cent in world export share (Angles et al.,2011). Among the several spices, turmeric ranks second in foreign exchange earning, being next only to chilli. The turmeric is native of South-East Asia, cultivated extensively in India, Myanmar, Nigeria, Pakistan, Sri Lanka, Indonesia, Bangladesh, Taiwan and China. The major states in India which grow turmeric are Andhra Pradesh, Orissa, Tamil Nadu, Assam, Maharashtra and Karnataka. Andhra Pradesh alone occupies 35 per cent of area and 47 per cent of production. In Tamil Nadu, it is grown in the districts of Erode, Coimbatore, Dharmapuri and Salem. Erode district alone contributes more than 10 per cent of the national production (Kandiannan and Chandaragiri,2004). Indian turmeric is regarded as the best in the world market because of its high curcumin content. During the periods between April 2011 to January 2012, the turmeric export from India was 67, 000 tonnes valued at 6438 million and contributed to 12.8 per cent of total spice export (Satya Sundaram, 2012). Though, India leads in production of turmeric with 78 per cent of global production, its average productivity is quite low, mainly due to the competition offered by weeds. Weeds are the most severe and widespread biological constraint to crop production and cause invisible damage till the crop is harvested. Heavy infestation of weeds comprising of grasses, sedges and broadleaved weeds poses a big challenge for turmeric production in India.

Herbicides are the key products in sustaining large scale agricultural production but in order to minimize agro-environmental concerns regarding their use, continued assessment of their behaviour under different management practices is required. Chemical weed control is a better supplement to conventional method and forms an integral part of the modern crop production. It is quick, more effective, time and labour saving method than others (Tahir et al., 2009). Presently a number of herbicides like pendimethalin, metribuzin and oxyfluorfen etc. are commercially available for weed control in turmeric.

Herbicides are extraneous to soil component pools, and are expected to affect the catalytic efficiency, behavior of soil enzymes (Bollag and Liu, 1990; Sannino and Gianfreda, 2001), which contribute to the total biological activity of the soil-plant environment under different states (Dick, 1995; Dick, 1997). The interaction between herbicides and soil microorganisms may be of practical significance because of possible inhibition in microbial activities contributing to soil fertility. Various studies have revealed that the herbicides can cause qualitative and quantitative change in enzyme activity (Sannino and Gianfreda, 2001; Min et al., 2001; Saeki and Toyota, 2004; Sebiomo et al., 2011, Xia et al., 2011). Hence, the effects of herbicides on soil microbial communities addressing the apprehensions about the environmental impacts of herbicide use. Several scientific investigations have suggested the importance of preserving soil fertility and quality, and consequently soil microbial population. As the soil microorganisms are very sensitive to low concentrations of contaminants and rapidly response to soil perturbation, they are considered as an indicator of soil pollution (Shen et al., 2005). The enzyme activities are considered to be sensitive to chemical pollutants/agrochemicals and have been proposed as potential indicators for measuring the degree of pollution of contaminated soil (Aoyama and Nagumo, 1995; Insam et al., 1996; Kuperman and Margret, 1997), and referred to as markers of soil environmental purity (Aon and Colaneri, 2001). The evaluation of soil enzyme activities may provide useful information on microbial activity and be helpful in establishing the effects of soil specific environmental conditions (Andreoni et al., 2004). An alternation in soil microorganisms, their number, activity and diversity may serve as indicators of soil fertility (Milosevia et al., 1997) and reflect the soil quality (Schloter et al., 2003). However, most of the studies were focused on single application for a short period, which may provide a realistic evaluation of the effects of herbicides on soil microorganism (Haney et al., 2000). However, the knowledge about the effect of herbicides on soil microbial population in long-term applications has been limited. Being a long duration crop, pre-emergence herbicides alone will not provide a sustainable and effective weed management. Based on the above constraints, we are taken the objective of study the efficacy of pre and post emergence herbicides in IWM on weed control and herbicide residues effect in soil microbial populations of turmeric.

Materials and Methods

Field experiments were carried out during kharif 2012 at Agricultural Research Station, Bhavanisagar of Tamil Nadu Agricultural University, to evaluate the integratedweed management with pre and post emergence herbicides in turmeric. The details of the experiment, the materials used and the methods employed during the course of investigation are presented in this chapter.

Soil characteristics

Composite soil sample was collected at random prior to the experiment, pooled and analysed for physico- chemical characteristics. The soil of the experimental field was red sandy loam in texture belonging to Typic Haplustalf. The nutrient status of the field was low in available nitrogen, medium in available phosphorus and high in available potassium. The detailed physico-chemical properties of the experimental field are furnished in Table 1.

Table 1 Physico-chemical characteristics of the experimental fields

Season

The experiments were conducted during kharif (May-June) season, 2012.

Crop and variety
Turmeric variety BSR 2 with a duration of 240-245 days was selected for this study and the seeds were procured from ARS, Bhavanisagar. The characteristic features of the variety BSR 2 are presented in Table 2.

Table 2 Varietal characteristics of turmeric BSR 2

Experimental Methods

Design and layout

The experiments were laid out in Randomized block design comprised of fifteen treatments. The treatments were replicated thrice. The lay out plan of the experimental field during 2012. The experimental details are furnished below.

Experimental details

Particular	Kharif-2012
Variety	BSR 2
Spacing	45 cm ´ 15 cm
Gross plot	6.0 m ´ 4.5 m
Net plot	5.7 m ´ 3.6 m
Date of sowing	29.06.2012
Date of harvest	15.03.2013

Treatment details

Treatment

T₁	-	PE metribuzin 0.7 kg ha^-1 + HW on 45 and 75 DAP
T ₂	-	PE metribuzin 0.7 kg ha^-1 + POE fenoxaprop 67 g ha^-1 + metsulfuron 4 g ha^-1 (Tank mix) on 45 DAP
T ₃	-	PE metribuzin 0.7 kg ha^-1 + straw mulch 10 t ha^-1 on 10 DAP + HW on 75 DAP
T ₄	-	PE pendimethalin 1.0 kg ha^-1 + HW on 45 and 75 DAP
T ₅	-	PE pendimethalin 1.0 kg ha^-1 + POE fenoxaprop 67 g ha^-1 + metsulfuron 4 g ha^-1 (Tank mix) on 45 DAP
T ₆	-	PE pendimethalin 1.0 kg ha^-1+ straw mulch 10 t ha^-1 on 10 DAP + HW on 75 DAP
T ₇	-	PE atrazine 0.75 kg ha^-1 + two HW on 45 and 75 DAP
T ₈	-	PE atrazine 0.75 kg ha^-1 + POE fenoxaprop 67 g ha^-1 + metsulfuron 4 g ha^-1 (Tank mix) on 45 DAP
T ₉	-	PE atrazine 0.75 kg ha^-1 + straw mulch 10 t ha^-1 on 10 DAP + HW on 75 DAP
T ₁₀	-	PE oxyfluorfen 0.30 kg ha^-1 + HW on 45 and 75 DAP
T ₁₁	-	PE oxadiargyl 0.25 kg ha^-1 + HW on 45 and 75 DAP
T ₁₂	-	POE glyphosate 1.03 kg ha^-1 on 25 DAP + HW on 45 and 75 DAP
T ₁₃	-	POE glyphosate 1.54 kg ha^-1 on 25 DAP + HW on 45 and 75 DAP
T ₁₄	-	Hand weeding on 25, 45 and 75 DAP
T ₁₅	-	Unweeded check

Note: PE - pre-emergence POE - post-emergence DAP - days after planting HW- hand weeding

Microbial analysis

Population dynamics of different types of microorganisms was studied from the soil samples of individual treatment plots at 3, 15, 25, 50 and 75 DAP. One gram of soil was weighed and transferred to 10 ml sterile water blank and a thorough shaking was given. This gave the dilution of 10^-1, from this using a sterile pipette, one ml of the suspension was transferred to 9 ml water blank to get a dilutionof 10^-2. Subsequent dilution of10^-3, 10^-4, 10^-5, and 10^-6 were also made accordingly. The respective media were melted, cooled and poured into the petri-dishes carrying the respective dilution and the dishes were incubated at 30°C. After incubation period, the colonies were counted and expressed as colony forming units per gram of soil. Media used for the estimation of population dynamics of different microbial communities are furnished below:

Composition of media used

Herbicide residue analysis

The samples were collected from turmeric field at harvest to determine the residue of the herbicides. Soil and turmeric rhizome samples were collected for each chemical. The protocol details of each herbicide chemicals are furnished below:.

Method employed for the determination of herbicides residue in soil and turmeric rhizome

Extraction and analysis of metribuzin

10 g of air dried and 2-mm sieved soil and finely chopped rhizome samples were transferred into 60 mL cylindrical tubes. Metribuzin residue was extracted with 10 ml of acidified acetonitrile (with formic acid) and 10 ml of methanol by shaking and vertexing for 2 minutes and then sonicating for 30 min. After sonication 1.8 g of MgSO₄ and 2 g of Na acetate was added and sample mixture was vigorously shaken for 2 minutes and then centrifuged for 5 min @ 5000 RPM. A 2 ml portion of supernatant solution was filtered using syringe filter for HPLC analysis.

Instrumental conditions

Instrument	HPLC with DAD (Agilent 1200 series)
Mobile phase	Acetonitrile :Distilled water 70/ 30 v/v
Flow rate	0.5 mL min^-1
Wave length (nm)	230
Injection volume	20 µl (using auto sampler)
Temperature	30^oC
Column	Eclipse XDB C₁₈ (5cm, 4.6 x 150 mm)
Retention time	5.32 min (±0.2 min)

Extraction and analysis of pendimethalin

Pendimethalin was extracted from the soil and rhizome samples withmethanol and the extract was filtered and evaporated at 60°C to about 10 ml. The concentrated extract was transferred to separatory funnel and 30 ml of 5 % aqueous NaCl was added. The contents were partitioned with n-hexane passed through anhydrous sodium sulphate. Hexane layer was concentrated on rotary vacuum evaporator at 60°C to approximately 5 ml and quantified by Gas Chromatograph (GC-Chemito Model 8610) equipped with ⁶³Ni electron capture detector.

Instrumental conditions

Detector	Electron capture detector
Column	Megabore capillary column D13-30 m × 0.53 mm ID-BPL 0.5 µm
Injector	240^oC
Column	185-220^oC
Detector	260^oC
Carrier gas flow rate	40 ml min^-1
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