Pervinder Kaur

Effect of repeated application of pendimethalin on its persistence and dissipation kinetics in soil under field and laboratory conditions

ABSTRACT The repeated application of herbicide can alter its persistence in the environment. In India, wheat fields are exposed to herbicide application at least once in the cropping season. The present study investigated the dissipation behavior of pendimethalin applied annually to a wheat field over four cropping seasons from 2012 to 2016. The dissipation studies were also conducted under laboratory conditions during 2015–2016. Pendimethalin from soil and wheat grain samples was extracted using matrix solid-phase dispersion and quantified using high-performance liquid chromatography and gas chromatography–tandem mass spectrometry. The average recoveries of pendimethalin from soil and crop produce ranged from 81.3% to 103.1%. The half-life of pendimethalin ranged from 20.9 to 31.3 days and 9.4 to 60.2 days under field and laboratory conditions, respectively. Dissipation of pendimethalin varied significantly over the years under field conditions and was comparatively faster than under laboratory conditions. On the other hand, non-significant variation in the dissipation of pendimethalin in soils under laboratory conditions was observed. The residues of pendimethalin in crop produce at harvest were below the maximum residue limit set by EPA.

Comparison of extraction techniques for quantitative analysis of pendimethalin from soil and rice grain

ABSTRACT The paper exploits the development, optimization, and comparison of fast, efficient, quantitative analytical extraction techniques such as ultrasonic-assisted extraction (UAE) and matrix solid-phase dispersion (MSPD) for proficient extraction of pendimethalin from soil and rice samples. Residues of pendimethalin were quantified using high-performance liquid chromatography. Impact of several experimental parameters of UAE and MSPD techniques on extraction of pendimethalin from soil and rice samples was also evaluated. Under the optimized conditions, the mean percent recoveries obtained from both methods were in the range of 80.3–101.3 and 81.7–103.1, respectively, with relative standard deviation <10. Linearity was in the range of 0.003–5.0 µg mL−1 with limit of detection and limit of quantification as 0.001 and 0.003 µg g−1, respectively. MSPD method was found superior in terms of low solvent consumption, small sample size, and reduced matrix coextracts due to simultaneous extraction and cleanup steps. Both extraction methodologies were successfully applied in monitoring routine soil and rice samples, in which pendimethalin residues (0.003–0.007 µg g−1) were detected in few rice samples while residues in soil samples were below the quantification limit. GRAPHICAL ABSTRACT

Time and temperature dependent adsorption-desorption behaviour of pretilachlor in soil

Understanding and quantifying the adsorption-desorption behaviour of herbicide in soil is imperative for predicting their fate and transport in the environment. In the present study, the effect of time and temperature on the adsorption-desorption behaviour of pretilachlor in soils was investigated using batch equilibration technique. The adsorption-desorption kinetics of pretilachlor in soils was two step process and was well described by pseudo-second-order kinetic model. Freundlich model accurately predicted the sorption behaviour of pretilachlor. The adsorption-desorption of pretilachlor varied significantly with the concentration, temperature and properties of soil viz. organic matter and clay content. All the studied soils had non-linear slopes (n < 1) and degree of nonlinearity increased with increase in clay, organic matter content and temperature (p < 0.05). Desorption of pretilachlor was hysteretic in studied soils and hysteresis coefficient varied from 0.023 to 0.275. Thermodynamic analysis showed that pretilachlor adsorption onto soils was a feasible, spontaneous and endothermic process which becomes more favourable at high temperature. It could be inferred that the adsorption of pretilachlor on soils was physical in nature.

Quantification of flufenacet residues in soil and wheat grain

The terminal residues of flufenacet were quantified in soil and wheat grains. Flufenacet was applied at 250 and 300 g/ha on 21 and 35 days after the sowing of wheat at the Research Farm of Punjab Agricultural University, Ludhiana. Matrix solid phase dispersion (MSPD) method was used for the extraction of flufenacet from soil and grain samples. The herbicide residues were quantified using High Performance Liquid Chromatography (HPLC) equipped with UV-Vis detector and were confirmed with gas chromatographic tandem mass spectrometry (GC-MS/MS). The average recoveries of flufenacet extracted from the matrix ranged from 80.9 to 93.0% and 88.0 to 96.2% when quantified using HPLC and GC-MS/MS, respectively with relative standard deviation less than 10%. Both HPLC and GC-MS/MS offer high reproducibility, however GC-MS/MS was more sensitive having limit of detection (LOD) and limit of quantification (LOQ) as 0.001 and 0.003 μg/g, respectively. Terminal residues of flufenacet in the soil and wheat grain samples were below the detectable limit. Thus, the use of flufenacet in wheat under sub-tropical humid conditions could be considered safe.

Effect of long-term application of pretilachlor on its persistence and residues in paddy crop

ABSTRACT The effect of long-term application of pretilachlor to paddy in rice–wheat cropping system was investigated from 1997 to 2015. Additionally, in 2013, field experiment was also conducted where pretilachlor was applied to paddy field having no background of its application. The residues of pretilachlor were quantified using high-performance liquid chromatography (HPLC). The average recoveries of pretilachlor from paddy soil, paddy grain and straw samples ranged from 80.7% to 93.8% using HPLC with standard deviation less than 10%. The dissipation rate of pretilachlor in paddy soil followed first-order kinetics and half-life ranged from 9.58 to 21.19 days. In 2015, HPLC was compared with gas chromatography–tandem mass spectrometry (GC–MS/MS) for quantification of residues. Average recoveries of pretilachlor using GC–MS/MS from paddy soil, paddy grain and straw samples ranged from 81.4% to 98.3% with standard deviation less than 10%. Both HPLC and GC–MS/MS offered high reproducibility; however GC–MS/MS was more sensitive and the limit of detection was 3.0 and 1.0 ng g−1 for HPLC and GC–MS/MS, respectively. At harvest, the residues of pretilachlor in the paddy soil and crop were below the maximum residue limit and no dangerous accumulation was observed after its prolonged application.

Screening of Basmati Rice Varieties for their Arsenic Accumulation in Punjab, North-West India

ABSTRACT A pot study was conducted to screen different basmati rice varieties for their accumulation of arsenic (As). Different amounts of arsenic (0–800 µg/L) were applied through irrigation water to four basmati rice varieties (Pusa basmati-1121, Pusa Punjab basmati-1509, Punjab basmati-2, and Punjab basmati-3). Highest arsenic concentration was found in the grains of Punjab basmati-3 and lowest in the grains of Pusa Punjab basmati-1509. In all varieties, grain As concentration ranged from 0.038 to 0.288 mg/kg, which was within the permissible limit of 1.0 mg/kg in rice grain recommended by World Health Organization (WHO). In husk, highest As concentration was found in Pusa basmati-1121 and lowest in Punjab basmati-2. Among the four varieties, highest content of As was accumulated in roots and straw of Pusa Punjab basmati-1509, whereas least was accumulated in Punjab basmati-2. The distribution of arsenic among plant parts was found in the order: roots > straw > husk > grain. The mean arsenic concentrations in grain, husk, straw, and root of basmati rice varieties increased with increasing concentration of arsenic in irrigation water. Highest grain yield was obtained in Pusa Punjab basmati-1509 variety due to lesser accumulation of arsenic compared with other varieties. Rice yield, plant height, root weight, straw weight, test weight, effective tiller, and filled grain per panicle decreased with increase in arsenic concentration in irrigated water.

Herbicide resistance in weeds and its management

Repeated use of herbicides with similar modes of action for weed control in wheat has resulted in evolution of multiple herbicide resistance in Phalaris minor, which could threaten the sustainability of the rice-wheat cropping system in north-western India. Herbicide resistance could also become a problem in direct seeded rice and soybean crops, which rely heavily on acetolactate synthase (ALS) and acetyl coenzyme A carboxylase (ACCase) inhibiting herbicides. As discovery of new herbicide modes of action has slowed dramatically, all effort should be made to increase the effective life of existing herbicides and make weed management cost-effective and efficient. Early detection of resistance can facilitate timely adoption of alternative tactics and minimise the financial impact on farmers. Structured surveys of resistance affected areas can provide required information for site-specific recommendations as expression of herbicide resistance tends to be highly site-specific. Greater emphasis is needed on weed management systems based on sound knowledge of weed ecology. Refinement is needed in seeding machinery for high residues systems, improvements in equipment for inter-row cultivation and application technology of herbicides. Farmer-participatory research and adoption of improved agronomy could delay evolution of resistance in weeds and enhance the sustainability of Indian cropping systems. This paper has reviewed and discussed herbicide resistance in weeds in Indian context.