Degradation of Lindane (γ-HCH) in a Mollisol as Effected by Different Soil Amendments

Soil amendments play an important role in management of pesticide residues. In this study, incubation experiment was conducted using the surface (0 - 15 cm) sample of a mollisol supplied with different soil amendments (farmyard manure, cow-dung slurry, pyrite and gypsum) to investigate the effect of amendments on the dissipation of lindane in mollisols. Dissipation of lindane in soil was studied at eight consecutive samplings (0, 1, 3, 5, 7, 10, 15 and 30 d). The results indicated that soil amendments could promote the degradation of lindane in soil. After 30 d of incubation 79% degradation was observed in the untreated soil (without any amendment) whereas, in the case of farmyard manure and cow-dung slurry amended soils, 83% and 91% degradation was observed, respectively. The pyrite and gypsum amendments also enhanced the degradation of lindane in soils, but the effect was less pronounced as compared to the organic amendments. Enhanced degradation in soil treated with organic amendments could be attributed to stimulated microbial activity after the addition of organic amendments. These addition, under different soil management conditions, minimize the persistence of lindane and consequently the risk of leaching and seepage into aquifers.

Uptake and distribution of ¹⁴C-labeled Fosthiazate in tomato (<i>Lycopersicon esculentum</i>L.)

The uptake of 14C-labeled fosthiazate (0.75 mg.L–1) by tomato plants was studied in solution culture both in the presence or absence of 2, 4 dinitrophenol (DNP, 1 × 10–2 mM), a metabolic inhibitor. Fosthiazate was rapidly taken up by tomato plants and nearly one third of the finally absorbed quantity was taken up in the first half an hour. The translocation of fosthiazate to the shoot part was under metabolic control during the initial stage of uptake. The kinetics of uptake both in the presence and absence of DNP conformed well to the dual phase than a single phase. In the presence of DNP, the uptake capacity (Vmax1) for the initial phase suffered, approximately three fold reduction in comparison to the absence of DNP while Vmax2 for the latter phase was statistically similar to the value observed in the absence of DNP signifying the metabolic dependence of the initial uptake phase. Autoradiography indicated that fosthiazate in the tomato plants tends to accumulate in the roots and at the root-shoot junction. In shoot, it is accumulated in the older leaves especially, near the leaf tip and margins.

Bioefficacy and Residue Studies of Fantac (Biostimulant) in Rice Crop under Sub-Tropical Conditions

Field investigations were conducted for three seasons from July 2006-2007 to test the efficacy of Fantac (N-ATCA) in transplanted rice and also determine its harvest time residues in paddy grain, straw, husk and soil by HPLC. It was applied at the rate of 25, 50, 75 and 100 mL/100 L respectively. The results revealed that foliar spray of this agrochemical on rice crop did not produce any significant effect on the general growth parameters but increased the number of grains/panicle. The residues of fantac were found to be < 0.05 μg/g at the time of harvest which are below MRL and thus Fantac can be considered as environmentally safe.

Role of organic amendments in reducing leaching of sulfosulfuron through wheat crop cultivated soil

A field study with wheat crop was undertaken to examine the efficacy of two soil amendments,cereal straw and fresh cow dung slurry,in reducing leaching of sulfosulfuron to groundwater and its residue load in soil.The herbicide was extracted by the QuEChER’S method and quantified through high performance liquid chromatography.The amendments had no effect on the general properties of groundwater.Both cereal straw and fresh cow dung reduced leaching of sulfosulfuron into groundwater but cereal straw was more effective,probably because its addition decreases soil pH,thereby causing faster hydrolysis of the herbicide.At harvest time,residues of the herbicide in grains,straw and soil were below recommended maximum residue limits(0.1mg kg-1)with both amendments.Thus,both the amendments can be recommended for wheat cropping systems to control sulfosulfuron leaching to groundwater.