Development of Ecologically Acceptable Chlorpyrifos Formulation for Effective and Safe Application

Application of the commercial formulation of chlorpyrifos has resulted in considerable environmental contamination. This study was designed to develop environmentally acceptable chlorpyrifos formulation for safe and effective application. This involved the modification of clay surfaces from hydrophilic to hydrophobic via ion-exchange reaction with organic cations. The resulting organo-clay complexes were tested for adsorption and release of chlorpyrifos. HPLC and FTIR measurements showed considerable adsorption and strong interaction between chlorpyrifos molecules and the organo-clay complexes. Basal spacing results emphasized the formation of suitable micro-pores for chlorpyrifos molecules. HPLC and bioassay techniques confirmed the slow release of chlorpyrifos. Leaching potential showed retention of chlorpyrifos in the top soil. Therefore application of organoclay formulation of chlorpyrifos may reduce their potential environmental contamination and produce safe applications.

Sugarcane bagasse amendment mitigates nutrient leaching from a mineral soil under tropical conditions

Large quantities of organic by-products are generated by the sugarcane industry during sugar extraction process.These by-products may be used as soil amendments to improve soil quality,as nutrient leaching is common in mineral soils of Florida in USA due to their sandy texture and frequent rain events.A soil column study was designed to evaluate the effects of bagasse application at 85 t ha^(-1) of fresh bagasse,170 t ha^(-1) of fresh bagasse,and 170 t ha^(-1) of fresh bagasse+nitrogen(N)on the leaching potential of carbon(C),N,phosphorus(P),and potassium(K).Bagasse was incorporated within the topsoil(0-15 cm)in outdoor soil columns exposed to natural conditions,with periodical irrigation during the experiment.After approximately 57 weeks,the distributions of C,N,P,and K were evaluated at three soil depths(i.e.,0-15,15-30,and 30-53 cm)within the soil columns.Total organic C(TOC),N,and P in leachates decreased significantly from the soils amended with bagasse compared with the control with no bagasse and no N.Based on K content changes in the columns,bagasse could also be utilized as a potential source of K for plants.Overall,application of bagasse as a soil amendment might be an effective way to sustainably reutilize organic by-products while reducing concerns regarding major nutrients entering groundwater resources.The results of this study could assist in developing nutrient management plans of using sugarcane bagasse as a potential soil amendment in mineral soils.

Influence of pyrolysis temperature on rice straw biochar properties and corresponding effects on dynamic changes in bispyribac-sodium adsorption and leaching behavior in soil

Bispyribac-sodium is a weakly acidic herbicide with high water solubility and is thus a potential source of groundwater contamination.Considering the risk inherent to the use of this herbicide,this study assessed the impacts of rice straw(RS)and biochar amendments on the adsorption and leaching behavior of bispyribac-sodium in soil.Biochars were produced from RS at different pyrolysis temperatures and characterized using various spectral techniques.Rice straw had a surface area of 3.996×10^(4)m^(2)kg^(-1),which increased under pyrolysis;biochars prepared at 350 and 550℃(RS350 and RS550)in a closed furnace with limited oxygen supply had a surface area of 5.763×10^(4)and 6.890×10^(4)m^(2)kg^(-1),respectively,and biochar prepared by purging the pyroformer with N2(RSC)had the highest surface area of 12.173×10^(4)m^(2)kg^(-1).After amendment with RS and biochar,soil Freundlich adsorption capacity(KF ads)increased to varying extents in the order RSC>RS350>RS550,from 2.89×10^(3)to 29.57×10^(3)mg^(1-1)/nkg^(-1)L1/n,compared to1.55×10^(3)mg^(1-1)/nkg^(-1)L1/nin unamended soil.The variability in KF ads of bispyribac-sodium amongst the RS-and biochar-amended soils was dependent on the surface area of the amendments.The desorption of bispyribac-sodium decreased in the RS-and biochar-amended soils and varied from90.45%to 95.20%in unamended soils and from 60.95%to 89.50%in amended soils.The adsorption and desorption of bispyribac-sodium varied significantly depending on its concentration and the type and application rate of soil amendment.Different leaching risk evaluation indices,viz.,modified leach index(M.LEACH),leach index(LEACH),groundwater ubiquity score(GUS),Hornsby index(HI),leaching index(LIN),and pesticide leaching potential(PLP)index,were used to assess the susceptibility of groundwater to herbicide leaching.To reduce the repetitive effects of common parameters in each index,a new index was developed by employing principal component analysis(PCA)to condense their information into a single ranking.The results of the PCA indicated that RS and biochar amendments could be an effective management practice for controlling the leaching potential of bispyribac-sodium in soil.