Effect of repeated applications of buprofezin and acephate on soil cellulases, amylase, and invertase M. Naga Raju & K. Venkateswarlu Received: 17 December 2013 /Accepted: 21 May 2014 /Published online: 29 May 2014 # Springer International Publishing Switzerland 2014 Abstract The impact of repeated applications of buprofezin and acephate, at concentrations ranging from 0.25 to 1.0 kg ha -1 , on activities of cellulases, amylase, and invertase in unamended and nitrogen, phosphorous, and potassium (NPK) fertilizer- amended soil planted with cotton was studied. The nontarget effect of selected insecticides, when ap- plied once, twice, or thrice on soil enzyme activities, was dose-dependent; the activities decreased with increasing concentrations of insecticides. However, there was a rapid decline in activities of enzymes after three repeated applications of insecticides in unamended or NPK-amended soil. Our data clearly suggest that insecticides must be applied judiciously in pest management in order to protect the enzymes largely implicated in soil fertility. Keywords Buprofezin . Acephate . Soil enzymes . NPK amendments Introduction Major problem that arises consistently in modern agriculture is that different groups of pesticides, either simultaneously or in succession, are applied for an effective control of a variety of major pests. The most widely used pesticides belong to the organophospho- rous (OP) group and account for an estimated 34 % of worldwide insecticide sales (Singh and Walker 2006). During the last 60 years, approximately 150 different OP chemicals have been used to protect crops, livestock, and human health (Casida and Quistad 2004). It is obvious that the application of pesticides results in their accumulation as residues in soil, which is the ultimate sink of all these xenobiotic compounds. It has long been known that pesticide applications at recommended rates have little or no effect on enzyme activity in soils (Nannipieri 1994; Rangaswamy et al. 1994; Ramakrishnan et al. 2010, 2011). Numerous reports, however, have indicated that soil enzyme activities were significantly affected when pesticides were applied to soil with higher than recommended rates over long periods (Sannino and Gianfreda 2001; Megharaj 2002; Wyszkowska and Kucharski 2004). Cotton is an important fiber-yielding crop of global importance which is grown in tropical and subtropical regions of more than 80 countries over the world. In recent decades, there is a serious concern about the vast economic damage caused to cotton by many insect pests. Although several insecticides are used on need basis for the effective control of the insect pests on cotton, two insecticides, particularly buprofezin (Applaud®) and acephate (Hythene®) are widely used along with nitrogen, phosphorous, and potassium (NPK) fertilizers in the recent years. Although data exist for other pesticides, virtually, no information is available Environ Monit Assess (2014) 186:6319–6325 DOI 10.1007/s10661-014-3856-9 M. N. Raju (*) Universidad Estatal Amazonica, 160150 Puyo, Ecuador e-mail: mnraju8875@gmail.com K. Venkateswarlu Sri Krishnadevaraya University, Anantapur 515003, India