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Title: Glufosinate and Ammonium Sulfate Inhibits Atrazine Degradation in Adapted Soils

item Zablotowicz, Robert
item Krutz, Larry
item Weaver, Mark
item Reddy, Krishna

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2008
Publication Date: 10/1/2008
Citation: Zablotowicz, R.M., Krutz, L.J., Weaver, M.A., Accinelli, C., Reddy, K.N. 2008. Glufosinate and Ammonium Sulfate Inhibits Atrazine Degradation in Adapted Soils. Biology Fertility Soils 45:19-26.

Interpretive Summary: Atrazine is the second most utilized herbicide in North America primarily in corn production, thus understanding how to manage its fate in soil and control weeds efficiently is important to crop production. These studies were conducted to assess how two inputs for corn production the herbicide glufosinate and ammonium fertilizer affect the persistence of atrazine in soil. Application of one- to four-times standard rate of glufosinate temporarily slowed down atrazine degradation rates. However, commercial rates of ammonium fertilizer had a greater effect in maintaining atrazine in soil. Co-application of both glufosinate and ammonium fertilizer had additive effects on increasing atrazine persistence in soil. Co-application of nitrogen fertilizer and glufosinate simultaneously with atrazine may improve the effectiveness of weed control by atrazine.

Technical Abstract: The co-application of glufosinate with nitrogen fertilizers may alter atrazine co-metabolism, thereby extending the herbicide’s residual weed control in adapted soils. The objective of this study was to assess the effects of glufosinate, ammonium sulfate, and the combination of glufosinate and ammonium sulfate on the persistence of atrazine in a Dundee silt loam exhibiting enhanced atrazine degradation. Application of glufosinate at rates of 10 to 40 mg kg-1 soil extended the lag-phase one to two days and reduced the maximum degradation rate by 15 to 30%. However, cumulative atrazine mineralization averaged 85% 21 days after treatment and was independent of treatment. Maximum daily rates of atrazine mineralization were reduced from 41 to 55% by application of 1 to 8 g kg-1 of ammonium sulfate. Similarly, cumulative atrazine mineralization was inversely correlated with ammonium sulfate rates ranging from 1.0 to 8 g kg-1 soil. Under the conditions of this laboratory study, the atrazine-degrading population(s) was relatively insensitive to exogenous mineral nitrogen, in that 8 g (NH4)2 SO4 kg-1 soil repressed but did not completely inhibit atrazine mineralization. Moreover, an additive effect on reducing atrazine mineralization was observed when glufosinate was co-applied with ammonium sulfate. In addition, ammonium fertilization alters the partitioning of 14C-atrazine into altered metabolite accumulation and non-extractable residues, indicating that ammonium represses cleavage of the triazine ring. Consequently, results indicate that the co-application of glufosinate with N may increase atrazine persistence under field conditions thereby extending atrazine residual weed control in adapted soils.