Abstract: By using litterbag method, this paper studied the degradation of Bt protein released from Cry1Ab Bt corns 1246×1482 and H9235Bt/RR under two straw return patterns, i.e., buried in soil and covered on soil surface, and the DT50 and DT90 were fitted and estimated by shift-log model. Under the two straw return patterns, more than 90% of the Bt protein from the two Bt corns were degraded within one week, only 0004%〖KG-*2〗-〖KG-*7〗0069% of their initial Bt protein being detected after the Bt corn straws returned to field for 180 days. Less difference was observed in the degradation of Bt protein from Bt corn 1246×1482 under different straw return patterns, with the DT50 and DT90 being 090 d and 345 d when the straws were buried in soil, and 079 d and 503 d when covered on soil surface, respectively. However, the degradation of Bt protein from H9235Bt/RR was manifestly affected by the straw return pattern. At the early stage of straw return, the degradation rate of Bt protein from H9235Bt/RR was lower when the straws were buried in soil than covered on soil surface, with DT50 and DT90 being 680 d and 2176 d, and 054 d and 712 d, respectively. It was suggested that the Bt protein both from Bt corn 1246×1482 and from H9235Bt/RR could be degraded rapidly in field, and straw return pattern only affected the degradation of Bt protein from H9235Bt/RR, with a much higher degradation rate when the straws were covered on soil surface.

Key words: Simulated acid rain, Soluble sugar, Nitrogen content, Photosynthetic rate, Nitrate reductase