In this study, differences in rates of decomposition and biomass fraction contents were observed for leaf, stalk, and cob plant parts. Differences in total C, total N, and biomass fractions of the initial Bt and non-Bt hybrid plant materials did not correspond to differences in rates of decomposition. The difference in rate of stalk decomposition was more likely a result of varietal differences rather than the Bt gene, according to USDA researchers.

Microorganisms that cause decay of corn stalks work best if the carbon to nitrogen ratio is less than 30. Most conventional corn hybrids have a ratio less than 30 and most Bt-containing corn hybrids have a carbon to nitrogen ratio higher than 30.

Adding extra nitrogen to speed the decaying process is a natural solution, but the high cost of nitrogen and the time and cost of application has left many farmers wondering how much nitrogen to use and how and when to apply it.

It is widely accepted that wet soils can lead to nitrogen losses. If so, could leaving Bt-containing corn stalks in wet fields further speed the loss of N? The continued increase in the use of Bt corn, and of the renewed popularity of corn in general seem to indicate a need among corn growers in the Southeast to take a look at the potential problem prior to planting their 2011 crop.

The use of Bt corn isn’t as widespread in the Southeast as it is in the Midwest, but it is growing. Bt corn debuted in 1996, and by 2010 was planted on nearly 60 million of 87 million total corn acres in the U.S.

Other staple crops in the Southeast have shown even more dramatic increases in Bt-containing varieties. It is estimated nearly 75 percent of this year’s cotton crop was planted to Bt-containing genes. Nationwide, over 90 percent of soybeans are Bt-containing varieties.