Crop residue chemistry, decomposition rates, and CO₂ evolution in Bt and non-Bt corn agroecosystems in North America: a review
2010
Yanni, S. F. | Whalen, J. K. | Ma, B. L.
Corn (Zea mays L.) is a major cereal crop, with production on more than one-fifth of the agricultural land worldwide. In North America, about 50% of corn acreage is planted with transgenic corn hybrids such as those with the gene from Bacillus thuringiensis (Bt) that express the insecticidal crystalline protein (Cry1Ab) for the control of European corn borer (ECB, Ostrinia nubilalis Hubner). Widespread production of Bt corn could affect soil organic carbon (SOC) storage in agroecosystems if transgenic corn differs from conventional corn in yield and chemical composition. Generally, the yield of Bt corn is greater than non-Bt corn in years when there is severe infestation of corn insect pests. Some authors report that Bt corn has higher lignin content than non-Bt corn, whereas others found no difference in the chemical composition of near isolines. Residues with higher lignin content are expected to have a slower decomposition rate and release less CO₂ to the atmosphere; however, this is not supported by the literature. A few studies have examined decomposition of Bt corn residues in this context, and the findings to date have been inconclusive, perhaps due to the variety of experimental approaches used to study this question. Generally, the literature supports the view that decomposition rates in Bt corn- and non-Bt corn-amended soils are similar. Whether Bt corn has greater lignin content or slower decomposition rates, the relevant question is whether this will affect the amount of C storage in the soil. A significant gain in SOC requires crop residue inputs with higher lignin content than what is realistically expected from Bt corn residue.
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