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CROP ECOLOGY, MANAGEMENT & QUALITY

Dry Matter and Nitrogen Partitioning Patterns in Bt and Non-Bt Near-Isoline Maize Hybrids

Eastern Cereal and Oilseed Research Center (ECORC), Central Experimental Farm, Research Branch, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, ON, Canada K1A 0C6

^* Corresponding author (subedik{at}agr.gc.ca).

While maize (Zea mays L.) hybrids with the Bt transgene from Bacillus thuringiensis have been gaining popularity, their dry matter (DM) production, N uptake, and whole-plant N dynamics have not been assessed to justify their added cost. A field experiment conducted for 2 yr in Ottawa, Canada, studied DM and N partitioning patterns, and N-use efficiency (NUE) of a conventional (Pioneer 3893) and its near-isoline transgenic hybrid (Pioneer 38W36 Bt). The hybrids were grown with two N treatments (0 kg N [N0] or 150 kg N ha^–1 with ¹⁵N-labeled source [N150]). Plant samples were analyzed for DM, N concentration, and the fate of ¹⁵N at the V7, silking, and physiological maturity (PM) stages. Both hybrids were similar in harvest index, leaf chlorophyll content, and N concentrations and contents at the V7, silking, and PM stages. The Bt hybrid produced greater DM in leaves (42.1 vs. 37.5 g plant^–1) and kernels (134 vs. 121 g plant^–1) than its non-Bt counterpart, it also accumulated about 11% more N in kernels and on a whole-plant basis. Both hybrids had a similar partitioning of N and NUE in different plant parts. About 47% of the applied N was recovered at harvest, 70% of which was accumulated in the kernels of both hybrids. There was no indication that the Bt hybrid accumulated more N than its non-Bt near-isoline until the silking stage; the greater N content of the Bt hybrid at the PM stage was associated with greater DM in the kernels and leaves.

Abbreviations: a.e., atom enrichment • Bt, Bacillus thuringiensis • DM, dry matter • ECB, European corn borer • NUE, nitrogen use efficiency • PM, physiological maturity.