Modern maize (Zea mays L.) hybrids coupled with improved agronomic practices may have influenced the accumulation and partitioning of nutrient uptake since the last comprehensive studies were published. The objective of this study was to investigate nutrient uptake and partitioning among elite commercial germplasm with transgenic insect protection grown under modern management practices. Plants were sampled at six growth stages and divided into four fractions for nutrient determination. Total nutrients required per hectare to produce 23.0 Mg ha−1 of total biomass with 12.0 Mg ha−1 of grain included 286 kg N, 114 kg P2O5, 202 kg K2O, 59 kg Mg, 26 kg S, 1.4 kg Fe, 0.5 kg Mn, 0.5 kg Zn, 0.1 kg Cu, and 0.08 kg B. A 10‐d period (V10–V14) denoted the maximum rates of accumulation on a per day basis for dry weight (439 kg), N (8.9 kg), P2O5 (2.4 kg), K2O (5.8 kg), Mg (2.2 kg), S (0.7 kg), Zn (14.2 g), Mn (18.0 g), B (3.3 g), Fe (95.3 g), and Cu (3.0 g). The majority of total uptake occurred post‐flowering for P, S, Zn, and Cu. Harvest index values of P (79%), S (57%), Zn (62%), and N (58%) were identified in the grain. These results provide much needed data on the nutrient uptake and partitioning of current hybrids, and provide an opportunity to further refine fertilizer method and timing recommendations for maize biomass and grain production.

It is widely accepted that yields decline when corn (Zea mays L.) is grown continuously vs. in rotation with soybean [Glycine max (L.) Merr.], although causes for the yield reduction are unclear. The primary objective of this study was to elucidate the source(s) of the continuous corn yield penalty (CCYP). The experiment was conducted from 2005 to 2010 in east‐central Illinois beginning with third‐year continuous corn (CC) or a soybean–corn (SC) rotation at six N fertilizer rates. Averaged across all years, yield at the agronomic optimum N rate for CC was 8.84 Mg ha−1 and for SC was 10.20 Mg ha−1, resulting in a CCYP of 1.36 Mg ha−1; values ranged yearly from 0.47 to 2.23 Mg ha−1. Using a regression model, three significant and independent predictors explained >99% of the variability in the CCYP: unfertilized CC yield (0NCCYD), years in CC (CCYRS), and the difference between CC and SC delta yields (maximum yield – unfertilized yield) (DELTADIFF). The strongest predictor, 0NCCYD, reflects net soil N mineralization and demonstrates that it decreases in CC systems. The CCYRS was strongly and positively correlated with CCYP, indicating that the CCYP increased through Year 7. We believe that CCYRS measures the effects of accumulated corn residue in CC systems. Finally, we consider DELTADIFF to be a measure of the interaction between yearly weather patterns and crop rotation, which results in more negative yield responses for CC than SC under hot or dry conditions. This study concluded that the primary causative agents of the CCYP are N availability, corn residue accumulation, and weather.

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because of its winter-hardiness and its exceptional ability to scavenge residual N (Wagger and Mengel, 1988; The inclusion of cereal rye (Secale cereale L.) as winter cover crop Ditsch and Alley, 1991;Shipley et al., 1992; Bollero and (WCC) following corn (Zea mays L.) has been suggested as a valuable nutrient management tool in the typical corn-soybean [Glycine max Bullock, 1994). In a review paper, Meisinger et al. (1991) (L.) Merr.] rotation of the U.S. Midwest. However, little information reported reductions in the mass of leached N ranging is available on the effects of rye WCC on the soybean crop. The obfrom 59 to 77% with rye WCC compared with no cover jectives of this study were to quantify biomass and nitrogen (N) uptake crop. The N content of rye WCC is reported to be around of rye WCC and to evaluate the effect of rye WCC on soybean yield. 40 kg N ha Ϫ1 (Wagger and Mengel, 1988), although it The effects of four rotations (corn/soybean, hairy vetch-corn/ryecan reach up to 120 kg N ha Ϫ1 (Vaughan and Evanylo, soybean, rye-corn/rye-soybean, and hairy vetch ϩ rye biculture-corn/ 1999) in field crops rotations. Kessavalou and Walters rye-soybean) on soil residual NO 3 -N content, rye biomass, N content, (1999) concluded that rye N content was close to the reand C/N ratio, soil residue cover, soybean light interception, and grain duction in residual soil NO 3 -N, and therefore rye N conyield were investigated at Urbana and Brownstown, IL. Rye N content tent can be considered a good estimator of the reduction was highly correlated with soil residual NO 3 -N content (r ϭ 0.64, p Ͻ in potentially leachable NO 3 -N. 0.0001). Rotations that only included hairy vetch (Vicia villosa L.) reached maximum N content at lower corn N rates compared with ro-In the long term, the addition of large N and C inputs tations with rye. Soybean light interception at R1, R4, and R6 growth in the form of WCC biomass to the soil results in higher stages and grain yield were not affected by the treatments. Rye WCC