Many corn (Zea mays L.) growers in Ohio delay harvest as a management strategy for reducing grain drying costs. However, this practice increases the risk of yield loss due to extended crop weathering. Field studies were conducted at three Ohio locations in 2002 to 2004 to determine eff ects of three harvest date periods, early to mid-October (HD1), early to mid-November (HD2), and early to mid-December (HD3), and four plant densities (59,000; 74,000; 89,000; and 104,000 plants ha -1 ) on the agronomic performance of four corn hybrids diff ering in maturity and stalk strength. Interactions between harvest date, plant population, and hybrid indicated that decreases in grain yield and increases in stalk rot and lodging associated with harvest delays were infl uenced by plant population and hybrid characteristics. Signifi cant yield losses due to delayed harvest were evident only aft er HD2. When harvest was delayed until HD3, yields decreased at the higher plant populations, especially at 104,000 plants ha -1 . Stalk rot and lodging increased at the higher plant populations, and this eff ect was magnifi ed by late harvesting. Hybrids with lower stalk strength scores exhibited greater stalk lodging and yield loss when harvest was delayed beyond HD2. Stalk rot showed a greater increase between HD1 and HD2, whereas stalk lodging generally showed a greater increase aft er HD2. Harvest delays aft er HD2 achieved little or no additional grain drying. Results of this study indicate that harvest delays should be avoided when using plant populations above 74,000 plants ha -1 , especially if planting hybrids that are not highly rated for stalk strength.

Accurate estimation of nitrogen (N) balance (a measure of potential N losses) in producer fields requires information on grain N concentration (GNC) to estimate grain-N removal, which is rarely measured by producers. The objectives of this study were to (i) examine the degree to which variation in GNC can affect estimation of grain-N removal, (ii) identify major factors influencing GNC, and (iii) develop a predictive model to estimate GNC, analyzing the uncertainty in predicted grain-N removal at field and regional levels. We compiled GNC data from published literature and unpublished databases using explicit criteria to only include experiments that portray the environments and dominant management practices where maize is grown in the US North Central region, which accounts for one-third of global maize production. We assessed GNC variation using regression tree analysis and evaluated the ability of the resulting model to estimate grain-N removal relative to the current approach using a fixed GNC. Across all site-year-treatment cases, GNC averaged 1.15%, ranging from 0.76 to 1.66%. At any given grain yield, GNC varied substantially and resulted in large variation in estimated grain-N removal and N balance. However, compared with GNC, yield differences explained much more variability in grain-N removal. Our regression tree model accounted for 35% of the variation in GNC, and returned physiologically meaningful associations with mean air temperature and water balance in July (i.e., silking) and August (i.e., grain filling), and with N fertilizer rate. The predictive model has a slight advantage over the typical approach based on a fixed GNC for estimating grain-N removal for individual site-years (root mean square error: 17 versus 21 kg N ha−1, respectively). Estimates of grain-N removal with both approaches were more reliable when aggregated at climate-soil domain level relative to estimates for individual site-years.

production system licensed by DuPont Specialty Grains (Des Moines, IA) is rapidly gaining popularity as the The TopCross grain production system is rapidly gaining popularity preferred method of producing HOC (U.S. Grains Counas the preferred method of producing high-oil corn (Zea mays L.). A blend (TC Blend) of two types of corn is planted to produce cil, 1999). Commercial high oil (HO) single-cross hy-TopCross high-oil corn (HOC) grain. Limited information is available brids have not been widely used by growers because on the effects of the TopCross system on agronomic traits that may their grain yield potential is lower than normal dent determine the profitability of HOC production. Field experiments hybrids (Watson and Freeman, 1975;Lambert, 1994). and on-farm studies were performed in 1995 to 1999 across a range The TopCross system may minimize the yield disadvanof production environments in Ohio to compare the agronomic perfortage associated with conventional HOC hybrids while mance of TC Blends with their conventional counterparts (check enhancing grain nutrient composition (Edge, 1997; Lamhybrids). Grain yields of TC Blends averaged across experiments and bert et al., 1998). With the TopCross system, HOC has on-farm studies were 8% less than those of check hybrids. The TC been reported to yield as well as normal corn (Crom-Blends were as tolerant to drought conditions as the check hybrids.well, 2000). Stalk lodging and barrenness were comparable for TC Blends and check hybrids. Little evidence existed that kernel set in TC Blends wasThe TopCross HO grain production system involves reduced by inadequate pollen availability due to the limited number of planting a blend (TC Blend) of two types of corn (Edge, pollinator plants in the blend. Factors that may contribute to the 1997). One type, representing 90 to 92% of the seed in differences in grain yields between TC Blends and check hybrids the blend, is a hybrid that is designated as the grain included lower plant populations in TC Blends at harvest, competition parent. The second type, representing 8 to 10% of the between the two components of the blend (TC Blend pollinators and seed in the blend, is designated as the special pollinator. male sterile grain parents), and the physiological cost of oil synthesis.The TC Blend grain parent is a male sterile (produces The lower grain yield, higher grain moisture content, and lower test no viable pollen) version of an elite hybrid. The TC weight associated with TC Blends should be considered when de-

Grain of corn (Zea mays L.) hybrids containing nutritionally enhanced genetics may exhibit higher oil and crude protein profiles than normal field corn. However, the impact of N management on these traits is not well understood. Field experiments were conducted at Hoytville, OH from 2000 to 2002 to determine effects of different timings of nitrogen application (at planting versus split) and N rates (0, 60, 120, and 180 lb/acre) on the grain yield, protein, and oil of two corn hybrids containing Supercede genetics. Grain protein concentration showed more consistent response to increasing N rates than did yield. Protein exhibited a linear response to increasing N rates each year. Yield responded positively to increasing N rates in 2001 and 2002 but showed no additional response above 60 lb of N per acre in 2000. Split applications of N increased grain protein concentration in two of the three years, but had little or no effect on yield. Grain oil concentration was not influenced by the timing of N application and responded to N rate only in 2001. Results of the study demonstrate that N management will be an important factor in maximizing the grain protein of nutritionally enhanced hybrids, but producing grain with consistently high protein concentration may be difficult given the variation in growing conditions and environments characteristic of this part of the Corn Belt.

Heavy precipitation events may also be accompanied by strong winds that could induce stalk breakage (also known as greensnap or brittle snap) or root lodging in crops like corn (Zea mays L.). In some cases, these storms have manifested as derechos or long-lived storms with straight-line winds producing damage similar to a tornado but with the damage occurring in one direction (Corfidi et al., 2016). Damage from these events was evident in parts of Ohio in both 2011 and 2012 (Corfidi et al., 2016); more recently, an event occurred in Iowa in 2020 (National Weather Service, 2020).There is interest in how corn management practices may influence the impact of greensnap and root lodging on yield. Much of the past work in this area has been conducted at populations lower than those used currently (Carter & Hudelson, 1988;Licht & Clemens, 2021;Xue et al., 2017 ) or in planting orientations that differ from U.S. practices (Wu et al., 2020). Improving the availability of data related to root lodging and greensnap response to seeding rate would better prepare crop practitioners to understand the implications for damage and yield in the event that severe wind damage is experienced in the future.