Producers may consider adopting narrow‐row corn (Zea mays L.) due to potential yield advantages; however, variable yield benefits, risk, and costs may limit adoption. Twin‐row corn planted in two 7.5‐inch spaced rows on 30‐inch centers allows farmers to utilize existing harvest equipment. Research was conducted on claypan soils to evaluate the effect of twin‐row corn compared to narrow‐ (≤ 22.5‐inch) and 30‐inch single‐row corn in separate small‐plot conventional, no‐till, and large‐plot no‐till trials in Northeast Missouri. This research determined the effect of (i) row spacing on intercepted photosynthetically active radiation (IPAR) and grain yield, and (ii) twin‐row plant arrangement and population compared with single rows on grain yield. There was no grain yield increase with narrow‐row compared with twin‐ or single‐row corn. Recommendations for plant populations in narrow‐, twin‐, and singe‐row spacings were similar since there was no interaction between row spacing and plant population for the hybrids in this research. Twin‐ and 30‐inch single‐row corn grain yield and IPAR was similar regardless of twin‐row corn plant placement in all trials except in large‐plot, no‐till research with a natural European corn borer (Ostrinia nubilalis Hübner) infestation.

A study evaluated corn (Zea maysL.) hybrids (Asgrow785, DKC61-73, DKC63-42, LG2642, and Kruger2114) and water management systems (nondrained, nonirrigated (NDNI); drained, nonirrigated (DNI) with subsurface drain tiles 6.1 and 12.2 m apart; drained plus subirrigated (DSI) with tiles 6.1 and 12.2 m apart; nondrained, overhead irrigated (NDOHI)) on yields, plant population, and grain quality from 2008 to 2010. Precipitation during this study was 36 to 283 mm above the past decade. Planting date was delayed 18 d in the nondrained control in 2009, and additional delayed planting controls were included this year. Grain yields were similar in the 6.1- and 12.2 m-spaced DNI and DSI systems in 2008 and 2010, but plant population increased 74% and yields were 3.1 Mg ha−1greater with DSI at a 6.1 m spacing compared to 12.2 m in 2009. At a 6.1 m spacing, DNI or DSI increased yield 1.1 to 6.6 Mg ha−1(10 to over 50%) compared to NDNI or NDOHI soil. High yielding hybrids achieved similar yields with DNI, while NDNI DKC63-42 had 1.2 Mg ha−1greater yields compared to DKC61-73. A 6.1 m spacing for DNI claypan soils is recommended for high yielding corn production.

Field research was conducted at Columbia and Novelty, MO, to determine the impact of winter-annual weed management systems on corn and soybean grain yields, winter-annual weed control, and soybean cyst nematode (SCN) egg population densities over the crop production cycle. Corn grain yield was not affected by winter-annual weed management systems. Soybean grain yield was not affected by winter weed management systems in 2001, but at Columbia in 2002 winter rye and Italian ryegrass reduced soybean grain yield 62 and 64%, respectively. Fall-applied simazine + tribenuron in corn and chlorimuron + sulfentrazone in soybean controlled winter-annual weeds greater than 99%. Fall-overseeded winter rye and Italian ryegrass in corn and overseeded Italian ryegrass in soybean controlled winter weeds 66 to 86%. In the soybean studies, race 4 SCN population densities increased (P = 0.08) in the nontreated control and remained stable (P = 0.55) with fall-applied chlorimuron + sulfentrazone from fall 2001 to spring 2002 while SCN population densities were reduced (P = 0.06) with spring-applied chlorimuron + sulfentrazone from fall 2002 to spring 2003. In the corn studies, none of the winter-annual weed management strategies reduced (P > 0.22) race 2 SCN population densities except winter rye from fall 2001 to spring 2002 (P = 0.05). This research indicates that control of weed species considered to be weak alternative hosts for SCN affected SCN population densities some instances when race 4 SCN population densities were high in a continuous soybean production system or race 2 SCN population densities were low in a 2-yr corn production system.

Increased ethanol production may result in excessive dried distillers grains (DDGs) that could be utilized as a fertilizer source for corn (Zea mays L.). Research was conducted to evaluate the effects of 1) DDG rates on weed suppression, changes in soil properties, and differences in grain yield and quality and 2) DDGs, polymer-coated urea (PCU), and anhydrous ammonia (AA) fertilizer sources on grain yield and quality. DDGs had a total N-P-K composition of 38.2-6.9-11.5 g kg -1 , respectively. There was no corn injury, common cocklebur or jimsonweed control with DDG rates up to 3600 kg ha -1 . Corn grain yield increased 1.41 and 1.56 kg ha -1 for every kg ha -1 of DDGs applied in medium and high yield environments, respectively. Grain yield was ranked non-treated control < DDGs < AA = PCU when fertilizers were applied at N equivalent rate of 140 kg ha -1 in medium and high yield environments.

Soybean seeded [Glycine max (L.) Merr.] early into standing wheat (Triticum aestivum L.) using relay intercropping (RI) and seed‐coat technology may reduce mechanical damage and soybean interference to wheat. Field research at Novelty from 2003 to 2005 and Albany in 2004 evaluated effects of seed coat technology on wheat and soybean response, and gross profits of RI soybean using seed coat technology compared with selected full season (FS) wheat or soybean and double crop (DC) wheat‐soybean. Wheat grain yield in the absence of soybean was 10 bu/acre greater in narrow (7.5‐inch) than wide (15‐inch) rows. Relay intercropped Intellicoat (ITC) treated 5143 soybean delayed germination and increased 15‐inch wheat grain yields 8 bu/acre compared to non‐coated (NC) 5143. At Novelty, RI 5143 ITC yield was similar in all three years and 7 bu/acre greater at Albany than 5143 NC. In 2005, dry conditions in mid‐ to late June reduced RI stands and yields compared to DC soybean at Novelty. Double‐cropped 5143 NC soybean had greater gross profits than RI 5143 ITC when wheat and soybean prices were high. However, RI 5143 ITC gross profits were greater when soybean prices were high and wheat prices were low. The RI system using ITC maintained soybean yields and did not reduce wheat yields due to mechanical damage or soybean interference compared to non‐coated or fungicide‐only coating.