Silage Corn Hybrid Response to Row Spacing and Plant Density in the Intermountain West.

Growers frequently ask about optimal plant population and row spacing of silage corn (Zea mays L.) in semi-arid, irrigated cropping systems.The objective of this study was to determine the dry matter yield and quality effects of corn hybrids grown in different plant populations and row widths in the Intermountain West. Research was conducted at two locations under sprinkler irrigation, North Logan, Utah and Jerome, Idaho. The soil at North Logan was a Millville silt loam, while the soil at Jerome was a Rad silt loam soil. Hybrid was the whole plot treatment, with three Dekalb hybrids selected to represent a range of relative maturities (99-, 106-, and 111-d RM). Each hybrid was grown at two row spacings (76 and 51 cm), which was the sub-plot treatment. Plant population was the sub-sub-plot treatment with six total plant populations ranging from 61,776 to 123,552 plants ha^-1 at intervals of 12,355 plants ha^-1. Treatments were arranged in an RCBD with four replications. Data collected included stalk diameter, LAI, and IPAR at silking stage. At harvest, yield and quality were measured. In 2015, forage yield increased approximately 4-7% when row spacing was narrowed from 76-cm to 51-cm. Stalk diameter increased by 1.2mm on 51-cm row spacing compared to 76-cm row spacing. Yield increased linearly from 61,776 to 123,552 plants ha^-1 for all hybrids. Narrow row spacing appears to increase yield while maintaining silage quality, resources are being utilized more efficiently by planting corn on narrow rows between 86,487 and 98,842 plants ha^-1.