- Prices paid for sweet corn are low relative to the cost of producing the crop, and every strategy possible must be used to maximize net return. Two strategies used to enhance profitability but that have received little research attention under Western Oregon conditions are the use of pop-up fertilizers and increased plant populations. Despite indications that popup fertilizers improve early-season growth, concrete evidence that these fertilizers ultimately enhance growth and yield are often lacking. Seeding density also can be increased to improve crop yield up to a point, but intraspecific competitive ability and the competitive stress tolerance of varieties currently produced in the Willamette Valley has not been demonstrated.
Four experiments were conducted over two years with varieties Captain (both years), 1477 (2014), and Owatonna (2015). Corn was planted at densities of 20, 24, 28, 32, 36, and 40,000 plant/A. Three popup fertilizer treatments were applied under the seed row at planting and corn growth and yield in these plots compared to an untreated check.
In 2014, popup fertilizer treatments had little impact on corn growth or yield. In 2015, both Owatonna and Captain plants were taller than the untreated check plots at V6, and the effect was clearly visible. The popup fertilizer treatments had no effect on sweet corn yield or net return, however.
Sweet corn yield was greatest for Captain at 40,000 plants/A in 2014 and 32,000 plants/A in 2015. Yield of 1477 was greatest at 32,000 plant/A in 2014. Owatonna yield was greatest at 28,000 plants/A in 2015. The additional costs associated with increased plant density lowered the adjusted gross return by 5 to 6%. However, with the exception of Owatonna in 2015, the value of corn at the optimum density averaged $112 to $181/A more than the standard of 28000/A, depending on year and variety.