X20000! Two years of yield checks here. 15" rows with 2 varieties. 160,000-60,000 in 15 inch rows. 20,000  increments. Never had an increase over 100,000,60-80 is usually the top. This planting was done at normal corn planting time. Notil into corn stalks.  Pretty simple test to run . We just split the planter. and then reduced the pop each strip,

First year we did a strip with  30" planter and it seemed to need a higher population! Makes no since! It wasn't available the next year.