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| At least Iowa tests don't show a big variation on beans harvested varying from 85K to 185K planted. Maybe a bushel or two at the most. Dr. Palle Pedersen (was Iowa State, now Syngenta and I've not heard him say anything since that move) has been saying go low on the population, you'll save more in seed cost than you'll loose production. Dr. Tracy Blackmer (Iowa Soybean Association) says the higher populations produce more, but his raw data shows only a bushel or two more.
Secondary factors like your lodging and crusting after planting are probable more important. Maybe you need to cut the rate in the black ground to reduce the push for tall plants and so help the lodging. The Iowa experimenters seem to show that cutting the population all over isn't a bad idea just for saving seed. My observation contrary to reduced seeding rate happens in soil that crusts before the beans push through. You need a certain number of seeds per foot to lift that crust without crunching the seedlings to get emergence, or you need a rotary hoe over the field at the right time (which is often prevented by the same spring rains that created the crust around here) to crack the crust. Going low population and narrow rows spreads the seed out in the row to make crusty emergence a serious problem, I think. So I think it takes a balance between crusty emergence and saving seed and that unless you get planted rates well below 85K you aren't going to see a big change at harvest and going way high you aren't going to see a big (or even for sure detectable) increase at harvest. Maybe a spoked closing wheel can help the crusting.
Gerald J. | |
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Variable rate planting beans
