Latimer, Iowa (north central) | We have done trials, non scientific, of 7.5's with a 1890 air seeder, 15's with a planter (doubling back), and 30's with the planter. I did 5 or so trials each year comparing the 3 different types over a 3 year span. We had more emergence issues the lower we went with population and the narrower the row spacing. They didn't seem to have the power to get out of the ground with the narrower spacing and further between the plants. If conditions were challenging at all at emergence the 30's were the best. If conditions were good, lower populations (100,000) were the best but again with any challenges, we found ourselves even replanting some of the low populations. Overall we have settled on just doing 30's at 130,000 population as the best blend. If the opportunity presents itself (have an extra driver and extra tractor) we will do some soybeans with the air seeder while I am planting corn and jump the population to 140,000. They generally yield the same as the ones done with the planter a week later at 130,000.
For me, its hard to get out of a 90'planter into a 40-50' seeder as far as getting stuff done. I see better depth control no-tilling with a planter with delta force than a seeder with just continuous hyd/spring downforce. Haven't tried 20's as we don't have the equipment for it. My thoughts would be that there isn't enough yield difference in any of the spacings to justify the additional equipment expense if what you have already gets over the acres needed. I haven't seen the consistent benefits to planting as early as possible on soybeans. They do yield better if the conditions are great but with our climate I have had early beans freeze off twice and lay in the ground for several weeks more often than not. Mid April beans are more risky then early May beans for us.
I do prefer the 7.5 inch spacing for double crop soybeans. I think the conditions in mid July are more forgiving on emergence. With double crops, the beans seem to only get about so tall and they bush out better when done with the air seeder. My trials have been about almost double when done with the seeder vs planter. This year beans done with seeder were 28 bpa and ones done with the planter were 16 bpa. I do roll everything to knock down the stubble and give more light to the beans.
With the air seeder I can also have radishes and turnips in the front tank and seed 4 lbs an acre while I plant the double crop soybeans from the back tank. Gets my cover crops planted at the same time. We don't harvest the soybeans till after it freezes a few times so haven't had an issue with material flow into the header. Gets our crop diversity up and meets my own goals. Guessing you are not talking double crops but thought it was worth mentioning.
Our climate and soil is virtually the same as southern MN in the cold middle finger of Iowa where we farm. |
15" or 20" vs 30" Soybeans in Southern MN
