January 29, 2009
US soy planting population and profits; less is more
In the quest to reduce input costs, US soy growers may be asking themselves if greater profits could be achieved with reduced seeding rates.
The effect of soy seeding rate on yield was evaluated in University of Minnesota research trials conducted across southern Minnesota in 2007 and 2008.
These trials, supported by the Minnesota Soybean Research and Promotion Council, demonstrated that very low seeding rates under good conditions could result in maximised yields.
Starting with a low plant population, however, can be risky as stand loss can be expected throughout the growing season.
A guideline commonly used for estimated stand loss throughout the season is 20 percent. Losses, however, can vary considerably.
Differences between planting and final populations ranged from a loss of 8 percent to 47 percent depending on target population and location in University trials in 2008. Losses were greatest where seedbed conditions were very wet at planting.
Previous soy population research and studies looking at the effect of hail injury on soy show that soy stands of 100,000 plants per acre or more at harvest are sufficient to obtain optimal yields. Harvest in north-western Minnesota stands of 125,000 to 150,000 plants per acre are needed to maximize yield.