Job number one is to leave 2012 behind, other than managing the crop in the bin and tending to marketing and crop insurance paperwork, and focus on 2013. Most specialists suggest starting with a clean slate, factoring in what condition the soil is in coming out of 2012 and into 2013.
For soybeans, Shaun Casteel, Purdue University Extension soybean specialist, says that a significant amount of potash deficiency symptoms were reported on corn and soybeans in drought-damaged fields in 2012.
Corn leaves turned brown around the edges and soybeans did too, indicating a lack of potassium in the plant. Some of those shortages were artificial, caused by the inability of the roots to take up potassium from the soil because it was so dry. The plants were seeing a real deficiency and needed more potassium. But it wasn't because the potassium wasn't in the soil. It was just because the plants couldn't get to it through their roots to use it in this particular year.
However, writing all symptoms of potassium deficiency off to the drought could be a mistake, he says. There are fields in Indiana where potash needs to be applied, and where soil potassium levels are low to moderate. Soybeans are a big user of potassium, and will respond to potash fertilizer if the soil test level is low and it is applied.
There are a few quirks to keep in mind with soybean potassium shortages and soil potassium levels. If soil samples are taken when the soil is very dry, soil potassium levels will tend to show up lower on the test results than they really are in the soil. Some areas have now received enough rain in August and September that soil sampling may be possible again, and potassium levels could be fairly representative of what's really there.
The other caveat for this year is that if the corn was so poor it was removed as silage, more potassium left the field, even if it only made one or two dry tons per acre of silage, than if a poor crop of grain was harvested and the residue was left in the field.
Casteel will explain how to better quantify those situations in his next edition of Soybean Success in the October issue of Indiana Prairie Farmer. Look for it in your mailbox within the next few days.