2010 may be critical year to replenish potassium

As 2010 gets underway and growers plan for the upcoming crop season, applying potassium (K) fertilizer may be more important than ever. According to a study released last fall by the International Plant Nutrition Institute (IPNI), 39 percent of the soils across North America were in negative balance for K, and this study didn't take into consideration the cutbacks of the 2009 growing season.

The decreasing soil levels for K, combined with agronomic factors held over from the 2009 growing season, may place 2010 yields in greater jeopardy for nutrient deficiency than what is normally expected.

"Cool, wet years like 2009 set up agronomic challenges for crops which exacerbate the impact of limited soil nutrients," says Steve Phillips, Southeast region director with IPNI, a not-for-profit, science-based organization with a focus on agronomic education and research support. "Season-long excess soil moisture and resulting compaction from planting, spraying and harvest cause poor soil aeration.

"Oxygen is required for root nutrient uptake; damp, compacted soils are lower in soil oxygen, thus limiting the plants' ability to uptake K. If we see continued wet conditions in 2010, the situation only becomes more complex," Phillips explains.

Potassium is very important for plant function as it activates more than 60 different enzymes and plays an important role in photosynthesis and plant metabolism. It is particularly essential in protein crops such as soybeans for converting nitrogen to protein and also plays a role in reducing plant disease. Insufficient K may lead to reduced nitrogen uptake, less developed roots, lower protein content, greater susceptibility to water loss and wilting, as well as weaker stalks that are more prone to lodging.

Another season of prolonged cool temperatures plus wet, compacted soils could cause irreparable damage to yield potential since more than 50 percent of the total potassium is taken up by corn plants in the first 50 days. Compaction and wet soils also may limit K uptake shortly before pollination when corn plants remove more than 15 pounds of K20 per acre per day.

“Over time, continued removal of K without annual fertilizer application will lower soil test levels and yield loss will occur because K removal is directly related to crop yield,” says Phillips.

"Yield losses are inevitable when nutrient levels drop below certain levels," explains Dan Froehlich, director of agronomy for The Mosaic Company. "A 180-bushel corn crop requires 240 pounds of K20. The critical level of potassium in the soil for optimum performance is approximately 165 ppm, and yield losses can be severe when the soil K levels drop below 165 ppm."

"Studies show that when soil K levels are at 100 ppm and the field does not receive potassium fertilizer, yields will only be about 85 percent, compared to soils that are not below the critical level," Froehlich adds. "We can only wonder where 2009 yields may have been if essential nutrients had been at recommended, balanced levels on 100 percent of corn acreage." Consider 15 percent additional yield on the 39 percent of the acres that have a negative balance for K.

"We encourage growers to visit with their local fertilizer retailer soon to get a handle on the nutrient balance situation in their area and to begin planning for spring application, choosing the products, rates, application method and timing to best meet the nutrient needs of the 2010 crop," Froehlich concludes. "With a clear picture of the situation on their own farm, they can develop a fertility plan for 2010 that will meet the crop nutrient needs and optimize their production and profitability."

For more information about proper crop nutrition, soil testing and the importance of balanced soil fertility, visit http://www.Back-to-Basics.net.