Gone are the days of planting soybeans and leaving them to do their thing. Management is critical when every bushel counts, and in-season decisions can add or subtract about 8 bu. per acre.
“Keep fields clean of weeds, insects at bay and plants healthy with fungicide and make sure fertility matches yield potential,” says Ross Bender, agronomist at The Mosaic Company.
Fertilizing soybeans might seem unnecessary because they fix their own nitrogen (N), but other macro- and micronutrients impact yield too.
“There are 17 essential nutrients. Macronutrients you need in large quantities include N, P [phosphorus] and K [potassium],” Bender says. However, don’t discount the importance of micronutrients, he adds. They’re needed at different points in the season, and some work in conjunction with macronutrients.
“Sulfur is an essential building block in chlorophyll development and protein synthesis,” says Wesley Haun, agronomist with Tiger-Sul. “Sulfur is required by the rhizobia bacteria in legumes for nitrogen fixation.”
“Soybeans require 20 lb. to 25 lb. of sulfur per year,” according to Pioneer research. “Ammonium sulfate, ammonium thiosulfate, gypsum, potassium sulfate, magnesium sulfate and elemental sulfur are potential sources of supplemental sulfur.”
Boron is needed because it helps with cell production, balances sugars and starches in plant cells, influences N metabolism and protein formation and helps manage water.
Boron levels should range from 25 ppm to 60 ppm. Both liquid and granular forms can be effective when used in the right way at the right time.
“To avoid leaf burn, foliar boron application rates should be less than 0.5 lb. per acre, and don’t spray when temperatures are high and the crop is under stress,” says Mike Staton, Michigan State University (MSU)Extension agronomist.
Zinc drives numerous metabolic responses, and deficient plants struggle to process carbohydrate and proteins and with chlorophyll formation.
Zinc is created when organic matter is mineralized, so conditions that slow this process increase risk of a deficiency. Cold weather or conditions that cause root growth to slow might prevent plants from having access to zinc. An excessive P application (more than 200 lb. of P2O5 per acre) can cause zinc deficiencies, according to MSU.
Sources of zinc include zinc sulfate, zinc-ammonia complex, zinc oxide and certain kinds of manure. MSU suggests 0.5 lb. to 1.0 lb. of zinc per acre with a rate of 20 gal. of water on a trial basis and then evaluating the response via tissue tests.
For more details on every essential macronutrient and micronutrient, visit bit.ly/2sSSoF0