Potash Corp. Director of Agronomy Robert Mullen discusses management techniques for phosphorus (P) and potassium (K) in soybean production. Mullen says it’s important to have a holistic plan that factors in all macronutrients.
Understanding P and K Chemistry
o What happens in soil?
99.9% of P and K in the soil is not able to be utilized
Soil tests focus on Exchangeable K to measure adequate potassium
Soil tests focus on Absorbed P to measure adequate phosphorus
o How does soil testing work?
Lab tests flood samples with ammonium to show an estimate of Exchangeable K
Dissolved P increases with P loading of soil and has dramatic environmental consequences
o Translate soil test levels to fertilizer rates
Depending on the soil test ppm, that determines the P/K recommendation
200 ppm of K in a soil test is the ideal rate to prevent yield loss
30-40 ppm of P in a soil test is the ideal rate to prevent yield loss
o How do economic models impact rate decisions?
Figure in potash cost with soybean prices and yield potential in order to figure the return $/acre
Return on investment of fertilizer is a function of yield
Manage Loss Pathways (Timing and Placement)
o Managing particulate P is best mitigated by reduced-till or no-till
o Dissolved P requires desorption to provide solution P
o Rainfall is one of the biggest loss pathways
o Chisel plowing, no-till and ridge-till impact how P is incorporated
The Illinois Soybean Association (ISA) checkoff and membership programs represent more than 43,000 soybean farmers in Illinois. The checkoff funds market development and utilization efforts while the membership program supports the government relations interests of Illinois soybean farmers at the local, state, and national level, through the Illinois Soybean Growers (ISG). ISA upholds the interests of Illinois soybean producers through promotion, advocacy, and education with the vision of becoming a market leader in sustainable soybean production and profitability.