PMN Crop News Homepage   

Posted 31 March 2016. PMN Crop News.

Phosphorus: Keeping it for the Crop

Source: Illinois Soybean Association Press Release.

Bloomington, Illinois (March 1, 2016)--Phosphorus (P) is one of the two nutrients to contribute to hypoxia. Nitrogen is the other. New insights into how phosphorus leaches into groundwater can reduce its potential impact on water quality and its impact on the environment. Phosphorus poses an environmental threat when it travels from soils to open bodies of water, including lakes, streams and rivers. Click here to read an Ag professional article on the problem.


I think the key takeaway from the article was that too high of a soil test or too much phosphorus in the soil leads to leaching across many different soil types. I personally have an area in one field on my farm where I will not add P in my lifetime due to an over application of hog manure many years ago. Added to that was I was not watching soil test levels closely enough before making routine P applications based on a removal rate. I discovered the area by noticing an algae bloom downstream from one of my tile outlets. I went ahead and did a soil test of that field and examined the results closely. This is an easy mistake if you donít routinely soil test and donít know what your P levels are.

To complicate the problems with P leaching down through the profile are the massive amounts of pattern tile going in at this time. Historically, fields were not tiled or the tile was placed at wide intervals. Yields were also lower. In 1972 when I returned to the farm my father had used a per acre analysis of 0-80-80 for a 2-year rotation of corn and soybeans. Within two years our yields had jumped up to over 150 and 50 for corn and soybeans, respectively, and subsequent P and K applications began to rise. For the last three years with great corn and soybean yields the application rate per acre is 45-115-180 using DAP and potash. Do I really need this much fertilizer? With tight margins, I will be incorporating a VRT program this year. It has been too easy to farm the past three years without really thinking agronomically or managing inputs for profitability.

A long-term no-till field enables roots and worms to create natural channels for preferential flow of water and water-containing nutrients to the tile in any situation. The value of no-till to reduce erosion and surface phosphorus loss is quickly offset by soil tests above recommended P amounts in areas where the preferential flow and tile loss can be a problem.

Maybe the lower commodity prices will institute better practices for everyone, because farming is not going to be easy until the next drought or higher prices return. Throw in Illinoisí NLRS and things are going to be tougher on everyone.

Dick Lyons is a cash grain farmer of 43 years in the panhandle of Montgomery County, Ill. Lyons has a BS in Agriculture Education from Illinois State University with an MA in Education from the University of Illinois-CU. He has taught for more than 30 years at Lincoln Land Community College, Illinois State University, and for various agriculture companies. He is working for the Council for Best Management Practices (IL C-BMP) as a cover crop specialist, is an associate director of the Montgomery Co. SWCD, and serves on the board of directors for the Illinois Association of Drainage Districts as wells as two local drainage districts.