Feeding our Crops, Protecting our Water
New technologies and soil conservation practices have greatly reduced sediment and nutrient loss from farmland, but cropland is purposely nutrient-rich and natural levels of N and P in lakes and streams is very low.
Overland flow tends to be the ‘hottest’ source of nutrients so it is important to select BMPs that retain water in the field. Even low amounts of runoff from large land areas can degrade water quality and upset the balance of aquatic life. The practical on-farm challenges of keeping nutrients in the root zone year-round highlight the importance of using multiple barriers or stacked/bundled BMP’s in the cropping system.
In recent years, the Michigan chapter of the Soil and Water Conservation Society MI-SWCS has organized an annual conference to highlight practical options for feeding our crops while minimizing nutrient loss from leaching or runoff. Dr. Merrin Macrae, University of Waterloo presented on-farm research results from southern Ontario demonstrating the value of multiple BMP’s to stabilize cropland and prevent runoff. The greatest risk for crop nutrient loss with runoff occurs at snowmelt so it is best to avoid late fall nutrient applications and all applications on frozen ground. Typically, about 80% of annual runoff and nutrient loss can occur between October and June with most of that during snowmelt in March. Subsurface bonding carries less risk than surface broadcasting, so incorporate broadcast nutrients before the next rainfall because most nutrient loss occurs with the first rainfall events.
Larry Geohring, Cornell University summarized research results from several years in New York demonstrating the value of periodic tillage to disrupt preferential flow paths and in mixing the nutrients evenly throughout the root zone, thereby reducing soil test P at the surface in no-till fields. The risk of phosphorus and bacterial transport from liquid manure through drainage tiles increased when the manure was surface applied on wet soil (when the tiles were flowing). Site-specific management was important. Weather, timing and rate of N application, timing and method of manure incorporation all influenced nitrogen leaching losses from manure and commercial fertilizer. Total P and nitrate N losses on corn and orchardgrass varied with timing of application and if the soils were loamy-sand or clay-loam.
On March 2, MI-SWCS and MSUE are co-sponsoring a conference at Michigan State University-- A Matter of Balance: Managing Soil and Crop Nutrient Systems to Protect Water Quality. Conference speakers will include national experts and experienced crop and livestock producers who will explain how soils, timing, rates and methods of application, use of nitrogen stabilizing amendments and other management factors influence nutrient recovery from manure and commercial fertilizers. Attendees will learn on-farm strategies for balancing soil health and economic profitability and how some farmers are refining conservation practices based on on-farm water quality monitoring.
A Matter of Balance: Managing Soil and Crop Nutrient Systems to Protect Water Quality will be on Friday, March 2, 9 a.m. until 4:15 p.m. at the Kellogg Center on the Michigan State University campus. The conference is hosted by the Michigan Chapter of the Soil and Water Conservation Society and MSU Extension. A conference agenda, speaker information, registration information and additional details are available at the MI-SWCS website and through this link to Program agenda and conference registration info.