The Discovery Farms Program continues to churn out on-farm research results in relation to the actual performance of environmental best management practices. Since 2002, this University of Wisconsin program has set up monitoring stations at surface, tile and stream sites and, in total, has collected 160 site years of information.
Using solar-powered monitoring equipment, the program measures the quantity and quality of water in agricultural watersheds.
Last month at the Agricultural Community Engagement meeting in Madison, Wisconsin, Amber Radatz and Eric Cooley, co-directors of the UW Discovery Farms, shared four core lessons they’ve learned from their research.
1. Best management practices remain useful.
“Keeping soil and nutrients in the field is critical to maximizing yields and reducing losses,” Radatz said. “Good conservation is not out of style or gone away with technology. There is still a place for some of those practices across the landscape.”
Since landscapes and farming systems are vastly different, there is no “one size fits all” approach to take in terms of best management practices. There are plenty of options available. The trick, Radatz said, is to use different tools in the right places to come out with the best management possible.
The best management practices she has found to provide the most “bang for the buck” include:
- Grass waterways – critical with clay soils and long slopes (and not necessarily steep slopes)
- Soil protection – no-till/conservation tillage, high residue, strip crop, crop rotation, etc.
- Cover crops – soil protection and retention of nutrients
- Nutrient management – match nutrient applications to crop needs.
2. Tillage systems aren’t all bad.
According to Radatz, “Tillage systems that are well suited to the landscape have low sediment losses. Big soil losses happen when the tillage system is too aggressive for the landscape.”
When they compare systems using two tillage passes to no-till systems, the average soil loss is quite similar at less than 1,000 pounds per acre. In places where the tillage is too aggressive for the landscape, soil losses can be upwards of 4,000 to 5,000 pounds per acre.
Likewise, annual total phosphorous loss is close to the same for two-pass tillage and no-till. The trade-off is in higher dissolved phosphorus losses in no-till systems. “That can be hard to remedy because it is already in the water,” she said.
“There’s a tradeoff in this system that we really need to think about,” Radatz added, suggesting a no-tiller should think about doing a little tillage every seven to 10 years to mix up the soil and reduce dissolved phosphorus losses.
Macropores caused by earthworm burrows, root channels, shrinkage cracks and structural porosity can take away soil’s natural ability to filter. These are predominately found in long-term no-till systems and perennial crops. Tillage is one way to disrupt macropores and reinstate the soil’s filtering ability.
3. Be cautious during critical time periods.
The program has identified two critical time periods for runoff to occur, particularly in Wisconsin. The first is the end of February and early March when the snow melts over frozen ground. This period accounts for 50 percent of all runoff that occurs in a year.
Cooley outlined three driving factors for runoff to occur on frozen ground.
- Concrete frost – When a thaw occurs allowing water to penetrate the soil, followed by freezing weather that causes an ice block to form within the soil.
- Ice crusting of soil – When ice freezes over the soil surface creating an impenetrable crust.
- Deep or dense snowpack – When a large amount of snow forms a dense crust over the soil surface.
“When we think of manure applications with any of these soil conditions, there is higher potential for loss,” Cooley said. “If you do not have good soil contact we have seen a greater potential for loss of nutrients.”
Runoff occurrence is dependent upon the year and conditions and not solely because the ground is frozen. “It really is all about the contact with the soil. We’ve seen very little losses because there was good soil contact,” he said.
The second critical time period, resulting in 31 percent of total annual runoff, is in May and June when the ground isn’t frozen, but it becomes overly saturated with frequent rains.
Through Discovery Farms research, they’ve found it takes a 1 ¼-inch rainfall to cause a runoff event on low to medium moist soils; whereas in highly saturated soils it takes half that amount of rain to see the potential for runoff. On frozen ground, just a 1/2-inch of rain can result in runoff.
4. Tile drainage needs to be managed too.
“Tile drainage really adds another level of management that you have to think about when you’re applying nutrients,” Cooley said.
Through their monitoring stations, they’ve found that tiles can flow 365 days a year, especially during winter months.
Tiles can transport a lot of water from the soil surface to the tile system quickly, especially in no-till or perennial crop systems, thus being an avenue for the majority of water and total nitrogen to leave agricultural fields. In addition, tiles can be the delivery method for a significant amount of phosphorus and sediment loss.
To better manage tile systems, producers need to understand and locate tile drainage system features, maintain tile drainage systems and manage tile-drained lands.
Whether it is employing a best management practice, developing a tillage system, working within a critical time period or managing drainage tiles, Cooley said, “Informed management is really the key. Understanding the basics is really important for trying to reduce the potential loss of both soil and nutrients.”
In monitoring real farm scenarios under actual weather conditions, the Discovery Farms program plans to continue to provide data to help producers be as informed as possible when it comes to managing nutrients. PD
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