Regardless of your operation’s soil health system, nutrient management is impacted by it in one way or another. There’s no debate that improving crop yield, soil health and water quality is synonymous with good nutrient stewardship and heightened conservation practices.
Achieving sustainable crop productivity depends on minimizing disturbance and maximizing nutrient use efficiency. For years, we believed nitrogen, phosphorus, potassium and soil organic matter content are good predictors of plant growth and high functioning soil, but that is no longer true.
“Contrary to belief, the fungal-bacteria ratio is the best indicator of soil health,” says Doug Peterson, Regional Soil Health Specialist at the Natural Resource Conservation Service. “A high fungal, low bacterial count is ideal when examining soil. High fungal counts generate good plant growth while high bacterial counts lead to poor growth.”
Along similar lines, tilling is extremely disruptive to soil and dramatically reduces fungi, including mycorrhizal fungi that are essential in transferring nutrients between plants. So, it’s no surprise that no-till fields show high fungal counts and, therefore, have better growth when compared to tilled fields.
Another common myth we often hear in the industry is that fertilizers feed plants directly. Much of the fertilizer applied isn’t taken up by plants the year it’s applied. Microorganisms in the soil feed on the excess nutrients and eventually transfer those nutrients to crops years later.
“Producers often try to make up for those losses with extra application of fertilizer, which only sets back soil health further,” says Peterson. “Nitrogen and phosphorus fertilization cause a reduction in mycorrhizal fungi populations at rates of 15 and 32 percent, respectively.”
In a conventional tillage program, only 30 to 50 percent of the nitrogen applied reaches the plant, leaving behind ineffective soil biological communities that struggle to retrieve resources for plants, according to Doug Peterson, Iowa/Missouri regional soil health specialist, National Resources Conservation Service. The remaining 50 percent of nitrogen applied is most often lost through leaching or erosion.
There is a silver lining, though. When land is converted to a cover crop, no-till system, nitrogen uptake has the potential to increase to 80 to 90 percent, with phosphorus efficiency reaching the same levels. Not only are cover crops an outstanding conservation practice, they’re also a production practice smart for your farm and your pocketbook.
Implementing cover crops reduces input costs. Without cover crops, it’s not uncommon for 50 to 100 pounds per acre to leach out of the soil even if nitrogen isn’t applied in the fall, according to Peterson. This is simply because no living crop is available to grab the nitrogen.
“At 45 cents per pound, the cost of leaching nitrogen is $22.50 to $45 per acre, a cost cover crops can help retain by taking up residual nitrogen,” says Peterson. “Although it can’t be directly recovered, that cost can be lowered by reducing fertilizer use over time.”
Beyond the cost savings benefit, cover crops increase fungal populations that are vital for resilient soil health and nutrient availability for plants. Fungal systems are far more efficient at bringing nutrients to plants and extending root systems to feed beyond the living plant root. And, fungi are often a reflection of the plant community. Meaning, if the fungi are healthy, plants will be too.
While it takes considerable time selecting soybean varieties, selecting the right cover crops for your operation likely requires more time. Take into consideration carbon-to-nitrogen ratios, mineralization and immobilization before selecting a cover crop. To help in the selection process, the Agricultural Resource Service created a chart detailing the characteristics and benefits of various cover crops.
From cover crops to no-till, effective nutrient management depends on good soil health practices. Simply put, nutrient management must be linked with soil health practices to be effective.
To learn more about selecting cover crops:
To learn about cover crop termination:
To learn about working with your Non-Operation landowner on implementing cover crops and other sustainable practices: