By Leon Ressler, Penn State Extension Agronomy Educator
Thirty years ago, concerns about runoff from fields contributing to water quality problems came into a sharper focus. At that time the general understanding was that most of phosphorus losses to surface water was a result of sediment loss since phosphorus is tightly bound to soil particles. The strategy developed was one of control soil loss and you will control phosphorus loss to our waterways.
No-till practices have increased significantly over the past thirty years and many benefits have been realized in our agricultural production. The improvements in no-till equipment has reduced early failures and has greatly enabled wide adoption of the practice. Time and fuel savings are a great advantage.
Additionally, we have learned much about the soil health benefits that come with no-till practices. Improved soil structure has increased water infiltration reducing runoff and increasing our ground water supplies. Of course, one of the main objectives of no-till was to reduce soil erosion and that has certainly been realized and has contributed to the reduction in sediment loss and the attached phosphorus loss to surface water.
On livestock farms with significant manure production, long term surface application of manure has resulted in a concentration of phosphorus in the top inch or two of soils. In the past there was a general belief that phosphorus was not likely to dissolve in surface water and therefore was not leaving fields in clear water. In recent years however, research has shown that with a very concentrated band of phosphorus on the surface of our soils, phosphorus can dissolve into surface water and leave the fields in clear run off.
So, this creates a dilemma, conventional tillage practices did mix in the manure across the plough layer and prevent a concentrated buildup of phosphorus in the top inch or two of our soil profiles. But we don’t really want to go back to the old tillage methods since there are many disadvantages.
The compromise solution seems to be manure incorporation. Just as no-till planting equipment has improved greatly, manure incorporation equipment as made great strides. New equipment today enables injection of manure three or four inches below the surface with very minimal surface disturbance. This provides several important benefits.
First placing the manure deeper in the soil profile means you do not get a concentrated band of phosphorus near the soil surface. This also reduces nitrogen losses from ammonia volatilization which saves fertilizer dollars on farms where manure is not enough to meet all crop needs. This savings of nitrogen can be enough to pay the additional cost of injection. A big benefit to farms with neighbors is the reduction of odor. In places where odor is a contentious issue this alone would be worth the cost of injection.
Today several custom manure haulers have invested in current manure injection technology. Check with your custom operator to see if they can provide this service. If it is available in your area you may want to give it a try to evaluate the benefits on your farm.