Make Manure Manageable Again

Manure is a gift and a curse for the Wisconsin dairy farmer. On one hand they have a valuable resource for fertility on crop acres. It also becomes the dark cloud for dairy operations; being the source of time constraints, nutrient runoff, and financial strains. Finding methods and approaches that bring consistency and flexibility to applications is often hard to find. That was true until conservation agriculture.

Conservation agriculture can be cumbersome to define, but it is easy to identify. Simply, it is the implementation of landscape management that reduces soil and fertility loss on cropland. Most practices that are considered conservation agriculture involve the use of summer or perennial vegetation and/or cover crops, where the soil surface on fields are covered by active plants and stimulated by living roots. This ‘cover’ offers a mechanism to dairy farmers to apply manure with reduced/or eliminated runoff, and more flexibility for applications. In another way, conservation agriculture’s aim is to avoid the wasteful use of a resource. In our case: manure.

Commonly asked in my office from farmers is “how come all this runoff is a big deal now, and not back when my grandpa was moldboard plowing?” The country landscape is different now than it was then, but not just naturally (forests, prairies), but rotationally. In Marathon county alone, from 1999 to 2018 corn and corn silage acres increased by 8%, and soybeans by 14%. Whereas small grains (oats, wheat, barley) decreased by 10% and perennial hay fields by 12%. More acres became prone to more bare soil, especially during the most critical runoff events of snow melt and rainfall in the spring on fall plowed fields. When soil is disturbed from tillage it loses its structure and strength with the loss of aggregates (chunks of soil made up of water, oxygen, organic matter), and then turns into smaller particles that are more prone to washouts from rain and snow melt. It isn’t just the soil that is leaving the field, however, but any fertility in the soil as well (potassium, nitrogen, phosphorus).

Loss of soil structure also creates lower trafficability. Particles that are not taken away from the field begin to settle after each rainfall, and this settling creates compaction. Compaction may look “solid”, but it is far from it. Being mostly particles, the profile has no structure, and when it is wet/ moist it will become too soft to drive on, let alone even walk on. This compaction also lowers infiltration and increases ponding (water not soaking in). But it isn’t the ponding water that slows down the tractor. Aggregate development in the soil profile creates a network of structure that gives fields a lot of backbone. When you have roots in the soil it further anchors the ground, because the roots from the cover crops are forcing pore-space which increases water infiltration and better trafficability. How all this equates to manure applications is utilizing those living plants and the roots they produced in the soil profile to get a better catch and hold that manure in place. Dribble bar applications are best, for custom applicators and for the cover crop as well. Little mechanical breakdown and faster application, the manure comes out in larger droplets that roll off of leaves and soak into the ground. These applications work well for grass hay, alfalfa fields, lower density/high density vegetation. Tanker loads are the most used and accessible but the cover needs to be able to shed off the manure, so it doesn’t stay covering the leaves too long, possibly killing it. Tanker applications have more success on very thick cover crop stands that have a lot of canopy. Low disturbance injection has been a beneficial application to incorporate manure without much disturbance to the field, and has been one that offers flexibility for established covers or seeding. Newly seeded winter rye will respond well after a low disturbance application with the extra moisture from the manure. As the winter rye grows (even in the depths of winter) it will push more and more roots and upper vegetation that will sequester the nutrients, and hold the soil/manure in place.

The task is easier said than done when operations have to consider that miscues in applications can bring heavy consequences. That is why farmers are always looking for the next advantage. Having cover crops in their rotations offer many advantages, logistically and agronomically. Cover crops, especially diverse mixes create maximum soil stimulation that mitigates compaction, increases infiltration, creates a mechanism that reduces manure applications leaving the field from runoff, and increasing flexibility of applications to avoid tight windows in the fall and early spring. Conservation agriculture is more than just building the soil so it gives back. It is also a way farmers can maximize a resource and not let it go to waste.

THE SOIL

SOUNDOFF

BY

MATT OEHMICHEN AGRONOMIST