Diversify rotations, increase manure spreading

By: Eric Cooley, eric.cooley@wisc.edu
Originally published in PDPW's Dairy's Bottom Line

Traditional manure-spreading periods in spring and fall can present challenges when adverse weather strikes. Most of Wisconsin received excessive precipitation this spring and in fall 2018. As a result most farmers struggled to spread manure on cropland for this growing season. For those relying on custom manure haulers, weather challenges present scheduling difficulties. Everyone wants manure spread when conditions are optimal.

Incorporating winter wheat into dairy-crop rotations can provide manure-spreading opportunities in the summer. That’s when soil conditions are ideal and custom-hauler schedules are more open.

In typical corn-soybean-alfalfa rotations, manure applications are often limited in the fall because of wet conditions. Alfalfa does provide in-season spreading opportunities after cuttings. But there can be issues with crop damage, manure-borne pathogens, palatability and soil-phosphorus accumulation. Incorporating winter wheat on some acreage in the rotation will provide nutrient uptake and soil protection through the fall and winter after planting. It will also provide a marketable crop for both grain and straw. Straw is a great bedding material. Even if producers don’t have a use for it on their farms, there’s a strong market for it.

Winter wheat is harvested in late July to early August when soils are usually dry and weather conditions are favorable for manure spreading. It’s important to note that manure applications on harvested winter-wheat fields should coincide with planting a second forage crop or a cover crop.

University of Wisconsin-Discovery Farms monitored elevated nitrate losses through tile at a site that received manure on wheat ground without a cover crop. A cover crop will retain nutrients from the applied manure. It will provide soil protection while enhancing physical, chemical and biological properties of the soils, until it’s terminated. Liquid in the applied manure will help the cover crop germinate, especially when soils are dry.

Wheat may also provide the opportunity to double-crop by planting a crop that can be taken as a fall forage. Drilling a mix of peas and oats, or barley, with the manure application can provide additional fall forage. The fast-growing oats and peas can be harvested in October. Those living plants will use nutrients from the manure application.

Caution should be taken when applying liquid manure on excessively dry soils. Manure can pose a risk when cracks develop in dry soil. Some soils develop shrink cracks as they dry, such as those with a greater clay content. Those cracks have been observed to extend more than 17 feet down through the soil. That’s of particular concern on tile-drained fields or shallow soils over fractured bedrock. Those soil cracks become direct conduits for manure to tile lines or fractures. If large soil cracks are present, wait until after a light rain – or apply a light application of manure to swell the soil shut before applying a full manure rate to the field.

Manure applications after winter-wheat harvest provide opportunities to remove manure from pits before fall. The dry weather commonly associated with the season reduces the risk of nutrient runoff. Paying careful attention to soil conditions and weather forecast prior to application as well as using cover or double-forage crops will further improve nutrient retention.