Feeding green grass to dairy cows is nothing new, but recent innovations have made it easier to add to diets of high-producing cows. A new practice on several large dairy farms in Wisconsin is proving efficient for harvesting high-quality perennial grasses to add to a TMR for improving cow health and performance, and the farm’s manure/slurry is utilized to fertilize the grass after each harvest.
Doug Sutter, certified crop adviser (CCA) with Wisconsin-based ag equipment provider Vanderloop Equipment, explains how the harvesting and manure application is facilitated. “I am an agronomist by trade, so I come at this from the crop end of it, but I know a dairy depends on healthy, productive cows. If the cows aren’t happy, none of the rest matters,” he says.
“Being able to provide fresh feed is important. Here in Wisconsin during the heat of summer, dry matter intake [DMI] is depressed due to palatability issues and loss of appetite. Fresh feed gives cows a reason to come to the bunk and eat more, which keeps milk production up. On one large dairy farm, this system is saving about 70 cents per cow per day [replacing part of the corn silage and alfalfa] as well as increasing milk production,” he says.
Vanderloop’s role in this innovative project started with manure handling and applying it to the fields. “Our issue in Wisconsin is twofold. We have too much liquid [manure is 95 percent water] and too much phosphorus. The way we address this is to remove the phosphorus and not have to haul the water as far – putting it onto the fields with a hose as opposed to putting it into a tanker, which is costly,” Sutter says.
“Our method of phosphorus removal is low-tech rather than using ultra-filtration or reverse osmosis, which are very expensive. The most cost-effective phosphorus removal we could find is a decanter – a centrifuge that functions horizontally instead of vertically. It revolves at 3,000 rpm and uses centrifugal force to throw solids [in suspended liquid material] to the outside wall. This decanter takes out twice as much solids as a screw press [which takes out about 33 percent]. The decanter takes out about 67 percent,” he says.
The phosphorus goes with the solids; that same proportion of phosphorus is also removed. “With more phosphorus out, we can apply more gallons of liquid per acre without compromising nutrient management plans,” he explains.
“The reason we had phosphorus problems was because whenever we applied manure to a crop to meet nitrogen needs, we overapplied phosphorus. They were not in balance. Now that we can take out two-thirds of the phosphorus before we apply manure to the fields, the nitrogen-phosphorus-potassium ratio falls more in line with the crops’ use of nitrogen-phosphorus-potassium from the soil. We can keep applying the amount of manure we need for appropriate nutrients for the crop. We can go from 10,000 gallons per acre to 30,000 gallons per acre without getting into a phosphorus problem,” he says.
This is part of the equation in making the grass crop work. High-quality perennial grass has high water demands and high nitrogen demands, both of which fit well with the effluent left after using the decanter.
The grass crop is cut five to seven times during the year and has a window of manure application six to eight times per year (which includes before and after the cropping season). This is a big factor for a dairyman who traditionally applied most of the manure in the fall. “Corn silage would be taken off and liquid manure put on the field, hoping it would still be there next July when the new corn crop is growing swiftly,” Sutter says.
This new way of applying manure is perfect for nutrient timing. “We’re cutting the grass every 21 to 24 days and immediately applying manure for the next crop to be taking it up. Our window of possible nutrient loss has shrunk as small as it can; we are putting it on just before peak demand,” he says.
For the grass harvest, there are two approaches. If you already have a chopper for harvesting haylage and corn silage, a direct-cut chopping attachment can be put on the front of the chopper. “The grass can be cut and chopped and put in a wagon to take to the TMR pad where you mix feed,” he says.
Another option is to use the front mower on a triple mower. “To utilize our fresh cut system, one farmer just puts a single deck at the front of the tractor, drives over the cut grass and has a pickup-unit attached to a chopper box. It picks it up, cuts it and puts it in the box, all in one pass. It depends on what you already have for equipment and what is most efficient for your own operation,” Sutter says.
The manure should be applied immediately after the grass is cut and removed, ideally the same day. “With a toolbar called a grassland injector, a press wheel creates a little groove, and a metal disc cuts a slot into the ground so liquid manure can go down into the root zone more effectively. We usually put 5,000 to 6,000 gallons per pass over the field, right after harvest so there’s no risk of injury to the crop, and the plants have access to the nutrients to immediately start growing again,” explains Sutter.
Liquid manure can be applied from a tanker and injected, or with a hose and dragline, depending on which method is most efficient for that farm. “There are ways to do NIR for manure [assessing nutrient components] which agronomically and environmentally is a big deal today. If someone wants to do a prescription for manure application – if they want to put on 60 pounds of nitrogen – they can analyze the manure, and the unit can vary the rate and/or gallons on the go. If you have some dilute manure [from runoff or rain in the pits], it will put on more gallons,” Sutter says. It adjusts the amount of liquid in terms of nitrogen content to match soil needs. This is precise delivery, with no guesswork.
“The buzzword today is prescription; we’re not underapplying or overapplying. We can put on exactly what the crop needs. If you run into a dry period and need to back off on the amount of manure, you can do that and, in optimum conditions with high moisture, you can put on a little more to accommodate what the crop needs,” he says.
“Dairymen like this system because grass is a feed source the cows really like and respond to production-wise, and cost is feasible and production-efficient. Agronomically, we’re using that piece of ground six months of the year, starting mid-May and hopefully into November. Yield per acre and value of that crop becomes as high as any crop we can raise,” says Sutter.
This type of cropping is better for the environment, using perennial grass rather than tilling and planting. “We have year-round cover with no soil erosion. Grass roots are adding to soil health,” he says.
“One reason we’ve gone this direction for dairies is that we have a hard time keeping alfalfa stands alive in Wisconsin because of winterkill or wet summers. Alfalfa is a very expensive crop to establish; seed costs are high. Normally it’s a three-year crop rotation – sometimes four, if you are lucky. With perennial grass, it’s a 10-year rotation, so seed costs drop to 25 percent of what it was with alfalfa because up-front costs are not as high and longevity is better. We might do some interseeding four to five years into it, to fill in thin spots, but we’re not tearing out an entire field to try to re-establish it,” says Sutter.
Grass is also much more tolerant to adverse weather conditions, so it’s an efficient crop for dairymen to put in and leave in. High-quality grasses have a lot of potential for large-scale dairies that need to maintain optimum cow health and production.
