Be Ready for the Spring Pasture Flush!

Crop and Soil Environmental News, February 1999

Paul R. Peterson
Extension Specialist, Forages

As burned up as pastures were last summer and fall, it is difficult to imagine that some day soon we will be faced with an overabundance of lush spring pasture. How we manage this period of high pasture productivity is critical. In a period of abundant growth, it might seem that we can get by with less management attention. However, our spring grazing management affects not only the degree to which we effectively utilize that growth, but also pasture performance for the remainder of the season.

Spring is when pasture growth in uncontrolled grazing situations gets most out of control. With cool-season pastures, the supply of available pasture forage reaches its peak during the spring. Too often, rather than make management efforts to utilize this abundance of spring forage, we are content to spend excess time and money in early summer brush-hogging the overmature forage that was wasted in the spring.

Typically, cool-season grass-based pasture systems are stocked conservatively, at a rate that the producer feels his farm can support during the summer months when cool-season species are lower in productivity. As a result, most pasture systems are understocked during spring. The resulting abundance of available forage allows grazing animals to fully express their selectivity. While rotational stocking gives us the higher stock densities that enable us to better control and utilize rapid spring growth, we can still end up wasting a lot of forage if we don't have a plan for managing it.

Several things should be kept in mind when animals are first "turned out" in the spring:

1. Turn out earlier than you think. One of the most common mistakes in managing spring pasture is turning animals out too late. If you use rotational stocking and wait until you have adequate growth in your first paddock to feed the herd for a full grazing period, you are too late. By the time you've gotten half-way through your paddocks, your ungrazed paddocks will be overgrown and overmature. One case where you may want to delay turn out until significant forage is available in your first paddock is with spring-freshened dairy cows, where forage availability is critical. Probably a better alternative though is to turn these cows out and begin rotating just as spring growth begins, supplementing cows with high quality hay or haylage or more concentrate until accumulated pasture growth is adequate.

2. Graze unhayable paddocks first. Unless you stock your grazing system more heavily for spring, even with good grazing management, chances are good that you will have to cut some paddocks for hay to control pasture growth. Since this situation is likely to occur, it is best to begin grazing in paddocks where haying would be most difficult, eg. steep slopes.

3. Rotate rapidly. Cool-season grasses are at their most rapid rate of growth of the year during the spring. The general rule of thumb that relates frequency of rotation to pasture growth rate is often a good one. If you rotate rapidly during the spring, the percentage of standing forage that you utilize will gradually decrease in your effort to keep paddocks topped. This is not a problem, however, because it enables you to essentially "stockpile" more forage for summer by leaving more residual.

4. Stock more heavily in spring. A system that can work well in a spring-calving cow-calf operation is to retain some weaned steer calves through the winter and graze them with or ahead of the cow herd during the spring. After cool-season pasture growth rate begins to decline in June, steers can be shipped, dropping the stocking rate on the farm to better match the lower pasture production anticipated during July and August.

The amount of pasture forage actually consumed over a growing season with continuous stocking is only about 35% of what is produced. In contrast, pasture that is rotationally stocked with 1-3 day rotation intervals typically has over 70% of the growth consumed. This difference is due largely to more effective use and management of the spring flush with rotational stocking.

The additional problem that occurs if spring growth is not well managed is that too much selective grazing can occur, resulting in an excessive patchwork of over- and under-grazed areas. Diverse pastures are never (nor should they be) grazed to a uniform height. Attempts to achieve completely uniform utilization result in overgrazing of the most desirable pasture species. Overgrazed areas are often repeatedly overgrazed with each grazing cycle and thus have chronically reduced productivity during the remainder of the grazing season. In contrast, the undergrazed areas continue to be avoided by grazing animals, unless close mowing is performed to encourage new vegetative growth in those areas. With ineffective spring management, this pattern of under/over-grazing is maximized.

Another common mistake is to apply nitrogen to pastures in the spring. Since spring is the period when we often have more growth than we can effectively utilize, applying N not only exacerbates the problem, but it also discourages the ability of higher quality, N-fixing legumes to persist and contribute to the pasture canopy. In spring, nitrogen should be applied only in grass paddocks where hay cutting is anticipated. For pasture, save your nitrogen fertilizer for stockpiling.

It is difficult to avoid making a pass with the brush-hog over some paddocks at least one time during the year. However, we need to be careful not to brush-hog just for aesthetic reasons. While not as expensive as some other equipment operations, brush-hogging still does take time, fuel, and wear-and-tear on equipment. Paddocks that may appear from the road to have too many overmature plants remaining after a grazing period, may really be pretty well utilized when viewed on a walk through the paddock.

Don't be in a hurry to brush-hog after the first grazing cycle. This is often a wasted trip. Generally, if brush-hogging is necessary, it is better to wait until after the 2nd or 3rd grazing cycle when the grasses propensity to produce seedheads is over.

It is also generally not a good idea to force animals to "clean-up" overmature forage, regardless of what type of animal or stage of production, because they will generally selectively overgraze other areas before they will touch the stems and seedheads of overmature plants. It is better to try to stay ahead of maturation as much as possible and cut hay or brush-hog to take care of what gets away.

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