Sid Bosworth, Extension Associate Professor,
Department of Plant and Soil Science, University of Vermont firstname.lastname@example.org
The next set of questions that often come up involve pasture improvement. Pasture “improvement” can mean different things to different people. For instance, pasture improvement may mean in increase in existing pasture yield, thus, increasing the potential carrying capacity of the pasture system. This is certainly an important consideration for many producers that would like to utilize grazing but are concerned that their pastureland is too limiting in area for their number of cows. Pasture improvement may also mean an increase in pasture quality such that milk production is increased or supplemental feed is decreased. Either way can improve profits. Pasture improvements may also mean an improvement in the seasonal distribution of dry matter so that animal needs are met throughout the season.
Besides grazing management, the two primary practices that can improve the productivity of pasture involve 1) soil amendments to improve forage growth and 2) the introduction of new species and varieties to improve productivity, quality and seasonal distribution. A third practice often considered is weed and brush control either by clipping or by chemical method. In some instances, subsurface drainage is a viable option and, on a few farms, I’ve seen irrigation used as a way of improving summer productivity of pasture.
The big question for all of these practices is “Are they worth it?” You can only answer that question for your particular situation. In light of today’s milk prices, whatever practice you put in place, you’ll certainly want to get the most bang for the buck. So, for whatever its worth, here is my take on these practices.
Soil test - Before applying any soil amendments, it makes a lot of sense to soil test and determine if there is even a need for lime or nutrients. Our most probable and apparent return on fertilizer investment is usually when the soil is low in fertility. If the soil is already adequate for a particular nutrient, it would be a waste of money to add any more.
Lime - If needed, liming to raise soil pH will probably give us our best return on our investment. Not only do plants grow better at a pH of 6 to 7, but most nutrients are most available in the soil. Also, soil microbes which are important for releasing many nutrients from organic matter grow best at this range of pH.
P and K Fertilization –Although most dairy farms in the northeast import most of their nutrients with supplemental grain, it may still be important to “jump start” the pastures with some initial fertilization if soil tests show a need. However, once up and running many dairy pasture programs need very little supplemental P and K fertilization. You may not see an immediate or dramatic improvement in pasture growth after adding P and K fertilizer. It’s most important function is in helping to maintain legumes in the stand. When P and K levels are low, legumes are more vulnerable to be out competed by the grasses, which are much more efficient at extracting P and K from soils.
N Fertilization – When a stand is predominately grass and there is adequate soil moisture, you’ll often see a growth response to N fertilization when applied at a rate of at least 50 lbs of actual N per acre. Grasses love nitrogen. It stimulates leaf and shoot growth and often boosts crude protein levels. It’s affect is usually immediate and does not last very long. In fact, I look at nitrogen applied to grass as more of a short-term management tool. If you need additional growth during the season, N can be a relatively cheap way to get it. When you’ve got plenty of growth (like in the spring), you probably don’t need it.
There are at least three factors to consider in deciding whether to use nitrogen. First, the soil needs to have adequate moisture for grass growth. Appling N during a dry summer is usually a waste of money. Second, if a pasture consists of at least 30% to 40% legume, there will be no or little growth response to added nitrogen fertilizer. In fact, N fertilization will usually cause a decline in legumes, which can impact animal performance. Third, some grass species found in native pasture may not respond to N as well as improved species. Some common examples include sheep fescue, red fescue, and velvetgrass. If these are predominate species, it may be time to consider major pasture renovation.
Overseeding Legumes – Legumes provide many benefits to a pasture system. Legumes do not need any nitrogen fertilization. They improve the seasonal distribution of forage dry matter by boosting summer production and they improve protein levels and overall digestibility of the forage. Probably the most economical and commonly used legumes for pasture overseeding include red and white (ladino type) clovers. Birdsfoot trefoil is another more persistent legumes that has been successfully overseeded. Seeding rates typically are 2 to 4 lbs per acre for red clover and trefoil and 1 lb for ladino clover.
Whether you broadcast seed in early spring (“frost seed”) or use a drill to place the seed in the soil, a key to successful overseeding depends greatly on how the existing vegetation is managed (suppressed). The grass growth must be controlled. First, it’s best to overgraze the field the previous fall. This grazing “abuse” will provide openings in the sod for clover or trefoil emergence and set back the sod's vigor the next spring. Overseed in early spring after the snow is gone but while the soil is still frozen. The freezing and thawing cycles helps to work the seed into the soil.
Animals can also be used to control early spring growth. In fact, the hoof action will assist natural late winter freezing and thawing to work the broadcast seed to a desirable depth for germination. Cattle could be kept on the area for a few days after overseeding but should be removed from the field before clover seedlings emerge.
After legume emergence, the animals can be brought in to graze as part of the normal rotational grazing scheme. A quick but moderate grazing is best in which animals are on the area for less than a day and removed just before the new clover seedlings are grazed (3 to 4 inches left). DO NOT APPLY ANY NITROGEN FERTLIZER either the fall before or during the year of establishment. This only stimulates the grasses and discourages the developing legumes.
Overseeding Grasses – If your pasture mainly consists of unproductive native grasses, there may be a benefit of introducing improved grass species and varieties. Again, frost seeding is a viable economic approach but only works for quick germinating grasses such as ryegrasses or orchardgrass. Research from the University of Wisconsin showed that overseeding ryegrass into native pasture did not improve pasture productivity but it did replace existing grasses with the better quality ryegrass but only in years when moisture was adequate for ryegrass growth. One warning – ryegrass is not as winter hardy as other cool season grasses so persistence may be a problem.
Complete renovation – You may have a situation in which the existing pasture is so poor, the best option is to completely renovate the site. This would include the addition of soil amendments, tillage and/or herbicides to kill existing vegetation, and reseeding. This is certainly the most expensive option, but may have the most beneficial long-term impact. It would allow you to incorporate lime and nutrients into the soil and seed the most appropriate pasture mix for your site and situation.
Weed Control –There is really little economic incentive to control weeds until proper grazing management, soil fertility and pasture species are in place. Except for a few invasive species, most weeds are opportunistic beings taking advantage of an open patch of soil or light. On the other hand, avoiding seed production with a few timely clippings can be a good prudent and inexpensive practice particularly if the weed is a problem perennial.
Soil Drainage – This is certainly a long-term investment that can have a large benefit to pasture. With low cash flow, it may not be a viable option but it is worth checking with USDA-NRCS to see what cost share programs are available to do some selected drainage on pasture.
Priorities and Starting Slow
When looking over the whole farm and pasture system, it is very likely that you can divide you system up into several management units according to soil type, slope, field history, etc. Then prioritize which practices will give you the best bang for the buck in each of these areas. Some areas may only need good grazing practices with no additional inputs. Others may do fine with just a little lime or a legume frost seeding. Others may need complete renovation.
The reality is that you will probably not know which is best for you until you’ve been grazing for two or three years. Only then will you be able to identify the weakest links in your production system. So start slowly.
This site is maintained by Sid.Bosworth@uvm.edu, Plant & Soil Science Department, University of Vermont.
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