Richard Taylor, Extension Agronomist; rtaylor@udel.edu
Last year there were a number of questions concerning the use of a technique called top cutting, in which the tops of the seed heads of cool-season grasses were removed using a bush hog or rotary mower raised high enough to clip the upper 1/3 to ½ of seed stalk. The word going around was that it would stimulate new growth and improve both forage quality and quantity. I asked a number of forage experts about the practice last year and the consensus was that the practice was unlikely to offer any benefits to grazers at all.
This year I was surprised this past week when another unique practice was employed on a very large area of pastures near my home. In this case, the mower was lowered to remove the top 2/3 of matured growth but instead of mowing the whole pasture random paths were cut through the pasture (see Photos 1 and 2).
The question on my mind is what advantage this type of mowing pattern offers the grazer? The many pastures on this farm are used to graze both cows and horses in a continuous grazing system. One idea was that the paths gave the livestock pathways to move around the pasture but in observing the pastures during the past week I have not seen any tendency of the cows or horses to preferentially use the pathways. As visible in the photos, regrowth of the pasture grasses is occurring so that some improvement in quality forage is occurring and at some point the livestock will make use of the new growth which will be much higher in crude protein, digestible dry matter, and lower in acid and neutral detergent fiber.
Another less serious idea raised by a producer that I asked about this type of practice was that the person mowing the pastures was less than sober or was out having fun. I did watch the mowing process long enough to determine that the mowing was being done deliberately; and, considering the number of acres mowed, it was done purposely.
Photo 1. Random paths mowed through beef and horse pastures
I do have a question for the grazers who may read this article. That question is whether they can think of some reason for this type of mowing process. If you can think of a purpose for this procedure, please email me with your thoughts as I would like to know what this type of procedure can accomplish.
Photo 2. Random paths mowed through beef and horse pastures and showing regrowth of pasture grasses
While on the topic, mowing pastures is one of the very useful management techniques a grazer has to both improve pasture and feed quality and to stimulate new production from the pasture grasses. When continuously grazing as is done in the above situation, mowing is most effective when done shortly after full emergence of the seed head on the majority of the pasture grass plants although many producers do not mow until full flowering or even later. Delaying the mowing operation too late can delay new tiller development and deplete root and crown energy reserves as seeds begin to develop and draw energy from the storage organs. In rotationally grazed pastures, mowing is often replaced by hay making on any unused grazing cells or paddocks. In cells used for several grazing cycles, mowing is often needed to remove grass that is overly mature due to preferential grazing of some grasses or to avoidance of dung areas. In all these cases, mowing removes old growth and stimulates new tiller development and improved forage quality and productivity.