In my first posting in forage extension, a grazing guru was making a big splash in the popular press touting that rotational grazing will let you double your stocking rate. The logical conclusion is that a grazier could double their income by dividing pastures. To me, this was completely illogical because adding fence changed nothing about the productivity of a pasture. Or does it?    Even the wildest claims can have a grain of truth in them. I now know that whether rotational grazing pays depends on many factors, such as stocking rate, soil fertility status, grass/forage base, and even the size of the grazing animals.

Let’s start with stocking rate. Rotational grazing may allow you to increase your stocking rate if you are severely understocked. It may be difficult to visualize how a field will yield more when rotationally grazing compared to set stocking at very low stocking rate, but research has shown that it can. One study compared the annual productivity of grass at five different grazing intensities from zero to 80%. The plots allowed to grow all season with no defoliation yielded less than those defoliated at 20 or 40%. Non-defoliated plots yielded less because shading caused by the old growth inhibited the emergence and growth of new grass. So depending on the initial stocking rate, rotational grazing may allow a doubling of stocking rate, at least for a while.

Another reason rotational grazing pays is related to the stocking rate effect. When you move from a set stocked pasture to a sub-divided system, you prevent the shading that limits yield. The forage stays in an active growth stage for more of the year, and that fresh growth is green, leafy and very high in quality. Forage quality is therefore nearly always greater under rotational grazing. Rotational grazing lets you eat more of what you grow. Early in the evolution of our understanding of intensive grazing, there was a tendency to graze too close and too often because of this new ability to subdivide pastures. Over time, graziers have learned that high utilization can be overdone. This evolution of understanding has led to the general recommendation of ‘take half and leave half’ as a guide for grazing intensity for grasses. Another guide is to always leave some green leaf area on defoliated forage grasses.

Regrowth in grasses will be faster when there is green leaf tissue left after grazing. This principle is especially true for the more erect grasses like orchardgrass and the native grasses. When defoliation results in bare ground, weeds can encroach and soil temperatures are elevated. This heating is especially detrimental to cool season grasses. Rotational grazing pays because we can incorporate high yielding legumes like red clover and alfalfa into the sward. Rotational grazing allows you to manage for a 30 day period of rest between defoliations which is the key to legume persistence. This 30 day rest is the length of time needed to recharge the carbohydrate reserves in the taproot. This carbohydrate reserve is what drives the new legume growth after defoliation.~ excerpted from article by Dr. Jimmy Henning for Farmers Pride.