THE MANAGEMENT OF GRAZING

E. Marion Brown

THE MOST difficult problem to be solved in the management of grazing arises from the seasonal differences in the rate at which pasture plants grow. I give a few examples.

Measurements of the seasonal growth of pasture grasses and mixtures in Maryland and Missouri showed that more than half of the total annual yield occurred during the first one-third, and more than two-thirds of the total occurred during the first half of the growing season.

No one crop or seed mixture yet tried in Connecticut supplies uniform grazing, and it becomes increasingly difficult to provide any pasturage there from June 15 to November 1.

In some years all of the annual gain made by beef steers on winter clover-Bermuda-grass mixtures in Arkansas had been made by July; in every year most of the annual gain had been made by that date.

Because winter legume-Bermudagrass-Dallisgrass pastures in Mississippi have peaks of production in spring and fall, the number of animals adequately carried in spring would overgraze the same pasture in the summer period of lessened production.

The productivity of mixed grasses and winter clovers increased rapidly in the Black Belt of Alabama from late March to May, remained high through May, declined during June, remained low through July, rose to and remained at a moderate rate during August and September, and then declined to the March level by the end of October.

So, whether the grazing season is 5 months long, as it is in Maine, or 12 months long, as it might be in Florida, the problem is to provide good pasturage throughout this season.

Saving part of the spring growth for summer and fall grazing is not the Solution, because of the poor quality of mature grass. Chemical analysis, Combined in some instances with feeding trials, have shown that some pasture grasses (such as bromegrass) deteriorate less in quality than others but that all of them are less palatable, less digestible, and less nutritious when mature than when young, vegetative, and actively growing.

When, therefore, hay of the desired quality cannot be made from surplus growth, the size of the pasture and herd should be adjusted to herbage growth during spring, and temporary pastures should be used to supplement permanent pastures summer and fall.

Heavy grazing of Kentucky bluegrass and associated legumes in Missouri from mid-April to early July and again during September and October produced large acre yields of beef but weakened the grass. Close defoliation during the cool periods of spring and fall prevented the synthesis of sufficient carbohydrates to satisfy plant requirements for current growth and for the storage of organic food reserves.

The use of Korean lespedeza for supplementary pasture from July 10 to September 1 increased live-weight gains during the summer, but resting the permanent pasture at that time had little beneficial effect on the bluegrass.

Kentucky bluegrass will benefit from under-grazing or rest both during the cool period of spring, when two-thirds of the total forage is produced, and that of autumn, when less than one-fifth of the total top growth occurs.

Supplemented grazing, whereby the permanent pasture was grazed to capacity from mid-April to early July and at a greatly reduced rate from early July to mid-September, and then rested from mid-September to late November was tried in Missouri from 1941 to 1944. The pasture sward, consisting of Kentucky bluegrass, Korean lespedeza, and volunteer white clover, improved steadily under this grazing schedule and in 1944 produced 250 pounds of beef-cattle gain an acre, as compared with 199 pounds obtained from the season-long grazing of a comparable pasture. Furthermore, the September-October growth was available in the supplemented-grazing pasture for winter feed.

Korean lespedeza grown with wheat, winter barley, or spring oats, each harvested for grain, supplied summer pasture from July 10 to September 30. The average live-weight gain made on this supplementary pasture from 1940 to 1944 by beef steers was 103 pounds an acre.

Feed costs can be reduced and injury to permanent and rotation pastures from too early grazing can be avoided by the use of supplementary pastures in the spring. Rye provides pasture earlier than any other crop. In the middle latitudes, Missouri to Virginia, rye is ready to be pastured a month earlier than permanent or rotation pastures, but in the northern tier of States not more than 2 weeks of early grazing can be gained.

Winter oats, barley, wheat, and rye supply both winter and early-spring pasture in the Cotton Belt. Only light intermittent grazing can be expected from them before February in the northern part of this region, but beef steers gained 139 pounds per head and 190 pounds an acre in northern Florida on winter oats pastured continuously from December 20 to April 20. Ryegrass, crimson clover, bur-clover, vetch, and roughpea, in pure stand, with one of the above cereals, or in Johnsongrass sod also are used for winter and early-spring grazing in the Southern States.

Summer is a period of low productivity for permanent and rotation pastures from Canada to the Gulf coast, and eastward from western Minnesota and eastern Texas, the area to which the management practices discussed here apply and which, although it is large and diverse in soils and climate, has several common problems of pasture management. North of the region within which annual lespedezas can be grown successfully, Sudangrass is the standard supplementary pasture crop from early July to late September. Japanese-millet, second-growth meadow, oats or barley planted as companion crops, and reed canarygrass also can be pastured during summer. From northern Missouri and Maryland to the South, the annual lespedezas fill this gap exceedingly well. Sudangrass, pearlmillet and cattail millet, Johnsongrass, kudzu, and soybeans are also used.

Autumn is a favorable period for root growth and for the storage of carbohydrate reserves by Kentucky bluegrass and other cool-weather perennial grasses. Protection from grazing during this period increases the vigor and prolongs the life of the grass with a minimum waste of forage, for only a small fraction of the annual top growth occurs after mid-September, and this growth can be pastured off after mid-November without harm to the grass.

Annual lespedezas and Sudangrass supply grazing until the end of September. Early-sown rye, winter barley, or oats and first-year sweetclover are usually ready to be pastured by early October. The fall growth in the permanent or rotation pastures can and should be pastured off after frosts in November.

Rotation Grazing

Farm animals never eat pasture herbage down to a uniform height unless compelled by being confined to an area so small that it is pastured out completely within a few days. Without this restriction, spot grazing occurs and the grass first refused is eaten only after livestock have failed to obtain a fill from vegetation shortened by previous grazing. Overgrazing and under-grazing within the same enclosure are the result.

Rotation grazing, whereby the pasture is fenced into two to eight separate enclosures of equal size to be grazed alternately, has been devised to reduce uneven grazing. If there are enough of these enclosures, the herbage can be pastured down quickly to the desired level as soon as it has grown to a height suitable for grazing. Between brief periods of intensive grazing, the sward is protected from defoliation and trampling.

During the spring period of flush growth, individual fields not needed then for pasture can be withheld from grazing and the forage in them harvested for hay or grass silage. Later these fields are pastured in turn, thereby lengthening the rest periods for all enclosures as herbage growth slows up. This practice reduces but usually does not eliminate the need for summer supplementary pasture.

A further refinement of rotation grazing is to divide .the dairy herd, so that producing cows have first access to new growth and dry cows and young stock finish pasturing out each enclosure after the producing cows have been moved to another field.

Each grazing period lasts from 3 to 7 days for each group of a split herd or from 1 to 2 weeks for an undivided herd or flock; and the intervening rest periods will last from 2 to 4 weeks, depending on the number of enclosures, the kind of pasture, and the weather.

Even when rotation grazing is practiced, tall grass will accumulate near droppings. If each field is mowed a day or two before the animals are to be removed, most of this previously avoided grass will be eaten after having been moved by the mower a short distance from the excrement around Which it grew.

Rotation grazing has been advocated for improved permanent pastures in Maine, Connecticut, Rhode Island, New York, Ohio, Illinois, and Wisconsin; for rotation pastures of bromegrass and alfalfa or Ladino clover in Wisconsin and Indiana; and for Sudangrass in Ohio and Georgia. But in each of the experiments in which rotation grazing has been compared With uncontrolled grazing in Maryland, Michigan, Wisconsin, Missouri, and Washington, the increase in production has been too small to justify the added expense of fencing and water supply, unless these could be provided at moderate cost and unless the pasture was high in yield and quality. Rotation grazing may be necessary to maintain in pastures such crops as alfalfa and Ladino clover, although it was found to have no advantage for the pasturing of bromegrass and alfalfa in Michigan.

The Hohenheim system of pasture management provides for grazing rotationally from four to nine fields and for heavy applications of nitrogenous fertilizers to the grass at regular intervals during the growing season. Although yields of dairy products obtained per acre under this system of management have been large, cost has been correspondingly high, so that the increased production has been profitable in some trials and unprofitable in others. Although widely publicized in this country following its use in Germany during the First World War, the Hohenheim system has never been used extensively and it is not now generally recommended, although it might have a limited usefulness under certain conditions.