Florida Agricultural Experiment Station


10). When these weeds were cut 6 to 8 inches from the ground
with a rotary chopper many revived sufficiently to produce seed.
Rotary choppers with closely spaced blades would be more suit-
able for controlling weeds (Fig. 19).
 GRAZING
 It has been shown in the preceding pages that fertilization
and liming improve yield and mineral and protein contents of
pasture plants. Quality and yield of pasture plants are in-
fluenced also by grazing management. Minerals such as phos-
phorus, calcium and iron are very essential in the building of
the framework and in the vital functions of the grazing animal,
but they make up only 5 to 15 percent of the plant's total dry
weight. A plant is made up largely of organic compounds
(sugars, starches, hemicelluloses and others) which furnish the
animal food for energy and body building.
 Organic compounds are produced by the plant itself.. The
 green chlorophyll in the leaves combines carbon dioxide and
 water, with the aid of energy from the sunlight, into simple
 sugars. This process is known as photosynthesis. These simple
 sugars are later transformed into starches and more complex
 organic compounds which make up 85 to 95 percent of the plant
 weight.
 Since the leaves manufacture the organic compounds of plants
 the leafage is important in the grazing management to obtain
 satisfactory production and quality of herbage. The primary
 factors to be considered in grazing management are the growth
 habit and the stage of growth of plants.
 Plants possess 2 types of growth habits; the prostrate, such
 as carpet and Bahia grasses, and erect or semi-erect, such as
 Para and Napier grasses or Cattail millet.
 Erect or semi-erect plants will be readily exterminated by
 continuous heavy grazing because cattle remove all or most of
 the leaves. When most of the leaves are kept removed the
 organic food reserves in the plants are utilized faster than they
 are replaced. Heavy, continuous grazing of erect plants will
 eventually deplete the organic food reserves, which will result
 in low yields or death of plants. For proper grazing manage-
 ment of erect or semi-erect pasture plants there should be 2
 or more fields so that the pastures can be grazed intermittently
 or rotationally. In rotational grazing 1 pasture is grazed at
 a time, which allows the others to produce new leafage to re-