MECHANICAL DEWATERING OF FORAGE CROPS

 by J. W. Randolph, J. P. Winfree and V. E. Green, Jr. /


 Water within a forage crop has no feed value and it can restrict the most
effective and efficient utilization of crops or livestock feeds.

 Mechanical dewatering, or artificial wilting, is an old process that may
be found in many applications about a farm home. The system herein considered
for the partial and preliminary drying of forage materials is carried out with
equipment which may be described as a modified kitchen meat grinder greatly
enlarged.

 One modification is forcing the discharge, which we call a "press-cake",
around a choke-cone that replaces the perforated end-plate. Another variation
in design is the substitution of a screen for the solid wall cylinder around
the screw which has a variable pitch. "Press-liquor" is used to designate the
fluid that is forced through the screen cylinder.

 Why Dewater?

 The normal growth cycle of a plant starts with high succulence and high
quality feeding values and it progresses more or less rapidly into a condition
of high fiber content and low feeding values. If the harvest is delayed, the
losses in nutrients may continue to a worthless condition. The progressive
changes in the moisture relationships within a crop are influenced not only by
the stage of maturity but also by moisture conditions as content of soil and
atmosphere. Both moisture factors are generally unfavorable in south Florida
when the crop should be harvested for maximum value.

 The normal use of moisture percentage data frequently fails to convey the
 true significance of "feed-dilution" as it may apply to pasture grasses or to
 the feeding of green-chop forage. In either case, the actual economic value of
 the green crop may be limited by the volume-intake-capacity of a cow. Table 1
 illustrates the significance of moisture percentage on the total green material
 required for 20 pounds of dry matter intake.

 The data in table 1, for the higher moisture relationships shows total
 quantities that exceed the intake capacity of a 1,000 Ib. steer, which might
 have a daily weight gain of 1.25 to 1.75 pounds if the dry matter had less water
 dilution. It is apparent that ust-too-much-water' in a forage feed can cause
 cattle starvation when a pasture crop is very succulent.

 Preliminary tests at the Everglades Station and large-scale use of screw
 presses have shown that grasses and legumes, recovered from a standard forage-
 crop-harvester, can be mechanically dewatered without additional treatment into
 a press-cake with 70 percent moisture. This means that a steer may obtain 20
 lbs. of dry matter by removing 200 .-'66 .- 134 lbs~ les 'water from greenchbop
 press cake ;containing 70% moisture than from'green chop'that contains 90%
 moisture.



 I/ Agricultural Engineer, Assistant Soils Chemist and Associate Agronomist,
 respectively, Everglades Experiment Station, Belle Glade, Florida