SUMMARY
 Over a period of 20 years, a total of 13 different pasture pro-
grams were compared. Variables considered were three grass
varieties, clover, native range, irrigation, fertilization rates,
renovation, and combinations of these factors. The different
pasture programs were evaluated by grazing with producing
cows and calves included in a comparison of five mating systems.
Caged clipping plots were used to estimate forage production.
Supplemental studies were made to assess both the accumulation
of organic matter and fertilizer nutrients and also the need for
annual application of N and K.
 With proper liming of the soil and annual fertilization ex-
cellent clover-grass pastures were maintained in nearly a steady
state of production over the 20-year period. The most economical
level of fertilization for maintenance of these pastures was 300
pounds of 0-10-20 annually. This was the lowest rate tested.
 The carrying capacity for cattle for all of the clover-grass
programs was approximately 1.3 acres per cow for grazing from
approximately March 1 to December 1. An additional 0.2 acre
was needed to produce corn silage for winter feed. Estimated
forage yields from caged plots and published dry matter require-
ments for producing cows and calves suggested that there was
little wastage of the pasture forage produced. The production
performance of cattle in the five mating systems compared
showed an annual production per cow during Phase 3 that was
99% above that of the native cattle from which they descended.
This increase apparently resulted mostly from hybrid vigor due
to crossbreeding and intense selection for fertility, growth rate,
and maternal ability. Differences between the five mating sys-
tems were highly significant for size and growth rate. Annual
production per unit of cow weight, however, varied only from
39% to 41%, suggesting no significant differences in total pro-
duction efficiency.
 Economic analyses showed none of the all-grass programs to
be economical under the conditions of these trials. Clover-grass
programs fertilized at rates varying from 300 to 600 pounds of
0-10-20 annually showed positive net returns. Production costs
vary sharply with time, however. The physical inputs and pro-
duction responses reported herein should be considered in light
of prevailing costs in extrapolation of the results.