Florida Agricultural Experiment Station


the winter had a greater ability to produce Sudan grass than:
that from Plot 3 where no cover crop had been planted. The
pecan yields of both varieties as shown in Table 4 were in
rather close agreement with these results, except with Frotscher
in two instances, one with no cover crops and the other where
oats and C. spectabilis were grown.
 However, the amount of nitrogen recovered in the Sudan grass,
 as will be noted in Table 9, followed fairly closely percentages.
 in soils from the various treatments. It is further shown that.
 the quantity of nitrogen recovered in plants grown in soil from
 the unplanted Plot 3 was lowest, while in hairy vetch Plot 2.
 it was highest. As will be noted in Table 2, the greatest amount
 of nitrogen was returned to the soil by hairy vetch and C. spec-
 tabilis in Plot 2 and amounted to 603.4 pounds per acre.
 The availability to the tree of the nitrogen taken up by the
 non-leguminous cover crop of oats evidently is not of the same
 order as the availability of the nitrogen to Sudan grass. How-
 ever, it must be borne in mind that the spring season is a period
 of maximum utilization of nitrogen by the pecan tree, and that
 the nitrogen would not be available from oats during this period.
 On the other hand, the Sudan grass studies were made after
 a long period of decomposition, and the nitrogen effectively con-
 served by the non-leguminous cover was available to some ex-
 tent after a prolonged period of decomposition in the soil.

 DISCUSSIONS AND RECOMMENDATIONS
 The data presented definitely point to beneficial effects of
leguminous cover crops on growth and yield of Frotscher and
Stuart pecan trees on Norfolk fine sandy loam soil. While the-
trees responded to a greater degree where complete fertilizer
applications were made, there were no significant differences
until cover crops had been annually grown and returned to the
soil for four years. Therefore, growers should keep in mind
the fact that it requires several years to revive trees in poor
condition and obtain profitable nut production. Quantity pro-
duction is possible, therefore, with potentially heavy bearing
pecan varieties that would otherwise give light yields, by prac-
ticing a continuous program of annual cover-cropping and judi-
cious fertilization.
 Hairy vetch and Crotalaria spectabilis produced the greatest
amount of green material which contained the most nitrogen
to be returned to the soil, followed closely by Austrian peas.