Florida Agricultural Experiment Station


and oats and C. spectabilis in winter and summer respectively,
annually thereafter, the total nitrogen returned by the two
legumes amounted to 237.0 pounds per acre.
 The nitrogen in the soil of Plot 4, in which the cover crops
 consisted of a winter non-legume and a summer legume, although
 highest of all for the 0-9 inch depth, evidently was not in an
 available form during the maximum growing season and could
 not be utilized. Growth and yield of trees were significantly
 greater in Plots 1 and 2 in which legumes were grown annually
 in winter and summer. However, it should be pointed out that
 hairy vetch was grown on Plot 4 the first year and produced
 13,400 pounds of green material per acre and that the crotalaria
 was heaviest in this plot each year except 1928 and 1931. The
 nitrogen returned was no doubt fixed in the soil by the oats,
 and it was thus unavailable to the trees and probably accounted
 for the poor results in Plot 4.
 TABLE 9.-EFFECTS OF COVER CROPS ON THE BASIC FERTILITY OF THE SOIL
 AS DETERMINED WITH SUDAN GRASS GROWN IN VOLUME SAMPLES TAKEN
 IN THE PECAN EXPERIMENT IN 1934*.
 Organic Dry Weight
 I Nitrogen Matter of Sudan Nitrogen in Sudan Grass
 Plot** in Soil in Soil Grass Sudan
 Avg. percent Avg. percent Avg. grams IAvg. percent Avg. grams
 1 0.049 2.34 11.6 0.54 0.063
 2 0.059 2.68 14.8 0.51 0.075
 3 0.047 2.48 8.1 0.56 0.045
 4 0.055 2.78 11.0 0.63 0.069

 These were taken with a volume sampler which gave a cube of surface
 soil 6x6x6 inches. The soil was passed through a two millimeter sieve
 before determinations were made and the Sudan grass planted.
** See Table 2 for cover crops grown in each plot.

 Organic Matter:-By referring to Table 8 it will be seen that
the organic matter content of the surface soil, as determined
by loss on ignition, was higher in 1933 than in 1928 in all planted
plots except 2, and that it was lower in the unplanted Plot 3.
The greatest increase in organic matter occurred in the 0-90
inch soil sample from Plot 4 where the most Crotalaria spec-
tabilis was grown and returned. It should be pointed out that
the rough organic materials in pecan soils are important, en-
couraging bacterial activity while decaying and also helping
somewhat in moisture conservation. Well decomposed organic
material after it becomes thoroughly incorporated as an integral