Cultural Practices for Root-Knot Control


 out of tobacco stalks immediately after harvest and exposing
 the roots to the sun, and of turning the land several times from
 August to November."
 Watson and Goff (7) found that summer fallow, "which con-
 sists in keeping the soil entirely free of all plants during the
 summer," was effective in reducing the nematode population of
 Florida truck lands. Their objection to this method of root-
 knot control was that it depleted soil fertility, and they recom-
 mended rather the growing of an "immune" cover crop such
 as velvet beans or Crotalaria spectabilis.
 Le Roux and Stofberg (4), working in the Union of South
 Africa, reported that a 6-month period of clean cultivation in
 either winter or summer gave commercial control of root-knot
 on at least 1 succeeding susceptible crop. The 2 6-month periods
 which they tried corresponded to October to April and April
 to October, respectively, in the northern hemisphere.

 EXPERIMENTAL
 MATERIALS AND METHODS
 Experiments on fall cultural practices for root-knot control
 were begun at the North Florida Experiment Station in the fall
 of 1937. The field selected was a shade in which 15 consecutive
 crops of cigar-wrapper tobacco had been grown. The soil was
 heavily infested with nematodes, as shown by knotting of roots
 and stunting of plants in the 1937 crop. The soil was a fine
 sandy loam in texture. About 70 percent of the field was of
 the Magnolia series and most of the remainder was of the closely
 related Faceville series.
 Twenty plots of about 1/25 acre each were used for 5 treat-
ments in quadruplicate. The 5 treatments were arranged in ran-
dom order in each 1/ of the area. Each plot consisted of 6
70-foot rows, 41/2 feet apart. Only the 4 inside rows of each
plot were harvested for experimental purposes. Border effects,
such as the transfer of nematodes, were thereby minimized.
The general layout of the plots is shown in Fig. 5.
 The 5 treatments which were begun in July after the 1937
crop was harvested were as follows:
 1. Fallow (roots removed). Tobacco roots pulled and re-
moved from the field; soil kept clean fallow by listing (bedding
and rebedding) at intervals to be mentioned later.
 2. Fallow. Roots not removed; clean fallow.