Material improvement of old plantations may sometimes be effected
and, unless the trees are known to be upward of fifty years old,
generally repays the labor. Marked increase in crop has followed a
heavy thinning out of trees upon the Government cocoanut farm at San
Ramon, Mindanao. The improvement that a freer circulation of air and
abundant sunlight have effected is very marked. Where it can be done,
plowing is also sometimes feasible and should be followed by immediate
crop improvement. The average native plow is not so well adapted for
working over an old or neglected grove as it is for original soil
preparation. It acts more as a subsoiler and will tear and lacerate
more roots than is desirable. A single carabao, or one-horse American
garden plow, is the better implement for this work. Extensive bat guano
deposits are found in Mindoro, Guimarás, and Luzon. Some of them show
richness in nitrogen and, when accessible at a moderate cost, would
be useful in the renovation of old groves, where the shade would be
adverse to the rearing of good crops of nitrogen gatherers.