= SUGGESTIONS FOR PAPER-MULCH TRIALS 3 
doubtedly require the same research, resourcefulness, and industry 
that brought about its successful development in the Hawaiian Is- 
lands. Present paper costs are deemed to limit the application of 
the system in this country toe the more intensive phases of our agricul- 
ture, but for these it appears to merit serious study. 
The present circular is intended as a guide to growers interested 
in the practical possibilities of paper mulch, who are desirous of 
ascertaining through small trials whether or not they may make 
economic use of the stimulation of plant growth and other advantages 
which frequently result frem the application of paper mulch. 
SOIL CONDITIONS IN RELATION TO PAPER MULCH 
The trials with paper mulch have not as yet indicated the desir- 
ability of any one particular method of soil preparation for general 
use. It is quite possible that on account of the modified soil condi- 
tions accompanying the use of paper mulch the present practices in 
relation to certain crops on unmulched soils may undergo some 
change. Nevertheless, such changes may be expected to develop 
gradually with further practical experience. For example, soil- 
moisture conditions produced under the mulch may be of such im- 
portance where irrigation or dry-land agriculture are practiced, or 
in regions of excessive rainfall, that a modification of present technic 
may “be practicable and advisable. Or, again, the effectiveness of 
the paper in bringing about the rapid decomposition of weeds may 
possibly be utilized in the development of a modified system of green 
manuring. Further, the protection afforded by the use of certain 
types of paper against the packing of heavy soils by winter rains 
and snows may p yermit advantageous fall preparation of the soil for 
early spring planting of certain crops. On soils described as “ cool 
and moist,” however, the special desirability of applying the paper 
over slightly ridged beds has been shown to be due to the fact that 
under these conditions the soil temperature was increased through 
the reduction of evaporation and through heat absorption. Ai the 
same time the soil moisture was not unfavor ably increased, as some- 
times happened on such soils with paper and flat culture. 
Little is known regarding the relation between the use of paper 
muich and the application “of fertilizers. The initial paper-mulch 
trials have indicated that the poorer the soil the greater the percent- 
age difference between the mulehed and the unmuiched crop. Even 
with a relatively great increase in yield resulting from the mulch the 
yield might still “be unprofitable. The absolute difference between 
mulched and unmulched crops increased with fertility. It is deemed 
entirely reasonabie to look to the paper mulch for an increase in 
soil moisture and soil temperature. In so far as these factors ma ay 
promote growth directly, well and good; but their indicated s 
ondary effect in promoting the activity of favorable microor ganisms 
in the soil, leading to an need production of nitrates, can take 
(9 place only through the same reduction of the organic materiais in 
the soil which characterizes all the usual practices. The introduc- 
tion of paper mulch into the pineapple-growing industry did not 
result in a reduction of the applications of manures or commercial 
fertilizers, but it did enhance the effectiveness of any added fertility. 
