Agriculture Reference
In-Depth Information
blowing away. Coarse bark proved very effective in orchard establishment
trials and with young orchards in Washington State.
Shredded paper also provides good weed suppression but can be difficult
to apply and must be replaced annually. Spray-on mulches made from slur-
ries of shredded paper pulp suspended in water have provided very good
weed control in orchards, but they require expensive mixing and spraying
equipment and tend to be challenging to apply. When using paper mulches,
be sure that the paper does not have glossy or colored inks. Spot treat-
ments using hand cultivation, steam weeders (not flame!), and organic herb-
icides are typically needed to control weeds, particularly at the edges of the
mulches.
Advantages.
In some situations, organic mulches can be useful to orchard-
ists by lowering soil temperatures, conserving soil moisture, and reducing the
need for irrigation. Organic mulches can also add nutrients and organic mat-
ter to the soil, and some provide favorable environments for beneficial in-
sects and microorganisms. In some cases, organic mulches have been found
to increase populations of beneficial nematodes while reducing populations
of plant parasitic nematodes.
Disadvantages.
Organic mulches do not provide complete weed control and,
when contaminated with weed seeds, insects, or diseases, can actually in-
crease problems. Grass hays and alfalfa hay harvested after flowering, for
instance, often contain large amounts of seeds and are not generally re-
commended for mulches. Perennial weeds, such as quack grass and Canada
thistle, are especially troublesome in mulched fields because of their
rhizomes. Rhizomes can spread quickly in some organic mulches, particularly
sawdust or compost. Organic mulches, especially straw, can also harbor mice
and voles, increasing the risk of girdling damage to orchard trees. When us-
ing agricultural and municipal wastes as mulches, contamination with pesti-
cides can be a problem. Before using any materials, make sure they are
pesticide-free.
