Residual herbicides pose a risk to the environment if applied to waterlogged soils. Residual herbicides don't work well on cloddy soils because the chemical is poorly distributed. Plough before mounding to break up the clods. If applied to freshly cultivated soil, they may leach rapidly and be less effective. Many mound ploughs used to prepare sites for tree planting are fitted with a roller to help consolidate the mounds.
Flattened mounds are also easier to walk along when planting.
The advantages of granular herbicides include lighter weight when spreading, no spray drift, and no uptake by foliage. For best results apply granules to moist soil, ahead of penetrating rain. Economics of second year weed control Second year weed control usually increases tree growth, but is only economic if the extra growth offsets the cost of the operation, or if needed to ensure the trees' survival. It is most likely to be profitable for trees that have grown poorly in the first year, on sites with prolific weeds. Spraying is probably not justified in tree stands with high growth rates.