Furthermore, it takes extra care with cropping annual plants to keep the soil in good tilth with a high organic matter content. Hemp fields need to be rotated with soil-building crops to maintain soil quality. Herbaceous perennials, on the other hand, generally build soils rather than deplete them. Some of the highest-producing biomass plants come from wet lowland areas. Examples are papyrus, cattails, rushes, water hyacinth, etc.
Wetlands have some of the highest nutrient loads in the landscape plus lots of water.
High biomass yields from wetland species are not surprising, given these conditions. Special equipment would be needed to carry out harvests in moist habitats, however. Presently under-utilized crop wastes could support a large paper industry without even putting new land into production. For example, large amounts of grass straw 4 are burned every year in Washington and Oregon by seed producers. Paper production is one possibility being looked into by the grass seed industry for alternative uses of the waste straw.