mulches. They found that herbicides killed 50% to 70% of the mulches but corn yield was reduced 5% to 10% at the end of the harvest. Although leguminous cover crops have large biomass production and turnover, they are not likely to increase soil organic matter. This is because legumes used as living mulches have greater N contents and a low C to N ratio. So when legume residue decomposes, soil microbes have sufficient N available to enhance their breakdown of organic materials in the soil. Types In the tropics, it is common to seed tree crops with living mulches such as legume covers in oil palm plantations, coconut and rubber. In Mexico, legumes used traditionally as living mulches were tested as nematode and weed suppressors. The mulches included velvetbean (Mucuna pruriens) jackbean (Canavalia ensiformis), jumbiebean (Leucaena leucocephala) and wild tamarindo (Lysiloma latisiliquum). Aqueous extract of Velvetbean reduced the gall index of Meloidogyne incognita in the roots of tomato, but suppressed tomato rooting as well. In addition, Velvetbean suppressed the radical growth of the local weeds Alegria (Amaranthus hypochondriacus) by 66% and Barnyardgrass (Echinochloa crus-galli) by 26.5%. Nicholson and Wien (1983) suggested the use of short turfgrasses and clovers as living mulches to improve the resistance soil compaction. These authors established Smooth Meadow-grass (Poa pratensis) and white clover (Trifolium repens) as living mulches since they did not cause reduction of yield corn (the accompanying main crop). In one study, chewing fescue or red fescue (Festuca rubra) and ladino clover (Trifolium repens) were effective living mulches for controlling weed growth. Unfortunately, these cover crops also competed with corn for water which was particularly problematic during a dry period. The possibility of using ladino clover (Trifolium repens) as a potential living mulch was also mentioned; however, this clover was difficult to kill with herbicides in winter. Management Because they compete with the main crop, living mulches may eventually need to be mechanically or chemically killed. It is important to judiciously select the appropriate herbicide rate for burning down a living mulch. In 1989, Echtenkamp and Moomaw found that herbicide rates were inadequate to suppress all the living mulches. Therefore, the mulches competed with the main crop for resources. In some cases, the clover could not be killed at the first herbicide application, so a second application was needed. For another treatment, rates that were so high that they caused the cover crop to