Restoring the Soil - Canadian Foodgrains Bank

46Decision Tree Guide25. Honduras. Mucuna can also be consumed,once it has been treated to rid the bean of itsL-Dopa (which is a medicine used for treatingParkinson’s disease). Gm/ccs like cowpeas, ricebeans, mungbeans and lablab beans for lowaltitudes, and fava beans, scarlet runner beans andtarwi for higher altitudes, can be consumed withoutthe need to take any such precautions.processing to get rid of the L-Dopa theycontain (Photo 25). On the other hand,for people with Parkinson’s disease,L-Dopa is the drug of choice, so a cup ortwo of coffee each morning, made withwell-toasted mucuna seeds, can providesome relief for those Parkinson’s patientstoo poor to buy pills. If mixed half andhalf with normal coffee, the slightlydifferent taste of the mucuna coffee is notnoticeable.Very likely, mucuna’s popularity is due toits ability to control weeds. It is by far thebest gm/cc species for this purpose. Thefact that farmers have given it so much useand prominence is a major indication offarmers’ priorities: reducing labor demands is very high on their list and manualweed control demands a lot of labor.Most mucunas are superior weed killers because they crawl and climb aggressively.(Photo 13—only the perennial mucuna is a bushy type, but it has notbeen popular with farmers because it often fails to produce seed and it does notcontrol weeds as well.) Generally, we prefer not to use mucuna as an intercrop forthis very reason—it is too difficult to keep it from smothering the crop(s) withwhich it is associated. At first, program personnel and farmers who see mucunagrowing over everything in sight might fear it will become a pest, crawling overand suffocating everything. (I have seen it grow up to the top of a 20 m tall pinetree.) But it is very easy to get rid of. If mucuna is cut below the first branchesbefore it has produced viable seed, it will disappear from a field.Mucuna’s aggressiveness and ability to place its next leaf precisely where it willprevent weeds from getting any sunlight at all are probably what make it sucha superior “green herbicide.” Some people also attribute mucuna’s weed controlattributes partly to allelopathic substances in its leaves that may deter the growthof weeds. Furthermore, the 140 kg of N that is fixed per hectare and high levelsof organic matter production (in some cases as high as 75 MT of organic matter(green weight) per hectare each year) make it a wonderful fertilizer (Photo 12).It also decomposes quickly, like most legumes containing a high percentage ofnitrogen. When the leaves are incorporated into a moist, lowland tropical soil,they will disappear within two to three weeks.Rapid decomposition is usually not desired, because a lot of the nitrogen will bewashed out of the soil (and into the groundwater) as a result. That is one reasonto leave the plant material on top of the soil, or bury it together with the rest ofthe organic matter from the fallow. If the mucuna is planted with crops, we leave