The Importance of Green Manure Cover Crops andCrop Rotation in the No-tillage System. Experiencesin the development of the No-tillage System inBrazil and Paraguay

摘要

Almost all of the advantages of the no-tillage system come from the permanent coverof the soil. Green manure cover crops (GMCC) and crop rotation are essential elements in notillagein order to achieve the amounts of soil cover needed in the system. Also with thesepractices weed, pest and disease infestations can be reduced significantly (Derpsch, 2003).Research and development activities including green manure cover crops and crop rotation inthe no-tillage system started in Brazil in the late 1970’s and in Paraguay in the late 1980’s.Significant yield increases of soybeans could be obtained when black oats (Avena strigosaSchreb) was seeded in winter as GMCC before this crop (Derpsch and Calegari, 1992). Alsosignificant maize yield increases could be obtained when mucuna (Mucuna pruriens) was interseededinto de maize crop (Derpsch and Florentín, 1992). GMCC like black oats and mucunahave shown to effectively reduce weed infestation in cash crops (Derpsch, et al., 1985, 1988,Florentín, et al., 2001).Research results obtained in Brazil and Paraguay have encouraged the use of GMCC inpractical farming in both countries. Black oats for instance are used on about 3.2 million ha onlyin the states of Paraná and Rio Grande do Sul, Brazil and on about 300.000 ha in Paraguay,mainly in mechanized farming systems. On small farms mucuna is the species that hasexperienced the highest adoption rate. Besides these species more than 20 other species areused regularly in Brazil and Paraguay as summer and winter GMCC, in mechanized and smallfarmer production systems (Florentín, et al., 2001).