The Importance of Green Manure Cover Crops and Crop Rotation in the No-tillage System: Experiences in the development of the No-tillage System in Brazil and Paraguay

摘要

Almost all of the advantages of the no-tillage system come from the permanent cover of the soil. Green manure cover crops (GMCC) and crop rotation are essential elements in notillage in order to achieve the amounts of soil cover needed in the system. Also with these practices weed, pest and disease infestations can be reduced significantly (Derpsch, 2003). Research and development activities including green manure cover crops and crop rotation in the 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 strigosa Schreb) was seeded in winter as GMCC before this crop (Derpsch and Calegari, 1992). Also significant maize yield increases could be obtained when mucuna (Mucuna pruriens) was interseeded into de maize crop (Derpsch and Florentin, 1992). GMCC like black oats and mucuna have shown to effectively reduce weed infestation in cash crops (Derpsch, et al., 1985, 1988, Florentin, et al., 2001). Research results obtained in Brazil and Paraguay have encouraged the use of GMCC in practical farming in both countries. Black oats for instance are used on about 3.2 million ha only in the states of Parana 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 has experienced the highest adoption rate. Besides these species more than 20 other species are used regularly in Brazil and Paraguay as summer and winter GMCC, in mechanized and small farmer production systems (Florentin, et al., 2001).