Survival and regeneration of four legumes oversown into native grasslands in northeast Thailand

Survival and regeneration of 4 legumes oversown into Arundinaria ciliata grassland and grazed at five stocking rates (2.5, 3.5, 4.5, 5.5 and 6.5 animal units ha over the wet season) were studied. Macroptilium atropurpureum cv. Siratro displayed the highest level of perennation with c40% of plants surviving from the 1st year to the next and 2% surviving into year 4. A density of at least 6 crowns m was maintained at the lowest stocking rate but loss of persistence occurred at higher stocking rates. Siratro had the highest seed reserves (74 kg ha) and a high initial seedlings density after the first year. Stylosanthes hamata cv. Verano and Stylosanthes guianensis cv. Endeavour performed as weak biennials with a mean survival of 17 and 9%, respectively, from the 1st year to the next. Both species relied predominantly on seedling recruitment for persistence and in Verano this was satisfactory for the first 3 yr at 60-125 seedlings m. However, this decreased in the 4th year as stresses during the growing season reduced mature plant density and seed formation. Endeavour was unsuccessful in this environment due mainly to late flowering during the dry season. Stylosanthes humilis cv. Lawson performed as an annual and disappeared after the 3rd year due primarily to a severe attack of anthracnose disease (Colletotrichum gloeosporioides). -Autho