library(deSolve)
## Warning: package 'deSolve' was built under R version 3.3.2
Lvcomp2 <- function (t, n, parms) {
  with(as.list(parms), {
    dn1dt = r1*n[1]*((k1-n[1]-alpha*n[2])/k1)
    dn2dt = r2*n[2]*((k2-n[2]-beta*n[1])/k2)
    list(c(dn1dt, dn2dt))
  })
}

parms <- c(k1=100, k2=50, r1 = 0.2, r2 = 1, alpha = 1, beta = 1)
initialN=c(1, 3)

out <- ode(func = Lvcomp2, y = initialN, parms = parms, times = 1:100)

matplot(out[,1], out[,-1], type = "l")