This may be a start:
Manipulate[ StreamPlot[{x^2 + y + x y, -((363889 x)/5000) - 10 x^2 + (3 y)/ 2000 + (11 x y)/5 + (7 y^2)/10}, {x, -k, k}, {y, -9 k, 9 k}, StreamScale -> None, StreamPoints -> Fine], {k, .1, 20}]
