Ineffective StreamPlot output

Question

My command below does not give a very informative StreamPlot. What am I doing wrong? Similar problem with VectorPlot. VectorScale -> Automatic and StreamPoints -> Automatic give unsatisfying results. What could I do better?

StreamPlot[
 {1, 1/5 y (1 - y/3500)},
 {x, -10, 50}, {y, -2000, 5500},
 PlotRange -> {{-10, 50}, {-2000, 5500}},
 StreamPoints -> Automatic
]

VectorPlot[
 {1, 1/5 y (1 - y/3500)},
 {x, -10, 50}, {y, -2000, 5500},
 PlotRange -> {{-10, 50}, {-2000, 5500}},
 VectorStyle -> Arrowheads[0],
 VectorScale -> Automatic,
 StreamPoints -> Automatic
]

Answer 1

This is due to the large disparity in the range on the x- and y-axes. @Rahul created a function to deal with this problem here, which I tweaked here. For self-containedness, I'll copy it below.

Options[myStreamPlot] = Options[StreamPlot];
myStreamPlot[f_, {x_, x0_, x1_}, {y_, y0_, y1_}, opts : OptionsPattern[]] := 
Module[{u, v, a = OptionValue[AspectRatio]},
  Show[StreamPlot[{1/(x1 - x0), a/(y1 - y0)}
    (f /. {x -> x0 + u (x1 - x0), y -> y0 + v/a (y1 - y0)}),
    {u, 0, 1}, {v, 0, a}, opts] /.
    Arrow[pts_] :> Arrow[({x0, y0} + {x1 - x0, (y1 - y0)/a} #) & /@ pts],
    PlotRange -> {{x0, x1}, {y0, y1}}]
]

Applied to your problem:

myStreamPlot[{1, 1/5 y (1 - y/3500)}, {x, -10, 50}, {y, -2000, 5500}]