I'm afraid it's not quite as simple as plant and forget - Christmas trees need constant maintenance if you want a fairly high yield from them
They will need annual shaping ideally once they get up a bit although this is not strictly necessary
Weed and pest control is paramount - deer and rabbits will need to be kept out at all costs or they will decimate your crop in no time, so factor in the cost of suitable fencing as an initial expense
Weed control to begin with is best done by ploughing the field prior to planting - single furrow at 1m spacing is ideal
You will need to use a selective weedkiller round the base from year two on to stop weed competition and also to stop the bottom branches going bare
A small amount of nitrogen fertilizer to keep them a nice green colour may also be required depending on soil type - not too much though fast growth should not be encouraged or the trees will get too leggy
NS will happily grow in exposed conditions as will all the other favouites, blue spruce, nordmann fir, scots pine etc - these species also command a price hike over NS due to low needle drop
Spacing for planting should be at 1m intervals along the furrow giving 10,000 trees / ha - they won't ALL survive to make good christmas trees though - culling to keep the best is important
Buy your trees as bare root stock from tree growing nurseries - they should cost around £150 - £250/ 1000 depending on species
A chat with the Christmas tree growers federation may help too
Hope this is of some use to you
Good luck !