This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The next diagram (fig. 331) represents a market garden in which Standard Apples and Rhubarb constitute the only crops. The Apple trees are planted 18 ft. apart every way, thus giving about 134 trees to the acre. Beneath these about 5000 stools of Rhubarb are planted (although 4000 would give much better results). In this case each Apple tree has 36 sq. yd. of space against the 11 sq. yd. in the bush plantation. It therefore makes a much larger head, and produces, at least, two or three times more fruit. Reckoning only 3 bus. of fruit per tree, there would be a yield of 402 bus. to the acre. At 3s. per bushel this represents a gross revenue of £60, 6s.
There are several other ways in which Apple land is under-cropped besides those mentioned, one excellent way being to have the standard trees planted 15 ft. apart every way on the square, and to have three rows of market bush Roses like General Jacqueminot between them.