The economic spacing of trees and other crops
利用密度相关产量函数，分析改变作物密度的盈利条件，发现存在一个“惰性区间”，在此区间内维持现有密度最有利，该发现对农业政策有重要启示。
Density related yield functions are used in this paper to consider the conditions that determine the profitablity of increasing or reducing the density of crops. The optimal density of the crop when densities need to be increased to raise profit is shown to be usually less than the profit-maximising density when densities need to be reduced to increase profit. It is shown that when actual densities fall in a particular density band or range (which straddles the density for which yield per hectare is at a maximum) profit is maximised by leaving the existing density unchanged. This range or band is described as an ‘inert’ area. Determinants of the width of this band are discussed The existence of this ‘inert’ area has not been recognised in the earlier literature. Its agricultural policy implications have been ignored by policy-makers, many of whom also fail to take account of other economic considerations discussed in this paper.