they increase the efficiency of the land too. By doing perfect spacing between plants they ensure optimal growing conditions for each which in turns increase yields greatly. Two plants in the space of one shade each other and the net result is a lot more than half the harvest is lost since each needs to put the same amount of energy into making a plant before they can put any into creating the crop. Too far apart and sunlight reaches the ground uselessly (or worse a fast growing weed that will shade your plants!).