Substitution of labour and energy in agriculture and options for growth

Viewed from the technical angle, labour and energy may be considered the basic resources for production. Methods to compute the requirement of energy and labour for the production processes from raw material to the product at the farm gate are discussed. It is shown that limited amounts of added energy and labour are required to achieve the maximum possible production per hectare. The form of the functions that relate the requirement for these resources with the level of production is considered in two limiting situations. These concern the minimum amount of added labour that is required when energy is abundantly available and the minimum amount of added energy that is required when labour is abundantly available. By means of these functions and the added energy and added labour used in the actual farm situation, iso-yield functions are constructed. These functions identify the possibilities for substitution of energy and labour during the production process at various yield levels. The shape of the expansion paths indicate that there may be a considerable range of production situations where the yield per unit of added energy, the yield per unit of added labour and the yield per unit of surface increase with increasing use of added labour and energy per hectare, whereas the added energy use per unit of added labour decreases at the same time. Some resulting options for growth, with special reference to the situation in the Netherlands, are discussed

Competitive interference of plant species in monocultures and mixed stands

A dynamic model is presented for calculating the dry matter yields of individual plant species in a mixed stand by means of parameters derived from a spacing experiment with species grown at 2 densities and harvested at regular intervals. Results are given of trials with different crops, including tall and dwarf peas. The model is intended for use under conditions of near-optimum supply of water and nutrients, where the principal competition is for light. A simple method for measuring relative light interception by species in mixed stands is also described