BASIC PRINCIPLES OF AGROECOLOGY AND SUSTAINABLE AGRICULTURE

In the final analysis, sustainable agriculture must derive from applie d ecology, especially the principle of the regulation of the abundance and distribution of species (and, secondarily, their activities) in s pace and time. Interspecific competition in natural ecosystems has its counterparts in agriculture, designed to divert greater amounts of en ergy, nutrients, and water into crops. Whereas natural ecosystems sele ct for a diversity of species in communities, recent agriculture has m inimized diversity in favour of vulnerable monocultures. Such systems show intrinsically less stability and resilience to perturbations. Som e kinds of crop rotation resemble ecological succession in that one cr op prepares the land for successive crop production. Such rotations en hance soil organic processes such as decomposition and material cyclin g, build a nutrient capital to sustain later crop growth, and reduce t he intensity of pest build-up. Species in natural communities occur at discrete points along the r-K continuum of reproductive maturity. Cle aring forested land for agriculture, rotational burning practices, and replacing perennial grassland communities by cereal monocultures move s the agricultural community towards the r extreme. Plant breeders sel ect for varieties which yield at an earlier age and lower plant biomas s, effectively moving a variety towards the r type. Features of more n atural landscapes, such as hedgerows, may act as physical and biologic al adjuncts to agricultural production. They should exist as networks in agricultural lands to be most effective. Soil is of major importanc e in agroecosystems, and maintaining, deliberately, its vitality and r esilience to agricultural perturbation is the very basis of sustainabl e land use.