AGP - Sustainable Agricultural Practices

The development of sustainable agricultural practices depends largely on promoting long term fertility and productivity of soil at economically viable levels through, for example:

  1. Matching the supply of soil nutrients with nutrient demands of crop, fodder and pasture plants: through optimising return of crop residues and animal wastes to the land and through greater reliance on biologically fixed and recycled nutrients instead of fertiliser inputs;
  2. Maintaining acceptable pest tolerance levels: through reliance on crop rotations and biocontrol agents and hence reducing or maintaining low pesticide use;
  3. Maintaining soil physical properties conducive to plant growth and to soil ecosystem functioning (aeration, water infiltration and retention, nutrient availability, etc.) through decreasing or maintaining low frequency and intensity of tillage and reducing erosion and leaching.

Farming can be considered essentially as an ecological activity in which natural ecosystems open to influences of climate, substrate and wild biota are modified to increase yields of desired food and fiber products. The greater the change to natural ecosystem the greater the human effort to maintain the agricultural system. It has been shown that conventional agriculture results in greater ecological disturbance and may be less sustainable compared to low external input agricultural (LEIA) systems. LEIA systems have high genetic and cultural diversity, multiple use of resources and efficient nutrient and mineral recycling (Altieri 1999) The search for biological alternatives to improve and maintain yields is a high priority. In order to find alternatives for different environments and agricultural systems we need to understand the effect of different practices on soil organisms, their functions and processes and their influence on plant nutrition and soil stability.

Understanding how agricultural management practices contribute to sustained fertility and productivity of arable soils requires a knowledge of below ground food webs. Trials have helped to illustrate effects of tillage on structure and function of such food webs and identify key mechanisms by which fungal and bacterial based food webs regulate soil processes. It is an important area for further research. Where cultivation is minimised and crop residues retained on the soil surface it has been shown that there is much greater spatial and temporal differentiation of belowground food webs and processes compared to conventional cultivated soils. In conventional tillage bacteria based food webs play a greater role especially in the tilled layer, and as result of flushes of mineralisation related to tillage events may lead to greater organic matter loss and lower nutrient retention. In no tillage systems fungal based food webs are more important which influence nutrient availability and soil aggregate stability, tending to increase N retention and reduce leaching.

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