About 90 elements are found in normal plant tissue, and only 16 or so elements are truly established as essential elements for plant growth. All 16 essential plant nutrients are naturally sourced from soil and microorganisms. There are not always enough of these nutrients in the soil for healthy plant growth; therefore, it is necessary to use fertilizers to add the nutrients to the soil to achieve desired quality plant yield. Since chemical fertilizers were first used commercially on a large scale, there have been claims that the use of agricultural chemicals produce less wholesome and less nutritious food crops. The organic farming movement began in part as a result of the belief that food grown using more traditional, chemical-free methods was more wholesome. Food grown by these methods came to be known as organic. Conventional farming systems allow the use of many synthetic chemical fertilizers, fungicides, insecticides, herbicides, and growth regulators, while organic farming must be carried out in accordance with relevant certification standards
For New Zealand organic kiwifruit growers, BIO-GRO New Zealand is an organic certifying organization that has strict input restrictions, and therefore organic growers must rely on the application of organic matter and slow-release soil nutrients (BIO-GRO NZ 2001; Worthington 2001); other soil additives; natural products such as bone or blood meal; and the management practices, such as crop rotation, tillage, and mulching, for nutrient balancing and to overcome pest and weed problems. Management practices may alter soil quality based on soil physicochemical and hydrological properties. Soil characteristics influence basic soil functions, such as moderating and partitioning water and solute movement and their redistribution and supply to plants; storing and cycling nutrients; filtering, buffering, immobilizing, and detoxifying organic and inorganic materials; promoting root growth; and providing resistance to erosion.
Read the full publication here: Impact of Management Systems on Soil Properties and Their Relationships to Kiwifruit Quality (PDF, 324kb)