As a result of excessive fertilizer use in agriculture and inadequate sewerage disposal, free nitrogen and phosphorus has triggered massive blooms of algae in the freshwater and marine environments. The millennium assessment found that excessive nutrient loading is one of the potential “tipping points” that can suddenly destroy entire ecosystems. So how do we clean up our act when applying fertilizer?
What is Fertilizer?
All fertilizers are made up of chemical nutrients. Nutrition of plants, animals and humans is chemistry in action. Their qualities and actions are however determined by their origin and level of treatment.
Although some are obtained from natural mineral deposits their chemistry is altered through chemical treatment to make unavailable plant nutrients accessible to plants e.g. superphosphate. Others are waste products of the chemical and mining industry, and the nutrients are often bound to a carrier salt to make them water soluble. High concentrations of nutrients are supplied to plants though osmotic solution in water. Plants show quick growth response, but fertilizer needs to be re-applied frequently. Most feed one to three nutrients only, with the exception of some speciality mixes. As nutrients are water soluble they are easily leached, especially from sandy soils. With long term use or overuse, soils degrade and soil life declines.
Fertilizers obtained from natural sources supply a buffet of plant nutrients (NPK & trace nutrients) to replenish nutrients in soil. IFOAM (International Federation of Organic Agriculture Movements) sets worldwide standards for certified organic growing to prevent soil and water pollution so inputs may not harm eco-systems. They are the first choice for the environmentally conscious, as soil health is promoted. Sustained release of nutrients ensures longer feeding, no burning and stronger plants less prone to pests and disease. Others are from natural mineral deposits. Natural nutrients are released by the decomposition action of microbial soil life and plant exudes, and are therefore not rapidly lost through leaching.
Compost and Manure to improve soil fertility
Although often marketed as organic fertilizers, compost and manures seldom contain nutrient levels sufficient to stimulate vigorous plant growth in South Africa’s low nutrient soils. They are from natural lifecycles, like waste from plants and animals. These are built on a carbon structure, and would not have been radically altered from their natural state. For example they might have been composted, sterilized, milled or pelleted for ease of application. The value of compost is that it improves water retention and soil structure, adds carbon which is the building block of all living things, supplies humic acids to stimulate healthy plant growth and it is food for microbes. Only composted manures sourced from well run farms and healthy animals should be added in limited quantities to condition soil. Effective composting sanitises harmful pathogens, stabilises nitrogen, denatures weed seeds and leaches excess salts.
The state of the world assessment at the start of the new millennium found that two thirds of the delicately balanced ecosystems studied have suffered badly at the hands of man over the past 50 years. Some 15 of the 24 ecosystems vital for life on Earth have been seriously degraded or used unsustainably. Significant problems such as climate change causing disrupted weather patterns, excessive nutrient loading in freshwater systems in dams and rivers, extinctions in animal and plant species, are clear and visible symptoms of this. These factors are impacting on the profitability and sustainability of farming. The WWF in South Africa produced a sustainable farming policy guide for commercial farmers to adapt as their contribution to rescue degradation in “The Green Choice Living Farms Reference 2009/2010”.
Synthetically Enriched Organic Fertilizers
An organic base, usually chicken manure, is enriched with synthetic fertilizer to boost major nutrient levels. This buffers and preserves extensively farmed soils by adding carbon and compost to an extent. Plants, leaves and roots can burn if incorrectly applied.
Another quotation from ‘The Secret life of Compost’ sums it up as follows: “The study of history and civilization shows that those who took care of the soil survived, while those who mistreated the soil didn’t”.