Organic Fruit Farming
Introduction
Organic farming offers the potential to reduce the emissions of agricultural greenhouse gases (carbon dioxide, nitrous oxide and methane) and their annual external costs, Organic farming additionally offers the highly significant potential to counter climate change through the development of the soil as a major carbon sink.
Carbon dioxide - numerous studies have shown that CO2 emissions from organic farming are 40-60% lower per hectare than conventional systems. This is mainly because organic farmers do not use inorganic N fertilisers.
Soil carbon bank – Soil contains about twice as much carbon as the atmosphere. The use of inorganic fertilisers and higher production levels in agriculture may have caused a large loss in organic matter.organic farming involves maintaining and increasing soil organic matter levels through various means. It has been estimated that if soils are developed as a CO2 bank, they could absorb 15 years worth of emissions from fossil fuels (Rattan Lal, Ohio State University).
Nitrous oxide and methane – Agriculture produces half the emissions of nitrous oxide. It is mainly emitted from manures and soils; methane is emitted by ruminant animals. There is little quantitative data on the production of these gases by organic farming. Organic farms may emit less per hectare because the livestock densities are lower (c.25% less) and inorganic N fertilisers are not used. However, methane emissions may be higher per unit of output, because more animals are needed for the same yield and emissions are thought to be increased by a forage-based diet (grass, silage or hay) rather than a grain based diet.
Air Quality
Air contamination from agriculture is mainly from pesticide sprays and ammonia volatisation (NH3). Organic farming should address both of these:
Pesticide sprays - synthetic pesticides sprays are not used.
Ammonia - Agriculture accounts for about 80% of UK ammonia emissions, which causes nutrient enrichment and acidification of soils. Emissions should be lower because of the non-use of N fertilisers and because manure from organic farms often has a lower concentration of nitrogen. Composting can release relatively high levels depending on its composition, but it reduces the amount released when manures are spread. Straw bedding minimises odour. Organic farms do not involve high concentrations of animals in a small space and there must be sufficient land to spread manure (170kgN/ha is the maximum allowed). Local odours should therefore be much less of a problem.
Water Resources
The higher soil organic matter that results from organic farming increases water retention and reduces run-off, reducing the need for irrigation. Anecdotal evidence supports the significance of the effect (farmers report a reduced risk of drought).
Nutrient leaching - Inorganic N fertiliser, used for plant nutrition in conventional systems is the most mobile form of nitrogen: thus in conventional systems about 20% of the nitrogen applied is lost. In organic systems inorganic N and P fertiliser are prohibited and nutrient inputs are through organic matter, where two-thirds of the N is in an organic form which is chemically more stable. The biological life in the soil, bacteria and fungi, feed on the organic matter and fix nutrients from the air, and it is they which mainly provide the nutrients to the plants. Bacteria and fungi are the least leachable form of N. Leaching is also reduced by the fact that organic systems are more extensive (stocking densities for all livestock are restricted to 170kgN/ha, which means that densities are c.25% less and all organic farmers must have adequate manure storage capacity. Many practices in organic systems increase the organic content of the soil, including humus levels, which means that water retention is increased and leaching and run-off reduced. This is supported by research: in all published calculations in Europe, the N,P,K surpluses of organic farms were significantly lower than conventional farms.
Pesticide contamination – organic farming eliminates the risk of ground and surface water pollution from synthetic pesticides. This is of importance for drinking water and also fisheries (eg. for eliminating Persistent Organic Pollutants and endocrine disrupting chemicals), as well as for reducing the major cost of water clean up.
Sediment run-off and bacterial leaching– as organic farming increases the level of soil organic matter, sediment run-off and bacterial leaching should both reduce.
Flood defence
Organic farming offers a major strategic opportunity for avoiding and reduce future flood damage in agricultural areas: very important for adapting to climate change:
Reducing the risk of flooding – the higher levels of organic matter in soils on organic farms, mean better water retention and drainage, and thus extremes of run-off and flooding are reduced. Anecdotal evidence indicates the effect is significant.
Organic Fruit farming Farms | South Africa
Organic Farming Association | South Africa