Environmental impacts of organic farming - Organic Agriculture: A Global Perspective - page 271

cessfully suppress weeds, to fix nitrogen and prevent erosion (Alföldi et al . 2002). Parrott and
Marsden (2002) report that the shift to biodynamic methods in the Ambootia Tea Estate (Dar-
jeeling, India) has significantly reduced problems of soil erosion and risk of landslide, and
increased retention of soil moisture in an area with very seasonal rainfall.
Desertification
Since organic farming techniques have the potential to improve soil fertility, soil structure and
moisture retention capacity, organic management provides solutions to the problems associ-
ated with desertification (degradation of drylands). Relevant techniques in this context include
composting, mulching, use of cover crops, intercropping, the use of supplemental organic fer-
tilisers and mineral fertilisers (e.g. rock powder, rock phosphate, potassium sulfate). Addi-
tional benefits are provided by the frequent use of endemic species which are more adapted to
climate stress, as well as the use of water preserving and agroforestry techniques (Djigma et al .
1990, Harris et al . 1998). With a high level of organic matter and permanent soil cover, the
water and nutrient retention capacity is increased and microorganisms create a stable soil
structure. Organically managed soils, therefore, tend to be more resilient to water stress and to
nutrient loss. The high moisture retention capacity can substantially reduce the amount of
water needed for irrigation (Alföldi et al . 2002).
The organic farming's potential for countering desertification is demonstrated by some
practical examples in arid areas. In Kenya, the International Centre for Research in Agrofor-
estry (ICRAF) runs organic farming projects to fight drought (Stolton 1997). Agroforestry
systems generate multiple benefits, including erosion control and moisture retention (Alföldi
et al . 2002). The organic farm Fazenda Tamanduà in Brazil is situated in an arid area severely
affected by salinisation resulting from inappropriate irrigation techniques. It is a certified
organic farm with more than 3000 ha of which 650 ha are cropped with mango trees. Conven-
tional agriculture in the area uses the water from the rivers and causes further salinisation by
overirrigation. By using only rainwater, the Fazenda Tamanduà avoids the depletion of water
resources and reduces soil salinisation considerably. Fertilisation regimes include grazing
cattle under mango trees as well as application of composted manure (Alföldi et al . 2002).
According to Harris et al . (1998) organic farming offers a favourable option in arid areas,
but has to face constraints such as a lack of knowledge, lack of organic materials, land-holding
constraints and the perception of organic farming as being old fashioned. The examples above
have shown the potential benefits of organic farming for countries hit by desertification.
Organic management could be a key to bringing degraded land back into production and
therefore significantly contribute to the solutions of the world food problem. Governments
would need, however, to actively promote organic farming systems and land reform (Alföldi et
al . 2002).
Ground and surface water
The harmful effects of intensive agriculture on ground and surface water are caused mainly by
the following practices (Stolze et al . 2000, Alföldi et al . 2002):
• excessive application of mineral N fertilisers, nutrient surpluses and a high level of
available nitrogen after harvest;
• high organic fertilisation level in combination with high stocking rates;
• contamination of water with synthetic pesticides; and
• lack of a protective soil cover, a narrow crop rotation and frequent tillage.