Notes - Agri-culture: Reconnecting People, Land and Nature - page 205

11 For a discussion on the value of ecosystem services in the soil, and the
problems of agricultural intensification, see Daily et al, 1997. See also Cleaver
and Schreiber, 1995; RCEP, 1996; World Bank/FAO, 1996; Hinchcliffe et al,
1999; Petersen et al, 2000; FiBL, 2000. For a summary of issues relating to
sustainable management of land and soils, see FAO (1999) The Future of Our Land.
12 In Argentina, the amount of organic matter in soils fell over a century
to 1990 from 5.5 per cent to 2.25 per cent; where no till systems are being used,
it is increasing by 0.1 per cent per year (Roberto Peiretti, personal commun-
ication).
13 For a summary of the extent of soil degradation and its effects, see
Koohafkan and Stewart, 2001; Smaling et al, 1997; Henao and Baanante, 1999.
14 See Reicosky, 1997; Sanchez et al, 1997; Sorrenson et al, 1998; de Freitas,
2000; Bunch, 2000. Some plants are called phosphate releasing, not because they
release phosphate but because acids secreted from roots solubilize iron and
aluminium phosphates in the soil. See Sanchez and Jama, 2000.
15 For effects of zero-tillage in Latin America, see Sorrenson et al, 1998;
Petersen, 1999; de Freitas, 2000; Peiretti, 2000; Landers, 1999.
16 See Landers et al (2001) 'Environmental Benefits of Zero-Tillage in
Brazil'.
17 Using 20 species of cover crops and green manures, Paolo Petersen and
colleagues at AS-PTA have shown how small farmers can adopt zero-tillage
systems without herbicides. See Petersen et al, 2000; von der Weid, 2000.
18 For details of the work of Rodale in Senegal, see Diop, 2000.
19 See Hamilton, 1998; Association for Better Husbandry, 2001.
20 One of the best examples of how changed rotations can transform whole
agricultural systems comes from western Kenya, where farmers are using
improved fallows using sesbania ( Sesbania sesban ), tephrosia ( Tephrosia vogelii ) and
various species of Crotalaria. These are interplanted during the main rainy season
maize crop, and capture 100-200 kilogrammes of nitrogen per hectare per year,
with the added benefit of no transport costs and associated benefits for fuelwood
production. Pedro Sanchez indicates that 'many farmers say hunger is now a thing of
the past' . See Sanchez et al, 1999; Sanchez and Jama, 2000.
21 Reij, 1996.
22 See Uphoff, 1999, 2000.
23 See BAA Annual Report , 2000. The eight companies in 2001 that control
90 per cent of the world pesticide market are Aventis, Syngenta, Monsanto, Du
Pont, Bayer, Cyanamid, Dow and BASF. Data on the weight of pesticides used
in agriculture are very difficult to access, not least because of the great differences
in toxicity of active ingredients, with some products being high volume and low
toxicity, and others low volume and high toxicity. According to the World Health
Organization, some 3.1 billion kilogrammes were exported in 1985 at a value
of US$16 billion. Since today's market is estimated to be in excess of US$31
billion, the total pesticides applied are likely to exceed 5 billion kilogrammes.
24 For more on farmer field schools in Asia, see Evelleens et al, 1996; Heong
et al, 1999; Desilles, 1999; Jones, 1999.