Sustainable Agriculture

Sustainable agricultural systems employ natural processes to achieve acceptable levels of productivity and food quality while minimizing adverse environmental impacts (Harrier and Watson, 2004). Sustainable agriculture must, by definition, be ecologically sound, economically viable, and socially responsible. Similarly, sustainable forestry refers to an overall commitment to environmental conservation that integrates the production of trees for useful products with reforestation and conservation of soil, air, water quality, wildlife and aesthetics. Sustainable agriculture relies on long-term solutions using proactive rather than reactive measures at system levels.

Several soil fertility factors contribute to sustainable agriculture through control of soil-borne diseases, including increased soil microbial activity leading to increased competition and parasitism within the rhizosphere (Jawson et al., 1993; Knudsen et al., 1995). Research and development strategies are presently focused on the search for suitable alternatives to the use of commercial synthetic pesticides. Progress has also been made, however, in exploring the use of microorganisms to improve soil fertility. Greater emphasis is being placed on enhanced exploitation of indigenous soil microbes which contribute to soil fertility, increased plant growth and plant protection.

Mycorhizal fungi, particularly AM, are ubiquitous in soil and create symbiotic associations with most terrestrial plants including agricultural crops, cereals, vegetables, and horticultural plants. In agriculture, several factors such as host crop dependency to mycorrhizal colonization, tillage system, fertilizer application, and the potential of mycorrhizal fungi inocula, affect plant response and plant benefits from mycorrhizae. Interest in AM fungi propagation for sustainable agriculture is increasing due to its role in the promotion of plant health, and improvements in soil fertility and soil aggregate stability. These fungi can be utilized effectively for increasing yields while minimizing use of pesticides and inorganic fertilizers.

To improve crop production in infertile soils, chemical fertilizers have been intensively used, organic matter is incorporated and soil management technologies such as fallow or legume cultivation have also been used. Reliance should be on biological processes by adapting germplasm to advance soil conditions, enhance soil biological activity and optimise nutrient cycling to minimise external inputs and maximise the efficiency of their use (Sanchez, 1994). This approach has been developed for soil biota management using earthworms and microsymbionts (Woomer and Swift, 1994; Swift, 1998).

These soil organisms may represent more than 90% of soil biological activity and thus contribute to nutrient cycling, soil fertility and symbiotic processes in the rhizosphere. Soil fungal diversity and activity have not been adequately studied and understood (Hawksworth, 1991). Mycorrhizae represent an important group because they have a wide distribution, and may contribute significantly to microbial biomass and to soil nutrient cycling processes in plants (Harley and Smith, 1983). Mycorrhizal associations are beneficial to plants and thus crop productivity for sustainable agriculture (Gianinazzi-Pearson and Diem, 1982; Bethlenfalvay, 1992). They improve nutrient uptake, especially P, and also uptake of micronutrients such as zinc or copper; they stimulate the production of growth substances and may reduce stresses, diseases or pest attack (Sylvia and William, 1992; Davet, 1996; Smith and Read, 1997). For appropriate use of this technology, it is necessary to select the best inocula adapted to the specific limiting environmental factors for crop productivity.

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    4 years ago

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