The main goal of agriculture - to guarantee food security and quality for an increasing world population - has to be attained in the current context of environmental constraints, namely: global climate change, water pollution and scarcity, soil pollution and degradation, loss of biodiversity. The sole economically viable, environmentally safe and socially acceptable way over the long term is considered to be newly developed sustainable agricultural systems. The agriculture sustainability is of tremendous importance for the mankind future, but the performances of this sustainable agriculture are even more important for satisfying the needs of "our daily bread" for present and following generations.
The technological aspects of sustainable agriculture imply the preservation of natural resources, especially the soil fertility - the main support of human civilization and wellbeing.
The world agriculture is practiced on only 6.4 percent of the 29 percent represented by the entire terrestrial surface. We have to emphasize here that the dominant part of all the agricultural land is represented by the soils with low and very low fertility (60 percent); the soils with moderate fertility attain 29 percent and only 11 percent of the soils are favored of high fertility.
If we refer to Romania, a country with a total surface of 23.8 million hectares, from which 14.85 million hectares are represented by agricultural land (9.4 million hectares arable land) and 6.6 million hectares are occupied by forests and forestry vegetation, the agricultural land productivity is influenced by a very large diversity of pedoclimatic conditions and the agricultural systems applied during the time. Currently, 2.8 percent of agricultural land is included in 1st class of suitability, 24.6 percent of it belongs the IInd class of suitability with few restrictions, 20.7 percent are the agricultural lands of the IIIrd class of suitability with moderate restrictions and the rest of agricultural land (51.9 percent) is included in the IVth and the Vth class of suitability with high and very high restrictions.
The most important indicator of soil productivity - the humus content is low and very low (< 2 percent) on about 5 million hectares (50.6 percent of agrochemically characterized surface) and moderate to high on about 3.9 million hectares. The availability of the main plant nutrients (N, P, K) is under the levels needed for obtaining high and stable crop yields. The soil pH values impose the use of amendments on about 2.26 million hectares characterized by medium to strong acidity. Even if we like to consider Romanian soils among the most fertile in Europe, the reality is asking for drastic changes in our conceptions and measures.
The maintenance and possible increase of soil fertility to sustain enhanced crop productivity and to counteract the soil nutrients depletion can be achieved by conceiving integrated plant nutrition systems implying the optimal use of all sources of plant nutrients adjusted to site characteristics and to the locally available resources.
Though the rational use in recommended quantities and balanced proportions of chemical fertilizers is recognized to be a quick and sure way of boosting crop production, a more sustainable solution is the combination with non-mineral nutrients as plant residues, farm manure, urban wastes, other organic matter sources and biological nitrogen fixation. The organic sources, beyond the nutritional aspects, contribute to the improvement of physico-chemical soil properties, closer to the nutrient cycles and to a better efficiency of fertilizer use.
The biological nitrogen fixation is, for the time being only a supplementary source, but its utilization could be significantly increased by developing specific cropping systems, more intense legume cultivations, use of leguminous plants as cover crops during non-crop seasons or as green fertilizers, or the transfer of the biological nitrogen fixation capacity in non-leguminous plants (cereals).
So, based on our gained experience and results, we are convinced about the necessity and beneficial role of fertilizers in food production, but, at the same time we are aware of our great responsibility to avoid the risks implied by excessive or inappropriate use of fertilizers. In developing the conscience of the error risk a multidisciplinary scientific co-operation with a more pronounced involvement of ecology, other life sciences and ethics is required.
Further research is needed for producing new fertilizer types with lower production costs, higher utilization efficiency and environmental friendly and new application methods are of high priority.
Being deeply concerned about global limitations, we have to find better ways to preserve and enrich the natural resources involved in agricultural production by using more advanced technologies, by establishing optimal forms, amounts, harmonized nutrient proportions, timing, multiple applications, tailored to crop requirements and expected yields, location history and soil and climate peculiarities corresponding to each zone and microzone. The refined modalities of fertilizers use will follow to enhance crop uptake and minimize losses. Computer simulation models can be developed aiming to integrate and synthesize complex soil-crop-environment factors, extrapolate beyond the bounds of experimental data from long term field experiments, allowing users to apply the predictive capability to control outcomes, reducing much of repetitive, laborious, time-consuming and expensive experimentation.
Being highly interested in the fulfillment of our assumed tasks, great attention has to be paid to developing and perfecting agrochemical services and improving advisory services for putting our research results to practical use by every farmer.
References
- Hera C., Schnug E., Dumitru M., Dorneanu A., 2001 - Role of fertilisers in sustainable agriculture (AGRIS Publishing House, Bucharest).
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- Hera C., 2002 - Soil fertility, a decisive chain for sustainable and performing agriculture (Tartakiserletek, Tajtermesztes, Videkfejleszets, Debrecen, Hungary).
- Ji L., Chen G., Schnug E., Hera C., Haneklaus S., 2003 - Fertilization in the Third Millenium (Liaoning Science and Technology Publishing House, Shengyang, China).
- Hera C., Schnug E., Ersahin S., Gunal H., 2003 - Fertilizers in context with resource management in agriculture (Gaziosmanpasa University Press, Tokat, Tukey).
