Book of Abstracts
11th IFOAM Scientific Conference
11-15 August 1996, Copenhagen, Denmark
Soil & Water Research Institute, Tehran, P. O. Box 14155-6185, Islamic Republic of Iran
For sustainable agriculture, the use of chemical fertilizers should be minimized. On the other hand, the use of organic fertilizers, which are vital for the improvement of the physical, chemical, and biological characteristics of the soils should be maximized. Unsuitable cropping as well as forgotten use of compost, animal, and green manures have caused lowering of soil organic carbon, increasing the bulk density, decreasing the root penetration, lowering of permeability and hardening of the arable soils.
Our farmers should realize the significance of a sustainable farming system, and continuously adapt the agricultural technology such as sequential cropping, biofertilizers and organic fertilizer application. In implementing sustainable agricultural program, the Iranian government strongly supports the production of Rhizobium, mycorrhiza, compost from very wide range of waste materials, and intensifying research on the development of other biofertilizers. The combined use of organic and inorganic fertilizers for crop production should be adapted by farmers.
Nitrogen fertilizers especially urea and ammonium nitrate, due to their higher solubility and susceptibility to leaching, should be used in split, otherwise underground waters will be polluted. At present, on irrigated farms, sulfur coated urea (SCU) is preferred. Granulated sulfur itself can be used on the calcareous soils through mixing with the thiobacillus bacteria. Ammonium sulfate is best suited for rice, sugar-cane, and tea cultivation, due to its available sulfate content. Because of its numerous advantages production of this fertilizer should be enhanced and its use encouraged. Although the need of plants for P, in comparison with N and K, is low (10-2-8), some farmers are extravagant in their use of ammonium phosphate. Over-use of P-fertilizer has deleterious effects on the uptake of Zn. All around the world, the ratio usage of N-P2O5-K2O is 100-50-40, but in Iran this ratio is imbalanced (100-80-5). In the case of increasing soil organic matters and K-fertilizers, the amount of applied P-fertilizers should be reduced up to 50%. Potassium deficiencies can be corrected with KCl due to its cheaper price particularly on: a) soils with low levels of chlorine, paddy soils and tea cultivations, b) irrigation water that contains less than 150 ppm chlorine, but potassium sulfate should only be used on potato, fruit trees, and on the saline soils with higher chlorine content.