Diagnostic sol pour la determination des formules d'engrais minéraux pour les caféiers
Clasification: The evaluation of mineral content of the soil is based on the works of J. Forestier. The classification given by the computer is based on the following scale, which is a function of the soil content in fine elements (clay + silt in per cent) : - : very poor, + : fair, ++ : high, +++ : very high. The ratios between exchangeable bases give the requirements in potassium and/or magnesium. Fertilizer formulae: If the base saturation is greater than 40 per cent and if the Cation Exchange Capacity (CEC) is greater than 5 meq per cent and if there is no important unbalance between elements, only nitrogen is added to the soil. Nitrogen and phosphorus are advised for coffee trees aged ten years or more, if the soil is poor in total phosphorus or in available phosphorus. When the potassium level is very low, nitrogen and potassium are advised. The type of phosphate fertilizer depends on the pH of the soil: natural or rock phosphate, if the pH is lower than 5.5; single or triple superphosphate if the pH is higher than 5.5. In other cases, on leached soils or on soils low exchange capacity, complete fertilizers are added N-P-K- or N-P-K-Mg, in which K predominates. The basic formula is 12 - 6 - 20, modified according to the phosphorus content of the soil, and also according to the K and Mg levels and the ratios between K, Ca and Mg. Doses: The doses were determined through field experiments. They do not depend on soil analyses. For nitrogen alone: 120 unities/ha, are advised; for nitrogen + phosphorus: 120 N/ha and 60 P2O5/ha; for nitrogen + potassium: 120 N/ha and 120 K2O/ha; for complete fertilizers (e.g. 12 - 6 - 20): 1000 Kg/ha
| Main Authors: | , , , |
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| Format: | biblioteca |
| Published: |
París (Francia)
1988
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| Subjects: | ANALISIS DEL SUELO, CLASIFICACION DE SUELOS, DISPONIBILIDAD DE NUTRIENTES, FERTILIZANTES, FORMULACIONES, DOSIS DE APLICACION, |
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