SOIL AND PLANT ANALYSES FOR LIME AND FERTILIZER RECOMMENDATIONS IN BRAZIL

The fertilizer recommendation guidelines for over 160 crops for the St ate of Sao Paulo, Brazil were updated in 1996 based on recent results of research on soil and plant analysis, and crop responses. Recommenda tions are based mainly on soil analysis and expected yield. Limestone rates are calculated to raise soil base saturation as a percentage of the cation exchange capacity (CEC) of the soil at pH 7.0, to levels wh ich vary with crop species (i.e., to 50% for rice, coffee, and cassava , 60% for sugar cane and soybeans, 70% for cotton and maize, and 80% f or grapes and onions). In addition, exchangeable magnesium (Mg) conten ts must reach a minimum level. Exchangeable subsoil aluminum (Al) and calcium (Ca), and clay content are used to determine rates of gypsum a s amendment of subsoil acidity. Fairly consistent data on soil phospho rus (P) and potassium (K) calibration are available for Brazilian soil s. Potassium rates are recommended based on values of soil exchangeabl e K and, for P fertilization, ion exchange resin-extractable P is used . For the later the ranges of interpretation of soil analysis are diff erent for horticultural, annual, perennial, and forestry crops. No soi l test is used for nitrogen (N) advisory purposes. For many crops, esp ecially grains, N rates depend on the class of expected response to th is element, defined as a function of previous management history, crop rotation, texture etc. For some perennial crops N fertilizer rates ta ke into account leaf N contents which were shown to correlate well wit h N response for citrus, mango, and coffee. Soil analysis for micronut rients, extracted with hot water [boron (B)] or DTPA-TEA [iron (Fe), c opper (Cu), manganese (Mn), and zinc (Zn)] is also used as criterion f or fertilizer recommendation although for most crops only B and/or Zn are required.