Soil and plant analyses for lime and fertilizer recommendations in Brazil

The fertilizer recommendation guidelines for over 160 crops for the State of Sao Paulo, Brazil were updated in 1996 based on recent results of research on soil and plant analysis, and crop responses. Recommendations 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 which 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% for grapes and onions). In addition, exchangeable magnesium (Mg) contents must reach a minimum level. Exchangeable subsoil aluminum (Al) and calcium (Ca), and clay content are used to determine rates of gypsum as amendment of subsoil acidity. Fairly consistent data on soil phosphorus (P) and potassium (K) calibration are available for Brazilian soils. Potassium rates are recommended based on values of soil exchangeable K and, for P fertilization, ion exchange resin-extractable P is used. For the later the ranges of interpretation of soil analysis are different for horticultural, annual, perennial, and forestry crops. No soil test is used for nitrogen (N) advisory purposes. For many crops, especially grains, N rates depend on the class of expected response to this element, defined as a function of previous management history, crop rotation, texture etc. For some perennial crops N fertilizer rates take into account leaf N contents which were shown to correlate well with N response for citrus, mango, and coffee. Soil analysis for micronutrients, extracted with hot water [boron (B)] or DTPA-TEA [iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn)] is also used as criterion for fertilizer recommendation although for most crops only B and/or Zn are required.