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Compositional Nutrient Diagnosis technique involves a yield target for discriminating between high- and low-yield subpopulations when developing norms. Traditionally, this yield value is estimated by finding the inflection point of the cumulative variance ratio function versus yield relationship through a third-order equation. However, yield targets frequently lie outside of the experimental yield range. A comparison among traditional (unrestricted) and restricted cubic model, and restricted and unrestricted Boltzmann equations was performed using a database (n = 360) of fresh matter yield and nutrient concentrations in one–year old cladodes ofOpuntia ficus-indicaL. The unrestricted Boltzmann equation resulted to have the best goodness-of-fit. The yield target was 27.01 kg plant−1associated to the unrestricted Boltzmann equation for phosphorus cumulative variance ratio function versus yield relationship. Proposed nutrient optimum concentrations are: 11.4 g kg−1for nitrogen (N), 3.4 g kg−1for phosphorus (P), 42.3 g kg−1for potassium (K), 42.5 g kg−1for calcium (Ca), and 16.2 g kg−1for magnesium (Mg). [ABSTRACT FROM AUTHOR]

Preliminary compositional nutrient diagnosis (CND) norms for maize ( Zea mays L.) were developed from a small database as means and standard deviations of row-centered log ratios V X of five nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] and a filling value R, which comprised all nutrients not chemically analyzed and quantified in 72 leaves of hybrid ‘Pioneer 3044.’ Norms were derived from maize grain yields higher than 7.7 t ha -1 . Principal-component analysis performed using CND nutrient indexes allowed us to identify an antagonism between N and Mg explained by the calcareous nature of the soil and the relevant N fertilization with ammonium (NH 4 + ), and a positive interaction between P and K, and P-Ca and K-Ca antagonisms. Maize plants tended to take up lower amounts of N and K and higher amount of Mg in our calcareous soil than the concentrations of these nutrients reported to be optimum. [ABSTRACT FROM AUTHOR]