The success of a plant tissue analysis program depends on the calibration relating growth and nutrient concentration in specified plant tissues for each essential element. The minimal nutrient concentrations in tissues associated with maximum growth have been determined from calibration curves that were drawn free‐hand to best fit the respective X and Y values in graphical plotting. Statistical models to establish critical deficiency levels related to 90% maximum growth are desirable to reduce the arbitrariness of the graphical procedure. A modified Mitscherlich response equation was used to quantify critical deficiency levels by characterizing plant growth as a function of tissue nutrient concentration. The model presented is y = β(1 — γe‐ax) where y is the plant yield at tissue concentration x, and α, β, and γ are parameters to be estimated. Critical deficiency levels determined from the Mitscherlich model were significantly greater (P < 0.05) than the previously reported nutrient values of the same studies utilizing the graphical procedure.

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The effect of four drip inigation rates 0, 22.7, 45.4, and 68.1 L/hr/tree (LHT) on several quality parameters of 'Stuart' pecans were investigated along with values calculated from inshell weights, volumes, and kernel weights. Irrigation significantly increased kernel yield/tree, nut weight, diameter, kernel specific gravity, fill of nut, oil content, and appearance rating. Values calculated by computer analyses from weights and volumes were useful for evaluating the quality of nuts from the different irrigation treatments. This technique should be useful for researchers engaged in quality evaluations of inshell pecans. Nut size and % fill, and kernel color are the best parameters to estimate quality and value of pecans before actual shelling and processing. Additionally processing costs are partially dependent on nut size (no./kg) and kernel yield.

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Comparison of two nonlinear models for describing intake-response relationships in higher organisms is presented. The first model is based on the assumption that growth processes obey saturation kinetics phenomena while the second model is based on the assumption that the absolute size of the body is the factor which determines the rate of the growth process. Comparison of the two models is illustrated by considering a typical experiment for the evaluation of intake-response relationships.