Relationship between the chemical composition of corn leaves and yield responses from nitrogen and phosphorus fertilizer

Corn yield in relation to soil, management, and weather variables in western Iowa

“…Soil test values for N, P, and K in the surface or plow layer have affected corn yield and its response to applied fertilizers in Iowa (Voss and Pesek, 1967;Desselle, 1967;Turrent-Fernandez, 1968) and by many other researchers elsewhere. Henao (1976) The mathematical model commonly used for fitting data is the polynomial of degree n; the degree is usually n = 2 (the quadratic model)* but n = 1/2 (the square root model) is also common (Dumenil, 1958(Dumenil, » 1961Voss and Pesek, 1967;Laird and Cady, 1969;Pena-Olvera, 1973;Henao, 1976). These models when used to approximate multivariate data are called mul tiple linear regression models.…”

“…From data in Table 9, Also common are references to the positive responses of corn yield to P and K fertilizer applications and their nega tive interactions with soil P and K levels, respectively (Dumenil, 1958;Pesek, 1958, 1959;Olson et al, 1962;Hanway et al, 1962;Pierre et al, 1966;Christensen, 1968;Voss et al, 1970;Bohling, 1971). Table 12.…”

Influence of soil variability on optimum soil sampling and fertilizer use

“…A final note of thanks is given to the National Science Foundation for major financial support of the research. In the present study, 15 of the 93 experiments analyzed by Dumenil (1958) were discarded, due to unavailable soil test nitrogen results. In Dumenil's numbering system, these are Experiments 1,2,3,5,17,20,21,64,77,78,79,91,93,94,and 119 Squares and all possible interaction pairs of these independ ent variables were included in the polynomial model.…”

Concentrations of N, P, and K in the corn leaf as affected by weather indexes and selected soil and management factors

“…In reviewing the effect of sampling upon nutrient concentration in the com leaf, Dumenil (1958) concluded that leaf N tended to decrease with time during the time around tasseling and silking but the rate of de crease was affected by the available soil N. The K percentage usually decreased with time through this period but there were some exceptions.…”