In recent years, numerous attempts have been made to simulate soil transformations
of N and P and the effects of soil and fertilizer N and P on nutrient
uptake by the plant, crop growth, and water pollution. In order to produce
reasonable estimates of the effects of crops on soil nutrient transformations,
soil erosion, and water quality, simulation models must produce reasonable
estimates of crop nutrient content and the distribution of nutrients in the
crop. The purpose of this review is to determine: (1) the variability of tissue
N and P concentrations of several major fractions of maize (Zea mays L.) and
grain sorghum (Sorghum bicolor (L.) Moench) plants; and (2) the optimum
tissue N and P concentrations at different stages of growth. This information
can be used to evaluate the estimates of crop nutrient composition produced
by crop growth simulation models.