Asymptotic and Parabolic Yield and Linear Nutrient Content Responses to Rice Population Density 1

Knowledge of optimum rice ( Oryza saliva L.) population densities and the response of rice nutrient status to population density is necessary for rice producers and researchers to achieve maximum productivity. The objectives of this study were to determine (i) the responses of rice yield to population, (ii) critical populations for experiments with asymptotic yield responses to population, (iii) optimum populations for experiments with parabolic yield responses to population, and (iv) Y‐leaf (youngest mature rice leaf of a plant) nutrient content responses to population. Seeding rates were used to obtain broad ranges of populations over 2 yr for three rice cultivars at three Arkansas locations. Asymptotic and parabolic area yield equations were determined for area yield and population data. In 11 experiments, asymptotic yield responses to population were found; in five experiments, parabolic yield responses were found; in three experiments, linear responses were found; and in three experiments there was no significant relationship between yield and population. Critical and optimum populations were 87 to 308 plants m −2 , with most in the range of 159 to 270 plants m −2 . In some experiments, the effects of population on N, P, K, and Fe contents were negative. The effect of population was positive for Mn in six of 14 experiments. Reductions in yield at excessive populations appeared to be associated with population‐dependent stresses such as water deficits, disease, and nutrient deficiencies.