Quantifying maize pollen movement in a maize canopy

An accurate assessment of the amount of pollen released in a cornfield that reaches the female flowers (silks) is important for determining both the amount and purity of seeds produced. A method for making this assessment is presented. In this method, the movement of maize pollen in and above a crop canopy is evaluated using a combination of measurements and modeling. In particular, concentrations, C (grains m(-3)), and downward vertical fluxes, F-V (grains m(-2) s(-1)) of pollen were measured at several heights inside and above a flowering maize canopy, and a Lagrangian stochastic (LS) simulation model was used to calculate concentrations and fluxes of pollen at these locations. Model estimates for the average release rate of pollen grains per area of crop, Q (grains m(-2) s(-1)) were deduced by comparing measured and modeled values of C. Using these determinations of Q, the model predicted well (r(2) = 0.73) the measured pollen fluxes in the canopy. On average, about 20% of the pollen released by the tassels reached the height of the silks in the canopy. Fluxes of pollen at silk height were highly variable, however. This variability was mainly due to the faster wind speeds and higher levels of turbulence in the upper canopy, which led to greater amounts of rebound and re-entrainment of pollen grains from leaves. The results of this study underscore the importance of rebound and re-entrainment processes in the amount of maize pollen reaching the silks. (c) 2005 Elsevier B.V. All rights reserved.