Apex Model Simulation of Hybrid and Inbred Corn Nitrogen Fertilization Needs and Fate.

Corn (Zea mays L.) inbred lines used to produce hybrid seed differ from hybrid corn plants. They have lower grain yield potential, primarily due to the smaller plant size, that includes smaller leaf area, and fewer kernels per plant. Successful hybrid seed production depends on the timing and optimization of key field operations and inputs, including; obtaining the correct ratio of female to male rows to maximize yields; optimizing the timing and duration of pollination period to maximize seed set. To ensure seed of the highest quality and purity, tassels of the female inbred lines are removed (detasseling) prior to silk emergence and pollen shed to prevent self-pollination. Usually detasseling is done mechanically, an operation that also results in the removal of several leaves, which results in a proportional linear decline in grain and stover yields. Furthermore, male inbreds are destroyed following pollination. In an effort to maximize target seed yields, producers often use fertilizer recommendations equal or in excess for hybrid corn production. Not only are these practices costly, they can harm the environment. The production of seed corn for planting is significant. Of the more than 90-million acres of corn grown in the USA, about 10 percent is dedicated to production of seed for planting. Our objectives were twofold: 1) adapt and demonstrate the capability of the EPIC/APEX model to simulate hybrid seed-corn production systems; and 2) comparably assess the N fertilization needs and fate of inbred/seed-corn production to those of commercial hybrid corn production. Preliminary results have showed that the EPIC/APEX model is capable of estimating inbred/seed-corn and hybrid corn grain yield and soil nitrogen balances under different production scenarios.