Wildrice (Zizania palustris) Varietal Differences in Response to Slow-Releasing Nitrogen Fertilizer (Polymer-Coated Urea).

Wildrice cultivars in Minnesota have been developed through recurrent selection within several distinct heterogeneous populations. Different traits have been emphasized in different breeding populations, such as early maturity, high yield, short stature, and the pistillate (gynomonoecious) panicle type. Because wildrice is a tall crop—often exceeding 2 m in height, lodging can be a problem if too much nitrogen is applied pre-plant. Shorter-statured varieties and the availability of polymer-coated urea (PCU) provide different tools for addressing this problem. Is there a differing response of short and tall wildrice varieties to pre-plant applied PCU?  To answer this question, experiments were conducted on five varieties or breeding populations: two short-statured, two high-yielding tall, and one early-maturing tall. Pre-plant PCU rates were 0, 45, 90, and 135 kg ha^-1 on organic soil. The design was split-plot with PCU rate as the main plot.  Measurements prior to harvest included SPAD readings of flag-leaves at weekly intervals, foliar disease ratings, plant height, panicle length, and flag leaf tissue nitrogen content. Data taken at harvest included grain moisture, raw yield (adjusted for moisture), dry hulled yield, seed size, lodging, and seed shattering. Yield response with increasing PCU rates was linear and positive for short-statured entries, with no sign of decreasing response at the higher rates. Tall entries showed a quadratic response, increasing initially, then leveling off or decreasing at higher PCU rates.