Rapid Yield Estimation Methods for Unharvested Rice Cultivated for Migrating and Wintering Waterfowl

Abstract

Land managers in the southeastern United States cultivate rice (Oryza sativa) to provide calorie-dense forage for autumn-migrating and wintering waterfowl and other migratory birds. Conservation planners require accurate yield estimates for rice and other energy-rich croplands to parameterize bioenergetic models and support data-driven, adaptive resource management efforts. We developed a rapid method to efficiently estimate rice yield and quantified associated precision, accuracy, sampling time, and operating costs in the Lower Mississippi Alluvial Valley (n = 16 fields). We compared a visual index of seed-head size and density using ocular scores (1–10; i.e., rapid assessment) to 1-m2 harvested plots within each field. We regressed our visual index against known rice yield estimates (kg [dry] ha–1) and related our yield estimates to rice cultivation practices to inform management actions that maximize yield and cost efficiency for wildlife management. Our model (R2a dj = 0.80) reliably estimated rice seed yield within 20–40 min per field. We found that yield was positively correlated with input cost, but that 125–180 kg ha–1 of post-emergence nitrogen and at least one herbicide application seemed to balance yield production while minimizing costs (US$900–1200 ha–1). We suggest our rapid visual index method be incorporated into resource monitoring protocols to improve conservation planning initiatives.