Subirrigated Meadow Response to Application of Nitrogen, Phosphorus, and Atrazine1

Abstract

AbstractBotanical composition of native hay meadows throughout the True Prairie has shifted from predominantly native, warm‐season grasses to introduced, cool‐season species following mismanagement. To determine if a shift in composition back to warm‐season grasses and subsequent increased seasonal production could be achieved, atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] herbicide in combination with N and P fertilizer was evaluated on an eastern Nebraska subirrigated meadow. The soil is classified as a Lawet Variant fine sandy loam (fine‐loamy, mixed [calcareous], mesic Fluvaquentic Haplaquoll). Five rates of N (0, 45, 90, 135, and 180 kg ha−1), two rates of P (0 and 34 kg ha−1), and two rates of atrazine (0 and 2.2 kg ha−1) in factorial combination were arranged in a randomized complete block design. Atrazine and P were applied in late April to late May, and N was applied in early June in 1982 through 1984. A combination of 180 kg N ha−1 and 34 kg P ha−1 produced dry matter yields 95,101, and 77% greater than untreated plots in 1982, 1983, and 1984, respectively. Atrazine altered botanical composition from predominantly cool‐season grasses to predominantly warm‐season grasses. Changes in species composition by weight indicated a twofold increase in warm‐season yield. This shift in seasonal distribution of yield was accomplished without a reduction in total dry matter yield compared with plots recieving 180 kg N ha−1 in combination with 34 kg P ha−1.