Impacts of slow release phosphorus and urea on intensively and moderately grazed mixed-grass prairie, and, Impacts of rotational grazing, intensive season-long grazing, and idle land use on soil health in the Missouri Coteau

Two studies were conducted at the Central Grasslands Research Extension Center near Streeter, North Dakota. The first was a 5-year study that was conducted to ascertain the usefulness of slow-release phosphorus (P) and nitrogen (N) fertilizers on intensively grazed and moderately grazed mixed-grass prairie. Second, a 1-year study was conducted to assess soil health and water holding potential on a rotationally grazed, intensively grazed season-long, and idle land use. Annual fertilizer rates of 0, 27, and 48 kg P/ha applied 1 May and 20 June; and 0, 37, and 74 kg N/ha applied 20 June were applied using a slowrelease fertilizer on an intensively (6.49 AUMs/ha) and a moderately grazed (2.21 AUMs/ha) rangeland. Total dry matter production in response to N and P was not significant during the 5-year study on the intensively or moderately grazed trial, although cool-season grass herbage production increased with N applications on the intensively grazed trial. There was no response to warm-season grasses, forb, or shrub herbage production on the intensively or moderately grazed trial. Forb species diversity increased in response to P on the intensively grazed trial with the 1 May P applications while forb diversity on the moderately grazed trial increased on the 27 kg P/ha 1 May and 48 kg P/ha 20 June fertilizer applications. Grass species diversity did not respond to N or P fertilization throughout the course of the study. In a second study, three land uses (rotational and season-long grazing, and idle land) were examined to assess soil health and water holding potential. Infiltration rate on the rotationally grazed site was higher than the season-long or idle site while saturated hydraulic conductivity was highest on the seasonlong grazed site in the A horizon and higher than the idle site in the Bk horizon. Macroporosity was highest on the idle site at the surface, but land uses then did not differ until 50 cm where the idle site had the lowest macroporosity. The rotationally grazed land use then had the highest percentage of macropores at depth, differentiating from microporosity where the idle site had the highest microporosity.