Trampling and Cover Effects on Soil Compaction and Seedling Establishment in Reseeded Pasturelands Over Time

Abstract

A field study in Randall County, Texas, was conducted to determine how soil bulk density and plant cover change over time in response to deferment following a high-density, high-intensity, short-term grazing/trampling event. Green Sprangletop (Leptocloa dubia Kunth.) and Kleingrass (Panicum coloratum L.) were broadcasted at 4.5 kg ha−1 pure live seed (PLS) on former cropland that had a partial stand of WW-Spar Bluestem (Bothriochloa ischaemum L.). A high-density, high-intensity trampling event was achieved with twenty-four 408-kg Bos taurus heifers occupying four 0.10-ha plots (97 920 kg live weight ha−1) for 10 h, with four adjacent 0.10-ha control plots left untrampled. Canopy and basal cover were determined by plant functional group using the Daubenmire method after rainfall events of > 0.254 cm, and a 5.08 × 7.62 cm core was collected to determine soil bulk density. Strips of supplemental plant material were applied in March to test the effects of 100% soil cover on seedling recruitment. Trampled treatments had 30% less vegetative cover (P < 0.01) and average soil bulk densities that were 0.20 g cm−³ higher (P < 0.01) than untrampled plots post trampling. Bulk density decreased with deferral until there were no significant differences between treatments (240 d). However, WW-Spar basal cover increased in both treatments, with no differences between treatments. Trampling did not affect seedling recruitment, but supplemental cover increased seedling density on three of five subsequent sampling dates (P < 0.05). Canopy cover of warm season perennial grasses in trampled treatments surpassed that of the untrampled treatments during the early growing season of 2016 (P < 0.01) but were no different after mid-June. Hydrologic function can be maintained with high stock densities by providing adequate deferment to reestablish sufficient cover and allow natural processes to restore porosity. © 2020