Tallgrass prairie plant establishment in Conservation Reserve Program fields

The Conservation Reserve Program (CRP) has resulted in more than 8.4 million acres of native warm season grass, forb, and legume species being planted on former agricultural land. These plantings are less diverse than prairie remnants and many prairie restorations, but they represent a substantial increase in the total land cover occupied by native plant species. However, little is currently known about the plant species richness in these plantings. We evaluated plant species establishment in 30 CRP sites in southwest Iowa, which were planted as either warm season grasses and forbs (conservation plan 2- CP2) or prairie habitat restorations (CP25). Two remnant prairies were also surveyed for comparison. The CRP sites were planted with between 5 to 33 species, including a minimum of 3 grass species. Each site surveyed was at least 4 years post-planting. There was a significantly difference (ANOVA of total site richness, p = 0.001) in species richness in the remnants and two CRP planting types, but no difference between CRP types. CRP plantings averaged 58.7 (CP2) and 53.0 (CP25) species per site while prairie remnants contained an average of 92.5 species. The proportion of planted species which established at a given site decreased as the number of planted species increased (r² = 0.443), but the total species richness was not correlated with the number of species planted. Although increasing planting species richness does result in increasing planted species establishment, many species in high diversity plantings are failing to establish.