Changes in Soil Microbial Community Under a 28-Year Conservation Reserve Program in the Semi-Arid Grasslands.

The Conservation Reserve Program (CRP) in the Southern High Plains (SHP) plays a crucial role in maintaining ecosystem health by reducing soil erosion. However, the restoration of its soil biological health (biological community and function) over time have not been clearly elucidated. The objective of this study was to describe changes in the soil microbial community composition (SMC) over years of established CRP. Soil samples (0-10 and 10-30 cm) were collected in 2012 and 2014 from 26 fields across seven counties within the SHP and included seven croplands (0 y in CRP), 16 CRP fields of varying ages (8-28 y as of 2014), and three rangelands with no plow disturbance. Total fatty acid methyl ester (FAME) abundance, as a proxy of microbial biomass, increased with CRP years at 10-30 cm in 2012 and in both depths in 2014. The physiological stress of microbial community indicated by ratios of saturated: monounsaturated FAME biomarkers consistently decreased with CRP restoration years in both sampling years in both depths. A shift in the SMC was measured during CRP restoration at 10-30 cm in 2012 and both depths in 2014 with an increase in relative total fungal abundance through the initial 15 years of CRP and then a decline after 15 years. The increase of fungi, mainly from arbuscular mycorrhizal fungi, was highly related to carbon sequestration (R²=0.46, n=104). The overall increase in soil microbial biomass and decrease in microbial physiological stress with increasing CRP years indicated that CRP is a valuable restoration program in terms of soil health for the fragile sandy soils in the SHP.