Vegetation, phosphorus, and dust gradients downwind from a cattle feedyard

Abstract

A native shortgrass pasture downwind from a 25,000-head beef cattle feedyard near Bushland, Tex. degraded after the feedyard was stocked in 1970. Objectives were to determine pre-1970 vegetation, quantify current vegetation, and describe changes in vegetation, soil P and dust deposition with distance from the feedyard. Pre-1970 vegetation was documented with published measurements. In 2000, plant cover was quantified using 600 quadrats. Soil P, conserved in the local soil, was measured in soil samples from 119 locations. Dust was collected at 12 locations. From 1966-1972, cover was 18.8% blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] and 7.4% buffalograss [Buchloe dactyloides (Nutt.) Engelm.]; the 2 species comprised 95% of vegetation cover. In 2000, perennial grass (75-99% blue grama) cover averaged 3.7% at < 150 m from the feedyard, and increased to 28% at > 525 m from the feedyard. Conversely, annual grass (67% Hordeum pusillum Nutt.) and annual forb [72% Kochia scoparia (L.) Schrad.] covers were 49% and 35% nearest the feedyard and decreased to 9% and 1%, respectively, at > 525 m. Over a similar distance, soil P decreased from 75 to 17 mg kg-1. Dust deposition rate decreased with distance from the feedyard. Manure dust contribution to total dust ranged from negligible to 89%. It was estimated that 20-30 kg N ha-1 year-1 were deposited over 30 years to areas nearest the feedyard. Changes in vegetation and soil P were greatest at < 500 m from the feedyard. Vegetation and soil P were near values expected for shortgrass prairie at > 500 m downwind from the feedyard. The pattern of vegetation, soil fertility, and dust deposition gradients strongly suggested that the feedyard was the primary cause of the observed changes, although a direct causal link could not be established, and other factors, such as grazing, could have contributed to the observed changes.