Effects of Stocking Rate and Botanical Composition on the
Physical Characteristics of the Riparian Zones of Pastures
(A Progress Report)
Grazing management practices that allow congregation of cattle near pasture streams may increase sediment, phosphorus, and pathogen loading of the streams by removing vegetation and causing manure accumulation near the streams. Forage sward height, bare and manure-covered soil, and forage species were measured along the banks of streams in 13 pastures on 12 cow-calf operations in southern Iowa. Forage sward height decreased as the proportion of tall fescue at the vegetated sites increased, as the stocking rate increased, and as the proportion of reed canarygrass at the vegetated sites decreased. The proportion of soil that was bare tended to increase as the proportion of reed canarygrass at vegetated sites decreased and the proportion of tall fescue at vegetated sites or the stocking rate increased. The proportion of soil that was manure-covered increased as the stocking rate and proportion of tall fescue at vegetated sites increased and the proportion of reed canarygrass at vegetated sites decreased. In stepwise multiple regressions, stocking rate was not selected to predict sward height and the proportion of bare soil. In contrast, stocking rate was the first factor selected to predict the proportion of soil that was covered with manure. Selection of tall fescue in the stepwise multiple regressions implied that the sward height decreased and manure cover increased as tall fescue as a proportion of vegetated sites increased. The presence of tall fescue and increasing stocking rate may increase cattle activity near streams reducing sward height and increasing manure cover. However, the effects of stocking rate and the botanical composition on the proportion of bare soil along stream banks were relatively small.