Effect of Livestock Grazing or Feeding on Cropland Soil Compaction and Nutrient Deposition
(ABSTRACT)
N. Thompson1, B. Whitney2, W. Poland2
1 Dickinson State
University - Department of Agricultural Studies and
2 North
Dakota State University – Dickinson Research Extension Service
As agriculture in North Dakota continually evolves, livestock
grazing of unharvested crops is increasing in popularity. The objective of this
project was to determine the effect of livestock grazing or feeding on soil
compaction in cropland and to measure the nutrient deposition caused by using
these practices. The treatments (2 replicates/treatment) included dry beef cows grazing in harvested corn, (8.01 ac/replicate) grazing
oat swaths (7.95 ac/replicate) and fed oat hay (9.83 ac/replicate). Stocking
rate varied with treatment replicate and was estimated at the beginning of the
grazing period to provide enough grazing pressure to remove 50% of available
forage in 8 weeks. The oat hay feeding areas were mob grazed prior to the initiation
of the grazing period to remove all grazable forage. Soil samples were taken
before mob grazing (oat hay) in early October, treatment immediately prior to
the initiation of grazing period in mid October and one week following the
termination of grazing in mid December. Soil samples were used to establish
bulk density and were later analyzed for Nitrogen, Phosphorus, Potassium, pH,
Electrical Conductivity, Organic Matter, Chlorine, and Sodium. Soil density was
not affected by time (P= .17), but was affected by treatment (P=.01).
Soil density increased with the feeding of hay in the dry lot, and decreased
with the grazing of oat swaths. The corn lots were intermediate. Nitrogen
(P=.01) and sodium (P<.01) decreased with the grazing period, while phosphorus
(P=.04) increased in the grazing period. Density, phosphorus, and sodium
increased in the dry lot. Density was least in the oat swaths and intermediate
in the corn, while phosphorus was low in the corn and intermediate in the oat
swaths. Sodium was high in the dry lot and intermediate in the oat swaths and
corn. Potassium (P<.01)) was low in the corn and pH (P=.01) was low in the
oat swaths. Electrical conductivity, organic matter, and chlorine were not
affected (P>.91) by treatment or time. Cattle grazing or feeding on cropland
does not increase soil density and any treatment affects were relatively small.
Soil nutrient concentration appears to be affected inconsistently across both
treatment and time and warrant future investigations. The increased popularity
in extending the grazing season onto cropland with beef cattle seems feasible
in Southwest North Dakota.