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University of Arizona (1971)

FERTILIZATION AND BURNING EFFECTS ON USE OF DESERT GRASSLAND BY CATTLE

Bryant, David Arley

Titre : FERTILIZATION AND BURNING EFFECTS ON USE OF DESERT GRASSLAND BY CATTLE

Auteur : Bryant, David Arley

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1971

Résumé
A two-year study was conducted on desert grassland near Elgin, Arizona to compare the effects of nitrogen, phosphorus, and nitrogen plus phosphorus fertilization, burning and a combination of fertilization and burning on soil components, plant components and subsequent utilization of forage by cattle. The specific objective of this study was to determine how and possibly why fertilization and burning influence the utilization of blue grama (Bouteloua gracilis (H.B.K.) Lag.) and curlymesquite (Hilaria belangeri (Steud,) Nash.) by cattle. The leaves of both species were collected at che time of grazing and analyzed for crude protein, phosphorus, total alcohol soluble sugars, total nonstructural polysaccharides and moisture. Also, soil samples were collected and analyzed for Kjeldahl nitrogen, nitrate nitrogen and phosphate. The utilization of blue grama and curly mesquite was measured during the summer and fall on the variously treated plots using the grazed-class method. Soil nitrate nitrogen was significantly correlated (r = 0,361 to 0.710) with leaf crude protein in the summer, but not in the fall, and leaf crude protein was usually significantly increased (P<0.05) above control plant levels by nitrogen fertilization and a combination of nitrogen fertilization and burning. Crude protein was not significantly increased above control plant levels by burning alone or in combination with phosphorus fertilization. Soil phosphate was significantly correlated (r = 0.352 to 0.732) with leaf phosphorus in both the summer and fall, and phos phorus fertilization usually significantly increased leaf phosphorus above control plant levels in the slimmer but not in the fall. Neither burning nor fertilization, alone or in combination, had a significant effect on leaf sugars or leaf total nonstructural polysaccharides. However, leaf moisture was significantly increased above control plant levels during the summer, but not the fall, by burning and nitrogen fertilization in combination. The utilization of blue grama and curlymesquite by yearling cattle was generally higher on areas treated with both nitrogen fertili zation and burning than on areas receiving either treatment alone, although the results were not always significant. The utilization on plots receiving both treatments was usually significantly greater than the utilization on control plots.

Mots clés : Grassland fires — Arizona. ; Range management — Arizona. ; Cattle — Arizona. ; Fertilizers — Arizona. ; Prescribed burning — Arizona. ; Rangelands —

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