Gilbert: Mesquite in South Texas

Postscript 1

Professor Peter Felker, Texas A&M Kingsville, estimated the nitrogen budget for south Texas mesquite grassland for a class he teaches. I organize his figures in the table below. These estimates are extrapolated from the following sources:

Loftis, S.G. and E.B. Kurtz. 1980. Field studies of inorganic nitrogen added to semiarid soils by rainfall and bluegreen algae. Soil Science 129: 150-155.

Chapman, Liebig, Rayner 1949. Nitrogen gains and losses. Hilgardia 19:111.

Gist, C.S. and P.R. Sferra. 1978. Animal consumer roles in desert nitrogen cycles. In Nitrogen in Desert Ecosystems. N.E. West and J.J. Skujins (ed). Dowden Hutchison & Ross Publ. pp. 152-159.

Rodel, M.G.W. 1970. Herbage yields of five grasses and their ability to withstand intensive grazing. XI International Grassland Conference, M.J.T. Norman (ed). Queensland Australia. Univ. of Queensland Press. pp. 618-621.

Nitrogen loss via cattle in South Texas
(assuming one cow/20 acres, and each cow consumes 25 lb dry matter/day averaging 8% crude protein) Nitrogen gain via rainfall and soil crust lichens

a. 9125 lb dry plant matter consumed/year/cow a. 1.1 lb/acre NO₃-nitrogen from rainfall
(assume 19" rain/yr)
b. 1.1 lb/acre NO₃-nitrogen from soil
blue-green algal lichen crust
(assume 43 days activity @ 15% cover)

b. 730 lb protein (8% of a.)

c. 117 lb nitrogen (16% of b.)

d. 53 lb nitrogen volatilized (45% of c.) in 20 acres

e. 2.6 lb nitrogen per acre volatilized

f. 500 lb gain by animal/year

g. 100 lb dry matter/carcass (20% of f.)

h. 30 lb protein (30% of g.)

i. 4.8 lb nitrogen (16% of h.) per 20 acres

j. 0.24 lb nitrogen/acre (carcass removal)
Total loss/yr - 2.84 lb/acre (e. + j.) Total gain/yr = 2.2 lb/acre (a. + b.)

Nitrogen loss via cattle in South Texas (assuming one cow/20 acres, and each cow consumes 25 lb dry matter/day averaging 8% crude protein)	Nitrogen gain via rainfall and soil crust lichens
a. 9125 lb dry plant matter consumed/year/cow	a. 1.1 lb/acre NO₃-nitrogen from rainfall (assume 19" rain/yr) b. 1.1 lb/acre NO₃-nitrogen from soil blue-green algal lichen crust (assume 43 days activity @ 15% cover)
b. 730 lb protein (8% of a.)
c. 117 lb nitrogen (16% of b.)
d. 53 lb nitrogen volatilized (45% of c.) in 20 acres
e. 2.6 lb nitrogen per acre volatilized
f. 500 lb gain by animal/year
g. 100 lb dry matter/carcass (20% of f.)
h. 30 lb protein (30% of g.)
i. 4.8 lb nitrogen (16% of h.) per 20 acres
j. 0.24 lb nitrogen/acre (carcass removal)
Total loss/yr - 2.84 lb/acre (e. + j.)	Total gain/yr = 2.2 lb/acre (a. + b.)