The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Wednesday, January 30, 2008
19
Using Soil Moisture to Estimate the Economic Value of Rainfall Events for Range Forage Production
L. Allen Torell1, Kirk C. McDaniel2, and Brian H. Hurd1. (1) Department of Agricultural Economics and Agricultural Business, New Mexico State University, P.O. Box 30003, MSC 3169, Las Cruces, NM 88003-3169, (2) Department of Animal and Range Sciences, New Mexico State University, P.O. Box 30003, MSC 3-I, Las Cruces, NM 88003
Using probe recorded and simulated soil moisture, we estimated the relationship between annual end-of-season forage yield and weather conditions on the New Mexico State University (NMSU) Corona Ranch located in central New Mexico. Daily levels of soil moisture depend on the history of storm events. Based on the 1991 to 2006 storm history for the Corona Ranch we categorized daily soil moisture into low (< 20% SM by volume), moderate (20% < SM ≤ 30%), and high (>30%) levels and used the defined moisture conditions along with temperature to estimate annual grass yields. We then estimated how grass yields and potential economic returns would change if additional storm events had occurred. As compared to the driest soil moisture state, grass yield was found to increase by 2.45 kg/ha if daily soil moisture was categorized to be at an intermediate level and by 6.43 kg/ha if it was high. An added 1 inch (25.4 mm) rain storm on 1 April 2003, a relatively dry year, and 2005 (a normal year) would add between 33 and 57 kg/ha (0.09 to 0.16 AUMs/ha) to forage production. If the added forage were valued at $9.80/AUM, the single large storm event would add between $0.88 and $1.57/ha in economic value. The added forage would have a total value of $5,500 to $10,000 and support between 50 and 80 head for a year on the 6,175 ha of blue grama (Bouteloua gracilis) rangeland found on the Corona Ranch. For the dry climate of the Corona Ranch, soil moisture is built with storms > 5 mm which occur on about 20 days of the year. Each large storm has a significant economic value.