Revegetation of Abandoned Agricultural Fields in the Sonoran Desert

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1 This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Revegetation of Abandoned Agricultural Fields in the Sonoran Desert Jerry R. Cox 1 and Gary W. Thacker 2 Early Descriptions ABSTRACT Historical records show that southeastern Arizona was a grassland before Today, shrubby plants dominate the region. From 1880 to 1920, dramatic changes in the composition of vegetation took place along major waterways. Flooding and the resulting channelization, plowing of the floodplains, and livestock grazing essentially eliminated the natural process of shallow groundwater recharge. The purpose of this paper is to determine why the changes occurred, and determine if the resource can be reclaimed. INTRODUCTION Early explorers in southeastern Arizona maintained journals describing vegetation. Their records provide descriptions of grazing areas and vegetation prior to 1880: Santa Cruz Basin. "We were off this morning (from Tucson)... and soon entered a thickly wooded valley of mesquite. A ride of nine miles brought us to San Xavier de Bac... a mile farther we stopped in a fine grove of large mesquite trees near a river, where there was plenty of grass. The bottomlands resembled meadows being covered with luxuriant grass and but a few trees. The bottoms (between San Xavier and Tubac) in places are several miles wide... and covered with tall, golden colored grass... divided by a meandering stream a dozen yards wide and as many inches deep, this shaded by cottonwoods, willows, and mesquites" (Bartlett 1854). San Pedro Basin. "The valley of this river is quite wide and is covered with a dense growth of mesquite, cottonwood, and willow. The majority of the valley has good grass... the bottoms having very tall grass. There is excellent trout fishing, but the grass makes travel by wagon very difficult' (Cooke 1938). Sulphur Springs Basin. "This vast area is without either running streams or timber, but covered to a great extent with fine grass. Approaching Sulphur Springs from the east, the road lies for miles through a dense growth of sacaton grass" (Hinton 1878). 1 Texas A&M Research & Extension Center, Vernon, TX 2 Pegasus Machinery Co., Tucson, AZ. 306

2 San Simon Basin. The valley of the San Simon is miles in width, and contains much fine grazing and some agricultural land. It is covered with gramagrass. Mesquite is most conspicuous and abundant from the base of the mountain (Mount Graham)... and sparse on the mesa... the sacaton and grama cover the plain... The country abounds in game, such as deer, antelope, wolf, wild turkey, duck and quaw (Hinton 1878). IRRIGATED AGRICULTURE Farming in southeastern Arizona was concentrated initially near major lowland drainage areas. Water was taken directly from rivers. This practice was hazardous on the San Pedro River because beaver would build dams in irrigation ditches at night and limit water flow to cropland. During the floods of 1895 and 1900, channel cutting resulted from the combination of farming, wagon trails, and grazing. The soils associated with lowlands were extremely rich because above- and belowground growth of sacaton added organic carbon and nutrients. Sacaton grasslands had slowed floodwater, trapped sediment, and enhanced soil fertility on southeastern Arizona floodplains for thousands of years. Once removed by plowing, burning or grazing, there was nothing to slow water movement in the lowlands. The result was channelization. From 1930 to 1960, irrigated agriculture expanded rapidly in Arizona s southeastern counties (Table 1). Decades of peak acreage were in the 194o s in Cochise, 195o s in Pima and Pinal, and 1960 s in Graham and Santa Cruz Counties. During periods of maximum cultivation, about 2.6 million acres were cultivated in the five southern counties; and if the areas farmed in 1980 are subtracted from the peak acreage, then 2.2 million acres of farmland have been abandoned in the past 40 or 50 years. Urban growth and water use in urban areas is predicted to increase dramatically by the year 2030 (Arizona Water Commission 1975). As urban demand for water increases, water will be diverted from agricultural uses, which have lesser value. This means the abandonment of more of the region s farmland, a phenomenon occurring nationally at an estimated average rate of 3 million acres per year (Sheets 1981). Farmland is dominated by tumbleweed immediately after abandonment, and if undisturbed for 2 or 3 years, tumbleweed is replaced by mustards (Cox and Madrigal1988). Annuals may be replaced in 3 to 10 years by half-shrubs such as baccharis and burroweed. After 10 years, abandoned fields are usually dominated by widely spaced half-shrubs and shrubs such as creosotebush, saltbush and mesquite. 307

3 Counties - Acres of abandoned farmland Year Cochise Graham Pima Pinal Santa Cruz Total ,990 18,300 8,620,300 2,560 45, ,900 38,820 10,160 25,430 4,770 84, ,980 32,400 16,880 28,650 2,610 93, , , ,550 75,740 4, , , , , , ,610 2,174, , , , , ,210 2,097, , , , , ,780 2,358, ,920 51,850 50, ,0 2, , ,630 45,900 47, ,610 3, , , , , , ,810 2,244,090 Table 1. Acres of irrigated agriculture in southeastern Arizona between 1990 and 1980 and estimates of abandoned farmland in Abandoned farmland acres were obtained by subtracting 1980 estimates from peak production years (Cox et al. 1983). Raindrop impact causes compaction of bare soil which reduces infiltration and enhances runoff, but wind erosion at the present is the most serious problem. In late June, moisture surges from the Gulf of Mexico generate long squall lines in southeastern Arizona. In front of the advancing squall lines, wind gusts approach 70 miles per hour, and visibility may decrease to zero. Dust storms, generated as the squall lines, pass over abandoned farmland were responsible for more than 440 automobile accidents between 1960 and The following studies were initiated to determine if perennial plants can be established with irrigation water before water rights are transferred from agricultural to municipal uses, and to evaluate the survival of two grasses (big and alkali sacaton) which dominated abandoned farmland sites prior to cultivation and irrigation. CAN PERENNIAL PlANTS ESTABLISH AND PERSIST ON ABANDONED FARMlAND? Studies at San Xavier, Arizona A study was conducted on abandoned farmland at the San Xavier Indian Reservation, south of Tucson. The site was plowed and sown to cotton or alfalfa between 1933 and 1971 and abandoned in Reclamation studies were conducted between 1980 and A seedbed was prepared by disking in either spring, summer or fall, and seeding 7 perennial grasses. Perennial grass seeds need continuous soil moisture for 7 days to ensure germination, and additional soil moisture within 7 days after germination to ensure establishment. Therefore, grasses received either 0, 1, 2, 3 or 4 flood irrigations at either 0, 7, 14 and 21 days after 308

4 planting. One-half of each irrigated area was hand weeded at 15, 30, 45 and 60 days after the final irrigation. Conclusions The intent of our study was to determine the effects of planting season, supplemental irrigation, and weed competition on the establishment and production of 7 perennial grasses. We found that small seed of A-68, L-28, L-38 Lehmann lovegrass and A-84 Boer lovegrass were unable to emerge from silty clay loam soil irrespective of planting season, irrigation amount or weed competition; hence, these grasses were unacceptable for reclaiming abandoned farmland (Cox and Madrigal 1988). Catalina Boer lovegrass, and A-130 and SDr 1 blue panicgrass seedlings from seed planted in summer often persisted for 4 months or more after planting, whereas seedlings from seed planted in spring and fall always died in less than 4 months. Our most important finding is that Catalina and both blue panic grasses will germinate and produce seedlings under natural rainfall, but longterm persistence was unreliable because plants eventually died. We might have missed this important point and recommended seeding without supplemental water, if the study plan had not included long-term evaluations. Therefore, these grasses are not adapted for planting on abandoned farmland if their survival is dependant on natural rainfall. Blue panicgrass A-130 and SDr 1 plants, established with 3 or 4 irrigations in summer, will persist for 52 months after planting and weeding to remove annual competition is unnecessary. The steady decline in plant persistence and forage production with time; however, may suggest that neither blue panic grass accession is adapted and both will disappear eventually. Thus, there is the distinct possibility that the methods and plant materials used in this study are not adequate to reclaim abandoned farmland in southeastern Arizona. Studies at Three Points, Arizona A second abandoned farmland study was conducted at the Buckelew Farm near Three Points. The site was sown to cotton between 1954 and 1975 (Thacker and Cox 1992). In 1976, the farm was purchased by the City of Tucson, and the water rights transferred from agricultural to municipal uses. After irrigation water is diverted from agricultural lands to municipalities, wind-borne soil particles from abandoned farmland reduce driver visibility and contribute to vehicle accidents. To stabilize soils, a cooperative study was initiated with the City of Tucson, a local farmer, and the state of Arizona. The City contributed two irrigation wells and 1,000 acres of abandoned farmland, the farmer provided machinery and fuel, and the Arizona Department of Environmental Quality provided a grant. The purpose of the study was to establish perennial crops with irrigation before the water rights were transferred to the City of Tucson, and monitor plant persistence to determine relationships between plant survival, rainfall amount and distribution, and air quality after irrigation was discontinued. A seedbed was prepared by plowing a sandy clay loam to 18 inches, and disking prior to the summer rains. In this experiment, we broadcast Catalina Boer lovegrass, ~~s-75 kleingrass, Common buffelgrass, COchise lovegrass, Kalahari bottlebrush grass, and Hatcheta sideoats gramagrass seeds in 1986 and 1987, and collected data from 1987 to Irrigation treatments were flood applications at either 0, 2 applications at 7 day intervals, or 4 applications at 7 day intervals. 309

5 Conclusions Catalina Boer lovegrass, S-75 kleingrass and Common buffelgrass seed, germinated after the summer rains, but only Common buffelgrass seedlings survived for more than 6 months. Buffelgrass plants established under natural rainfall were still present in fall 1996, but plant densities were less than 1 plant per 9 square ft. The native grass, sideoats grama, germinated after the initial irrigation, but most plants died before the second application, seven days later. Within 48 months, established sideoats plants began to die, and few plants were present in seeded plots during fall Catalina Boer lovegrass, 5-75 kleingrass and Common buffelgrass seed germinated after the second irrigation, and after 1 year densities and production were similar on plots receiving either 2 or 4 irrigations. By years 2 and 3, Catalina and S-75 densities declined by approximately 50%, but Common buffelgrass densities either remained constant or increased. We frequently observed quail feeding in kleingrass plots, and deer and javelina feeding in buffelgrass plots. Observations in 1992 and 1996 indicated establishment of sideoats grama, three-awns and sand dropseed in irrigated lovegrass and kleingrass plots, but no native grass establishment in buffelgrass plots where plant densities have remained relatively constant for the past 10 years. Studies at the University of Arizona-Romero Road Farm, Tucson, Arizona To determine if sacaton could survive on abandoned farmland where water flows from natural drainage had been diverted, 40 big and alkali sacaton collections from sites in west Texas, southern New Mexico, southeastern Arizona and the states of Zacatecas and Chihuahua in Mexico, were transplanted at the Romero Road Farm during spring All plants were watered in spring, summer, and fall 1981, but only one-half of the plants continued to receive irrigation in summers between 1982 and Conclusions After discontinuing irrigations, all big and alkali sacaton collections died within 24 months. IMPLICATIONS Under current soil and climatic conditions it is unlikely that big and alkali sacaton, and sideoats grama will establish and persist on abandoned farmland without the annual application of irrigation water. In contrast, buffelgrass, an introduced perennial from Africa, can be easily established and will persist for 10 years after establishment with 2 or 4 initial irrigations. One important observation was the establishment of native, perennial grasses in plots seeded to kleingrass and Catalina Boer lovegrass, and irrigated 2 to 4 times. We are not suggesting that introduced plants are the only perennial plants adapted on abandoned farmland, even though this does appear to be true. It may be that native plants will establish where introduced plants were initially sown after organic carbon and soil nutrients have accumulated; therefore, it may be possible to establish native plants within introduced stands. We have observed native plants invading fenced stands of Lehmann lovegrass in southeastern Arizona, and Dr. Bruce Roundy and graduate students have documented the establishment of native plants (from seed) in mature Lehmann lovegrass stands. It may be possible to use introduced plants to enhance infiltration and soil nutrients, and then seed natives into introduced stands. As desert farmland is removed from production and the water rights transferred to municipalities, the new owners will be faced with management problems. To reduce environmental impacts, we 310

6 recommend the establishment of a permanent vegetation cover before retirement, this will reduce the headaches and liabilities associated with land management. If adapted vegetation is established before retirement, the site will be stabilized with plant cover. Beneficial plant cover will limit blowing soil and inhibit tumbleweeds from dominating the land. The costs of establishing vegetation are easy to measure, the benefits are more difficult to quantify because they relate to health, safety, and legal issues. The environmental costs of abandoning farmland are in the form of dust pollution, erosion from water runoff, tumbleweeds blowing onto roadways, and automobile accidents caused by blowing dust. In the past, society was either not concerned or not aware of potential environmental impacts from abandoned farmland. Today, however, most are aware of adverse actions, and we in agriculture and municipalities must offer alternatives and incentives to minimize adverse environmental impacts. REFERENCES Arizona Water Commission Phase 1-Arizona State Water Plan. Inventory of Resources and Uses. Phoenix, AZ. 37 pp. Bartlett, J. R [Personal narrative of exploration and incidents in Texas, New Mexico, California, Sonora and Chihuahua. Volumes 1 and 3]. The Botanical Review 24: Cooke, P. G [Journal of the March of the Mormon Battalion, ]. The Botanical Review 24: Cox, K. R., H. L. Morton, J. T. LaBaume and K. G. Renard Reviving Arizona s Rangelands. J. Soil and Water Conservation 38: Cox, J. R. and R. M. Madrigal Establishing perennial grasses on abandoned farmland in southeastern Arizona. Applied Agricultural Research 3: Thacker, G. W. and J. R. Cox How to establish a permanent vegetation cover on farmland. Arizona Cooperative Extension, College of Agriculture, University of Arizona. #191051, 23 pp. 3