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Dryland management research has been conducted at Bushland since 1939. Terraces were installed in 1949 to control and use runoff from soils with slopes of 1.0 to 1.8%. The terraces were later modified about 1955 to include a level bench area for spreading storm runoff from the adjacent watershed. Crop growth and water conservation were compared for the level, graded (about 6 inches per 1000 feet), and the new conservation bench terraces. Little differences in yield have been measured for crops grown on either level or graded terraces. The modified level- bench terraces increased the amount of water available for annual crops an average of 4 inches and obtained yields similar to crops grown after an intervening fallow period. One of the most successful and dependable dryland cropping sequences used on the terraces has been the Wheat- Sorghum-Fallow (WSF) system that produces two crops in three years. Soil water storage and crop yield using WSF is similar when using either no or stubblemulch (sweep) tillage, but the measured storm runoff during fallow is greater with no tillage. These results show that crop residues on the soil surface increase the amount of soil water stored during fallow by covering the soil and reducing evaporation of soil water.
Throughout the Great Plains, crop residues that cover the soil have consistently increased water conservation and yields. The residue amount needed to increase water conservation to more than 35% is about 4000 lbs/acre for wheat with a corresponding grain yield of about 65 bu/acre. The amount of residue produced under dryland conditions is, often, too limited to reduce storm runoff or soil water evaporation. Research at Bushland shows that, in the Southern Great Plains, dryland winter wheat and grain sorghum averages about 1,500 lbs/acre or about one quarter of the residues produced under irrigated conditions. To increase soil water conservation, limited irrigation has been applied to increase both grain and residue yields. For example, irrigation increased grain and straw production of wheat and provided the residues (average 6,900 lbs/acre) that resulted in an average 3000 lbs/acre dryland sorghum grain yield after no-till fallow. When dryland grain sorghum planted after no till wheat received a single irrigation during the boot stage, grain yield increased by as much as 1500 lbs/acre. Limited or deficit irrigation may be combined with dryland residue management to increase grain and residue yields of future production systems.
R. Louis Baumhardt, Soil Scientist, USDA-ARS, Bushland, TX
Problem. The need for alternative dryland crops in the southern Great Plains results from developing weed control problems in cropping systems that repeat chemical control methods, and declining water tables and irrigation. This study will determine the adaptability and best management practices, BMPs, for growing various alternative crops under dryland conditions using the Conservation Bench Terrace (CBT). The CBT is a system of level terraces and ridges for capturing storm runoff from sloping watersheds and spreading it on an adjacent level crop area that is 50% smaller. Long-term annual runoff from the stubblemulch tilled wheat-sorghum-fallow (WSF) cropped watersheds has averaged 1.3" resulting in about 4.0" more water for crops grown on the benches compared to graded terraces. Because of this additional water, annual crops on the CBT level benches such as wheat, grain sorghum, corn, and sunflower achieved yield levels comparable to those same crops grown after an intervening fallow periods (2 crops in 3 years). Objectives. This study will be conducted to evaluate: (i) CBT water management for producing a drought sensitive crop, such as soybean, under dryland conditions, (ii) cropping strategies for producing a long season drought tolerant crop, cotton, during a limited growing season, and (iii) differences in proven crop management practices developed using CBT with higher profit/risk cropping alternatives. Approaches. The watershed portion of each terrace will be cropped according to the WSF rotation. The benches will be managed with either crop rotations of sorghum with cotton, soybean, and sunflower or with continuously cropped soybean, sorghum, wheat, and cotton. Conservation of precipitation as soil water, and crop growth and yield will be measured and used for crop growth modeling. Results. This information will be used to develop BMPs for producing alternative crops under demanding conditions using field data and computer crop growth simulation models.
R. Louis Baumhardt, Soil Scientist, USDA-ARS, Bushland, TX
Problem. The agricultural industry on the Texas High Plains generates some $3.25 billion annually from livestock and supporting feed grains and forage crop production. Much of the intensive crop production depends on irrigation water supplied from the declining Ogallala aquifer. Dryland crop production systems that integrate livestock grazing are needed for the continued success of the southern Great Plains agriculture industry. Objectives. A long-term study will be initiated in 1998 to develop Best Management Practices (BMPs) for integrating livestock grazing into a dryland Wheat-Sorghum-Fallow (WSF) residue management cropping system. We will use site specific management technologies such as Differential Global Positioning Systems (DGPS) and Geographic Information Systems (GIS) when possible. Approaches. The effects of cattle grazing on soil compaction, water conservation, and the growth and yield of wheat and sorghum will be determined for the dryland WSF cropping sequence. This rotation sequence will be established beginning with a sorghum crop during the summer 1998 and wheat during the fall 1998. Cattle grazing will begin with the 1998 wheat crop and sorghum residues and continue until mid-March. Soil measurements include penetration resistance, density, depth to the caliche, and rain infiltration. Crop measurements include water use and the yield of grain and forage/ residue. These measurements will be manually grid sampled using DGPS for location and recording yield monitors. Cattle grazing density, grain-yield, residue-production, soil density, and soil depth will be mapped from the location data and cross-correlated. Results. This information will be used to evaluate soil qualities in relation to grazing pressure and its economic impacts. As the study evolves, BMPs that improve production will be developed and evaluated.
R. Louis Baumhardt, Soil Scientist, USDA-ARS; Steven R. Winter, Professor Agronomy, TAES, Bushland, TX; L. Wayne Greene, Professor Animal Science, TAES, Amarillo, TX
Problem. Many decisions on commercial uses of chemicals and tillage practices are based on projected environmental impacts using computer simulation-models or data limited to 3 - 5 years of measurements. Longterm research to quantify tillage and agricultural chemical impact on soil and environmental conditions is needed. For example, infiltration, runoff and water conservation effects of no-tillage (NT) and stubblemulch (SM) tillage have been measured on field-sized (5- to 10-ac) graded-terraced watersheds in a dryland, 3-yr, winter wheat-sorghum-fallow (WSF) sequence for about 40 years. Runoff measurements with H-flumes in these longterm research plots and corroborating infiltration measurements with a rainfall simulator show that NT has more runoff than SM. The amount of water conserved in the soil using NT was greater than SM, however, because NT reduced evaporation. Soil, chemical and nutrient loses in runoff monitored on these mini- watersheds show that 1) few fertilizer nutrients are lost in runoff, 2) no evidence of atrazine loss in runoff or accumulation in the soil is observed, and 3) propazine appears to have a greater potential for negatively impacting the environment under semiarid conditions than does atrazine. Objectives. This study will continue to quantify the longterm tillage impact on: (i) conservation of precipitation as soil water, (ii) ag-chemical and soil losses in runoff, and (iii) spatial and temporal variability of crop growth. Approaches. The ongoing tillage practices and crop rotation sequences will be un-interrupted. Measurements of runoff quality and quantity, crop growth and yield, and soil physical and chemical properties will be continued. Beginning in 1998, soil and crop spatial variability will be characterized using grid sampling and/or yield monitor sampling. Computer simulation modeling of various aspects of the field plot hydrology will be initiated. Results. This information will be used to develop water conservation practices and to assess, more accurately, the environmental impact of agricultural practices.
R. Louis Baumhardt, Soil Scientist, USDA-ARS, Bushland, TX
Problem. Winter wheat and grain sorghum are well-adapted dryland crops for the semiarid southern Great Plains, but water use efficiencies often are low due to high evaporative losses when these crops are grown in a rotation, which involves 10-11 months of fallow after each crop. Also, a fixed cropping system involving these crops prevents growing alternative crops when enough soil water becomes available soon after harvest of either crop. Objective. To determine if crops other than wheat or grain sorghum could be successfully grown on dryland when adequate soil water becomes available at times not suitable for growing wheat or grain sorghum. Treatments. Cropping systems include continuous cropping of wheat, grain sorghum, and triticale, and rotations of wheat and grain sorghum, wheat and fall canola, wheat and spring canola, and grain sorghum and kenaf. Alternative crops are planted in some plots whenever soil water contents become adequate and the growing season is suitable. These `opportunity' crops include forage sorghum, millet, oat, and pinto bean as well as grain sorghum and wheat. All systems involve reduced tillage (tillage- herbicide combinations) to control weeds, except no-tillage (only herbicides) is used for the wheat- grain sorghum rotation. Results. Yields for wheat, grain sorghum, and triticale grown continuously have been poor, whereas yields for wheat and sorghum grown in rotation have been greater in most cases. Spring canola yields have been fair, but no yields have been obtained for fall canola. Forage sorghum, millet, and oats have performed well as opportunity crops, which were planted when adequate soil water became available at a time not suitable for planting grain sorghum or wheat. The protein content of kenaf at early growth stages is over 30% and is near 20% in the fall. Some kenaf cultivars are suitable as feed for animals; others are more suitable for paper making.
Paul W. Unger, Soil Scientist, USDA-ARS
Problem. Contracts covering some of the CRP land in the region have expired or will expire soon, depending on renewal of the contracts, and there is interest in what methods are suitable for returning the CRP grassland to cropland if this is to occur. Objective. A study was started on a farmer's field near Wildorado (about 7 km west of the Research Laboratory) in late 1994 to determine effects of different ways to prepare CRP land for winter wheat and grain sorghum production. Also to determine what effects the treatments have on soil conditions. Procedure. Treatments include moldboard, disk, and sweep tillage without prior grass removal or with grass removed by mowing and baling; grass burning before disk or sweep tillage; and no-tillage with grass retained or removed. Results. Because of little rain or snow before planting grain sorghum and little rain during the growing season in 1995, grain yields were low with all treatments and averaged only about 390 kg/ha. Poor weed control (bindweed) contributed to the low yields. The highest yield was 770 kg/ha for a treatment involving sweep tillage followed by herbicides to control weeds. Severe plant water stress resulted in poor grass and weed control with herbicides on no-tillage plots. Sorghum was not planted in 1996 because of the drought. The 1995-1996 wheat yields were extremely low because of the drought. Wheat yields averaged 2040 kg/ha in 1997, with no differences due to tillage treatments. The yields, however, were greater where nitrogen was applied at 67 or 134 kg/ha than where no nitrogen was applied. Grain sorghum yields in 1997 averaged 3850 kg/ha, with yields being higher with no-tillage than with other treatments in most cases for which the yields were similar. Application of nitrogen fertilizer did not affect sorghum yields in most cases. At 2 to 3 years after terminating the CRP grass, the potential for soil erosion by wind is low on plots for all tillage treatments.
Paul W. Unger and Ordie R. Jones (Collaborator), Soil Scientists , USDA-ARS
Cooperators -- John Janhsen, Farmer. USDA-Natural Resource Conservation Service (NRCS) personnel and USDA-Farm Services Agency (FSA) personnel
Problem. Soil water storage and erosion control improve with increases in the amount of crop residues retained on the soil surface, but residue production by dryland crops such as winter wheat and grain sorghum often is low. If more residues could be `carried over' from one crop to the next and a `buildup' of residues could be obtained when these crops are grown in rotation, improved water conservation and erosion control should occur. Objectives. To determine if wheat and grain sorghum varieties differ with regard to amounts of residues carried over from one crop to the next when they are grown in a rotation in a no-tillage cropping system. Treatments. Five wheat varieties and five grain sorghum hybrids are `cross planted' in the study. Residue amounts remaining from each previous crop are determined at planting and harvest of each crop. Soil water contents and crop yields are determined also.
Paul W. Unger, Soil Scientist, USDA-ARS
Problem. No-tillage is a drastic departure from conventional tillage, and there are concerns whether this type of farming can be maintained on dryland without developing problems that could adversely affect soil conditions and crop yields. Objectives. To determine the effect of long-term use of no-tillage on wheat and sorghum yields and on soil physical and chemical properties. Treatments. Winter wheat and grain sorghum have been grown in rotation under no-tillage conditions on three fields since 1979. Weeds and volunteer crop plants are controlled with herbicides. Soil water contents at planting and harvest and yields are determined for each crop. Soil conditions are determined periodically. Results. Since 1985, grain yields have averaged 2850 kg/ha for wheat and 4400 kg/ha for grain sorghum, both at 13.5% grain moisture content. Soil conditions have not been adversely affected by use of no-tillage when compared with soil conditions on other dryland field areas.
Paul W. Unger, Soil Scientist , USDA-ARS
Problem. Waste paper accounts for much of the material disposed of in landfills. Landfill space, however, is limited in many areas and some landfills are no longer available for waste paper disposal. Therefore, alternative means of disposal are needed. Applying waste paper to agricultural land is being considered. If applied to land, it must not result in a trashy appearance and it should provide benefits to land owners or operators. One such means is to use paper pellets, which are being used as a mulch for landscaping in some areas. Surface-applied paper pellets reduced soil water evaporation under laboratory conditions. Objective. A study was started in 1995 to determine whether surface-applied paper pellets would increase soil water storage under field conditions. Such application would increase the amount of organic materials on the surface, which should add to the benefits obtained from crop residues. It should also increase soil organic matter contents, which should improve soil conditions. Procedure. Paper pellets are applied after wheat harvest in a wheat-grain sorghum rotation study. Pellets are applied at rates of 0 (check treatment), 5000, 10000, or 15000 kg/ha to no-tillage plots where wheat resides are retained or removed by raking and to sweep tillage plots where wheat resides are retained or removed by raking. Effects of the pellets on soil water storage and on grain sorghum growth and yield are being determined.
Paul W. Unger, Soil Scientist, USDA-ARS
Problem. Soil organic C content, recognized as an indicator of soil quality, declines with continued cropping when grasslands are converted to cropland. When croplands are planted to grass, it is generally assumed that soil C contents will increase, which would enhance C sequestration in the soil and improve soil quality. Some croplands in the region have been planted to grass under Conservation Reserve, Soil Bank, and Great Plains Programs. Land adjacent to such program lands has remained in crop production and/or in native grass. The effect of different management practices on soil C and related properties, however, is not well documented. Objectives. To determine the effect of long- and short-term cropping practices and differently-managed grasslands on soil physical, chemical, and biological properties that are related to crop productivity, soil quality, production sustainability, and the environment. Procedure. Sites at which cropland, native grassland, and one or more replanted grassland areas are adjacent to each other will be sampled to determine a number of soil properties, including texture, organic carbon content, aggregation, density, and water relations.
Paul W. Unger, Steven R. Evett, R. Louis Baumhardt, and Thanh H. Dao, Soil Scientists, and Judy A. Tolk, Plant Physiologist, USDA-ARS, Bushland; Fred B. Pringle, Soil Scientist, USDA- NRCS, Amarillo; and Clay Robinson, Associate Professor, and B. A. Stewart, Distinguished Professor of Soil Science and Director, Dryland Agriculture Institute, WTAMU, Canyon
Beef cattle feeding operations can potentially have adverse effects on water and air quality. Although beef cattle feedyards produce large quantities of manure which can be used as fertilizer for crops, the value of manure as a fertilizer is limited because of it's low nitrogen:phosphorus (N:P) ratio and other factors. The objectives of this research are to develop nutritional and management regimens that decrease nutrient losses to the environment and increase the fertilizer value of manure from confined beef cattle feeding operations. In vivo and in vitro trials were conducted to determine the effects of sorghum planting density and processing method on P utilization by ruminants. Row spacing and processing method appeared to affect P retention when diets contained 60% concentrate but not when diets contained 90% concentrate. Two trials were conducted to determine the effects of oscillating dietary crude protein concentrations at 24- hour or 48-hour intervals on nutrient digestion and retention in sheep fed 90% concentrate diets. Results indicated that oscillating dietary protein concentrations (10 vs 15% CP) at 48-hour intervals could improve N utilization, however, the effects were partially dependent upon the ruminal degradability of the dietary crude protein. One study is in progress to evaluate internal markers that can be used to determine the digestibility of high-concentrate feedlot diets under typical feeding conditions. In vitro studies are in progress to determine the bioavailability of P in various feed ingredients and to determine the effects of low ruminal pH on utilization of phytate-P by ruminants. This information would make it possible to formulate rations that contain decreased amounts of total P, and thus would decrease the amounts of P excreted to the environment. A laboratory scale system is being used to evaluate different methods (soil amendments, etc.) to decrease ammonia, nitrogen, carbon, and sulfur emissions from the surface of feedlots. Successful completion will provide information to determine soil amendment and other methods to use in larger scale studies to decrease N, C, and S losses from feedlot surfaces and thus potentially decrease odor, greenhouse gas, and dust emissions from feedlots. Initial tests indicated that additions of lime to the soil increased ammonia losses by 10 to 20 fold, whereas additions of alum could decrease ammonia losses by as much as 80%. Results of these studies will help to develop nutritional and management regimens that decrease excretion of N and P by beef cattle and decrease ammonia emissions from confined beef cattle feeding operations. This will decrease potential adverse effects on water and air quality and increase the N:P ratio of feedlot manure.
N. Andy Cole, Research Animal Scientist, USDA-ARS
Background: Animal production in the Southwest of the United States occurs primarily in concentrated animal feeding operations (CAFO). Large numbers of animals are gathered in a relatively small land area where huge volumes of nutrients in feeds are imported to support the finishing of million head of cattle, in particular about 6.9 million in the Southern High Plains in 1997. Sophisticated manure collection and storage systems are developed to dispose of the estimated 61 million tons produced each year across the country. Approximately 6.3 million tons are produced annually in feedlots in the panhandles of Texas and Oklahoma, and in eastern New Mexico. This concentration and type of confined production system creates an imbalance in nutrient distribution and has resulted in intensive land applications of manure in the immediate vicinity of the feedlots because of the high cost of transporting such material for distances greater than a 25-mile radius. Otherwise, the manure is placed in stockpiles that dot the region. Cumulatively, the nutrient content of the manure in the U.S. represents approximately 17, 24, and 64% of the quantities of N, P, and K used in crop production. On the average, feedlot manure contains about 2% nitrogen, 0.2% phosphorus, and 1.5% potassium. Therefore, it is estimated that the manure produced each year in the Southern High Plains potentially contains about 250 million lbs of N, 58 million lbs of P2O5, and 228 million lbs of K2O. These nutrients could be beneficially recycled back into crop production. Composting of manure results in 30 to 50% reduction in mass and a material more uniform in nutrient composition that is more transportable. Mineralization of labile carbon and nitrogen constituents results in a more stable remaining N fraction that are not easily usable by plants or by other soil organisms to derive further growth energy. Carbon mineralization also results in an enrichment of the P concentration in the composted material. A rather uniform material is obtained and sold as an organic soil amendment that has very different nutrient release characteristics than the manure of origin. Objectives: Offsite land application of animal liquid and solid manure is the major avenue for disposing of the large volume of manure produced by CAFOs. Land application requires a fundamental knowledge of the waste-soil- plant-environment systems and efficient management skills to minimize contamination risks to air, land, and water resources. An accurate assessment of the manure or compost composition and their mineralization characteristics is needed. This information is critical to arrive at optimal loading rates for land treatment of stockpiled and composted manure and the optimal use of these organic sources of plant nutrients for crop production without impairing the quality of the environment. Land application research studies were undertaken to (i) quantify and predict nutrient mineralization from manure and waste-amended soils, and (ii) develop physical and biochemical modifications of P availability and application strategies to reduce the ecological risks of surface applications of animal manure in the design a total manure management system. Materials & Methods: In long-term field studies, equivalent N applications of stockpiled feedlot manure, composted manure, and inorganic fertilizers, ranging from 75 to 250 kg(N)/ha and from 20 to 150 kg(P)/ha were made on leveled terraces. The fields were managed using either no-tillage or stubble-mulch tillage practices. Grain sorghum (Sorghum bicolor L.) and winter wheat (Triticum aestivum) were planted following nutrient applications in May 1996. Results: Our preliminary results showed that sorghum and winter wheat responded positively to added nutrients from all nutrient sources. Plant responses were affected by highly variable waste characteristics. Although manure is considered an organic amendment, the release of P is of interest because of the high proportion of inorganic P in cattle feedlot wastes and the stabilization of manure nutrients upon composting. Water- soluble P readily desorbed from both manures when incubated alone or with a Torrertic Paleustoll and an Aridic Paleustalf. Phosphorus release followed a double-exponential decay model, showing a large P pool with an initial fast release rate for both stockpiled and composted manure. A second smaller pool has a slow release rate. No apparent increased stability of P occurred in composted manure.
Because of environmental pressures, our land application research efforts are also devoted to develop chemical research approaches to modification of P availability and application strategies to reduce the ecological risks of land applications of animal manure. Traditionally, manure applications are made to meet the N requirements of the plant. A narrow N/P ratio exists in animal manure that ranges from 1:2.5 to 1:8, depending upon animal species. The imbalance creates a high loading of P, which progressively accumulate in the soil when applications are made to fulfill the nitrogen demands of the crop. The high loading of P in excess of plant needs may affect micronutrient nutrition and may result in offsite movement. Non-hazardous industrial by-product such as alum or calcium, aluminum, iron-rich compounds such as caliche, or fly ash, a coal combustion by-product generated by Southwest Public Service electric power plants were used to induce changes in P extractability in manures. Caliche, alum, and fly ash decreased water-extractable P in stockpiled manure by 20, 60, and 85% and by 50, 80, and 90% in composted manure at 0.1g/g rate of amendment. Plant-extractable P concentrations were also drastically reduced in stockpiled and composted manure with increasing amendment rates. Co- mingling these amendments with feedlot manure widened the effective N:P ratio of treated manure by reducing bioavailable P by a factor ranging from 1.5 to 18. The amendments may account for an additional 0.1 to 0.2 pH unit change and an increase of 0.1 dS/m in EC that is biologically insignificant in soils. The joint uses of animal and mineral by-products at the 1:10 rate of amendment should reduce the stockpiling of both by-products where they co-exist within short hauling distances locally and across the nation in general. The loading rates of manure on different soil types and landscapes can revert back to N requirements of the vegetation without causing environmental problems.
Using the controlled solubility approach, we are studying the effects of matching nutrient requirements, nitrogen, to actual nutrient contents of the animal manures rather than a total loading of manure that has a highly variable composition. These treatments are being contrasted to applications based on phosphorus needs of the sorghum and wheat crops, and those based on P needs with manure and manure supplemented with inorganic N fertilizers. Rainfall simulation studies are conducted in conjunction with the above studies to determine the susceptibility of nutrients from land applications of manure and compost to overland flow and offsite transport of manure nutrients. The research will provide guidelines for addressing regulatory limits of P loading and issues of soluble P and the forms in which P moves in the environment.
Thanh H. Dao, Soil Scientist, USDA-ARS, Bushland, TX
Wind turbines that produce electricity are used with standard electric pumps and motors (submersible pumps with 3-phase motors). Flow rates vary from 10 gpm (38 L/min) for a 1 kW wind turbine to 100 gpm(385 L/min) for a 10 kW system at a pumping head of 100 ft (30 m) and a wind speed of 22 mph (10 m/s). A 1.5 kW (10 ft) wind turbine was used to replace a worn out 60 year old 10 ft Dempster mechanical windmill on a 300 ft well (240 ft static water level) here at Bushland. The piston pump, 2" steel drop pipe, and sucker rod of the mechanical system was replaced by a 3-phase 230 Volt 1.5 hp motor, 19-stage centrifugal pump, and 1" poly pipe of the wind-electric system. From October '97 to June '98 enough water was provided to satisfy the water requirements of 80 head of cattle. However, the low winds, high temperatures, and drought conditions we've experienced in July this year have required us to haul water for these cattle. If a rancher in this area decides to buy this wind-electric system, it is recommended that he either have a storage tank capable of supplying his cattle with water for 5 days, have a backup 4.5 kW 3-phase 230 Volt gasoline generator, or be prepared to haul water for his cattle in July/August. The 850 Watt (8 ft) wind-electric system can be used to replace a 8 ft mechanical windmill if a tower is used for the wind-electric system which is twice as high as that for the mechanical windmill. A completely new 850 Watt wind-electric system will cost about 20% less than a completely new mechanical windmill system.
R. Nolan Clark, Laboratory Director, Ron Davis, Agricultural Engineer, Brian Vick, Mechanical Engineer, USDA-ARS, Bushland; and Shitao Ling, Research Technician, WTAMU- AEI, Canyon/Bushland
Solar photovoltaic panels are used to produce DC electricity that is used directly to power electric pumps. Diaphragm pumps and DC electric motors are used to pump water from small systems (less than 400 Watts) and submersible pumps with AC electric motors are used on larger systems (greater than 500 W). An inverter is used to convert the DC output of photovoltaic panels to AC electricity to power the submersible motors on the larger systems. The DC diaphragm pumps have been pumping water for over 2.5 years now with an Availability close to 100%. A rancher with a 100 ft well and 25 cattle to water, this is the best stand-alone renewable energy system to use. However, the lifetime of the diaphragm pump will significantly be shortened if the pumping depth is much deeper. The AC solar water pumping system has also bee
n very reliable and for a rancher with 100 head of cattle and a 150 ft well, who has a good solar resource but a poor wind resource, this is the best stand-alone renewable energy system to use.
R. Nolan Clark, Laboratory Director; Ron Davis, Agricultural Engineer, and Brian Vick, Mechanical Engineer, USDA-ARS; and Shitao Ling, Research Technician, WTAMU-AEI, Canyon/Bushland