ArkValley Irrigation Grant SOW - Laserfiche WebLink

Home Browse Search

of the Arkansas River and has a shallow water table varying from 8 to 22 feet as seen in static well levels. "Perched" water table areas have been created by over-irrigation in some areas of the property causing excessive salting of the soils. Because of the excessive salting of these soils, salt tolerant grasses and legumes will be compared to grasses and legumes presently being grown or recommended for these type soils. Birdsfoot trefoil and cicer milkvetch are more salt tolerant legumes that will be included in the grass/legume mixtures. Grasses could include switchgrass, bluestem, wheatgrass, bromegrass, orchardgrass, creeping foxtail and wildrye. Nine full-circle and two half-circle center pivot systems are located on the property. Full and lor partial- circle pivots will be selected that will represent different soil types or salinity conditions. as possible. The pumps being used to supply these pivots were tested to determine pumping capacity and pump efficiency. Crops and/or grass and legume mixtures planted on these soils will be determined by the soil type or salinity levels shown by the soils and salinity mapping. Also. the quality of the water being pumped to each of the demonstration sites will be tested for irrigation suitability and will determine the method of water application used by LEPA system. Drag hoses, low drift nozzles (LDN) or quad-sprays will be used to apply the water depending on the salinity level. Where possible, higher quality water will be applied to the alfalfa and the lower quality water will be applied to the more salt-tolerant grass-legume and/or grass mixtures. II. Methods and Evaluation Procedures The demonstration area was re-mapped for soil type in the summer of 1993 by the SCS. Salinity mapping will be done during the demonstration period when arrangements can be made for the equipment. Soils remapping was done to give more detailed information for the project. Alfalfa will be planted in the fall oU995 or 1996 on the pivot with the better soil type. Soil type and saliIiitywill determine thegtasses ancrlor legume mixe,s planted on the remaining,pivots ill'The demonstration area. Four grass mixtures .an.d/or gi:iss~legumemixtures will be planted with the more salt-tolerant mixtures on the more saline soils."''fhese mJxtUtes will be planted in grazing cells and forage cages will be harvested to determine forage yield and quality while visual evaluations will be made of othh forage characteristics such as recovery, grazing tolerance and species preference.' These areas will be mechanically harvested and/or grazed. Some of the mixtures may be mechanically harvested first cutting and grazed the remainder of the season. Soil tests will be taken before the 1995, 1996 and 1997 and after the 1997 growing seasons to determine nutrie~t needs and use. 'Sub-surface nitrogen and' salinity will be determined by sampling from the two, lM"ee"'llffu'tour foot le~i;. ".,Nitrogen and s~iiirity 101ding will be calculated from this sampling by the Cneinistry Departinent<it the University of Southern Colorado. Water quality samples will be taken from wells supplying water to the demonstration sites under thec,eJ!ter pivot systems and the surge irrigation system. A compI~ttirrigation water suitability analysis 'will be ccTh'di'iCt~a 6hthese samples by the Chemistry Department atfue University of Southern Colorado and will include conductivity,lotal dissolved solids (TrJS) , s~lts and nitrate-nitrogen. These wells will also be monitored and analyzed fot agricultural chemicals by the Colorado Health Department as part of a basin wide program. Water-use efficiency will be determined. in part. by resistance (gypsum) blocks or dielectric constant measurement placed in the crops at varying depth to "monitor available soil moisture. Measurements will' be'taken in the soil to a four-foot depth as this is usually the effective root zone for alfalfa and grasses. 8