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Storage and release functions of western U.S. traditional river valley irrigation systems may counteract early and rapid spring river runoff associated with climate variation. Along the Rio Grande in northern New Mexico, we instrumented a 20-km-long irrigated valley to measure water balance components from 2005 to 2007. Hydrologic processes of the system were incorporated into a system dynamics model to test scenarios of changed water use. Of river water diverted into an earthen irrigation canal system, some was consumed by crop evapotranspiration (7.4%), the rest returned to the fiver as surface return flow (59.3%) and shallow groundwater return flow that originated as seepage from canals (12.1%) and fields (21.2%). The modeled simulations showed that the coupled surface water irrigation system and shallow aquifer act together to store water underground and then release it to the river, effectively retransmitting river flow until later in the year. Water use conversion to nonirrigation purposes and reduced seepage from canals and fields will likely result in higher spring runoff and lower fall and winter river flow. DOI: 10.1061/(ASCE)IR.1943-4774.0000265 CE Database subject headings: Aquifers; Hydrologic models; Hydrogeology; Irrigation systems; Surface water; Groundwater; Groundwater recharge; Rio Grande. Author keywords: River-aquifer interaction; Hydrology; Hydrologic models; Hydrogeology; Irrigation systems; Surface water; Groundwater; Groundwater recharge; Rio Grande.

Irrigated pastures form a significant component of agriculture in the irrigated steppe of the southern Rocky Mountains, USA. Information is limited, however, describing performance of grazed binary perennial cool-season grass--legume mixtures in the region. Established monoculture tall fescue [Festuca arundinacea Schreb. = Lolium arundinaceum (Schreb.) S.J. Darbyshirel + 134 kg N [ha.sup.-1] (MONO) and tall fescue mixed with alfalfa (Medicago sativa L.) (ALF/TF), birdsfoot trefoil (Lotus corniculatus L.) (BFT/TF), ricer milkvetch (Astragalus cicer L.) (CM/TF), or kura clover (Trifolium ambiguum M.B.) (KC/TF) at New Mexico State University's Sustainable Agriculture Science Center at Alcalde were subjected to two grazing frequencies (grazed monthly or bimonthly mid-May to mid-September) from 1998 to 2000. Grass, legume, and combined dry matter (DM) yields were measured in May 1998 to 2001. A year x grazing frequency x pasture interaction for legume DM yield was moderated by a lack of effect in grass DM yield, leaving a year x pasture interaction for combined DM yield in which MONO, ALF/TF, and CM/TF increased linearly across years and cubic trends were exhibited by ALF/TF and KC/TE Despite the cubic trend of KC/TF, it and BFT/TF had the most uniform yield distribution across years became of nonsignificant linear effects. Annual combined DM yield averaged 2.21, 3.90, 2.43, 1.93, and 3.03 Mg [ha.sup.-1] for MONO, ALF/TF, BFT/TF, CMfFF, and KC/TF, respectively, from 1998 to 2001 (5% LSD 0.77). Kura clover-tall fescue offers an alternative to alfalfa-tall fescue for long-term pastures in the irrigated steppe of the southern Rocky Mountains., RECENTLY, there has been increased interest in maximizing utilization of irrigated pastures in the western USA because of changes in federal land policies on public grazing lands and the desire [...]

An improved understanding of ecohydrologic connections is critical for improving land management decisions in water-scarce regions of the western United States. For this study, conducted in a semiarid (358 mm) rangeland location in central Oregon, we evaluated precipitation-interception-soil moisture dynamics at the plot scale and characterized surface water and groundwater relations across the landscape including areas with and without western juniper (Juniperus occidentalis). Results from this study show that juniper woodlands intercepted up to 46% of total precipitation, altering soil moisture distribution under the canopy and in the interspace. Results indicate that precipitation reaching the ground can rapidly percolate through the soil profile and into the shallow aquifer, and that strong hydrologic connections between surface and groundwater components exist during winter precipitation and snowmelt runoff seasons. Greater streamflow and springflow rates were observed in the treated watershed when compared to the untreated. Streamflow rates up to 1020 L min-1 and springflow rates peaking 190 L min-1 were observed in the watershed where juniper was removed 13 years ago. In the untreated watershed, streamflow rates peaked at 687 L min-1 and springflow rates peaked at 110 L min-1. Results contribute to improved natural resource management through a better understanding of the biophysical connections occurring in rangeland ecosystems and the role that woody vegetation encroachment may have on altering the hydrology of the site. [ABSTRACT FROM AUTHOR]

Better understanding of surface water (SW) and groundwater (GW) interactions and water balances has become indispensable for water management decisions. This study sought to characterize SW-GW interactions in three crop fields located in three different irrigated valleys in northern New Mexico by (1) estimating deep percolation (DP) below the root zone in flood-irrigated crop fields; and (2) characterizing shallow aquifer response to inputs from DP associated with irrigation. Detailed measurements of irrigation water application, soil water content fluctuations, crop field runoff, and weather data were used in the water budget calculations for each field. Shallow wells were used to monitor groundwater level response to DP inputs. The amount of DP was positively and significantly related to the total amount of irrigation water applied for the Rio Hondo and Alcalde sites, but not for the El Rito site. The average irrigation event DP using data for the complete irrigation season at each of the three sites was 77.0 mm at El Rito, 54.5 mm at Alcalde and 53.1 mm at Rio Hondo. Groundwater level rise compared to pre-irrigation event water levels ranged from 3 to 1870 mm, and was influenced by differences in irrigation practices between sites. Crop evapotranspiration estimates averaged across irrigation events were highest in Rio Hondo (22.9 mm), followed by El Rito (14.4 mm) and Alcalde (10.4 mm). Results from this study indicate there are strong surface water-groundwater connections in traditionally irrigated systems of northern New Mexico, connections that may be employed to better manage groundwater recharge and river flow. [ABSTRACT FROM AUTHOR]

Traditional cultures in arid landscapes of the southwestern United States and northern Mexico developed irrigation systems to irrigate floodplain valleys along streams and rivers. Many of these traditional irrigation systems, referred to as acequias, continue to be used today. Population growth in the region is creating pressures to convert agricultural land and irrigation water to urban and other uses. Unique hydrologic features of the acequia systems suggest that, beyond providing crop irrigation, they may provide additional valuable hydrologic, riparian, and agroecosystem functions worth maintaining. We investigated in detail the seepage and the groundwater response to seepage from a traditional acequia irrigation ditch along the Rio Grande in north-central New Mexico. We found that 16% of ditch flow seeps into the ditch bed and banks. Groundwater levels near the ditch and midway between the ditch and the river rise 1 m or more within three to four weeks following the start of the irrigation season. The elevated groundwater table produced by ditch and field seepage is sustained until late summer when groundwater levels again drop. The seepage that provides this annual groundwater recharge also sustains riparian vegetation along the main ditch and side ditches. In light of our hydrologic analysis, we considered seepage-supported riparian areas and their ecological functions including aquatic habitat, terrestrial habitat, and water quality effects. Ace quia hydrology plays an important role in contributing to an ecologically healthy, agriculturally productive, and community-sustaining floodplain agroecosystem. [ABSTRACT FROM AUTHOR]

This investigation was part of a project to evaluate green manure forage legumes as relay intercrops for sweet corn (Zea mays L.) and chile (Capsicum annuum L.) in north-central New Mexico. The study was carried out under irrigated conditions in 1994 on a Fruitland sandy loam (coarse-loamy, mixed, calcareous, mesic Typic Torriorthent) to evaluate the 15N recovery by forage sorghum (Sorghum bicolor L.] Moench) and soil after the incorporation of lSN-labeled alfalfa Medicago sativa L. Nitro') or hairy vetch (Vicia villosa Roth. 'Madison'). Two application rates of alfalfa (2.7 or 4.0 Mg dry matter ha[sup -1]) or hairy vetch herbage (3.2 or 6.4 Mg dry matter ha[sup -1]), were incorporated into soil microplots. Additional treatments consisting of 56, 112, and 168 kg N ha[sup -1] (as urea) were used to compare soil inorganic N concentrations with those released from the legumes. Nitrogen-15 recovery by sorghum tops was 16% of the [sup 15]N applied, in two harvests. Of this, 80% was recovered at the first harvest. In soil, [sup 15]N recoveries were 50 and 3% of the input at the 0-0.3 and 0.3-0.6 m depths, respectively. Maximum inorganic N concentrations were found 14 d after amendment application. At the end of the growing season, inorganic N concentrations in all treatments were essentially the same as the background (8 mg N kg[sup -1]). The low [sup 15]N recoveries by crop plus soil and inorganic N concentrations in soil at the end of the season suggest that about 12% and 35-58% of the N applied as green manure was lost from the system for alfalfa and hairy vetch, respectively. [ABSTRACT FROM AUTHOR]

Forage legumes in crop rotations are often used to supply N for succeeding crops. However, the residual effect of forage legume green manures for second crops has not been thoroughly investigated in high desert regions of the Southwestern United States. The objective of this study was to evaluate the [sup 15]N recovery by a second subsequent crop (oat [Avena sativa L.]) and soil from microplots amended with [sup 15]N-labeled alfalfa (Medicago sativa L. 'Nitro') and hairy vetch (Vicia villosa Roth 'Madison'). In 1994, two application rates of each legume were incorporated into 1 m² microplots and forage sorghum (Sorghum bicolor [L.] Moench) was used to evaluate the [sup 15]N recovery. Aboveground residues were removed from microplots immediately after each of the two sorghum harvests. In 1995, the [sup 15]N recovery by the oat crop was determined. Nitrogen-15 recovery by oat averaged 3% of applied as green manure. Of this, 95% was found in tops and 5% in roots. Averaged across application rates, oat recovery of [sup 15]N was 63% greater in treatments amended with alfalfa than with hairy vetch. Green manures did not affect the total N concentration of oat parts. Most of the residual [sup 15]N was found in soil at the 0-0.3 m depth at the end of the oat season. The percent of [sup 15]N recovery by soil in plots amended with alfalfa was 238% higher than with hairy vetch. Green manures applied in 1994 had little residual effect on the N nutrition of oat. [ABSTRACT FROM AUTHOR]

Improving the soil quality in arid agro-ecosystems requires a greater understanding of how the time-of-sampling and management affect the soil measurements. We evaluated the selected soil quality indicators on samples collected at a 0–0.15 m depth, and at various sampling dates of the year, corresponding to the fall of 2015, winter of 2015/2016, spring of 2016, and the summer of 2016. The three crop management systems sampled included alfalfa (Medicago sativa), upland cotton (Gossypium hirsutum), and pecan (Carya illinoinensis). The soil properties measured included the wet aggregate stability (WAS), mean weight diameter of dry aggregates (MWD), dry aggregates greater than 2 mm (AGG >2 mm), dry aggregates less than 0.25 mm (AGG <0.25 mm), available water capacity (AWC), soil organic matter (SOM), permanganate oxidizable carbon (POXC), soil bulk density (BD), soil electrical conductivity (EC), pH, nitrate-nitrogen (NO3-N), extractable potassium (K), extractable phosphorus (P), calcium (Ca), magnesium (Mg), sodium adsorption ratio (SAR), and micronutrients (zinc, iron, copper, and manganese). Out of the 21 soil measurements, 15 varied significantly with the time-of-sampling within a year, although there were no consistent trends in variability. However, only a few measurements differed significantly with the crop management practices tested. Wet aggregate stability, MWD, AWC, and BD were significantly higher in the summer, while POXC and SOM were significantly higher in the fall and winter, respectively. Soil quality indicators such as NO3-N, K, and P decreased significantly during the spring. This study shows that the seasonal variability of the soil measurements can be significant in the arid agro-ecosystems, with the magnitude of variation depending on the measurement type. The soil managers in the region need to account for this variability, in order to be able to assess the changes in the soil quality. Also, because of the variability that can occur across the different sampling dates within a year, it is advisable to sample during the same period every year, for a consistent interpretation of the directional changes of the soil quality indicators. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) stover is used globally as winter feed for livestock but the nutritive value is low, requiring supplementation. A 2-year randomized complete block study with three replicates at New Mexico State University's Alcalde Sustainable Agriculture Science Center compared sweet maize (Zea mays var. rugosa; maize-alone) with sweet maize relay intercropped with oat (Avena sativa L.; maize-oat) or turnip (Brassica rapa L.; maize-turnip). Relay intercropping had no effect (p > 0.05) on sweet maize stover dry matter (DM) yield and there was no difference in aboveground biomass DM yield of the intercropped species. Turnip aboveground biomass had greater crude protein concentration and 48-h in vitro dry matter disappearance (IVDMD) than oat aboveground biomass. Relay intercropping with turnip improved sweet maize stover IVDMD (443, 439, and 515 g IVDMD kg−1 for maize-alone, maize-oat, and maize-turnip, respectively, p < 0.0001). Intercropping increased animal gains compared to maize-alone (0.36, 0.52, and 0.59 kg/day for maize-alone, maize-oat, and maize-turnip, respectively, p < 0.02), likely due to provision of additional crude protein. Relay intercropping oat or turnip into sweet maize is viable for improving sweet maize stover for fall forage. In addition turnip, specifically, had a positive effect on stover nutritive value. [ABSTRACT FROM AUTHOR]