Search

Dryland crops rely on precipitation as their exclusive water source, but storm water runoff decreases the amount available for biomass and grain production. Management practices that minimize runoff often increase the opportunity time for infiltration and improve precipitation storage as soil water. Our objective was to quantify storm water runoff from contour farmed terraces in relation to precipitation and field characteristics and then relate runoff to soil water at planting and yields of wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench] grown in a 3‐yr wheat–sorghum–fallow (WSF) rotation. Comparisons of long‐term (1984–2010) runoff observations indicated mean annual runoff for both uncropped periods of the WSF rotation were significantly greater with no‐tillage (NT) than stubble‐mulch (SM) tillage. By contrast, soil loss was greater for SM than NT because residue cover of undisturbed NT soil was less subject to entrainment and loss. Increasing field slope from 1.2 to 1.8% produced greater fallow runoff, which is water lost from dryland production. Nevertheless, soil water was significantly greater with NT, which reduced evaporative losses during fallow compared with SM. Long‐term wheat yields exhibited no difference due to tillage, but NT grain sorghum yields increased significantly over SM tillage. The data show that while runoff with NT was typically greater than SM, profile soil water at planting was also greater for NT and increased grain sorghum yields significantly. We conclude that decreasing evaporative water losses with NT residues is the primary factor affecting soil water conservation. [ABSTRACT FROM AUTHOR]

Dryland crops rely on precipitation as their exclusive water source, but storm water runoff decreases the amount available for biomass and grain production. Management practices that minimize runoff often increase the opportunity time for infiltration and improve precipitation storage as soil water. Our objective was to quantify storm water runoff from contour farmed terraces in relation to precipitation and field characteristics and then relate runoff to soil water at planting and yields of wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench] grown in a 3‐yr wheat–sorghum–fallow (WSF) rotation. Comparisons of long‐term (1984–2010) runoff observations indicated mean annual runoff for both uncropped periods of the WSF rotation were significantly greater with no‐tillage (NT) than stubble‐mulch (SM) tillage. By contrast, soil loss was greater for SM than NT because residue cover of undisturbed NT soil was less subject to entrainment and loss. Increasing field slope from 1.2 to 1.8% produced greater fallow runoff, which is water lost from dryland production. Nevertheless, soil water was significantly greater with NT, which reduced evaporative losses during fallow compared with SM. Long‐term wheat yields exhibited no difference due to tillage, but NT grain sorghum yields increased significantly over SM tillage. The data show that while runoff with NT was typically greater than SM, profile soil water at planting was also greater for NT and increased grain sorghum yields significantly. We conclude that decreasing evaporative water losses with NT residues is the primary factor affecting soil water conservation. [ABSTRACT FROM AUTHOR]

Depletion of the High plains Aquifer that supplies irrigation water for the semiarid Southern great plains may necessitate dryland production of crops like wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] using the wheat-sorghum-fallow (WSF) rotation. Reduced crop productivity without irrigation can be offset by intensifying the WSF rotation with cattle (Bos taurus) grazing. Biomass removal and soil trampling without tillage, however, may reduce rain infiltration and storage during fallow that increases with no-tillage (NT) over stubble-mulch (SM) tillage. Our objective was to quantify grazing and tillage effects on infiltration, sediment transport, and aggregate stability during fallow periods after sorghum and wheat. Using a split plot randomized complete block design, we compared wet aggregate size distribution of a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll; 0.0-0.05 m) and sediment yield in runoff of simulated rain during the fallow-like idle period after wheat and the sorghum fallow. Sediment concentration and yield for both fallows were numerically larger (>40%) with grazing. Sediment concentration from SM tillage increased significantly over NT for either fallow, but soil loss differed only for wheat fallow. Mean final infiltration rate (IRf) and amount (IA60) did not differ significantly with grazing during either fallow, but IA60 was usually 20% lower for grazed than for ungrazed paddocks. Because SM tillage after grazed wheat significantly (P < 0.01) increased IRf and IA60 over NT, occasional SM tillage to disrupt compaction from trampling may increase water conservation for dryland cropping systems combining grazing with NT residue management. [ABSTRACT FROM AUTHOR]

High grazing pressure can lead to soil erosion in pastures, causing increased sediment delivery to waterways. The objectives of this research were to evaluate the impact of grazing management and buffer strips on soil erosion by assessing soil physical properties, hydrology, and sediment loads from pastures fertilized with broiler litter. Field studies were conducted for 12 yr on 15 small watersheds. Five management strategies were evaluated: hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with a buffer strip (RB), and rotationally grazed with a fenced riparian buffer (RBR). Broiler litter was applied every year at a rate of 5.6 Mg ha-1. Bulk density and penetration resistance were highest for CG watersheds. Runoff volumes, sediment concentrations, and loads were lowest for the H and RBR treatments and highest for CG. Average runoff amounts were 48, 84, 77, 60, and 81 mm yr-1 for the H, R, RB, RBR, and CG treatments, respectively. Annual average sediment loads were 25, 30, 58, 71, and 110 kg ha-1 for H, RBR, R, RB, and CG, respectively. The Revised Universal Soil Loss Equation, Version 2 was reasonably effective at predicting soil loss for the R, RB, and RBR treatments, but it greatly overpredicted soil loss from the CG and H treatments. Converting a pasture to a hay field or using rotational grazing in conjunction with a fenced riparian buffer appear to be effective options for reducing soil erosion and runoff to waterways from pasture soils. [ABSTRACT FROM AUTHOR]

Equatorial Pacific sea surface temperature anomalies can cause a systematic El Niño-Southern Oscillation (ENSO) coupling with the atmosphere to produce predictable weather patterns in much of North America. Adapting irrigation strategies for drought-tolerant crops like cotton (Gossypium hirsutum L.) to exploit forecast climatic conditions represents one potential innovative technique for managing the declining Ogallala Aquifer beneath the US Southern High Plains. The crop simulation model GOSSYM was used with ENSO phase-specific weather records during 1959 to 2000 at Bushland, TX, to estimate lint yields of cotton emerging on three dates from soil at 50 or 75% available water content for all possible combinations of irrigation durations (0, 4, 6, 8, and 10 wk) and rates (2.5, 3.75, and 5.0 mm d-1). From those data, our objective was to compare partial center pivot deficit irrigation strategies that optimize calculated net cotton lint yield in relation to ENSO phase, initial soil water content, and emergence date. Although phase classification in June was inconsistent with maturing fall phases, the most accurately classified La Niña phase had limited rain that reduced lint yields compared with wetter Neutral and El Niño phases. During La Niña phase conditions, irrigation strategies that focused fixed water resources on smaller areas were better suited to increase net yield than spreading water across larger areas. Alternatively, during less predictable and wetter Neutral and El Niño phases, irrigation strategies that spread water increased net lint yield over focused applications except when both initial soil water and irrigation amount were limiting. [ABSTRACT FROM AUTHOR]

The declining High Plains or Ogallala Aquifer motivates U.S. producers to optimize water use and yield of drought-tolerant crops like cotton [Gossypium hirsutum (L.)]. Systematic sea surface temperature anomalies (SSTA) drive the El Niño-Southern Oscillation (ENSO), resulting in predictable weather patterns in North America that could be exploited by irrigation strategies. Our objective was to compare cotton yield response to irrigation as altered by La Niña, Neutral, or El Niño phases for the Texas High Plains. We used actual 1959 to 2000 weather records with the simulation model GOSSYM to estimate lint yields for three progressively later emergence dates under 50 or 75% initial soil water conditions and all combinations of irrigation duration (0, 4, 6, 8, and 10 wk) and rate (2.5, 3.75,and 5.0 mm d-1). Simulated lint yield and its ratio to evapotranspiration generally decreased with emergence delays and increased with increasing irrigation amount and application rate. Growing season precipitation varied with ENSO phase, but April to June phase classification was inconsistent with fall conditions except for La Niña. Compared with yield estimates for Neutral and El Niño phases, limited rain during La Niña years reduced lint yields from 5 to 30% when initial soil water was 75 and 50%. Yield increased with increasing irrigation rate and duration during drier La Niña growing seasons, but irrigation benefits decreased during Neutral and El Niño years having greater precipitation. Early ENSO based extended forecasts for La Niña related consistently to irrigation effects on yield and could determine application strategies. [ABSTRACT FROM AUTHOR]

Rhizome production has been transferred from wild germplasm of Lotus corniculatus L. (broadleafed birdsfoot trefoil) into domesticated germplasm to produce `ARS-2620' and `ARS-2424' (a L. corniculatus × L. uliginosus hybrid). The objective of this study was to determine if field environments in the United States differing in latitude affect rhizome expression in genotypes of ARS-2620 and ARS-2424. Ramets of rhizomatous genotypes of ARS-2620 and ARS-2424, and nonrhizomatous `Norcen' were planted at seven locations in late July and August 1999. At five locations in 2000 and 2001, dormant plants were hand-dug in late autumn or winter. Traits measured were mean crown-plus-root mass, crown circumference, and percentage survival for all entries, and rhizome mass for the two rhizomatous entries. Significant (P ≤ 0.001) location X genotype effects were observed for all traits in 2000, hut only for percentage survival in 2001. In 2001, the effect of locations was significant for all traits (P ≤ 0.001), but genotype effects were significant (P ≤ 0.001) only for crown circumference and percentage survival. The rhizomatous entries were larger in circumference and had a greater crown-plus-root mass than Noreen. Rhizomes appeared to be beneficial to plant survival and plant growth, but rhizomes did not assure performance or survival, as we did not identify a genotype that performed well across locations. High plant mortality and extensive tissue necrosis caused by root and crown-rot complex reduced overall plant performance and rhizome expression and masked the interpretive value of the data from the five locations. Plants grown in Logan, UT, were notable for their large size and rhizome production relative to the other locations, and as having advantageous, but undefined, environmental conditions beneficial to the performance of rhizomatous birdsfoot trefoil. [ABSTRACT FROM AUTHOR]

Mechanisms involved in mineral stress tolerance of cool-season grasses infected by Neotyphodium spp. endophytes are not known. In a controlled-environment experiment, two genotypes (DN2 and DN4) of tall fescue (Festuca arundinacea Schreb.) infected (E+) with their naturally occurring strains of N. coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, and their non-infected (E-) isolines were cultivated in nutrient solution at two phosphorus (P) levels of 31 mg P dm-3 (P+) and 0.31 mg P dm-3 (P-) for 3 weeks. Diameters of lateral roots, root hair length, and distance between root hairs were recorded using a digital image analysis system (Dage 72S CCD camera controlled by a Power MacIntosh 7200/120PC compatible computer equipped with an AG-5 frame grabber board and NIH-Image). Irrespective of tall fescue genotype and P level in nutrient solution, E+ plants had roots with a smaller diameter (16 %) than E- plants. In response to P deficiency, root diameter of E+ plants declined by 11 % and root hair length increased by 17 % when compared to E- plants. Altered root diameter and root hair length might be one of the mineral stress tolerance mechanisms in endophyte-infected tall fescue. [ABSTRACT FROM AUTHOR]