Runoff and Sediment from Row-crop, Row-crop with Grass Strips, Pasture, and Forest Watersheds

Comparisons of runoff and sediment loss from row-crop with and without riparian buffers, pasture and grass filter strips are limited. Effects of precipitation, landuse and buffer condition on runoff and sediment loss were examined from 1997 to 1999 in eight watersheds with varying proportions of row-crop, pasture, riparian buffers and grass filter strips. Runoff volume and sediment mass from row-crop watersheds were inversely related to the percentage of forest and pasture cover. Forest (n = 2), pasture (n = 3), row-crop (n = 2) and a row-crop watershed with grass filter strips (RC-GFS) had 3‑yr mean runoff of 939, 1,560, 3,434 and 1,175 m3 ha‑1 yr‑1, respectively. Runoff was greater from all landuses in a year when precipitation was 36% above normal (1998). The largest single runoff event from each watershed accounted for 11 to 25% of its total runoff. Forest, pasture, row-crop and RC-GFS watersheds lost 1,017, 1,241, 3,679 and 2,129 kg ha‑1 yr‑1 of sediment, respectively. In 1998, the RC-GFS watershed lost more sediment than row-crop watersheds and had less runoff and sediment loss in years with normal or below normal precipitation. Row-crop watersheds with 55% pasture reduced runoff and sediment loss by 55 and 66%, respectively, compared to row-crop watersheds. During 90% of the runoff events, more soil was lost from row-crop watersheds than pasture or forest watersheds. Results suggest that 3‑4 m grass filter strips, maintenance of 55% or more pasture/CRP land within row-crop watersheds and intact riparian buffers significantly reduce runoff and sediment losses from row-crop watersheds.Les études comparant les volumes de ruissellement et les charges sédimentaires de bassins versants avec cultures en lignes et pâturages avec et sans zones tampons et bandes riveraines sont peu nombreuses. Les effets des précipitations, de l’occupation du sol et des conditions des zones tampons sur le ruissellement et les charges sédimentaires ont été analysés de 1997 à 1999 pour huit bassins versants comportant en proportions diverses des cultures en lignes, des pâturages, des zones tampons et des bandes riveraines. Il a été montré que les volumes de ruissellement et les charges sédimentaires pour les bassins versants avec cultures en lignes étaient inversement proportionnels aux pourcentages de forêt et de pâturages présents sur ces bassins. Les moyennes mesurées sur trois ans des volumes de ruissellement des bassins versants de type forestier, avec pâturages, avec cultures en lignes et avec cultures en lignes et bandes riveraines (RC‑GFS) sont de 939, 1 560, 3 434 et 1 175 m3/ha/an respectivement. Les volumes de ruissellement mesurés pendant une année pour toutes les occupations du territoire ont été plus grands lorsque les précipitations ont été supérieures de 36 % à la normale (1998). L’événement générant le volume de ruissellement le plus important à survenir sur chaque bassin versant génère à lui seul de 11 % à 25 % du volume de ruissellement total mesuré. Les charges sédimentaires pour les bassins versants forestiers, avec pâturages, avec cultures en lignes et RC‑GFS ont été respectivement de 1 017, 1 241, 3 679, et 2 129 kg/ha/an respectivement. En 1998, les charges sédimentaires des bassins versants RC‑GFS ont été plus importantes que les bassins avec cultures en lignes alors que les volumes de ruissellement et les charges sédimentaires sur ces mêmes bassins ont été plus petits lors d’années avec des précipitations égales ou inférieures à la moyenne. Les bassins avec cultures en lignes et comportant 55 % de pâturages permettent une réduction de l’ordre de 55 % des volumes de ruissellement et de 66 % des charges sédimentaires lorsque comparés aux bassins avec cultures en lignes. Les charges sédimentaires mesurées à l’exutoire des bassins avec cultures en lignes ont été plus élevées pour 90 % des événements que celles issues des bassins avec pâturages ou forestiers. Les résultats de cette étude montrent que des bandes riveraines de 3 à 4 m, le maintien de plus de 55 % du territoire sous forme de pâturages/CRP pour des bassins avec cultures en lignes et la présence de bandes riveraines permettent de réduire de façon significative les volumes de ruissellement et les charges sédimentaires des bassins versants avec cultures en lignes

Disruption of Yarrowia lipolytica TPS1 Gene Encoding Trehalose-6-P Synthase Does Not Affect Growth in Glucose but Impairs Growth at High Temperature

We have cloned the Yarrowia lipolytica TPS1 gene encoding trehalose-6-P synthase by complementation of the lack of growth in glucose of a Saccharomyces cerevisiae tps1 mutant. Disruption of YlTPS1 could only be achieved with a cassette placed in the 3′half of its coding region due to the overlap of its sequence with the promoter of the essential gene YlTFC1. The Yltps1 mutant grew in glucose although the Y. lipolytica hexokinase is extremely sensitive to inhibition by trehalose-6-P. The presence of a glucokinase, insensitive to trehalose-6-P, that constitutes about 80% of the glucose phosphorylating capacity during growth in glucose may account for the growth phenotype. Trehalose content was below 1 nmol/mg dry weight in Y. lipolytica, but it increased in strains expressing YlTPS1 under the control of the YlTEF1promoter or with a disruption of YALI0D15598 encoding a putative trehalase. mRNA levels of YlTPS1 were low and did not respond to thermal stresses, but that of YlTPS2 (YALI0D14476) and YlTPS3 (YALI0E31086) increased 4 and 6 times, repectively, by heat treatment. Disruption of YlTPS1 drastically slowed growth at 35°C. Homozygous Yltps1 diploids showed a decreased sporulation frequency that was ascribed to the low level of YALI0D20966 mRNA an homolog of the S. cerevisiae MCK1 which encodes a protein kinase that activates early meiotic gene expression

Apparent Soil Electrical Conductivity Used to Determine Soil Phosphorus Variability in Poultry Litter-Amended Pastures

The objectives of this research were to determine the relationship between soil apparent electrical conductivity (ECa) and soil P distribution, and to compare the effectiveness of noncontact mobile electromagnetic induction (EM) and direct contact methods for relating ECa to soil P. Studies were conducted at two locations in Southwest Missouri on a longterm forage fertility plot site and three 1 to 1.5 ha sites within beef cattle pasture fields, all having received long-term poultry litter applications. For the long-term plot site, both the direct contact ECa sensor deep reading and the EM-38 (Geonics) sensor in the shallow mode had significant positive correlations with soil test Bray-1 P at both the 0 to 5 and 5 to 15 cm sampling depths. Significant spatial variation in soluble, soil test Bray-1 and total P were observed by landscape position within pasture fields. In general, soil ECa was not significantly correlated with soluble, soil test Bray-1 and total P at each individual pasture site, but when data was combined over all three sites, significant relationships were observed between ECa measured by the EM-38 sensor and soil soluble P, soil test Bray-1 P and total P, especially when the vertical (deep) mode was used. The difference in performance of the two sensors between the two studies was attributed to the proportion of coarse fragments contained in the soils and soil water content. These results suggest that soil ECa measurements may provide some useful information for evaluating spatial variation in soil P due to manure applications. However, further research is needed to assess the processes and factors affecting this relationship before it can be recommended for use for improved soil P management in individual farm fields with varying environmental conditions and management practices

Synchrotron microtomographic quantification of geometrical soil pore characteristics affected by compaction

Soil compaction degrades soil structure and affects water, heat, and gas exchange as well as root penetration and crop production. The objective of this study was to use X-ray computed microtomography (CMT) techniques to compare differences in geometrical soil pore parameters as influenced by compaction of two different aggregate size classes. Sieved (diameter  &lt;  2 mm and  &lt;  0.5 mm) and repacked (1.51 and 1.72 Mg m⁻³) Hamra soil cores of 5 by 5 mm (average porosities were 0.44 and 0.35) were imaged at 9.6 &mu;m resolution at the Argonne Advanced Photon Source (synchrotron facility) using X-ray CMT. Images of 58.9 mm³ volume were analyzed using 3-Dimensional Medial Axis (3-DMA) software. Geometrical characteristics of the spatial distributions of pore structures (pore radii, volume, connectivity, path length, and tortuosity) were numerically investigated. Results show that the coordination number (CN) distribution and path length (PL) measured from the medial axis were reasonably fit by exponential relationships P(CN)  =  10^−CN∕Co and P(PL)  =  10^−PL∕PLo, respectively, where Co and PLo are the corresponding characteristic constants. Compaction reduced porosity, average pore size, number of pores, and characteristic constants. The average pore radii (63.7 and 61 µm; <i>p</i>  &lt;  0.04), largest pore volume (1.58 and 0.58 mm³; <i>p</i>  =  0.06), number of pores (55 and 50; <i>p</i>  =  0.09), and characteristic coordination number (3.74 and 3.94; <i>p</i>  =  0.02) were significantly different between the low-density than the high-density treatment. Aggregate size also influenced measured geometrical pore parameters. This analytical technique provides a tool for assessing changes in soil pores that affect hydraulic properties and thereby provides information to assist in assessment of soil management systems

Phosphorus and nitrogen losses in relation to forest, pasture and row-crop land use and precipitation distribution in the midwest usa

Little information is available comparing the influence of land use and precipitation on the control of phosphorus (P) and nitrogen (N) losses from agricultural watersheds in claypan soils. Eight watersheds with varying proportions of row-crop, pasture, forest, and grass filter strip condition were examined for three consecutive years to evaluate effects of land use and precipitation on P and N losses from row-cropped watersheds. Total P (TP) and total N (TN) losses were inversely related to the percentage of forest and pasture cover. Forest (n=2), pasture (n=3), row-crop (n=2), and row-crop grass filter strip (n=1) land use types had mean annual TP losses of 0.43, 0.90, 3.82 and 1.30 kg•ha-1•yr-1, respectively and mean annual TN losses of 2.02, 4.34, 29.25 and 12.31 kg•ha-1•yr-1, respectively. During the 3-year study, the respective land use types lost 0.36, 0.64, 13.99 and 7.26 kg NO3-N•ha-1•yr-1. Runoff events on row-cropped watersheds resulted in significantly greater TP, TN, and NO3-N losses than those from pastured and forested watersheds. Stream nitrate-N concentrations averaged 0.39, 0.50, and 2.56 mg•L-1 for forest, pasture, and row-crop land use types, respectively. During the study, 136% of the long-term average precipitation in 1998 caused significant nutrient losses in all watershed categories and the variability within a land use type was larger than in years with below long-term rainfall. The study results emphasize the incorporation of perennial vegetation such as vegetative buffers, grass/conservation reserve program areas, and grass filter strips or other perennial vegetation as a long-term option for effective control of nutrient losses in runoff from agricultural watersheds.Il y a peu d’information disponible sur les liens entre l’occupation des sols, la précipitation et le contrôle des pertes en phosphore (P) et en azote (N) des bassins versants ayant des sols aux horizons argileux. Pour cette étude, huit bassins caractérisés par différentes proportions de culture à interlignes, pâturage, forêt et conditions de bandes enherbées, ont été suivis sur une période de trois ans. Les pertes en P total (TP) et N total (TN) étaient inversement reliées au pourcentage d’occupation en forêt et en pâturage. Les occupations forêt (n=2), pâturage (n=3), cultures à interligne sans (n=2) et avec bandes enherbées (n=1), avaient respectivement des pertes annuelles moyennes de TP de 0,43, 0,90, 3,82, et 1,30 kg•ha-1•année-1 et de TN de 2,02, 4,34, 29,25 et 12,31 kg•ha-1•année-1. Au cours de cette étude de trois ans, les pertes en azote nitrate étaient respectivement de 0,36, 0,64, 13,99, et 7,26 kg N-NO3•ha-1•année-1. Les pertes résultant des événements de ruissellement sur les bassins de cultures à interlignes étaient plus considérables que celles sur les bassins caractérisés par la forêt et les pâturages. Les concentrations en azote nitrate dans les cours d’eau alimentés par les occupations forêt, pâturage et cultures à interlignes étaient respectivement de 0,39, 0,50, et 2,56 mg N-NO3•L-1. Au cours de l’étude, et ce en comparaison avec les années ayant reçu des précipitations inférieures à la moyenne à long terme, les précipitations de 1998 (136% de la moyenne à long terme) ont produit plus de pertes dans tous les types de bassins ainsi que de plus grandes variabilités pour chaque occupation. Les résultats de cette étude illustrent que l’intégration de couvertures végétales pérennes, telles que les bandes enherbées, les aires protégées enherbées et les voies enherbées ou autre végétation pérenne, représente une option à long terme pour le contrôle efficace des pertes en nutriments par ruissellement dans les bassins agricoles

Microbial community diversity and composition across a gradient of soil acidity in spruce-fir forests of the southern Appalachian Mountains

Anthropogenic deposition of sulfur (S) and nitrogen (N) contributes substantially to soil acidity in some forest regions and hence studies have focused on modeling and quantifying depositions in landscapes. The resulting acidity can change the soil chemical balance, nutrient availability, microbial communities, and at a broader scale, ecosystem functioning. In this study, a 16S PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) approach was used to measure the bacterial diversity and identify the dominant bacterial species along a soil acidity gradient in high elevation spruce-fir forests of Great Smoky Mountains National Park (GSMNP). Sample sites were selected based upon modeled S deposition class (6-14, 15-23, 23-32, and 33-41kgha -1). Collected soils were analyzed for pH, C, N, Ca, Al, S, CEC, and base saturation. Average soil pH in the O, A, and B horizons were 3.6, 3.6 and 3.9, respectively. Modeled S deposition was found to be an unreliable predictor of soil S content as well as most other soil chemical properties. DGGE profiles of bacterial partial 16S rRNA genes revealed minor differences in bacterial diversity while communities were similar, dominated by members of phylum Actinobacteria, Acidobacteria, Planctomycetes, Proteobacteria, and Chloroflexi. Dominance of acidophilic bacterial species, often found in highly acidic environment such as acid-mine drainage and sphagnum bogs, suggests that the poorly buffered soils that are endemic to southern Appalachian spruce-fir forests are saturated with acidity. Our results suggest that stricter air quality standards have not resulted in shift to less acid-tolerant bacteria. © 2012 Elsevier B.V