Mesic Typic Argiudoll Research Articles

Long-term tillage impacts on soil organic matter components and related properties on a Typic Argiudoll

Soil organic matter affects a number of soil processes and properties. A better understanding of soil-profile distribution of organic matter components and related soil properties under long-term tillage systems is thus needed. The objective of this study was to evaluate the impacts of 33 years no-till (NT), double disk (DD), chisel (CH), and plow tillage (PT) under corn (Zea mays L.)–soybean (Glycine max L.) rotation on soil organic C (SOC), particulate organic matter (POM), pH, and wet aggregate stability to 100cm soil depth on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) in eastern NE. After 33 years, NT and DD management increased SOC by 1.2 times and mean weight diameter (MWD) of aggregates by 2 times compared with CH and PT at the 0–10cm depth. At the 0–20cm, NT had 1.1 times higher SOC concentration than CH and PT. When compared with data collected 24 years prior to this study, SOC at the 0–20cm increased by 12.5% across NT, DD, and CH and by 2.7% for PT. No-till had 5 times higher total POM concentration than PT, 4.7 times higher than CH, and 2.4 times higher than DD at the 0–10cm depth. However, at the 10–20cm, PT had higher POM than other tillage systems, which is most probably due to mixing and burial of residues at the bottom of the plow layer. Soil pH did not differ among tillage treatments at the 0–10cm, but it differed in this order: PT>CH>DD>NT at the 10–20cm and PT=CH=DD>NT at the 20–40cm depth. The lower pH under NT, DD, and CH in deeper soil depths may be due to the limited or no lime mixing in these systems compared with PT. When compared with data (pH 5) collected 33 years prior to this study, soil pH increased by 0.9 in NT, 1.4 in DD, 1.5 in CH, and 1.9 units in PT at 0–20cm depth, probably due to surface application and incorporation of lime. Overall, 33 years of NT increased near-surface soil organic matter components and soil aggregation compared with the PT.

Using Corn and Soybean Yield History to Predict Subfield Yield Response

Site‐specific management often uses past grain yield data to delineate management zones in a field. Questions remain about the type and amount of data required to classify subfields into management zones. The objective of this study was to test the hypothesis that yield history could predict yield patterns of subfields. Past grain yield data were collected from two experiments conducted on a Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll) near Arlington, WI. Experiment 1 included 26 yr and Exp. 2 included 10 yr of data for continuous corn (Zea mays L.), continuous soybean (Glycine max L. Merr.), and rotated corn–soybean in conventional‐till and no‐till. Average yield range among subfields within a year was 1.51 to 3.67 Mg ha−1 for corn and 0.54 to 0.81 Mg ha−1 for soybean. Across both experiments, spatial yield standard deviation of corn was 0.68 to 1.69 Mg ha−1; temporal yield standard deviation was 1.87 to 2.73 Mg ha−1. Spatial yield standard deviation of soybean was 0.24 to 0.37 Mg ha−1; temporal yield standard deviation was 0.56 to 0.85 Mg ha−1. The length of time required to detect yield differences among subfields was 2 to 18 yr and to detect consistent subfield yield patterns was 4 to 24 yr. High corn yield predicted high soybean yield and low corn yield predicted low soybean yield in 87% of subfields. Since temporal yield variation was greater than spatial yield variation, classifying subfields into management zones for input prescriptions remains challenging.

Soil Carbon Accumulation under Switchgrass Barriers

The benefits of grass barriers or hedges for reducing offsite transport of non‐point‐source water pollutants from croplands are well recognized, but their ancillary benefits on soil properties have received less attention. We studied the 15‐yr cumulative effects of narrow and perennial switchgrass (Panicum virgatum L.) barriers on soil organic C (SOC), total N, particulate organic matter (POM), and associated soil structural properties as compared with the cropped area on an Aksarben silty clay loam (fine, smectitic, mesic Typic Argiudoll) with 5.4% slope in eastern Nebraska. Five switchgrass barriers were established in 1998 at ∼38‐m intervals parallel to the crop rows in a field under a conventional tillage and no‐till grain sorghum [Sorghum bicolor (L.) Moench]–soybean [Glycine max (L.) Merr.]–corn (Zea mays L.) rotation. Compared with the cropped area, switchgrass barriers accumulated about 0.85 Mg ha−1 yr−1 of SOC and 80 kg ha−1 yr−1 of total soil N at the 0 to 15 cm soil depth. Switchgrass barriers also increased coarse POM by 60%. Mean weight diameter of water‐stable aggregates increased by 70% at 0 to 15 cm and by 40% at 15 to 60 cm, indicating that switchgrass barriers improved soil aggregation at deeper depths. Large (4.75–8 mm) macroaggregates under switchgrass barriers contained 30% more SOC than those under the cropped area. Switchgrass‐induced changes in SOC concentration were positively associated with aggregate stability (r = 0.89***) and porosity (r = 0.47*). Overall, switchgrass barriers integrated with intensively managed agroecosystems can increase the SOC pool and improve soil structural properties.

Speedzone has Potential for Postemergence Goosegrass Control in Perennial Ryegrass and Creeping Bentgrass

Goosegrass (Eleusine indica [L.] Gaertn.) is a C4 summer annual distributed throughout the transition zone and can be problematic in sports fields and lawns, but more often is problematic in golf course greens and tees where preemergence (PRE) herbicides are rarely used because of frequent reseeding in-season. The postemergence (POST) herbicides monosodium methanearsonate (MSMA), fenoxaprop-ethyl, or sulfentrazone are commonly used to control goosegrass on golf courses. However, MSMA has recently lost most of its labeled uses (EPA, 2013), while fenoxaprop-ethyl is restricted from use at mowing heights less than 0.25 inch (Anonymous, 2005) and sulfentrazone is restricted from use on golf course greens or tees (Anonymous, 2012). In July 2011, control of goosegrass was reported when Speedzone was applied to golf course tees to control summer annual broadleaves in Omaha, NE (J. Calentine, personal communication, 2011). This was further reported anecdotally at multiple sites in Nebraska later that summer. Therefore, we began our studies in 2012 with the objectives of confirming if Speedzone has potential for goosegrass control and if so, what application rates and intervals are most effective while still safe on cool-season turfgrasses. The experiment was conducted in 2012 and 2013 at the John Seaton Anderson Turf Research Facility near Mead, NE. In October of 2011, sand-based thinly cut sod of Kentucky bluegrass (Poa pratensis) and perennial ryegrass (Lolium perenne) from a tee on a local goosegrass-infested golf course was moved to the experimental site, distributed evenly and tilled into the top inch of soil. Soil type on the experimental area was Tomek silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) with pH 6.9 and 2.7% organic matter. A perennial ryegrass blend was seeded at 3 lbs/1000 sq ft in April 2012 to establish a thin turf cover. Following establishment, the area was irrigated to prevent water stress, mowed at 0.625 inch, and not fertilized to minimize turf competition with goosegrass. Before goosegrass germination and initiating treatments, glyphosate was applied Published in Applied Turfgrass Science DOI 10.2134/ATS-2014-0025-BR © 2014 American Society of Agronomy and Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711

Soil quality improvement under an ecologically based farming system in northwest Missouri

AbstractEcologically based farming conserves and improves the soil resource and protects environmental quality by using organic or natural resources without the application of synthetic chemicals. Soil quality assessment indicates the ability of management systems to optimize soil productivity and to maintain its structural and biological integrity. Our objective was to evaluate the effect of ecologically based management on biochemical characteristics of soil [soil quality indicators (SQI)] as an assessment of soil quality. The study was conducted on an ecologically based farming enterprise established on gently sloping soils of Sharpsburg silt loam (fine montmorillonitic, mesic Typic Argiudolls) in Clay County, Missouri, which was previously under conventional corn and soybean production. The transition to organic farming began in 1995, which included a primary management strategy to restore soil organic matter consisting of the establishment of native prairie plants and the application of composted vegetative residues and litter from horse and laying hen operations. Soils were collected at 0–10cm depths from sites under organic production (orchard and vegetable), managed prairie/pasture and from adjacent unmanaged fields during 2003–2008 for soil quality assessment. Soil organic carbon (SOC) and water-stable soil aggregates were considerably increased by up to 60 and 72%, respectively, in organic production sites compared with tilled cropland by the fifth year of assessment. Organically managed systems and restored prairie sites significantly increased (P<0.05) soil enzyme activities compared with unmanaged grass and tilled cropland. For example, dehydrogenase and glucosaminidase activities increased by 60 and 73%, respectively, under organic vegetables compared with tilled cropland. Soil enzyme activities were significantly correlated with SOC content (rvalues up to 0.90,P<0.001). The results of the soil quality assessment suggest that ecologically based management successfully restored biological activity of silt loam soils previously under intensive conventional agriculture. The system practiced at the study sites illustrates how resources internal to the farm (i.e., composts) can be used to manage soil productivity.

Scale-of-measurement effects on phosphorus in runoff from cropland

Phosphorus (P) risk loss assessment tools such as P indices are usually developed from small-plot scale data showing the relationships between various site and management variables and runoff P losses. Little information is available on how small-plot runoff composition compares with field-scale measurements. This study was conducted to compare runoff volume and composition measurements at the field scale with those obtained from natural runoff at the small-plot (1 m2 [10.8 ft2]) scale. Sediment, dissolved P, and total P in natural runoff from small plots located in two fields (7.2 and 12 ha [17.8 and 29.6 ac]) were compared with similar measurements from the fields over an 18-month period. Runoff from small-plot rainfall simulations in both fields was also analyzed for P and sediment. The fields, cropped with either corn (Zea mays L.) or alfalfa (Medicago sativa L) interseeded with bromegrass (Bromus inermis), were located on a Tama silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll) in southwest Wisconsin (42°42′ N, 90°22′W). Statistical analysis using repeated measures showed no significant differences between the two scales of measurements for dissolved P concentrations in runoff. Total P concentrations in small-plot runoff were greater than those in field runoff. Runoff volume and dissolved P concentrations were greater in winter than in summer, but summer runoff had higher sediment concentrations. Small plots had greater cumulative runoff volumes per unit area in both seasons compared to the fields. The dissolved P concentration relationships between the two scales of measurement for individual runoff events were very good in the corn field (r2 = 0.90) but not in the alfalfa field (r2 = 0.09). Sediment P enrichment ratios varied by crop and were similar in the small-plot and field runoff. Cumulative runoff-dissolved P concentrations were strongly related (r2 = 0.95) to average soil-test P at both scales. The agreement of small-plot and field runoff-dissolved P concentrations during the 18-month measurement period supports use of small-plot data in P loss risk assessment tools.

Long‐Term Continuous Corn and Nitrogen Fertilizer Effects on Productivity and Soil Properties

There are uncertainties about the sustainability of long‐term monoculture and N fertilizer use in corn (Zea mays L.) production. This paper examines the effects of 50 yr (1958–2007) of continuous corn and N fertilizer use on corn yield, N use efficiency, soil pH, and organic matter content. Corn was harvested for grain with residues returned annually since 1958 on a Plano silt loam soil (fine‐silty, mixed, superactive, mesic Typic Argiudolls) near Arlington, WI (43°18’ N; 89°21’ W). The experimental design includes three N fertilizer rates (currently 0, 140, and 280 kg N ha−1) and two lime treatments (imposed in 1985) with four replications. Soil pH and organic matter content were measured periodically during the experiment. Average corn yields in N fertilized treatments increased dramatically (100%) over time with some of the highest yields occurring in the most recent years. Apparent N use efficiency (kg grain kg−1 N fertilizer) also increased over time, thus higher yields in recent years have not required greater N fertilizer use. Results suggest that both hybrid genetic improvement and improved management techniques contributed to the long‐term yield gain. Soil organic matter content was maintained or increased with long‐term N additions, and since 1985, lime treatments increased yields in 14 of 23 yr. Increasing productivity and N use efficiency along with stable or increasing soil organic matter suggest that long‐term continuous corn and N fertilizer use are sustainable practices. No evidence of a decline in productivity from long‐term corn monoculture or N fertilizer use was detected.

Effects of Gypsum Addition on Solubility of Nutrients in Soil Amended With Peat

It is widely accepted that the accumulation of gypsum in gypsiferous soils results in very low fertility, even with application of fertilizers and organic amendments. The objectives were to investigate, in laboratory experiments, the effect of gypsum on the solubility of 13 nutrients and how amending the soil with organic peat moss may mitigate the impact of gypsum on nutrients and soil fertility. A 100-g sample of gypsum-free soil (Sharpsburg Fine, montmorillonitic, mesic Typic Argiudolls) was treated with increasing amounts of gypsum (0, 1, 5, 10, 15, 20, 30, and 50 g), then water was added to the mixtures to reach 50% of the water saturation capacity. Another set of soil/gypsum mixtures received 5-g peat to study the effect of peat application. All mixtures were incubated at 32 degrees C for 15 weeks. After incubation, the concentration of water-soluble nutrients was measured. In general, the addition of gypsum increased the solubility of N, K, Ca, Mg, Mn, Cl, and S, whereas it decreased the solubility of P, Na, Fe, Cu, Zn, and B. The application of peat increased the solubility of all nutrients investigated, except for N and S. Chemical reactions and mechanisms were applied to interpret the effects of both gypsum and peat treatments on nutrient solubility and their relationship to soil fertility and crop production. The application of peat improved the solubility of most nutrients and proved to be useful as an amendment for gypsum-rich soils and increases its productivity.

Source Water Effects on Runoff Amount and Phosphorus Concentration under Simulated Rainfall

Frequently, well water is used instead of rainwater to perform rainfall simulations to study P and soil loss in cropping systems. This study was conducted to determine whether the source water used in simulated rainfall studies affects runoff amount and P and sediment concentrations. Rainfall simulation and natural runoff studies were conducted in a corn (Zea mays L.) and alfalfa (Medicago sativa L.) field on a Tama silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudoll) in spring and fall 2004. No significant differences in runoff composition were found between the well and deionized (DI) source waters in the spring rainfall simulation study in corn. The fall rain simulation in alfalfa showed significantly higher runoff volumes and dissolved reactive P (DRP) concentrations with DI water than with well water. Soil water‐extractable P (WEP) measurements showed that rain and DI water extracted similar amounts of P, while well water extracted less P. Using the same source waters in WEP procedures and in rainfall simulations yielded good relationships (r2 = 0.73) between simulated rain runoff DRP and soil WEP concentrations. Natural runoff DRP concentrations measured in the same field treatments as those used in the simulated rainfall studies were much greater than those found in simulated rainfall runoff, but the relative field treatment effects on runoff P concentrations were the same. These results emphasize that simulated rainfall data can provide a relative comparison of treatment effects on runoff composition, but results from simulated rainfall experiments are not likely to duplicate natural runoff composition, regardless of the source water used.

Canopy Structure and Neutral Detergent Fiber Differences among Temperate Perennial Grasses

Intake of animals grazing grass pasture is in part influenced by canopy density. Our objective was to determine the vertical distribution of dry matter and neutral detergent fiber (NDF) within temperate perennial grass swards. The study was conducted in 2004 and 2005 on a Plano silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudolls). When leaf height of each grass reached 25 cm in spring, summer, and fall, canopy layers were harvested from 20 to 25, 15 to 20, and 10 to 15 cm. Differences in canopy density were usually not significant when precipitation was below normal. With abundant spring precipitation, quackgrass [Elymus repens (L.) Gould] had greater upper canopy density (1.9 mg dry matter [DM] cm−3) than any of the other grasses studied. Grasses typically grazed at shorter heights such as bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) had greater density in the lower canopy layer (1.0–1.3 g DM kg−1). While soft‐leaf tall fescue (Festuca arundinacea Schreb.), reed canarygrass (Phalaris arundinacea L.), and meadow fescue (Festuca pratensis Huds.) had lower density in the upper canopy than timothy (Phleum pratense L.) and quackgrass in the spring, the reverse was true in the summer. Herbage NDF of grasses generally increased from the upper to lower canopy layer (mean difference of 50 g kg−1); perennial ryegrass and meadow fescue often had the lowest NDF throughout the canopy (range of 392–452 and 418–469 g kg−1, respectively). Pasture intake may benefit from a diverse species composition because animals can graze a mixture having optimum density and NDF throughout the canopy.

Dairy Manure Type, Application Rate, and Frequency Impact Plants and Soils

The impacts of dairy rations on manure chemistry, manure N mineralization in soils, and crop N uptake have been evaluated after single manure applications. No information is available on these impacts when manure is applied to soils at different rates and frequencies. Manure from lactating dairy cows (Bos taurus) fed three diets differing in crude protein (CP) content were applied to a Plano (fine‐silty, mixed, superactive, mesic Typic Argiudolls) and a Rosholt (coarse‐loamy, mixed, superactive, frigid Haplic Glossudalfs) soil at two application rates (225 or 450 kg total N ha−1) and three application frequencies (once, twice, or thrice). Oat (Avena sativa L.), sorghum [Sorghum bicolor (L.) Moench] and sorghum ratoon were grown in succession during a 170‐d period. Plant responses to manure from different CP diets were much less than responses due to soil type and manure application rate and frequency. Manure N uptake efficiency by plants was greatest for manure derived from a low‐CP diet than manure derived from either the medium‐ or high‐CP diets. Manure application rate and frequency increased NO3 levels in oat and sorghum shoots, which if used as forage could have detrimental impacts on dairy cow health. No significant differences were measured in second‐crop (sorghum) yield or N uptake due to a previous manure application at either N application rate. Third‐crop (sorghum ratoon) yield and N uptake were significantly increased, however, due to previous manure applications, but only in pots that received two manure applications at the high rate. Longer term, repeated applications of dairy manure derived from different diets at lower rates could provide more pronounced impacts on plants and soils than those observed during this relatively short‐term greenhouse study.

Nodulating and Non‐Nodulating Soybean Rotation Influence on Soil Nitrate‐Nitrogen and Water, and Sorghum Yield

Soybean [Glycine max (L.) Merr.] rotation has been shown to enhance grain sorghum [Sorghum bicolor (L.) Moench] growth and yield due in part to N contribution. Sorghum grain and stover yield, yield components, soil water and soil NO3–N were measured in a long‐term rotation study in 2003 and 2004 on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudoll). The objectives were to separate biologically fixed N from other rotation effects on sorghum grain and stover yields, and to relate yield to yield components, soil NO3–N and water contents. The cropping sequences were continuous grain sorghum, and sorghum rotated with non‐nodulating or nodulating soybean. Soil amendment treatments consisted of control (zero), manure (17–25 Mg dry matter ha−1 yr−1), and N (41 kg ha−1 for soybean and 84 kg ha−1 yr−1 for sorghum). Cropping sequence × soil amendment interaction effects were found for most parameters measured. High soil NO3–N following soybean rotation and from amendment application promoted plant growth leading to low soil water content at anthesis, and increased kernel weight, grain and stover yield. Rotation with non‐nodulating soybean without soil amendment increased grain yield by 2.6 to 3.0 Mg ha−1 and stover yield by 1.5 to 1.8 Mg ha−1 over continuous sorghum without soil amendment. Rotation with nodulating soybean further increased grain yield by 1.7 to 1.8 Mg ha−1 and stover yield by 0.6 to 0.9 Mg ha−1. Biologically fixed N effects accounted for only 35 to 41% of enhanced sorghum yield due to crop rotation with soybean. Soil NO3–N during vegetative growth, plant height, soil water content at anthesis and kernel weight were the most important parameters related to sorghum grain yield across cropping sequences and soil amendments.

Crop Rotation and Soil Amendment Alters Sorghum Grain Quality

ABSTRACTSoybean [Glycine max (L.) Merr.] rotation enhances grain sorghum [Sorghum bicolor (L.) Moench] yield, but influence on grain quality has not been measured. The objective was to determine the effect of cropping sequence (CS) and soil amendment (SA) on grain yield and quality. Sorghum grain yield and quality, soil NO3–N and water were measured in a rotation study in 2003 and 2004 on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudoll). Cropping sequences were continuous sorghum, and sorghum rotated with non‐nodulating and nodulating soybean. Soil amendments consisted of no amendment, manure (17–26 Mg dry matter ha−1 yr−1), and N (84 kg ha−1 yr−1). CS × SA interaction effects were found for most parameters. Rotation with non‐nodulating soybean without SA increased yield by 2.6 to 2.8 Mg ha−1 over continuous sorghum without SA. Rotation without SA with nodulating soybean further increased yield by 1.7 to 1.8 Mg ha−1 over rotation with non‐nodulating soybean. Grain N increased by 0.5 to 1.0, 2.5 to 5.0, and 3.3 to 4.9 g kg−1 for N application to continuous sorghum and sorghum rotated with non‐nodulating and nodulating soybean, respectively. Tangential abrasive dehulling device (TADD) removal indicated that continuous sorghum without SA produced the softest grain with 43 to 44% TADD removal, and sorghum rotated with nodulating soybean with manure produced the hardest grain with 22 to 27% TADD removal. As food end‐use opportunities for sorghum grain evolve, use of crop rotation and SA application will be important to produce grain with desirable quality attributes.

Effects of Commercial Diazinon and Imidacloprid on Microbial Urease Activity in Soil and Sod

Diazinon [O,O-diethyl O-2-isopropyl-6-methyl(pyrimidine-4-yl) phosphorothioate] and imidacloprid [1-(1-[6-chloro-3-pyridinyl]methyl)-N-nitro-2-imidazolidinimine] are applied to lawns for insect control simultaneously with nitrogenous fertilizers such as urea, but their potential effect on urease activity and nitrogen availability in turfgrass management has not been evaluated. Urease activity in enzyme assays, washed cell assays, and soil slurries was examined as a function of insecticide concentration. Intact cores from field sites were used to assess the effect of insecticide application on urease activity in creeping bentgrass (Agrostis palustris Huds.) and bluegrass (Poa pratensis L.) sod. Bacterial urease from Bacillus pasteurii and plant urease from jack bean [Canavalia ensiformis (L.) DC.] were unaffected by the insecticides. Both insecticides inhibited the growth of Proteus vulgaris, a urease-producing bacterium, but only diazinon significantly reduced urease activity in washed cells; neither insecticide inhibited urease activity in sonicated cells. Neither diazinon nor imidacloprid inhibited urease activity in Woolper soil (fine, mixed, mesic Typic Argiudoll) slurries, but diazinon slightly inhibited urease activity in Maury soil (fine, mixed, semiactive, mesic Typic Paleudalf) slurries. Imidacloprid had no effect on urease activity in creeping bentgrass or bluegrass sod at up to 10 times the commercial application rate. Diazinon briefly, but significantly, reduced urease activity in bluegrass sod. Co-application of imidacloprid and urea appears to be benign with respect to urease activity in soil and sod. Diazinon, in contrast, appears to have a significant, short-term, inhibitory effect on the microbial urease-producing community, but that effect depends on soil type.

Changes in Soil Attributes Following Low Phosphorus Swine Slurry Application to No-Tillage Sorghum

Swine (Sus scrofa) slurry can serve as an excellent fertilizer source. Application at rates to meet crop N requirements can result in excess soil P due to low manure N/P ratios. Low phytate corn (LPC) (Zea mays L.) stores a greater proportion of P as phosphate than does traditional corn (TC) increasing bioavailability of P in pig feed grain. Improved utilization of feed P reduces P concentration in manure and soil P accumulation. However, the potential effects of LPC manure on other soil properties are not known. Changes in soil attributes over 3 yr were compared for soils receiving LPC manure, TC manure, inorganic fertilizer, and no nutrients in no-tillage sorghum [Sorghum bicolor (L.) Moench] on a Sharpsburg clay loam (fine, smectitic, mesic Typic Argiudolls). Soil physical properties exhibited values that should not inhibit crop growth. Several soil chemical properties differed by year and treatment. Particulate organic matter (POM), NO 3 -N, pH, and extractable P increased with manure additions. Extractable P content was greater with addition of TC than LPC manure. Soil chemical properties exhibited values acceptable for crop production, but increasing extractable P increases the potential for environmental contamination. Biological soil properties varied in their response to treatments. Microbial biomass C decreased in the control and increased in manure treatments. The Soil Management Assessment Framework (SMAF) was used to conduct a dynamic soil quality assessment. The SMAF index values were similar across years in the control and inorganic fertilizer treatments and increased in both manure treatments. Manure additions improved soil properties affecting crop production, with P accumulation and the potential for environmental contamination being lower with LPC manure. LPC manure applied at rates to meet crop N requirements will have slower soil P accumulation rates and a lower potential for P contamination of the environment.

Land‐use Effects on Anion‐associated Cation Leaching in Response to Above‐normal Precipitation

AbstractFertilizers and liming agents are generally used to achieve optimal economic yields. However, several negative effects of long‐term annual fertilization of nitrogen (N) in particular have been observed, such as reduced cation exchange capacity and decreased base saturation, which may stimulate accelerated leaching loss of other nutrients. Equilibrium‐tension lysimeters installed at a depth of 1.4 m were used to evaluate leaching of soil‐solution ionic constituents from a tallgrass prairie restoration and optimally and deficiently N‐fertilized, no‐tillage (NT) and chisel‐plowed (CP) maize (Zea mays L.) agroecosystems on Plano silt loam soil (fine‐silty, mixed, superactive, mesic Typic Argiudoll). This study was conducted in south‐central Wisconsin, USA during a 1‐year period of above‐normal precipitation between January 2000 and January 2001. The loss of soluble constituents added to agroecosystems to maintain adequate soil fertility and pH, such as N, phosphorus, potassium, calcium, and magnesium, was generally numerically smaller from the natural prairie 25 years after conversion from cultivated agriculture than from optimally and deficiently N‐fertilized, NT and CP maize agroecosystems, though the differences were not significant. Tillage and fertilizer N‐rate generally did not significantly affect drainage, ionic concentrations, or their leaching losses in the maize agroecosystems, though all parameters evaluated tended to be numerically smaller in the deficiently than optimally N‐fertilized maize agroecosystems. Nitrate‐N leaching losses were generally significantly positively correlated with leaching losses of K, Ca, Mg, and Na in the maize agroecosystems, but not for the prairie, indicating that nitrate‐N leaching plays a significant role in the concomitant loss of cations to maintain soil‐solution charge balance in N‐fertilized maize agroecosystems in a temperate environment.

Comparison of Estimates of First‐Year Dairy Manure Nitrogen Availability or Recovery Using Nitrogen‐15 and Other Techniques

Measurements of dairy manure nutrient availability to crops typically show great variability. Approaches that are more accurate are needed to improve manure management and reduce nutrient loss to the environment. In this study, we compared direct (15N recovery) and indirect (difference method [Diff Meth] and fertilizer equivalence [FE] approach) methods of determining first-year dairy manure N availability or recovery during three cropping seasons. A field experiment was conducted on a Plano silt loam (fine-silty, mixed, superactive, mesic Typic Argiudolls) planted to corn (Zea mays L.). Plots received either manure, fertilizer N, or no N. Microplots receiving 15N-labeled manure were also established each study year. Manure was applied to a new plot each cropping season. Whole-plant N uptake was the best crop parameter to use for FE estimates. Estimates of N availability by relative effectiveness (Rel Eff), which are derived from the Diff Meth, and FE were similar (32 and 41%, respectively) and higher than unlabeled N or 15N recovery measurements because these indices factor in N use efficiency. Measures of the Rel Eff of manure N use were highly affected by control plot N uptake. The FE approach is less influenced by control plots, but it requires the inclusion of several more treatments and use of mathematical functions to describe crop response to N. These limitations are reflected in the wide ranges obtained for N availability estimates (-60 to 148%). Although apparent N recovery by the Diff Meth (14%) or direct measurements of 15N recovery (16%) were close on average, variability tended to be much lower for the 15N method. In addition, the Diff Meth was highly dependent on initial soil conditions. Use of 15N-labeled manure, although more costly and time-consuming, provided more consistent and reliable results.

Soil organic carbon content and composition of 130‐year crop, pasture and forest land‐use managements

AbstractConversion of former agricultural land to grassland and forest ecosystems is a suggested option for mitigation of increased atmospheric CO2. A Sharpsburg prairie loess soil (fine, smectitic, mesic Typic Argiudoll) provided treatments to study the impact of long‐term land use on soil organic carbon (SOC) content and composition for a 130‐year‐old cropped, pasture and forest comparison. The forest and pasture land use significantly retained more SOC, 46% and 25%, respectively, compared with cropped land use, and forest land use increased soil C content by 29% compared with the pasture. Organic C retained in the soils was a function of the soil N content (r=0.98, P<0.001) and the soil carbohydrate (CH) concentration (r=0.96, P<0.001). Statistical analyses found that soil aggregation processes increased as organic C content increased in the forest and pasture soils, but not in the cropped soil. SOC was composed of similar percentages of CHs (49%, 42% and 51%), amino acids (22%, 15% and 18%), lipids (2.3%, 2.3% and 2.9%) and unidentified C (21%, 29% and 27%), but differed for phenolic acids (PAs) (5.7%, 11.6% and 1.0%) for the pasture, forest and cropped soils, respectively. The results suggested that the majority of the surface soil C sequestered in the long‐term pasture and forest soils was identified as C of plant origin through the use of CH and PA biomarkers, although the increase in amino sugar concentration of microbial origin indicates a greater increase in microbial inputs in the three subsoils. The practice of permanent pastures and afforestation of agricultural land showed long‐term potential for potential mitigation of atmospheric CO2.

Colloid-Enhanced Desorption Of Zinc In Soil Monoliths

The desorption and co-transport of metals by ex situ water dispersible soil colloids moving through macropores was evaluated in a leaching experiment utilizing Zn-saturated soil monoliths. The monoliths were created by hydraulically driving steel pipe sections (50 cm diameter 2 50 cm length) into a Loradale silt loam soil (fine, silty, mixed, mesic Typic Argiudolls). Each monolith was saturated in excess of the soil cation exchange capacity (CEC) with ZnCl 2 , then leached at a constant flux with a suspension of water-dispersible colloids fractionated from either the Bt or O horizon of a Beasley (fine, montmorillonitic, mesic Typic Hapludalfs) or Rayne (fine-loamy, mixed, mesic, Typic Hapludults) soil, respectively. Eluents from the monoliths were collected and analysed periodically for colloid and Zn concentration in the soluble and sorbed phase. Colloid and Zn concentration in the eluents varied greatly with respect to colloid type. The Beasley colloid, which had a small particle diameter (< 800 nm) and high sorptive affinity for Zn, showed considerable migrating ability through the soil matrix and enhanced Zn desorption by up to 400 times over that exhibited by a distilled water flushing solution. Eluted Beasley colloids were saturated with Zn at concentrations greater than 50% of the soil's CEC. Enhanced Zn desorption by colloids generated from the organic horizon of the Rayne soil was insignificant because the large colloid size (> 1200 nm) limited transport through the soil matrix. Mineralogical analysis of the eluted colloids revealed that in situ colloid generation was negligible, thus confirming that nearly all of the desorbed Zn fraction was due to the ex situ applied colloid.

Methodological limitations and N-budget differences among a restored tallgrass prairie and maize agroecosystems

Interpretation of elemental balances requires careful assessment of component terms and their errors, especially for the major terms of the nitrogen (N) budget which has implications for environmental health. This study reports results from independent field measurements of major annual N-budget components, including atmospheric deposition, fertilizer added, net mineralization, residue returned, soil storage changes of inorganic N, leaching, and plant uptake. Measurements were made in a restored tallgrass prairie and optimally and deficiently N-fertilized, no-tillage and chisel-plowed maize ( Zea mays L.) agroecosystems on Plano silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll (USDA); Haplic Phaeozem (approximate FAO)) in Wisconsin between 1995 and 1999. Denitrification and N losses due to runoff were assumed negligible and bulk density was assumed uniform with depth and across ecosystems. Annual inorganic N leaching was negligible in the restored prairie, but represented 3–57% of the amount of fertilizer-N applied in the optimally N-fertilized agroecosystems. On an annual basis, closure of the inorganic-N budget yielded cumulative errors that were often undesirably large; indicating methodological problems with quantifying ecosystem N cycling in situ. Increased spatial sampling is required to reduce individual measurement errors of two components with large uncertainties; namely net N-mineralization and soil inorganic N changes. Profile-scaled net N-mineralization generally did not balance with the residue N input from the previous year, but the imbalance agreed with the N-budget imbalance. Both results suggest that the prairie is accumulating N slowly, the deficiently N-fertilized maize plots are losing N more rapidly, and the optimally N-fertilized maize plots have too large an uncertainty to be interpreted confidently. Nitrogen-use efficiency, defined on a N-uptake basis, did not differ among the prairie and deficiently N-fertilized maize for 3 out of 5 years, but the prairie was significantly more efficient than the optimally N-fertilized maize.