Many of the native prairies in southern Wisconsin and the midwestern United States in general have been replaced by conventional till (chisel plow) and no-tillage corn agroecosystems.  However, knowledge of the influence of land use change on the structure and function of ecosystems is incomplete.  Soil surface CO₂ flux is a major transfer of carbon from terrestrial ecosystems to the atmosphere and varies greatly among vegetation types.  We measured soil surface carbon dioxide flux and microbial biomass in tilled and no-till corn agroecosystems and a restored prairie ecosystem, examined the influence of various environmental factors on soil surface CO₂ flux in these ecosystems, and estimated annual soil surface CO₂ flux for the natural and managed ecosystems.  Soil surface CO₂ flux is significantly greater for prairie and conventional tilled corn than for no-till corn in the spring, greater for prairie than tilled and no-till corn from July to early October, and is similar for all three ecosystems in the late fall and winter.  Soil surface CO₂ flux is positively correlated to soil temperature at 10 cm for all three ecosystems (r² = 0.43-0.60, p < 0.001), but is only weakly correlated to soil moisture. Using an empirical model to estimate soil surface CO₂ flux from 10 cm soil temperatures, we estimate annual soil surface CO₂ fluxes of 508, 535, and 719 (g C m^-2 yr^-1) for the tilled and no-till corn and restored prairie ecosystems, respectively, demonstrating that land use practices can significantly affect soil surface CO₂ flux.

An equilibrium tension lysimeter (ETL) was designed to maintain equilibrium between lysimeter suction and soil matric potential.  ETL replicates were  installed in a natural prairie, and nitrogen-fertilized no-tillage and chisel plow agroecosystems to measure drainage through undisturbed soil.  The ETLs were used to monitor drainage continuously at 1.4 m below the soil surface through a 0.2-um pore diameter stainless steel porous plate (0.19 m²).  Heat dissipation sensors were used to record variations in matric potential inside and outside the ETL’s sampling area.  Suction was maintained on lysimeters according to the matric potential experienced by the surrounding bulk soil.  Cumulative lysimeter drainage was 199, 563, and 793 mm for the prairie, fertilized no-tillage, and fertilized chisel plow agroecosystems for 132 weeks between 25 June 1995 and 3 January 1998.  Drainage accounted for 11, 31, and 44 % of precipitation inputs for the prairie, fertilized no-tillage, and fertilized chisel plow systems.  Variability between lysimeter replicates was smallest for the prairie, where the coefficient of variation (CV) was 8.2%, and largest for the N-fertilized no-tillage agroecosystem (CV=36.6%).

Brye, K.R., J.M. Norman, L.G. Bundy, and S.T. Gower. 2000. Water budget evaluation of prairie and maize ecosystems. Soil Sci. Soc.
        Am. J. 64:715-724.

Annual monitoring of water budget components is useful for comparing the fate of water inputs among ecosystems.  We hypothesize that land-use changes from natural prairies to managed agroecosystems have altered water budget components.  Weekly hydrological budgets for a restored natural prairie and corn (Zea mays L.) agroecosystems (no-tillage and chisel-plow) were constructed for 132 consecutive weeks between June 1995 and January 1998.  Precipitation, drainage, soil water storage changes, and snow cover changes were measured on Plano silt loam soil (fine-silty, mixed, mesic Typic Argiudoll) at agricultural and prairie sites.  Compared with the corn ecosystems, the prairie maintained greater soil water contents deeper in the soil profile (0.8 - 1.4 m), somewhat larger evapotranspiration (Et), and significantly less drainage due to considerable interception of precipitation by a residue layer.  Soil water storage in the no-tillage corn setting was more similar to the prairie, while Et, net primary productivity, and drainage were more comparable to the chisel-plow agroecosystem.  Total drainage measured with equilibrium-tension lysimeters was 199 (CV = 5.7 %), 563 (CV = 13.6 %), and 793 (CV = 18.5 %) mm of water for the prairie, no-tillage corn, and chisel-plow corn ecosystems, respectively.  Residue interception for the prairie was 477 mm compared to 681 mm of precipitation during the growing season of 1997, which contributed to lower prairie drainage.  The combination of similar productivity, higher soil water contents, and less drainage than the chisel-plow ecosystem suggests that a no-tillage ecosystem is more sustainable than the chisel-plow agroecosystem in terms of reducing potential adverse environmental impacts associated with soil water movement.

Excessive N rates applied to cropland increase the potential for NO₃ leaching from the root zone to groundwater.  This study determined the effect of several cropping systems and N rates, providing a range of N availability to corn (Zea mays L.), on soil water NO₃ concentrations and leaching below the root zone.  Four cropping/manure management systems were established in 1993 and 1994 (8-site yrs) at Arlington, WI, on a Plano silt loam (fine-silty, mixed, mesic Typic Argiudoll).  Corn was planted and seven rates of ammonium nitrate (0 to 204 kg N ha^-1 in 34 kg increments) were broadcast applied at planting.  Economic optimum N rates (EONR) ranged from 0 to 150 kg ha^-1 depending on site-yr.  Soil water NO3 concentrations were determined for an 18-month period using porous-cup lysimeters installed at a 120-cm depth in the 0 and 204 kg N ha^-1 rate treatments.  Average NO₃-N concentrations were <10 mg L^-1 where fertilizer N rates >50 kg N ha^-1 below the EONR, 10 to 20 mg L^-1 at EONR, and >20 mg L^-1 where fertilizer N rates were >50 kg N ha^-1 above the EONR.  Total NO₃-N leaching estimates for the 18-month study period ranged from 3 to 88 kg ha^-1 depending on crop management system, excess N fertilizer rate, drainage amount, and time of drainage event relative to treatment establishment.  An end-of-season soil NO₃ test appears to be capable of assessing corn N management practices and indicating the amount of excess N fertilizer applied which may potentially be leached from the root zone.

Land management practices such as no-tillage agriculture and tallgrass prairie restoration have been proposed as a possible means to sequester atmospheric carbon, helping to refurbish the soil fertility and replenish organic matter that was lost due to previous agricultural management practices. However, the relationship between these land use changes and ecosystem structure and functioning is not yet understood.  We studied soil and vegetation properties over a four-year period (1995-1998), and assembled measurements of microbial biomass, soil organic carbon (SOC) and nitrogen (N), N-mineralization, soil efflux of CO2, and leached C and N in managed (maize; Zea mays L.) and natural (prairie) ecosystems near the University of Wisconsin Agricultural Research Station at Arlington. Field data show that different management practices (tillage and fertilization), and ecosystem type (prairie versus maize) have profound influence on biogeochemistry and water budgets between sites.

These measurements were used in conjunction with a dynamic terrestrial ecosystem model, called IBIS (the Integrated BIosphere Simulator), to examine the long-term effects of land-use changes on biogeochemical cycling. Field data and modeling suggest that agricultural land management near Arlington between 1860 and 1950 caused SOC to be depleted by as much as 63% (native SOC  ~25.1 kg C m^-2).  Reductions in N-mineralization and microbial biomass were also observed.  While IBIS simulations depict SOC recovery in no-tillage maize since the 1950s and also in the Arlington prairie since its restoration was initiated in 1976, field data suggest otherwise for the prairie. This restoration appears to have done little to increase SOC over the past 24 years. Measurements show this prairie contains between 28% and 42% less SOC (in top 1-m) than the no-tillage maize plots and 40-47% less than simulated potential SOC for the site in 1999.  Because IBIS simulates competition between C3 and C4 grass species, it is hypothesized that current restored prairies, which include many forbs not characterized by the model, could be less capable of sequestering C than agricultural land planted entirely in monocultural grass in this region.  Model output and field measurements show a potential 0.4 kg C m^-2 y^-1 difference in prairie NPP.  This study indicates that high productivity C4 grasslands (NPP = 0.63 kg C m^-2 y^-1) and high-yield maize agroecosystems (10 Mg ha^-1) have the potential to sequester C at a rate of 74.5 g C m^-2 y^-1 and 86.3 g C m^-2 y^-1, respectively, during the next 50 years across southern Wisconsin.

An in-situ-soil-core/ion-exchange-resin-bag (ISC/IERB) field method has been used to measure nitrogen (N) mineralization in intact soil cores, but has not been widely tested in fertilized agricultural soils.  We measured N-mineralization in the top 20 cm using the ISC/IERB technique from 1996 through spring 2000 in N-fertilized and unfertilized, no-tillage (NT) and chisel-plowed (CP) maize (Zea mays L.) agroecosystems on Plano silt loam (fine-silty, mixed, superactive, mesic Typic Argiudoll) in Wisconsin.  We modified the technique to include a sand bag below the resin bag to act as a N-diffusion barrier, fertilized individual soil cores with a small volume of fertilizer solution, and collected initial soil samples from within the soil core, and plugged the holes with lucite rod to minimize anomalous moisture redistribution patterns in the core.  Following the modifications, N-mineralization rates for the fertilized CP treatment were significantly higher than for the unfertilized CP treatment (p-value = 0.001) in 2000.  A bootstrap statistical re-sampling procedure showed that sample variability could be reduced by using the refined ISC/IERB field method for N-mineralization.

The drainage of water and leaching of dissolved constituents represent major components of agroecosystem mass budgets that have been exceedingly difficult to measure.  Equilibrium-tension lysimeters were used to monitor drainage, nitrogen (N), and carbon (C) leaching through Plano silt loam (fine-silty, mixed, mesic Typic Argiudoll) for a 4-yr period in a restored prairie and N-fertilized no-tillage and chisel-plowed maize (Zea mays L.) agroecosystems.  Mean drainage recorded over four years for the prairie, no-tillage, and chisel-plowed ecosystems was 461, 1116, and 1575 mm and represented 16, 33, and 47 % of precipitation plus melting of drifted snow received, respectively.  Total inorganic N leaching losses during the 4-yr period for the prairie, no-tillage, and chisel-plowed ecosystems were 0.6, 201, and 179 kg N ha^-1, respectively.  Inorganic N leaching represented 26 and 24 % of applied fertilizer N additions to the no-tillage and chisel-plowed agroecosystems.  Total dissolved C leaching losses were 119, 435, and 502 kg C ha^-1 for the prairie, no-tillage, and chisel-plowed ecosystems, respectively.  Sufficient dissolved organic C (DOC) and nitrate-N existed in the prairie and agroecosystems to support subsoil denitrification, however potential denitrification was limited by insufficient lengths of saturated soil conditions in all three ecosystems, the supply of DOC in the agroecosystems, and the supply of nitrate-N in the prairie.  Based on available DOC and nitrate-N, the maximum contribution of denitrification below the root zone in the agroecosystems was less than 25 % of the total amount of leached nitrate-N and the likely contribution of denitrification was much less.

Land use changes and management practices greatly influence the carbon (C) budget of terrestrial ecosystems.  Independent estimates of components of the C budget for a restored tallgrass prairie, and fertilized and unfertilized no-tillage and chisel plow corn (Zea mays L.) agroecosystems on a Plano silt loam soil (fine-silty, mixed, mesic Typic Argiudoll) were measured for four years (1995-1998).  Carbon budget components evaluated included aboveground net primary production (NPP), grain C removal, soluble C leaching, soil surface CO₂ flux, and soil C storage changes.  Soluble C leaching was greater for the fertilized agroecosystems than for the restored prairie for 1996, 1997, and 1998, respectively.  The soil surface CO₂ flux was 719, 853, and 886 g C m^-2 yr^-1 for the prairie, and varied between 508 and 535, 275 and 358, and 295 and 380 g C m^-2 yr^-1 for the agroecosystems in 1995, 1997, and 1998, respectively.  Averaged for a 4-yr period, the soil C contents increased in the prairie and decreased in all four agroecosystems.  Aboveground NPP was 6 to 10 times greater for the agroecosystems than the tallgrass prairie.  Net ecosystem productivity, neglecting annual variations in stored soil C,  was nearly balanced, but negative, for the prairie and positive for the fertilized agroecosystems for 1996, 1997, and 1998, suggesting the restored prairie is a net C source and the agroecosystems are a net C sink.  However, direct soil C measurements suggest, though statistically insignificant, that soil C is slightly increasing for the prairie and decreasing for the agroecosystems.  Several indices depicting ecosystem service characteristics were greater for the restored prairie than for the agroecosystems.

Equilibrium-tension lysimeters were used to quantify year-round drainage, inorganic nitrogen (N) concentrations, and inorganic N leaching losses from undisturbed Plano silt loam soil (fine-silty, mixed, mesic Typic Argiudoll) of N-fertilized no-tillage and conventionally-tilled chisel plow corn (Zea mays L.) agroecosystems for 1996, 1997, and 1998.  The chisel plowed corn agroecosystem consistently had greater drainage losses of water from its soil profile than a no-tillage corn agroecosystem over the 3 year period.  Both fertilized tillage treatments maintained nitrate-N concentrations above the 10 mg L^-1 safe drinking water standard for the majority of the three growing seasons monitored between 1996 and 1998.  Inorganic N leaching losses were nearly the same for both fertilized corn tillage treatments for the first 2 years of this 3 year study.  During the third year, inorganic N leaching losses from the fertilized no-tillage corn agroecosystem were greater than inorganic N leaching losses from the fertilized chisel plow corn agroecosystem.

A study was undertaken to evaluate, characterize, and model various components of the C and N cycles of several common and historic land use patterns of Wisconsin (e.g. chisel plow and no-till corn, and natural prairie).  The ecosystems under investigation reside on a silt loam soil with similar edaphic properties and morphological characteristics.  In April 1995, initial total soil C and organic matter content for the top 30 cm layer were the same in all ecosystems.  Nitrate leaching and drainage were quantified in the field using suction plate lysimeters. The chisel plowed corn ecosystem had greater cumulative drainage from July 1995 through May 1996 than the other two ecosystems, where the prairie’s drainage was ten times less than that measured under cultivation.  Cumulative, post-growing season NO₃^- leaching losses between October 1995 and April 1996 were 12.4, 7.4, and <0.05 kg NO₃^-N ha^-1 for the chisel plow, no-till, and prairie systems, respectively.  The differences in NO₃^- leaching can be attributed to decreasing drainage and substantially lower soil solution NO₃^- concentrations for the prairie ecosystem.  These results confirm the environmental concern over groundwater contamination by nitrates associated with production agriculture.

The balance of moisture inputs and outputs for an ecosystem influences many processes within the soil environment.  The components of the water budget for a chisel plow and no-till corn, and a natural prairie ecosystem were continuously monitored over the annual cycle of 1996.  The ecosystems reside on a silt loam soil with similar soil physical properties, and climatic and physiographic characteristics.  The drainage component was measured using suction plate, pan lysimeters.  Evapotranspiration estimates were obtained by calculating a residual difference from each water budget.  Annual measured drainage from the prairie, no-till corn, and chisel plow corn ecosystems accounted for 18, 35, and 47 % of total precipitation inputs.  The same trend exists for drainage losses over the course of the growing season (e.g., May through September).  Drainage losses relative to moisture inputs were greatest between the months of January and March, while a layer of frozen soil persisted, for both agroecosystems.  Prairie drainage losses were largest between the months of April and June following the disappearance of frost.  An ecosystem's water budget, especially the downward flux of soil moisture, effects and controls numerous soil processes, probably most notable being the potential contamination threat of nitrates and other solutes leaching to our groundwater reserves.

Land use and above-ground management schemes influence the fate of moisture inputs to the soil.  The water budgets for a natural prairie, fertilized no-tillage and chisel plow corn, and unfertilized no-tillage and chisel plow corn agroecosystems are evaluated for eighty-two consecutive weeks.  Precipitation, soil moisture storage changes, and drainage are measured in the field.  Evapotranspiration is calculated by difference from the water budget.  Runoff is indirectly estimated for discrete, extreme climatic events.  The drainage component of the water balance is measured using porous stainless steel equilibrium tension pan lysimeters under undisturbed soil columns.  Lysimeter tension is held slightly more negative than the tension of the surrounding bulk soil to recreate natural water flow patterns year round.  Cumulative variability in lysimeter drainage estimates for more than 400 days is less than 26 % for all replicate pairs of lysimeters, which we feel is acceptable given the inherent variability in soil hydraulic properties in general.

 The long-term water budgets of the natural and managed ecosystems are different despite the ecosystems having similar soil properties.  Precipitation is slightly less in the prairie than in the agricultural ecosystems due to small geographic separation of the two study sites.  Evapotranspiration is similar for the natural and managed ecosystems.  However, drainage patterns are distinctly different.  The chisel plow agroecosystem allows 419 mm of water to percolate past a 1.4 m soil depth plane compared to 1198 mm of precipitation in eighty-two weeks.  In contrast, the no-tillage agroecosystem yields 308 mm of drainage and the natural prairie allows 116 mm of drainage.  The amount of water available to the prairie to drain through the soil profile is significantly influenced by the residue cover and the process of rainfall interception.

 The Cupid model is used to simulate a seven month growing season for the natural and managed ecosystems.  Cupid's prediction for evapotranspiration and drainage agrees well with calculated and measured results.  Soil moisture storage change predictions deviate from measured data for all ecosystems.

Nitrogen leaching losses are influenced by soluble nitrogen, primarily nitrate (NO₃^-), in the soil solution and the movement of water through the soil profile.  The drainage component of the water balance is the process responsible for leaching nitrogen from agricultural ecosystems.  Drainage and soil solution nitrogen concentrations have been continuously monitored in optimally fertilized conventional-till (i.e. chisel plow) and no-tillage corn to evaluate long-term leaching trends.  The corn plots exist on a fine textured silt loam soil at the Arlington Agricultural Research Station.

 Natural water movement through undisturbed soil is challenging to measure.  In this study, drainage has been measured using equilibrium tension pan lysimeters.  Chemical analysis is performed on leachate collected from the lysimeters to determine inorganic nitrogen concentrations.

 Drainage and nitrogen leaching losses have been quantified continuously since June 1995.  Overall, the chisel plowed soil drained more, however maintained lower soil solution nitrogen concentrations than compared to the no-tillage treatment.  On an annual basis, 1996 was above the 30 year normal for precipitation.  Consequently, drainage and nitrogen leaching losses increased.  Of the 744 mm of precipitation received by the agricultural corn plots in 1996, 351 mm and 262 mm of water drained through the chisel plow and no-tillage soil profiles.  Nitrogen leaching losses for the year were the same for both tillage treatments, 63 kg ha^-1.  Greater than 85% of the annual leaching losses occurred during the growing season between 5 May and 22 August in 1996 representing almost 30% of the total quantity of applied fertilizer nitrogen.  The leaching of fertilizer-applied nitrogen is controlled by precipitation inputs and drainage, but still is responsible for environmental degradation and unnecessary economic losses.

Field measurements of drainage and solute leaching are indispensable in the context of understanding the dynamics of the hydrologic and nutrient cycles of any ecosystem.  An equilibrium tension lysimeter (ETL) was designed and replicates were  installed in a natural prairie, and nitrogen-fertilized no-tillage and chisel plow agroecosystems to measure drainage through undisturbed Plano silt loam soil.  The ETLs monitor drainage continuously at 1.4 m below the soil surface through a 0.2-um pore diameter stainless steel porous plate (0.19 m²).  Heat dissipation sensors were used as tensiometers to record variations in matric potential inside and outside the ETL’s sampling area.  Tension was maintained on lysimeters according to the matric potential experienced by the surrounding bulk soil.  Lysimeter drainage variability between replicates was smallest for the prairie (CV=5.9%) and largest for the N-fertilized chisel plow agroecosystem (CV=29.2%).  Nitrate losses were smallest for the prairie (< 0.3 kg ha^-1).  Based on 825 days of continuous measurements, nitrate losses were 155 kg ha^-1 (CV=4.1%) for the fertilized chisel plow agroecosystem and 165 kg ha^-1 (CV=22.0%) for the fertilized no-tillage agroecosystem.

Periodic burning is a common prairie restoration management practice that is intended to promote new growth, better species establishment, and improved seed quality.  However, altering the character of the above-ground vegetation strongly influences the hydrologic cycle of a natural prairie.  The impact of burning on above-ground biomass and residue, precipitation interception, and drainage was examined in a restored tallgrass prairie on Plano silt loam soil (Typic Argiudoll).  During the pre-burn growing season (1997), peak prairie biomass and necromass were 1.5 and 1.0 Mg ha^-1, respectively.  The precipitation interception capacity of the necromass residue averaged 11.4 mm, ranging from 1.3 to 32.7 mm depending on rainfall intensity.  Annual drainage below a 1.4 m soil profile in the prairie was 83 mm of 644 mm of precipitation.  During the post-burn growing season (1998), above-ground biomass more than doubled to 3.1 Mg ha^-1, while no necromass residue existed until late in the growing season.  With negligible  residue interception, the soil moisture status was regularly greater throughout the 1.4 m profile during the post-burn year compared to the pre-burn year.  Consequently, post-burn annual drainage increased significantly to 208 mm of 691 mm of precipitation received.

Preferential flow of water and solutes may be occurring through agricultural soil between growing seasons due to winter snow melt and during the growing season due to extreme precipitation events.  Equilibrium tension lysimeters (ETLs) were used beneath 1.4 m undisturbed soil columns of Plano silt loam (Typic Argiudoll) to make observations suggesting drainage and solute leaching occurred preferentially through frozen and unfrozen soil.  Three event period, two winter snow melts and an intense rainfall, were chose to illustrate the potential for preferential flow.  Between 3 January and 5 February 1996, an ETL recorded 119 mm of drainage through > 70 cm of frozen soil following 45 mm of water from snowfall and 81 mm water from melting snow.  Between 16 and 19 June 1996, 116 mm and 119 mm drained through no-tillage and chisel plow soil following 116 mm of rainfall.  This event was responsible for 51 kg N ha^-1 to be leached from no-tillage and chisel plowed corn plots.  Between 31 December 1996 and 7 January 1997, 41 mm of drainage was recorded through > 70 cm of frozen chisel plowed soil following the addition of 10 mm of water as rainfall, 11 mm of water as melted snow cover, and 28 mm of water as snowfall.

Components of the annual carbon and nitrogen budgets were evaluated for a natural restored tallgrass prairie and fertilized and unfertilized, no-tillage and chisel plow corn agroecosystems for a four year period.  The natural prairie and corn agroecosystems are located near Arlington, Wisconsin and reside on Plano silt loam soil (fine-silty, mixed, mesic Typic Argiudoll).  Inorganic nitrogen and dissolved carbon leaching losses were quantified in-situ using equilibrium-tension lysimeters.  Inorganic nitrogen leaching was a negligible component of the nitrogen balance for the natural prairie, however nitrogen leaching was a significant component of the nitrogen balance for the fertilized agroecosystems.  Dissolved carbon leaching was greatest for the fertilized chisel plow agroecosystem and smallest for the natural prairie.  Denitrification was assumed negligible for all ecosystems. However, large net nitrogen mineralization field measurements for the agroecosystems suggested that denitrification may be a significant export of nitrogen from the agroecosystems since leaching losses could not alone reconcile the differences between the inputs and outputs of nitrogen to the fertilized agroecosystems.  Soil surface carbon dioxide emissions from the prairie were significantly higher than carbon dioxide emissions from the agroecosystems.  High soil respiration fluxes contributed to the nature of the restored prairie being a net carbon source rather than a net carbon sink.  Carbon leaching was a minor component of the carbon budgets for both the prairie and agroecosystems.  Compared to the prairie, the fertilized agroecosystems were less efficient or leaky in terms of carbon assimilated per unit nitrogen leached.  Computer modeling of soil biogeochemical cycling complemented field measurements and provided valuable insight into the mechanisms contributing to and controlling such important processes as nitrate leaching from the rooting zone of fertilized crops.

Simultaneous processes of nutrient import and export occur in prairies of relatively large areal extent as a result of prescribed burning.  However, these processes are markedly altered when burning is imposed on prairie fragments.  The loss of macro- and micro-nutrients contained in above-ground litter following prescribed burning was assessed in a fragmented, 24-yr-old restored tallgrass prairie in south central Wisconsin.  The combustion process reduced necromass by > 90 % and produced losses > 70 % of the pre-burn litter-contained mass of N, C, S, Al, Cu, Ca, Mg, Fe, Mn, Na, B, and Zn.  Since many of Wisconsin’s existing remnant and restored prairies are relatively small and fragmented in the landscape, a net export of nutrients is likely to occur, as a result of prescribed burning, followed by no long-term increase in soil nutrient status.  Without replenishment of the essential plant nutrients to the soil, that are exported during combustion, prairies may suffer continued depletion of soil nutrient pools, or at least no increase in pre-cultivation levels.  Consequently, the function and structure of restored tallgrass prairies may never achieve the level they once had as native tallgrass prairies.

Carbon (C) leaching is important in natural and managed ecosystems because it represents a mechanism for C loss. Equilibrium-tension lysimeters (ETLs) were used beneath 1.4 m undisturbed soil columns of Plano silt loam (Typic Argiudoll) to quantify soluble C leaching for a 4-yr period from 1996 through 1999 in a natural tallgrass prairie and nitrogen-fertilized no-tillage and chisel plowed maize (Zea mays L.) agroecosystems.  Total drainage was greatest for the chisel plowed agroecosystem and smallest for the prairie during the 4-yr period.  Total C concentrations averaged 27, 54, and 50 mg C L-1 and organic C concentrations averaged 13, 16, and 17 mg C L-1 for the prairie, no-tillage, and chisel plowed agroecosystem, respectively.  Cumulative total C leaching losses were 124, 472, and 548 kg C ha-1 for the prairie, no-tillage, and chisel plowed agroecosystem, respectively.  The organic C fraction was 58, 31, and 36 % of total leached C for the prairie, no-tillage, and chisel plowed agroecosystem, respectively.  Though the magnitude of C leaching is relatively minor compared to the magnitude of other components of  the C budget, the presence of soluble organic carbon at depth in a soil profile also represents an important source of C that could potentially support subsoil denitrification.

In Wisconsin, fewer than 800 ha of the estimated 850 000 ha of pre-settlement native prairie remain.  Prairie restoration provides erosion control and wildlife habitat and is gaining popularity in Wisconsin partly because natural prairies are aesthetically pleasing.  However, prairie restoration also has the potential to sequester atmospheric carbon (C) to the soil.  Soil C content in the top 1 m and bulk density in the top 10 cm were measured in a chronosequence of tallgrass prairies at a fine-textured site near Arlington, WI (ARL) and a coarse-textured site at the International Crane Foundation (ICF) near Baraboo, WI to evaluate the impact of prairie restoration on C sequestration.  Soil textural differences between the sites contributed to significant differences in soil C content and the potential to sequester C to the soil.  Soil C content in the top 25 cm was significantly positively correlated to time elapsed since last disturbance at the ARL site (r = 0.72, p-value = 0.03), but not at the ICF site.  Bulk density was inversely related to time elapsed since last disturbance at the ARL site (r = -0.53) suggesting that soil structure improved with time, but no relationship was found at the ICF site.  The rates of C sequestration were generally smaller for the sandy than the silt loam soils studied and on average the silt loam soil sequestered more C.  Total C sequestered was positively related, while C sequestration rate was inversely related, to time since last disturbance at the ICF site, but both were inversely related at the ARL site.  Prairie restoration increased the potential for C sequestration in coarse- and fine-textured soils compared to nearby agricultural soils.

Equilibrium-tension lysimeters were used to evaluate and compare dissolved reactive phosphorus (DRP) leaching from a prairie and fertilized no-tillage and chisel-plowed corn agroecosystems on Plano silt loam (fine-silty, mixed, superactive, mesic Typic Argiudolls) in south central Wisconsin during four monitoring periods, March through April 1996, 1997, and 1998, and from January 1999 through September 2000.  A low level of soluble P was found to leach from both natural and managed ecosystems.  Dissolved reactive P leaching losses were higher from the managed compared to the natural ecosystems.  The fertilized no-tillage agroecosystem consistently maintained higher DRP concentrations in soil leachate solutions compared to the fertilized chisel-plowed agroecosystem, which led to higher DRP leaching losses for the fertilized no-tillage agroecosystem, despite greater drainage from the fertilized chisel-plowed compared to the fertilized no-tillage agroecosystem.  Soluble P leaching losses measured for a prairie and fertilized agroecosystems in south central Wisconsin were below acceptable critical limits for P loss.

Nitrogen (N) mineralization is a spatially variable and difficult component of the N cycle to quantify accurately under field conditions.  Obtaining reliable estimates of N-mineralization during the growing season will improve fertilizer recommendations and help minimize undesirable, environmental N-enrichment.  Soil mineral-N content and in-situ net N-mineralization were measured in the surface horizon from 1995 through 1998 in a restored prairie and in N-fertilized and unfertilized, no-tillage and chisel-plowed maize (Zea mays L.) agroecosystems on Plano silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll) in Wisconsin.  An in-situ-soil-core/ion-exchange-resin-bag technique was used to measure net N-mineralization in the top 20 cm.  Land use significantly affected in-situ net N-mineralization, where the smallest rates occurred  in the restored prairie.  Three independent methods for quantifying annual net N-mineralization (i.e., N budget residual, unfertilized plant N uptake, and profile-scaled in-situ field measurements) consistently captured ecosystem, tillage, and fertilizer-N rate effects on net N-mineralization and suggest accuracy limitations of field measurements of N-mineralization.  Laboratory incubations with periodic CaCl₂  leachings showed that fertilization stimulated N-mineralization (in-situ field measurements show this too), but that withholding residue inputs to agricultural soils significantly deceased net N-mineralization carbon dioxide (CO₂) evolution compared to soils that were amended with residue.  Consequently, both mineralized N and labile C were co-limiting factors influencing N-mineralization in agroecosystems.

Most studies of phosphorus (P) movement in soil have based their conclusions on patterns of extractable soil P as a function of depth, which has led to the assumption that no substantial leaching loss occurs because of high P-fixation capacity in mineral soils.  Few studies have involved high-quality leachate samples collected below the root zone, rather most have involved tile drainage systems.  Equilibrium-tension lysimeters installed at a depth of 1.4 m were used to evaluate and compare P leaching from a restored tallgrass prairie and nitrogen (N)-fertilized (f) and N-unfertilized (nf), no-tillage (NT) and chisel-plowed (CP) corn (Zea mays L.) agroecosystems on Plano silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll) in south central Wisconsin during a 5-yr period.  Mean volume-weighted molybdate-reactive P (MRP) and total dissolved P (TDP) concentrations were similar within replicate samples, but always higher in NTf corn than in the prairie or CPf corn systems, though drainage from the CPf corn was always higher than from the NTf corn system.  Water-extractable soil P concentrations at any given depth were not positively correlated with leachate concentrations, suggesting that macropore flow causes infiltrating runoff to preferentially by-pass the bulk of the soil matrix.  Leachate-P concentrations from the natural and managed agroecosystems were environmentally significant (i.e., > 0.01 mg P L^-1) and leaching losses were significantly higher from N-fertilized corn, regardless of tillage, than from the prairie or N-unfertilized corn systems, from which leachate-P concentrations and loads were similar.  Increased root growth from N fertilization could cause more macropore formation, preferential flow, and P-mineralization from decaying roots compared to N-unfertilized systems, which could contribute to an N-fertilization effect on P leaching.