Agroforestry Buffers Research Articles

Agroforestry buffers on nitrogen reduction in groundwater on a grazed hillslope

AbstractAgricultural practices often contribute to the transport of solutes into groundwater; thus, low‐cost strategies that extract nutrients from groundwater are essential to address water pollution. This study evaluated the effects of agroforestry (tree + grass; AB [cottonwood {Populus deltoides Bortr. ex Marsh.}]) and grass buffers (GB; [tall fescue Schedonorus phoenix (Scop.) Holub, Red clover {Trifolium pretense L.}, and Lespedeza {Lespedeza Michx}]) on groundwater nitrogen (N) concentrations. The experiment consisted of two grazing watersheds, one with an AB and another with a GB treatment. Buffers were not grazed since 2001. Three wells representing summit, backslope, and foot‐slope positions were installed at each watershed. Water samples were collected biweekly from November 2019 to January 2022 and analyzed for total nitrogen (TN) and dissolved N (DN). Dissolved nitrogen (DN) and TN concentrations after the AB in the foot‐slope well were 99% (5.36–0.06 mg L−1) and 85% (9.04–1.37 mg L−1) lower than the mean concentration of the summit and backslope wells. Similarly, DN and TN concentrations after the GB in the foot‐slope well were 94% (1.95–0.11 mg L−1) and 62% (2.86–1.07 mg L−1), lower than the mean concentration of the summit and backslope wells. Dissolved N concentrations were lower during warm periods probably due to plant uptake and denitrification in the buffer zone. Results showed that buffers, especially with deep‐rooted trees in the proximity of the water table, decreased TN and DN concentrations in groundwater and can be used as a conservation practice to address water pollution.

Effects of conservation buffer systems on adsorption of fluorescent-labeled Escherichia coli.

The magnitude of bacterial transport through runoff into surface water or infiltration into groundwater is influenced by the adsorption processes in soil. The objective of this study was to evaluate fluorescent-labeled Escherichia coli (E. coli) adsorption by soil under agroforestry buffer (AB), grass buffer (GB), and row crop (RC) management. Adsorption experiments were conducted by inoculating three masses (0.5, 1, and 10 g) of each treatment (AB, GB, and RC) with E. coli O157:H7-GFP with concentration ranges of 105 -108 colony-forming units (cfu) ml-1 . Adsorption data were evaluated using Langmuir, Freundlich, and Temkin adsorption isotherm models. The Freundlich isotherm model described the observed data well for all treatments using the 10-g soil mass, with the R2 values closer to unity in all treatments. The Freundlich Kf parameter, an indicator of adsorption capacity, was higher for the AB treatment (9.93 cfu ml-1 ) compared with the GB and RC treatments (2.32 and 1.27 cfu ml-1 , respectively). The multiple pairwise comparisons test (Tukey test) of the Freundlich 1/nf parameter demonstrated a significant difference (p<.05) between the AB treatment and the RC and GB treatments. Similarly, the Kf values were significantly (p=.05) higher for the 10-g mass under the same test conditions, but no significant differences were observed in the 0.5- and 1-g masses. This study demonstrated that AB has a higher E. coli adsorption capacity and the potential for mitigating the effects of E. coli O157:H7 transport to surface or groundwater through the soil ecosystem.

Spatial and temporal variability of soil organic carbon on a corn–soybean watershed with 23 years of agroforestry

AbstractUnsustainable agricultural practices deplete soil organic carbon (SOC), affecting ecosystem services, land productivity, soil health, and water quality. This study evaluated the long‐term effects of row crop (RC), agroforestry buffers (AB), grass buffers (GB), and grassed waterways (GWW) on SOC. Agroforestry buffers (grass and tree) and grass buffer treatments were established in 1997 on a corn (Zea Mays L.)–soybean (Glycine Max [L]. Merr.) rotation. Grid soil samples from 86 locations were collected in 10 transects to determine SOC at 0–10 and 10–20 cm depths. The general linear model and the generalized linear mixed model were conducted to evaluate treatment, landscape, soil depth, and series effects on SOC. Kriging interpolation was used to visualize the temporal and spatial change of SOC in the watersheds, comparing samples collected in 2000 and 1994 with samples collected in 2020. The mean SOC percentage (SOC%) in the top 10 cm depth for the RC, AB, GB, and GWW areas was 1.94, 2.19, 2.41, and 2.51%, respectively (ρ &lt; .001). The soil depth was significant (ρ &lt; .001) between samples from 0–10 cm and 10–20 cm. The mean SOC% among soil series showed no significant differences at the studied depths. The mean SOC% of 0–10 cm for RC, AB, and GWW were 1.85, 1.88, and 2.30% in 2000 and 1.94, 2.19, and 2.51% in 2020. The foot‐slope position had the highest (2.41%) and the summit position had the lowest SOC (2.02%) percentages. The SOC% in the RC treatment from 0–10 cm at the summit, backslope, and foot slope positions were ranked 1.83 &lt; 2.22 &lt; 2.31%, respectively. Perennial vegetation and undisturbed land management practices increased SOC compared with the RC areas.

Quantifying Agroforestry Yield Buffering Potential Under Climate Change in the Smallholder Maize Farming Systems of Ethiopia

Agroforestry is a promising adaptation measure for climate change, especially for low external inputs smallholder maize farming systems. However, due to its long-term nature and heterogeneity across farms and landscapes, it is difficult to quantitatively evaluate its contribution in building the resilience of farming systems to climate change over large areas. In this study, we developed an approach to simulate and emulate the shading, micro-climate regulation and biomass effects of multi-purpose trees agroforestry system on maize yields using APSIM, taking Ethiopia as a case study. Applying the model to simulate climate change impacts showed that at national level, maize yield will increase by 7.5 and 3.1 % by 2050 under RCP2.6 and RCP8.5, respectively. This projected increase in national-level maize yield is driven by maize yield increases in six administrative zones whereas yield losses are expected in other five zones (mean of −6.8% for RCP2.6 and −11.7% for RCP8.5), with yields in the other four zones remaining stable overtime. Applying the emulated agroforestry leads to increase in maize yield under current and future climatic conditions compared to maize monocultures, particularly in regions for which yield losses under climate change are expected. A 10% agroforestry shade will reduce maize yield losses by 6.9% (RCP2.6) and 4.2 % (RCP8.5) while 20% shade will reduce maize yield losses by 11.5% (RCP2.6) and 11% (RCP8.5) for projected loss zones. Overall, our results show quantitatively that agroforestry buffers yield losses for areas projected to have yield losses under climate change in Ethiopia, and therefore should be part of building climate-resilient agricultural systems.

Long‐term perennial management and cropping effects on soil microbial biomass for claypan watersheds

AbstractSustainable vegetative management plays a significant role in improving soil quality in degraded agricultural landscapes by enhancing soil microbial biomass. This study investigated the effects of grass buffers (GBs), biomass crops (BCs), grass waterways (GWWs), and agroforestry buffers (ABs) on soil microbial biomass and soil organic C (SOC) compared with continuous corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation (row crop [RC]) on claypan soils. The RC, AB, GB, GWW, and BC treatments were established in 1991, 1997, 1997, 1997, and 2012, respectively, and are located at Greenley Memorial Research Center in Missouri. Soil samples were collected in May 2018 from the 0‐ to 10‐cm depth at summit, backslope, and footslope landscape positions. Within AB treatment, soils were collected from the 50‐cm and 150‐cm tree distance. Total microbial biomass and biomass of gram‐positive bacteria, gram‐negative bacteria, actinomycetes, rhizobia, fungi, arbuscular mycorrhizae, saprophytes, and protozoa were determined by phospholipid fatty acid (PLFA) analysis. Results showed that soil microbial biomass and SOC across all microbial groups were significantly higher (P &lt; .01) under perennial vegetation treatments compared with RC. The footslope position exhibited the highest total microbial biomass compared with the summit and backslope positions. The sampling distance of 50 cm from the tree base demonstrated 16% greater total microbial biomass and 15% higher SOC compared with 150 cm. These findings highlight the influence of landscape on soil biological properties and show that perennial vegetation systems have the potential to increase soil microbial biomass and enhance agricultural sustainability in degraded RC systems.

Agroforestry, grass, biofuel crop, and row‐crop management effects on soil water dynamics for claypan landscapes

AbstractSoil water use and water storage vary by vegetative management practices, and these practices affect land productivity and hydrologic processes. This study investigated the effects of agroforestry buffers (AB), grass buffers (GB), and biofuel crops (BC), relative to row crops (RC) on soil water use for a claypan soil in northern Missouri, USA. The experiment located at the Greenley Memorial Research Center included RC, AB, GB, and BC established in 1991, 1997, 1997, and 2012, respectively. Soil water reflectometer sensors installed at 5‐, 10‐, 20‐, and 40‐cm depths monitored soil water from April to November in 2017 and 2018. Results showed significant differences in weekly volumetric water content (VWC) among treatments for all four soil depths in 2017 and 2018. Treatments of AB, GB, and BC had lower VWC (16, 37, and 18% on 9 June), (31, 35, and 20% on 18 August), and (43, 49, and 35% on 29 September) in 2017 and (46, 70, and 19% on 24 August) and (31, 34, and 17% on 5 October) in 2018, respectively, in the pre‐recharge periods for the 5‐cm depth compared with the RC. In the post‐recharge period, equal or occasionally slightly higher soil water occurred in the buffer and biofuel treatments compared to the RC. During recharge, larger increases in soil water due to better infiltration were observed in the perennial vegetative practices relative to RC. The results showed that these practices could significantly influence soil water use and storage compared to RC management, especially for eroded claypan landscapes.

Effects of Conservation Practices on Soil Quality Compared with a Corn–Soybean Rotation on a Claypan Soil

Restoration of degraded lands by adoption of recommended conservation management practices can rehabilitate watersheds and lead to improving soil and water quality. The objective was to evaluate the effects of grass buffers (GBs), biomass crops (BCs), grass waterways (GWWs), agroforestry buffers (ABs), landscape positions, and distance from tree base for AB treatment on soil quality compared with row crop (RC) (corn [Zea mays L.]–soybean [Glycine max (L.) Merr.] rotation) on claypan soils. Soil samples were taken from 10‐cm‐depth increments from the soil surface to 30 cm for GB, BC, GWW, and RC with three replicates. Soil samples were collected from summit, backslope, and footslope landscape positions. Samples were taken at 50‐ and 150‐cm distances from the tree base. β‐Glucosidase, β‐glucosaminidase, dehydrogenase, fluorescein diacetate hydrolase (FDA), soil organic carbon (SOC), total nitrogen (TN), active carbon (AC), and water‐stable aggregates (WSA) were measured. Results showed that β‐glucosidase, β‐glucosaminidase, dehydrogenase, FDA, AC, WSA, and TN values were significantly greater (P &lt; 0.01) for the GB, BC, GWW, and AB treatments than for the RC treatment. The first depth (0–10 cm) revealed the highest values for all soil quality parameters relative to second and third depths. The footslope landscape had the highest parameter values compared with summit and backslope positions. The 50‐cm distance of AB treatment had higher values than the 150‐cm distance for all measured parameters. Results showed that perennial vegetation practices enhanced soil quality by improving soil microbial activity and SOC.Core Ideas Permanent vegetative management (trees and grasses) enhanced soil quality. Perennial practices improved microbial activity and increased soil organic carbon. Perennial vegetative practices have agricultural and environmental significance. Establishing perennial practices is an effective approach to enhance soil quality.

Influence of agroforestry plant species on the infiltration of S-Metolachlor in buffer soils

Agroforestry practices have been acknowledged for reducing pesticide losses while maintaining land productivity. Pesticide removal from overland flow results from great infiltration capacities of the buffer soils. This can in turn threaten the quality of groundwater in case of poor pesticide sorption and degradation in the root-influenced zone. These mechanisms and their balance are likely to be influenced by plant species. However, little is known about the role of agroforestry species in the infiltration of herbicides. The aim of this study was thereby to evaluate how popular agroforestry species modulate the infiltration of water and of a widely used herbicide. We established large buffer microcosms by planting Brome grass, Black walnut, Pin oak and Poplar trees in repacked soil columns. After a growth season of 4 months, we performed ponded infiltration experiments with bromide and S-Metolachlor. We used then the HYDRUS 1D model to compare the hydrodynamic properties and S-Metolachlor transport patterns between the microcosms. In addition, we compared the sorption properties of the rhizosphere and bulk soils. We found that the tree species increased the sorption of S-Metolachlor in soil with Kd being 3 times greater than in the un-vegetated and Brome grass microcosms. Poplar trees increased the hydraulic conductivity (Ksat) compared to the control and was associated to a low retardation of S-metolachlor, which increases the risk of groundwater contamination. With slightly reduced Ksat and retardation factor in the root zone, 1.6 to 1.8 times greater than in the control treatment, Black walnut appears as an optimal species for mitigating S-Metolachlor. The Brome grass and oak microcosms had the lowest Ksat of all treatments and S-Metolachlor retardation factors were equal and slightly increased compared to the control, respectively. These results show that agroforestry buffer's efficiency can be optimized by selecting appropriate species.

Biomass and buffer management practice effects on soil hydraulic properties compared to grain crops for claypan landscapes

Biomass production systems as well as agroforestry and grass buffers have been found to improve soil hydraulic properties and water quality relative to row crop management for temperate regions. Objectives of this study were to assess the effects of biomass crops, agroforestry buffers, and grass buffers grown on claypan soils relative to a traditional corn (Zea mays L.)–soybean (Glycine max L.) rotation for hydraulic properties which included saturated hydraulic conductivity (Ksat), soil water retention, bulk density, and pore size distributions. Experiment was conducted in northeastern Missouri, USA. Buffers and biomass crops were established in 1997 and 2012, respectively. Grain crop production watersheds were established in 1991. Agroforestry buffers consisted of grasses and forbs with pin oak (Quercus palustris Muenchh.) trees. Redtop (Agrostis gigantea Roth), brome grass (Bromus spp.), and birdsfoot trefoil (Lotus Corniculatus L.) were planted in grass buffer areas. Biomass crops included switchgrass (Panicum Virgatum L.) and native grasses. Undistributed soil cores (7.6 cm diam. by 7.6 cm long) were taken by 10 cm depth increments with six replications from the surface to the 40 cm depth. Samples were measured and evaluated for bulk density, Ksat, water retention, and pore size distributions. Results illustrated that bulk density values were significantly lower (P 1000 µm effective diam.) and coarse mesopores (60–1000 µm effective diam.) were significantly higher for the biomass treatment than the other treatments for the first depth 0–10 cm. Although the claypan soil horizon dominates hydrology in northeastern Missouri, this study showed that biomass crops as well as agroforestry and grass buffer practices improve soil hydraulic properties relative to row crop management; they also have valuable economic and environmental benefits.

Improved APEX Model Simulation of Buffer Water Quality Benefits at Field Scale

Abstract. Watershed models offer cost-effective means to quantify the environmental benefits of conservation practices. This study evaluated the ability of the Agricultural Policy/Environmental eXtender (APEX) model to simulate the effectiveness of upland buffers for reducing event runoff, sediment, and total phosphorus (TP) loadings. The study used 16 years of monitoring data (1993-2008) from three field-scale row crop watersheds. Two watersheds had buffers installed in the fall of 1997, one with upland agroforestry buffers (grass plus trees) and the second with upland grass buffers; the third watershed was maintained as a control. Objectives were to (1) determine the effect of upland buffers on APEX parameters, (2) evaluate the ability of APEX to estimate upland buffer effectiveness, and (3) evaluate the impact of alternative buffer placement options on water quality outcomes. After modification of the APEX code to improve simulation of infiltration in the buffers, we successfully calibrated APEX for no-buffer and upland buffer conditions for event runoff and TP. However, calibrated parameters from the no-buffer model simulated buffer conditions poorly and resulted in an overestimation of buffer effectiveness. Buffer effectiveness estimated with upland buffer parameters was similar to that obtained from measured data. Scenario analysis indicated that a combination of backslope and footslope agroforestry buffers was more effective than contour placement for reducing average annual edge-of-field runoff and total P losses. These results highlight the complexity of using APEX to assess upland buffers as well as potential problems when using APEX to quantify the benefits of conservation practices not included in the calibration dataset. Keywords: Agroforestry buffers, Buffer placement, Modeling, Phosphorus, Practice effectiveness, Watershed discretization.

Influence of Agroforestry Buffers on Soil Hydraulic Properties Relative to Row Crop Management

Influence of Agroforestry Buffers on Soil Hydraulic Properties Relative to Row Crop Management

Evapotranspiration differences between agroforestry and grass buffer systems

Improved soil and water quality, and carbon sequestration are notable benefits of agroforestry practices compared to row-crop agriculture. Over an agricultural watershed with two buffer cropping systems (agroforestry buffers and grass buffers) soybean crop evapotranspiration was calculated from the Penman-Monteith equation using 10-min averages of meteorological measurements within crop alleys for 54days in summer 2007. Wind speeds were consistently lower over the agroforestry buffer portion of the watershed by an average of 0.42ms−1. For calculated evapotranspiration assuming water-stressed conditions, this decrease in wind speed from the presence of agroforestry buffers was offset almost entirely by an increase in net radiation. Net radiation differences between the two systems were highest during the morning (∼40Wm−2) and were likely the result of solar radiation scattered from the agroforestry buffers. Wind speed reduction over the crop portion surrounded by agroforestry buffers varied by wind direction with daytime winds ≥0.6ms−1 greater over the grass buffer portion of the crop for northerly and southerly winds (nearly perpendicular to the agroforestry buffers). Therefore, buffer orientation relative to the prevailing wind is important for reducing evapotranspiration. Changes in crop alley width would be expected to impact the portion of the crop within wind-sheltered zones and the portion receiving scattered radiation from trees. The sensitivity of evapotranspiration to agroforestry buffer orientation and crop alley width should be a focus of future investigations.

Soil quality differences in a row-crop watershed with agroforestry and grass buffers

Agroforestry buffers are believed to enhance soil quality parameters in agricultural landscapes. Soil enzyme activities, water stable aggregates (WSA), soil organic carbon (SOC), and total nitrogen (N) have been identified as good indices of soil quality. The objective of this study was to quantify soil quality differences among agroforestry buffer (AGF), grass waterway (GWW), grass buffer (GB), and row crop (RC) areas and distance from the tree base on corn (Zea mays L.)-soybean (Glycine max L.) watershed. Soil samples from AGF at 0, 30, 60, 90 cm distances from the tree base, and from AGF, GWW, GB, and RC areas were collected from summit, shoulder, and foot-slope landscape positions at the paired watershed study near Novelty, MO. Soil enzyme activity, WSA, soil C, and N were determined and data were analyzed statistically. The highest SOC and N percentages were found in AGF and the lowest in RC. β-Glucosidase activity was not significantly different among AGF, GWW, and RC. β-Glucosaminidase and dehydrogenase activities were significantly lower in RC treatment than all other treatments. Fluorescein diacetate (FDA) hydrolase activity was not significant among all treatments. WSA percentage was significantly higher in GWW and AGF as compared to others. Landscape position was not significantly different for all measured soil quality parameters. β-Glucosidase, β-glucosaminidase activities, WSA, and soil N did not differ significantly with distance from the tree base. SOC and FDA hydrolase activity were significantly lower at the tree base. Results imply that permanent vegetation has improved the soil quality by enhancing soil microbial activity and organic matter accumulation, thereby contribute positively to watershed restoration.

Water infiltration and soil water content in claypan soils influenced by agroforestry and grass buffers compared to row crop management

Agroforestry buffers have recently been introduced in temperate regions to enhance conservation of soil and water resources in row crop management. The effects of agroforestry and grass-legume buffers on in situ water infiltration relative to row crop management (RC) were assessed for a claypan soil in northeastern Missouri, USA. Infiltration rates were observed in early June in 2014 and 2015 for watersheds under corn (Zea mays L.)-soybean (Glycine max L. Merr.) management; these watersheds had agroforestry buffers (AGB) or grass buffers (GB). The dominant soil for the watersheds was Putnam silt loam (fine, smectitic, mesic Vertic Albaqualf). The watersheds were in no-till management and established in 1991 with agroforestry buffers and GBs implemented in 1997. Agroforestry buffers, 4.5 m wide and 36.5 m apart, consisted of redtop (Agrostis gigantean Roth), brome (Bromus spp.), and birdsfoot trefoil (Lotus corniculatus L.) with pin oak (Quercus palustris Menchh.), swamp white oak (Q. bicolor Willd.), and bur oak (Q. macrocarpa Michx.) trees. GBs consisted of redtop, brome, and birdsfoot trefoil. Significant differences were found among the treatments in 2014 for the sorptivity parameter for the fitted infiltration equations with the highest values for agroforestry buffers. Significantly higher saturated hydraulic conductivity values were found for the buffer treatments in 2015. Soil water content measurements were assessed over time for years 2010 and 2011 with sensors at 5, 10, 20 and 40 cm depths for the agroforestry buffer and RC areas. Water content decreased more rapidly during the summer season within agroforestry buffers relative to RC areas; however, water infiltration was higher within agroforestry buffers during the recharge period.

Soil Thermal Properties under Prairies, Conservation Buffers, and Corn–Soybean Land Use Systems

Although prairies and conservation buffers are becoming popular to improve soil properties and environmental quality, very little is known about their influence on soil thermal properties. This study compared and quantified thermal conductivity (λ), thermal diffusivity (D), and volumetric heat capacity (C) of prairies (Tucker Prairie [TP] and Prairie Fork [PF]), conservation buffers (grass buffers [GB] and agroforestry buffers [AGF]), and corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation (COS) land uses in Missouri. Core and bulk soils were collected at 10‐cm depth increments. Soil thermal properties and water characteristic curves were determined at 0, −33, −100, and −300 kPa pressures. Additionally, soil organic C (SOC) and bulk density (BD) were also determined. The results showed that SOC was negatively correlated with λ and D and positively correlated with C. Significantly higher values of SOC and lower BD were observed for AGF, TP, GB, and PF than COS. Similarly, λ and D were significantly higher and C was lower under COS than the prairies and conservation buffers. The results suggest that a greater amount of SOC decreases the thermal conductance due to the insulating characteristics of SOC and acts as a barrier to heat transport. Therefore, AGF, TP, GB, and PF had lower thermal conductance to deeper soil depths, which helps to conserve more moisture as well as assist in increasing the longevity of SOC in the soil matrix. Our results imply that buffers and perennial vegetation can help reduce heat flow by increasing the thermal capacity and thereby mitigating climate change.

Variability of soil carbon in row crop watersheds with agroforestry buffers

Good understandings of soil carbon (C) variability are important to develop mitigation strategies for global warming and for enhanced ecosystem services. The objective of this study was to examine agroforestry, corn-soybean (row crop; control) and landscape effects on variations in soil C. One-m deep soil cores were sampled from two paired watersheds under agroforestry management with buffers and corn-soybean rotations and soils were analyzed for soil C, texture, pH, and cation exchange capacity. To observe the effect of landscape positions, both agroforestry and control watersheds were divided according to the landscape positions and area. The agroforestry watershed was divided into 0–2, 3–5, and 6–9 % slope segments and control watershed into 0–2 and 3–9 % slope segments. The results showed non-significant higher values of soil C in the agroforestry watershed after 3 years of establishment compared to the control treatment. Coefficient of variation (CV) showed ranges of variability for soil C by soil depth in both watersheds. Soil C distribution under agroforestry (CV 0.19–0.31) was moderately variable whereas under control (CV 0.30–0.40) it was moderate to most variable. Significantly higher amounts of soil C were observed at lower landscape positions compared to the upper and middle positions probably due to the depositions of eroded plant materials and retention by the grass waterway. Similarly, higher soil C was observed on both watersheds where depths to the claypan were shallow. It might be due to the lower drainage and soil water movement. Establishment of agroforestry practices decreased the variability of soil C, helped increase the soil C during long run as well as helped to enhance the ecosystems services.

Use of Fuzzy rainfall–runoff predictions for claypan watersheds with conservation buffers in Northeast Missouri

Summary Fuzzy rainfall–runoff models are often used to forecast flood or water supply in large catchments and applications at small/field scale agricultural watersheds are limited. The study objectives were to develop, calibrate, and validate a fuzzy rainfall–runoff model using long-term data of three adjacent field scale row crop watersheds (1.65–4.44 ha) with intermittent discharge in the claypan soils of Northeast Missouri. The watersheds were monitored for a six-year calibration period starting 1991 (pre-buffer period). Thereafter, two of them were treated with upland contour grass and agroforestry (tree + grass) buffers (4.5 m wide, 36.5 m apart) to study water quality benefits. The fuzzy system was based on Mamdani method using MATLAB 7.10.0. The model predicted event-based runoff with model performance coefficients of r 2 and Nash–Sutcliffe Coefficient (NSC) values greater than 0.65 for calibration and validation. The pre-buffer fuzzy system predicted event-based runoff for 30–50 times larger corn/soybean watersheds with r 2 values of 0.82 and 0.68 and NSC values of 0.77 and 0.53, respectively. The runoff predicted by the fuzzy system closely agreed with values predicted by physically-based Agricultural Policy Environmental eXtender model (APEX) for the pre-buffer watersheds. The fuzzy rainfall–runoff model has the potential for runoff predictions at field-scale watersheds with minimum input. It also could up-scale the predictions for large-scale watersheds to evaluate the benefits of conservation practices.

Sulfamethazine Sorption to Soil: Vegetative Management, pH, and Dissolved Organic Matter Effects

Elucidating veterinary antibiotic interactions with soil is important for assessing and mitigating possible environmental hazards. The objectives of this study were to investigate the effects of vegetative management, soil properties, and >1000 Da dissolved organic matter (DOM) on sulfamethazine (SMZ) behavior in soil. Sorption experiments were performed over a range of SMZ concentrations (2.5-50 μmol L) using samples from three soils (Armstrong, Huntington, and Menfro), each planted to one of three vegetation treatments: agroforestry buffers strips (ABS), grass buffer strips (GBS), and row crops (RC). Our results show that SMZ sorption isotherms are well fitted by the Freundlich isotherm model (log = 0.44-0.93; Freundlich nonlinearity parameter = 0.59-0.79). Further investigation of solid-to-solution distribution coefficients () demonstrated that vegetative management significantly ( < 0.05) influences SMZ sorption (ABS > GBS > RC). Multiple linear regression analyses indicated that organic carbon (OC) content, pH, and initial SMZ concentration were important properties controlling SMZ sorption. Study of the two most contrasting soils in our sample set revealed that increasing solution pH (pH 6.0-7.5) reduced SMZ sorption to the Armstrong GBS soil, but little pH effect was observed for the Huntington GBS soil containing 50% kaolinite in the clay fraction. The presence of DOM (150 mg L OC) had little significant effect on the Freundlich nonlinearity parameter; however, DOM slightly reduced SMZ values overall. Our results support the use of vegetative buffers to mitigate veterinary antibiotic loss from agroecosystems, provide guidance for properly managing vegetative buffer strips to increase SMZ sorption, and enhance understanding of SMZ sorption to soil.

Temporal and Spatial Influence of Perennial Upland Buffers on Corn and Soybean Yields

Contour perennial buffers within cropland reduce pollutants from watersheds, but may interfere and affect crop yields at the crop‐buffer interface. The objective of this study was to evaluate the temporal and spatial effects of agroforestry (AGF) and contour grass (CGS) buffers on no‐till corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields in the claypan region of Missouri. The CGS buffers (4.5‐m width) contained redtop (Agrostis gigantean Roth), brome grass (Bromus spp.), and birdsfoot trefoil (Lotus corniculatus L.), established at 35 m spacings. The AGF buffers contained, a single row of pin oak (Quercus palustris Muenchh.), swamp white oak (Q. bicolor Willd.), and bur oak (Q. macrocarpa Michx.) trees planted at 3‐m spacings in the middle of grass strips. Mean yields of corn in 2004, 2006, and 2008 and soybean in 2005, 2007, and 2009 at distances 0 to 5 m, 5 to 10 m, 10 to 15 m, and 15 to 20 m from AGF and CGS buffers were determined using geo‐referenced yield maps and ArcGIS software. Corn yield reductions at 0 to 5 m from buffers, ranged from 22 to 49% in AGF and 15 to 32% in CGS watersheds, compared to the yield at 15 to 20 m during 2004 and 2006. This reduction may have been enhanced from soil moisture stress, late planting, and different hybrids between study years. Soybean yields were not affected by buffers. Reduction of corn yields could be potentially minimized with early planting, drought‐tolerant varieties and reduction of buffers root competition with pruning or barriers.

Soil quality indicator responses to row crop, grazed pasture, and agroforestry buffer management

Soil enzyme activities and water stable aggregates have been identified as sensitive soil quality indicators, but few studies exist comparing those parameters within buffers, grazed pastures and row-crop systems. Our objective was to examine the effects of these land uses on the activities of selected enzymes (β-glucosidase, β-glucosaminidase, fluorescein diacetate (FDA) hydrolase, and dehydrogenase), proportion of water stable aggregates (WSA), soil organic carbon and total nitrogen content. Four management treatments [grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row crop (RC)] were sampled in 2009 and 2010 at two depths (0 to 10- and 10 to 20-cm) and analyzed. Most of the soil quality indicators were significantly greater under perennial vegetation when compared to row crop treatments. Although there were numerical variations, soil quality response trends were consistent between years. The β-glucosaminidase activity increased slightly from 156 to 177 μg PNP g−1 dry soil while β-glucosidase activity slightly decreased from 248 to 237 μg PNP g−1 dry soil in GB treatment during 2 years. The surface (0–10 cm depth) had greater enzyme activities and WSA than sub-surface (10–20 cm) samples. WSA increased from 178 to 314 g kg−1 in row crop areas while all other treatments had similar values during the 2 year study. The treatment by depth interaction was significant (P < 0.05) for β-glucosidase and β-glucosaminidase enzymes in 2009 and for dehydrogenase and β-glucosaminidase in 2010. Soil enzyme activities were significantly correlated with soil organic carbon content (r ≥ 0.94, P < 0.0001). This is important because soil enzyme activities and microbial biomass can be enhanced by perennial vegetation and thus improve several other soil quality parameters. These results also support the hypothesis that positive interactions among management practices, soil biota and subsequent environmental quality effects are of great agricultural and ecological importance.