Alley cropping practices are highly diverse and range from simple to complex. Plantings can consist of a single tree species or any multiple of species. Pruning requirements under alley cropping vary greatly, depending on the short- and long-term objectives of the practice. A primary goal in most alley cropping practices, however, is to optimize the economic gain; thus, artificial pruning is often an important consideration. Both the timing of thinnings and the number of trees to be removed in alley cropping varies greatly with species, site conditions, and management objectives. Forage, row crop, and specialty-crop species used in alley cropping practices range from shade tolerant to shade intolerant. Most of today's agroforesters design their alley cropping practices with an eye to the future; although the companion crop may change with time, the goal is to always have one or more companion crops present to diversify an operation while optimizing financial gain.

Annual screenings of forage grasses and legumes for shade tolerance were conducted from 1996 to 2001 in the outdoor Shade Tolerance Screening Laboratory at the Horticulture and Agroforestry Research Center, University of Missouri. Forty-three forages were grown under non-shade (100% of full sunlight), moderate shade (45%), and dense shade (20%) without competition for water and nutrients. Annual forage yield (g pot−1) was equal to or higher under moderate shade for all 43 forages and under dense shade for 31 forages than the non-shade control. Relative distance plasticity index (RDPI), a measure of a species’ adaptability to different environments, ranged from 0.104 to 0.567. Cool season grasses had the lowest RDPI (0.183), followed by warm season grasses (0.252), warm season legumes (0.274), and cool season legumes (0.314), indicating grasses tend to be more shade tolerant than legumes in terms of forage yield. Overall, most grass and legume forages have the potential to produce equivalent or higher yields in agroforestry practices featuring light to moderate shade than forages in open pastures when competition from tree roots is minimized.

Benefits of repeated air-root-pruning of seedlings when stepping up to progressively larger containers include excellent lateral root distribution immediately below the root collar and an exceptionally fibrous root ball. To evaluate long-term field performance of repeatedly air-root-pruned container stock, three plantings of swamp white oak (Quercus bicolor Willd.) 10 to 13 years old were located that also included bareroot planting stock. Initial and final stem diameter and height and above-ground green weights were determined on randomly selected trees at each site. On a site with a sandy, excessively drained, high pH soil, trees (age 10) from container stock were 1.5 times taller, 2.3 times larger in dbh, and 2.8 times greater in green weight than trees from bareroot stock which averaged only 2.9 m tall, 3.9 cm dbh, and 16.3 kg green weight. On a site with high clay, poor internal drainage, and frequent flooding, trees (age 12) from container stock were 1.4 times taller, 1.8 times larger in dbh, and 4.1 times greater in green weight than trees from bareroot stock which averaged 4 m tall, 7.3 cm dbh, and 28 kg green weight. On an upland site with deep loess soils, there was a trend for trees (age 13) from container stock to be only slightly larger than trees from bareroot stock with each stock type averaging 9.6 m tall, 20 cm dbh, and 177 kg green weight. Repeated air-root pruning produced lateral roots immediately below the root collar that resulted in large container stock with large well-balanced root systems that were competitive on harsh or less than ideal oak sites. Although the process is relatively labor intensive, propagation of repeatedly air-root-pruned container stock is readily adaptable internationally to locally available sources of organic matter and open-bottom containers.

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.

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.

INTRODUCTION: The percentage of water stable aggregates (WSA) is a measure of resistance to breakdown by water and mechanical activities. Water stable aggregates improve soil water and air movement. Macro-aggregates (diam. > 250 m) are considered as a secondary soil structure associated with pores, microbial habitat, and physical protection of organic matter (Christensen, 2001; Carter, 2004). Aggregates provide spatially differentiated habitats for microorganisms and are important for biogeochemical soil processes (Park and Smucker, 2005).

Despite improvements in the use of soil conservation practices, crop rotation and nutrient management programs, significant concern still exists regarding soil erosion and nutrient losses in runoff from row crop production. In the US, states are required to implement water quality standards based on USEPA guidelines or other scientifically defensible methods (Ice and Binkley, 2003). Agroforestry has recently been suggested as an alternative to traditional row crop production in the temperate zone that also generates additional environmental and economic benefits (Gold and Hanover, 1987). It is hypothesized that incorporation of agroforestry practices would improve soil physical properties and thus reduce runoff, sediment, and nutrient losses from row crop agricultural watersheds. However, the effects of agroforestry and grass buffer strips, on soil pore parameters, saturated hydraulic conductivity, and soil bulk density have not been extensively studied for surface and subsurface soils in temperate regions on a watershed scale.

Silvopasture-the integration of trees, forage, and livestock can be established by planting trees in existing pastures. Successful tree establishment and acceptable tree growth in existing tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] pastures requires a vegetation-free zone near the tree base. This study was conducted to determine how large a vegetation-free zone was necessary for the establishment of black walnut (Juglans nigra L.) in tall fescue pastures. Half-sib black walnut seeds were planted in seven different-sized vegetation-free zones [0.0 (control), 0.3, 0.6, 0.9, 1.2, 1.5, and 1.8 m radii] that were created and maintained by applying glyphosate. The study included two consecutive planting years at two locations, one in central Missouri and another in north-central Missouri. The central Missouri site was underlain with well drained, deep soil while the other site was underlain with a poorly drained soil with a defined argillic horizon. Tree height growth was greatest in 0.9-m or larger vegetation-free zones. Diameter growth was greatest in 1.2-m vegetation-free zones and larger. The results suggest that a minimum of a 1.2-m vegetation-free zone in tall fescue pastures should be used to maximize black walnut height and diameter growth in the critical first years of tree establishment.

In this study, we report the results of a comparison of 5-year survival and 14-year growth of black, white, and swamp white oaks grown from planting stock produced by a conventional bareroot method and stock produced by the Root Production Method (RPM (R)) of Forrest Keeling Nursery. Five-year survival was 100% for black and white oak grown from RPM (R) stock, but only 63 and 75%, respectively, for trees grown from bareroot stock. The odds ratio for survival of RPM (R) planting stock of black and white oaks compared to bareroot stock were 21.9 and 12.1, respectively. All swamp white oak survived. After 14 years, diameter growth was greater for the RPM (R) than bareroot planting stock and ranged from a 35% increase in black oak to a 6% increase in swamp white oak. Average aboveground fresh weight for trees from RPM (R) planting stock equaled 530 lb compared to 333 lb for trees from bareroot seedlings (P < 0.0001). Compared with traditional bareroot seedlings, survival and growth of RPM (R) oak planting stock was greater through 14 years.

Agroforestry has been practiced in the United States since the 1930s in the form of windbreaks; however, science-based agroforestry research and practice gained attention only in the1970s. Even then, the progress of agroforestry and its acceptance by practitioners, farmers, and policy makers were hindered by the paucity of hard evidence to support the practice. The scientific foundation that has been laid, over the past decade in particular, has elevated agroforestry’s role as an integral component of a multifunctional working landscape in the United States. Recent trends in the agriculture sector necessitate farm diversification as an essential strategy for economic competitiveness in a global market. The realization that agroforestry systems are well suited for diversifying farm income while providing environmental services and ecosystem benefits has increased receptivity on the part of some landowners. Agroforestry systems offer great promise for the production of biomass for biofuel, specialty and organic crops, pasture-based dairy, and beef, among others. Agroforestry also offers proven strategies for carbon sequestration, soil enrichment, biodiversity conservation, and air and water quality improvement not only for the landowners or farmers but for society at large. The USDA Agroforestry Strategic Framework released in 2011 identifies agroforestry as an important component of a much-needed national strategy to “enhance America’s agricultural landscapes, watersheds, and rural communities.” Minor shifts in national agricultural policy can serve to catalyze the growth of agroforestry further. In an era of environmental sustainability and green business, the realization that agroforestry is an environmentally sound, ecologically sustainable, and economically viable alternative to traditional farming will propel its adoption to newer heights in the coming decades.

The efficacy of vegetative buffer strips (VBS) in removing herbicides deposited from surface runoff is related to the ability of plant species to promote rapid herbicide degradation. A growth chamber study was conducted to compare C-atrazine (ATR) degradation profiles in soil rhizospheres from different forage grasses and correlate ATR degradation rates and profiles with microbial activity using three soil enzymes. The plant treatments included: (i) orchardgrass ( L.), (ii) smooth bromegrass ( Leyss.), (iii) tall fescue ( Schreb.), (iv) Illinois bundle flower (), (v) perennial ryegrass ( L.), (vi) switchgrass ( L.), and (vii) eastern gamagrass (). Soil without plants was used as the control. The results suggested that all plant species significantly enhanced ATR degradation by 84 to 260% compared with the control, but eastern gamagrass showed the highest capability for promoting biodegradation of ATR in the rhizosphere. More than 90% of ATR was degraded in the eastern gamagrass rhizosphere compared with 24% in the control. Dealkylation of atrazine strongly correlated with increased enzymatic activities of β-glucosidase (GLU) ( = 0.96), dehydrogenase (DHG) ( = 0.842), and fluorescein diacetate (FDA) hydrolysis ( = 0.702). The incorporation of forage species, particularly eastern gamagrass, into VBS designs will significantly promote the degradation of ATR transported into the VBS by surface runoff. Microbial parameters widely used for assessment of soil quality, e.g., DHG and GLU activities, are promising tools for evaluating the overall degradation potential of various vegetative buffer designs for ATR remediation.

Despite increased attention and demand for the adoption of agroforestry practices throughout the world, rigorous long-term scientific studies confirming environmental benefits from the use of agroforestry practices are limited. The objective was to examine nonpoint-source pollution (NPSP) reduction as influenced by agroforestry buffers in watersheds under grazing and row crop management. The grazing study consists of six watersheds in the Central Mississippi Valley wooded slopes and the row crop study site consists of three watersheds in a paired watershed design in Central Claypan areas. Runoff water samples were analyzed for sediment, total nitrogen (TN), and total phosphorus (TP) for the 2004 to 2008 period. Results indicate that agroforestry and grass buffers on grazed and row crop management sites significantly reduce runoff, sediment, TN, and TP losses to streams. Buffers in association with grazing and row crop management reduced runoff by 49 and 19%, respectively, during the study period as compared with respective control treatments. Average sediment loss for grazing and row crop management systems was 13.8 and 17.9 kg ha yr, respectively. On average, grass and agroforestry buffers reduced sediment, TN, and TP losses by 32, 42, and 46% compared with the control treatments. Buffers were more effective in the grazing management practice than row crop management practice. These differences could in part be attributed to the differences in soils, management, and landscape features. Results from this study strongly indicate that agroforestry and grass buffers can be designed to improve water quality while minimizing the amount of land taken out of production.

Water content reflectometers allow temporal and continuous assessment of spatial differences in soil water dynamics. We hypothesized that volumetric soil water content estimated by the water content reflectometers (CS616 Campbell Sci. Inc., Logan, UT) is influenced by clay content and temperature and therefore site- and or soil-specific equations are required for accurate estimations of soil water. Objectives of the study were to develop calibration equations and to evaluate soil water dynamics for an agroforestry system using the improved calibration equation. Putnam silt loam (fine, smectitic, mesic Vertic Albaqualfs) and Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs) soils were selected with 23–54% clay. Soils were packed in cylinders and sensors were monitored at 5, 10, 15, 20, 25, 30, 35, and 40°C. Calibration equations for volumetric water content (θ v ) as a function of sensor measured period, temperature, and clay content were developed. Coefficient of determination (r2) and root mean square error (RMSE) were used to compare goodness of fit. RMSE varied between 0.028 and 0.040 m3 m−3 for soil specific and soil-combined linear and quadratic equations with period. Coefficients of determination ranged between 0.89 and 0.96 for these calibrations. RMSE decreased and r2 increased as temperature was included. The effect of temperature varied with water content, with the strongest effect at high water contents. Clay content did not contribute significantly to improve predictability. Water content estimated by the linear calibration equation with period and temperature showed differences in θ v influenced by vegetation and soil depth, and closely followed precipitation events and water use by vegetation. The field study showed significant differences between the two treatments. Also the importance of temperature correction is emphasized during periods with large diurnal fluctuations and site specific calibration equations. Results of the study showed that water content reflectometers can be used to estimate θ v with less than ±4% error and may need site specific calibration and a temperature correction to research more precise estimates.

Multiple species vegetative buff er strips (VBSs) have been recommended as a cost-effective approach to mitigate agrochemical transport in surface runoff derived from agronomic operations, while at the same time offering a broader range of long-term ecological and environmental benefits. However, the effect of VBS designs and species composition on reducing herbicide and veterinary antibiotic transport has not been well documented. An experiment consisting of three VBS designs and one continuous cultivated fallow control replicated in triplicate was conducted to assess effectiveness in reducing herbicide and antibiotic transport for claypan soils. The three VBS designs include (i) tall fescue, (ii) tall fescue with a switchgrass hedge barrier, and (iii) native vegetation (largely eastern gamagrass). Rainfall simulation was used to create uniform antecedent soil moisture content in the plots and to generate runoff. Our results suggested that all VBS significantly reduced the transport of dissolved and sediment-bound atrazine, metolachlor, and glyphosate in surface runoff by 58 to 72%. Four to 8 m of any tested VBS reduced dissolved sulfamethazine transport in the surface runoff by more than 70%. The tall fescue VBS was overall most effective at reducing dissolved tylosin and enrofloxacin transport in the runoff (>75%). Th e developed exponential regression models can be used to predict expected field-scale results and provide design criteria for effective field implementation of grass buffers. Our study has demonstrated that an optimized VBS design may achieve desired agrochemical reductions and minimize acreage removed from crop production.

The detection of veterinary antibiotics (VAs) in drinking water resources resulting from manure disposal operations has raised public health concerns. Previous studies have demonstrated the benefits of using multispecies vegetated buffer strips (VBS) to reduce agrichemical transport from agroecosystems. However, VA fate and subsequent effects of VAs on microbial activities in the root zone ofVBS have not been well documented. A growth chamber study was conducted to investigate dissipation of two commonly administered VAs, sulfamethazine (SMZ) and tetracycline (TC), and the relationship between VA dissipation and soil enzyme activities in the root zone of selected plant species. Switchgrass, eastern gammagrass, orchardgrass, and a hybrid poplar tree were grown in pots containing a Mexico silt loam/sand mixture for 3 mo, followed by plant biomass removal and collection of root zone soil. Radiolabeled (3H) SMZ or TC was applied to the soils and samples were incubated in the dark for 5 wk. Among the plant species studied, hybrid poplar showed enhanced capability for promoting SMZ dissipation. The half-lives of SMZ in soil planted to the poplar tree were significantly reduced by the enhanced enzymatic activity. Comparison of soil enzymatic activities between the antibiotic treatments revealed that fluorescein diacetate hydrolytic and glucosaminidase enzyme activities were significantly lower in TC-treated soils than in SMZ-treated soils. The beta-glucosidase activities were similar between the two VA treatments. Correlation analyses showed that the half-life of SMZ in the soil was negatively correlated with enzymatic activity. Enhanced SMZ dissipation in soil planted to hybrid poplar suggests that incorporation of this plant species in VBS may mitigate deleterious effects of SMZ in the environment.