Greg D. Hoyt

Effects of Production Practices on Soil-Borne Entomopathogens in Western North Carolina Vegetable Systems

Abstract Populations of endemic soil entomopathogens (nematodes and fungi) were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC. Two tillage types (conventional plow and disk versus conservation tillage), two input approaches (chemically versus biologically based), and two cropping schedules (continuous tomato versus 3-yr rotation of corn, cucumber, cabbage, and tomato) were employed in large plots from 1995 to 1998. A Galleria mellonella (L.) trap bioassay was used to identify and monitor activity of Steinernema carpocapsae, Heterorhabditis bacteriophora, Beauveria bassiana, and Metarhizium anisopliae populations during the vegetable growing season (April–September). Seasonal detection of entomopathogens was significantly higher in conservation compared with conventional tillage systems. The strip-till operation did not affect levels of detection of S. carpocapsae. Pesticide use significantly reduced detection of entomopathogenic fungi. Type of ground cover significantly affected temperature in the upper 12 cm of soil; highest soil temperatures were observed under black plastic mulch and bare ground, whereas lowest temperatures were observed under rye mulch and clover intercrop. The high soil temperatures associated with certain ground covers may have reduced entomopathogen detection or survival. Although type of tillage appeared to be the primary factor affecting survival of endemic soil entomopathogens in our system, other factors, such as pesticide use and type of ground cover, can negate the positive effects of strip-tillage.

Effects of production system on vegetable arthropods and their natural enemies

Abstract Populations of foliar insect pests and natural enemies were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC, USA. Two types of tillage (conventional plow and disk, strip-tillage), two input approaches (chemically-based, biologically-based) and two cropping schedules (continuous tomato ( Lycopersicon esculentum Mill.), 3-year rotation of corn ( Zea mays L.), cucumber ( Cucumis sativus L.) and tomato) were employed from 1995 to 1998. Tomato pest pressure was relatively low in all years, resulting in a limited impact of production systems on potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae), and its associated parasitoids and predators. Thrips ( Frankliniella spp. (Thysanoptera)) populations were significantly higher in the biological input treatments in 3 of 4 years. Lepidopterous (primarily Helicoverpa zea Boddie (Lepidoptera: Noctuidae)) damage on tomato was significantly higher in biological treatments in all years, damage by thrips and pentatomids (Hemiptera: Pentatomidae) increasing each year in the continuous tomato crop schedule. Most insect populations were significantly influenced by type of insecticide input or ground cover. Few population measurements were affected by tillage type. Foliar insect problems in commercial vegetable production may be associated predominantly with insecticide input (i.e. more damage with biologically based insecticides) and use of intercropping (i.e. more damage in systems with living mulch); however, the long term effects of tillage and crop rotation remain to be seen.

Effects of vegetable production system on epigeal arthropod populations

Abstract Populations of epigeal arthropods were monitored in vegetable production systems under varying degrees of sustainable agricultural practices in Fletcher, NC (USA). Two tillage types (conventional plow and disk, strip-tillage (ST)), two input approaches (chemically based, biologically based) and two cropping schedules (continuous tomato Lycopersicon esculentum Mill.], 3-year rotation of sweet corn [Zea mays L.]/cabbage [Brassica oleracea L.], cucumber [Cucumis sativus L.]/cabbage and tomato) were employed from 1995–1998. A second study with tomatoes was performed in 1997–1998 to separate effects of pesticide use, intercropping and herbicide application. Pitfall traps (48-h sample period) were used at ∼25-day intervals to monitor relative activity of carabid beetles (Coleoptera: Carabidae), staphylinid (Coleoptera: Staphylinidae) beetles and lycosid spiders (Araneidae: Lycosidae). Carabids and lycosids appeared to be more active in systems with ground cover. Trap catches of carabid species were not significantly affected by insecticide input, but trap catches of lycosids were lower in plots with conventional insecticide use. No consistent effect of tillage was found over time, although Scarites spp. were more active in minimally disturbed habitats in 1998. Two distinct patterns of seasonal activity were observed for carabid beetles and lycosid spiders. Ground cover generally enhanced abundance of carabids and lycosids, while tillage type, pesticide use and crop rotation had different effects.

Cover crop nitrogen availability to conventional and no‐till corn: Soil mineral nitrogen, corn nitrogen status, and corn yield

Abstract Understanding seasonal soil nitrogen (N) availability patterns is necessary to assess corn (Zea mays L.) N needs following winter cover cropping. Therefore, a field study was initiated to track N availability for corn in conventional and no‐till systems and to determine the accuracy of several methods for assessing and predicting N availability for corn grown in cover crop systems. The experimental design was a systematic split‐split plot with fallow, hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), wheat (Triticum aestivum L.), rye+hairy vetch, and wheat+hairy vetch established as main plots and managed for conventional till and no‐till corn (split plots) to provide a range of soil N availability. The split‐split plot treatment was sidedressed with fertilizer N to give five N rates ranging from 0–300 kg N ha‐1 in 75 kg N ha‐1 increments. Soil and corn were sampled throughout the growing season in the 0 kg N ha‐1 check plots and corn grain yields were determined in all plots. Plant‐available N was greater following cover crops that contained hairy vetch, but tillage had no consistent affect on N availability. Corn grain yields were higher following hairy vetch with or without supplemental fertilizer N and averaged 11.6 Mg ha‐1 and 9.9 Mg ha‐1 following cover crops with and without hairy vetch, respectively. All cover crop by tillage treatment combinations responded to fertilizer N rate both years, but the presence of hairy vetch seldom reduced predicted fertilizer N need. Instead, hairy vetch in monoculture or biculture seemed to add to corn yield potential by an average of about 1.7 Mg ha‐1 (averaged over fertilizer N rates). Cover crop N contributions to corn varied considerably, likely due to cover crop N content and C:N ratio, residue management, climate, soil type, and the method used to assess and assign an N credit. The pre‐sidedress soil nitrate test (PSNT) accurately predicted fertilizer N responsive and N nonresponsive cover crop‐corn systems, but inorganic soil N concentrations within the PSNT critical inorganic soil N concentration range were not detected in this study.

Cover Crop Management Affects Weeds And Yield in Organically Managed Sweetpotato Systems

A 3-yr field experiment was initiated in 2001 to evaluate weed suppression and sweetpotato productivity in three organic sweetpotato production systems. Organic systems were (1) compost and no cover crop with tillage (Org-NC), (2) compost and a cover crop mixture of hairy vetch and rye incorporated before transplanting (Org-CI), and (3) compost and the same cover crop mixture with reduced tillage (Org-RT). A conventional system with tillage and chemical controls (Conv) was included for comparison. Suppression of monocot and dicot weed density and biomass was similar between Org-NC and Org-CI each year, and were frequently similar to Conv. Org-RT was as effective as Org-NC in controlling dicot weed density and biomass each year, but did not suppress monocot weeds. At sweetpotato harvest, an increase in cover crop surface residue biomass in Org-RT was associated with a decrease in cumulative total weed density (R2 = 0.43, P = 0.0001); however, the amount of that residue was insufficient to suppress late-emerging monocot weeds. Total sweetpotato yield in Org-RT was at least 45% lower than other systems in 2002 and was most likely due to an increase in monocot weed density and biomass concurrent with a decrease in sweetpotato vine biomass. Total sweetpotato yield was similar among all systems in 2001 and 2004; the exception was lowest yields obtained in the Org-RT system in 2002. Organically managed sweetpotato with or without an incorporated cover crop produced sweetpotato yields equal to conventionally managed systems despite difficulties controlling weeds that emerged later in the season. Nomenclature: EPTC; napropamide; hairy vetch, Vicia villosa Roth; rye, Secale cereale L. ‘Wrens Abruzzi’; sweetpotato, Ipomoea batatas (L.) Lam. ‘Beauregard’.

Eastern black nightshade (Solanum ptycanthum) reproduction and interference in transplanted plasticulture tomato

Abstract Studies were conducted to determine the effect of in-row eastern black nightshade establishment and removal timings in plasticulture tomato on tomato yield loss and nightshade berry production and seed viability. Eastern black nightshade was transplanted at 1, 2, 3, 4, 5, 6, and 12 wk after tomato planting (WAP) and remained until tomato harvest, or was established at tomato planting and removed at 2, 3, 4, 5, 6, 8, and 12 WAP to determine the critical weed-free periods. Eastern black nightshade seed viability increased with berry size and with length of establishment or removal time. The critical weed-free period to avoid viable nightshade seed production was 3–6 WAP. Tomato yield decreased with early weed establishment or with delayed time of weed removal. The critical weed-free period to avoid greater than 20% tomato yield loss for the sum weight of extra large and jumbo grades was 28 to 50 d after tomato transplanting. Nomenclature: Eastern black nightshade, Solanum ptycanthum Dun. SOLPT; tomato, Lycopersicon esculentum.

Comparison of Surface Water Quality and Yields from Organically and Conventionally Produced Sweet Corn Plots with Conservation and Conventional Tillage

Organic agricultural systems are often assumed to be more sustainable than conventional farming, yet there has been little work comparing surface water quality from organic and conventional production, especially under the same cropping sequence. Our objective was to compare nutrient and sediment losses, as well as sweet corn ( L. var. ) yield, from organic and conventional production with conventional and conservation tillage. The experiment was located in the Appalachian Mountains of North Carolina. Four treatments, replicated four times, had been in place for over 18 yr and consisted of conventional tillage (chisel plow and disk) with conventional production (CT/Conven), conservation no-till with conventional production (NT/Conven), conventional tillage with organic production (CT/Org), and conservation no-till with organic production (NT/Org). Water quality (surface flow volume; nitrogen, phosphorus, and sediment concentrations) and sweet corn yield data were collected in 2011 and 2012. Sediment and sediment-attached nutrient losses were influenced by tillage and cropping system in 2011, due to higher rainfall, and tillage in 2012. Soluble nutrients were affected by the nutrient source and rate, which are a function of the cropping system. Sweet corn marketable yields were greater in conventional systems due to high weed competition and reduced total nitrogen availability in organic treatments. When comparing treatment efficiency (yield kg ha /nutrient loss kg ha ), the NT/Conven treatment had the greatest sweet corn yield per unit of nutrient and sediment loss. Other treatment ratios were similar to each other; thus, it appears the most sustainably productive treatment was NT/Conven.

A survey of cover crop practices and perceptions of sustainable farmers in North Carolina and the surrounding region

The environmental benefits of cover cropping are widely recognized but there is a general consensus that adoption levels are still quite low among US farmers. A survey was developed and distributed to more than 200 farmers engaged in two sustainable farming organizations in NC and the surrounding region to determine their level of utilization, current practices and perceptions related to cover cropping. The majority of farms surveyed had diverse crop production, production areas <8 ha, and total gross farm incomes <US

Long-term no-tillage and organic input management enhanced the diversity and stability of soil microbial community

50,000. Approximately one-third of the survey population had an organic production component. Eighty-nine percent of participants had a crop rotation plan and 79% of the total survey population utilized cover cropping. More than 25 different cool- and warm-season cover crops were reported. The statements that generated the strongest agreement about cover crop benefits were that cover crops: increase soil organic matter, decrease soil erosion, increase soil moisture, contribute nitrogen to subsequent cash crops, suppress weeds, provide beneficial insect habitat and break hard pans with their roots. Economic costs associated with cover cropping were not viewed as an obstacle to implementation. A factor analysis was conducted to identify underlying themes from a series of positive and negative statements about cover crops. Pre- and post-management challenges were able to explain the most variability (30%) among participant responses. Overall, participants indicated that the incorporation of residues was their greatest challenge and that a lack of equipment, especially for no-till systems, influenced their decisions about cover cropping. Farmers did not always appear to implement practices that would maximize potential benefits from cover crops.

ASSESSMENT OF BURLEY TOBACCO NITROGEN NEEDS FOLLOWING COVER CROPPING AND MANURE APPLICATION

Intensive tillage and high inputs of chemicals are frequently used in conventional agriculture management, which critically depresses soil properties and causes soil erosion and nonpoint source pollution. Conservation practices, such as no-tillage and organic farming, have potential to enhance soil health. However, the long-term impact of no-tillage and organic practices on soil microbial diversity and community structure has not been fully understood, particularly in humid, warm climate regions such as the southeast USA. We hypothesized that organic inputs will lead to greater microbial diversity and a more stable microbial community, and that the combination of no-tillage and organic inputs will maximize soil microbial diversity. We conducted a long-term experiment in the southern Appalachian mountains of North Carolina, USA to test these hypotheses. The results showed that soil microbial diversity and community structure diverged under different management regimes after long term continuous treatments. Organic input dominated the effect of management practices on soil microbial properties, although no-tillage practice also exerted significant impacts. Both no-tillage and organic inputs significantly promoted soil microbial diversity and community stability. The combination of no-tillage and organic management increased soil microbial diversity over the conventional tillage and led to a microbial community structure more similar to the one in an adjacent grassland. These results indicate that effective management through reducing tillage and increasing organic C inputs can enhance soil microbial diversity and community stability.