Nitrogen limits crop production when insufficient and harms the environment when excessive. Tailoring N inputs to cropping systems remains a high priority to achieve production and environmental goals. We collected soils from 47 corn (Zea mays L.) production fields in North Carolina and Virginia at depths of 0 to 10, 10 to 20, and 20 to 30 cm and evaluated soil C and N characteristics in association with soil N mineralization. Soil organic C at a depth of 0 to 10 cm varied among sites from ~10 to 80 g kg -1 , and generally declined with depth because of many sites with no-tillage management. N itrogen (N) is considered the most limiting nutrient in plant production. In many cases, demand for N by highly productive crops far exceeds the N that can be supplied by soil. Sources of N from soil are residual inorganic N from previous cropping or organic forms of N in soil organic matter and plant and animal residues, which must be mineralized in synchrony with decomposition processes. Insufficient N leads to low biomass production as a result of limited protein synthesis and low photosynthetic activity, all of which causes cascading negative effects on water-use efficiency, biological activity, ecosystem functioning, economic return from farm capital investment, and social welfare of farming communities (Smil, 2002;Tilman et al., 2011). In contrast, excessive N leads to susceptibility of crops to invasion by pests, leakage of N from the soil and plant systems to the environment causing air and water pollution, and loss of investment from costly inorganic N inputs (Vitousek et al., 1997;Hatfield and Follett, 2008).Nitrogen availability in soils has been investigated for decades (Waksman and Starkey, 1924;Fribourg and Bartholomew, 1956;Stanford, 1968;Jenkinson and Powlson, 1976;Jansson and Persson, 1982;Campbell et al., 1991), yet reliable predictions of N fertilizer application rate to optimize cereal grain yields have been elusive (Balkcom et al., 2003). Early investigations to optimize inorganic N inputs focused on defining potentially mineralizable N from a nonlinear function derived from inorganic N released through successive leaching and incubation (Stanford and Smith, 1972). This methodology has been considered the best estimate of soil N mineralization potential, despite (i) the long time period for evaluation (32 wk Core Ideas• Soil nitrogen mineralization can be predicted with the flush of CO 2 .• Soil texture does not alter the relationship between the flush of CO 2 and N mineralization.• Large quantity of mineralizable N in surface soils is possible with conservation management.• The flush of CO 2 is an appropriate indicator for soil-test biological activity.• The flush of CO 2 is a rapid and reliable indicator of soil N availability.

Agritourism—visiting a working farm for education or recreation—may serve as a tool to increase local food consumption as it often includes opportunities to purchase local food on-site. Yet, the influence of agritourism on consumers’ local food purchasing behavior remains underexplored. Thus, this study measures the impact of agritourism experiences on consumers’ intentions to purchase local food. To do so, visitors were surveyed at six agritourism farms with similar agritourism activities (e.g., U-pick, educational displays, and on-site market) located across North Carolina (USA) before (pre) and after (post) their visits ( n = 328). Data, collected during the 2018–2019 peak agritourism season, were analyzed using repeated measures multivariate analysis of variance. Findings indicate that agritourism experiences effectively increase consumers’ intentions to purchase local food. These findings advance the scholarship of agritourism. They also provide useful information to design effective marketing campaigns to promote the purchase and consumption of local food and strengthen local agricultural systems.

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Arbuscular mycorrhizal fungi (AMF) can perform key roles in ecosystem functioning through improving host nutrient acquisition. Nitrogen (N) is an essential nutrient for plant growth, however, anthropogenic N loading (e.g. crop fertilization and deposition from combustion sources) is increasing so that N now threatens ecosystem sustainability around the world by causing terrestrial and aquatic eutrophication and acidification. It is important to better understand the capacity of AMF to directly uptake N from soils and transfer it to host plants because this process may increase N recycling and retention within ecosystems. In addition to understanding the role of AMF in the N cycle in the present day it is important to understand how AMF function may change as global change proceeds. Currently the net effects of N enrichment and elevated temperature predicted with global change on AMF are unknown. In this study, we examined the effects of N enrichment by simulated Ndeposition loading, elevated temperatures expected by future global changes and their interactions on growth and AMF-mediated N acquisition of switchgrass (Panicum virgatum var. Alamo), an important species for biofuel production. Switchgrass plants were grown in microcosm units that divided mycorrhizal roots from AMF hyphae and organic residues enriched with 15 N by compartments separated by an air gap to reduce N diffusion. While AMF did not enhance switchgrass biomass, mycorrhizas significantly increased 15 N in shoots and total shoot N. Neither N enrichment nor elevated temperatures influenced this mycorrhizal-mediated N uptake and transfer. Results from this study can aid in developing sustainable bioethanol and switchgrass production practices that are less reliant on synthetic fertilizers and more dependent on internal N recycling from AMF.

Arbuscular mycorrhizas can alter competitive interactions between plants that markedly differ in their dependence upon mycorrhizas, but little is known about how mycorrhizas affect intra- and inter-specific competition between similarly dependent plant species. We conducted competition experiments in pots between all pairs of the similarly facultatively mycotrophic crop species, chili ( Capsicum annuum L.), maize ( Zea mays L.), and zucchini ( Cucurbita pepo L.). We used a two-species yield-density model to analyze the separate effects of mycorrhizal inoculation, intra-, and inter-specific density on biomass responses. Mycorrhizas reduced the growth of all three plant species. Intraspecific competition increased the negative effect of mycorrhizas, as did interspecific competition at low intraspecific density. At high intraspecific density, however, interspecific competition improved plant responsiveness to mycorrhizas. Enhancement of plant benefit from mycorrhizas at high interspecific density of competing, weakly mycorrhiza-dependent species may help to explain the evolutionary maintenance of their associations with mycorrhizal fungi, and may be a key to understanding intercrop combinations that exceed the monoculture yields of component species.

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Commelina benghalensis(Benghal dayflower) is a noxious weed that is invading agricultural systems in the southeastern United States. We investigated the influences of nutrition, light, and photoperiod on growth and reproductive output ofC. benghalensis. In the first experimental series, plants were grown under high or low soil nutrition combined with either full light or simulated shade. Lowered nutrition strongly inhibited vegetative growth and aboveground spathe production. Similar but smaller effects were exerted by a 50% reduction in light, simulating conditions within a developing canopy. In the second series of experiments,C. benghalensisplants were exposed to different photoperiod conditions that produced short- and long-day plants growing in similar photosynthetic periods. A short-day photoperiod decreased time to flowering by several days and led to a 40 to 60% reduction in vegetative growth, but reproduction above and below ground was unchanged. Collectively, the results indicate that (1) fertility management in highly weathered soils may strongly constrain competitiveness ofC. benghalensis; (2) shorter photoperiods will limit vegetative competitiveness later in the growing seasons of most crops; and (3) the high degree of reproductive plasticity and output possessed byC. benghalensiswill likely cause continual persistence problems in agricultural fields.

Many abiotic factors, such as mineral nutrients—including phosphorus (P)—fertility, can impact the yield and growth of Cannabis sativa. Given the economic portion of C. sativa is the inflorescence, the restriction of P fertility could impact floral development and quality could be detrimental. This study sought to track the impacts of varying P concentrations (3.75, 7.50, 11.25, 15.0, 22.50, and 30.0 mg·L−1) utilizing a modified Hoagland’s solution. This experiment examined plant height, diameter, leaf tissue mineral nutrient concentrations, and final fresh flower bud weight as well as floral quality metrics, such as cannabinoids and terpenes. The results demonstrated that during different life stages (vegetative, pre-flowering, flowering), P concentrations impact C. sativa growth and development and yield. Regarding the cannabinoid pools, results varied for the individual cannabinoid types. For the acid pools, increasing fertility concentrations above 11.25 mg·L−1 P did not result in any increase in cannabinoid concentrations. These results indicate that, if a crop is being produced under greenhouse conditions, specifically for cannabinoid production, an excessive P supply did not result in higher cannabinoid production. However, plants grown with a higher rate of P fertility (30.0 mg·L−1) had greater plant width and may result in more buds per plant.