No description available.

No description available.

No description available.

Food production security and resiliency require combination of agricultural management practices that are environmentally friendly and economically viable. Cover crops and tillage are two typical management practices that influence corn (Zea mays L.) and soybean (Glycine max L.) production in Illinois and the Midwest, USA. Finding practices that could potentially reduce nitrous oxide (N2O) emissions and sequester carbon (C) in the soil can improve agricultural resiliency to climate change. Generally, shifting from reduced tillage (RT) to no-till (NT) improves soil structure and decreases C emissions or sequesters soil C but might increase N2O emissions. Including a legume cover crop such as hairy vetch (Vicia villosa L.) before corn is preferred to winter cereal cover crops (WCCCs) to avoid yield penalty in corn and ensure high grain production. Winter cereal cover crops such as winter cereal rye (Secale cereale) (WCR) could potentially decrease soil N2O emissions during fallow period by capturing residual N and reducing soil moisture. These conditions could change in soils with legacy tillage (RT vs. NT) effects due to changes in soil physical, chemical, and biological over time. We utilized a medium-term (six-year-old) trial to test several hypotheses. We hypothesized that RT increases the soil temperature, accelerates soil organic matter mineralization, and especially in combination with hairy vetch could increase soil N in the soil leading to increased corn grain yield and N2O emission (Chapter 1). We also hypothesized that WCR takes up residual N after harvesting corn, decrease soil N, use soil moisture, and therefore, could decrease soil N2O emission (Chapter 2). For study 1 (Chapter 1), our objective was to evaluate the influence of cover crop (hairy vetch) vs. a no CC control and tillage systems (RT vs. NT) on (i) corn yield, N uptake, removal, and N balance; (ii) N2O emissions during corn season; (iii) yield scaled N2O emissions on a long-term (eight years) tillage × cover cropping system during the corn growing season in 2019 and 2021. We also analyzed factors that influence N2O emissions via principal component analysis in corn season. In corn growing seasons, we found that corn grain yield was higher in RT than NT reflecting on more N in the soil in RT than NT. Hairy vetch increased corn grain yield, soil N, and N2O-N indicating increased corn grain yield by hairy vetch N contribution let to higher N loss. Yield-scaled N2O-N emissions in NT-2019 (3696.4 g N2O-N Mg-1) were twofold higher than RT-2019 (1872.7 g N2O-N Mg-1) and almost fourfold higher than NT-2021 and RT-2021 indicating in a wet year like 2019, yield-scaled N2O-N emissions were higher in NT than RT. Principal component analysis indicated N2O-N fluxes were less driven by soil N and more by environmental conditions and N balances reflecting on N application at planting in this trial. . The objectives for chapter 2 were to evaluate the legacy effect of tillage (RT vs. NT) and cover crops (WCR vs. a no cover crop control) on soil nitrate-N (NO3-N), volumetric water content (VWC), temperature, and N2O emission trends during a fallow period after corn in a six-yr trial. In spring 2020 we also estimated WCR biomass and N uptake as affected by tillage practices and compared WCR biomass to weeds in the no cover crop treatment. In rye growing season, winter cereal rye biomass was 55% higher than weeds in the fallow treatment. A linear positive relation between WCR biomass and N uptake (R2= 0.93) and C accumulation (R2 = 0.99) indicates WCR captures more N and adds more C inputs than weeds. Winter cereal rye biomass was also higher in RT than NT reflecting on higher soil temperature and N availability in RT than NT. Soil VWC was lower in WCR plots and there was a negative linear relation between days of the year (DOY) and VWC (R2 = 0.6). Despite all these differences, soil N2O-N values were mainly less than 5 g N2O-N ha-1d-1 in all sampling dates regardless of tillage or cover crop treatment. We conclude that in poorly drained Alfisols with claypan and fragipans, NT is not an effective strategy to decrease N2O-N fluxes. Hairy vetch benefits corn grain yield and supplement N but that increases N loss through N2O-N emissions. We concluded that we should focus on decreasing N2O emissions early in corn season since majority of N is lost during that time sometimes 300 times higher than those reported during the WCR phase. Some changes in management practices that could reduce N2O losses are shifting from upfront N application to sidedress N management, terminating hairy vetch at or even after corn planting, and combine these efforts with enhanced efficiency fertilizers that control nitrification and denitrification.

This study analyzes the distribution system of fresh fruits and vegetables used by Brazilian population in Massachusetts, which is estimated to be over 250,000. Maxixe (Cucumis anguria) and abóbora híbrida (Cucurbita spp.), vegetable crops popular among Brazilians were used as test crops to better understand the distribution system and to assess the most efficient way for local farmers to enter into the marketplace with their fresh produce. In person interviews with Brazilian consumers, and test marketing were used in this research to evaluate sales potential and pricing levels for abóbora híbrida produced in Massachusetts. The squash was sold at four locations during two weeks at specific pricing levels and results showed good sales potential for this crop. Yields and production practices were evaluated at the UMass Research Farm to test productivity and adaptability of this squash in local climate conditions. Results of this pilot study also underscored the importance of local farmers understanding the role of cultural characteristics of the Brazilian community in the United States, especially with regard to language and media, in order to fully capitalize on this market.

Integrated crop-livestock systems (ICLS) incorporate cropping systems and livestock production by grazing cover crops. With a growing awareness in recent years regarding agricultural sustainability, these systems have begun to be re-introduced into the southeastern U.S. This study evaluated cover cropping systems under grazed no-till (GNT), un-grazed no-till (UNT), and un-grazed conventional tillage (UCT) management, in Mississippi. Beef cattle (Bos spp.) performance was significantly less in the cover crop treatment of oats (Avena sativa) + crimson clover (Trifolium incarnatum) + radish (Raphanus sativus; OCR) in both average daily gain (ADG; 3.03 lb hd-1 d-1) and total gain ac-1 (GAIN; 346 lb ac-1). Soybean (Glycine max) yield was unaffected by cover crop treatment and tillage. The lowest expected economic return was generated by OCR ($749.31 ac-1). Soil penetration resistance was unaffected by the influence of grazing. The greatest concentrations of soil organic carbon (1.44%) and soil nitrogen (0.20%) were observed in GNT.

Crop production systems which utilize the biomass produced by rye (<i>Secale cereale</i> ) to suppress weed growth and conserve soil moisture have been developed at Virginia Tech. The success of alternative, reduced-input crop production systems has encouraged research into the potential for breaking the traffic-tillage cycle associated with conventional tillage crop production systems. The fragile residues encountered in agricultural crop production, whether incorporated into the soil or distributed on the soil surface, provide minimal protection against compaction by wheeled vehicles. The potential of an intact cover crop to reduce machine-induced effects on soil properties that affect primary crop growth was the subject of this study. A randomized complete block experiment was conducted at the Whitethorne Farm in Montgomery County, Virginia. One set of plots was arranged on a terrace adjacent to the New River in a fine, mixed, mesic, Aquic Argiudolls. Another set of plots was arranged on an upland site, a river terrace tread, in a fine-loamy, mixed, mesic, Typic Hapludults. Three rye cover crop treatments were examined. In one, a live cover crop was completely undisturbed prior to tracking by a wheel-type tractor. In another, the cover crop was chemically desiccated, and in the third treatment, all above-ground biomass was removed from plots prior to machine traffic. The treatments permitted investigation of the effects of crop condition on machine-induced soil compaction and the contribution of root reinforcement to the alteration of soil response to machine traffic. A fall-tilled fallow treatment served as an experimental control. Three levels of traffic were investigated: one pass, three passes, and five passes. Undisturbed soil core samples were analyzed to determine machine-induced effects on dry bulk density, pore size distribution, and saturated hydraulic conductivity. The treatments affected soil response to machine traffic. The cover crop treatments altered the soil-plant microenvironment, affecting soil parameters that influence compactibility. Soil compaction was attenuated by the reinforcing effect of a network of undisturbed roots within the soil. There was no convincing evidence that above-ground biomass contributed directly to the reduction of machine-induced compaction effects. Soil response to machine traffic was limited to the uppermost 15 cm of the soil profile. / Ph. D.

This study compares the energy costs of synthesizing, distributing, and applying manufactured nitrogen fertilizer to the overall energy costs associated with nitrogen-fixing legume production and use. The energetics of com silage and com grain production under standard and alternative practices are examined. Economic analyses of crop production practices are used to aid the selection of recommended alternative practices. In corn silage production, cover-cropped treatments had a significant advantage over standard practice treatments in terms of overall energy expenditures for field operations. Cover-cropped no-till treatments required an average energy expenditure of 9026 MJ/ha compared to 19,763 MJ/ha required by the standard-practice no-till treatment. Cover-cropped treatments that used disking to kill the cover crops required an average energy expenditure of 9781 MJ/ha compared to 18,488 MJ /ha required by the standard-practice winter-fallow treatment. Alternative-practice treatments that utilized vetches to provide nitrogen for com production performed significantly better than standard-practice treatments in terms of energy use per unit of crop output. In addition, the alternative hairy vetch - no-till treatment produced a $33/ha greater average net revenue than the standard-practice no-till treatment. Weed control energy requirements for cover-cropped ridge-tillage com grain production were compared. Broadcast application of pre-emergence herbicides required an energy expenditure of 1160 MJ fha. Cultivation of ridges to control weeds consumed 380 MJ/ha. Economic costs of ridge cultivation were $14/ha. Broadcast application of pre-emergence herbicides cost $49/ha. / Master of Science

Winter fallow corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production systems are susceptible to erosion and agrochemical transport. This research determined the effects of Cover Crop Minimum Tillage (CCMT) on erosion and agrochemical transport from corn-soybean rotations at field scale, while assessing impacts to agroeconomics and irrigation in Mississippi’s Delta Region. CCMT did not affect total suspended solids (p = 0.53), total inorganic phosphorus (TIP) (p = 0.30), or total nitrogen (TN) (p = 0.25) loads, but did reduce TIP (p = 0.018), TN (p = 0.011), and nitrate-nitrite (p = 0.007) concentrations. An economic loss of $281/ha with no effect on yield (p = 0.09), irrigation use efficiency (p = 0.38), or consumptive water use (p = 0.83) was observed. CCMT will not improve profitability of corn-soybean rotations in the Delta and transitioning from fallowing to CCMT will have varying effects on erosion and agrochemical transport.

With herbicide efficacy declining as weeds continue to evolve and resist key modes of action, long-term, multi-faceted control practices need to be investigated. Two studies, involving cover crops and tillage, were implemented to understand how management practices influence the weed seed bank. The objectives of both studies were to examine long-term changes in the weed seed bank in response to tillage methods, fertility, and cover crops, and to analyze differences in distribution and community composition between individual species in the weed seed bank. To assess the weed community present in both seed banks, soil samples were collected, and a soil grow out was conducted in the greenhouse. To examine the field-emerged seed banks, percent coverage was collected for each weed species, crop residue, bare ground, and cover crop if present. The first study was established in 1970, evaluating four tillage systems: moldboard plow (CT), chisel plow (RT), alternative (AT), and no-tillage (NT). From 1970 to 1990, this study was continuous corn (Zea mays L.), but in 1991, soybeans (Glycine max L.) were added into the rotation, marking the beginning of the current corn-soybean rotation. Fertilizer treatments (no-fertilizer, nitrogen only, and NPK) were also evaluated. Each tillage and fertility treatment were replicated four times in the field in 6 m by 8 m plots. Weed seeds were found to be distributed within the soil profile differently by tillage treatment. No-till treatments maintained most of the seed bank near the surface of the soil. Based on the response of individual species to fertility treatments, community shifts in seed bank composition were found. LAMAM, STEME, and SIBVI had the greatest richness in NPK treatments compared to no fertilizer and nitrogen only. CERVU tended to favor treatments without any fertilizer. Tillage and fertility were also found to interact and influence species presence and community composition. The second study was established in 2013, to examine changes and differences in distribution and composition between individual species in the weed community in response to cover crop rotations and tillage. A split-plot design with three crop rotation systems was implemented: 1) corn (Zea mays L.) – cereal rye (Secale cereale L.) – soybean (Glycine max (L.) Merr.) – hairy vetch (Vicia villosa Roth) [CcrShv], 2) corn-cereal rye-soybean-oats + radish (Avena sativa L. + Raphanus sativus L.) [CcrSor], and 3) corn-no cover crop-soybean-no cover crop [NOCC], and two tillage treatments: conventional tillage and no-till. This field study also supported previous findings of higher weed diversity in no-till systems. ANOVA performed in R suggested species richness was significantly higher in no-tillage treatments in comparison to tillage treatments. For the field-emerged weed community, a pairwise comparisons test suggested cover crop treatments have significantly lower weed richness compared to plots with no cover crop present, but there was no interactive effect of tillage. 3-Way ANOVAs suggested time, tillage, and crop rotation influenced each weed species differently. Due to individual weed species having different requirements for germination and seed longevity, these data suggest the importance of developing and implementing a quality, integrated weed management program to maintain low levels of weed emergence and seed credits to the seed bank.