Kurt D. Thelen

To determine if current university fertilizer rate and timing recommendations pose a limitation to high-yield corn (Zea mays subsp. mays) and soybean (Glycine max) production, this study compared annual Phosphorous (P) and Potassium (K) fertilizer applications to biennial fertilizer applications, applied at 1× and 2× recommended rates in corn–soybean rotations located in Minnesota (MN), Iowa (IA), Michigan (MI), Arkansas (AR), and Louisiana (LA). At locations with either soil test P or K in the sub-optimal range, corn grain yield was significantly increased with fertilizer application at five of sixteen site years, while soybean seed yield was significantly increased with fertilizer application at one of sixteen site years. At locations with both soil test P and K at optimal or greater levels, corn grain yield was significantly increased at three of thirteen site years and soybean seed yield significantly increased at one of fourteen site years when fertilizer was applied. Site soil test values were generally inversely related to the likelihood of a yield response from fertilizer application, which is consistent with yield response frequencies outlined in state fertilizer recommendations. Soybean yields were similar regardless if fertilizer was applied in the year of crop production or before the preceding corn crop. Based on the results of this work across the US and various yield potentials, it was confirmed that the practice of applying P and K fertilizers at recommended rates biennially prior to first year corn production in a corn–soybean rotation does not appear to be a yield limiting factor in modern, high management production systems.

BACKGROUND: Isoflavones, such as genistein and daidzein, are produced in soybean seed [Glycine max (L.) Merr.] and may be associated with health benefits in the human diet. More research is required to determine the effect of agronomic soybean treatments on isoflavone concentration. In this study from 2012 to 2014 at Michigan State University and Breckenridge locations, we have evaluated agronomic input management systems which are marketed to increase or protect potential soybean grain yield, including: nitrogen fertilization, herbicide–defoliant, foliar applied fertilizer, a biological‐based foliar application, foliar applied fungicide, foliar applied insecticide, a seed applied fungicide, and a maximized seed treatment that included fungicide and insecticide as well as an inoculant and lipo‐chitooligosaccharide nodulation promoter, for their effect on soybean seed genistein and daidzein concentrations.RESULTS: Paired comparisons were made between treatments receiving a designated management input and those without the input. Year and location had a significant effect on isoflavone concentrations. Agronomic management inputs impacted soybean seed daidzein concentrations in 15 of 48 field observations and genistein concentrations in 11 of 48 observations.CONCLUSION: The research supports findings that soybean seed isoflavone levels exhibit a location specific response, and the temporal variability experienced between years appears to influence changes in soybean isoflavone levels more than location. © 2016 Society of Chemical Industry

Integrating cover crops into the corn (Zea mays L.) forage-production system could enhance growers’ profitability and improve ecosystem services. Field plots were established at two locations in Michigan during 2012--2014 to evaluate ethanol production, estimate carbon and energy balance, and the economics of corn forage plus cover crop, cropping systems. In the 2012--2013 crop cycle, which was characterized by a summer drought, the cereal rye (Secale cereale L.), and triticale (Triticale hexaploide Lart.), winter annual cover crops increased cropping system biomass yield by 44%, and total ethanol yield by 28% relative to the no-cover control. During the 2012--2013 cycle, cover crops provided sufficient biomass (6.5 and 8.1 Mg ha⁻¹, respectively, for cereal rye and triticale) to result in a profitable harvest as a biofuel feedstock. However, following a harsh winter, such as that experienced in the 2013--2014 cycle, cover crop yield (1.6 and 1.2 Mg ha⁻¹, respectively, for cereal rye and triticale) was compromised to the point that harvest was not economically justified. Incorporating cover crops into a corn forage cropping system increased total biomass and potential biofuel yield and generated a very favorable net ecosystem carbon and energy balance.

Public concern over herbicide contamination of water, surfactant effects on amphibians, and herbicide-resistant weeds has led to increased interest in alternative weed-control systems. In addition, direct-cut harvest-associated yield losses of dry bean (Phaseolus vulgaris L.) are of concern to some growers. Often there is difficulty operating combine mechanisms near soil surfaces to reach the lowermost bean pods. The objectives of this study were to evaluate the utility of an interseeded spring-planted rye (Secale cereale L.) cover for: (a) weed suppression and (b) elongation of dry bean stems to raise lower pod heights and facilitate direct-cut harvest. We hypothesized that a rye cover would suppress weeds and shade dry bean plants, resulting in a stem elongation response. Overall, interseeded rye cover reduced dry bean yields, above-ground biomass, and plant heights. Rye cover also suppressed above-ground weed biomass in several instances. However, despite overall reductions in dry bean-plant vigor, treatments including rye cover resulted in significantly greater heights of lowermost dry bean-pod attachment, indicating the presence of a stem elongation effect.

Background: Corn grain is an important renewable source for bioethanol production in the USA. Corn ethanol is currently produced by steam liquefaction of starch-rich grains followed by enzymatic saccharification and fermentation. Corn stover (the non-grain parts of the plant) is a potential feedstock to produce cellulosic ethanol in second-generation biorefineries. At present, corn grain is harvested by removing the grain from the living plant while leaving the stover behind on the field. Alternatively, whole corn plants can be harvested to cohydrolyze both starch and cellulose after a suitable thermochemical pretreatment to produce fermentable monomeric sugars. In this study, we used physiologically immature corn silage (CS) and matured whole corn plants (WCP) as feedstocks to produce ethanol using ammonia fiber expansion (AFEX) pretreatment followed by enzymatic hydrolysis (at low enzyme loadings) and cofermentation (for both glucose and xylose) using a cellulase-amylase-based cocktail and a recombinant Saccharomyces cerevisiae 424A (LNH-ST) strain, respectively. The effect on hydrolysis yields of AFEX pretreatment conditions and a starch/cellulose-degrading enzyme addition sequence for both substrates was also studied. Results: AFEX-pretreated starch-rich substrates (for example, corn grain, soluble starch) had a 1.5-3-fold higher enzymatic hydrolysis yield compared with the untreated substrates. Sequential addition of cellulases after hydrolysis of starch within WCP resulted in 15-20% higher hydrolysis yield compared with simultaneous addition of hydrolytic enzymes. AFEX-pretreated CS gave 70% glucan conversion after 72 h of hydrolysis for 6% glucan loading (at 8 mg total enzyme loading per gram glucan). Microbial inoculation of CS before ensilation yielded a 10-15% lower glucose hydrolysis yield for the pretreated substrate, due to loss in starch content. Ethanol fermentation of AFEX-treated (at 6% w/w glucan loading) CS hydrolyzate (resulting in 28 g/L ethanol at 93% metabolic yield) and WCP (resulting in 30 g/L ethanol at 89% metabolic yield) is reported in this work. Conclusions: The current results indicate the feasibility of co-utilization of whole plants (that is, starchy grains plus cellulosic residues) using an ammonia-based (AFEX) pretreatment to increase bioethanol yield and reduce overall production cost.

Wheat (Triticum aestivum L.) crop residue can negatively affect the growth and development of no-till corn (Zea mays L.). The objective of this study was to determine whether nitrogen management practices including legume cover crops and manure applications used in conjunction with a pre-sidedress soil nitrate test (PSNT) could be used to overcome the observed wheat residue antagonism of no-till corn growth and development. A PSNT nitrogen strategy was effective in maintaining no-till corn grain yield in wheat residue systems equivalent to no-till corn grain yield in no-wheat residue systems in 4 of 6 site years. Similar results were obtained for PSNT plus clover cover crop and PSNT plus manure plus clover cover crop nitrogen management systems. Utilization of a PSNT with manure application equalized no-till corn grain yield in high wheat residue treatments with no-till corn grain yield in treatments without wheat residue in all site years. This can be a recommended practice in the Michigan eco-region.

The emerging cellulosic‐based ethanol industry will likely use corn (Zea mays L.) stover as a feedstock source. Growers wishing to maintain, or increase soil C levels for agronomic and environmental benefit will need to use C amendments such as manure, compost, or cover crops, to replace C removed with the corn stover. The objective of this research was to determine the effect of cover crops, manure, and compost on short‐term C sequestration rates and net global warming potential (GWP) in a corn–soybean [Glycine max (L.) Merr.] rotation with complete corn stover removal. Field experiments consisting of a corn–soybean–corn rotation with whole‐plant corn harvest, were conducted near East Lansing, MI over a 3‐yr period beginning in the fall of 2001. Carbon amendments were: compost, manure, and a winter cereal rye (Secale cereale L.) cover crop. Compost and manure amendments raised soil C levels in the 0 to 5 and 0 to 25 cm soil profile but not in the 5 to 25 cm soil profile over the relatively short‐term duration of the study. Total soil organic C (SOC) (kg ha⁻¹) in the 0 to 25 cm profile increased by 41 and 25% for the compost and manure treatments, respectively, and decreased by 3% for the untreated check. Compost and manure soil amendments resulted in a net GWP of −1811 and −1060 g CO₂ m⁻² yr⁻¹, respectively, compared to 12 g CO₂ m⁻² yr⁻¹ for untreated.