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Recent advancements in agricultural metagenomics allow for characterizing microbial indicators of soil health brought on by changes in management decisions, which ultimately affect the soil environment. Field-scale studies investigating the microbial taxa from agricultural experiments are sparse, with none investigating the long-term effect of crop rotation and tillage on microbial indicator species. Therefore, our goal was to determine the effect of rotations (continuous corn, CCC; continuous soybean, SSS; and each phase of a corn-soybean rotation, Cs and Sc) and tillage (no-till, NT; and chisel tillage, T) on the soil microbial community composition following 20 years of management. We found that crop rotation and tillage influence the soil environment by altering key soil properties, such as pH and soil organic matter (SOM). Monoculture corn lowered pH compared to SSS (5.9 vs. 6.9, respectively) but increased SOM (5.4% vs. 4.6%, respectively). Bacterial indicator microbes were categorized into two groups: SOM dependent and acidophile vs. N adverse and neutrophile. Fungi preferred the CCC rotation, characterized by low pH. Archaeal indicators were mainly ammonia oxidizers with species occupying niches at contrasting pHs. Numerous indicator microbes are involved with N cycling due to the fertilizer-rich environment, prone to aquatic or gaseous losses.

The environmental consequences of residue removal practices to support cellulosic biofuel production remain poorly understood. In the U.S. Midwest, corn (Zea mays L.) stover removal combined with no-till practices may increase or decrease soil N2O emissions by influencing soil moisture, temperature, and nutrient dynamics, yet empirical evidence from long-term field experiments is inconsistent. We investigated the effects of residue management (residue retained or removed) and tillage (chisel-till or no-till) on cumulative soil nitrous oxide (N2O) emissions, grain yield, and yield-scaled N2O emissions in a 3-year study initiated 10 years after treatment implementation in a long-term, continuous corn experiment in Illinois, United States. Crop yields were affected by treatment in only one of three study years, with the combination of residue removal and no-till reducing yields compared to both chisel-till treatments. Cumulative N2O emissions, soil inorganic N concentrations, and yield-scaled N2O emissions differed over the 3-year period and were significantly affected by tillage, with no response to residue management. In 2 years, no-till decreased cumulative N2O emissions and yield-scaled N2O emissions by an average of 64% and 60%, respectively. Correlations between daily N2O fluxes and soil moisture, temperature, and inorganic N concentrations suggested that the relative importance of these variables changed depending on year and treatment. While more research across a range of sites and management practices is needed, our findings support previous studies which have challenged IPCC methodology assumptions regarding the effects of residue removal on N2O emissions. We conclude there is inherent difficulty in predicting the impacts of residue removal due to the complexity of soil processes underlying N2O emissions coupled with inter-annual weather variability in this rainfed continuous corn system. Future efforts to evaluate the net greenhouse gas emissions of cellulosic biofuel production may benefit from accounting for this uncertainty.

The environmental consequences of residue removal practices to support cellulosic biofuel production remain poorly understood. In the U.S. Midwest, corn (Zea mays L.) stover removal combined with no‐till practices may increase or decrease soil N2O emissions by influencing soil moisture, temperature, and nutrient dynamics, yet empirical evidence from long‐term field experiments is inconsistent. We investigated the effects of residue management (residue retained or removed) and tillage (chisel‐till or no‐till) on cumulative soil nitrous oxide (N2O) emissions, grain yield, and yield‐scaled N2O emissions in a 3‐year study initiated 10 years after treatment implementation in a long‐term, continuous corn experiment in Illinois, United States. Crop yields were affected by treatment in only one of three study years, with the combination of residue removal and no‐till reducing yields compared to both chisel‐till treatments. Cumulative N2O emissions, soil inorganic N concentrations, and yield‐scaled N2O emissions differed over the 3‐year period and were significantly affected by tillage, with no response to residue management. In 2 years, no‐till decreased cumulative N2O emissions and yield‐scaled N2O emissions by an average of 64% and 60%, respectively. Correlations between daily N2O fluxes and soil moisture, temperature, and inorganic N concentrations suggested that the relative importance of these variables changed depending on year and treatment. While more research across a range of sites and management practices is needed, our findings support previous studies which have challenged IPCC methodology assumptions regarding the effects of residue removal on N2O emissions. We conclude there is inherent difficulty in predicting the impacts of residue removal due to the complexity of soil processes underlying N2O emissions coupled with inter‐annual weather variability in this rainfed continuous corn system. Future efforts to evaluate the net greenhouse gas emissions of cellulosic biofuel production may benefit from accounting for this uncertainty. When evaluating net GHG emissions of removing corn stover to support cellulosic biofuel, life cycle assessment and IPCC approaches commonly predict soil nitrous oxide emissions will decrease. Our results support a growing evidence‐base showing nitrous oxide emissions do not necessarily decrease, implying the benefits of biofuels may be overestimated. [ABSTRACT FROM AUTHOR]

Crop rotation and tillage alter soil organic matter (SOM) dynamics by influencing the soil environment and microbes carrying out C and N cycling. Our goal was to evaluate the effect of long-term crop rotation and tillage on the quantity of C and N stored in SOM and microbial biomass. Two experimental sites were used to evaluate four rotations--continuous corn (Zea mays L.) (CCC), corn-soybean (Glycine max [L.] Merr.) (CS), corn-soybean-wheat (Triticum aestivum L.) (CSW), and continuous soybean (SSS), each split into chisel tillage (CT) and no-till (NT) subplots. The CSW rotation increased soil organic carbon (SOC) content compared to SSS; SSS also reduced total nitrogen (TN) compared to other rotations. Levels of SOC and TN were 7% and 9% greater under NT than CT, respectively. Rotation did not affect microbial biomass C and N (MBC, MBN) while tillage reduced only MBN at 10-20 cm compared to NT, likely related to dispersion of N fertilizers throughout the soil. Despite the apparent lack of sensitivity of microbial biomass, changes in SOC and TN illustrate the effects of rotation and tillage on SOM dynamics. The inclusion of crops with high C: N residues and no-till use both support higher C and N content in the top 20 cm of the soil. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] can produce compensatory yield following plant stand reduction, but the effect of plant size within a developmental stage on this ability is unknown. We seeded two cultivars at 15, 30, 45, and 60 plants m-2, and identified large and small plants within each density at V3 (third trifoliate), V6 (sixth trifoliate), R2 (full bloom), and R4 (full pod) developmental stages. Subplots were either thinned to a density of 5.3 plants m-2 or left at intact densities. The ability for large or small plants to produce compensatory growth and yield was evaluated by the differences between subsequent growth and yield produced in thinned vs. intact stands. We found small plants had equivalent harvest index to large plants across all plant densities and developmental stages, suggesting small plants were as efficient as large plants for compensating seed yield relative to biomass when stands were not thinned. However, when stands were thinned, compensatory growth and yield were different between large and small plants. For example, across all plant densities thinned at V3, large and small plants produced 51 and 37 g plant-1, respectively, and compensatory yield contributed 30 and 24 g plant-1, respectively. Thus, small plants produced 80% as much compensatory yield as large plants when thinned at V3. However, by the same comparison, the contribution of small plants declined to 57% when thinning was delayed to R4 development, suggesting small plants lost more compensatory ability over time. We conclude initial soybean plant size impacts compensatory yield plant-1. [ABSTRACT FROM AUTHOR]

Cover crops (CC) are being actively promoted in Illinois as a tool to improve soil properties and enhance crop performance and yield. Our goals were to assess the short-term ability of radish (Raphanus sativus L. var. longipinnatus) and companion CC to improve (i) soil properties and (ii) soybean (Glycine max L. Merr.) growth and yield following compaction and CC treatments under conventional systems. We used a 6 X 3 factorial arrangement of the CC and compaction treatments in a completely randomized design with two replications in two independent year-locations hereby referred as environments. Cover crop treatments included radish alone "R", and with rye (Secale cereale L.) "RR", triticale (x Triticosecale 'Presto') "RTR", buckwheat (Fagopyrum esculentum L. Moench) "RB", or hairy vetch (Vicia villosa Roth) "RH V", and a control with no cover crop "NCOV". Compaction treatments were no compaction (Nc), and two levels of compaction achieved with a large tractor (LT) or a hauling truck (TK). Compaction was temporarily achieved and disappeared after the CC growing season. Cover crop treatments significantly lowered soil NO3-N compared to NCOV yet no further effect was evident on soils. Soybean yield for CC treatments were not different from control plots. Results from this study showed that one growing season was not enough time to evidence changes in soil properties related to cover cropping yet they were useful tools for retaining NO3-N in the system. In addition, following adequate management practices, CC should not affect soybean growth and yield. [ABSTRACT FROM AUTHOR]

Organic inputs have been suggested to have either suppressive or conducive effects on levels of plant diseases. In this study, we compared effects of organic matter amendments and transitional cropping systems on plant diseases during the transition from conventional to organic agricultural production and 2 yr following. During the 3-yr transition, organic amendments included raw dairy manure, composted dairy manure, and non-amended treatment superimposed on three cropping systems (perennial pasture, cash grain crops, and vegetable crops). Two years of post-transition crops included tomato (Lycopersicon esculentum Mill.) and bell pepper (Capsicum annuum L. var. annuum) in the first year and soybean [Glycine max (L.) Merr.] in the second. During transition, raw manure amendments resulted in higher levels of diseases caused by some biotrophic pathogens, including rusts in corn (Zea mays L.) and orchardgrass (Dactylisglomerata L.). However, raw manure applications were also found to suppress some diseases caused by necrotrophic pathogens, including anthracnose and Septoria leaf spot in tomato. Manure applications promoted higher soybean yields. Powdery mildew of cucurbits (Curbubita moschata Duchesne) was suppressed by composted manure. After transition, tomato plants grown in plots previously under the vegetable system had the highest levels of anthracnose, and soybean grown in plots previously in the pasture system had the highest levels of bacterial pustule, despite the fact that these same plots produced the highest yields in soybean. Yield benefits resulting from applications of raw manure to a pasture transition system may be attractive for farmers, but disease management strategies will need to be considered to prevent increased disease levels. [ABSTRACT FROM AUTHOR]

Illinois ranks second in soybean [Glycine max (L.) Merr.] production in the United States with an annual crop value of some $4 billion. To discover what management practices, soil parameters, and environmental conditions enable higher soybean yields, the Illinois Soybean Association (ISA) started in 2010 a state-wide "Yield Challenge" (YC) program. Enrolled producers established a "challenge" plot and adjoining "standard" practices plot, and agreed to share crop management information, soil samples, and yield data. Our work describes data analyses and findings using data generated under this program. Yields differed between standard and challenge plots across the state, with foliar applications of fungicide and or insecticide resulting in significant yield increases. Using principal component analyses and multiple regression tools, we were able to explain about 54% of the variation in soybean yield for the state in 2010. Within the available data range, delays in planting date and increased row spacing both reduced soybean yields, and tilled fields yielded more than no- tilled soybean fields. We uncovered a negative trend between soybean yield and PCI, formed by soil cation exchange capacity (CEC), dominant cations, and soil organic matter (SOM), likely due to the drainage characteristics of the plots. Yields were also decreased with increasing values of PC3, a variable that includes soil pH, Mn levels, and soybean cyst nematode (SCN) egg count. On the other hand, higher soil test values of P, Zn, Fe, and K, included in PC2, were related to higher soybean yields. We see this as a promising start to identifying management factors that may be addressed as we continue the search for higher soybean yields. [ABSTRACT FROM AUTHOR]