In addition to soil health and conservation benefits, cover crops (CCs) may offer weed control in the midwestern United States, but individual studies report varying effects. We conducted a ...meta‐analysis of studies measuring weed biomass (WBIO) or density (WDEN) in paired CC and no‐cover treatments in corn (Zea mays L.)–soybean Glycine max (L.) Merr rotations in the U.S. Midwest. Fifteen studies provided 123 paired comparisons of WBIO and 119 of WDEN. Only grass CCs significantly reduced WBIO, while no CC reduced WDEN. We found no evidence CC management factors (e.g., termination method) directly affected outcomes. Our dataset showed that a 75% reduction in WBIO requires at least 5 Mg ha−1 of CC. Simulations from a process‐based model (SALUS) indicated achieving 5 Mg ha−1 requires substantially earlier fall planting and later spring termination in most years, conflicting with typical cash‐crop planting and harvesting. We conclude CCs significantly reduce WBIO, but current CC management constraints render these reductions variable and uncertain.
Abstract
Regional and global impact assessment tools are increasingly used to explore and evaluate the impact of climate change and extreme events on crop yield and environmental externalities. ...However, the large uncertainties associated with the inputs or the parameters in crop models within these tools, limits their predictive ability, exceeding the spatiotemporal variability of observed yields. The objective of this study is to explore and quantify different sources of uncertainties and assumptions made behind initial conditions (IC), soil input, meteorological forcing, management practices and model cultivar parameters by running regional simulations for the time period between 2009 and 2019. Simulations were performed for maize and soybean using the pSIMS platform across the U.S Midwest by incrementally accounting for five sources of uncertainty with a
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resolution using the APSIM and DSSAT crop growth models. First, the relative contribution of different sources of uncertainty was estimated over time and space. Then, a series of nitrate leaching hotpots were identified and a regional maize yield productivity index was estimated by decomposing the uncertainty in the same scenario using a hierarchical Bayesian random-effect model. All factors showed a strong spatial pattern in their contribution to the total uncertainty and their contribution was found to be partially dependent on location. However, across the whole region, it was found that the uncertainty around management is larger than IC, soil and meteorological forcing while showing a strong correlation with each of these factors. Given the high spatial correlation, we hypothesize that constraining soil inputs and management uncertainty could allow for the largest reduction in predictive uncertainty for crop yield. Our results showed vast areas over northern IA, IL and IN with high potential for NO
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leaching and southern IA, IL and east NE with lower maize productivity index compared to the regional average.
Energy crops for biofuel production, especially switchgrass (Panicum virgatum), are of interest from a climate change perspective. Here, we use outputs from a crop growth model and life cycle ...assessment (LCA) to examine the global warming intensity (GWI; g CO2 MJ−1) and greenhouse gas (GHG) mitigation potential (Mg CO2 year−1) of biofuel systems based on a spatially explicit analysis of switchgrass grown on marginal land (abandoned former cropland) in Michigan, USA. We find that marginal lands in Michigan can annually produce over 0.57 hm3 of liquid biofuel derived from nitrogen‐fertilized switchgrass, mitigating 1.2–1.5 Tg of CO2 year−1. About 96% of these biofuels can meet the Renewable Fuel Standard (60% reduction in lifecycle GHG emissions compared with conventional gasoline; GWI ≤37.2 g CO2 MJ−1). Furthermore, 73%–75% of these biofuels are carbon‐negative (GWI less than zero) due to enhanced soil organic carbon (SOC) sequestration. However, simulations indicate that SOC levels would fail to increase and even decrease on the 11% of lands where SOC stocks >>200 Mg C ha−1, leading to carbon intensities greater than gasoline. Results highlight the strong climate mitigation potential of switchgrass grown on marginal lands as well as the needs to avoid carbon rich soils such as histosols and wetlands and to ensure that productivity will be sufficient to provide net mitigation.
Biofuels derived from energy crops grown on marginal lands are attractive in terms of climate change because of their low input requirements, potential for soil organic carbon sequestration, and ability to reduce food‐fuel conflicts. We examined the global warming impact of biofuel systems using a crop growth model and life cycle assessment based on a spatially explicit analysis of switchgrass grown on marginal land (abandoned former cropland) in Michigan, USA. The findings highlight the significant climate mitigation potential of biofuels derived from switchgrass grown on marginal lands, as well as the importance of avoiding carbon‐rich soils when growing switchgrass.
•Root attributes such as mass, length, and N concentration are highly variable across environments.•Maize and soybean root to shoot (R:S) ratios averaged 0.09 ± 0.02 and 0.17 ± 0.05, ...respectively.•Maximum shoot biomass explained 70 % of variation in root biomass.•Variation in R:S was explained by weather (r2 < 0.41), shoot traits (r2 < 0.50) and root traits (r2 < 0.73).
Root traits are important to crop functioning, yet there is little information about how root traits vary with shoot traits. Using a standardized protocol, we collected 160 soil cores (0−210 cm) across 10 locations, three years and multiple cropping systems (crops x management practices) in Iowa, USA. Maximum root biomass ranged from 1.2 to 2.8 Mg ha−1 in maize and 0.86 to 1.93 Mg ha−1 in soybean. The root:shoot (R:S) ratio ranged from 0.04 to 0.13 in maize and 0.09 to 0.26 in soybean. Maize produced 27 % more root biomass, 20 % longer roots, with 35 % higher carbon to nitrogen (C:N) ratio than soybean. In contrast, soybean had a 47 % greater R:S ratio than maize. The maize R:S ratio values were substantially lower than literature values, possibly due to differences in measurement methodologies, genotypes, and environment. In particular, we sampled at plant maturity rather than crop harvest to minimize the effect of senescence on measurements of shoots and roots. Maximum shoot biomass explained 70 % of the variation in root biomass, and the R:S ratio was positively correlated with the root C:N measured in both crops. Easily-measured environmental variables including temperature and precipitation were weakly associated with root traits. These results begin to fill an important knowledge gap that will enable better estimates of belowground net primary productivity and soil organic matter dynamics. Ultimately, the ability to explain variation in root mass production can be used to improve C and N budgets and modeling studies from crop to regional scales.
•Biological N fixation (BNF) was maximized early in the seed filling period, achieving a maximum rate of 3 kg N ha–1 day–1.•Biomass production was a better predictor of BNF than seed protein or ...environmental factors.•The BNF rate during seed-fill was driven by crop growth rate (C supply) rather than seed N accumulation rate (N demand).•The N exported in seed exceeded the N derived from BNF, indicating a negative partial N balance for soybean production.
The rainfed USA Midwestern region has deep, fertile soils and leads the USA in soybean Glycine max, (L.) Merr. production. Biological nitrogen (N) fixation (BNF) contributes a portion of the soybean N requirement, but variability in BNF is poorly understood and estimates of BNF for this region are rare. We established experiments in Iowa, USA to gain a better understanding of BNF and increase its predictability. We collected in-season BNF measurements accompanied by high temporal resolution soil and plant growth measurements. Across two years, two locations and two planting dates, we found that BNF contributed 23–65% of total aboveground N accumulation in soybean. The BNF rate was maximized at the early seed-filling period and varied from 1 to 3 kg N ha−1day−1. During seed filling period, the rate of BNF was related to crop growth rate (carbon (C) supply) but not to N accumulation by the reproductive organs (N demand). We found that a minimum crop growth rate of 135 kg dry matter ha−1day-1 is required to sustain maximum BNF rates. In contrast to BNF, the soil inorganic N uptake rate was related to seed N demand but not to C supply. Biomass production was the best predictor of total soybean BNF (R2 > 0.83). On average, 0.013 kg N was fixed per kg biomass produced. Across all trials, the N exported via seed was greater than the N imported via BNF, which suggests that Midwest US soybeans may reduce soil organic matter. We concluded that future research efforts should focus on increasing C – rather than N – availability during the seed filling period towards improving both grain yields and environmental sustainability.
•Maize and soybean roots occupy the space between 76cm rows at 480°Cd after sowing.•Root front velocity change rate from slow to fast at 5th maize leaf and 3rd soybean node.•Root front velocity ...ranged from 0.9cmd−1 (slow phase) to 3.2cmd−1 (fast phase).•Corn and soybean maximum root depth varied from 89 to 157cm.•Groundwater table depth explained 61% of the variation in maximum root depth.
Quantitative measurements of root traits can improve our understanding of how crops respond to soil and weather conditions, but such data are rare. Our objective was to quantify maximum root depth and root front velocity (RFV) for maize (Zea mays) and soybean (Glycine max) crops across a range of growing conditions in the Midwest USA. Two sets of root measurements were taken every 10–15days: in the crop row (in-row) and between two crop rows (center-row) across six Iowa sites having different management practices such as planting dates and drainage systems, totaling 20 replicated experimental treatments. Temporal root data were best described by linear segmental functions. Maize RFV was 0.62±0.2cmd−1 until the 5th leaf stage when it increased to 3.12±0.03cmd−1 until maximum depth occurred at the 18th leaf stage (860°Cd after planting). Similar to maize, soybean RFV was 1.19±0.4cmd−1 until the 3rd node when it increased to 3.31±0.5cmd−1 until maximum root depth occurred at the 13th node (813.6°C d after planting). The maximum root depth was similar between crops (P>0.05) and ranged from 120 to 157cm across 18 experimental treatments, and 89–90cm in two experimental treatments. Root depth did not exceed the average water table (two weeks prior to start grain filling) and there was a significant relationship between maximum root depth and water table depth (R2=0.61; P=0.001). Current models of root dynamics rely on temperature as the main control on root growth; our results provide strong support for this relationship (R2>0.76; P<0.001), but suggest that water table depth should also be considered, particularly in conditions such as the Midwest USA where excess water routinely limits crop production. These results can assist crop model calibration and improvements as well as agronomic assessments and plant breeding efforts in this region.
Introducción: En las poblaciones con elevada esperanza de vida, las personas de edad avanzada son más propensas a contraer enfermedades crónicas. Objetivo: Relacionar el envejecimiento poblacional ...con la morbimortalidad por algunas enfermedades crónicas seleccionadas en el municipio de Rafael Freyre hasta el año 2030 y su posible incidencia sobre los servicios de salud. Método: Se utilizó la ecuación compensadora para calcular la proyección de la población para el 2030 y las tasas de prevalencia y mortalidad para estimar la morbimortalidad por algunas enfermedades crónicas. Se realizó un pronóstico de población hasta el año 2030, utilizando una proyección por componentes que incluyen el comportamiento estimado de la natalidad, la mortalidad y las migraciones hasta el 2030. A la población pronosticada se le aplicaron las tasas de morbilidad para la hipertensión arterial y la diabetes mellitus y mortalidad por cáncer y enfermedades del corazón para estimar el número de enfermos y fallecidos. Resultados: Los cálculos realizados estiman el incremento de la morbilidad por hipertensión arterial del 26,1%, de la diabetes mellitus en el 34,1% y la mortalidad por enfermedades del corazón se elevará en 56,2% y por cáncer, en 47,3%, en el municipio de Rafael Freyre para el año 2030 en la población de 60 años y más. Conclusiones: El envejecimiento de la población del municipio de Rafael Freyre provocará un incremento de la morbimortalidad por enfermedades crónicas, lo que incrementará la presión asistencial sobre el sistema de salud existente. Palabras clave: envejecimiento poblacional, enfermedades crónicas, morbilidad, mortalidad, proyecciones demográficas.
Myeloma Multiple (MM) is a hematological malignancy that affects elderly patients mainly. Due to the heterogeneity of this population, a geriatric evaluation is recommended to decide first-line ...therapy. However, its application is laborious, and its use in clinical practice is not widespread, being therapeutic decisions usually made according to chronological age. The aim of this study is to evaluate the clinical characteristics and evolution of a series of 148 newly diagnosed transplant-ineligible MM patients according to different age group.
Retrospective study of patients with newly diagnosed MM, diagnosed in two tertiary hospitals in Spain, between 2015-2020. According to age at diagnosis, patients were grouped in ≤79 (Group 1; n=90) and ≥80 (Group 2; n=58) years. The International Myeloma Working Group criteria were used to evaluate treatment response.
The median (range) age of patients in Group 1 and 2 was 74 (70-79) and 83 (80-92) years, respectively. There were more patients with ECOG >2 (5.6 vs 17.2%; p=0.01) and ISS 3 (38.9 vs 53.4%; p=0.013) in Group 2. Remaining characteristics at diagnosis were similar in both groups. The most frequently administered treatments were bortezomib-based (43 patients in Group 1 and 22 in Group 2), followed by regimens with lenalidomide (18 patients in Group 1 and 20 in Group 2). Overall, 66 (73.3%) patients in Group 1 and 40 (71.4%) in Group 2 achieved partial response or better after treatment. The rate of very good partial response or better was 53.3% and 50% in Groups 1 and 2, respectively. Finally, 24 (26.6%) patients achieved complete response in Group 1 and 9 (16.1%) in Group 2 (p = 0.1). Nine (37.5%) out of 24 patients in Group 1 and 3 (33.3%) out of 9 patients in Group 2 achieved minimal residual disease negativity by flow cytometry, with a sensitivity of 10-5. With a median follow-up of 23.5 months, the progression-free survival (95%CI) of Group 1 and 2 was 33.13 (25.9-40.4) and 26.43 (16.6-36.2) months, respectively (p = 0.680). Median overall survival was 50.4 (33.4-67.4) months in ≤79 years and 28.1 (22.5-33.6) months in ≥80 years (p = 0.014). Overall, 38 patients from Group 1 and 33 from Group 2 have died, being infections the leading cause of death in both groups. It should be noted that 22 patients (24%) of Group 1 and 24 (41%) of Group 2 did not reach second line of therapy.
Patients aged ≥80 years often have a worse general condition at diagnosis, but the rest of the baseline clinical characteristics are similar to those of patients aged ≤79. There were no differences in terms of the rate and quality of responses between both groups of patients. There was a high attrition rate, particularly among patients ≥80 years, highlighting the need to design specific therapeutic strategies for this fragile group of patients.
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