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Agricultural irrigation is a significant contributor to freshwater consumption. However, the current irrigation systems used in the field are not efficient. They rely mainly on soil moisture sensors and the experience of growers but do not account for future soil moisture loss. Predicting soil moisture loss is challenging because it is influenced by numerous factors, including soil texture, weather conditions, and plant characteristics. This article proposes a solution to improve irrigation efficiency, which is called DRLIC (deep reinforcement learning for irrigation control). DRLIC is a sophisticated irrigation system that uses deep reinforcement learning (DRL) to optimize its performance. The system employs a neural network, known as the DRL control agent, which learns an optimal control policy that considers both the current soil moisture measurement and the future soil moisture loss. We introduce an irrigation reward function that enables our control agent to learn from previous experiences. However, there may be instances in which the output of our DRL control agent is unsafe, such as irrigating too much or too little. To avoid damaging the health of the plants, we implement a safety mechanism that employs a soil moisture predictor to estimate the performance of each action. If the predicted outcome is deemed unsafe, we perform a relatively conservative action instead. To demonstrate the real-world application of our approach, we develop an irrigation system that comprises sprinklers, sensing and control nodes, and a wireless network. We evaluate the performance of DRLIC by deploying it in a testbed consisting of six almond trees. During a 15-day in-field experiment, we compare the water consumption of DRLIC with a widely used irrigation scheme. Our results indicate that DRLIC outperforms the traditional irrigation method by achieving water savings of up to 9.52%. [ABSTRACT FROM AUTHOR]

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Aims: Kura clover living mulch (KCLM) is thought to provide in-season nitrogen (N) to the cash crop. Because of interactions between cropping system and crop performance, the magnitude of in-season N inputs from KCLM cannot be quantified using common N rate research methods. We aim to quantify the timing and magnitude of these N inputs using clover biomass and decomposition data. Methods: This research measured the temporal distribution of clover biomass with intensive sampling, vertical biomass distribution using bead tracer analysis, and residue decomposition using in situ litter bags. These data were used as inputs to a model that estimated the in-season N contributions from KCLM. Results: Our results found that spring management contributed 7–23 kg N ha−1 during the first 6 weeks of the growing season, while shade suppression contributed 59 – 84 kg N ha−1 from mid-June to mid-October. Daily N inputs peaked on 8 August at 1.14 kg N ha−1 d−1. When these estimates were added to fertilizer N inputs and analyzed against crop N uptake, we found that the maize took up 88% of the total N inputs and fertilizer recovery efficiency was 56%. Conclusions: This study provides a methodology which generates estimates that may be used in research related to N cycling and management in KCLM and other legume intercropping systems. [ABSTRACT FROM AUTHOR]

A personal narrative is presented which explores the author's experiences and interactions with Professor Dan Mandelker, reflecting on various aspects of his character and the impact he had on their professional life.

The terrestrial vegetation GPP of Qinghai Province is an important variable that characterizes the carbon cycling pattern. However, there is still a lack of a high-resolution GPP dataset for Qinghai Province. To address this issue, we processed all Landsat images of Qinghai from 1987 to 2021 using the GEE, and we combined multi-source auxiliary data to estimate GPP using the revised EC-LUE model. We compared our GPP dataset with flux observations to verify its accuracy. The results showed that our GPP dataset had a high correlation with the flux tower observations, with correlation coefficients of 0.984 at CF-AM site and 0.976 at CN-Ha2 site, respectively, and each site had an RMSE of $11.960\, \rm g C\cdot m^{-2}\cdot 16d^{-1}$ 11.960 g C ⋅ m − 2 ⋅ 16 d − 1 and 12.986 $\rm g C\cdot m^{-2}\cdot 16d^{-1}$ g C ⋅ m − 2 ⋅ 16 d − 1 , respectively. There are different deviations between our GPP dataset and the mainstream GPP datasets in various vegetation types, with the average correlation coefficient ranging from 0.431 to 0.943. By comparing with the flux observations and the related analysis, we demonstrated that our GPP dataset features better accuracy, higher spatial resolution, and more temporal coverage than mainstream GPP datasets. This study offers the first long-term high-resolution GPP dataset for Qinghai Province, and we believe that this dataset has important implications for ecological management and climate research. [ABSTRACT FROM AUTHOR]

Reconstructing the history (spatio-temporal patterns) of biological invasions at a small spatial scale is challenging, notably because the required data are often not available in sufficient quantity and quality. In this study, we present a mixed approach using six different data sources to explore the spreading history of four non-native invasive tree species, Ailanthus altissima, Celtis occidentalis, Prunus serotina and Acer negundo in a high conservation value foreststeppe habitat with an area of 1000 ha (Peszér Forest, Central Hungary). We carried out a literature search, compiled all the archived and currently valid data of the National Forestry Database (NFD) in a GIS database, conducted a full-coverage field survey, mapped all the large/old tree specimens and carried out annual ring counts, performed a hotspot analysis on the abundance data provided by the field survey and gathered local knowledge. Each of these approaches proved indispensable and their complementary use made it possible to reconstruct the invasion history of all four tree species. According to the available source literature, P. serotina was first planted in the area in 1937 and the first known occurrence of A. altissima could also be traced back to the 1930s. The examination of large specimens of C. occidentalis and querying the NFD for data related to A. negundo provided evidence that these species have been present in the area since at least the 1940s. However, based on the NFD and local knowledge, it is certain that the rapid expansion of the four tree species occurred simultaneously and only around the turn of the millennium, with a lag of at least 60-70 years. The exploration of local knowledge revealed three possible explanations, which interestingly also coincided in time. With the change in the political regime, the intensity of forest use started to decrease in the 1990s, the population of game was drastically reduced at the end of the decade and droughts became more frequent from 2000 onwards. The field survey clearly showed that these tree species were 2-3 times more prevalent and abundant than the relevant NFD data indicated. Finally, the primary hotspots of A. altissima and A. negundo overlapped with the locations of their first known occurrences, while in the case of C. occidentalis and P. serotina, they did not. However, local knowledge revealed that the former two had been ignored since at least the 1950s, while the latter two were occasionally planted until the 1990s. It is likely that the primary hotspots of C. occidentalis and P. serotina indicate the locations of these undocumented plantations. [ABSTRACT FROM AUTHOR]

Row establishment is important to mitigate competition with maize (Zea mays L.) seedlings in a kura clover (Trifolium ambiguum Bieb.) living mulch (KCLM). This study investigated the effect of row-establishment and fertilizer nitrogen (N) rate on maize yield and N uptake in a KCLM system in Arlington, WI, and Rosemount, MN, during the 2021 growing season. Row establishment treatments included rotary zone tillage (RZT), shank strip-tillage (ST), and banded herbicides (BH), each evaluated at six N rates from 0 to 225 kg N ha-1. Extended periods of moderate and severe drought were experienced during the study period. The Arlington and Rosemount sites received 64 and 63% of the normal precipitation between 20 Apr. and 31 Oct. 2021, but poor distribution and higher temperatures at Rosemount elevated drought severity indices at that site. Grain yields at Rosemount were 3.6 Mg ha-1, whereas Arlington produced yields that matched expectations for the area (10Mg ha-1). Row establishment affected maize grain yield differentially at each site, where, under severe drought conditions, BH maximized maize yield, whereas under moderate drought conditions, the higher level of tillage (RZT) maximized maize yield. These responses are most likely attributed to reduced moisture loss in the row-zone of the BH treatment and the greater level of clover suppression in the RZT treatment and their interactions with specific weather conditions at the research sites. Results from this study indicate that row establishment methods in a KCLM cropping system should be considered with spring environmental conditions and the expected weather outlook. [ABSTRACT FROM AUTHOR]

The composition of proanthocyanidins in the testa (seed coat) of bread wheat was analyzed by thiolysis of PA oligomers from developing grain and found to consist of (+)‐catechin monomers, with a small amount of (+)‐gallocatechin. The average chain length of soluble PA stayed relatively constant between 10 and 20 days post‐anthesis, whereas that of unextractable PA increased over the same period, suggesting that increases in chain length might account for the insolubility of PAs from mature wheat grain. We carried out RNA‐Seq followed by differential expression analysis from dissected tissues of developing grain from red‐ and white‐grained near‐isogenic lines differing in the presence of an active R gene that encodes a MYB transcription factor involved in control of PA biosynthesis. In addition to genes already identified encoding chalcone synthase, chalcone isomerase, flavanone 3‐hydroxylase, and dihydroxyflavonoid 4‐reductase, we showed that wheat genes encoding phenylalanine ammonia lyase, flavonoid 3′,5′‐hydroxylase, leucoanthocyanidin reductase, and a glutathione S‐transferase (the orthologue of maize Bronze‐2) were more highly expressed in the red NIL. We also identified candidate orthologues of other catalytic and regulatory components of flavonoid biosynthesis in wheat. [ABSTRACT FROM AUTHOR]

Provides information on a study that analyzed a long-term record of monthly average below-ground temperatures at a mid-latitude site to determine heat flux and heat storage. Methodologies used; Results and discussion; Conclusions.

The US Corn Belt is a global hotspot of atmospheric ammonia (NH3), a gas known to adversely impact the environment and human health. We combine hourly tall tower (100 m) measurements and bi‐weekly, spatially distributed, ground‐based observations from the Ammonia Monitoring Network with the US National Emissions Inventory (NEI) and WRF‐Chem simulations to constrain NH3 emissions from April to September 2017–2019. We show that: (1) NH3 emissions peaked from May to July and were 1.6–1.7 times the annual NEI average; (2) average growing season NH3 emissions from agricultural lands were remarkably similar across years (3.27–3.64 nmol m−2 s−1), yet showed substantial episodic variability driven by meteorology and land management; (3) dry deposition was 40% of gross emissions from agricultural lands and exceeded 100% of gross emissions in natural lands. Our findings provide an important benchmark for evaluating future NH3 emissions and mitigation efforts. Key Points: Rare multiyear tall tower and ground‐based ammonia measurements were combined with WRF‐Chem to constrain emissions from the US Corn BeltMonthly ammonia emissions peaked in May through July and were 1.6–1.7 times the annual NEI averageEpisodic low WRF‐Chem bias versus tall tower observations underscore the importance of weather and land management as emission drivers [ABSTRACT FROM AUTHOR]

Author's Synopsis: This Article reviews the competing demands free speech law makes when applied to sign and billboard ordinances. It describes the free speech doctrines that apply, explains ambiguities and conflicts, and makes recommendations for sign regulations that can avoid constitutional problems. The Article first explains how state courts decided the constitutionality of billboard controls before free speech law applied. It then describes the litigation problems municipalities face in sign litigation, and considers the overbreadth and severability doctrines that litigants can use to strike sign ordinances down. Ordinances that regulate signs typically regulate commercial speech. The Article explains the criteria the Supreme Court adopted for laws that regulate commercial speech, and how the Court liberally applied these criteria in a case upholding an ordinance that prohibited billboards. Lower court cases that applied this case are discussed next. They followed the Supreme Court's approach in billboard cases but sometimes added new requirements. The Article then describes the free speech time, place, and manner rules that are an alternative to commercial speech doctrine, and how courts apply these rules to sign ordinances. Regulations for digital billboards are discussed next. The Article concludes by discussing the constitutional protections courts provide for noncommercial speech, and the constitutional restrictions they require for signs that regulate content. [ABSTRACT FROM AUTHOR]

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) was launched to the International Space Station on 29 June 2018 by the National Aeronautics and Space Administration (NASA). The primary science focus of ECOSTRESS is centered on evapotranspiration (ET), which is produced as Level‐3 (L3) latent heat flux (LE) data products. These data are generated from the Level‐2 land surface temperature and emissivity product (L2_LSTE), in conjunction with ancillary surface and atmospheric data. Here, we provide the first validation (Stage 1, preliminary) of the global ECOSTRESS clear‐sky ET product (L3_ET_PT‐JPL, Version 6.0) against LE measurements at 82 eddy covariance sites around the world. Overall, the ECOSTRESS ET product performs well against the site measurements (clear‐sky instantaneous/time of overpass: r2 = 0.88; overall bias = 8%; normalized root‐mean‐square error, RMSE = 6%). ET uncertainty was generally consistent across climate zones, biome types, and times of day (ECOSTRESS samples the diurnal cycle), though temperate sites are overrepresented. The 70‐m‐high spatial resolution of ECOSTRESS improved correlations by 85%, and RMSE by 62%, relative to 1‐km pixels. This paper serves as a reference for the ECOSTRESS L3 ET accuracy and Stage 1 validation status for subsequent science that follows using these data. Key Points: ECOSTRESS is a state‐of‐the‐art combination of thermal bands, spatial and temporal resolutions, and measurement accuracy and precisionData from 82 eddy covariance sites were coalesced concurrently with the first year of ECOSTRESS for Stage 1 validationClear‐sky ET from ECOSTRESS compared well against a wide range of eddy covariance sites, vegetation classes, climate zones, and times of day [ABSTRACT FROM AUTHOR]

Atmospheric ammonia (NH3) has increased dramatically as a consequence of the production of synthetic nitrogen (N) fertilizer and proliferation of intensive livestock systems. It is a chemical of environmental concern as it readily reacts with atmospheric acids to produce fine particulate matter and indirectly contributes to nitrous oxide (N2O) emissions. Here, we present the first tall tower observations of NH3 within the U.S. Corn Belt for the period April 2017 through December 2018. Hourly average NH3 mixing ratios were measured at 100 and 56 m above the ground surface and fluxes were estimated using a modified gradient approach. The highest NH3 mixing ratios (>30 nmol mol−1) occurred during early spring and late fall, coinciding with the timing of fertilizer application within the region and the occurrence of warm air temperatures. Net ecosystem NH3 exchange was greatest in spring and fall with peak emissions of about +50 nmol m−2 s−l. Annual NH3 emissions estimated using state‐of‐the‐art inventories ranged from 0.6 to 1.4 × the mean annual gross tall tower fluxes (+2.1 nmol m−2 s−1). If the tall tower observations are representative of the Upper Midwest and broader U.S. Corn Belt regions, the annual gross emissions were +720 Gg NH3‐N y−1 and +1,340 Gg NH3‐N y−1, respectively. Finally, considering the N2O budget over the same region, we estimated total reactive N emissions (i.e., N2O + NH3) of approximately 1,790 Gg N y−1 from the U.S. Corn Belt, representing ~23% of the current annual new N input. Key Points: Observations of NH3 from a tall tower (100 m) provide insights regarding regional emissions from the US Corn BeltAnnual NH3 emissions estimated using state‐of‐the‐art inventories were 0.6 to 1.4‐fold compared to the tall tower flux densityAnnual gross emission estimates for the Upper Midwest and broader US Corn Belt regions were +720 Gg NH3‐N y−1 and +1340 Gg NH3‐N y−1 [ABSTRACT FROM AUTHOR]

Core Ideas: Several methods of overseeding a winter rye cover crop into soybean were tested.Tractor‐mounted seeders reduced soybean yield by 4% relative to an aerial seeder.Each seeder was equally variable across the seeding path with an average CV of 34%.Rye growth was influenced by weather and possibly by seeding density (a covariate).Seeding rate and timing may be more important factors than choice of equipment. In the upper Midwest, short growing seasons make it difficult to establish cover crops in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations. Overseeding before cash crop harvest may allow more time for growth, but practical methods need to be evaluated. Over 2 yr, this study assessed three winter rye (Secale cereale L.) overseeding techniques into standing soybean in mid‐September: aerial seeding (AS), tractor‐mounted air‐flow spreader (TAF), and tractor‐mounted fertilizer broadcast spreader (TBS). All treatments had equal variability in seeding density across plots. When rye was overseeded using the TAF and TBS treatments, soybean yield was reduced by approximately 4% relative to the AS treatment. In spring, seeding treatments impacted aboveground biomass production and N uptake in a year with good growing conditions (2010–2011), but not in a year with poor growth conditions (2011–2012). The impact of seeding method in the first year of the study was more likely due to differences in seeding density of the treatments, which was used as a covariate in this study. In a year with good growing conditions, the treatments with lower seeding densities had more spring biomass production, likely due to compensatory growth. Overall, measured values of aboveground biomass ranged from 39 to 467 kg ha−1, whereas aboveground N uptake ranged from 2.1 to 15.3 kg ha−1. Based on these findings, research efforts should focus on evaluating optimal seeding rates and timing, rather than choice of seeding method, to reduce impact on soybean yields and maximize cover crop benefits. [ABSTRACT FROM AUTHOR]

A source of thermal, ground-state atomic oxygen has been used to expose thin copper films at a flux of 1.4×1017 atoms/cm2 s for times up to 50 min for each of five temperatures between 140 and 200 °C. Rutherford backscattering spectroscopy was used to characterize the oxide formed during exposure. The observations are consistent with the oxide phase Cu2O. The time dependence and the temperature dependence of the oxide layer thickness can be described using oxide film growth theory based on rate limitation by diffusion. Within the time and temperature ranges of this study, the growth of the oxide layers is well described by the equation L(T,t)=3.6×108 exp(-1.1/2kBT)t12, where L, T, and t are measured in angstroms, degrees Kelvin, and minutes, respectively. The deduced activation energy is 1.10±0.15 eV, with the attendant oxidation rate being greater than that for the corresponding reaction in molecular oxygen. [ABSTRACT FROM AUTHOR]

Abstract: Aerodynamic canopy height (ha) is the effective height of vegetation canopy for its influence on atmospheric fluxes and is a key parameter of surface‐atmosphere coupling. However, methods to estimate ha from data are limited. This synthesis evaluates the applicability and robustness of the calculation of ha from eddy covariance momentum‐flux data. At 69 forest sites, annual ha robustly predicted site‐to‐site and year‐to‐year differences in canopy heights (R2 = 0.88, 111 site‐years). At 23 cropland/grassland sites, weekly ha successfully captured the dynamics of vegetation canopies over growing seasons (R2 > 0.70 in 74 site‐years). Our results demonstrate the potential of flux‐derived ha determination for tracking the seasonal, interannual, and/or decadal dynamics of vegetation canopies including growth, harvest, land use change, and disturbance. The large‐scale and time‐varying ha derived from flux networks worldwide provides a new benchmark for regional and global Earth system models and satellite remote sensing of canopy structure. [ABSTRACT FROM AUTHOR]

Abstract: Indirect nitrous oxide (N2O) emissions from drainage ditches and headwater streams are poorly constrained. Few studies have monitored stream N2O emissions and fewer modeling studies have been conducted to simulate stream N2O emissions. In this study, we developed direct and indirect N2O emission modules and a corresponding calibration module for use in the Soil and Water Assessment Tool (SWAT) model, and implemented the expanded SWAT model (termed SWAT‐N2O) to a representative fourth‐stream‐order catchment (210 km2) and six first‐order stream catchments (0.22–1.83 km2) in southeastern Minnesota. We simulated the spatial and temporal fluctuations of the indirect emissions from streams, identified emission “hot spots” and “hot moments,” and diagnosed the correlations between direct and indirect emissions. We showed that zero‐order streams and first‐order streams could contribute 0.034–0.066 and 0.011 nmol N2O m−2 s−1 (expressed on the basis of unit catchment area) to the total surface emissions, respectively. Emissions from zero‐order and first‐order streams equal 24–41% of direct emissions from soil, which may explain the emission gap between calculations using top‐down and bottom‐up methods. Clear spatial patterns were identified for both direct and indirect emissions and their spatial variations were negatively correlated. Our results suggest that the IPCC N2O emission factor for streams in the Corn Belt should be increased by 3.2–5.7 times. Increasing precipitation and streamflow in the Corn Belt may potentially increase frequencies of soil anoxic conditions and nitrate leaching to streams, and subsequently increase N2O emissions from both soils and streams. [ABSTRACT FROM AUTHOR]

Cover crops can provide ecological services and improve the resilience of annual cropping systems; however, cover crop use is low in corn (Zea mays L.)--soybean [Glycine max (L.) Merr.] rotations in the upper Midwest due to challenges with establishment. Our objective was to compare three planting methods to establish cover crops (winter rye [Secale cereale L. 'Rymin'], red clover [Trifolium pretense L. 'Medium'], hairy vetch [Vicia villosa Roth], field pennycress [Thlaspi arvense L. 'MN-106'], and a mixture of oat [Avena sativa L.], pea [Pisum sativum L.], and tillage radish [Raphanus sativus L.]) (MIX) in corn at the seven-leaf collar stage. Planting methods included directed broadcast into the inter-row (DBC), directed broadcast with light incorporation (DBC+INC), and a high-clearance drill (DRILL). The DRILL method achieved greater fall biomass than DBC for all species except pennycress, and DRILL and DBC+INC increased red clover and hairy vetch spring biomass compared with DBC. Cover crops did not affect corn grain or silage yield and reduced yield of the subsequent soybean crop by 0.4 Mg ha-1 (10%) only when poor termination of hairy vetch occurred at one site. Cover crops with >390 kg ha-1 of spring biomass reduced soil nitrate- N compared with the no-cover control. These results support that cover crops can be interseeded into corn at the seven-leaf collar stage in the upper Midwest to reduce soil nitrate-N while maintaining corn and subsequent soybean yields; however, effective cover crop termination is critical to avoid competition with the subsequent soybean crop. [ABSTRACT FROM AUTHOR]

Abstract: The methane (CH4) budget and its source partitioning are poorly constrained in the Midwestern United States. We used tall tower (185 m) aerodynamic flux measurements and atmospheric scale factor Bayesian inversions to constrain the monthly budget and to partition the total budget into natural (e.g., wetlands) and anthropogenic (e.g., livestock, waste, and natural gas) sources for the period June 2016 to September 2017. Aerodynamic flux observations indicated that the landscape was a CH4 source with a mean annual CH4 flux of +13.7 ± 0.34 nmol m−2 s−1 and was rarely a net sink. The scale factor Bayesian inversion analyses revealed a mean annual source of +12.3 ± 2.1 nmol m−2 s−1. Flux partitioning revealed that the anthropogenic source (7.8 ± 1.6 Tg CH4 yr−1) was 1.5 times greater than the bottom‐up gridded United States Environmental Protection Agency inventory, in which livestock and oil/gas sources were underestimated by 1.8‐fold and 1.3‐fold, respectively. Wetland emissions (4.0 ± 1.2 Tg CH4 yr−1) were the second largest source, accounting for 34% of the total budget. The temporal variability of total CH4 emissions was dominated by wetlands with peak emissions occurring in August. In contrast, emissions from oil/gas and other anthropogenic sources showed relatively weak seasonality. [ABSTRACT FROM AUTHOR]

Core Ideas: Corn–soybean and continuous corn had similar soil water dynamics and N leaching.Urea and anhydrous ammonia resulted in similar leachate nitrate concentrations.The kura clover cropping system reduced drainage, N leaching, and fall soil N. Improving water quantity and quality impacts of corn (Zea mays L.)‐ and soybean [Glycine max (L.) Merr.]‐based cropping systems is a key challenge for agriculture in the US Midwest. Long‐term field experiments are important for documenting those effects and exploring possible solutions. This study examines differences in soil water dynamics and nitrate‐nitrogen (N) leaching among cropping systems and N fertilizer sources in a long‐term experiment in southeastern Minnesota. Drainage and leachate concentrations were measured for 4 yr using automated equilibrium tension lysimeters installed below the root zone in replicated, large plots on a well‐drained silt loam soil. Soil water storage was monitored using water content reflectometers. Corn–soybean and continuous corn cropping systems exhibited similar soil water dynamics, drainage rates (145–202 mm yr−1), leachate nitrate N concentrations (21.3–25.6 mg L−1), and nitrate N leaching loads (30–75 kg ha−1 yr−1). Nitrate‐N concentrations in the leachate were similar whether N was added as urea (21.2 mg L−1) or anhydrous ammonia (25.7 mg L−1). A perennial kura clover (Trifolium ambiguum M. Bieb)‐based cropping system with no N fertilizer significantly altered soil water dynamics and resulted in lower (p < 0.10) drainage rates (53 mm yr−1), nitrate N concentrations (7.1 mg L−1), and nitrate N leaching loads (2–5 kg ha−1 yr−1) compared with corn–soybean or continuous corn, but also reduced corn grain yields. These impacts are generally consistent with a growing body of literature showing substantial environmental benefits of a kura clover living mulch system for corn production, but the economic viability of such a system is not yet proven. [ABSTRACT FROM AUTHOR]