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Breeding towards root-centric ideotypes can be a relatively quick trait-based strategy to improve crop resource use efficiency. Irrigated agriculture represents a crucial and expanding sector, but its unique parameters require traits distinct from previously proposed rainfed ideotypes. We propose a novel irrigated ideotype that integrates traits across multiple scales to enhance resource use efficiency in irrigated agroecosystems, where resources are concentrated in a relatively shallow ‘critical zone’. Unique components of this ideotype include rapid transplant recovery and establishment, enhanced exploitation of localized resource hotspots, adaptive physiological regulation, maintenance of hydraulic conductivity, beneficial rhizosphere interactions, and salinity/waterlogging avoidance. If augmented by future research, this target could help to enhance agricultural sustainability in irrigated agroecosystems by guiding the creation of resource-efficient cultivars. [ABSTRACT FROM AUTHOR]

Integrated nitrogen (N) management strategies could make significant contributions to improving the efficiency of N use in the northern Corn Belt, particularly for maize, which has high N requirements. Using legume cover crops has been shown to increase both the soil's capacity to supply N and nitrogen use efficiency (NUE), through the reduction in the amount of N fertilizer that must be applied to the following crops. However, the impact of non-legume crops such as winter wheat ( Triticum aestivum L.) on the diminishing return function between crop yield and N supply and its influence on N fertilizer use remains unclear. We hypothesized that maintaining wheat in short maize and soybean- based rotations is instrumental to improve cropping system performance and increase N fertilizer use efficiency while decreasing N requirements for maize. Seven maize and soybean rotations with different frequency of winter wheat with or without underseeded red clover ( Trifolium pratense L. ) were grown in two tillage systems (conventional and zone-tillage) and four long-term N regimes in Ridgetown, ON, Canada (2009–2013). Wheat in the rotation increased maize and soybean yields, negated crop yield lags due to zone-tillage, and decreased maximum economic rates of fertilizer N (MERN). The benefits of wheat in the rotation on maize yield were negated by high N rates; however, similar yields were obtained with lower N levels in rotationally grown maize, resulting in a 17% (conventional till) to 21% (zone-till) increase in partial factor productivity for N fertilizer at MERN (PFP MERN ). While N benefits to crops following wheat alone may be attributed to a higher indigenous plant available soil N, underseeding red clover further increased the agronomic efficiency (AE) of N fertilizer (AE MERN ) up to 32%. Maize yields were also less limited by N supply and less responsive to N fertilization when grown in rotation with wheat, especially in the zone-till system. These results highlight the value of wheat as a system component of dominant maize/soybean short rotations of Ontario and its potential to increase both maize and soybean productivity using less N input. [ABSTRACT FROM AUTHOR]

Highlights: [•] Soft winter wheat and red clover respond inversely to N supply in relay cropping. [•] Reducing N rate by 10–12% increased economic benefits and return to N derived from red clover without significantly reducing wheat yields. [•] We show that high N rate increase red clover stand heterogeneity and may compromise benefits form relay cropping. [•] Different approaches toward N fertilization are necessary to improve the environmental and economic benefits of relay cropping. [Copyright &y& Elsevier]

Across the world, an increasing number of farmers are piloting agroecological systems. The recoupling of crops and livestock is one type of agroecological practice that has potential to help reduce the use of off-farm inputs, improve soil quality, and reduce costs for farmers. Yet, a major part of the world's agricultural landscapes remain dominated by conventional specialized crop and livestock practices. In particular, grazing animals in perennial cropping systems may reduce pesticide and fuel use, decrease labor, and build soil organic carbon and soil fertility. In this study, we examined adopters and non-adopters' perceptions of a niche system, integrated sheep-vineyard systems (ISVS) in California. We aimed at understanding the conditions under which ISVS, a specific case of ICLS (integrated crop-livestock systems), could be mainstreamed. We then contextualized these interviews using the Multi-Level Perspective framework to analyze the levers favoring or impeding mainstreaming of this niche system. We considered both pull factors arising from changes in the landscape, and push factors arising through decentralized, grassroot processes. Our inductive analysis is a promising first insight into farmers' perceptions and motivations toward ISVS adoption in California, considering both vineyard managers and contractors (i.e. shepherds renting their sheep to vineyard managers). We found a positive perception of ISVS among both current adopters and non-adopters regarding the potential agronomic, environmental and economic benefits of these practices. All adopters were satisfied with this system as they experienced labor and fuel savings, soil quality improvement and marketing advantages. Local push factors (bottom-up levers emerging from the niche systems) were highlighted by interviewees as contributing to adoption. Push factors identified include knowledge exchange and networking between vineyard managers and developing marketing pathways for "carbon-positive" wool, meat and wine products. However, some pull factors (macro-economic and policy levers acting as top-down levers) could help move the system beyond limited adoption. We point out biotechnical and socio-economic research avenues to encourage the scaling-up of ISVS and ICLS more broadly. On the biotechnical dimension, we recommend continuing and scaling-out system experiments to redesign vineyards considering sheep integration and evaluate the effect of grazing on soil quality and fire management. On the socio-economic dimension, we encourage the exploration of relevant spatial scenarios through co-design of collaborative arrangements between vineyard managers and contractors at the landscape level. Greater research on the social, environmental and economic services provided by ISVS is urgently needed to inform state and federal agricultural policies, including whether such systems should be supported through payment for ecosystem services and as part of environmental good practices and fire safety recommendations. • We highlighted positive perception of ISVS among current adopters and non-adopters. • ISVS allowed labor and fuel saving, soil quality improvement and marketing options. • A major barrier was related to the complexity of sheep management in vineyards. • Knowledge exchange between farmers and policy levers are needed to mainstream ISVS. • Biotechnical and socio-economic research is needed to encourage ISVS scaling-up. [ABSTRACT FROM AUTHOR]

While characteristics of semi-arid climates place limitations on soil organic carbon (SOC) storage, there is opportunity and urgency for increasing the quality and long-term persistence of cropland SOC content within these agroecosystems. Livestock re-integration into cropland shows potential to improve semi-arid agroecosystem functioning through shifts in biogeochemical processes and the facilitation of multiple ecosystem services involved in carbon and nutrient cycling and use-efficiency. Here we review the characteristics of grazing-based Integrated Crop-Livestock (ICL) systems and how various associated management practices may interplay with semi-arid agroecological and biogeochemical dynamics to influence soil microbial ecology and SOC accumulation and stabilization. We argue that livestock re-integration holds notable potential to increase cropland SOC through controls on landscape net primary productivity, allocation of biomass belowground, efficient recycling of residual crop nutrients, and soil biological activity related to a suite of soil ecosystem services. Achieving the full SOC accumulation potential of ICL management will require site-specific consideration of feedbacks between herbivory, soil microbial ecology, soil disturbance, and forage species interactions. Future research should focus on optimizing plant-soil-grazer feedbacks and understanding of mechanistic drivers of ICL system outcomes to optimize the design and management of semi-arid regional ICL systems for enhanced SOC quality and persistence. Image 1 • Semi-arid ecoregions face high vulnerability to global climate change impacts. • Grazing influences cropland net primary productivity and soil carbon partitioning. • Crop-livestock integration impacts multiple soil carbon stabilization pathways. • Plant-soil-grazer feedbacks alter nutrient stoichiometry and soil microbial ecology. • Reduced tillage, moderate intensity rotational grazing, and biodiverse forage mixtures facilitate potential ICL benefits. [ABSTRACT FROM AUTHOR]

A key strategy for climate change adaptation in the rain-fed northern Corn Belt is to decrease cropping system vulnerability to changes in precipitation patterns by building resilience. Using 50- year of county level yield and environmental data from Iowa and Ontario, we first demonstrate that sensitivity of corn yield to precipitation, particularly in July and August, has increased over the past five decades despite no changes in precipitation patterns. This can be attributed to steady improvement in corn yield potential and so plant water demand since the mid-20th century and removal of non-water constraints to crop production. Such vulnerability of corn-based cropping systems to water limitations is of increasing concern as climate change models predict higher summer temperatures and year-to-year variations in precipitations in this region. As suggested in the ecology literature, increasing agroecosystem temporal and spacial diversity is one of the key management strategies to deal with impending weather variability. Using yield and environmental data from a 30-year long-term rotation and tillage trial in Ontario, we show that diversification of short corn-based rotations using small grains and forage crops increases corn yield stability and resilience to both limiting and excess soil moisture1. We also demonstrate the importance of conservation tillage and measured the impact of rotation and tillage history on plants ability to access water resources, plant available soil water and their combined effects on timing of physiological water stress and grain yield when drought occurs at reproductive stages. Our results emphasize the growing importance of developing strategies for managing soil moisture in rain-fed regions and the significance of agroecological approaches to develop hardy agricultural systems and protect food and feed production against the upcoming extreme weather events. [ABSTRACT FROM AUTHOR]

Agroecosystems are on both the receiving and contributing ends of increasingly demanding climatic and environmental conditions. Maintaining productive systems under resource scarcity and multiplicative stresses requires precise monitoring and systems-scale planning. By incorporating ecological resilience into agroecosystems research we can gain valuable insight into agroecosystem identity, change, responsivity, and performance under stress, but only if we move away from resilience as a mere touchstone concept. Using the productivity, stability, resistance, and recovery of system processes as a basic framework for resilience monitoring, we propose quantitative research approaches to tackle the continuing lack of biophysical, field-scale indicators needed to lend insight into dynamic resilience variables and mechanisms. We emphasize the importance of considering productive functions, sources of system regulation and disturbance, and cross-scale interactions when applying resilience theory to agroecosystems. Agroecosystem resilience research requires understanding of multiple scales and speeds of influence both above and below the focal scale. When these considerations are addressed, resilience theory can add tangible value to agroecosystems research, both for the purposes of monitoring current systems and of planning future systems that can reconcile productivity and sustainability goals. [ABSTRACT FROM AUTHOR]

• Fall-applied CM led to more complete decomposition and greater C stabilization. • Fall-applied CM significantly increased volumetric water content by 22% in year one. • Fall-applied CM increased soil water retention between 0 to ˜100 kPa by 13%. • The greatest benefit from OMA use may be when irrigation supplies are limited. • OMA use in young orchards could have a long-term impact on orchard productivity. Permanent crops like almond (Prunus dulcis) require significant water inputs for economic yields and long-term productivity. This demand creates a challenge in drought-prone regions like California. Use of organic matter amendments (OMA) can improve water use efficiency by conserving soil moisture and reducing tree water stress. The majority of almond orchards in California are no-till with irrigation targeted on a narrow tree berm where OMA is applied as surface mulch. We examined the effects of composted dairy manure (CM) and the timing of its application on soil moisture, soil water retention and tree water status in a young orchard planted in 2014. Treatments including Fall-applied CM (October 2015 and 2016), Spring-applied CM (April 2016 and 2017) and an unamended control were monitored during the 2016 and 2017 growing seasons. Fall-applied CM was more readily incorporated in soil organic matter of the 0–60 cm rooting zone as evidenced by significantly greater soil organic carbon (SOC) for Fall versus Spring-applied CM in 2016 (p < 0.05). Fall-applied CM significantly increased soil volumetric water content (VWC) by 22% from 0 to 150 cm depth during the driest period of year one and tended to make midday stem water potential (SWP) less negative relative to the control. Fall-applied CM tended to increase VWC in 2017, but treatment differences were no longer significant. Differences in VWC and SWP between Fall-applied CM and the control were most apparent at low VWC (<10%). Two years of Fall-applied CM increased soil water retention between 0 to ˜100 kPa at 0–10 cm depth by 13% compared to the control. These results demonstrate Fall-applied CM was more effective at enhancing soil moisture retention and reducing tree water stress compared to Spring-applied CM. We also conclude OMA use may buffer against periods of limited water supply for young trees. [ABSTRACT FROM AUTHOR]

Continuously flooded rice systems are a major contributor to global rice production and food security. Allowing the soil to dry periodically during the growing season (such as with alternate wetting and drying irrigation - AWD) has been shown to decrease methane emissions, water usage, and heavy metal accumulation in rice grain. However, the effects of AWD on rice yields are variable and not well understood. A two-year study was established to quantify the impacts of a range of treatments differing in AWD severity (degree of soil drying between flooding events) on yield (as well as factors that may affect yields), soil hydrology in the soil profile, and grain arsenic (As) concentrations relative to a continuously flooded control (CF). Three AWD treatments of increasing severity were imposed between full canopy cover (around 45 days after sowing) and 50% heading: AWD-Safe (field was reflooded when the perched water table reached 15 cm below the soil surface) and AWD35 and AWD25 (field was reflooded when the soil volumetric water content at 0–15 cm depth reached 35% and 25%, respectively). During the drying periods, the 0–15 cm soil layer in the AWD-Safe remained saturated, whereas in AWD35 and AWD25 the soil dried to the desired volumetric water contents. In contrast, soil moisture at 25–35 cm below the soil surface was similar across all treatments. Yield was not reduced in any of the AWD treatments, compared to the CF control. There were no consistent differences in yield components, 13 C discrimination, and N dynamics. Results suggest that the availability of water and the presence of roots at the 25–35 cm soil depth during the drying periods ensured that the crop did not suffer drought stress and thus yields were maintained. Grain As concentration in the AWD-Safe treatment was similar to that in the CF control but decreased by 56–68% in AWD35 and AWD25. AWD-Safe is often promoted as a means of practicing AWD without reducing yields; however, in this study this practice did not reduce grain As concentration because the soil did not reach an unsaturated state. These findings demonstrate that knowledge of surface and subsurface hydrology, and the root system are important for understanding the potential of AWD. [ABSTRACT FROM AUTHOR]

Subsurface drip (SSD) irrigation is becoming increasingly prevalent in drought-prone irrigated agroecosystems thanks to greater yields and irrigation water productivity (IWP) and decreased weed pressure. However, potential tradeoffs for soil health and biogeochemical cycles remain unclear, especially in organic systems that rely on soil ecosystem services and biological processes for productivity. Gains in IWP and weed control were evaluated with respect to shifts in soil biological and physicochemical parameters in an organic processing tomato ( Solanum lycopersicum L.) agroecosystem. Yield, IWP, and spatial distribution of soil resources and microbial processes were measured in furrow and SSD irrigated organic processing tomato on long term organic fields. Higher IWP and lower weed density under SSD confirm known benefits, while altered distributions of inorganic N, salinity, microbial activity, and C/N cycling enzyme activities as a function of shifts in soil moisture highlight the far-reaching impacts of irrigation management on soil organic C (SOC) and N dynamics regulating resource availability. Decreased macroaggregate formation and greater unprotected C under SSD indicate that altered soil wetting patterns may reduce the C sequestration potential of irrigated land. Previously unknown tradeoffs should be integrated to develop irrigation strategies that maintain current and future sustainability and productivity of organic tomato agroecosystems. [ABSTRACT FROM AUTHOR]

Soil nitrogen (N) often limits productivity in agroecosystems, prompting fertilizer applications that increase crop yields but can degrade the environment. Nitrogen's dual role in both productivity and environmental quality should center it in soil health frameworks. We use recent evidence to argue that N availability is an emergent property of the integrated soil biogeochemical system and is strongly influenced by plant traits and their interactions with microbes and minerals. Building upon this, we theorize that the sources of plant and microbial N shift across soil health gradients, from inorganic N dependence in ecologically simple systems with poor soil health to a highly networked supply of organic N in healthy soils; ergo, investments in soil health should increase ecological complexity and the pathways by which plants can access N, leading to more resilient nutrient supplies and yields in a variable climate. However, current N assessment methods derive from a historical emphasis on inorganic N pool sizes and are unable to capture the shifting drivers of N availability across soil health gradients. We highlight the need to better understand the plant-microbial-mineral interactions that regulate bioavailable N as a first step to improving our ability to measure it. We conclude it will be necessary to harness agroecosystem complexity, account for plant and microbial drivers, and carefully integrate external N inputs into soils' internal N network to expand the routes by which N from organic pools can be made bioavailable. By emphasizing N in soil health concepts, we argue that researchers can accelerate advances in N use efficiency and resiliency. • Soil health goals must prioritize soil N cycling efficiency and leverage organic N. • Bioavailable N cycling is an emergent property of complex plant-soil-microbe interactions. • Soil health improves the resilience of N supply to crops but strains measurement. • Soils of intermediate health may respond most to new N cycle informed management. [ABSTRACT FROM AUTHOR]

Domestication and agricultural intensification dramatically altered maize and its cultivation environment. Changes in maize genetics (G) and environmental (E) conditions increased productivity under high-synthetic-input conditions. However, novel selective pressures on the rhizobiome may have incurred undesirable tradeoffs in organic agroecosystems, where plants obtain nutrients via microbially mediated processes including mineralization of organic matter. Using twelve maize genotypes representing an evolutionary transect (teosintes, landraces, inbred parents of modern elite germplasm, and modern hybrids) and two agricultural soils with contrasting long-term management, we integrated analyses of rhizobiome community structure, potential microbe-microbe interactions, and N-cycling functional genes to better understand the impacts of maize evolution and soil management legacy on rhizobiome recruitment. We show complex shifts in rhizobiome communities during directed evolution of maize (defined as the transition from teosinte to modern hybrids), with a larger effect of domestication (teosinte to landraces) than modern breeding (inbreds to hybrids) on rhizobiome structure and greater impacts of modern breeding on potential microbe-microbe interactions. Rhizobiome structure was significantly correlated with plant nutrient composition. Furthermore, plant biomass and nutrient content were affected by G x E interactions in which teosinte and landrace genotypes had better relative performance in the organic legacy soil than inbred and modern genotypes. The abundance of six N-cycling genes of relevance for plant nutrition and N loss pathways did not significantly differ between teosinte and modern rhizospheres in either soil management legacy. These results provide insight into the potential for improving maize adaptation to organic systems and contribute to interdisciplinary efforts toward developing resource-efficient, biologically based agroecosystems. • Shifts in rhizobiome composition were observed over maize evolutionary time. • Plant biomass and nutrients were significantly correlated to rhizobiome composition. • Teosintes/landraces grew relatively better in soil from organic management legacy. • Modern hybrids had unique co-occurrence networks but unchanged potential N cycling. [ABSTRACT FROM AUTHOR]