Agricultural Soil Science in a Changing Climate: Soil Health, Carbon Cycling, Nutrient Dynamics and Agroecosystem Resilience

Next-Generation Genome Editing for Climate-Smart Agriculture: A Critical Appraisal of the Transition from CRISPR-Cas Nucleases to Large-Scale Genome Engineering

2026-09-22T12:24:41+00:00

Genome editing has moved from a proof-of-concept technology to a central instrument in proposals for adapting agriculture to a warming and more variable climate. The claim that editing can deliver climate-smart crops rests on a chain of assumptions that has rarely been examined as a whole: that climate-relevant traits are tractable at the level of a small number of edited loci, that editing reagents can be delivered into agronomically relevant germplasm, that laboratory phenotypes translate into field performance, and that regulatory and institutional systems will allow the resulting varieties to reach the farmers most exposed to climate risk. This review evaluates that chain critically. It traces the technical trajectory from double-strand-break nucleases through base and prime editing to multi-kilobase insertion and chromosome-scale engineering, and asks what each capability adds to climate adaptation rather than to precision as an end in itself. The evidence is strongest for single-gene and cis-regulatory modifications affecting disease resistance, tillering and grain traits, where independent field data exist. It is considerably weaker for abiotic stress tolerance, where most reports rest on controlled-environment phenotyping of single genotypes, and weakest for mitigation traits, where genetic interventions have rarely been evaluated under realistic management. Delivery and regeneration, not nuclease design, remain the binding constraint for most crops that matter for adaptation in low-income regions. Chromosome-scale engineering has been demonstrated convincingly in model species and offers a route to manipulating recombination and linkage, yet no crop application has been reported at agronomic scale. Regulatory divergence and unequal institutional capacity now shape the distribution of benefits at least as strongly as technical capability. Priorities that follow include multi-environment field evaluation with transparent reporting of null and negative results, systematic quantification of trade-offs, transfer of chromosome engineering to crop species, and investment in delivery platforms for vegetatively propagated and orphan crops.

Microbiome-Mediated Crop Resilience to Drought, Salinity and Nutrient Stress: Mechanisms, Engineering Strategies and the Challenge of Field Translation

2026-09-22T12:28:58+00:00

Crop-associated microbiomes are increasingly proposed as tools for stabilising productivity under drought, salinity and nutrient limitation, yet the evidence spans scales from stress-responsive community surveys to single-strain inoculation and field deployment. This critical narrative review integrates literature published from 1 January 2000 to 3 July 2026 to evaluate mechanisms, engineering strategies and translational constraints. Across drought studies, root microbiomes show recurrent stress-driven reassembly, including conserved enrichment patterns in several grasses and crops, but taxonomic shifts alone do not establish adaptive function. Bacterial inoculation, arbuscular mycorrhizal symbiosis and community-selection experiments support causal routes involving root architecture, hormone balance, osmotic adjustment, antioxidant capacity and nutrient acquisition. Salinity mitigation uses overlapping mechanisms but adds ion-homeostasis and microbial halotolerance requirements; the evidence remains weighted towards controlled environments. Nutrient stress provides some of the clearest causal examples of host-directed microbiome recruitment, including genotype-dependent nitrogen-associated communities, flavone-mediated bacterial enrichment, phosphate-starvation–microbiota integration and coumarin-dependent iron acquisition. Synthetic communities, host-mediated microbiome selection and microbiome-aware breeding can convert these mechanisms into interventions, but field performance is constrained by native-community competition, soil heterogeneity, stress definition, genotype × environment × microbiome × management interactions and uncertain persistence. The synthesis supports a context-dependent functional-resilience framework in which function is prioritised over taxonomic identity, persistence is defined by the duration required for activity, and success is judged by yield stability or resource-use efficiency rather than short-term biomass alone. Progress requires causal perturbation, non-sterile validation, multi-site and multi-season testing, realistic combined stresses and explicit ecological safety assessment. The most credible translational pathway is therefore a staged evidence chain linking microbial establishment, in situ functional expression, plant physiological response and agronomic benefit within defined agroecological recommendation domains.

Engineering Abiotic Stress Tolerance in Crops with CRISPR-Cas: A Critical Appraisal of Mechanisms, Evidence and Translational Constraints in a Warming Climate

2026-09-22T12:36:11+00:00

Rising mean temperatures, more frequent extremes and the progressive salinisation of agricultural land are eroding the productivity gains on which global food supply depends. Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) technologies are widely presented as a means of building abiotic stress tolerance directly into elite germplasm, yet the literature has expanded far faster than the evidence base that would justify confidence in field-scale benefit. This review critically evaluates that literature. It examines how the editing toolbox has moved from simple gene disruption towards allelic series, regulatory-region modification and transcriptional or epigenetic modulation, and asks what each modality can realistically deliver for quantitative stress traits. Evidence is then appraised by stress domain, covering water deficit, salinity and ionic imbalance, high and low temperature, oxygen deficiency and soil chemical constraints. Recurring problems are identified rather than catalogued: a heavy dependence on glasshouse or pot-based phenotyping under severe, abrupt stress; asymmetric reporting in which yield under non-stressed conditions is frequently omitted; near-exclusive reliance on a small number of model cultivars; and limited attention to combined or sequential stresses. Stomatal density engineering is treated as an instructive case in which mechanistically attractive interventions have produced inconsistent and sometimes opposing outcomes across species and growth environments. The strongest evidence supports interventions that tune expression of a native locus in a stress-responsive manner rather than eliminating gene function outright, and that have been evaluated under field conditions with an explicit accounting of yield potential. Persistent constraints include genotype-dependent regeneration, incomplete transferability of targets between species, divergent regulatory treatment across jurisdictions, and an evidence base geographically concentrated in a few research systems. Priorities are proposed for multi-environment field evaluation, standardised stress reporting, and the extension of editing capability to crops and regions currently underserved.

Subsurface Controlled Drainage and Subirrigation Systems: A Critical Synthesis of Hydrodynamic Modelling, Water-Table Management and Nutrient-Loss Mitigation

2026-09-22T12:41:22+00:00

Subsurface drainage is indispensable to crop production on many poorly drained soils, yet rapid removal of water can accelerate nutrient export and reduce the soil-water reserve available during subsequent dry periods. Controlled drainage (CD) and controlled drainage with subirrigation (CDSI) seek to convert a fixed drainage network into an actively managed water-table system. This critical narrative review integrates hydrodynamic modelling, field water-table management, agronomic response, and nitrogen and phosphorus mitigation. Literature was selected from agricultural, environmental and multidisciplinary scholarly sources, with emphasis on peer-reviewed field experiments, long-term syntheses, meta-analyses and process-based modelling studies. The evidence is strongest for a hydrologic mechanism: raising the effective outlet elevation commonly reduces subsurface drainage discharge and therefore nitrate load delivered through drain outlets. Concentration responses are less consistent, and field-scale outlet reductions cannot automatically be interpreted as whole-system nutrient removal because retained water may be redistributed to evapotranspiration, surface runoff, deep percolation or lateral seepage. Phosphorus responses are more equivocal than nitrate responses because dissolved and particulate pathways can shift in opposite directions as the water table is raised. Yield effects are similarly conditional; benefits are most plausible when stored or supplied water relieves seasonal water deficit, whereas excessive or poorly timed water-table elevation can increase waterlogging risk. DRAINMOD and its nutrient and crop extensions provide the most established field-scale framework, while HYDRUS-2D, RZWQM2, SWAT/SWAT+ and SWAP address complementary process or scaling questions. Model credibility depends on independent validation of water-table depth, flow, nutrient loads and crop outcomes, not calibration to outlet flow alone. The synthesis supports adaptive, site-specific operation rather than static high-water tables, and identifies catchment-scale water accounting, phosphorus pathway representation, automated control under forecast uncertainty, salinity constraints, and multi-objective field validation as priorities for future research.

Unlocking Crop Genetic Diversity for Climate Adaptation: A Critical Appraisal of Genebanks, Crop Wild Relatives, Pangenomes and Precision Breeding

2026-09-22T12:45:38+00:00

Crop genetic diversity is widely presented as the raw material for adapting agriculture to a warming and more variable climate, yet the pathway from conserved diversity to adapted cultivars remains poorly characterised and unevenly evidenced. This critical narrative review examines four components of that pathway, namely ex situ and in situ conservation of plant genetic resources, the mobilisation of crop wild relatives and landraces, the construction and use of pangenomes, and the application of precision breeding technologies. Literature was identified through open scholarly databases and indexes, supplemented by citation searching and by examination of authoritative institutional documents, with verification of bibliographic identity and of the correspondence between each source and the claim it supports. The synthesis indicates that the evidence base is strongly asymmetric. Conservation gap analyses, genebank genotyping and pangenome assembly are methodologically mature and internally consistent, whereas evidence that these resources have produced climate-adapted cultivars at scale is sparse, concentrated in qualitative disease resistance traits, and rarely accompanied by multi-environment yield data. Structural variation captured by graph pangenomes recovers heritability that single-reference analyses miss, but the demonstrated breeding applications remain concentrated in a small number of well-resourced crops. Genome editing has delivered convincing qualitative phenotypes and a smaller number of field-validated quantitative gains, while paralogue redundancy and background dependence limit the transfer of edited alleles between species. The central unresolved problem is not the discovery of adaptive variation but its conversion into varieties that farmers grow, which depends on prebreeding capacity, multi-environment phenotyping, seed systems and varietal turnover rather than on sequencing throughput. Governance of digital sequence information and divergent national regulation of precision-bred plants add further uncertainty. Priorities include environment-resolved phenotyping of genebank material, validation of genomic vulnerability predictions against measured fitness, and reporting standards that make pangenome-based claims comparable across crops.

Digital Innovations in Carbon Farming: A Critical Review of Soil Carbon Sequestration, Permanence and Monitoring, Reporting and Verification Systems

2026-09-24T09:28:04+00:00

Carbon farming has moved from an agronomic aspiration to a regulated and traded climate instrument, and the credibility of that transition rests on whether soil organic carbon change can be quantified accurately, attributed correctly and defended over time. Digital technologies, including proximal and laboratory spectroscopy, satellite earth observation, in-field sensor networks, process-based biogeochemical models, statistical learning and distributed registry infrastructure, are being assembled into digital monitoring, reporting and verification systems that promise to reduce cost while preserving rigour. This review critically evaluates the scientific basis of that promise across three connected domains: the biogeochemical limits of soil carbon accrual, the meaning and management of permanence, and the design and performance of digital quantification systems. Literature was identified through structured searching of open scholarly databases and indexes, supplemented by backward and forward citation searching and by targeted retrieval of institutional and policy analyses, with critical appraisal focused on measurement validity, uncertainty treatment, external validity and the alignment between evidence and claim. The synthesis indicates that the strongest evidence supports three positions: that measurable and durable gains in soil organic carbon are achievable but bounded by mineralogical capacity and by the diminishing returns of stock recovery; that reversibility is an intrinsic property of the resource rather than a project management failure, so accounting must treat impermanence explicitly; and that no single digital modality currently satisfies the joint requirements of accuracy, spatial coverage and affordability. Evidence is weakest, and disagreement most pronounced, in three areas: the transfer of spectroscopic and remote sensing calibrations to new soils and conditions, the independent temporal validation of the models used to interpolate between sampling events, and the empirical performance of digital systems in smallholder and dryland settings. Digital innovation improves the resolution and cost profile of quantification, but it does not by itself resolve questions of additionality, baseline construction or durability, which remain governance problems informed by, rather than solved by, measurement.

Farming under Heat, Drought and Water Scarcity: An Integrated Critical Review of Water-Smart Crop Production in a Warming Climate

2026-09-25T09:12:35+00:00

Climate warming is intensifying the concurrence of heat stress, drought and water scarcity, but proposed responses are often evaluated at incompatible biological and hydrological scales. This critical narrative review integrates crop physiology, breeding, soil management, rainwater capture, irrigation engineering, digital decision support, cropping-system design and water governance. Literature published primarily from 2000 to 4 July 2026 was selected through transparent relevance and quality criteria, with foundational sources retained where necessary. The evidence indicates that no single technology reliably creates water-smart production. Heat and drought interact through stomatal regulation, canopy temperature, phenology and reproductive sensitivity; consequently, trait and management performance is scenario dependent. Soil cover, infiltration improvement, context-matched cultivars, timely establishment, supplemental irrigation and well-scheduled deficit irrigation can raise yield stability, although benefits vary with soil, stress timing and implementation quality. Pressurised irrigation improves control but does not necessarily conserve water at basin scale because return flows, crop expansion and rebound pumping alter net depletion. Digital tools are valuable when calibrated, actionable and evaluated against current practice, yet their effect is constrained by data quality, connectivity and unequal capacity to respond. The strongest strategy is a diagnosed portfolio that combines genetic, agronomic and engineering measures with salinity management, energy safeguards and enforceable limits on consumptive use. Evaluation should jointly consider yield stability, farm income, water depletion, soil condition, energy, equity and environmental flows. Research priorities include realistic compound-stress trials, farm-to-basin water accounting, prospective decision-support evaluations and governance experiments that distinguish plot efficiency from genuine water savings.