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Rice is often grown as multiple crops in one year, with reduced tillage upland cropping following flooded cropping gaining prominence due to water use, soil degradation and labour demands. This study explored whether a deep rather than shallow rooting rice cultivar grown in a flooded cropping cycle, benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle. In a greenhouse study, a simulated flooded paddy was planted with deep (Black Gora) and shallow (IR64) root cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland, with a photoperiod insensitive variety (BRRI Dhan 28) planted. Root length, root surface area, root volume, root diameter, number of root tips and branches were measured. The number of roots penetrating the plough pan was measured from camera images and X-ray CT. The overall root length density (RLD), root surface area, number of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared to the shallow rooting rice genotype, the deep rooting rice genotype as a ‘first season’ crop promoted 19 % greater RLD, 34 % greater surface area and 29 % more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28 % greater RLD, 35 % greater surface area and 43 % more branching for the shallow rather deep rooting genotype planted in the ‘first season’. The results suggest that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

Structural disturbance of soil such as that caused by tillage or translocation for infrastructure projects can induce changes in soil microbial functions eliciting large fluxes of CO2. Soil pH, often referred to as a master variable in the context of soil biology, exerts a strong influence on both the structure and function of microbial communities as well as the physical structure of the soil. In order to better understand the interaction of soil pH and large-scale physical disturbances in controlling these fluxes, we took the opportunity presented when moving an entire experimental field to a new location to look at how changing soil structural conditions influenced the activity of the microbial community. Soils under long-term (60 years) pH manipulation were dug from the original experimental site (Woodlands Field, SRUC, Aberdeen) and transported to a new experimental site less than 1 mile away (Aberdeen Cropping Experiment (ACE), Aberdeen), excavated soils were thoroughly mixed before reinstatement. This produced a significant decrease in bulk density and concomitant increase in macroporosity as expected (p = 0.027 and p = 0.021 respectively), with more pronounced changes at lower pH. There were consistent increases in the fraction of water-stable aggregates from the soil translocation, where the field averages of Woodlands and ACE were 91% and 95% respectively (p < 0.001). However, there were no discernible differences across the pH range (p = 0.641), despite greater changes occurring at lower pH treatments. We also observed changes in respiration rates of soils after translocation, rates were slightly increased at low pH, reduced at mid-range pH, and stable at high pH, although none of these were significant changes (p = 0.081). Soil pH was a dominant factor in controlling some aspects of the soil physical properties. Soil pH had variable magnitudes of influence, in particular, more acidic soils were more vulnerable to changes in the physical structure, where the volume of large pore spaces increased dramatically. This could explain the increased CO2 efflux in acidic soils, however, microbial communities in mid-range pH treatments demonstrated the greatest vulnerability to large-scale physical disturbance, which is likely due to the threshold pH determining their respiration pathway. This research demonstrates that soil management in large-scale disturbance should have altered management, guided by the soil pH.

Efficient water use is a must for sustainable agriculture, driving the need for affordable soil moisture sensors to guide irrigation timing. Sensors are limited by cost, maintenance and the need for wires for data capture and charging. We are developing low-cost, long-life, wireless in-situ soil sensing networks, which can potentially enable a much higher sensor density for large farmland or intense research plot monitoring. This custom soil sensor is made from off-the-shelf electronics and consumes approximately 10x less energy per measurement, compared to commercially available sensors. Here we present our new sensor technology, while also investigating its repeatability and accuracy in controlled conditions and comparing it to that of commercially available soil moisture sensors. The final application of the custom soil moisture sensor is an underground in-situ sensing network, which will be enabled through wireless powering and telemetry systems implemented on autonomous vehicles, both ground and aerial.

Root hairs represent an attractive target for future crop breeding, to improve resource use efficiency and stress tolerance. Most studies investigating root hairs have focused on plant tolerance to phosphorus deficiency and rhizosheath formation under controlled conditions. However, data on the interplay between root hairs and open-field systems, under contrasting soils and climate conditions, are limited. Although root hairs and rhizosphere are assumed to play a key role in regulating plant water relations, their effect on plant water uptake has been rarely investigated. As such, this study aimed to experimentally elucidate some of the impacts that root hairs have on plant performance under field conditions and water deficit. A field experiment was set up in Scotland for two consecutive years, in 2017 (a typical year) and 2018 (the driest growing season ever recorded at this site), under different soil textures (i.e., clay loam vs. sandy loam). Five barley (Hordeum vulgare) genotypes exhibiting variation in root hair length and density were used in the study. Measurements of root hair density, length and its correlation with rhizosheath weight highlighted trait robustness in the field under variable environmental conditions. Root hairs did not confer a notable advantage to barley under optimal conditions, but under soil water deficit root hairs enhanced plant water status and stress tolerance. This resulted in less negative leaf water potential and lower leaf abscisic acid concentration, while promoting shoot phosphorus accumulation. Specifically, minimum leaf water potential differed significantly (P = 0.021) between the wild type (-1.43 MPa) and its hairless mutant (-1.76 MPa) grown in clay loam, with the mutant exhibiting greater water stress. In agreement with leaf water potential measurements, at the peak of water stress, leaf abscisic acid concentration was significantly (P = 0.023) greater for the hairless mutant (394 ng g-1) than the wild type (250 ng g-1) grown in clay loam soil. Under water deficit conditions, in clay loam soil, shoot phosphorus accumulation in the wild type (2.49 mg P shoot-1) was over twice that in the hairless mutant (1.10 mg P shoot-1). Furthermore, the presence of root hairs did not decrease yield under optimal conditions, while root hairs enhanced yield stability under drought. While yield of the hairless mutant significantly (P = 0.012) decreased from 2017 to 2018 in both clay (-26%) and sandy (-33%) loam soils, no significant differences were found between years in the yield of the wild type. Therefore, selecting for beneficial root hair traits can enhance yield stability without diminishing yield potential, overcoming the breeder’s dilemma of trying to simultaneously enhance both productivity and resilience. To our knowledge, the present findings provide the first evidence of the effect of root hairs under drought in open field conditions (i.e., real agricultural system). Therefore, along with the well-recognized role for P uptake, maintenance or enhancement of root hairs can represent a key trait for breeding the next generation of crops for improved drought tolerance in relation to climate change.

The main aim of this global review and systematic analysis was to investigate the impacts of previous land use system, climate zone and forest type and age on soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP), in the different soil layers (0-20, 20-60 and 60-100 cm), following afforestation. We collected 85 publications on SOC, TN and TP stock changes, covering different countries and climate zones. The data were classified into groups depending on these investigated parameters and analyzed using R version 3.6.1. We found that afforestation significantly increased SOC and TN stocks in the 0-20 and 20-60 soil layers, with values of 45% and 44% for SOC, 30% and 22% for TN, respectively, but had no impact on TP stock. Previous land use systems had the largest influence on SOC, TN and TP stocks, with greater accumulations on barren land compared to cropland and grassland. Climate zone influenced SOC, TN and TP stocks, with significant accumulations in the moist than in the dry climate zone. Afforestation with broadleaf deciduous and broadleaf evergreen forests led to greater SOC, TN and TP accumulations in each soil layer throughout the investigated profile (0-100 cm), compared to coniferous forests. Afforestation for

A number of critical zone observatories across China have focussed on human impacts caused by agriculture, particularly the sustainability of soil and water resources. Using the CZO approach of measuring from the top of vegetation, through soil, to the bedrock below, joint China/UK projects at these CZOs have quantified large pools of previously undocumented nitrogen stored at depth, pathways for water loss and pollutant transport and drivers of accentuated soil erosion. Socioeconomic studies have found that these challenges to land and water resources tie in well with the concerns of farmers. In two different regions of China, farmers identified fertilisers as their greatest cost and water availability as their biggest challenge. Using large data-sets generated over the past 4 years in these projects, we are developing Decision Support Tools (DSTs) underpinned by CZO science that can guide farmers and policy makers. The work addresses food and water security in the context of climate change and diminishing resources, with an aim to improve livelihoods and sustainable economic development. We have been guided by a review of over 400 DSTs designed for agriculture and the environment, which have been ranked in terms of their outputs and data requirements. A goal at the EGU will be to develop links with other CZO projects to help with our DST development.