Soil resource interactions

Lead Research Organisation: Rothamsted Research
Department Name: Unlisted

Abstract

This project will provide a mechanistic understanding of how soil properties and root characteristics interact to determine water uptake, nutrient acquisition and yield and to minimize the damage caused to wheat roots by the take-all fungus. Attention will be focused on two sets of factors:
1. Improvement of management practices (M) and cultivars (G) and their interaction with the environment (E).
2. Tactical (in season and farmer driven) and strategic (longer term) crop management methods that can be used to address the yield ‘gap’ between actual and potential yield and to reduce the impact of variable seasonal conditions on yield. The combined effects of M and E which limit crop production, given adequate disease control, can be merged in the concept of “abiotic stress”. Major abiotic stresses are associated with drying soil due to high evapo-transpirational demand from the crop canopy. As soil dries water potential becomes more negative and soil strength increases, and each of these stresses can in their own right reduce crop growth. In this WP we aim to understand the effects of these interacting stresses on productivity, as outlined in the project direct objectives. Uniquely, by considering the soil-plant interface, we will take into account the G x E x M which will ensure that our findings can be translated into the field environment. Our goal will be to identify important root traits that help to mitigate against the effects of abiotic stresses on yield. Genotypic variation in root susceptibility to biotic stresses (take-all) will also contribute to root performance and will be addressed in this work package; taken together G x M x E is a central theme.

Publications

10 25 50
 
Description • Discovery of a genetic basis for the way in which root proliferate in structured soil which appears to be related to ability of roots to penetrate strong soil. The wax screen method for assessing penetration of roots was applied to diverse germplasm including a Triticum monococcum GWAS population: parents for a future mapping population were identified. The Triticum monococcum mapping population have now been screened with the wax layer system and the QTL analysis data will be available shortly. We have also measured angular spread, root number and root depth. In laboratory studies, we have shown the modification to the soil rhizosphere made by roots depends on both plant species and soil type. In the field we have made detailed measurements of rooting in relation to soil structure. These data support the prediction of our model for penetrometer resistance (see below) that at depth roots must elongate in existing pores. We have identified a genetic basis for the way in which root proliferate in structured soil in the field, by comparing different Rht NILs, which appears to be related to (1) the ability of roots to penetration strong soil and (2) the ability of roots to locate pre-existing pores. It has implications for water and nutrient uptake, as well as the most useful laboratory root screen to predict root growth in the field.
We have developed Electromagnetic Induction to the point where it has been used on AHDB RL trials, to assess water uptake by roots. The method is described by Shanahan et al. (2015). We have cooperated with NIAB in the development of PCR based root quantification methods. We are currently preparing a paper to outlining methods to phenotype wheat roots in the field.

• Models to predict the relationship between soil strength and water potential have been extended to include soil depth and tested with field data. This has allowed us to design appropriate experimental systems to investigate the effects of root impedance in the laboratory. Wheat architecture has been linked to soil strength and a genotypic basis for leaf stunting has been discovered. We investigated the effects of root impedance on both leaf elongation and tiller number (Coelho Filho et al. 2013, Jin et al. 2015). We have shown that the effect of root impedance on leaf stunting is related to GA. We have further shown the degree of leaf stunting in UK wheats is related to the Rht allele (Jin et al. 2015). We have found little evidence of a genotype dependency of tiller number reduction when roots are impeded. Global hormone profiling of wheat grown in resistant substrate was carried out to identify endogenous growth regulators involved in the response. Changes in auxin, cytokinin and jasmonate levels were observed in root tips. In rice, it was demonstrated that strigolactones are involved in the tillering response, through the use of biosynthetic/signalling mutants and quantification of strigolactones levels. The tillering response of wheat to root impedance is similar to that of rice (i.e. there are fewer tillers in when roots are impeded).

• By gaining permission to soil sample the HGCA recommended list first wheat trial sites immediately post-harvest, the low Take-all Inoculum build-up (TAB) trait has been identified as having UK wide importance.
Exploitation Route This project is not complete. However the planned objectives to date have been achieved. I the coming period we will continue to investigate root penetration of strong layers, stunting of leaves by strong soil, take-all and the effects of soil management on conditions for plant growth.
Sectors Agriculture, Food and Drink

 
Description Elongation in leaves which have been stunted due to root impedance can be restored by exogenous gibberellin (GA) applied to the roots, whereas in GA-insensitive dwarf NILs containing the Rht-b1c allele, leaf elongation is not reduced by root impendence. Thus, reduced GA signalling may be implicated in the stunting effect on leaf growth due to the root impedance. Exogenous GA and root impedance both reduced the number of tillers, while the NILs with different sensitivities to GA had a similar reduction in tiller number when roots were impeded. This implies that the effect of soil strength on tiller number is not directly related to GA signalling. While the tendency for deeper roots to be found in pores is well reported, we provide an explanation for why this is inevitable. The confinement of deeper roots to existing pore networks is almost certainly related to the increased soil penetrometer resistance that occurs with depth even in soils that have not been damaged by compaction. We have demonstrated that this effect can occur in relatively shallow soil (50 cm), but it is exacerbated by compaction. The ability of roots to penetrate hard layers is unlikely to be correlated with very deep rooting, although it is still a useful trait and likely to be associated with better exploration of surface layers and water or nutrient uptake. Penetration by roots into deeper layers is likely to depend on how well roots are able to find existing pore networks and we suggest that this question needs greater attention. The greater depth of roots that can be found in natural systems compared to cultivated soils illustrates the importance of soil structure in facilitating deep rooting. While large differences in rooting depth between different cultivars of the same species are reported, differences in soil type and management are likely to be more important factors than genotype. When comparisons of rooting depth between different genotypes have been made in the same soil, the reported differences in rooting depth have been small. Presently we do not know if the ability of roots to locate pores is simply stochastic or whether there is an underlying biological mechanism. It is also unclear how differences in root architecture and soil structure interact to determine how effectively roots locate pore networks. However, once the mechanism is understood it would aid breeding for deep rooting and improved water and N uptake.
Sector Agriculture, Food and Drink
Impact Types Societal,Economic

 
Description Funding from industry
Amount £669,000 (GBP)
Funding ID 5325 
Organisation Syngenta International AG 
Sector Public
Country Global
Start 03/2014 
End 12/2017
 
Description An optimal calibration function and process for a dielectric tensiometer sensor of the matric potential of soil water 
Organisation Delta T Devices Ltd
Country United Kingdom 
Sector Private 
PI Contribution Richard Whalley and his team have a strong track record of developing novel sensing techniques to measure soil conditions for plant growth. These sensors and sensing approaches have been developed with funding from EPSRC, BBSRC and the EU, but they have never been taken through to the point of commercialization. This has limited their wider use at Rothamsted because of the low number of prototype sensors available for research. The hurdle to commercialization is sensor calibration and this applied in particular to the dielectric tensiometer sensors of water potential (Whalley et al. SSSAJ 75:1652-1657). While the Rothamsted team does have many of the "soil physics" skills needed to develop a rapid calibration method for dielectric tensiometers, to do so in the absence of commercialization strategy, involving the use of pre-commercial sensor designs, would not effective or fruitful. For this reason we are proposing to develop a sensor calibration protocol in parallel with the development of pre-commercial prototype sensor at Delta-T Devices.
Collaborator Contribution Delta-T expects to start commercialising sensors that arise from this collaboration within 12 to 18 months of the end of this project. The successful completion of this project would provide Delta-T with its first low cost and accurate dielectric tensiometer for the measurement of matric potential of soil water. The demand for such a sensor is thought to be very high. We already have a royalty agreement, which is not related to any patent, in place with Delta-T for the technology that is at the core of the dielectric tensiometer technology that they are looking to commercialise.
Impact This collaboration is about to start. It exists because of the existing projects identified (BBS/E/C/00004861 and BBS/E/C/00005204)
Start Year 2015
 
Description I organised a scientic mneeting at Rothamsted on "Soil-Plant-Atmosphere-Continuum" jointly with Delta-T devices (Cambridge) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A scientific workshop with international invited speakers
Year(s) Of Engagement Activity 2015
URL http://www.delta-t.co.uk/Soil-Plant-Atmosphere-Continuum.asp
 
Description Show the project at the "Cereals Show" 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The outputs of the Wheat 20:20 project were presented to industry and the general public on a BBSRC/Rothamsted stand at the "Cereals" trade show.
Year(s) Of Engagement Activity 2011,2012,2013,2014,2015
URL http://www.cerealsevent.co.uk/