Baseline root coring indicates that root mass density (RMD) values are generally higher for Gijnlim as compared to Guelph Millennium for most soil depths and sample locations. However, after one-year of growth no significant differences were as yet detected. For both varieties, one year after planting circa 65% of the total measured plant root mass is found at the crown zero line, near the surface at 0.0 - 0.15 m depth (Figure 1). Very few roots have explored the soil at 0.3m, 0.6m and 0.9m away from the crown zero line. Further away from the crown zero line, roots tend to be mostly in the 0.15 – 0.30m and 0.3 - 0.45m soil layers and avoid the topsoil (0.0 - 0.15m). For both varieties, there were no roots detected (RMD values <0.1 kg m-3) in any of the root cores (0.0 – 0.45m depth) taken 0.9m away from the crown zero line. When the dimensions of the re-ridged bed-form are superimposed on the baseline varietal root distribution, the results indicate that for both Quelph Millennium and Gijnlim there is a risk of damaging 7-9% of total root biomass if the rotating tines of the bed-former used were to till soil to 0.15 -0.3m depth within 0.3m of the crown zero line. In addition, for Guelph Millennium there is a risk of damaging 2% of total plant root biomass if the rotating tines of the bed-former till soil to 0.0 - 0.15m depth within 0.3m of the crown zero line.
The year-one field trial results indicate that for both Gijnlim and Guelph Millennium varieties sub-soiling operations [for the control runoff and erosion] could be undertaken at operating depths of 0.175 – 0.3m, when crowns are planted on 1.83m centres. It is of note that the high PR (>3 MPa) measurements observed in the upper sub-soil could impact asparagus root development. The observed high BD measurements (>1.45 cm-3) in the mid top-soil and more notably in the upper sub-soil are likely to impede root growth. Historically, asparagus roots have been observed in soils with PR values of 1.96 MPa and 2.9 MPa). However, the limiting values of PR and BD for the unhindered expansion of the asparagus storage root system and hence ability to store soluble carbohydrates (COH) is unknown. This continuation of this project aims to address this knowledge gap, through the longer-term monitoring of this trial and ‘outscaling’ of root system architecture mapping to the wider UK asparagus grower land bank and cropping systems. Baseline root coring results suggest that the current coring protocol will as expected form a robust basis to quantify the effect of the BMPs investigated on asparagus root architecture and varietal differences in root profile distribution.
A pilot Cranfield MSc study (Sneska Lee) entitled “Critically evaluating varietal differences in the spatial distribution of asparagus roots” was able to map spatial patterns in asparagus storage roots. This study indicates that the highest values of root mass are found along the centre line up to 0.3m away from the ridge, and the lowest values in the wheeling in a ‘deadzone’ near the soil surface (0-0.3m). Variety [Gijnlim and Guelph Millennium] was not a prevailing factor in root mass distribution, while stand age had a significant effect. Repeated re-ridging and sub-soiling in the wheelings prevents expansion of the root system in the wheeling zone thus causing significant ‘truncation’ of the potential root biomass achievable. The has significant implications for COH storage. Root mass also negatively correlated with soil penetrative resistance across all sampled locations and fields. It is expected that the continuation of the long-term trials will form an evidence base for a paradigm shift in the way asparagus is cultivated in the UK particularly, the need for and intensity of, annual re-ridging operations and the efficacy of a suite of BMPs to remediate compaction and their selection to avoid root damage. Minimizing root damage contributes to stand longevity and productivity and decreases the susceptibility to crown and root rot.
Knowledge exchange activities
a. PAG meetings on 6th December 2016 and 17th May 2017.
b. Project update given at the Biennial AGA meeting on 18th July 2017 (150 attendees).
c. Article submitted to The Grower in September 2017
d. Niziolomski, J., Simmons, R.W., De-Baets, S. (2017) Sustainable soil management for stand longevity and yield optimization. Poster presentation, The XIV International Asparagus Symposium, Potsdam, Germany, 3-6 September 2017.
e. Lee, S., De Baets, S., Simmons, R.W., (2017). Critically evaluating varietal differences in the spatial distribution of asparagus roots. Cranfield MSc thesis poster.
f. De Baets, S., Simmons, R. 2017. Cover Crop Roots to Bio-Engineer Soil. 6th International Symposium on Soil Organic Matter, 3-7th of September 2017, Rothamsted, Harpenden, UK.
1. It is envisaged that growers will be able to select the most appropriate BMP generated under FV450 for their particular asparagus field [based on a self-evaluation of root system architecture]. This will provide a better insight into the likely return on investment of adopting BMPs derived from FV450.
2. The additional work undertaken will enable growers to minimise root damage and optimise ‘root system development’ during the crop establishment phase (1-3yrs) and hence COH storage capacity. By being able to accurately quantify their root system architecture [as well as ensuring that COH levels are within the target values established under FV271 (>550 mg COH g-1 pre harvest)] growers will be able to make a much more informed decision on whether to extend the harvest season. For a typical UK crop, this equates to >£400 of extra income for every extra day of harvest.
3. Over a 10-year cropping cycle, ‘asparagus decline’ largely attributed to Fusarium and Phytophthora infection caused by root damage can result in up to 60% loss of stand amounting to up to £16M in lost revenue per annum. A 10% reduction in yield losses due to ‘asparagus decline’ would amount to a saving of >£1.6M to UK asparagus growers per year. Therefore, optimising the development of the root system during crop establishment and maintaining this root system and hence COH storage capacity through avoiding root damage could lead to increased and yield and productive stand longevity. This in turn will improve the ability of UK growers to meet customer (supermarket) demand during the British asparagus season.