Do agricultural grasses bred for improved root systems provide resilience to machinery-derived soil compaction?

Nuwan P.K Muhandiram,Christina L Marley,John W Davies,Ruth Sanderson,Mike W Humphreys,Rhun Fychan

doi:10.1002/fes3.227

Nuwan P.K Muhandiram, Christina L Marley + Show 4 more

Open Access

https://doi.org/10.1002/fes3.227

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Abstract

The increasing frequency of droughts and floods on grasslands, due to climate change, increases the risk of soil compaction. Soil compaction affects both soil and forage productivity. Differing grasses may counteract some effects of compaction due to differences in their root architecture and ontogeny. To compare their resilience to soil compaction, three Festulolium (ryegrass and fescue species’ hybrids) forage grass cultivars comprising differing root architecture and ontogeny were compared in replicated field plots, together with a ryegrass and tall fescue variety as controls. Pre‐compaction soil and forage properties were determined in spring using > four‐year‐old plots to generate baseline data. Half of each field plot was then artificially compacted using farm machinery. Forage dry matter yield (DMY) was determined over four cuts. After the final harvest, post compaction soil characteristics and root biomass (RB) were compared between grasses in the non‐compacted and compacted soils. Pre‐compaction data showed that soil under Festulolium and ryegrass had similar water infiltration rates, higher than soil under tall fescue plots. Tiller density of the Festulolium at this time was significantly higher than fescue but not the ryegrass control. Forage DMY was significantly lower (p < .001) with compacted soil at the first cut but, by the completion of the growing season, there was no effect of soil compaction on total DMY. Tall fescue had a higher total DMY than other grasses, which all produced similar annual yields. Soil bulk density and penetration resistance were higher, and grass tiller density was lower in compacted soils. Root biomass in compacted soils showed a tendency for Festulolium cv Lp × Fg to have higher RB than the ryegrass at 0–15 cm depth. Overall, findings showed alternative grass root structures provide differing resilience to machinery compaction, and root biomass production can be encouraged without negative impacts on forage productivity.

Highlights

Prior to soil compaction and the full commencement of the growing season, the perennial ryegrass plots showed significantly lower total penetration resistance (PR) compared to the Festulolium cultivars Lp × Fm and Lp × Fg
Given the importance of the rates of soil drying on soil strength (Rondinelli et al, 2015), as differences in water uptake by roots was not measured during the current study, further studies are needed to include these parameters and for the findings presented here to be evaluated across a range of different soil types to fully understand the plant genotype responses to differing soil strength
The impacts of soil compaction on forage may be due to a reduced plant nutrient uptake and reduced root biomass at depth, the latter being a known attribute in certain Festulolium genotypes with improved drought resistance (Durand et al, 2007; Humphreys et al, 2018) and so these below-ground responses were a key focus of the current study

Summary

Introduction

There were no further effects of compaction on DMY (p > .05) and total DMY for all grass types accumulated over all four harvests was not significantly different between soil condition treatments (p > .05). Prior to soil compaction and the full commencement of the growing season, the perennial ryegrass plots showed significantly lower total PR compared to the Festulolium cultivars Lp × Fm and Lp × Fg. at the second PR measurement in the autumn of the same year, this effect had diminished, with the penetration resistance of the ryegrass treatments being equivalent to that under the other grasses.

Results

Conclusion