Assessing the impact of agricultural forage crops on soil biodiversity and abundance

AbstractMaintaining soil biodiversity and function is key to maintaining soil health, nutrient cycling and decomposition. Different forage species have variable concentrations of essential nutrients and rooting patterns, potentially affecting soil biology and soil–plant–animal interactions. Our study compared the effect of growing different forage crops on soil faunal diversity and abundance. Plots of chicory (Cichorium intybus), red clover (Trifolium pratense), white clover (Trifolium repens) or perennial ryegrass (Lolium perenne) were established in 2009 and maintained over a four year period. Soil faunal samples were taken, including soil mesofauna, nematodes and earthworms, at the end of this period in autumn 2012 and spring 2013. Significant differences were found between the forages for a number of biological groups, as well as some seasonal differences; overall earthworm abundance and biomass was higher within the white clover treatment, specifically anecic earthworms. Nematode functional groups were found to differ, with greater numbers of fungal feeders in the clovers and chicory treatments, whilst the herbivores had the greatest abundances in the two ryegrass treatments. Overall the microarthropod order abundances did not differ, however two collembolan superfamilies did show differences between treatments with the detritivorous Poduromorpha having a higher abundance in the clovers and chicory treatment and the herbivorous Symphypleona had a higher abundance in the ryegrass treatment. Relatively little is known about the links between soil biology and the effects of plant type because of the complex nature of soil, however here we have begun to reveal some of these linkages. Overall, the findings indicate a relationship between ryegrass and herbivorous invertebrates, whilst the other forages have a stronger relationship with decomposer invertebrates; changing the dominance within the soil food web dependent on forage type

Should farmers apply fertilizer according to when their daffodils are in flower?:Utilizing a “farmer-science” approach to understanding the impact of soil temperature on spring N fertilizer application in Wales

Perennial ryegrass starts growing when soil temperatures reach 5.5°C for five consecutive days; applying N fertiliser before this risks environmental losses. To test whether daffodil flowering signified when to apply N fertiliser, farmers volunteered to take part in a citizen‐science study. The PROSOIL project used a ‘citizen science’, participatory approach to create farmer‐informed science, aiming to increase awareness of the importance of soil health. In 2014, over 300 farmers completed a “How do you manage your soil” survey. The survey included a question on the use of daffodils (Narcissus spp) to indicate the best time to apply the first nitrogen fertiliser of the season, based on anecdotal feedback from farmers involved in the PROSOIL project. The survey recorded 7% of farmers based their first fertiliser application on when daffodils flowered. To increase farmer awareness of soil temperatures, we provided them with soil thermometers, held workshops and hosted interactive stands at agricultural events in 2014. In autumn 2014, farmers planted daffodil bulbs of the same variety, across Wales, and monitored soil temperatures. Farmers returned postcards once their daffodils were in flower, noting the soil temperature. An assessment of whether daffodil flowering date could indicate when to apply N fertiliser was made. Overall, in spring 2015, daffodils flowered when soil temperature was 6.4(±0.35)°C, suggesting daffodil flowering date is a more reliable indicator for fertiliser application, than first hypothesised. Findings show a scientific validation of local knowledge, regarding the use of daffodils to indicate the “not‐before” date for the first N fertiliser application

Understanding the legacy effect of previous forage crop and tillage management on soil biology, after conversion to an arable crop rotation

AbstractThe soil ecosystem provides a habitat for numerous and diverse fauna which hold a pivotal role driving decomposition and nutrient cycling. However, changing land use or management can alter population dynamics, changing soil biology within the system. The implementation of different field management can improve soil fertility, whilst natural variations in plant species growth and root system may create changes to soil structure and properties. All plant species create a legacy effect within the soil to some extent; changing the environment either physically or through remaining plant residues. An experiment investigated the hypothesis that previous forage cropping and tillage management would alter the diversity and abundance of soil fauna, after changing from a stable soil environment for three years to an annual arable crop rotation to complete a five-year rotation cycle. Four replicate plots (crop 1) of either perennial ryegrass (Lolium perenne), red clover (Trifolium pratense), white clover (Trifolium repens) or chicory (Cichorium intybus) were grown in a randomised block design (2009–2013) as the first crop, before conversion to an arable crop rotation. Spring wheat (Triticum aestivum) was established in 2013, either by conventional ploughing (CP) or direct drilling (DD); and winter barley (Hordeum vulgare) established using the same methodology the following autumn 2013 and harvested in 2014. Soil fauna abundance was sampled each year after the cereal crop was harvested, and included microfauna (nematodes), mesofauna (mites) and macrofauna (earthworms). Nematodes were found in greatest abundance in the previously ryegrass treatments, with greater numbers of bacterial feeders and herbivores (in 2013). Mesostigmata and oribatid mites had larger abundances in the ryegrass treatments, although Prostigmata were found in numbers five times higher after red clover in DD plots (in 2013); earthworms were found in significantly greater numbers in the previously white clover plots, across both cereal crops. These legacy effects began to diminish by the end of the second cereal crop in the rotation (in 2014). Tillage management also affected abundance, although these were fauna dependent, with earthworm numbers being detrimentally affected by ploughing whilst nematode abundances increased with ploughing. The combination of legacy and tillage elucidated interactions with the different groups of fauna, for example, epigeic earthworms, wireworms, and prostigmatid mites showed changes in abundance dependent on the combined effect of forage and tillage. Overall, legacy effects were found across three organism scales, highlighting the impact agricultural cultivations have across the whole soil food web

The legacy effect of cover crops on soil fungal populations in a cereal rotation

AbstractThe use of rotations and minimum tillage in agriculture can permit more sustainable production through increasing soil organic matter and nutrients, and breaking of pathogen lifecycles. Soil fungal populations make an important physical and chemical contribution to soil. For example, mycorrhizal species are important in plant nutrition but are often overlooked when considering management practices for efficient soil function. We undertook DNA metabarcoding (Ion Torrent) using novel PCR primers and high-throughput sequencing of the D1 region of the large ribosomal subunit of the rRNA locus, to assess the effect of different forages and cereal tillage methods on the soil fungal community. The study comprised five forage treatments, perennial ryegrass (Lolium perenne) with either low or high N, chicory (Cichorium intybus), red clover (Trifolium pratense) or white clover (Trifolium repens) grown over 3 harvest years (2010–2012). Cultivation of chicory, red clover or white clover led to significantly divergent soil fungal communities, with a notably lower diversity of fungal populations under clover, suggesting a link to soil N dynamics. Consistent with this, was a negative correlation of soil nitrate-N levels with populations of arbuscular mycorrhizal fungi (AMF) and other root-associated fungal groupings (dark septate endophytes, ‘CHEG’, Sebacinales and Ceratobasidiaceae). In contrast, abundance of Fungi belonging to the genera Mortierella and Cryptococcus were positively correlated with soil nitrate-N, with Mortierella also being negatively correlated with soil P. Spring wheat was sown on the same plots (April 2013) followed by winter barley (October 2013). Half of each plot was sown either after ploughing or by direct drilling. A legacy effect of the preceding forage crop on the fungal community was detected after both cereal crops, with plots previously cultivated with ryegrass being most divergent. No overall effect of establishment method on fungal communities was detected but AMF and CHEG fungi were more abundant on direct-drilled plots and pathogenic fungi were more abundant on ploughed plots after the sowing of winter barley

Stability, fatty acid composition and sensory properties of the <i>M. Longissimus </i>muscle from beef steers grazing either chicory / ryegrass or ryegrass

Research has shown both production and health benefits for the use of chicory (Cichorium intybus) within ruminant diets. Despite this, little was known about the the effects of this forage, containing differing fatty acid profiles and secondary plant compounds compared to ryegrass, on beef stability, fatty acid composition or sensory properties. An experiment was conducted to investigate whether the inclusion of chicory in the diet of grazing beef steers would alter the meat stability, fatty acid composition and sensory properties of the M. Longissimus muscle compared to beef steers grazing perennial ryegrass (Lolium perenne). Triplicate 2 ha plots were established with a chicory (cv. Puna II) / perennial ryegrass (cv. Premium) mix or a perennial ryegrass (cv. Premium) control. A core group of 36 Belgian Blue - cross steers were used within a two-year beef finishing experiment (n=6 per replicate plot). In the second grazing year, steers were slaughtered as they reached a target fat class of 3. After dressing, half carcass sides were hung for 48 h and then then quartered between the junction of the 10th and 11th rib. Muscle pH was checked at 2 and 48 h post-slaughter. A 250 mm-long section of the hindloin joint containing the M. Longissimus lumborum muscle was removed from the left side of the carcass, posterior to the 10th rib. A 20 mm-thick steak was cut and a muscle sample was vacuum packed and frozen at -20? C for subsequent analysis of vitamin E, a further steak being retained for fatty acid analysis. The remaining section of the loin was vacuum-packed in modified atmosphere packs and subjected to simulated retail display. The remaining section of the conditioned loin was used for sensory analysis. Data on pH, vitamin E concentration and colour stability in a simulated retail display showed there were no effects of including chicory in the diet of grazing beef steers on meat stability. There were also no differences found in the fatty acid composition or the overall eating quality of the steaks from the two treatments. In conclusion, there were no substantive effects of including chicory in the swards of grazing beef cattle on meat stability, fatty acid composition or sensory properties when compared with beef steers grazing ryegrass-only swards.publishersversionPeer reviewe

The Impact of Using Alternative Forages on the Nutrient Value within Slurry and Its Implications for Forage Productivity in Agricultural Systems

Alternative forages can be used to provide valuable home-grown feed for ruminant livestock. Utilising these different forages could affect the manure value and the implications of incorporating these forages into farming systems, needs to be better understood. An experiment tested the hypothesis that applying slurries from ruminants, fed ensiled red clover (Trifolium pratense), lucerne (Medicago sativa) or kale (Brassica oleracea) would improve the yield of hybrid ryegrass (Lolium hybridicum), compared with applying slurries from ruminants fed ensiled hybrid ryegrass, or applying inorganic N alone. Slurries from sheep offered one of four silages were applied to ryegrass plots (at 35 t ha⁻¹) with 100 kg N ha⁻¹ inorganic fertiliser; dry matter (DM) yield was compared to plots only receiving ammonium nitrate at rates of 0, 100 and 250 kg N ha⁻¹ year-1. The DM yield of plots treated with 250 kg N, lucerne or red clover slurry was significantly higher than other treatments (Pred clover (81 kg) >kale (44 kg) >ryegrass (26 kg ha⁻¹ yr⁻¹). These FNE values represent relative efficiencies of 22% (ryegrass), 52% (kale), 47% (red clover) and 60% for lucerne slurry, with the ryegrass slurry efficiency being lowest (P = 0.005). Soil magnesium levels in plots treated with legume slurry were higher than other treatments (P<0.001). Overall, slurries from ruminants fed alternative ensiled forages increased soil nutrient status, forage productivity and better N efficiency than slurries from ruminants fed ryegrass silage. The efficiency of fertiliser use is one of the major factors influencing the sustainability of farming systems, these findings highlight the cascade in benefits from feeding ruminants alternative forages, and the need to ensure their value is effectively captured to reduce environmental risks