The effects of arbuscular mycorrhizal fungal colonisation on nutrient status, growth, productivity, and canker resistance of apple (Malus pumila)

We assess whether arbuscular mycorrhizal fungi (AMF) improve growth, nutritional status, phenology, flower and fruit production, and disease resistance in woody perennial crops using apple (Malus pumila) as a study system. In a fully factorial experiment, young trees were grown for 3 years with or without AMF (Funneliformis mosseae and Rhizophagus irregularis), and with industrial standard fertiliser applications or restricted fertiliser (10% of standard). We use two commercial scions (Dabinett and Michelin) and rootstocks (MM111 and MM106). Industrial standard fertiliser applications reduced AMF colonisation and root biomass, potentially increasing drought sensitivity. Mycorrhizal status was influenced by above ground genotypes (scion type) but not rootstocks, indicating strong interactions between above and below ground plant tissue. The AMF inoculation significantly increased resistance to Neonectria ditissima, a globally economically significant fungal pathogen of apple orchards, but did not consistently alter leaf nutrients, growth, phenology or fruit and flower production. This study significantly advances understanding of AMF benefits to woody perennial crops, especially increased disease resistance which we show is not due to improved tree nutrition or drought alleviation. Breeding programmes and standard management practises can limit the potential for these benefits

Experimental evaluation of biological regeneration of arable soil : the effects of grass-clover leys and arbuscular mycorrhizal inoculants on wheat growth, yield, and shoot pathology

Wheat yields have plateaued in the UK over the last 25 years, during which time most arable land has been annually cropped continuously with short rotations dominated by cereals. Arable intensification has depleted soil organic matter and biology, including mycorrhizas, which are affected by tillage, herbicides, and crop genotype. Here, we test whether winter wheat yields, mycorrhization, and shoot health can be improved simply by adopting less intensive tillage and adding commercial mycorrhizal inoculum to long-term arable fields, or if 3-year grass-clover leys followed direct drilling is more effective for biological regeneration of soil with reduced N fertiliser. We report a trial of mycorrhization, ear pathology, and yield performance of the parents and four double haploid lines from the Avalon x Cadenza winter wheat population in a long-term arable field that is divided into replicated treatment plots. These plots comprised wheat lines grown using ploughing or disc cultivation for 3 years, half of which received annual additions of commercial arbuscular mycorrhizal (AM) inoculum, compared to 3-year mown grass-clover ley plots treated with glyphosate and direct-drilled. All plots annually received 35 kg of N ha−1 fertiliser without fungicides. The wheat lines did not differ in mycorrhization, which averaged only 34% and 40% of root length colonised (RLC) in the ploughed and disc-cultivated plots, respectively, and decreased with inoculation. In the ley, RLC increased to 52%. Two wheat lines were very susceptible to a sooty ear mould, which was lowest in the ley, and highest with disc cultivation. AM inoculation reduced ear infections by >50% in the susceptible lines. In the ley, yields ranged from 7.2 to 8.3 t ha−1, achieving 92 to 106% of UK average wheat yield in 2018 (7.8 t ha−1) but using only 25% of average N fertiliser. Yields with ploughing and disc cultivation averaged only 3.9 and 3.4 t ha−1, respectively, with AM inoculum reducing yields from 4.3 to 3.5 t ha−1 in ploughed plots, with no effect of disc cultivation. The findings reveal multiple benefits of reintegrating legume-rich leys into arable rotations as part of a strategy to regenerate soil quality and wheat crop health, reduce dependence on nitrogen fertilisers, enhance mycorrhization, and achieve good yields

The role of hedgerows in soil functioning within agricultural landscapes

Intensification of agriculture has led to major losses of hedgerows and field margins worldwide. Soil sample extraction, in situ time series of soil moisture, temperature and soil water quality analyses, annual earthworm sampling and arbuscular mycorrhizal (AM) fungi sampling enabled comparison of soil functions between typical hedgerows, grass field margins, pasture and arable (mainly winter wheat) fields in a temperate, lowland setting. Mean bulk density (upper 50 cm), surface compaction and soil moisture content were significantly lower while organic matter content and porewater dissolved organic carbon concentrations were significantly greater in hedgerow soils, than margins or fields. Mean nitrate and phosphate concentrations were three and ten times larger, respectively, in soil solutions under hedgerows than arable fields while ammonium concentrations were least in arable fields. Saturated hydraulic conductivity was significantly greater under hedgerows (median = 102 mm hr−1) where it took an average of one hour longer for soils to reach maximum moisture content following rainfall, than adjacent arable (median = 3 mm hr−1) or pasture fields and margins (median = 27 mm hr−1). Hedgerow soils had a greater proportion of flow through micropores and less macropore flow than other soils. The pasture and margin soils had the largest proportion of macropore flow (>85%) and more (and larger) anecic earthworm species, such as Lumbricus terrestris which produce vertical burrows. Earthworm density, biomass and diversity were greater in pasture and margin soils, followed by hedgerow soils, and tended to be lowest in arable soils. For both total and AM fungi, hedgerow soils hosted a distinct and heterogeneous soil community, margin and pasture communities were diverse but clustered together, and arable communities formed a distinct cluster, with low inter-sample variation and significantly lowest AM fungal richness. The findings demonstrate that soils under hedgerows, which should be conserved, can provide important functions on farmland including storing organic carbon, promoting infiltration and storing runoff, increasing earthworm diversity and hosting distinct AM communities