Impact of Diversified Crop Rotations on Soil Fungal Communities.

Diversifying crop rotations with pulse crops has been reported to decrease the input cost of crop production through improved soil water and nutrient conditions. However, little is known about the rotational effect on soil microbial communities. A 4-yr crop rotation experiment was carried out at Indian Head, Saskatchewan (50°32'N, 103°40'W) to evaluate six rotation systems where pea (P, Pisum sativum L.), lentil (L, Lens culinaris Medik.), and hybrid canola (C, Brassica napus L.) were seeded in different intensities and rotated with wheat (W, Triticum aestivum L.) and oats (O, Avena sativa L.). The results revealed that the rotation sequences had a significant effect (P<0.01) on soil fungal community composition and diversity at pea flowering stage in 2015 and 2016. Rotation sequences also influenced soil properties, such as Fe, Mn, available phosphorus (AP) and pH value significantly (P<0.05). Non-metric multidimensional scaling analysis showed that the soil fungal community in the rotation with three pulse crops (WPLP) was distinct from those in the rotations including two pulse or canola crops (WCPC, WPCP and WPOP). Rotation of WPLP had a significantly higher proportion of pathotrophs (primarily due to higher levels of Olpidium in 2015 and Alternaria in 2016) in the soil fungal community compared to rotations with canola crop (WCPC and WPCP) in both years; whereas the WPLP rotation had the lowest proportion of symbiotrophs among the rotation systems evaluated. It appeared that rotation sequences have promoted the diversification of soil fungal communities after four years of cropping. Strong effect of rotation sequences on soil fungal community composition suggest that the way crops are rotated will drive the shift of soil fungal community, which may alter crop root growing environment and thus influencing crop productivity.