Soil amendments influence Pratylenchus penetrans populations, beneficial rhizosphere microorganisms, and growth of newly planted sweet cherry
Watson, T.T., Nelson, L.M., Neilsen, D., Neilsen, G.H., Forge, T.A. (2017). Soil amendments influence Pratylenchus penetrans populations, beneficial rhizosphere microorganisms, and growth of newly planted sweet cherry. Applied Soil Ecology, [online] 117-118 212-220. http://dx.doi.org/10.1016/j.apsoil.2017.04.014
Plain language summary
When new cherry and apple orchards are replanted into old orchard sites, roots of young trees are attacked by plant-parasitic nematodes, which are microscopic roundworms that feed in fine roots and inhibit growth of young trees. Historically, growers could treat soil with broad spectrum fumigants before replanting to suppress nematodes and fungal pathogens. Environmental issues associated with fumigants has prompted research to identify soil management practices that suppress nematode populations and improve early growth of replanted trees without impacting the environment. Amending soil with composts was previously observed to suppress pathogenic fungi in other crops, but such amendments had not been evaluated for replanting apple or cherry orchards where parasitic nematodes are major problems. The objective of this research was to evaluate, relative to fumigation, the effects of incorporating agricultural waste compost into soil before replanting, and applying bark chip mulch immediately after planting, on early growth of cherry trees and infection of their roots by parasitic nematodes. After two years growth, the organic amendment treatments resulted in tree growth that was nearly the same as in fumigated soil, and substantially greater than in untreated soil. Only fumigation suppressed nematode populations in the first year, but by the end of the second year nematode populations in roots of trees in fumigated soil were as large as in untreated soil, and the organic amendment treatments had the smallest nematode populations. These results indicate that compost amendments can be environmentally sustainable substitutes for fumigation in orchard replant programs.
Replant disease (RD) presents a significant barrier to establishing productive orchards on old orchard soil. Using a field and greenhouse experiment, this study evaluated the influence of agricultural waste compost (AWC) soil amendments, and bark chip mulch (BM) on Pratylenchus penetrans populations and new growth of sweet cherry planted into soil previously used for apple production. Impacts of the treatments on the abundance of rhizosphere microorganisms associated with soil suppressiveness were also evaluated. In the field experiment, fumigation, and preplant incorporation of AWC combined with surface application of BM increased trunk cross-sectional area (TCSA) compared to untreated control plots. Fumigation initially decreased P. penetrans populations in soil, however populations recovered by the end of the first growing season. AWC and BM suppressed P. penetrans populations in roots relative to fumigation or the control. AWC increased the abundance of total bacteria, 2,4-diacetylphloroglucinol-producing (DAPG) bacteria, and pyrrolnitrin-producing (PRN) bacteria in the rhizosphere, relative to fumigation and the control. In the greenhouse experiment, fumigation, AWC, and yard trimmings compost (YTC) increased shoot length of apple and sweet cherry seedlings as well as suppressed P. penetrans populations compared to the control. AWC also increased the abundance of total bacteria, Pseudomonas spp., DAPG+ bacteria, and PRN+ bacteria relative to fumigation and the control. Overall, composts and BM show potential as alternatives to fumigation for suppression of RD on sweet cherry, with promotion of beneficial rhizosphere microorganisms a possible contributing mechanism in compost-induced soil suppressiveness.