Utility of compost and wood mill waste amendments to mitigate severe replant stress of sweet cherry in the Okanagan Valley of British Columbia
Temperate fruit trees replanted into old orchard sites often grow poorly. A complex assemblage of soil-borne fungal plant pathogens and plant-parasitic nematodes is considered to be the primary cause of replant stress, but on coarse-textured soils restricted availability of water and key nutrients also contribute to poor replant establishment. Compost amendments have been reported to suppress soil-borne pathogens and improve soil-plant water relations and nutrient uptake of a wide range of crops, but their effectiveness for mitigating replant stress of perennial fruit crops is not well-known. We assessed the interactive effects of 1) fumigation, 2) the historical use of bark mulch in the preceding orchard, and 3) pre-plant incorporation of a beef feedlot-based compost at 50 Mg ha‑1, on plant-parasitic nematode populations, soil health indicators, nutrient uptake, water relations and growth of 'Lapins' sweet cherry on Krymsk 5 rootstock, through two growing seasons after replanting into an old orchard site. The historical mulch plots had been covered with shredded bark for ten years before the residual mulch was incorporated into soil prior to replanting. Fumigation had a strong main-factor effect on tree growth, illustrating the importance of soil-borne pests at this site. The compost and historical mulch treatments both increased total and labile organic soil carbon and other indicators of soil health, but only the compost treatment increased soil organic N. The compost treatment suppressed root-lesion (Pratylenchus penetrans) and stubby-root (Paratrichodorus teres) nematode populations and increased uptake of P and K, but did not improve tree growth or water relations. Similarly, the historical mulch treatment suppressed ring nematode (Mesocriconema xenoplax) populations, improved uptake of P and K, and improved tree water relations (stem water potentials, stomatal conductance, transpiration, photosynthesis), but did not improve tree growth. The lack of significant tree growth response to the compost treatment contrasts with similar experiments at other sites in the region. We speculate that the incremental suppression of plant parasitic nematodes and improvements in soil health were inadequate to overcome the particularly severe replant pest complex at this particular site. Growers should be cautious about relying completely on organic amendments to alleviate replant stress at all sites.
Forge, T.A., Neilsen, D., Neilsen, G.H., Munro, P., Watson, T.T., Jones, M. and Nelson, L.M. (2019). Utility of compost and wood mill waste amendments to mitigate severe replant stress of sweet cherry in the Okanagan Valley of British Columbia. Acta Hortic. 1266, 421-428
cherry replant, orchard soil health, plant-parasitic nematode, Pratylenchus penetrans, water relations