GROWTH RESPONSES OF YOUNG APPLE PLANTS INDUCED BY SOIL REMEDIATION TREATMENTS FOR SPECIFIC APPLE REPLANT DISEASE
Specific apple replant disease (SARD) causes reduced growth, impaired productivity and poor economic performance of new apple orchards planted on land that previously grew apples. In New Zealand and elsewhere, new intensive apple production systems will increasingly replace older orchards. A better understanding of how young apple tree growth is disrupted by SARD and the nature of growth responses to SARD remediation treatments will contribute to improving orchard performance on replant soils. In a study using plants grown in 5 L pots, the first annual growth of M.26 apple rootstocks was compared in SARD-affected soil and unplanted (new) soil of the same silt loam. Rootstock growth was measured in soils with and without pre-planting fumigation treatment (chloropicrin, 15 ml per 40 L soil volume), in combinations with and without supplementary nutrition (1.5 g Osmocote® Plus per L soil). Total dry weight of plants grown in untreated SARD soil was 22% lower than in untreated new soil. Fumigation significantly promoted growth in both SARD and new soil. After fumigation but without supplementary nutrition, growth was very similar in both SARD and new soil, with total plant dry weight of 58 g compared with 43 g for non-fumigated, unfertilised SARD soil. Although there was no significant interaction between fumigation and nutrition treatments, supplementary nutrition significantly enhanced rootstock growth in all unfumigated and fumigated soils. The greatest rootstock growth occurred in treatments combining fumigation and supplementary nutrition, achieving total plant dry weight in a range of 72-80 g. When total plant growth was partitioned into stem, new shoot and root components, the greatest proportional growth increment in response to soil treatments occurred in the dry weight of new shoots.
Tustin, D.S., I. Horner, , K. Breen, , D. Dayatilake, and E. Bigwood, (2008). GROWTH RESPONSES OF YOUNG APPLE PLANTS INDUCED BY SOIL REMEDIATION TREATMENTS FOR SPECIFIC APPLE REPLANT DISEASE. Acta Hortic. 772, 407-411
fumigation, orchard systems, nutrition, growth analysis