title: Changes in fine-root production, phenology and spatial distribution in response to N application in irrigated sweet cherry trees.
abstract: Factors regulating fine-root growth are poorly understood, particularly in fruit tree species. In this context, the effects of N addition on the temporal and spatial distribution of fine-root growth and on the fine-root turnover were assessed in irrigated sweet cherry trees. The influence of other exogenous and endogenous factors was also examined. The rhizotron technique was used to measure the length-based fine-root growth in trees fertilized at two N rates (0 and 60 kg ha(-1)), and the above-ground growth, leaf net assimilation, and air and soil variables were simultaneously monitored. N fertilization exerted a basal effect throughout the season, changing the magnitude, temporal patterns and spatial distribution of fine-root production and mortality. Specifically, N addition enhanced the total fine-root production by increasing rates and extending the production period. On average, N-fertilized trees had a length-based production that was 110-180% higher than in control trees, depending on growing season. Mortality was proportional to production, but turnover rates were inconsistently affected. Root production and mortality was homogeneously distributed in the soil profile of N-fertilized trees while control trees had 70-80% of the total fine-root production and mortality concentrated below 50 cm depth. Root mortality rates were associated with soil temperature and water content. In contrast, root production rates were primarily under endogenous control, specifically through source-sink relationships, which in turn were affected by N supply through changes in leaf photosynthetic level. Therefore, exogenous and endogenous factors interacted to control the fine-root dynamics of irrigated sweet cherry trees.
authors.affiliation: Ph.D. Program in Agricultural Sciences, Agronomy and Forestry Faculty, Pontifical Catholic University of Chile, Vicuña Mackenna 4860, 7820436-Macul, Región Metropolitana, Chile; pnartach@uc.cl.
authors.forename: Pamela
authors.initials: P
authors.lastname: Artacho
authors.affiliation: Pomology and Enology Department, Pontifical Catholic University of Chile, Vicuña Mackenna 4860, 7820436-Macul, Región Metropolitana, Chile.
authors.forename: Claudia
authors.initials: C
authors.lastname: Bonomelli
mesh_terms: D057914:Agricultural Irrigation; D002677:Chile; D004305:Dose-Response Relationship, Drug; D005308:Fertilizers / Q000032:analysis; D009584:Nitrogen / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D000068220:Prunus avium / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D012621:Seasons; D014197:Trees / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D005308:Fertilizers; D009584:Nitrogen
keywords: N fertilization; central Chile; fine-root dynamics; spatial distribution; sweet cherry trees