Causes and Consequences of Overfertilization in Orchards

Abstract

<jats:p>Over-fertilization (i.e., the application of fertilizer nitrogen (N) in excess of the tree or vine capacity to use it for optimum productivity) is associated with high levels of residual nitrate in the soil, which potentially contribute to groundwater and atmospheric pollution as a result of leaching, denitrification, etc. Overfert-ilization also may adversely affect productivity and fruit quality because of both direct (i.e., N) and indirect (i.e., shading) effects on flowering, fruit set, and fruit growth resulting from vegetative vigor. Pathological and physiological disorders as well as susceptibility to disease and insect pests also are influenced by the rate of applied N. Over-fertilization appears to be more serious in orchard crops than in many other crop species. The perennial growth habit of deciduous trees and vines is associated with an increased likelihood of fertilizer N application (and losses) during the dormant period. The large woody biomass increases the difficulty in assessing the kinetics and magnitude of annual N requirement. In mature trees, the N content of the harvested fruit appears to represent a large percentage of annual N uptake. Overfertilization is supported by a) the lack of integration of fertilizer and irrigation management, b) failure to consider nonfertilizer sources of plant-available N in the accounting of fertilizer needs, c) failure to conduct annual diagnosis of the N status, and d) the insensitivity of leaf analysis to over-fertilization. The diversity of orchard sites (with climatic, soil type, and management variables) precludes the general applicability of specific fertilization recommendations. The lack of regulatory and economic penalties encourage excessive application of fertilizer N, and it appears unlikely that the majority of growers will embrace recommended fertilizer management strategies voluntarily.</jats:p>

Seasonal changes in nutrient content and concentrations in a mature deciduous tree species: Studies in almond (Prunus dulcis (Mill.) D. A. Webb)

“…leaching of nitrogen to ground water (Weinbaum et al, 1992) with nitrate levels in ground water now exceeding the maximum contamination level of 45 ppm in many parts of the world (Nightingale, 1972;Burow et al, 1998;Esser et al, 2002;Neilsen and Neilsen, 2002;Burow et al, 2008;Mangiafico et al, 2009;Clarisse et al, 2010;Viers et al, 2012). In annual crops understanding of crop nutrient demand and the application of fertilizers at rates and times consistent with crop demand has been central to the improvement of nitrogen use efficiency and the reduction in leaching potential (Di and Cameron, 2002;Meisinger and Delgado, 2002;Li et al, 2007;Gheysari et al, 2009;Fessehazion et al, 2011).…”

The effect of autumn N supply on the architecture of young peach (Prunus persica L.) trees

“…Applied in spring and summer, N promotes shoot growth (Taylor and May 1967;Ro and Park 2000), and increases the shoot:root ratio (Poorter and Nagel 2000). Over fertilisation leads to excessive shoot growth that penalises fruit production (Weinbaum et al 1992). The increase of shoot biomass with N fertilisation results from higher sylleptic ramification and increased lengths of the axes, which have longer internodes and contain more phytomers (Lobit et al 2001;Médiène et al 2002).…”

Influence of nitrogen availability on shoot development in young peach trees [ Prunus persica (L.) Batsch]

“…It also increases the N content of all organs (Hill-Cottingham and Williams 1967;Maust and Williamson 1994) that can alter the quality of fruits such as apples (Klein et al 1989;Raese and Drake 1997). Furthermore, over fertilisation may cause groundwater pollution by nitrate leaching (Merwin et al 1996) and can decrease tree productivity due to excessive vegetative growth or increased tree sensitivity to pests (Weinbaum et al 1992;Daane et al 1995).…”