Sources of N for leaf growth in a high-density apple (Malus domestica) orchard irrigated with ammonium nitrate solution

Abstract

Elstar apple trees (Malus domestica Borkh.) on M.9 rootstock received either 5 or 35 g N tree(-1) year(-1) during the first two growing seasons after planting, applied as Ca(NO(3))(2) on a daily basis for nine weeks through a drip irrigation system. During the third growing season (1994), all trees were treated with 20 g N tree(-1) year(-1) as (15)NH(4) (15)NO(3) with applications starting on April 22 and continuing for 10 weeks. Soil solution nitrate-N and ammonium-N were monitored weekly with suction lysimeters located 30 cm beneath the drip emitters. Spur and shoot leaves were sampled intensively from full bloom to the end of rapid shoot growth. During the period of nitrogen application, soil solution nitrate-N and ammonium-N were relatively constant, at about 24 and 1.0 mg l(-1) respectively. Growth of the spur leaves was completed by one week after full bloom (May 12), whereas biomass of the shoot leaves increased until mid-June. Nitrogen for growth of the spur leaves was supplied mainly from remobilization, which was dependent on previous N supply. Accumulation of fertilizer N in spur leaves was independent of previous N treatments and continued until the end of the monitoring period (June 24), but contributed only 13% to total spur leaf N. Nitrogen for shoot leaf growth was independent of previous N treatments and was initially supplied primarily by remobilization, but by the end of extension growth, fertilizer N contributed 48% to total shoot leaf N. Linear increases in leaf N uptake throughout the period of rapid shoot growth and the large contribution of fertilizer N to total shoot leaf N were attributed to the constant supply of N available in the root zone through daily N fertilization.

Effects of spring soil nitrogen application on nitrogen remobilization, uptake, and partitioning for new growth in almond nursery plants

“…Moreover, the amount that was remobilized depended mainly on the amount that had been stored, and was unaffected by the current N supply. This result is similar to the pattern of spring N remobilization reported for other tree fruit species (Millard and Neilsen, 1989;Millard, 1996;Neilsen et al, 1997). Numerous studies have described the remobilization of nitrogen in deciduous tree fruits.…”

“…Approximately 50-55% of the nitrogen in dormant young apple trees is used to support new growth (Neilsen et al, 2001b;Cheng and Fuchigami, 2002). The remobilization of N in young, fruiting apple trees ends by 5 d after full bloom (Neilsen et al, 1997). In peach trees, all N used for new growth during the first 25 to 30 d of the growing season came from storage; remobilization continues until about 75 d post-anthesis (Rufat and DeJong, 2001).…”

Contribution of previous year's leaf N and soil N uptake to current year's leaf growth in sessile oak

“…Similar findings have been reported for other species. For example, 20-30 % of shoot-leaf N was supplied by spring-applied fertilizer for mature pear trees (Sanchez et al, 1990) and mature almond trees (Weinbaum, 1984), while only 13 % of a solution of nitrate-N and ammonium-N that was applied to soil contributed to total leaf N of apple trees (Neilsen et al, 1997). Sorbus aucuparia had remobilized half the N from storage before any was taken up by the roots .…”

Benchmarking nitrous oxide emissions in deciduous tree cropping systems

“…This stored N is remobilised for the current season's growth, which for some crops can contribute up to 50% of the total N requirement for the season (Millard and Neilsen 1989). Deciduous fruit tree crops are strong sinks for N, in which a large portion of N (30-60 kg ha -1 ) is removed on an annual basis depending on crop load (Neilsen et al 1997). As developing fruit have a strong demand for N over a short growth stage, growers tend to apply high rates of fertiliser to the soil over a short period preharvest to meet tree demands and/or post-harvest to facilitate storage of N by trees during winter dormancy.…”