Remobilization and uptake of N by newly planted apple (Malus domestica) trees in response to irrigation method and timing of N application

Abstract

Environmentally sound management of N in apple orchards requires that N supply meets demand. In 1997, newly planted apple trees (Malus domestica Borkh. var. Golden Delicious on M.9 rootstock) received daily applications of N for six weeks as Ca(15NO3)(2) through a drip irrigation system at a concentration of 112 mg l(-1) at 2-8, 5-11 or 8-14 weeks after planting. Irrigation water was applied either to meet estimated evaporative demand or at a fixed rate. In 1997, trees were harvested at 5, 8, 11 and 14 weeks after planting; and in 1998 at 3 weeks after full bloom. The amount of fertilizer N recovered was similar in trees in both irrigation treatments, but efficiency of fertilizer use was greater for trees receiving demand-controlled irrigation than fixed-rate irrigation. This was attributed to lower N inputs, greater retention time in the root zone and less N leaching in the demand-controlled irrigation treatments compared with fixed-rate irrigation treatments. Less fertilizer N was recovered by trees receiving an early application of N than a later application of N and this was related to the timing of N supply with respect to tree demand. Demand for root-supplied N was low until 11 weeks after planting, because early shoot and root growth was supported by N remobilized from woody tissue, which involved 55% of the total tree N content at planting. Rapid development of roots > 1 mm in diameter occurred between 11 and 14 weeks after planting, after remobilization ended, and was greater for trees receiving an early application of N than for trees receiving a later application of N. Late-season tree N demand was supplied by native soil N, and uptake and background soil solution N concentrations were higher for trees receiving demand-supplied irrigation compared with fixed-rate irrigation. Total annual N uptake by roots was unaffected by treatments and averaged 6-8 g tree(-1). Nitrogen applications in 1997 affected growth and N partitioning in 1998. Trees receiving early applications of N had more flowers, spur leaves and bourse shoots than trees receiving later applications of N. Consequently, more N was remobilized into fruits in trees receiving early applications of N compared with fruits in trees receiving later applications of N. Demand for N in the young apple trees was low. Early season demand was met by remobilization from woody tissues and the timing of demand for root-supplied N probably depends on whether flowering occurs. Method of N delivery affected the efficiency of N use. We conclude that N demand can be met at soil solution N concentrations of around 20 mg l(-1).

The Effect of Weed Competition on Apple Fruit Quality

“…The practices increasing cell number in fruit may promote firmness. During the cell division period, the most notably determining factor is the N content of trees accumulated in the previous year (Millard, 1996;Neilsen et al, 2001).…”

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

“…This suggests that the uptake of nitrogen is correlated with the rate of spring new growth. Reports on apple, peach, and mature almonds have also shown that uptake can be affected by high demands for N during the period of vigorous spring vegetative growth (Weinbaum et al, 1984b(Weinbaum et al, , 1987Munoz et al, 1993;Neilsen et al, 2001b).…”

“…For example, in apple trees, a combination of soil temperature and plant developmental stage influences the uptake and use of soil nitrogen in the spring . The timing of demand for root-supplied N may depend on whether flowering occurs (Neilsen et al, 2001b). In mature almond trees, the need for nitrogen that is triggered by the presence of fruits may also be involved in regulating its uptake (Weinbaum et al, 1984b).…”

“…Faust (1989) has reported that this practice may enhance flower-bud sizes in apple trees, while Neilsen et al (2001b) have shown that early applications of N during the first year of growth increases the amount of flowers, spur leaves, and bourse shoots in the following year. Moreover, when marginally N-deficient peach trees are supplied with N in early April, without having been treated with N fertilizer in the fall of the previous year, they exhibit vegetative growth, fruit size, and yield comparable with those trees that are supplied with soil N the previous fall (Niederholzer et al, 2001).…”

Leaf absorption, withdrawal and remobilization of autumn-applied urea-N in apple

“…Absorption of urea through dormant woody tissues was found to be considerable (Tukey and Ticknor 1952). Nitrogen reserves are responsible for supporting early season growth and flowering through remobilization (Millard 1996;Millard and Neilsen 1989;Neilsen et al 2001). Recently, labelled urea 15 N has been used to quantify leaf absorption more precisely and to measure directly the increase in N reserves attributable to urea sprays (Rosecrance et al 1998;Tagliavini et al 1998;Sanchez et al 1990).…”