Fate of 15N-labelled nitrogen fertilizer applied to kiwifruit (Actinidia deliciosa) vines

Abstract

The fate of 15N-labelled ammonium fertilizer applied once to six-year-old field-grown kiwifruit (Actinidia deliciosa 'Hayward') vines was measured over three years. The three main treatments were nitrogen (N) applied singularly at 100 or 200 kg N ha -~ in early spring (two weeks before bud burst) or split with 100 kg N ha -I (unlabelled) in early spring and 100 kg N ha -1 (lSN-labelled) ten weeks later. All N treatments were applied to vines with a history of either 50 or 200 kg N ha -~ yr -1. For three years after ~SN application, components of the vines and soil (0-600 mm depth) were sampled at harvest in late autumn and the N and 15N contents determined.By the first harvest, all plant uptake of ~SN had occurred and this represented 48-53% of the 15N applied. There was no significant effect of current N fertilizer treatment or of N history on ~SN recovery by vines. Removal of 15N in harvested fruit was small at 5-6% in the first year and 8% over 3 years. After 2-3 years, most plant 15N occurred in the roots and this component declined only slowly over time. In contrast, there was a large temporal decline in ~SN in above-ground plant components due to the annual 'removal' in leaf fall and pruning. An associated experiment showed that when 15N-labelled prunings and leaves were mulched and returned to the soil, only about 9% was recovered by plants within 2 years. Almost all remaining mulched material had been immobilised into the soil organic N.In all treatments, about 20% of the added ~SN remained in soil at the first harvest. This was almost entirely in organic fractions (<0.4% in inorganic N) and mostly in the surface 150-mm layer. The 15N content in soil changed little over time (from 20 to 17% between the first and third harvests respectively) and indicated that most of the N had been immobilised into stable humus forms.

Coupling Sap Flow Velocity and Amino Acid Concentrations as an Alternative Method to 15N Labeling for Quantifying Nitrogen Remobilization by Walnut Trees

“…This result is consistent with the values of 60% estimated for larger walnut trees grown in the orchard by Weinbaum and Van Kessel (1998), although higher values of 75% have also been reported for field-growing walnut trees by Deng et al (1989). Similar percentages of N derived from remobilization for new growth were found in young pear (Pyrus communis) trees (Taglivani et al, 1997), in kiwifruit (Actinidia deliciosa) in orchard conditions (Ledgard and Smith, 1992), and in B. pendula, 40% (Millard et al, 1998). Higher fractions were reported for citrus trees growing in sand culture (Legaz et al, 1995), apple (Malus domestica) trees (Neilsen et al, 1997), and peach (Prunus persica) trees (Munoz et al, 1993).…”

Root uptake, storage and remobilisation of autumn applied nitrogen to kiwifruit (Actinidia deliciosa) vines

“…These values likely represent an underestimate of the whole N remobilisation from storage as they do not take into account the remobilisation of unlabelled N absorbed before autumn 1997. However, the data agree with evidence provided by Ledgard and Brier [7] and by Ledgard and Smith [8], who analysed xylem sap from kiwifruit plants supplied with labelled N in early spring and estimated that the remobilised N may account for 60% of total N in new growth 4 weeks from bud burst, declining to 30% four weeks later. It appears, therefore, that the internal cycling of N represents a major source of N for shoot development of kiwifruit plants in spring.…”

“…Nitrogen needs are thought to be continuous throughout the long vegetative season [2,17], but assessments of nitrogen uptake by kiwifruit using 15 N techniques have been made for spring and summer periods only [8,9]. The present study indicates that the root system of kiwifruit is highly efficient in taking up the nitrogen applied in early autumn, representing 68% of the N supplied to LN plants, and 44% to HN ones.…”

“…deliciosa) is a perennial fruiting crop with a large seasonal N demand, with two major peaks coinciding with bud swelling and the early stages of fruit growth, 2-3 weeks after fruit set [3,17]. In a field experiment where 15 N was applied to kiwifruit vines in spring or early summer, the labelled N uptake was almost complete within 10 weeks from application and partitioned mainly in leaves and roots [9]. During summer and autumn the N requirements were met to a large extent from redistribution of the N previously taken up.…”

“…To meet the large N demand that occurs in spring, N is both absorbed by the root and remobilised from storage pools. Estimates of the contribution of the internal cycling of N in this crop has been provided by Smith et al [17] using cuttings from one year old canes grown in spring in distilled water, and by Ledgard and Brier [7] and Ledgard and Smith [8] analysing xylem sap from vines supplied with 15 N. Remobilisation of N from storage in perennial organs contributes to a large extent to their annual N demand in a range of perennial fruit crops, and provides a supply of N for early spring vegetative and reproductive growth, before rapid root uptake occurs [10]. Sanchez et al [15,16] reported that some 45% of the N requirement for annual growth of 5-year-old pear trees comes from internal cycling, while this contribution has been estimated by 50% and 84% respectively for mature almond [21] and citrus [4] trees.…”