NUTRIENT UPTAKE AND DISTRIBUTION. Tagliavini, M 1, Zanotelli, D 1.

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1 NUTRIENT UPTAKE AND DISTRIBUTION Tagliavini, M 1, Zanotelli, D 1 massimo.tagliavini@unibz.it 1 Faculty of Science and Technology, Free University of Bozen-Bolzano, Italy KEYWORDS Calcium, dynamics of nutrient uptake, magnesium, nitrogen, nutrient partitioning, phosphorus, potassium, tree growth, uptake rate, yields. ABSTRACT Annual uptake of nutrients from the soil, and sometimes from the leaves, at desired rates and timings, is necessary for apple and pear trees to successfully complete their vegetative and reproductive cycle, produce high quality fruits, and become economically viable. Nutrient uptake provides for an optimal concentration of nutrient in tree organs to sustain growth, yields, flower bud formation, and the building of nutrient reserves. Nutrient uptake occurs with rates and dynamics depending on tree factors like growth rate (Figure 1) and yields, but also on environmental factors and nutrient availability. Figure 1 Example of total annual new biomass (NPP tot ) produced by apple trees and its partitioning to fruits (NPP fruits ). Data are in t D.W. per hectare and refer to cv. Fuji on M9 with fruit yields around t fresh weight ha -1 (27-29 t/acre)

2 Our quantitative knowledge about the amounts of absorbed nutrients under field conditions is derived either by 1) quantification of new biomass produced every year and its nutrient concentration or 2) by stable isotope techniques. For mature fruit trees, regularly subjected to pruning, it is often assumed that the increment of biomass of the framework of adult trees could be approximated to the amount of pruning wood, as secondary growth is considered low and negligible. Under these situations, nutrient uptake can be estimated by considering the amount of nutrients in the yield, in the pruning wood and in the abscised leaves (Table 1). Calcium (Ca), nitrogen (N) and potassium (K) are often the most absorbed nutrients. The partitioning of the absorbed nutrients within tree organs depends on their relative growth (Figure 1) and on specific nutrient needs. Most absorbed N is allocated to shoots and leaves, while most absorbed Ca is partitioned to leaves and woody organs. Pome fruits have low protein content and relatively low N requirements, while contain relatively high potassium. Therefore, the higher the yields the higher the K uptake and the need for K fertilizers. The rate of nutrient uptake varies along the season with dynamics that differs according to the nutrient. In apple, the uptake rate of N, phosphorus (P), Ca and magnesium (Mg) increases along the spring, slightly decreases in summer and markedly decreases approaching fruit harvest; K uptake rate, on the contrary, decreases only slightly in summer and approaching fruit harvest. Predicting annual amount and dynamics of the nutrient uptake, and their distribution in organs is a fundamental step for developing rational fertilization strategies in apple and pear orchards. Table 1 Example of nitrogen uptake, assumed equal to the nitrogen content in fruits, abscised leaves and woody organs yearly produced. Tree organ Biomass (t D.W. ha -1 ) N concentration (% D.W.) N content (kg N ha -1 ) Abscised leaves Fruit Woody organs yearly produced Total

3 Nutrient uptake and distribution Massimo Tagliavini and Damiano Zanotelli 2015 WSU Fruit School Physiology of Apple and Pear November 2015

4 Introduction Nutrient availability in tree organs are necessary to adequately support vegetative growth and productivity. Both nutrient deficiencies and excesses should be avoided to reconcile economic and ecological aspects of sustainability in fruit production.

5 REFERENCE PRICE FOR SELECTED FERTILISERS IN THE INTERNATIONAL MARKET ($/t) Urea Ammonium phosphate Triple phosphate Potassium chlroride

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7 Nutrient uptake Nutrient uptake rates depend on environmental (soil) and tree internal factors An increase in soil nutrient availability normally increases uptake (especially true for N) Adequate root density (and new roots) and root C availability needed to support nutrient uptake

8 Source of nutrients for tree growh and production Soil «native» fertility and fertilisers provides nutrients for root uptake Foliar nutrient supply might contribute to fulfil the nutrient needs (to different extent depending on the type of nutrient) In spring, nutrients remobilised from storage organs support N metabolism during early vegetative growth phases, flowering and fruit set

9 Remobilized N supports the early vegetative and reproductive stages in apple (Neilsen et al., 1997) and pear (Tagliavini et al., 1997)

10 Nitrogen uptake (1) Both NH 4 + and NO 3- absorbed by apple and pear roots (Tromp and Ovaa, 1979) NH 4+ sometimes taken up preferentially as compared to NO 3- (Mota et al. 2011) NO 3- uptake stimulates shoot growth more than NH 4 + uptake, but the latter is sometimes reported as having positive effect on flower bud formation (Gao et al., 1992).

11 Nitrogen uptake (2) Presence of both NH 4+ and NO 3- in soil is often beneficial (evidences from other fruit crops). Not always easy to control NH 4+ : NO 3- ratio in soil due to microbial transformation of the N molecules. The higher the uptake, the higher the growth and the higher the uptake needs for other nutrients as well!

12 Relative P uptake rate Phosphorus (P) uptake rate by apple roots as affected by their age (Bouma et al. 2001) Root age (days)

13 The need for nutrient uptake ultimately depend on Vegetative and reproductive tree growth Specific needs (concentrations) of single organs

14 Tagliavini, Failla and Xiloyannis, 2012

15 Pome fruit mineral concentrations Pome fruits (apple and pear) mainly contain water and carbohydrates and are low in protein and therefore are relatively low in N ( kg/t F.W.) Their Ca, P and Mg concentration is low (approx kg/t F.W.) But they contain relatively high concentrations of K ( kg/t F.W.)

16 Nutrient concentration (on D.W. basis) ranges of main apple organs Organs N % P % K % Ca % Mg % Leaves (July) Leaves (senescent) Fruits Woody organs Roots

17 Example of total annual new biomass in apple trees and its partitioning to fruits in two years (cv. Fuji on M9 with fruit yields around t fresh weight ha -1 )

18 Apple tree growth rate along the season (data from Zanotelli e al and 2015)

19 Accumulation of N in apple fruits and shoots

20 Accumulation of P in apple fruits and shoots

21 Accumulation of K in apple fruits and shoots

22 Accumulation of Ca in apple fruits and shoots

23 Accumulation of Mg in apple fruits and shoots

24 Biomass accumulation and influx rates of nutrients in apple bourse shoots (with one fruit) from ful bloom (day 0 ) to harvest (day 158) (average of Golden del. and Nicoter. Zanotelli et al., 2014) Period (DaFB) BIOMASS mg D.W. /day N mg/day P mg/day K mg/day Ca mg/day Mg mg/day

25 Yearly new biomass and N uptake by apple and pear trees Biomass (t D.W./ha) N (kg/ha) Organs Pear (Abbè F.) 35 t/ha Apple (Fuji) 60 t /ha Apple (Gala) 40 t /ha Pear (Abbè F.) 35 t/ha Apple (Fuji) 60 t /ha Apple (Gala) 40 t /ha Leaves (senescent) Fruits New woody organs (above ground) Roots Total

26 Yearly nutrient uptake by pear trees (cv. Abbè Fetel). Data are averges of three rootstocks average yields 35 t/ha. Organs N (kg/ha) P (kg/ha) K (kg/ha) Ca (kg/ha) Mg (kg/ha) Leaves (abscised) Fruits Woody organs (above ground) Roots Total Tagliavini and Quartieri, 2008

27 Nitrogen (% of dry weight) Different N concentration of apple leaves as affected by the genotype Days after full bloom Source: Beratungsring Manual Boden und Pflanzenernhärung in Obstbau, Weinbau und Bioanbau, 2004

28 Foliar uptake versus soil uptake Foliar uptake alone is inadequate to meet the magnitude of plant demand from macronutrients, but can complement root uptake. If soils are well endowed with Ca, but Ca-related disorders occur, then direct uptake of Ca by fruit cuticle can solve the problem.

29 Bitter pit disorder Courtesy Neilsen G., 2001

30 Foliar uptake versus soil uptake Foliar uptake alone is inadequate to meet the magnitude of plant demand from macronutrients, but can complement root uptake. If soils are well endowed with Ca, but Ca-related disorders occur, then direct uptake of Ca by fruit cuticle can solve the problem. Foliar absorbed micronutrients represent an important way to supply them, due to Small amounts requested Low availability of micronutrients in many soils Soil deficiency and toxicity thresholds often very close

31 When foliar uptake is likely to be effective 1. At growth resumption in spring, when remobilization has finished and root uptake is suboptimal 2. During the growing season, when nutrient soil availability does not meet nutrient demand 3. When we see symptoms or analysis show deficiencies that need to be quickly overcome 4. When the nutrient is unavailable if soil-applied (es. when no irrigation is available) 5. In late summer to rebuilt nutrient reserves, for those nutrients with phloem mobility

32 Final remarks Nutrient partitioning affects the fate of the absorbed nutrients

33 Uptake and partitioning Fluxes at Tree scale fruits Framework woody Organs tree leaves pruning wood uptake abscised leaves SOIL

34 Nutrients contained in decomposing leaves are released and become available again for uptake Tagliavini et al., 2007

35 Final remarks Nutrient partitioning affects the fate of the absorbed nutrients Nutrient uptake dynamics data should be used together with tools able to assess soil nutrient availability to fine tune the fertilisers supply in order to match nutrient needs and nutrient availability.

36 THANKS FOR YOUR ATTENTION