Fall Nutrient Sprays in Tree Fruit

Written by Bernardita Sallato, Updated October 2024. Dowload Fact Sheet publication FS365E

Carbon (C), oxygen (O), and hydrogen (H), taken up in the form of carbon dioxide (CO2) and water (H2O), are the most important nutrients for tree fruit growth and development, representing more than 95 percent of the tree dry matter (Marschner 2002). The rest of the nutrients represent the other five percent, and their uptake occurs mainly through the roots, between bloom and the rapid vegetative growth phase. In most perennial tree fruit, initial spring growth and early fruit development rely on reserves accumulated the previous season (Weinbaum et al. 1984). Thus, fall nutrient management strategies have had positive effects on building those reserves in apples (Nielsen et al. 1996) and cherries (Lang 2005). However, the effectiveness of fall sprays will depend on the overall tree health, deficiency level, and demand. This publication presents some considerations to decide whether fall sprays are needed.

In tree fruit and other plants, macronutrients such as nitrogen (N), potassium (K), phosphorous (P), calcium (Ca), magnesium (Mg) and sulfur (S) are required in much larger amounts than micronutrients (Table 1). In most intensive cropping systems, the demand of macronutrients can surpass soil availability (or soil supply), requiring nutrient correction or maintenance. For example, K demand in a ‘Gala’ orchard can be 400 times the demand for boron (B) (calculated from Cheng and Raba, 2009). Nutrient uptake is most effective through plant roots; thus, soil application is preferred under adequate growing conditions (healthy roots, soil pH between 5.5 and 7.5, welldrained soil, moderate soil temperatures, among other factors).

Table 1. Ranges of nutrient concentration (% d.w) in tree fruit. (Adapted from Silva and Rodriguez, 1995 and Faust, 1989)

Element	Percent (% d.w)
Carbon (C)	40 – 50
Oxygen (O)	42 – 44
Hydrogen (H)	6 – 7
Nitrogen (N)	1 – 3
Phosphorous (P)	0.1 – 0.3
Potassium (K)	1.5 – 3.0
Calcium (Ca)	1.5 – 2.5
Magnesium (Mg)	0.35 – 0.6
Iron (Fe)	0.008 – 0.02
Other micronutrients	< 0.01

Micronutrient uptake can be affected by root growth-limiting factors, including anoxia, parasitic nematodes, diseases, alkaline soils (pH above 7.5), and low soil temperatures, where zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), and boron (B) are precipitated and unavailable. Given that micronutrients are required in small quantities (parts per million), they can effectively be managed with foliar sprays, especially when there are some underground limitations (Fernandez et al. 2013). Micronutrients required early in the season, before root uptake starts, can effectively be managed with delayed dormant prays, especially in areas with low soil temperatures. Keeping adequate levels of micronutrients in the soil will benefit root growth and tree health.

Fall nutrient sprays can be utilized for different purposes: to ensure adequate reserves for the following season (Johnson et al. 2001; Dong et al. 2002), to manage vigor and return bloom or for disease control (Beresford et al. 2015; Burchill 1968; Carreño and Pinto de Torres 1982). However, before making a decision, it is important to define your needs and management goals. In the following sections, a few examples and considerations are provided for deciding if N, Zn, and B fall sprays are needed.

Nitrogen (N)

Nitrogen is required in large quantities for tree fruit production systems and is a highly mobile nutrient in the plant and in soils (Table 2). In plants, N is a component of many compounds such as chlorophyll, amino acids, proteins, and nucleic acids, and is also part of many metabolic processes.

Table 2. Macronutrient demand per ton (US ton) of fruit produced.

Crop	lbs N/ US ton	References
Apples	1.2 – 2.6	Cheng and Raba 2009. Palmer and Dryden (2006), Silva and Rodriguez (1995), Sallato et. al, (2021)
Apricot	6.1 – 13.6*	Silva and Rodríguez, 1995. Fallahi et al 1993.
Cherry	3.3 – 12*	Silva and Rodríguez,1995. Weinbaum et al. 1984.
Peach	4.5 – 12*	Silva and Rodríguez,1995.
Pear	1.3 – 2.7	Silva and Rodríguez,1995.

*Includes vegetative growth.

The wide range in N demand reflects the wide variability that is dependent on cultivar, rootstock, tree density, vigor, tree shoot to fruit balance, among others. For example, ‘Gala’ on ‘Malling 26’ rootstock demands 2.6 lbs. of N per ton of fruit (calculated from Cheng and Raba, 2009) while preliminary data on the ‘Cosmic Crisp’ ® apple has shown a demand of 1.2 – 1.4 lbs. of N per ton of fruit over M9 and G41, respectively, in a three-year study developed by Sallato (unpublished data). Thus, the importance of determining demand needs to be addressed for specific cultivars, regions, and even individual orchard blocks.

During the fall, N within the plant is mobilized and translocated to the roots where it remains stored until the following season (Nielsen and Nielsen, 2003, Cheng et al., 2002, Dong et al., 2001, Dong et al., 2005, Ouzounis and Lang, 2011). In perennial trees, N and carbohydrate reserves are the main source of energy and nutrients for initial growth and early fruit development. This is particularly important in species where pollination and fertilization occur before leaves are fully expanded, such as cherries, apricots, peaches, nectarines, apples, and pears (Nielsen et al., 1996, Lang, 2005). In apples, Nielsen and Nielsen (2003) showed that remobilized N contributed to 50% of the N in shoots the following season, 90% of N in spur leaves, and 60% of fruit N.

Since remobilized N is critical for establishing N reserves for developing flowers, leaves, and fruit, fall N applications can benefit to build up reserves for the following season crop (Sanchez et al., 1990, Johnson et al., 2001, Ouzounis and Lang, 2011, Sallato and Whiting, 2021). When needed, fall N sprays should be done after harvest, between October and November, but before natural leaf fall when leaves start to turn yellow to ensure absorption and remobilization to the roots, trunk and buds (Sanchez et al., 1990, Johnson et al., 2001, Ouzounis and Lang, 2011). The efficacy of fall foliar N sprays can vary between 30 to 80 percent depending weather conditions. Guak et al. (2004) reported 48% absorption in apples sprayed with 2% urea. Before spraying, a decision is required to assess whether the block needs additional N reserves because under adequate nutrient conditions, foliar sprays are ineffective (Wójcik and Morgaś, 2013, Faust, 1989, Guak et al., 2004, Sallato and Whiting, 2021) and can sometimes contribute to toxicity or excessive vigor.

Conditions that indicate the need to build up reserves

• Nitrogen deficiency: nutrient deficiency can be diagnosed with visual symptoms of shoot growth or vigor assessment (Figure 1) (Righetti et al. 1998), complemented with leaf tissue samples. Concentration in recently mature leaves (mid-summer) below 1.7% in apples (Nielsen and Nielsen, 2003), 1.8% in pears and 2.0% in cherries are indicative of deficiency (Sallato et.al, 2019).

In apples, N deficiency can lead to biennial bearing. If you are in your “off year” and you expect higher cropping the following year, fall N can increase the shoot to fruit ratio in the “on years”. Avoid fall N sprays to prevent excessive growth the following season.

• Highly productive orchards: when trees have been cropped heavily, the demand for N increases and trees can decline in vigor. Table 2 can be used as a guide to estimate N demand based on yield. If the demand surpasses all the inputs (soil organic matter, N in the irrigation water, compost, etc.), growers can apply up to 20 lb N per acre in a single foliar application during the fall.

Conditions that indicate no need for building reserves

• Adequate N levels: tree N status can be determined with leaf tissue N levels during the summer and vigor assessment of the block. If tissue analyses are within adequate values and trees have balanced and adequate vigor, additional N sprays would be ineffective (Wojcik and Morgas, 2013). Adequate levels for N in recently mature leaves (mid-summer) should be in the range of 1.7 – 2.5% N (for more information visit https://treefruit.wsu.edu/orchard-management/soils-nutrition/fruit-tree-nutrition/).
• Excessive vigor: blocks with excessive vigor have sufficient N for the following spring, and additional N could be counter-productive (Figure 1, bottom photo). In blocks with excessive vigor, leaf tissue analysis can be deceiving. In highly vigorous tissue, N concentration can be diluted, thus, determination of N status should include a visual vigor assessment in addition to the tissue test. Excessive vigor can affect return bloom in apples, fruit quality, and susceptibility to diseases such as fire blight (Van der Zwet and Keil, 1979 cited by Nielsen and Nielsen, 2003) and powdery mildew in cherries.

 

Boron (B) Boron is a micronutrient that is fundamentally important for meristematic growth (new shoot and root growth), pollen germination and pollen tube growth, fruit set, xylem and phloem development, and consequently, fruit quality (Marschner, 2002, Brown and Hu, 1995). Thus, its demand is particularly important for fruit set early in the season (Wojcik and Wojcik, 2006, Cheng and Raba, 2009). Uptake of B by the roots is in the form of boric acid with mass flow (water movement). It has low mobility in the xylem, although in Prunus sp., Malus sp. and Pyrus sp. it has adequate mobility in the phloem (Brown and Hu, 1995).

Deficiencies have been reported widely in the PNW region due to extensive areas with high soil pH, cold soils, excessively drained soils, and dry soil conditions (Nielsen et al., 2004, Peryea et al., 2003). According to Callan et al., 1978 (cited by Faust, 1989), fall application of B is more effective than spring application in increasing B levels in flowers and improving fruit set. However effectiveness depends on the orchard deficiency levels. Effectiveness has most consistently been reported in trees with confirmed deficiency prior to the application. Peryea et al. (2003) reported that B maintenance sprays in apples and pears are more effective at pink flowering stage, and that postharvest sprays in the PNW have not been widely adopted in apples due to logistics and reduced efficacy in late ripening apple cultivars. More recently, Karlidag et al. (2017) demonstrated that the application of B (1000 ppm) plus 3% urea during the fall were effective in augmenting N and B in buds, improving flower development and fruit set.

Most soils in WA’s tree fruit growing area are low in B, and most growers manage the deficiency with foliar sprays. Thus, to monitor B deficiency in the trees, leaf tissue samples are better indicators than soils. Samples should be collected during mid-summer in leaves that have reached maturity, with adequate levels ranging between 20 to 80 mg/kg (ppm).   Although adequate or high levels of B in leaf tissue are not always correlated with fruit B concentrations, if B is low in leaves, deficiency in the fruit is more likely. Precautions should be taken with B sprays because there is a small margin between deficiency and toxicity. Faust (1989) indicated that one spray per season should be sufficient to prevent deficiencies in apples.

Zinc (Zn)

Zinc is a micronutrient involved in many enzymatic processes. Deficiency symptoms are very distinctive with smaller leaves, yellowing, rosetting, and short internodes (Figure 2) (Silva and Rodríguez 1995). Among different tree fruit crops, cherries and apples appear to be highly susceptible to Zn deficiency (Faust, 1989, Silva and Rodríguez 1995). Levels in recently mature leaves below 25 mg/kg are indicative of a deficiency.

In the PNW, deficiencies are most frequently in soils that are cold, wet, sandy and alkaline (pH above 7.5) where Zn becomes unavailable. Under these conditions, the deficiency relates more to a lack of uptake rather than a lack of supply; therefore, soil application of Zn is inefficient. Foliar sprays with Zn sulfate (ZnSO₄) during the fall and throughout the season have been shown to be effective in managing Zn deficiencies in apples (Nielsen and Nielsen, 1994), peaches (Sanches et al., 2006), sweet cherries (Sallato and Whiting, 2021) and tart cherries (Wójcik and Morgaś 2015). However, Zn has low re-translocation and high binding capacity in the plant (Zhang and Brown, 1999, Marschner, 2002), and as noted by Wójcik and Morgaś (2015) in sour cherry and Sallato and Whiting (2021) in sweet cherries, fall application of Zn only improved bud and flower levels and didn’t affect overall Zn levels in leaves, suggesting the need for frequent applications when deficiency persist.

Spray recommendations

For leaf nutrient sprays, mixing micronutrients with urea has been shown to improve uptake (Fernandez et al 2013, Sánchez and Righetti 2005). There are several formulations for each nutrient. The most common formulations are listed in Table 3. Whatever the source, always check the label recommendation. To calculate the amount of product based on the actual amount needed, divide the actual amount recommended by the percentage of the element indicated in the label.

Example: If the amount needed is 8 lb of N per acre, and the fertilizer is urea—46% actual N—then 8 lb ÷ 0.46 = 17 lb of urea per acre.

Table 3. General fall recommendation for tree fruit under diagnosed deficiency.

Nutrient	Formulation or salt, % active ingredient	Dose (lbs. of actual element in 100 gallons of water per acre)
Nitrogen	Urea (CO (NH2)2), 46%	8 – 10 lbs. of N. When using urea make sure has less than 0.25% biuret.
Calcium	Calcium nitrate (CaNO3), 19% Calcium chloride (CaCl), 34 – 36%	3 – 5 lbs. of Ca
Boron	Sodium borate (Na₂[B₄O₅(OH)₄]·8H₂O), 20.5% Boric acid (H₃BO₃), 10%	1 – 1.6 lbs. of B Boron is not suggested for nonbearing trees.
Zinc	Zinc sulfate (ZnSO4) 35%	8 – 10 lbs. of Zn for apples and cherries. 3 lbs. of Zn for peach and nectarine. For nonbearing trees apply 0.5 lbs.

Note: For nutrients containing sulfate (example; zinc sulfate), wait until temperatures are below 80 º F. Percent active ingredient might change among commercial products, make sure to read the label.

The effectiveness of foliar sprays will depend on the environmental conditions at the time of application (Guak et al., 2004, Fernandez et al., 2013). The most important considerations are:

• Don’t apply with temperatures below 68 ºF or above 85 ºF.
• High wind reduces drying time of the droplet and reduces absorption.
• Relative humidity. Low humidity influences droplet size and persistence in the leaf surface.

Other potential benefits

Fall sprays of urea have also been used to induce leaf drop when sprayed in higher concentrations. For example, urea at 5% has been used to reduce inoculum of Venturia inaequalis responsible for apple scab (Qazi et al., 2005, Beresford et al. 2015, Burchill, 1968, Carreño et al., 1982). Urea in combination with ZnSO₄ at a 2% concentration has successfully been used to induce early leaf drop after harvest, augmenting cold hardiness (Fernandez et al., 2002, Sallato and Whiting, 2021, Ouzounis and Lang, 2005).

Summary

• Fall sprays are beneficial and effective only when the trees are deficient for that particular nutrient.
• Fall nitrogen applications can help in building up reserves for critical early growth the next season.
• Fall zinc and boron sprays can improve fruit set and early fruit development.
• Fall spray applications should be applied when growth has ceased but before natural leaf fall.

For more information

Sallato, 2018. Leaf tissue analysis. Fruit Matters.

Sallato, B, T. DuPont, D. Granatstein. 2019. Tree Fruit Soil Fertility and Plant Nutrition in Cropping Orchards in Central Washington. Washington State University Extension Publication EM119E. Washington State University.

Contact

Bernardita Sallato C
WSU Tree Fruit Extension Specialist
b.sallato@wsu.edu
Mobile: 509 4398542

Bibliography

Beresford, R.M., I.J Horner and P. N. Wood. 2015. Autumn-applied urea and other compounds to suppress Venturia inaequialis ascospore production. New Zealand Plant Protection 53:387 – 392

Brown, P. H. and H. Hu. 1996. Phloem mobility of boron is species dependent: evidence for phloem mobility in sorbitol-rich species. Annals of Botany 77: 497 – 505.

Burchill,  R.  T.  1968.  Field  and  laboratory studies of the effect of urea on ascospore pro-duction  of  Venturia  inaequalis  (Cke.)  Wint.Ann. Appl. Biol. 62:297-307

Carreño,  I.,  and  Pinto  de  Torres,  A.  1982. Efecto de las pulverizaciones otoñales de ureaen  la  reducción  del  inoculo  primario  de  Venturia inaequalis (Cke.) Wint., en manzanos de la zona de Curicó, Chile. Agric. Tec. 42:235-238

Cheng, L. 2010. When and how much Nitrogen should be applied in Apple Orchards? New York Fruit Quarterly 18 (4): 25 – 28.

Cheng, L., S. Dong and L.H. Fuchigami. 2002. Urea uptake and nitrogen mobilization by apple leaves in relation to tree nitrogen status in autumn. J. Hortic. Sci. Biotechnol. 77:13–18.

Cheng, L. and R. Raba. 2009. Nutrient Requirement of Gala/M.26 Apple tree for high yield and quality. Cornell University.

Dong, S.F., D. Neilsen, G.H. Neilsen, and L.H. Fuchigami. 2005. Foliar N application reduces soil NO3-N leaching loss in apple orchards. Plant and Soil. 268:357-366.

Dong, SF, Cheng, LL, Scagel, CF, Fuchigami, LH. 2002. Nitrogen absorption, translocation and distribution from urea applied in autumn to leaves of young potted apple (Malus domestica) trees. Tree physiology 22(18):1305-1310. doi:10.1093/treephys/22.18.1305

Dong, S., L. Cheng and L.H. Fuchigami. 2001a. New root growth in relation to nitrogen reserves of young Gala/M26 apple trees. Acta Hortic. 564:365–370.

Dong, S., L. Cheng, P. Ding and L.H. Fuchigami. 2001b. Effects of foliar urea application in the fall on N reserves and cold hardiness of young Fuji/M26 apple trees. HortScience 36:600.

Fageria N.K., M.P. Barbosa Filho , A. Moreira and C. M. Guimarães. 2009. Foliar Fertilization of Crop Plants. Journal of Plant Nutrition, 32(6): 1044-1064.

Fallahi, E., Righetti, T.L. and Proebsting, E.L. 1993. Pruning and nitrogen effects on elemental partitioning and fruit maturity in “Bing‟ sweet cherry. Journal of Plant Nutrition, 16(5): 753-763.

Faust, 1989. Physiology of temperate zone fruit trees. John Wiley and Sons,. New York.

Ferguson, I.B. and C.B. Watkins. 1992. Crop Load Affects Mineral Concentrations and Incidence of Bitter Pit in ‘Cox’s Orange Pippin’ Apple Fruit. J. AMER. Soc. HORT. SCI. 117(3):373-376.

Fernandez, V., T. Sotiropoulos and P. Brown. 2013. Foliar Fertilization; Scientific Principles and Field Practices. First edition, IFA, Paris, France.

Guak, S., D. Neilsen, P. Millard, and N.E. Looney. 2004. Leaf absorption, withdrawal and remobilization of autumn-applied urea-N in apple. Can. J. Plant Sci. 84:259-264.

Johnson, R.S., R. Rosecrance, S. Weinbaum, H. Andris, and J.Z. Wang. 2001. Can we approach complete dependence on foliar-applied urea nitrogen in an early-maturing peach? Journal of the American Society for Horticultural Science. 126:364-370.

Karlidag, H., A. Esitken, M. Turan and S. Atay. 2017. The effects of autumn foliar application of boron and urea on flower quality, yield, boron and nitrogen reserves of apricot. Journal of Plant Nutrition 40: 19, 2721 – 2727.

Lang, G. 2005. Underlying principles of high density sweet cherry production. Acta Hort. 667:325-333.

Marschner H. 2002. Mineral Nutrition of Higher Plants. 3rd edition. Academic Press, London, U.K

Neilsen, G. H., Neilsen, D., Hogue, E. J. and Herbert, L. C. 2004. Zinc and boron nutrition management in fertigated high density apple orchards. Can. J. Plant Sci. 84: 823–828.

Nielsen D, P. Millard, G.H. Nielsen and E.J. Hogue. 1996. Sources of N for leaf growth in a high-density apple (Malus domestica) orchard irrigated with ammonium nitrate solution. Tree Physiology 17, 733-739.

Neilsen, G.H. and D. Neilsen. 1994. Tree Fruit zinc nutrition, p. 85–93. In: A.B. Peterson and R.G. Stevens (eds.). Tree fruit nutrition. Good Fruit Grower, Yakima, Wash.

Neilsen, G.H., Neilsen, D. 2003. Nutritional requirements of apple. In: D.C. Ferree and I.J. Warrington, eds. Apples: Botany, production and uses. CABI Publ., Oxford, UK. p. 267–302.

Ouzounis, T and G. Lang. 2011. Foliar Applications of Urea Affect Nitrogen Reserves and Cold Acclimation of Sweet Cherries (Prunus Avium L.) on Dwarfing Rootstocks. HortScience 46 (7) 1015–1021.

Palmer and Dryden. 2006. Fruit Mineral Removal Rates from New Zealand Apple (Malus domestica) Orchards in the Nelson Region. New Zealand Journal of Crop and Horticultural Science 34(1):27–32

Peryea, F.J., D. Nielsen and G. Nielsen. 2003. Boron Maintenance Sprays for Apple: Early-season Applications and Tank mixing with Calcium Chloride. HortScience 38(4): 542-546

Qazi, N. A, M.A Beig and K. Ahmad. 2005. Impact of post-harvest urea application on primary inoculum and infection of Venturia inaequalis (Cke.) Wint. and plant behaviour of apple. Applied Biological Research 7 (1/2), 37-43.

Righetti, T., K. Wilder, R. Stebbins, D. Burkhart, and J. Hart. 1998. Apples. Nutrient Management guide. Oregon State University Extension Service.

Sallato, B., Whiting, M. D., & Munguia, J. (2021. Rootstock and Nutrient Imbalance Leads to ‘‘Green Spot’’ Development in ‘WA 38’ Apples. HortScience, 56(12), 1542-1548. Retrieved Sep 30, 2024, from https://doi.org/10.21273/HORTSCI16213-21

Sallato, B. and M.D. Whiting. 2021. Early defoliation reduced yield and bud nutrient concentration in `Selah´ sweet cherry. IX International Symposium on Mineral Nutrition of Fruit Crops, June 28 – 30, Tel Aviv, Israel. Acta Horticulturae.

Sanchez, E. E, Weinbaum, S. A, Johnson, R. S. 2006. Comparative movement of labelled nitrogen and zinc in 1-year-old peach [Prunus persica (L.) Batsch] trees following late-season foliar application. The journal of horticultural science & biotechnology 81(5):839-844. doi:10.1080/14620316.2006.11512147

Sanchez, E.E and T. L. Riguetti. 2005. Effect of Postharvest Soil and Foliar Application of Boron Fertilizer on the Partitioning of Boron in Apple Trees. HORTSCIENCE VOL. 40(7) 2115-2117

Sanchez, E.E., T.L. Righetti, D. Sugar and P.B. Lombard. 1990. Responses of ‘Comice’ pear tree to a postharvest urea spray. J. Hortic. Sci. 65:541–546.

Shear, C.B. and M. Faust. 1980. Nutritional ranges in deciduous tree fruits and nuts. Horticultural Reviews 2, 142-163

Silva, H., and J. Rodríguez. 1995. Fertilización de plantaciones frutales. Colección en Agricultura. Pontificia Universidad Católica 519.

Weinbaum, S.A., I. Klein, F.E. Broadbent, W.C. Micke and T.T. Muraoka. 1984. Effects of time of nitrogen application and soil texture on the availability of isotopically labeled fertilizer nitrogen to reproductive and vegetative growth of mature almond trees. J. Am. Soc. Hortic. Sci. 109:339–343.

Wojcik, P. and M. Wojcik. 2006. Effect of Boron Fertilization on Sweet Cherry Tree Yield and Fruit Quality. Journal of Plant Nutrition, 29: 1755 – 1766

Wójcik, P. and H. Morgaś. 2013. Response of ‘Burlat’ sweet cherry trees to postharvest sprays of nitrogen, boron and zinc. Journal of Plant Nutrition 36(3):503-514. doi:10.1080/01904167.2012.748071

Wójcik, P. and H. Morgaś. 2015. Impact of Postharvest Sprays of Nitrogen, Boron and Zinc on Nutrition, Reproductive Response and Fruit Quality of ‘Schattenmorelle’ Tart Cherries. Journal of plant nutrition 38(9):1456-1468. doi:10.1080/01904167.2015.1009095

Zhang, Q.L., and P.H. Brown. 1999a. Distribution and transport of foliar applied zinc in pistachio. Journal of the American Society for Horticultural Science. 124:433-436.