CALIFORNIA Patterns of Nutrient Accumulation in ‘Hass’ Avocado Fruit By Richard Rosecrance, Ben Faber, and Carol Lovatt Synchronizing plant nutrient demand with fertilizer application increases nutrient use efficiency, is cost-effective, and protects the environment. Avocado trees were sampled during their 2-year growing cycle to determine the pattern of nutrient accumulation in the fruit as a guide for better timing of fertilizer applications.
n understanding of seasonal nutrient require- ments of crops is important in order to develop Abest fertilizer management practices. ‘Hass’ avocado trees absorb nutrients according to seasonal growth patterns, and matching fertilizer applications to those patterns can maximize yields, improve fruit quality, increase nutrient uptake, and reduce the po- tential for nutrient loss. Avocado fruit is unique because it remains on the tree for 15 to 18 months after spring bloom (i.e. two growing seasons) and the developing fruit is a strong sink for nutrients (Figure 1). Fruit N removal values in the literature range from 11 to 61 kg N/ha based on a 10 t/ha crop yield. However, little is known about the pattern of nutrient uptake into avocado fruit. This understanding is important to schedule fertilizer ap- plications to coincide with periods of high nutrient demand, thereby maximizing nutrient use efficiency. Research was conducted in a commercially bearing mature ‘Hass’ avocado orchard growing on a gravelly loam (thermic Typic Argixerolls) in Moorpark, Califor- Avocados are grown in more than 60 countries. The Hass variety (shown here) is the nia. Fruit samples were harvested monthly for 1 year most common, but other locally adapted varieties are also cultivated. from two different trees each month. The total fruit weight and number of fruit per tree were determined as were Dry Weight and Nutrient Accumulation Patterns the concentrations of specific nutrients in the tissues of fruit. Fruit dry matter accumulation followed a double sigmoid curve (Figure 2). Fruit growth was split evenly over the 2 years, with about half of the total fruit dry weight accumulating Skin (exocarp) during the first growing season and half accumulating the fol- 20% of total dry weight lowing year. Dry matter accumulation ceased during the winter months (i.e. December to March). This differs from avocados 1.1% N N growing in tropical environments where fruit growth follows a 0.17%0.2% P P single sigmoid curve. 2.1% K K Similar to the dry matter growth curve, avocado fruit ac- cumulated most nutrients in a double sigmoid pattern with Flesh (mesocarp) nutrient uptake ceasing during the winter months (Figure 3). 67%13% of total dry weight Accumulation patterns, however, differed for the individual 1.3% N nutrients. Approximately 50% of the total fruit nutrient uptake 0.8% N for N, P, Mg, and S occurred during the first year and 50% 0.23% P 0.2% P accumulated during the second growing season. In contrast, 2.1%1.0% K K only about 30% of the total fruit K and B accumulated during the first year, and the remaining 70% accumulated during the Seed (endocarp) second growing season. In contrast to other nutrients, fruit Ca 13% of total dry weight content followed a single sigmoid curve, where it increased 67% of total dry weight during the first 5 months following bloom and then remained 0.75% N 1.3% N constant until fruit harvest in September the next year (Fig- 0.21%0.2% P P ure 2). 1.0%2.0% K K Timing Fertilizer Applications to Figure 1. The dry weight and nutrient content (dry weight basis) of Meet Tree Nutrient Demand mature avocado fruit skin, flesh, and seed. Avocado fruit accumulated the majority of nutrients be- tween full bloom and autumn and also during the following Common abbreviations and notes: N = nitrogen; P = phosphorus; K = spring. These periods of high fruit nutrient demand should
Better Crops/Vol. 96 (2012, No. 1) Crops/Vol. Better potassium; S = sulfur; Mg = magnesium; Ca = calcium; B = boron. coincide with timely fertilizer applications. For example, 12 Better Crops/Vol. 96 (2012, No. 1) 13
- - - BC Synchronizing the timing of fertilizer ap N K P S Ca Mg Dr. Dr. Rosecrance is an Associate College Professor, of Agric., Calif State Univ, Chico; e-mail: Advisor rrose Farm a is Faber Dr. [email protected]. in Ventura County, Univ. Calif., Dr. Lovatt is a Dept. Botany Calif., & Plant Sci. Univ. Professor, Riverside, CA. plications with plant nutrient demand is criti is demand nutrient plant with plications cal for the successful production of avocado right the consider to important also is It fruit. fertilizer source, rate, and placement of the added nutrients in order to meet the desired economic and environmental objectives. ‡ A. AMJJASONDJFMAMJJ B. C. AMJJASONDJFMAMJJ AMJJASONDJFMAMJJ 0 A fruit from bloom to harvest. Uptake patterns are shown shown are patterns harvest.fruit bloom to from Uptake Ca and Mg (B), and P and S (C). N and K (A), for avocado nutrients in‘Hass’ ccumulation ofselected 800 600 400 200 0 0 90 80 70 60 50 40 30 20 10 50
2,000 1,800 1,600 1,400 1,200 1,000
100
250 200 150 100
.
Fruit nutrient content, mg/fruit content, nutrient Fruit † 401 Fruit nutrient content, mg/fruit content, nutrient Fruit to support the maturing fruit. y during early fruit development. Fruit nutrient content, mg/fruit content, nutrient Fruit 9 to 47 9 to 10 to 58 10 to 47 to 212 47 to 45 to 156 45 to Figure 3. Ca – Since most of the Ca was accumulated during the first available be must supply abundant an growth, fruit of ear Other literature Other
- - -
192 245 267 212 229 Table Table This study ------g/ha ------Nutrient B Fe Zn Mn Cu ‡ 4 to 8 4 to 2 to 7 2 to 4 to 8 4 to 2 to 10 2 to 11 to 41 11 to 20 to 61 20 to – Apply these nutrients during Other literature Other Total Flesh Seed Peel 22 30 24 25 21 23 This study ------kg/ha ------kg/ha AMJJASONDJFMAMJJ Dr to harvest.to Nutrients removed from an avocado crop based on a 10 t/ha yield crop an avocado from removed Nutrients fruit bloom from accumulationinanavocado y matter 0 90 80 70 60 50 40 30 20 10
on as well as the maturing fruit. d t t s To To synchronize fruit nutrient demand with fertilizer ap- Fertilizer applications at the very least must replace nu Dry weight, g/fruit weight, Dry Calculated on a fresh weight basis. weight on a fresh Calculated Table 1. Table Specific literature citations are available at http://info.ipni.net/BCADDENDA. available are citations Specific literature † ‡ N Nutrient P K S Ca Mg N, P, Mg, S, Fe, and Zn Mg, S, N, P, plication, we recommend for: trients removed in fruits to avoid soil depletion. In this study, study, this In depletion. soil avoid to fruits in removed trients avocado t/ha 10 a by removal nutrient secondary and primary ( Mg 3 and Ca, 1 S, 5 P, 4 K, 30 N, 22 (kg/ha) was crop nutri crop influence also will orchard the in factors Other 1). tree age. and cultivar, ent removal, such as rootstock, scion needed be may rate application higher a load, fruit the K and B – These nutrients are accumulated more rapidly Depending development. fruit of season second the uring again repeat and bloom full after season growing Spring he strategy This period. time same the during year second he upplies nutrients to the recently pollinated flowers in earlier experiments N fertilization in the increased both springfruit size and (April)yield and reduced the severity of alternate-bearing compared with trees receiving N at any other time of the year besides April. April N fertilization ap Figure 2. pears to be critical for fruit set of the new crop, for growth of the of growth fruit support to and flushes, shoot vegetative the maturing crop.