Breadfruit has experienced an exponential increase of plantings in Hawai‘i (Langston and Lincoln, 2018) and an increase in distribution and cultivation globally (Lincoln et al., 2018). The Food and Agriculture Organization of the United Nations (2009) has recognized breadfruit as one of 35 priority crops for its tremendous potential to improve global food security, human nutrition, and climate-smart agriculture in the tropics (Lucas and Ragone, 2012; McGregor et al., 2016). As one of the few staple foods that grow on long-lived perennial trees, breadfruit has potential to dramatically shift cultivation practices in tropical regions away from annual crops. Breadfruit is highly productive, with consistent yields of at least 5 t·ha−1 edible dry weight [see Lincoln et al. (2018) for compilation of reported yields] and was an important element of Hawaiian food systems in the past (Lincoln and Ladefoged, 2014; Winter et al., 2018). Despite the growing interest and awareness of the production potential of breadfruit, it remains underused and suffers from significant lack of research investment (Lincoln et al., 2018; Ragone, 2007). Thus, substantial gains in breadfruit yield are probable with relatively little agronomic research and breeding effort (Sraffa, 2005; Willcox, 1954).
Foliar nutrient analysis is a well-established method (Munson and Nelson, 1990) to assist in the diagnosis of nutrient-related problems (deficiencies, toxicities, imbalances, etc.) of both annual and perennial crops. Assessment of foliar nutrient concentrations can be applied to inform fertilizer management, rule out nutrition as a source of a production variability, and assess the impact of management techniques on the nutrient status of crops. Foliar nutrient analyses are employed through tissue-sampling methods, which are contingent on sampling location, plant part selected, and the stage of growth. Specific sampling protocols may be dependent on the crop type and purpose (Munson and Nelson, 1990). Furthermore, optimal nutrient levels must to be established for each individual crop. Although important work has been done for many fruit crops (Jones, 2001), including species related to breadfruit (Poovarodom et al., 2000; Sun et al., 2015; Tawinteung et al., 2001), no studies investigating foliar sampling protocols for breadfruit were identified (Lincoln et al., 2018).
Using data from commercial and research orchards in Hawai‘i, we explored foliar sampling methods of breadfruit to inform a sampling protocol. Sampling entire breadfruit leaves is impractical due to their size (we have measured leaves up to 1.4 m in length). Thus, implementing a method that uses a portion of a leaf is necessary. Our primary objective was to assess leaf location and leaf part for suitability in foliar nutrient diagnosis and to validate potential sampling protocols using measurements of breadfruit productivity.
Anjaneyulu, K. 2007 Diagnostic petiole nutrient norms and identification of yield limiting nutrients in papaya (Carica papaya) using diagnosis and recommendation integrated system Indian J. Agr. Sci. 77 3 6
Bell, D.T. & Ward, S.C. 1984 Seasonal changes in foliar macro-nutrients (N, P, K, Ca, Mg) in Eucalyptus saligna and E. wandoo growing in rehabilitated bauxite mine soils of the Darling Range, Western Australia Plant Soil 81 377 388
Chang, S.X. & Robison, D.J. 2003 Nondestructive and rapid estimation of hardwood foliar nitrogen status using the SPAD-502 chlorophyll meter For. Ecol. Mgt. 181 331 338
Food and Agriculture Organization of the United Nations 2009 International treaty on plant genetic resources for food and agriculture, 56. 29 May 2019. <http://www.fao.org/3/a-i0510e.pdf>
Gavlak, R., Horneck, D., Miller, R.O. & Kotuby-Amacher, J. 2003 Soil, plant and water reference methods for the western region. WCC-103 Publ. Fort Collins, CO
Jones, J.B. Jr 2001 Laboratory guide for conducting soil tests and plant analysis. CRC Press. Boca Raton, FL
Lincoln, N.K. & Ladefoged, T.N. 2014 Agroecology of pre-contact Hawaiian dryland farming: The spatial extent, yield and social impact of Hawaiian breadfruit groves in Kona, Hawai’i J. Archeological Sci. 49 192 202
Lincoln, N.K., Ragone, D., Zerega, N., Roberts-Nkrumah, L.B., Merlin, M. & Jones, A.M. 2018 Grow us our daily bread: A review of breadfruit cultivation in traditional and contemporary systems Hort. Rev. 46 299 384
Lucas, M.P. & Ragone, D. 2012 Will breadfruit solve the world hunger crisis? New developments in an innovative food crop ArcNews Summer 6 7
McGregor, A.M., Tora, L.D. & Lebot, V. 2016 Planting breadfruit orchards as a climate change adaptation strategy for the Pacific islands Acta Hort. 1128 55 66
Munson, R.D. & Nelson, W.L. 1990 Principles and practice of plant analysis, p. 359–388. In: R.L. Westerman (ed.). Soil testing and plant analysis. 3rd ed. Soil Sci. Soc. Amer., Madison, WI
Neilsen, D., Hogue, E.J., Neilsen, G.H. & Parchomchuk, P. 1995 Using SPAD-502 values to assess the nitrogen status of apple trees HortScience 30 508 512
Netto, A.T., Campostrini, E., de Oliveira, J.G. & Bressan-Smith, R.E. 2005 Photosynthetic pigments, nitrogen, chlorophyll a fluorescence and SPAD-502 readings in coffee leaves Scientia Hort. 104 199 209
Poovarodom, S., Tawinteung, N., Mairaing, S., Prasittikhet, J. & Ketsayom, P. 2000 Seasonal variations in nutrient concentrations of durian (Durio zibethinus murr.) leaves Acta Hort. 564 235 242
Sraffa, P. 2005 The laws of returns under competitive conditions, p. 216–233. In: G.Z. Sun (ed.). Readings in the economics of the division of labor: The classical tradition. Vol. 2. World Sci. Publ., Singapore
Sun, Y., Yang, J., Wang, H., Zu, C., Tan, L. & Wu, G. 2015 Standardization of leaf sampling technique in jackfruit nutrient status diagnosis Agr. Sci. 6 232 237
Van den Berg, A.K. & Perkins, T.D. 2004 Evaluation of a portable chlorophyll meter to estimate chlorophyll and nitrogen contents in sugar maple (Acer saccharum Marsh.) leaves For. Ecol. Mgt. 200 113 117
Ware, G.O., Ohki, K. & Moon, L.C. 1982 The Mitscherlich plant growth model for determining critical nutrient deficiency levels 1 Agron. J. 74 88 91
Winter, K.B., Lincoln, N.K. & Berkes, F. 2018 The socio-ecological keystone concept: A quantifiable metaphor for understanding the structure, function, and resilience of a biocultural system Sustainability 10 3294
Wludyka, P. & Sa, P. 2004 A robust I-Sample analysis of means type randomization test for variances for unbalanced designs J. Stat. Comput. Simul. 74 701 726