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New working standards for leaf analysis of pistachio ‘Sirora’ in Australia

The Australian pistachio industry is young in international terms. Until now Australian pistachio growers have relied on the leaf analysis standards developed in California to assess the nutrient status of producing orchards. The Californian standards were developed for the cultivar ‘Kerman’, whereas nearly all Australian orchards are planted to cultivar ‘Sirora’. We have used data from (a) long term on-farm monitoring samples, and (b) industry benchmark surveys, and (c) a long term nitrogen fertiliser trial, to develop some new “working standards” for use in Australian orchards. Comparative on-farm sampling showed that ‘Kerman’ shows higher values for nitrogen, phosphorus, potassium, sulfur and boron than ‘Sirora’ when grown under the same conditions. Our proposed “working standards” based on leaflets sampled from mature leaves on non-fruiting shoots, in late January or early February (southern hemisphere) are as follows: N - Critical Value 1.6% (DW basis), Satisfactory range >1.8% (%DW basis); P - Critical Value 0.11%, Satisfactory range >0.12%; K - Critical Value 1.4%, Satisfactory range >1.6%; Ca - Satisfactory range >1.5%; Mg - Critical Value >0.4%, Satisfactory range >0.5%; Na - Satisfactory range >15 mg kg-1; Mn - >30 mg kg-1. We suggest that these “working standards” should be used with caution by Australian pistachio growers until the industry as a whole has gained some confidence in their usefulness. The difficulty of developing standards for pistachio, which is so severely biennial in cropping habit, is discussed. Care should be taken when interpreting leaf analysis data, particularly for micro-nutrients, to take account of potential contamination with foliar nutrient sprays, fungal protectants and environmental dust.