Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 2008-2009
Dr. Patrick Brown !"#$%&' !"#$%&'()*+,-&'(*"(./0(1'+%2(10,.%'%30,(1*+-2&.%*- !"#$%! !"#$%&'()*+%,--. /012%345%602%75%899:$%;<= !"#$!%#&'&()*!+)*,$-!./#!0,'#&$1'!2)1)3$4$1'!51! "*4/16!"16!7&-')(8&/!9#(8)#6-!51:)*&6; !"#$%&#'$("(#)((*#%#&+&'(,%'-.#,-&/&(#01#&%,23-*4#,('$050304+# %*5#%*#-*5/&'"+6#7%*5#/*-8("&-'+69#:-5(#,-&-*'("2"('%'-0*#01#"(&/3'&; Summary: Ninety percent of growers and consultants participating in recent grower and consultant focus groups on nutrient management in tree crops, and the majority of respondents to an industry-wide survey, felt that the University of California (UC) “critical values” (CVs) for nutrient management in almond and pistachio were inadequate for modern production levels based on 1) current CVs are limited in application or 2) there are systematic errors in use of critical values. Review of current and historic data, however, indicates that the University of California established CVs for almond and pistachio production were reasonable and unlikely to be sufficiently incorrect to warrant the largely negative industry perceptions. It is apparent, however, that there has been a systematic misuse of sampling methodology and industry- (and university-) wide misinterpretation of results. Discussions with plant nutritionists working in high-value crops in the U.S . and in the international community suggest that this ‘simple’ misinterpretation of the use and interpretation of tissue samples is widespread. The large variability in leaf nutrient concentrations seen in tree crops has resulted in the development of standardized sampling techniques that strive to limit variability from sample to sample. While it is true that the use of a standardized sampling protocol is essential if you are to contrast results with a predetermined standard, this does not necessarily imply that such leaf samples are either the most sensitive or the most relevant indicators of tree nutrient status or potential for response. The choice of a July, non-fruiting, exposed spur leaf for nutrient analysis in almond is clearly a compromise selected to ensure low variability. There has been no study (to our knowledge) that specifically attempts to determine the relative sensitivity of this standard leaf in California almonds with any other leaf type or time of sampling. In addition to within-tree variability in leaf nutrient status, there is also a great deal of within-orchard and between-orchard variability that occurs as a consequence of variability between trees, changes in soil conditions, and local microclimate. Typically, this within-field variability is not considered in sampling and, as a consequence, can lead to incorrect interpretation This principle is illustrated in the following graph of 50 independent single-tree nutrient samples taken, one per row, across a mature almond orchard (Figure 1). In this example, leaf K concentrations vary greatly in the 50 sampled trees in this highly productive orchard. The average leaf K of this orchard is 2 percent, which is significantly greater than the University of California (UC)-recommended 1.4 percent K. Current UC recommendations would suggest this field is over-fertilized. The grower, however, is convinced, and has good yield records to verify it, that he obtains his highest yield when he targets a field average K concentration of 2 percent. The reason for this apparent © Hope Harris 2009 Figure 1. Leaf K values were determined in 50 individuals (1 per row) across a 50-acre orchard. The current CV for K in almond is 1.5%. Here the grower has targeted a field CV of 1.9% with the resultant effect that yield response to K has been maximized and 95% of all individuals have a tissue K value exceeding 1.5%.
Fluid Journal 2005-2007