Nutrient Management Research Database

This paper discusses the use of foliar sprays to address transient nutrient deficiencies and short term deficiencies, such as those that occur at peak demand. It is hypothesized that transient nutrient deficiencies occur due to limitations in uptake or restrictions in nutrient delivery during peak nutrient demand. Therefore, foliar sprays are utilized to allow for a localized and tailored nutrient application that are not easily obtained using solid or blended soil products. Little research has been done on the effectiveness of foliar sprays, generally, fertilizers that are applied to the roots are far less expensive than foliar spray. Therefore research as to the best situations to use foliar sprays provides information for economic success, as well as the fertilization strategies. This report covers multiple reports on 10 years of targeted research on boron and potassium fertilization and deficiencies. Multiple tree crops were used, and potassium deficiency and fertilization in almonds was studied. Result suggest that foliar sprays are a highly effective method to deliver potassium to almond trees due to the localized nature of potassium deficiencies

This report surveys multiple research projects.

• With respect to almonds, potassium fertilizer was applied to Non-Pareil almonds at the rates of 0, 240, 600, and 960 lbs potassium, directly under the drip emitters in 3 applications in 1998 (May 23, June 17, and July 3) and in 2 applications in 1999 (Feb 26 and April 29).
• Samples from the low and high treatments were taken to monitor yield determinants, leaf potassium concentrations, and individual spur longevity over several years.

• There was no significant effect on yields in 1998 or 1999 among treatments, yield did increase in 2000 by 18% with potassium application compared to the control.
• Potassium increased yields by increasing the number of vegetative spurs.
• Results of tissue analysis indicate highly localized potassium deficiency in spurs in otherwise symptom free trees.
• The authors believe that foliar application of potassium for almond trees will be uniquely effective in treating the highly localized potassium deficiencies.
• The nutrient deficiencies at an individual branch or spur level may not trigger root uptake of nutrients, meaning that foliar sprays are the best option to address localized deficiencies.