Nutrient Management Research Database

This project developed means to estimate seasonal nitrogen demand in a mature, high yielding Non-Pareil almond orchard. This was done to develop a computer model for nitrogen fertilization and recommendations. Studies involving 9 commercially managed orchards with 12 trees each and two locations with predetermined nitrogen application rates suggested that both leaf total nitrogen and leaf nitrate-nitrogen are poor predictors of almond meat production. Results of tree excavation at different growth stages suggested that total removal of nitrogen from almond harvest and leaf drop from a mature tree with a per acre nut meat yield of 4200 lb was 3.8 lb per tree. To balance the full year nitrogen demands of the almond tree, total nitrogen uptake from the soil was 4.3 lbs per tree. Of this amount, 13% was taken up during spring flush (Jan-mid-March), 42% between spring flush and nut fill (Mid May), and 45% during summer. This information on nitrogen uptake will provide guidance for deeming the timing of split nitrogen applications, to optimize the nitrogen use efficiency. this information is now being used to develop a fertilization recommendation model.

• Studies were conducted on nine commercially managed orchards in two locations.
• Researchers conducted field validations of leaf nitrate levels, took tissue samples, and analyzed data to build a computer model to generate nitrogen fertilizer recommendations for growers.

• Results show that total leaf nitrogen and nitrate-nitrogen levels at the end of July are not good predictors of almond tree meat yields. This is likely due to the fact that leaf nitrate-nitrogen levels change dramatically during the growing season as fertilization and irrigation events occurred.
• To fulfill the plant's nitrogen requirement, total nitrogen uptake from the soils was 4.3 lb per tree.
• 3.8 lbs nitrogen per tree was removed during harvest and by leaf drop from a tree.
• Average per acre nut meat yield was 4200 lbs.
• 13% of the nitrogen was taken up during spring-flush (January to mid-March); 42% was taken up from spring flush to nut fill (Mid-March to Mid-May), and 45% during the summer.
• This data is valuable for determining the timing and rate of fertilizer application.