Foliar nutrient concentrations of three economically important tree species in an alley-cropping system

Abstract

Alley-cropping systems that pair economically important tree species with crop production in alleyways have the potential to diversify outputs and improve resource use efficiency. However, management practices are more complex because trees and crops have different nutrient requirements and access different depths in the soil profile. Foliar nutrient concentrations are often used to determine fertility plans for fruit and nut production orchards, but these recommendations may not be appropriate in integrated tree and crop production systems. This research describes foliar nutrient concentrations in three different tree species, red oak (Quercus rubra L.), pecan [Carya illinoinensis (Wangenh.) K. Koch], and black walnut (Juglans nigra L.), at an alley-cropping site in northwest Arkansas, USA from 2004 to 2012. Foliar nutrient concentrations did not differ in trees fertilized by poultry litter when compared to those receiving synthetic N fertilizer. Concentrations of nutrients changed over time in all three species, with Mg and Ca increasing and N, K, S, Fe, and Na decreasing as trees aged. A principal components analysis indicated that leaf nutrient levels in oak and pecan were much more similar to each other than to black walnut. Some of the foliar nutrient concentrations identified in this study were inconsistent with sufficiency ranges reported in fruit and nut production orchards. However, given the multiple aims of an alley-cropping system, these inconsistencies may not represent deficiencies in available nutrients for these tree species.