Nutrient Management Research Database

This study had two main objectives:

1. Investigate the effects of foliar N application on tree nutrient levels and growth.
2. Compare foliar and soil N applications on tree growth and fruit set.

Foliar Application

Apple trees were found to take up N from sprays early in the season. The best spray timing was with the opening of the king bloom. Both urea and calcium nitrate were of equal effectiveness.

Foliar urea application in the autumn resulted in apple leaves readily absorbing N, which was quickly stored by the tree.

Upper and lower leaf surfaces were able to absorb from the foliar application, however the lower surface absorbed N four times more quickly. Tree bark could also take up N.

Fall urea foliar spray after harvest increased tree N storage and subsequently increased fruit size and yield the next season.

Differences Between Foliar and Soil Applications

Summer application of urea resulted in increased above ground growth. Foliar application resulted in increased root growth. Soil application led to extension root initiation and foliar application promoted feeder root initiation. Following soil application, leaf N uptake was increased in the autumn, while foliar application improved root N uptake.

Both foliar and soil N applications improved leaf N levels, leaf color, fruit size, and total yield. Soil N application increased shoot length, though due to increasing soil nitrate and ammonium levels was also less effieicnt than foliar application.