Nitrogen
Nitrogen (N) is necessary for many tree functions, including growth, fruit bud formation, fruit set and fruit size. Because of the complexity of nitrogen interactions with quality and production, the best guide for nitrogen rates is leaf analysis.
Identification
- Symptoms first present in older leaves
- Leaves turn light green or yellow
- Affected leaves may drop prematurely
- Shoot growth is reduced and spindly
- Reduced bud formation and fruit set
- Small highly coloured fruit
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Often Confused With
Contact herbicide injury – more severe on lower leaves close to where herbicide was applied
Bacterial spot on peach – no ring around shot-holes on leaves; small, circular sunken lesions on fruit
X-disease – no bacterial oozing; irregular yellow spotting which becomes reddish purple with upward rolling of the leaf at the margins; both healthy and infected symptomatic branches on the same tree
Captan spray injury – lesions are circular and occur mostly on young leaves, many of which may be damaged on only one side of the midvein
Scouting Notes
Terminal shoot growth of less than 20 cm on bearing trees and less than 40 cm on non-bearing trees may indicate a nitrogen deficiency.
Cool growing conditions in early spring often cause plants to develop a temporary nitrogen deficiency. This is usually due to poor growing conditions, and not necessarily a lack of nitrogen in the soil.
Nitrogen deficiency often occurs when a permanent grass is seeded in the orchard or when a large amount of organic matter which is low in nitrogen, such as straw, is worked in to the soil. Deficiency symptoms may also occur particularly in coarse, sandy soils with low organic matter when nitrogen has been leached by heavy rains.
Management notes
All management decisions must be based on tree age, crop levels and prior soil and tissue samples. Tissue sampling must occur at the same stage of tree growth each season as the N levels will fluctuate in the soil and tissue over a growing season. For application rates see nutrient sufficiency ranges for tender fruit.
Photo source: UC Davis Fruit and Nut Research and Information
