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Changes in water requirement, yield, and quality under various irrigation and nitrogen levels in 'Fuji' apples

Fallahi, E., Fallahi, B.
Acta horticulturae 2017 no.1177 pp. 301-306
Malus domestica, apples, canopy, color, crop coefficient, evapotranspiration, fruit quality, irrigation rates, irrigation scheduling, irrigation water, leaves, nitrogen, root zone drying, sprinklers, trees, water requirement
The use of crop evapotranspiration (ETc), when the crop coefficient (Kc) was modified by percentage of ground shade (GS) and tree canopy maturity (M) provided a reliable irrigation scheduling tool for determining water requirement for apple trees. In an experiment with ET based irrigation scheduling, 'Autumn Rose Fuji' trees with a micro-jet sprinkler system received an average of 6,462 L (994 mm) while trees with a drip system used 3,996 L (614.1 mm) of irrigation water. Using micro-jet sprinklers to impose a partial root zone drying regime reduced fruit size but slightly improved fruit color in 'Autumn Rose Fuji'. Deficit drip applied to both sides of a tree (DD, 65% of full drip or FD) increased yield initially, but had lower yield when the treatment was repeatedly applied. When the 65% of FD rate was applied to only one of the alternating sides of the tree every other week, fruit size was larger than those with DD treatment. Leaf nitrogen (N) at about 2.2% (dwt.) and fruit N at 0.24% was achieved when 40 g N tree-1 was applied and these levels increased fruit quality in 'Fuji'. A well-calculated ETc-based FD system is recommended over other irrigation regimes, although trees can be maintained at lower irrigation rates.