The 2009 ASHS Annual Conference

Keywords: fruit quality, irrigation efficiency
An increasing trend in water shortage and needs for high density orchards mandate the use of more efficient methods of irrigation and rootstocks.  Also, more information is needed on the relationship between irrigation and nutrient inputs in order to target nutrient applications to meet plant demands. In this long-term experiment, effects of seven irrigation systems for 'Fuji' on RN 29 rootstock  and two irrigation systems for 'Gala' on four rootstocks on tree growth, water use, fruit quality and mineral nutrients were studied.  Soil solution was collected from permanently installed suction lysimeters and NO3-N concentration in part of our experiment with ‘Gala apple on M9 rootstock on a silt loam soil.  All forms of drip systems used less water than full micro-sprinkler (SP). Partial root drying sprinkler (PS) used 50% less water than SP. Trees with partial root drying drip and deficit drip received 65% of full drip. The amount of water used in July was higher than all other months.  When trees were completely mature, each tree with SP system used about 6673 L while that with Full Drip (FD) used 4118 L per season, which was equivalent to 1010 mm and 624 mm, respectively.  Thus, FD resulted in as low as 38.3% and as high as 58.3% saving in water over sprinkler system.  ‘Fuji’ yield and quality, particularly starch degradation pattern (SDP) and size were affected by irrigation treatments. ‘Fuji’ trees with water deficiency had lower leaf and fruit K.  ‘Pacific Gala’ on B.9 rootstock had more bourse shoots with fruit than those on other rootstocks. ‘Pacific Gala’ trees on B.9 ceased its terminal growth and formed its terminal buds about one once before the trees on other rootstocks. ‘Pacific Gala’ fruits from trees on G.30 and B.9 had higher (SDP) than those on RN-29 and Supporter 4.  ‘Pacific Gala’ on G.30 had more fruit cracks than those on any of the other rootstocks.  ‘Pacific Gala’ on B.9 had higher leaf N, than those on Supporter 4 and G.30. Trees on B.9 had lower leaf K than those on other rootstocks. In contrast, trees on B.9 and RN-29 had higher leaf Mg and trees on B.9 had higher leaf Ca than those on the other rootstocks.Nitrate -N concentration in the soil solution measured at 30cm depth, beneath the drip emitter, increased rapidly with the onset of fertigation and decreased rapidly when fertigation ended in Gala/M9. Concentrations remained relatively constant during the intervening period and were directly proportional to either the amount of N or the amount of irrigation water added. The relationships between various irrigation regimes on growth, overall fruit quality attributes, yields, and mineral nutrients fetigation and partitioning will be discussed in more detail.