Influence of rootstock and irrigation methods on water use, mineral nutrition, growth, fruit yield, and quality in 'Gala' apple

Abstract

The increasing trend in the world population and decreasing trend in the suitable land for fruit production, combined with a shortage of water, mandate the use of efficient methods of irrigation and establishment of high-density orchards that require size-controlling rootstocks. Method of irrigation and vigor of rootstock are among the most important factors affecting uptake of mineral nutrients, and thus tree growth and fruit yield and quality attributes of apple (Malus domestica). In a long-term experiment, effects of two irrigation methods and four rootstocks on water use, tree growth, fruit quality, and leaf mineral nutrients were studied in 'Pacific Gala' apple. The experiment was conducted in southwestern Idaho, which represents the high desert conditions of the Intermountain West region of the United States. Evapotranspiration-based irrigation scheduling (ETc), adjusted by percentage of ground shading, was used for sprinkler and drip systems. Significantly lower volume of water was applied to the trees with drip irrigation than those with sprinkler irrigation system. Leaf calcium (Ca) decreased but leaf potassium (K) increased with rootstock vigor, resulting in the greatest leaf Ca but lowest leaf K in trees on 'Budagovsky 9' (B.9). Fruit weight and yield per tree in 'Pacific Gala' on 'Nic 29' (RN29) rootstock was higher than those on B.9 and 'Geneva 30' (G.30) rootstocks. 'Pacific Gala' on B.9 rootstock had smaller trees and fruit size but higher fruit starch degradation pattern (SDP), suggesting earlier fruit maturity on this rootstock. On average, 'Pacific Gala' trees with drip irrigation had larger fruit and higher leaf magnesium (Mg) and manganese (Mn) but less fruit color and firmness and lower leaf Ca, K, zinc (Zn), and copper (Cu) than those with sprinkler system.