Trickle Irrigation of Apple Trees and the Effects of Liquid Feeding with NO3−and K+Compared with Normal Manuring

Abstract

SummaryIn three orchards under trickle irrigation, where different types of nozzle were in use, wetting patterns were similar, as relatively deep, narrow cones. Roots adapted to the pattern of water spread and root fibre (< 1 mm diam.) were increased four to five times below 30 cm depth near the wet core under the trickle nozzle than in an equivalent unirrigated zone. In the absence of irrigation the greatest concentration of roots was in the surface 30 cm of soil. Fertilizer K and N were fed at two rates to the trees in one orchard, either as granules spread uniformly over the ground or in solution delivered into the puddle area under the trickle nozzles. The granular fertilizer was applied once annually and the liquid feeds were dispensed in equal monthly, fortnightly or weekly amounts from May to September. NO3− concentration built up 30–60 cm from the trickle nozzle, beyond the area of visible wetting. K+ was mainly increased in the puddle region which extended to 15 cm from the nozzle. The lateral spread of NO3− and K+ appeared to be as great as the discernible spread downwards. Trees receiving the higher N rate had the higher leaf N, except those receiving weekly liquid feed for which the reverse was true. Leaf K varied with the frequency but not with the rate of application. The annual and monthly applications led to a lower leaf K in cv Worcester Pearmain than more frequent ones, but in cv Egremont Russet only the annual application led to a significantly lower concentration of leaf K than the other frequencies. Polar transport of nutrients from the trickle-irrigated zones on the E and W sides of the trees to the foliage on the same sides appeared to explain the significantly greater number of trees with higher contents of P, Ca and Mg in June; N, P and Ca in July; and P in August in their E and W rather than their N and S foliage. The effect seemed entirely associated with the localized irrigation because there were no apparent differences between the nutritional treatments. Leaf nutrient concentration did not show the same consistent pattern as leaf nutrient content. Treatments did not affect tree growth differently, and in only one year was cropping increased by monthly liquid feed given at both rates of supply. The storage quality of Egremont Russet fruit was improved by the monthly and fortnightly liquid feed treatments compared with normal manuring.