NITROGEN REMOVAL WITH APPLE--TREE FRUITS.

The investigation was done at the Latvia State Institute of Fruit-Growing in Dobele in 2009, on the basis of an established field experiment planted in 1997 with apple (Malus domestica Borh.) cultivar 'Melba' (rootstock B9) trees spaced at 1.5 x 4 m distances. Three different treatments of soil moisture management were compared: control, sawdust mulch and fertigation. Soil of the experimental plot was Haplic Luvisol (Hypereutric), sandy loam, interspaced with Cutanic Luvisol, sandy loam. Organic matter -- 25 g kg-1, soil reaction pH -- 6.5. Plant available P was 130.9, K -- 157.7, and Mg -- 102.2 mg kg-1. The aim of the investigation was to determine nitrogen removal with fruit yield taking into consideration the used soil moisture regulation method -- sawdust mulch or fertigation. The applied soil moisture regulation methods (mulch and fertigation) had significant influence on the content of dry matter in apple fruits (p<0.05). The highest content of dry matter was found in the control treatment. A significantly higher nitrogen concentration (47 g kg-1) in apple dry matter was in the control treatment, whereas in mulch and fertigation treatments nitrogen concentrations were lower (36 and 42 g kg-1). The highest nitrogen concentration in dry matter was found in fruits with the biggest mass (r=0.61). A negative significant (p<0.05) correlation was found between nitrogen concentration and trunk diameter (r=-0.85), and between nitrogen concentration and yield (r=-0.84). Removal of N was 24.4 kg ha-1 in the control, 22.3 kg ha-1 in the mulch, and 25.0 kg ha-1 in the fertigation treatment. [ABSTRACT FROM AUTHOR]