The objective of the research was to study the removal of nitrogen, phosphorus and potassium with summer-pruned branches of apple-trees grown on dwarfing rootstocks under the influence of applied moisture regulation methods. The investigation was done at the Latvia State Institute of Fruit-Growing in Dobele, on the basis of an existing field experiment planted in 1997 with cultivar 'Melba' (rootstock B9) at 1.5 - 4 m trees spacing distances. Three different treatments of soil moisture management were compared: control (without moisture regime regulation), sawdust mulch and fertigation. Inter-row strips were covered by grass vegetation (Lolium perenne L. and Poa pratensis L., in proportion 1:3). Pruning of apple-trees was done in mid-July. The results of the research showed that the applied soil water regulation treatments (mulch and fertigation) had significant influence (p is less than 0.05) on the apple-tree biomass (leaves, one-year and older wood) removed by summer pruning, as well as on the content of dry matter in biomass. The contents of N and K were influenced both by the treatment and age of tree vegetative parts, but the content of P did not differ significantly among treatments or tree parts (p is greater than 0.05). Removal of N with summer-pruned leaves and branches was 30 kg haE-1 N in the mulch treatment and 16 - 17 kg haE-1 in control and fertigation treatments (p is less than 0.05). Removal of K in the control treatment was 19 kg haE-1, in the mulch treatment 40 kg haE-1, but in the fertigation treatment 27 kg haE-1 (p is less than 0.05). Removal of P varied from 5.04 to 9.84 kg haE-1, no significant differences were found among treatments (p is greater than 0.05).

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 × 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 kgE-1, soil reaction pH – 6.5. Plant available P was 130.9, K – 157.7, and Mg – 102.2 mg kgE-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 is less than 0.05). The highest content of dry matter was found in the control treatment. A significantly higher nitrogen concentration (47 g kgE-1) in apple dry matter was in the control treatment, whereas in mulch and fertigation treatments nitrogen concentrations were lower (36 and 42 g kgE-1). The highest nitrogen concentration in dry matter was found in fruits with the biggest mass (r=0.61). A negative significant (p is less than 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 haE-1 in the control, 22.3 kg haE-1 in the mulch, and 25.0 kg haE-1 in the fertigation treatment.

Potassium (K) is one of the most important nutrients necessary for many life functions of plants, like shoot growth, fruit and flower bud set, and fruit size. The aim of this study was to determine the content of potassium in orchard lawn for reduction of potassium fertilizer application and to include the potassium from mown grass into K balance and turnover calculation. 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 (Mains 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 Pisocalcic Cutanic Luvisol (Hypereutric, Hyposkeletic); loam. Organic matter - 25 g kgE-1, soil reaction pH - 6.5. Plant-available P was 130.9, K - 157.7, and Mg - 102.2 mg kgE-1. Inter-row strips were covered with grass vegetation (Lolium perenne L. and Poa pratensis L.). Grass samples were collected during cutting, 3 times per season of 2009: May 19, June 20, and August 11. The uptake and removal of potassium was calculated as kilograms per hectare area. The concentration of potassium in the lawn and the height of grass growth were significantly influenced by the mowing time and the soil moisture treatment. These results can be a base for further studies of potassium turnover in an orchard, as well as for fertilizer planning and management.