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 researches were carried out from 2002-2007 in the upper reaches of the Šušvė River, a Nevėžis tributary, at the pig enterprise Limited company (LTD) 'Litpirma' breeding near the township of Šiaulėnai. LTD 'Litpirma' has been operating since 1978 and produces 25 thousand fattening pigs per year, along with an associated 56 thousand m3 organic fertilizers (liquid manure, slurry and solid manure), which are spread on surrounding agricultural fields. This article presents the impact of a large pig breeding company on the river water quality and quantifies the leaching of nitrogen, phosphorus and potassium (NPK). It is based on the water quality research data collected from an 11.6 km section of the Šušvė River, both upstream and downstream of Šiaulėnai, regarding the drainage water outflow from the fertilized fields and from Šiaulėnai domestic wastewater. Drainage water from 728 ha of fields that have been fertilized with organic fertilizers carry an average of 11.4 tons of nitrogen, 0.073 tons of phosphorus and 5.53 tons of potassium. Changes in NPK quantities carried by this section of the Šušvė were calculated as follows: total nitrogen increased by an average of 83 tons yrE–1 (58%), potassium by 51 tons yrE-1 (54%) and the smallest increase, for total phosphorus, by 1.2 tons yrE-1 (48%). All of these pollutants leached into the river during the cold season (to 60% total phosphorus and to 88% total nitrogen) when there was no vegetative growth. A wet year affects the quantities of leached NPK.

Abstract Studies comparing slurry injection versus spreading have reported inconsistent results so far. The objective of the study was to compare two slurry application methods, injecting and spreading, in terms of influence on sward yields and leaching of nitrogen (N) and potassium (K) from grassland. The experiment was conducted from 2008 to 2011 at the Eerika Experimental Station, Estonian University of Life Sciences. Mini-lysimeters filled with loamy sand soil embedded in three swards (three-species grass mixture (Phleum pratense, Lolium perenne and Poa pratensis), grasses mixture with white clover (Trifolium repens), and grasses mixture with lucerne (Medicago sativa)) were used. Three annual nitrogen rates (60, 120, 180 kg haE-1) in conjunction with the two slurry application methods (injecting and spreading) were applied. Percolated water quantities, N and K content in leachate and the sward yield were measured. N leaching was significantly less with slurry injection while K leaching did not depend on slurry application method. N and K leaching was more affected by sward botanical composition and applied N rate and N:K ratio n slurry than by slurry application method. Sward yields did not depend significantly on slurry application method. Slurry injection is rational only in grasses sward when used N rates are above 120 kg haE-1 yrE-1. Slurry injection may have negative influence on the distribution of white clover in the grasses + white clover sward and thus lead to sward yield decrease.

The yield and quality (1000 kernel weight, protein, nitrogen, phosphorus and potassium content) of peas was studied in cultivar 'Madonna'. The peas (Pisum Sativum L.) were part of the five-year crop rotation experiment where red clover (Trifolium pratense L.), winter wheat (Triticum aestivum L.), peas, potato (Solarium tuberosum L.) and barley (Hordeum vulgare L.), were following each other. There were two production variants which followed the crop rotation. In one variant mineral fertilizers and pesticides were used, and the other variant was conversion to organic without any synthetic agrochemicals. In mineral fertilizing variants the background in all variants was N20, P25, and K95 kg haE-1. The previous crop was winter wheat which received in fertilized variants mineral fertilizers with the background of P25 and K95 kg haE-1, the N amount varied from 0 to 150 kg haE-1. The aim of this paper was to study a mineral fertilizing after-effect on the peas which followed the winter wheat. Herbicide MCPA 750 was used. In conversion to organic, the pea grains which followed the crop rotation and mineral fertilizing Nl50 after-effect variants had higher yield, protein and nitrogen content compared to the other variants where mineral fertilizing after-effect was investigated. Phosphorus contents were higher in NO, and conversion to organic variants. Potassium content remained lower in Nl00, and Nl50 mineral fertilizing after-effect variants. The 1000 kernel weight was significantly higher in the variant of conversion to organic compared to the other variants.

In this article, the results of research on WRI of LUA Juodkiškiai experiment field (1999 – 2003) are discussed. Fertilization and other factors influence over potassium fluctuation, its balance and leaching into drainage water during crop rotation are analysed. In order to evaluate the potassium balance and its quantity passed together with rainfall, seeds, fertilizers and take with the yield (secondary and primary production) was established in plant residues and drainage water. When fertilizing with liquid manure, potassium balance was negative while growing perennial grasses as much potassium was needed to mature their yield. The investigations established that potassium concentration in drainage water and its leaching was increased by precipitation during the research period, and it was reduced by the amount of this element taking out with yield. Soil geochemical environment had influence on the increase of potassium supply in soil. It was established that long-term fertilization with liquid manure had raised the potassium supply in soil. However, from an ecological point of view, potassium leaching did not cause any problems. In all treatments the potassium concentration in drainage water did not exceed permissible concentration.

Blueberry cultivation is becoming more and more popular in Latvia, and several commercial plantations have been established recently. Highbush blueberries (Vaccinium corymbosum L.) are perennial and can grow without replanting for 50 years; therefore a choice of soil and its preparation have a great role. This article summarizes results of research carried out in commercial blueberry plantation established in 2004 on loamy Haplic Cambisol. Soil properties, especially reaction and organic matter content, initially were not suitable for blueberry cultivation, therefore deep tillage and application of soil conditioner (acid sphagnum peat) were done before planting and similar peat mulch was applied every second year. Berry yield of 4 blueberry cultivars, soil properties and the nitrogen, phosphorous and potassium content in growing plant leaves were determined. The obtained results showed that sphagnum peat is an effective material for lowering of soil pH in plant root layer (0 – 40 cm). Data about plant nutrient content in topsoil and subsoil as well as in growing plant leaves will help to develop criteria for soil fertility assessment and diagnosis of plant nutrition.

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.

Human milk provides infant with the required nutrients for growth and development. The aim of preliminary study was to determine macro- and micronutrients content in mature human milk among lactating women residing in Latvia and dietary habits affecting it. The study was carried out from November 2016 to February 2017. In total, 24 pooled diurnal milk samples were collected from mothers whose infants had reached the age of at least two months. Personal information of each participant was recorded, including mother’s age, weight and height parameters, sex and age of an infant, parity, breastfeeding pattern, milk expression method used for sampling. Eating habits were obtained using Monthly Food Frequency Questionnaire. Analysed elements were determined using inductively coupled plasma mass spectrometry (ICP‑MS Agilent 7700x, Japan). Concentrations ranged from 227.52 to 398.34 mg LE-1 for calcium, 58.56 – 256.38 mg LE-1 for sodium, 445.33 – 736.71 mg LE-1 for potassium, 25.73 – 49.52 mg LE-1 for magnesium, till 3.17 mg LE-1 for iron, 0.28 – 2.77 mg LE-1 for zinc, 0.06 – 0.43 mg LE-1 for copper, 2.00 – 44.00 µg LE-1 for manganese, 1.00 –10.00 µg LE-1 for chrome which is comparable to data obtained from other studies although chrome and manganese concentration was even higher than observed in literature. Cobalt and selenium content was below detection limit. Zinc content in human milk negatively correlated with baby’s age (p is less than 0.05). The content of majority of essential minerals in human milk was affected by mother’s dietary habits; however, more samples need to be analysed for representative conclusions.

New types of polymer fertilizer series ‘Vitanoll’ are used in adaptive-varietal agro technology in the cultivation of seed potatoes. The experiments were conducted on sod-podzolic soils, typical of the North-West region of the Russian Federation. The aim of the research was to study the effect of new polymer fertilizers on potato yield. Research tasks included assessing the effect of various polymer fertilizers (Polymer-N, Polymer-P, Polymer-K.), as well as the effect of Polymer-N on different potato varieties. Based on the studies conducted, the most responsive potato varieties to polymeric fertilizers with nitrogen were identified. They turned out to be Salin (increase of 7.1 t haE−1) and Mocart (increase of 4.1 t haE−1). Evaluation of the influence of different types of polymer fertilizers revealed that the most effective are polymer fertilizers with potassium.

The mean content of minerals in grains varies significantly among different parts of the world as it depends on the type of grain growing conditions and fertilizer application. In this study, the content of minerals in the wheat, oat and barley grains of the crop of the year 2006 from different regions of Latvia were investigated. The grain samples were analysed for K, Mg, Ca, Na, Cu, Mn, Fe, and Zn using Atomic Absorbtion Spectrometer, and for P using spectrophotometer. Phosphorus content in different types of grains varied from 3.10 to 5.65 g kgE-1, potassium - from 4.37 to 6.10 g kgE-1, calcium - from 0.40 to 1.40 g kgE-1, magnesium - from 1.20 to 1.68 g kgE-1, manganese – from 14.50 to 55.54 g kgE-1, copper - from 3.35 to 6.01 g kgE-1, zinc - from 18.72 to 31.84 g kgE-1, iron - from 42.39 to 120.40 g kgE-1, and sodium - from 32.34 to 55.52 g kgE-1. The greatest difference was found between the content of manganese and iron in barley, wheat and oat grains, but small difference was between the mean content of P, K, Zn, Cu, Mg, and Na.