Eight-year (2000-2007) field studies on the effectiveness of controlled drainage in loam sandy soil were carried out in the Lowland of Middle Lithuania. The plot, which has existing subsurface water removal systems operated as conventional drainage was readjusted for the water table management. Two separate systems - 4.9 hectares free drainage (FD) and 5.4 hectares controlled drainage (CD) were arranged. A water level control structure with a riser column and hand operated rigid flap door was installed in the outlet of drainage collector in the manhole at the junction of two collectors. The water table level was allowed to rise to the maximum of 68 cm above the drains. Measurements to record the water table depth, drain outflow quantity and quality were performed. It was determined that in the CD system the annual drainage outflow lasted shorter by 40-62%, at the same time it was reduced by 25% and nitrate leaching - by 20-28% lower in comparison with the drainage operating in an ordinary regime. These indicators varied depending on weather conditions. The water table control in single-acting drainage systems is feasible and has a positive hydrological and environmental impact.

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.

The article analyses the seasonal nitrogen variation in drainage water, when the plants in the field crop rotation are fertilized with slurry during different seasons. The investigations were carried out in 2001-2003 in Juodkiškis experimental site of the Lithuanian Water Management Institute. The investigations established that the largest amounts of nitrogen are leached out in spring and in winter. In the autumn fertilized variant 38.8% more of this element was leached out in winter and spring compared with the variant fertilized in spring. During autumn nitrogen leaching was also 21% higher from the variant fertilized in autumn. It was established that the fertilization rate and dissolved inorganic nitrogen (DIN) supply in soil have influence on the concentrations of this element. During the cold season nitrogen concentrations in drainage water, when plants had been fertilized with slurry in spring, were more affected by the supply of dissolved inorganic nitrogen in soil more compared with the rate of fertilization; and if fertilization had been performed in autumn - the concentrations were more affected by the fertilization rate. In warm season both the fertilization rate and the supply of dissolved inorganic nitrogen in soil had similar influence on the concentrations of nitrogen in the drainage water in both treatments. Meteorological conditions affect nitrogen leaching a lot. During the cold season a greater amount of nitrogen is leached out when the air temperature is higher and during the warm season - when more precipitation falls.

A current investigation compared various intensive crop rotations (Norfolk, row crops, cereals, short term grass) grown on Cambisols. The study results showed significant effects of N-fertilization of the agroecosystem on mineral N concentration in drainage water and its leaching process. The highest N concentration in drainage water and leaching was determined in the conditions of cereals and row crops rotations. No major impact of the crop rotation on phosphates concentration in drainage water was determined. The average leaching of one by drainage did not exceed 100-140 g haE-1 within a 7 year study period. An experiment was arranged during 1997-2003 years in the Kėdainiai district, Lipliunai willage. A rational and well-considered fertilization ensures high crop productivity and profitable farming as well as steady, which is the main condition for reduced non-point source pollution of water.

The paper presents data on the water quality in drainage from manure-fertilized areas in a large livestock company (629 conditional livestock) from 2008 to 2012. The scheme of investigation consists of two field variants: manure fertilized and non-fertilized. Researches are carried out in drained areas, where the drainage water is drained away through outlets. The nitrogen rate 170 kg haE-1 is used annually to fertilize fields in spring. The aim of the research was to ascertain the impact of large livestock company fields fertilized annually with manure on the water quality in drainage. For the purpose of chemical investigations, water samples from drainage were taken once per month. Water analyses were carried out by the accredited Chemical Analytical Laboratory of the Water Management Engineering Institute of Aleksandras Stulginskis University according to specified methods. Investigation results have demonstrated that fields fertilized annually with manure raised the contents of Nmin and P2O5 in the soil by 1.5 and 2.2 times respectively in comparison to the non-fertilized ones. The increase in these contents was conditioned by the higher air temperature and the lower rainfall. The seasonality of Ntotal concentrations in drainage water was discovered: higher concentrations were identified in autumn and winter, lower concentrations – in spring and summer. Due to low dissolubility in the soil, low Ptotal concentrations were identified in drainage water. The highest concentrations were identified with the start of drainage operation.

The research was conducted during the period of 2007-2011 in the fields fertilized by manure of pig breeding complex. According to the fertilization value of manure, the following total nitrogen levels reached the fields each year: 2007 – 169, 2008 – 167, 2009 - 168, 2010 - 168, 2011 – 168 kg haE-1. Ptotal reached the fertilized fields accordingly: 2007 – 9.4, 2008 – 18.9, 2009 – 12.0, 2010 – 10.8, 2011 – 13.5 kg haE-1. The aim of the research was to explore the impact of manure fertilized fields of a pig breeding complex on the water quality of streams. Streams, flowing through fields fertilized with manure, are usually polluted with nitrogen. The increase in Ntotal concentrations in streams’ water below fertilized fields was affected by precipitation (r = -0.31), fertilization rate (r = 0.41) as well as mineral nitrogen reserves in the soil (r = 0.20). Phosphorus concentrations in streams’ water were low and corresponded to a very good streams’ water ecological condition, except in times, when the water inflowing into the fertilized fields was already contaminated with this element. It was determined that an extremely high impact on streams’ water quality below fertilized fields comes from Ptotal concentration in streams’ water above fertilized fields (r = 0.91) as well as from the drainage water inflowing from fertilized fields into the streams (r = 0.71). Neither Ntotal, nor Ptotal pollution was observed in drainage water, because the highest concentrations during the research period were lower than the maximum allowable concentrations by 1.1 and 6.5 times respectively.

The investigations were carried out in the Lithuanian Agricultural University Water Research Institute land plots in the Endocalcari Endohypogleyic Cambisols (CMg-n-w-can). The basis of the investigation is 3 variants field experiment. Each variant consists of 3 in 0.54 ha drainage. The traditional arable farming is applied in variant I. In the variant II the land is not being cultivated, but in spring the perennial ryegrass (‘Lolium perenne L’) is being seeded into the spring barley and kept till spring. In the variant III the land is not being cultivated after the harvest and left for the rest till spring. The variant II is distinguished by the minimal mineral nitrogen content. Applied to cultivated and uncultivated land, the min N reserves are increased 51 - 83 and 33 - 40 and 11 - 101 and (38 - 134%) (to 9.5 - 14.3 mg kgE-1 and 152 - 68 and 154 - 61 kg haE-1). The average investigation of N concentration in the drainage water shows, that the minimum concentration of this element was in the second variant. Applied to the traditional farming and uncultivated land, the N concentration is increased by (30 - 42% to 34 and 37 mg lE-1). By average data the min N, leaching by drainage water in the variant II was minimal and about 27 kg haE-1. Applied to the arable farming and uncultivated land, the min N leching is increased (30 - 55%) (to 35 - 42 kg haE-1).

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.

The investigations were carried out during the period 2006-2011 in the land of the Water resources management institute of ASU, in the village of Lipliūnai on Endocalcari Endohypogleyic Cambisol (CMg-n-w-can). The base of investigations is 3 drainage systems, which contain cereals differing in fertilization and grass crop rotations. The aim of investigations is to determine the crop rotations differing in fertilization and these relations with cycles of phosphorus in agroecosystem. Higher productive was perennial grass crop rotation. In the conditions of cereal crop rotations this productive was 3-46% lesser. The highest concentration of P-PO4 3- in drainage water was received in the conditions of higher fertilization cereals crop rotation while highest concentration of total P was in the conditions of grass crop rotation. The concentration of P-PO4 3- in drainage water essentially depends on amount of mobile P2 O5 in soil, fertilization, productivity of field crops, drainage runoff as well as cumulative balance of P. The highest leaching of P-PO4 3- and total P by drainage was received under the conditions of higher fertilization cereals crop rotation. The leaching of P-PO4 3- essentially depends on fertilization, drainage runoff as well as cumulative and yearly balance of P. The application of all crop rotations was distinguished by positive P balance.

The research was carried out on ASU WRI grounds in Juodkiškes village in Endocalcari Endohypogleyic Cambisol (CMg-n-w-can). Research basis is 3 different field studies. In Variant I an organic cropping system was used with manure and without mineral fertilizers and pesticides, in II - organic-mineral cropping system with manure and mineral fertilizers, using pesticides, in Variant III - mineral cropping system with mineral fertilizers and pesticides. Minimum mineral nitrogen content in soil was in the organic cropping system, and the total minimal field crop capacity - in the mineral cropping system. However, it has the highest energy efficiency of this system (ETK - 13). Minimal N-NO3 - concentration in drainage water was in the mineral cropping system. In the organic-mineral and organic cropping systems concentration of this compound increases by 11 percent (to 21.8 mg l-1). The minimal concentration of ammonia nitrogen was under organic cropping conditions. The organic cropping system showed the highest runoff and maximum leaching of nitrogen compounds by drainage.