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 yield and quality (volume weight, 1000 kernel weight, protein content, falling number, gluten content, gluten index, gluten content in dry matter) of winter wheat was studied in variety 'Portal'. The wheat was part of the five-year crop rotation experiment where red clover (Trifolium pratense L.), winter wheat (Triticum aestivum L.), peas (Pisum sativum L.), potato (Solanum 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 variant, on the background of P25 and K95 kg haE-1 the N amount varied from 0 to 150 kg haE-1 and herbicide Mustang (preparation norm 0.5 L haE-1, active substance florasulam, 6.25 g LE-1; 2.4-D, 300 g LE-1), insecticide Fastac 50 (preparation norm 0.2 L haE-1, active substance 50 g LE-1 alphacypermethrin) fungicide Falcon EC 460 (preparation norm 0.4 L haE-1, active substances 167 g tebuconazole, 250 g spiroxamine, 43 g triadimenol) and growth regulator Moddus (preparation norm 0.4 L haE-1, active substance 250 g LE-1 trinexapac-ethyl) were used. In conversion to organic the winter wheat grains which followed the red clovers after effect had higher volume weight, 1000 kernel weight and gluten index compared to the variants where mineral fertilizers were used. The yield, protein content, falling number and gluten content in dry matter increased with increase of the amount of mineral N. The wet gluten content was significantly higher compared to the other variants where the N amount was 50 kg haE-1.

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.

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.

Wheat crown rot is a harmful disease that can be caused by different pathogens. The control of this disease is complicated because of the diversity of pathogens and an insufficient efficacy of fungicides; therefore, the agronomic practices of wheat production are an important tool for reducing the disease development. The aim of this study was to estimate the incidence of wheat crown rot depending on soil tillage system and on the pre-crop of wheat in the year 2016. The field experiment was carried out at the Research and Study farm ‘Peterlauki’ of the Latvia University of Agriculture in the autumn of 2008. The data obtained in 2016 are analysed in this study: A – soil tillage system: 1 – traditional soil tillage with ploughing at the depth of 22 – 24 cm, 2 – reduced soil tillage with disc harrowing up to the depth of 10 cm; B – pre-crop of winter wheat: 1 – wheat, 2 – oilseed rape, 3 – faba beans. The incidence of crown rot was not influenced by soil tillage system, but the impact of pre-crop was significant (p = 0.006). The level of disease was essentially higher in continuous wheat sowings. The experiments showed that the main causal agents of the disease were Fusarium spp. and Oculimacula spp. The spectrum of pathogens was not dependent on a particular agronomic practice.

The agronomic role of legumes in cropping systems is well understood with the respect to N2 fixation, mechanisms of precrop effects, and environmental impacts. The combined inoculation and tripartite symbiosis between leguminous plants, Rhizobium spp. and vesicular-arbuscular mycorrhizal fungi has been the subject of intensive research. Less attention has been paid to their effects on subsequent crops. Pot experiments were carried out in the greenhouse of Latvia University of Agriculture in 2015 and 2016. Soil used for this experiment was taken from the previous trial, where broad beans (Vicia faba var. major Harz.) were grown. Bean seeds, depending on the variant, were inoculated with rhizobia bacteria or mycorrhiza fungi, or the mixture of both microorganisms. Onions were grown as a subsequent crop. During the experiment, fresh and dry weight of onion leaves was determined. Onion root mycorrhizal colonization frequency and arbuscule abundance in the onion root system were determined. The activity of soil microorganisms was determined by soil respiration intensity. Results showed that the use of microsymbionts increased the subsequent onion leaf harvest in 2014 by 2.3% and in 2015 by 9.5%. In 2015 the highest increase of onion leaf yield was detected in variants were rhizobia strain RP023 was used. Rhizobia strain RV407 gave a positive effect only in combination with mycorrhiza fungi. Precrop treatment with mineral nitrogen fertilizer increased the onion yield in both years – by 12.4 and 14.3%, respectively. In all treatments, a decrease in dry matter content was observed. The highest incidence of mycorrhiza fungi structures was detected under mycorrhiza treatment. Tripartite symbiosis promoted the soil respiration rate.

Wheat (Triticum aestivum) is one of the main crops grown in Latvia. Nitrogen fertilizer is one of the most important factors affecting the acquired yield and its quality. The aim of this paper is to describe the nitrogen fertilization impact on winter wheat yield and yield components under two soil tillage systems and after two forecrops. Field trials were carried out at Research and Study farm ‘Peterlauki’ of Latvia University of Agriculture (56° 30.658°C N and 23° 41.580°C E) in 2014/2015 and 2015/2016. Researched factors were (1) crop rotation (continuous wheat and wheat/oilseed rape (Brassica napus ssp. oleifera), (2) soil tillage (traditional soil tillage with mould-board ploughing at a depth of 22 – 24 cm and reduced soil tillage with disc harrowing at a depth below 10 cm), and (3) nitrogen fertilizer rate (N0 or control, N60, N90, N120(90+30), N150(90+60), N180(90+60+30), N210(90+70+50), and N240(120+60+60). Results showed that the nitrogen fertilization significantly increased winter wheat grain yield after both forecrops and in both soil tillage variants. Grain yield significantly increased until the nitrogen fertilizer rate N180. Nitrogen fertilizer significantly affected all tested yield components. Values of yield components increased enhancing N-rate of N150 – N180. The forecrop had a significant impact on wheat yield and 1000 grain weight (both increased when wheat was sown after oilseed rape). Yield and grain number per ear were significantly higher when conventional tillage was used, but number of ears per square m – when the reduced tillage was used.

Wheat (Triticum) is one of the three most important field crops used for food in the world, as well as in Latvia. The two-factorial trial was conducted at the Research and Study farm ‘Pēterlauki’, Latvia, with the aim to find out the effect of soil tillage and crop rotation on winter wheat grain yield formation. Two soil tillage systems (conventional and reduced), and three crop rotations with different winter wheat (Triticum aestivum) proportion in it (100, 67 and 25%) and different fore-crops (wheat, oilseed rape (Brassica napus ssp. oleifera), faba bean (Vicia faba)) were used. Long-term trial was started in 2009, however, the data from 2016/2017, 2017/2018 and 2018/2019 growing seasons was used for this report. The highest average wheat yield was harvested in 2017 (7.17 t haE−1), and it was significantly (p is less than 0.001) higher than yields in 2018 and 2019 (on average 6.18 t haE−1 and 5.68 t haE−1, respectively). Crop rotation with winter wheat proportion 25%, in which faba bean was wheat fore-crop, showed the highest average grain yield (7.35 t haE−1), but the lowest yield was obtained in rotation with 100% wheat proportion (on average 5.52 t haE−1). Crop rotation scheme had a significant influence on the yield (p is less than 0.001) and 1000 grain weight (p is less than 0.001). Forecrop influenced the yield (p is less than 0.001), number of spikes per 1 square m (p is less than 0.001), and number of grain per spike (p=0.008) significantly. Soil tillage did not affect the studied parameters importantly. Conditions of the trial year affected all parameters significantly.

The most important reason for growing field crops is food consumption. Only some of the total amounts of field crop species are mostly used for cultivation in the largest part of arable land. These crops ensure high economic income. This is the reason why biological diversity has decreased. Crop rotation is considered to be an instrument of sustainable cropping system and this is confirmed again nowadays. Higher cereal yields have been gained by including oil crops or pulses in the rotation. Each field crop has its own calorific value (MJ kgE-1). Grains/seeds and above-ground biomass may have different calorific values because of their chemical composition. Research results from literature confirm that the average net calorific value of winter wheat (Triticum aestivum) and triticale (Triticosecale) grain and straw are ~17 MJ kgE-1, but the net calorific values for oilseed rape (Brassica napus ssp. oleifera) seeds and straw are – 25.70 MJ kgE-1 and 16.37 MJ kgE-1, respectively. Oilseed rape is also known as energy rich crop. It is reported that diversified crop rotations also have greater energetic productivity from above-ground biomass (grain/seed yield and by-products) if compared with crops grown in repeated sowings or in monoculture. Crop rotation in combination with different tillage methods (conventional tillage, reduced or minimum tillage and no-tillage) is the way to improve soil quality, but it is not clear whether the soil treatment method has a significant impact on the overall crop rotational energy productivity.