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Maintaining and increasing the stock of soil organic carbon is of vital importance in maintaining the soil fertility. In present research the changes in the content of organic carbon (SOC) and total nitrogen (Ntot) in the soil are investigated. The data is collected from the long-term field experiment, which compares organic and conventional farming systems in a crop rotation (barley undersown with red clover, red clover, winter wheat, pea, potato) during 2014-2018. Based on the 5-year experiment, it was concluded that the cropping systems have a significant effect on the SOC content and a smaller effect on the Ntot content of the soil. The diversification of organic cropping systems with cover crops and composted cattle manure significantly increases the content of organic carbon in the soil. The results of the experiment indicate that the content of organic carbon was significantly lower (by 7.6-12.6%) in conventional systems, where pesticides had been applied and cover crops and manure had not been used, compared to the organic cropping systems. The correlations between the SOC contents of main crops and precrops were statistically more significant in organic farming system, compared to the conventional system. Highest SOC and Ntot values were observed in organic systems with cover crops and composted manure fertilization. Hence, it can be stated that in order to improve the soil fertility and fix more carbon and nitrogen, high amounts of organic material should be applied into the soil and the activity of soil microbes should be a priority. The organic cropping systems have more advantages for sustainable crop production. [ABSTRACT FROM AUTHOR]

Rhizoctonia disease in potato is widely distributed in Estonia. Field experiments with cv. 'Red Fantasy' were undertaken with seven pre-crop treatments at the Estonian Research Institute of Agriculture in 2009 and 2010. Monocropped potato, spring barley, spring barley underseeded with red clover, spring wheat, grain pea, spring oil seed rape and oil seed radish were involved in the study as pre-crops. Growing conditions on both years were rather optimal for potato growth but year 2010 was drier at early bulking stage. The effect of different pre-crops on Rhizoctonia solani complex was studied (i.e. incidence and severity of stem and stolon canker and black scurf) at 15, 30, 45, 60, 90 and 120 days after planting. Results indicated that pathogenfree seed tubers are of primary importance in the disease control and no pre-crop was suppressive to disease if seed tubers had sufficient amount of inoculum. However, to achieve consistent reduction in disease development, inoculum-free seed tubers and crop rotation with non-host crops should be considered. [ABSTRACT FROM AUTHOR]

In 2008 an experiment was set up on the field in Eerika experimental station (Estonian University of Life Sciences) as a 5-field crop rotation: red clover, winter wheat, pea, potato and barley undersown with red clover. The objective of the study was to measure the content of weed seeds in the soil and to evaluate the diversity of the species at the end of the period of converting to organic production. In conventional farming systems without fertilizer (Conv I) and conventional farming with mineral fertilizer (Conv II) herbicides were used for weed control. All the crops in Conv II system received P 25 kg ha-1 and K 95 kg ha-1, but the application rates of mineral nitrogen fertilizer differed. In organic systems (Org I - organic farming based on winter cover crop and Org II - organic farming based on winter cover crop and manure), the winter cover crops (ryegrass after winter wheat, winter oilseed rape after pea, winter rye after potato) were sown after the harvest and were ploughed into the soil as green manure in spring. The content of annual weed seeds was the lowest in red clover that had 17.7% less weed seeds in the soil of Org II system compared to control (Conv I). In winter wheat the content of winter annual weed seeds was 50-76% higher compared to other crops. By the end of 2009 the content of organic carbon (Corg %) in the soil had increased significantly in both organic systems which results in higher activity of organisms that decrease the viability of weed seeds. [ABSTRACT FROM AUTHOR]

Field trials with two potato varieties were undertaken at the Estonian Research Institute of Agriculture in 2005 and 2006. Year 2005 was generally optimal for potato growth but year 2006 was dry and very warm, hence, it was adverse for growth. The effect of fertilizing on two main traits of potato, i. e. tuber dry matter (DM) and nitrate content was examined. Five rates of compound fertilizer were applied, N50P20K85, N70P28K119, N90P36K153, N110P44K187 and N130P52K221. Results indicated that DM content was largely determined by variety but it also depended on fertilizer amounts and particular environmental conditions of a year. Nitrate content of tubers was quite clearly dependent upon variety, but growing season had significant effect on final nitrate content in tubers. Water stress during early and main bulking periods resulted in high tuber nitrate levels. In order to gain tuber yield fit for intended use, it is necessary to manage nutrient acquisition based on expected yield and nutrient supply from soils. [ABSTRACT FROM AUTHOR]

The effect of time of sowing on oil and meal quality of winter oilseed rape (Brassica napus L. cv. Express) was investigated at the Institute of Agricultural and Environmental Sciences of the Estonian University of Life Sciences in the period of 2001-2005. The rape seeds were sown at weekly intervals on four different dates: 8th, 15th, 22nd and 29th of August. The study shows that sowing date and environmental conditions affect the seed quality of winter oilseed rape. Early sown oilseed rape plants were more adapted to stressful conditions associated with high or low temperatures. The seeds of such plants had higher oil concentration (up to 50.2%) and a lower protein concentration (approximately 19%). Plants sown in late August were less tolerant to stressful conditions and their seed oil concentration was lower (47-48% DM). Oil and protein yield were higher in the early sown crops because the seed yield was higher. Also the glucosinolate (GSL) concentration of the seeds was affected by the time of sowing and weather conditions. Shortage of rainfall before harvest increased the GSL concentration in the seeds. Plants sown in late August did not tolerate the extreme environmental conditions and their seed glucosinolate concentration appeared to increase. [ABSTRACT FROM AUTHOR]

Field trials with the potato cultivars 'Ants' (medium late) and 'Laura' (medium early) were carried out on the experimental fields of the Department of Field Crops and Grassland Husbandry located at Eerika (58°22' N, 26°40' E), Estonian University of Life Sciences in 2010 and 2011. The yield of tubers and starch, marketable yield of potato, number of tubers per plant and tuber weight were studied. We used the following treatments: untreated control (To): seed tubers were planted directly from storage house (storage temperature 4°C); thermal shock (TS): seed tubers were kept before planting 5 days in a room with temperature of 30°C and 2 days with temperature of 12°C; pre-sprouting (PS): before planting the seed tubers were kept 26 days in a room with temperature of 15°C and 10 days with temperature of 12°C. The results are presented as the averages of studied years. According to the average results of two experimental years, the pre-planting treatment with thermal shock increased the number of tubers per plant of cultivar 'Ants' by 30.6%, compared to control treatment. None of the treatments had any effect on the number of tubers of cultivar 'Laura'. The thermal treatment increased the average weight of tubers of cultivar 'Laura' compared to the control treatment (thermal shock by 14.7%, pre-sprouting by 20.7%), but for cultivar 'Ants' the weight of tubers was decreased by 16.7% (thermal shock treatment). The thermal shock treatment increased the tuber yield of cultivar 'Ants' by 10.7% and the presprouting increased the total tuber yield of cultivar 'Laura' by 9.9%. The thermal shock increased significantly the starch content of cultivar 'Ants' and decreased that of cultivar 'Laura'. [ABSTRACT FROM AUTHOR]