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A Thesis for applying for the degree of Doctor of Philosophy in Agriculture. Väitekiri filosoofiadoktori kraadi taotlemiseks põllumajanduse erialal. The long - term effect of organic and mineral nitrogen fertilizers on soil fertility in five - field crop rotation and on the quality of winter wheat grain yield and dough was studied in the doctoral thesis. The aim was to find out the long-term effect of organic and conventional cropping on total yield, soil fertility (phosphorus and potassium content, pH) and the combined effect of different cropping systems and year on the size distribution of starch granules, the yield of whole grain and fine flour, the interaction of gluten-starch on the rheological properties of wheat dough. The total yield of the five-field crop rotation was on average 25% higher than in organic farming due to mineral fertilizers. During the 10-year experimental period, the soil P content of the conventional treatments did not change, while the K content decreased to 40 mg K per kg dry soil and the soil became more acidic. The use of winter crops and well-composted cattle manure did not maintain the basic levels of P and K in the soil, which is why it is important to monitor the nutrient balance, especially in organic farming, so that soil fertility does not decrease. The effect of the cropping system on the size of the starch grains was not significant, but it was affected by the weather conditions during the experimental years. Flour yield was affected by the size distribution of starch granules, while the increased proportion of smaller diameter granules significantly increased the yield of fine flour. The quality of the dough was affected by several factors, with the nitrogen fertilization regime having a significant effect. If the protein content is more than 13% and the glutenin-gliadin ratio is optimal, the dough has a longer stability time, a lower softening degree and a higher dough quality. The quality of the dough varied more in the organic treatments. The amount of 150 kg/ha of mineral N applied in two parts before flowering ensured stable plant growth and protein and gluten content in different years. Treatments fertilized with lower amounts of nitrogen and organic treatments were more vulnerable to changing weather conditions. Doktoritöös uuriti orgaaniliste ja mineraalsete lämmastikväetiste pikaajalist mõju mulla viljakusele viieväljalises külvikorras ning talinisu terasaagi ja nisutaina kvaliteedile. Eesmärk oli välja selgitada mahe- ja tavaviljeluse pikaajaline mõju külvikorra kogusaagile, mulla viljakusele (fosfori- ja kaaliumisisaldusele, pH) ning eri viljelusviiside ja aasta koosmõju tärklise graanulite suuruse jaotusele, täistera ja peenjahu saagile, gluteeni-tärklise koostoimele nisutaina reoloogilistele omadustele. Tulemustest selgus, et viieväljalise külvikorra kogusaak oli mineraalväetiste toimel keskmiselt 25% kõrgem kui maheviljeluses. Kümneaastase katseperioodi jooksul tavaviljeluse variantide mullas ei muutunud taimele kättesaadava P sisaldus, samas K sisaldus vähenes kuni 40 mg K kg kuiva mulla kohta ning muld muutus happelisemaks. Talivahekultuuride ja hästi komposteerunud veisesõnniku kasutamine ei säilitanud mullas P ja K baastasemeid, mistõttu on oluline eriti maheviljeluses jälgida toitainete bilanssi, et mullaviljakus ei langeks. Viljelusviisi mõju tärkliseterade suurusele ei olnud märkimisväärne, küll aga mõjutasid seda usutaval määral ilmastikutingimused katseaastatel. Jahu saagikust mõjutas tärklise graanulite suuruse jaotus, samas kui väiksema läbimõõduga graanulite suurenenud osakaal suurendas oluliselt peene jahu saagikust. Taina kvaliteeti mõjutasid mitmed tegurid, kusjuures lämmastiku väetamise režiimil oli määrav mõju. Kui proteiinisisaldus on üle 13% ning gluteniini-gliadiini suhe on optimaalne, siis on taina stabiilsusaeg on pikem, pehmenemise tase madalam ja taina kvaliteet kõrgem. Taina kvaliteet varieerus enam mahevariantides. Mineraalse lämmastiku 150 kg/ha kogus, mida anti kahes jaos enne õitsemist, tagas taimede stabiilse kasvu ning valgu- ja gluteenisisalduse erinevatel aastatel. Väiksemate lämmastiku kogustega väetatud variandid ning mahevariandid olid muutuvate ilmastikutingimuste suhtes tundlikumad. Publication of this thesis is supported by the Estonian University of Life Sciences.

Nitrogen accumulates in soils during the process of fertilizer addition to promote the plant growth. When the organic matter decomposes, the form of available nitrogen produced is in the form of nitrate, which is highly mobile. The most significant health effect of nitrate ingestion is methemoglobinemia in infants under six months of age (blue baby syndrome). The mobile nutrients, like nitrate nitrogen, are not stored in the soil as the available forms for the long periods and in large amounts. It depends on the needs for the crops such as vegetables. On the other hand, the vegetables will compete actively for nitrate nitrogen as a mobile nutrient and water. The mobile nutrients must be shared. The fewer the plants, the larger this share is for each plant. Also, this nitrate nitrogen is poisonous for the people who use these vegetables. Nitrate is converted to nitrite by the existing bacteria in the stomach and the Gastro-Intestinal (GI) tract. When nitrite is entered into the blood cells, it converts the hemoglobin to methemoglobin, which causes the anoxemia and cyanosis. The increasing use of pesticides and chemical fertilizers, especially the fertilizers with nitrates compounds, which have been common for the increased production of agricultural crops, has caused the nitrate pollution in the (soil, water, and environment). They have caused a lot of damage to humans and animals. In this research, the nitrate accumulation in different kind of vegetables such as; green pepper, tomatoes, egg plants, watermelon, cucumber, and red pepper were observed in the suburbs of Mashhad, Neisabour, and Sabzevar cities. In some of these cities, the information forms of agronomical practices collected were such as; different vegetable crops fertilizer recommendations, varieties, pesticides, irrigation schedules, etc., which were filled out by some of our colleagues in the research areas mentioned above. Analysis of the samples was sent to the soil and water laboratory in our department in Mashhad. The final results from the chemical analysis of samples showed that the mean levels of nitrates from the samples of the fruit crops in the mentioned cities above were all lower than the critical levels. These fruit crop samples were in the order of: 35.91, 8.47, 24.81, 6.03, 46.43, 2.06 mg/kg dry matter, for the following crops such as; tomato, cucumber, eggplant, watermelon, green pepper, and red pepper. Even though, this study was conducted with limited samples and by considering the mean levels, the use of these crops from the nutritional point of view will not cause the poisoning of humans., {"references":["Baybordi, M., H. Siadat. Agriculture, Fertilizers and Environment (translated). Nezhat Publishing Institute. Yara Internatinal Company. 2005. pp.305.","Chongpraditnum, P., P. Luksanawimol, P. Limsmutchaiporn, and S. 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Godollo. 2004, pp:5-24.\n[13]\tWard MH, de Kok TM, Levallois P, et al. Workgroup report: Drinking-water nitrate and health--recent findings and research needs. Environ Health Perspect. 2005;113(11):1607–1614. (PMC free article) (PubMed).\n[14]\tWHO (World Health Organization). Health hazards from nitrates in drinking water. WHO, Regional Office for Europe, Switzerland. 1993."]}