Effects of cropping systems on soil fertility and winter wheat dough quality

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.