Augu maiņas produktivitāte atkarībā no ziemas kviešu īpatsvara tajā un augsnes apstrādes sistēmas: promocijas darbs zinātnes doktora grāda (Ph.D.) iegūšanai lauksaimniecības, meža un veterinārajās zinātnēs = Productivity of crop rotation depending on winter wheat proportion in it and soil tillage system

The doctoral thesis was developed in the period from 2017 to 2024 at the Institute of Soil and Plant Sciences of the Latvian University of Life Sciences and Technologies (former Latvia University of Agriculture until 2022). The field trials were conducted at Latvia University of Life Science and Technologies Faculty of Agriculture and Food Science (former Faculty of Agriculture) Research and Study Farm “Pēterlauki”, field trial period: four harvest seasons (2016/2017–2019/2020); soil analysis data collected from the results of research conducted in 2010, and samples for comparison collected in 2017 and 2022. Hypotheses: (1) Reducing the share of winter wheat in crop rotation improves the productivity of winter wheat increases the total energy yield of crop rotation (GJ haE−1), and the production of winter wheat is more profitable in long term (EUR haE−1); (2) Conventional and reduced soil tillage ensure equivalent winter wheat yields. Research tasks: (1) Assess the growth and development of winter wheat depending on crop rotation and soil tillage system, (2) Determine the winter wheat yield and the formation of its components depending on crop rotation and tillage system, (3) Evaluate the quality of the winter wheat yield depending on the studied factors, (4) Assess the productivity of other crops included in crop rotations in two tillage systems, (5) Determine the influence of studied factors on energy yield of winter wheat and other crops included in the crop rotations and the total energy yield of the crop rotation, (6) Evaluate the accumulation of soil organic carbon depending on the investigated factors, (7) Calculate and analyse the economic benefit of crop rotation depending on the proportion of wheat in it and the tillage system. The structure of the thesis: Chapter 1 – Literature review, which includes six subsections. The subsections present the characteristics and importance of the crops studied in the work, describe the importance of crop rotation, analyse different tillage systems, explain the energy productivity of field crop biomass, characterise the accumulation of soil organic carbon depending on crop rotation and soil tillage and summarise the results of research on the economic benefits of different crop rotations, applying different tillage systems. Chapter 2 – Research conditions and methodology consists of five sub-chapters, which describe the study site, the investigated variants, the agrotechnology used in the trial, the observations and analyses, and the meteorological situation during the trial period. Chapter 3 – Results and discussion includes five sub-chapters that present results on winter wheat growth and development, yield and grain quality depending on the used crop rotation and the tillage system. The productivity of the other crops included in the thesis during the research period was analysed. The energy yield of the crop rotation variants used analysed, the accumulation of soil organic carbon in the studied crop cultivation variants was explained, and economic evaluation of the crop rotation variants in two different tillage systems was performed. Conclusions include answers to the research tasks.