Stationary field experiment pertaining to the winter wheat in Croatia was performed during the three seasons. This study’s intention was to examine and diagnose the effect of tillage systems (TS) on soil chemical properties (soil acidity, phosphorus P, potassium K, and organic matter content). The TSs were as follows: CT — ploughing up to 30 cm depth, DT — disking up to 8-12 cm depth, LT — loosening up to 35 cm depth, and NT — no-tillage. The experimental design was a randomised block design in four repetitions, in which the basic TS plot amounted to 540 m2. Soil sampling for 0-30 cm soil layer was performed prior to setting up the experiment and subsequent to the three seasons with a total of 320 soil samples. Chemical analysis was performed according to standard pedological procedures. Economic indicators were calculated using economic equations and standards, whereas statistical analysis was performed with SAS 9.3 and Microsoft Excel 2016. Generated results indicate that the expressed accumulation of phosphorus and potassium appeared with a distinct vertical stratification in the systems with shallower tillage or no-tillage. At the same time, these TSs ensured the soil organic matter and soil fertility preservation. A conservable agricultural production of reduced soil tillage systems has its efficiency and vigor while providing soil degradation. Stacionarni poljski pokus za ozimu pšenicu u Hrvatskoj proveden je tijekom triju sezona . Namjera ovoga istraživanja bila je ispitati i dijagnosticirati utjecaj sustava obrade tla (TSs) na kemijska svojstva tla (kiselost tla, sadržaj fosfora, kalija i organske tvari. TSs-i su bili CT — oranje do 30 cm dubine; DT — tanjuranje do 8-12 cm dubine; LT — rahljenje do 35 cm dubine; NT — bez obrade tla. Eksperimentalni dizajn je bio randomizirani blok dizajn u četiri ponavljanja, u kojem je osnovna TSs parcela bila 540 m2 . Uzorkovanje za sloj tla 0-30 cm obavljeno je prije postavljanja pokusa i nakon triju sezona s ukupno 320 uzoraka tla. Kemijska analiza provedena jer prema standardnim pedološkim postupcima. Standardna statistička analiza provedena softverom SAS 9.3 i Microsoft Excel 2016. Dobiveni rezultati upućuju da se na sustavima s plićom obradom ili bez obrade javlja izražena akumulacija fosfora i kalija uz izraženu vertikalnu stratifikaciju. Istodobno ovi TSs-i osiguravaju konzervaciju organske tvari tla i očuvanje plodnosti tla. Poljoprivredna proizvodnja uz primjenu reduciranih sustava obrade tla ima svoju učinkovitost i snagu kroz sprječavanje degradacije tla.