The influence of residual fertilizing by phosphorus and potassium upon winter wheat grain yield and some soil chemical properties in crop rotation maize-soybean-winter wheat-sugar beat

Abstract

U radu se iznose rezultati osmogodišnjih istraživanja gnojidbe na zalihu fosforom i kalijem za ozimu pšenicu u četveropoljnom mjembenom plodoredu kukuruz-soja-ozima pšenica-šećerna repa u dvije rotacije plodoreda na lesi-viranom tlu na pretaloženom lesu, lokalitet Lukač (Virovitica). Uz negnojenu varijantu i standardnu mineralnu gnojidbu, u pokusu su bile zastupljene dvije varijante gnojidbe na zalihu fosforom i kalijem za četverogodišnje razdoblje i jedna varijanta s gnojidbom na zalihu za dvogodišnje razdoblje. U odnosu na prinos zrna ozime pšenice učinkovitost gnojidbe na zalihu tijekom osmogodišnjeg istraživačkog razdoblja bila je promjenjiva. Prema prosječnim osmogodišnjim rezultatima pri gnojidbi na zalihu ipak su dobiveni viši prinosi u usporedbi sa standardnom mineralnom gnojidbom, pri čemu je važniju ulogu od kalija odigrao fosfor s obzirom na fiziološke potrebe pšenice. Isto tako, prema prosječnim osmogodišnjim vrijednostima, sadržaj biljci pristupačnog fosfora i kalija u tlu u svih je gnojenih varijanata, osim standardne mineralne gnojidbe, porastao signifikantno u odnosu na negnojenu varijantu. Glede zasićenosti bazama, nastale promjene prvenstveno su se očitovale njezinim smanjenjem, što, drugim riječima, znači da je mineralna gnojidba djelovala nepovoljno na sve one parametre koji su izravno povezani s reakcijom tla, kao i one koji neizravno iskazuju takva obilježja.The paper presents the results of eight-year investigations of residual fertilization with phosphorus and potassium for winter wheat grown in the four-year field crop rotation: maize-soybean-winter wheat-sugar beet in two rotations on luvic soil on redeposited loess, locality Lukač (Virovitica). Besides the unfertilized variant and standard mineral fertilization, the trial also included two treatments of residual fertilization with phosphorus and potassium for a four-year period and one residual fertilization treatment for a two-year period. Efficiency of residual fertilization with respect to the winter wheat grain yield varied over the eight-year research period. Nevertheless, according to average eight-year results, higher yields were obtained with residual fertilization compared to standard mineral fertilization, in which, due to wheat physiological requirements, phosphorus had a more important role than potassium. Also, according to average eight-year values, plant available phosphorus and potassium contents of the soil increased significantly in all fertilized variants, except for standard mineral fertilization, compared to the unfertilized control variant. In the case of base saturation, the induced changes were primarily reflected in its reduction; in other words, mineral fertilization had an adverse effect on all parameters directly related to soil reaction, as well as on the parameters indirectly expressing such characteristics