Sestava talnih mikrobnih združb po žetvi soje v odvisnosti od gnojenja in obdelave tal v dolgoletnem poljskem poskusu

Potočnik, Živa (author), Suhadolc, Marjetka (mentor)

Intenzifikacija kmetijstva v zadnjih desetletjih je prispevala k degradaciji tal, zato je vedno več zanimanja za uvajanje bolj trajnostnih kmetijskih praks ter poznavanje njihovega vpliva na kakovost tal in talni mikrobiom. V magistrski nalogi smo preučevali vpliv dolgoletne obdelave tal (brez obdelave, orano) in gnojenja (brez gnojenja ter gnojenje z mineralnimi, organskimi in kombinacijo gnojil) na vsebnost organskega ogljika (Corg), mikrobnega ogljika (Cmic) in sestavo mikrobnih združb. Tla smo vzorčili na 21-letnem poljskem poskusu Oddelka za agronomijo Biotehniške fakultete jeseni leta 2020 po žetvi soje na štirih globinah (0–1 cm, 0–10 cm, 10–20 cm in 30–60 cm). Ugotovili smo kopičenje organskega ogljika v zgornjih plasteh tal brez obdelave, največja vsebnost Corg je bila 7,6 % (pri obravnavanju z organskim gnojenjem na globini 0-1 cm). Na globini 0-10 cm smo ugotovili večjo vsebnost Corg v tleh sistema brez obdelave (povprečje vseh obravnavanj je bilo 3,2 %) v primerjavi z oranjem (povprečje vseh obravnavanj je bilo 2,3 %). Posledično se je s povečanjem Corg povečala talna mikrobna biomasa, ki smo jo določili z metodo fumigacije s kloroformom in ocenili s količino skupne talne DNA. Vsebnosti mikrobnega biomasnega ogljika in dušika ter količina DNA so bile večje v zgornjih plasteh tal (0–1 cm in 0–10 cm) pri sistemu brez obdelave. Številčnost bakterij, gliv in krenarhej smo opredelili s kvantitativno verižno reakcijo s polimerazo (qPCR). V celotnem talnem profilu je bilo največ bakterij (povprečna številčnost sistema brez obdelave na globini 0–1 cm 7,7×109), manj je bilo gliv in krenarhej (povprečna številčnost sistema brez obdelave na globini 0-1 cm za glive 3,8×108 in krenarheje 2,7×108). Številčnost mikroorganizmov se je z globino zmanjševala. Razmerje med bakterijami in glivami je bilo najožje na globini 0–1 cm, kjer smo ugotovili tudi značilne razlike med obravnavanji. V prihodnjih raziskavah je potrebno preučiti sestavo mikrobne združbe na nižjih taksonomskih nivojih, prav tako pa je pomembno preučiti tudi povezavo med sestavo in delovanjem talnega mikrobioma.

• Language: Slovenian
• Keywords: bakterije, glive, krenarheje, organski ogljik, mikrobna biomasa
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [Ž. Potočnik]
• Year: 2022
• PID: 20.500.12556/RUL-136963
• UDC: 631.461:579.26
• COBISS.SI-ID: 109165571
• Publication date in RUL: 27.05.2022

Secondary language

• Language: English
• Title: Soil microbial communities composition after harvest of soya in dependence of fertilisation and tillage in long-term field experiment

Abstract

The intensification of agriculture in recent decades has contributed to soil degradation, and there is growing interest in adopting more sustainable agricultural practices and understanding their impact on soil quality and the soil microbiome. In this master thesis, the influence of long-term tillage (no-till, ploughing) and fertilisation (no fertilisation and fertilisation with mineral, organic, and a combination of fertilisers) on soil organic carbon (Corg) and microbial carbon (Cmic) content, and microbial community composition was investigated. Soils were sampled at four depths (0-1 cm, 0-10 cm, 10-20 cm, and 30-60 cm) in a 21-year field trial conducted by the Department of Agronomy, Faculty of Biotechnology, in the autumn of 2020 after soybean harvest. We found organic carbon accumulation in the top layers of the no-till soils, with a maximum Corg content of 7.6 % at a depth of 0-1 cm of organic fertiliser treatment. At a depth of 0-10 cm, we found a higher Corg content in the soil of the no-till system (the average of all treatments was 3.2 %) compared to ploughing (the average of all treatments was 2.3 %). As a consequence, the soil microbial biomass increased as determined by the chloroform fumigation method and estimated by the amount of total soil DNA. Microbial biomass carbon and nitrogen content and DNA amount were higher in the top soil layers (0-1 cm and 0-10 cm) in the no-till system. The abundance of bacteria, fungi and Crenarchaea was determined by quantitative polymerase chain reaction (qPCR). Bacteria were most abundant throughout the soil profile (the average abundance of the no-till system at a depth of 0-1 cm 7.7 × 109), whereas fungi and Crenarchaeota were less abundant (the average abundance of the no-till system at a depth of 0-1 cm for fungi 3.8×108 and for Crenarchaea 2.7×108). The abundance of micro-organisms decreased with depth. The ratio of bacteria to fungi was narrowest at a depth of 0-1 cm, where we also found significant differences between treatments. Future research needs to investigate microbial community composition at lower taxonomic levels, and it is also important to investigate the relationship between composition and functioning of the soil microbiome.

• Keywords: bacteria, fungi, Crenarchaeota, organic carbon, microbial biomass