Dynamic of different soil phosphorus fractions related to long-term fertilizing of maize monoculture

Dinkayehu Alamnie Asrade, MSc

Disertační práce

Abstract:

Long-term maize monoculture was evaluated from the point of view different fertilizing systems (organic and mineral) in the small plot field experiments at two locations: Červený Újezd (Haplic luvisol) and Suchdol (Chernozem). The main objective was to evaluate phosphorus (P) behavior. Following groups of parameters were evaluated: i) plant parameters: silage maize biomass yield, P uptake, P content in aboveground biomass, simple P balance, ii) soil P tests: readily available P, potentially available P, aluminum and iron extracted with Mehlich 3 method, organic and inorganic P and pseudototal P content, and iii) soil sorption characteristics: P sorption index, degree of P saturation (DPS), P stability ratio according to aluminum and iron. Based on the results and hypothesis, we can state the following key findings. Long-term sewage sludge fertilization led to significant phosphorus accumulation in both soil types (Chernozem and Luvisol). The accumulation was due to high P application, low mobility of P in sewage sludge (due to Fe and Al precipitation), and comparable P uptake with other fertilization treatments. Example: at Luvisol, a P dose of 82.1 kg ha-1 year-1 resulted in a total accumulation of 1589 kg P ha-1 over 27 years. The hypothesis that increasing applied phosphorus reduces soil P-sorption was confirmed, particularly with organic fertilization. Sewage sludge showed higher P stability and accumulation tendency as compared to cattle slurry and farmyard manure. However, in Chernozem, DPS after long-term sewage sludge application exceeded 100%, indicating a high risk of P leaching. Nitrogen-only application resulted in more negative P balance than no fertilization, highlighting the risk of P depletion, which was confirmed with lower DPS values compared to unfertilized control. Continuous monoculture led to significant maize yield reduction after 15 years, regardless of fertilization method. Phosphorus did not limit plant growth initially, but soil fatigue, rising temperatures, and uneven precipitation distribution likely contributed to yield decline. The main conclusions of this thesis are following: sewage sludge as a nitrogen source is effective only in P-deficient areas. Otherwise, it risks P accumulation and leaching. Mineral nitrogen alone can deplete P more than no fertilization. Further research is needed to optimize fertilization strategies for maize monoculture considering weather development, other nutrients, and long-term sustainability.

Keywords

Maize monoculture, phosphorus accumulation, P-sorption, sewage sludge, soil fatigue, yield decline, nitrogen fertilization

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 21. 8. 2024

Obhajoba závěrečné práce

• Vedoucí: prof. Ing. Jiří Balík, CSc. dr. h. c.
• Oponent: Jan Haberle, externi, Pavel Ryant, externi, Ladislav Ducsay, externi

Česká zemědělská univerzita v Praze

Fakulta agrobiologie, potravinových a přírodních zdrojů

Doktorský studijní program:
Plant Sciences