Fertilizer source and placement affect nutrient mobility through the soil profile and productivity of maize

Maximizing maize (Zea mays L.) grain productivity for high-yielding areas requires aligning the nutrient availability in the soil with the crop nutrient demand throughout the season. While the traditional practice of pre-plant broadcast fertilizer application is widely used due its convenience, it may be limiting nutrient availability and grain yield due to nutrient tie-up, loss, and/or positional unavailability. The mineral nutrients phosphorus (P) and potassium (K) are considered immobile in the soil and are typically thought to have limited movement through the soil profile. Concentrating these nutrients, however, may enhance their movement into the soil profile and increase their availability for root uptake. Complementing a traditional fertilizer program by adding the multi-nutrient fertilizer source POLY 4 (containing K, S, Ca, Mg) that contains S, and including biostimulant coatings like sugars or humic acid (HA) may further improve nutrient availability and crop productivity. For these reasons, the objective of the first chapter was to investigate how different timing × placement (pre-plant broadcast or in-season surface dribble, also known as dry-drop) and sources of fertilizer, with and without coatings, affect soil nutrient availability, plant uptake, and productivity of maize. The focus of the second chapter was to determine how fertilizer placement affects movement of nutrients into the soil profile and their subsequent availability throughout the crop season. The movement of P, K, and S into the soil profile, and the subsequent impact on maize productivity was examined by comparing the traditional P and K fertilizer sources with added POLY4, with or without organic coatings, and by pre-plant broadcasting the fertilizer or by concentrating it along the crop row in-season as a dry-drop application. The second chapter examined the use of traditional pre-plant broadcast of P, K, and S fertilizers compared to two methods of in-season concentrated surface applications as a granular dry fertilizer (dry-drop) or as liquid fertilizer (Y-drop). Results for soil characteristics varied by site and year, and P, K, and S exhibited stratification patterns across treatments. However, when those nutrients were concentrated in one spot, by dry-drop or Y-drop placement, they consistently increased near-row soil concentrations of P, K, and S compared to pre-plant broadcast, with an average increase of + 32 mg kg-1 in soil P, +43 mg kg-1 increase in soil K, and +12 mg kg-1 increase in soil S. Concentrating the nutrients moved P and K through the soil profile down to as much as 30 cm depth, challenging the conventional idea that these nutrients are immobile. In 2023, less-than-average seasonal rainfall slowed nutrient solubilization and incorporation, reducing the effectiveness of the in-season fertilization, while 2024 experienced more typical rainfall, resulting in enhanced nutrient availability, crop nutrient uptake, and growth compared to 2023. Even though soil tests indicated nutrient sufficiency at most sites, fertilizer applications resulted in measurable yield increases across all the fertilizer treatments. Despite minimally impacting early vegetative growth, fertilizer applications containing POLY 4 significantly enhanced grain yield, producing the highest yield of 13.44 Mg ha⁻¹. The in-season applications were year- and site-dependent, but the overall results in grain yield were at least equivalent to pre-plant broadcast application. The humic acid and sugar coatings did not increase yields, and the combination of humic acid and sugar coating tended to reduce yield by up to 0.32 Mg ha⁻¹. Tissue analysis indicated that grain nutrient concentrations were mostly unaffected by the fertilizer treatments, while stover exhibited increased K and S accumulation when provided with POLY 4. This study supports the hypothesis that in-season surface banding of fertilizer near the crop row increases nutrient availability in the proximity of the crop root system. Fertilizer application increased grain yield in most of the experiments, regardless of the area being considered nutrient sufficient based on soil test recommendations. Overall, this research highlights the importance of fertilizer placement and fertilizer source for modern maize production systems.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Frigo Fernandes, Gabriela

Contributors dc:contributor

• Below, Frederick E.
• Mulvaney, Richard
• Jones, John
• Sible, Connor

• Fertilizer
• Potassium
• Phosphorus
• Sulfur
• Polyhalite
• Mop
• Map
• Dribble Surface Application
• Surface Banding Fertilizer
• Broadcast Application
• Banded Fertilizer Application
• Nutrient Movement
• Nutrient Mobility
• Midwest Maize Nutrition
• Nutrient Stratification
• Alfisols
• Mollisols
• Humic Acid
• Sugar

Statement dc:rights

• Copyright 2025 Gabriela Frigo Fernandes

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129988

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129988