Characterizing plant biostimulants and their impact on the soil microbiome and productivity of maize

Sible, Connor Nelson

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https://hdl.handle.net/2142/115409 Copy

Description

Title

Characterizing plant biostimulants and their impact on the soil microbiome and productivity of maize

Author(s)

Sible, Connor Nelson

Issue Date

2022-04-22

Director of Research (if dissertation) or Advisor (if thesis)

Below, Frederick

Doctoral Committee Chair(s)

Below, Frederick

Committee Member(s)

• Riechers, Dean
• Margenot, Andrew
• Butts-Wilmsmeyer, Carolyn

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Plant Biostimulants
• Soil Health
• Maize

Abstract

Plant biostimulants are becoming popular in the agricultural market as products to increase growth, health, and/or yield of crop plants. The challenge is that there are many types of biostimulants, each with unique mechanisms of action, and these dynamics make it difficult to optimize product placement into grower systems. Multiple studies and reviews have investigated individual biostimulant categories for their influence on crop growth and development, and their effects on soil ecosystems and the mechanisms responsible for the observed responses. However, these studies are most often limited to greenhouse and lab experiments using more traditionally known biostimulants with little research at the field scale. The objective of this research is to better understand the individual categories of biostimulants and their interactions with plant and soil nutrient cycling through a comprehensive review of the literature and from intensive field studies. What are the major plant biostimulants and how do they influence field crop production? Plant biostimulants are specialty products used to increase crop production and are quickly becoming common in the agricultural seed and chemical marketplace. This review presents a summary of the current status and descriptions of plant biostimulants with available literature on their uses in row crop production of maize (Zea mays L.), soybean [Glycine max (L.) Merr.], wheat (Triticum aestivum) and other major crop species. Biostimulants have much potential to improve crop production through enhanced yields, grain quality, and increased sustainability of agronomic production systems, particularly in relation to nutrient management. However, there is great variability in the efficacy of biostimulants and a limited understanding of the mechanisms responsible in field-tested scenarios where differences are observed. These unknown mechanisms may align with recognized soil health indicators, providing opportunity for unrealized biostimulant potential beyond crop growth and development. This review aims to identify the predominant types of crop biostimulants, the known understandings of their modes of action, and examples of their current field efficacy with an outlook for their future. What are the effects of soil applied biostimulants and starter fertilizers on biological soil health indicators, soil mineral nutrients, and maize growth and yield? While plant biostimulants have been shown to enhance nutrient uptake and use efficiency of maize, the exact mechanisms driving these responses are not fully understood. The objectives of this research were to test in-furrow applications of biostimulants or biostimulant/starter fertilizer blends when applied with no additional fertility or a broadcast application of N, P2O5, K2O, S, Zn, and B for their effects on soil biological indicators and subsequent maize growth and nutrient accumulation. Averaged across fertility levels, four of five treatments increased V8 vegetative biomass between 0.09 to 0.15 Mg ha-1 (+9.1 to 15.2%), with the microbial fermentation product increasing R6 stover Zn accumulation (+21 g ha-1, +10.8 %). All in-furrow applications tended to improve Zn grain content, regardless of changes in yield, serving as a possible management practice for biofortification of maize to combat global Zn malnutrition. Biostimulants resulted in minimal effects on the soil biological indicators, with the only notable influence being a numerical increase in microbial biomass carbon (MBC) at three days after application of the marine extract (+32 mg kg-1, +10.2 %). Humic starter fertilizers increased microbial biomass phosphorus (MBP) (+1.0 mg kg-1, +41.7 %) and beta-glucosidase (BG) activities (+0.06 μmol pNP g-1 soil, +11.5%) over the untreated control when analyzed across fertilizer blocks and sample timepoints. Overall findings show that biostimulants improve maize growth and micronutrient uptake, and that biological soil health indicators of enzyme activities and microbial biomass are influenced more by starter fertilizers than by the individual biostimulants tested in this study. When used in a systems approach, how do biostimulants interact with the native soil microbiome to enhance residue decomposition and mitigate the continuous maize yield penalty? Continuous maize (Zea mays L.) (CM) cropping has been proposed to increase carbon sequestration through enhancement of plant residues. These residues, however, can lead to yield decreases in what is known as the continuous maize yield penalty (CMYP). The objectives of this research were to 1) determine the long-term rotation effects of continuous maize and maize/soybean [Glycine max (L.) Merr.] (MS) on soil chemical and biological properties, and 2) evaluate if the efficacy of residue management practices to mitigate the CMYP is associated with rotation-induced changes of soil properties. Bacterial communities were unchanged by crop rotation, while fungal assemblage, particularly arbuscular mycorrhizal fungi (AMF), were influenced by rotation and site. For site A, a nearly 3-fold increase in the relative abundance of AMF was observed for the CM rotation, while at site B the MS rotation had a greater relative abundance of AMF. C-hydrolytic enzyme activities were higher under CM cropping, while crop rotation effects on the soil organic matter and nutrient levels was site-dependent. Grain yield response to residue management (mechanical, chemical, and/or biological) were similar at both sites, even though inherent soil chemical and biological properties differed. The CMYP was 2,561 kg ha-1 with no fall residue management, while mechanical sizing of the residue along with AMS reduced the CMYP by 730 kg ha-1. The CMYP was further reduced when a microbial blend was applied with ammonium sulfate (AMS) to the sized residues, totaling a combined CMYP reduction of 1,313 kg ha-1 (51.3%). These findings indicate that the CMYP is not directly associated with the soil bacterial community, and that management to mitigate the CMYP may benefit from elevated levels of fungal diversity under CM.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Connor Sible

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