FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Sep. 30, 2025

Schedule of Estimated Fair Values for Each Type of Instrument

The following table summarizes the fair value hierarchy for each type of instrument carried at fair value on a recurring basis (in millions):


	Fair Value Measurements at September 30, 2025
	Total Carrying Value at September 30, 2025		Quoted Prices in Active Market (Level One)		Significant Other Observable Inputs (Level Two)		Significant Unobservable Inputs (Level Three)
Asset Class:
Mutual fund investments in a non-qualified savings plan(a)(b)	$	3.5	$	3.5	$	—	$	—
Derivatives designated as hedging instruments - natural gas instruments, net	7.9		—		7.9		—

Total assets	$	11.4	$	3.5	$	7.9	$	—
Liability Class:
Derivatives designated as hedging instruments - natural gas instruments, net	$	(8.7)	$	—	$	(8.7)	$	—

Liabilities related to non-qualified savings plan	(3.5)		(3.5)		—		—
Total liabilities	$	(12.2)	$	(3.5)	$	(8.7)	$	—

(a)Includes mutual fund investments of approximately 29% in the common stock of large-cap U.S. companies, 4% in the common stock of small to mid-cap U.S. companies, 2% in the common stock of international companies, 9% in bond funds, 20% in short-term investments and 36% in blended funds.

(b)The investments related to a non-qualified deferred compensation arrangement on behalf of certain members of management. The Company has a liability for the related-party transaction recorded in Other noncurrent liabilities for deferred compensation obligations.


	Fair Value measurements at September 30, 2024
	September 30, 2024		Quoted Prices in Active Market (Level One)		Significant Other Observable Inputs (Level Two)		Significant Unobservable Inputs (Level Three)
Asset Class:
Mutual fund investments in a non-qualified savings plan(a)(b)	$	3.1	$	3.1	$	—	$	—
Derivatives not designated as hedging instruments - natural gas instruments, net	0.6		—		0.6		—
Total assets	$	3.7	$	3.1	$	0.6	$	—
Liability Class:
Derivatives designated as hedging instruments - natural gas instruments, net	$	(1.9)	$	—	$	(1.9)	$	—
Liabilities related to non-qualified savings plan	(3.1)		(3.1)		—		—
Total liabilities	$	(5.0)	$	(3.1)	$	(1.9)	$	—

(a)Includes mutual fund investments of approximately 35% in the common stock of large-cap U.S. companies, 5% in the common stock of small to mid-cap U.S. companies, 5% in the common stock of international companies, 10% in bond funds, 5% in short-term investments and 40% in blended funds.

The Company is required to disclose the fair value of financial instruments that are not recognized at fair value in the statement of financial position for which it is practicable to estimate that value (in millions):


			Fair Value Measurements at September 30, 2025 Using
	Total Carrying Value at September 30, 2025		Quoted Prices in Active Market (Level One)		Significant Other Observable Inputs (Level Two)		Significant Unobservable Inputs (Level Three)

8.00% Senior Notes due June 2030	$	650.0	$	—	$	680.1	$	—
6.75% Senior Notes due December 2027	150.0		—		150.1		—


			Fair Value Measurements at September 30, 2024 Using
	Total Carrying Value at September 30, 2024		Quoted Prices in Active Market (Level One)		Significant Other Observable Inputs (Level Two)		Significant Unobservable Inputs (Level Three)

Term Loan and Revolving Credit Facility	$	383.9	$	—	$	379.1	$	—
6.75% Senior Notes due December 2027	500.0		—		497.0		—

The following fair value hierarchy table summarizes the Company’s assets that were written down to their fair value on a nonrecurring basis (in millions):


				Fair Value Measurements at the Measurement Date Using
	Measurement Date	Total Carrying Value at Measurement Date		Quoted Prices in Active Market (Level One)		Significant Other Observable Inputs (Level Two)		Significant Unobservable Inputs (Level Three)		Total Gains (Losses)
Intangible assets, net
Definite-lived intangible assets(a)	March 31, 2025	$	—	$	—	$	—	$	—	$	(53.0)
Definite-lived intangible assets(b)	March 22, 2024	$	—	$	—	$	—	$	—	$	(15.6)
Indefinite-lived intangible assets(c)	September 3, 2024	$	—	$	—	$	—	$	—	$	(17.6)
Property, plant, and equipment, net
Property, plant and equipment, net(d)	June 30, 2025	$	—	$	—	$	—	$	—	$	(0.7)
Property, plant and equipment, net(e)	January 23, 2024	$	—	$	—	$	—	$	—	$	(74.8)
Goodwill
Plant Nutrition goodwill(f)	March 31, 2024	$	—	$	—	$	—	$	—	$	(51.0)
Fortress goodwill(f)	March 31, 2024	$	—	$	—	$	—	$	—	$	(32.0)

(a) On March 31, 2025, the Company recorded an impairment loss of $53.0 million related to definite-lived intangible asset after determining that no future cash flows were expected from these assets. As a result, the Fortress definite-lived intangible asset was assigned a fair value of zero using the income approach under ASC 820. Fair Value Measurement (see Note 2. Summary of Significant Accounting Policies).

(b) On March 22, 2024, the Company recorded an impairment loss of $15.6 million related to definite-lived intangible asset associated with the magnesium chloride-related assets as a result of the evaluation using the income approach.

(c) On September 3, 2024, the Company recorded an impairment loss of $17.6 million related to definitive-lived intangible asset water right, due to the Voluntary Agreement of donating non-production related water rights to be used by the State of Utah for lake conservation and preservation.

(d) On June 30, 2025, Fortress-related property, plant and equipment, net with a carrying value of $0.7 million was written down to its fair value of $0, resulting in a loss on impairment, net of $0.7 million, due to no future expected use of property, plant and equipment, net at June 30. 2025.

(e) On January 23, 2024, the Company terminated its pursuit of its lithium development. Consequently, the Company evaluated the capitalized assets, including site preparation, project engineering, equipment and material and capitalized labor and interest and recorded an impairment charge of $74.8 million.

(f) On March 31, 2024, the Company performed the interim goodwill impairment test related to the Company’s Plant Nutrition segment, primarily due to decreases in projected future revenues and cash flows and an increase in discount rates due to the uncertain regulatory environment in Utah and recorded a goodwill impairment of $51.0 million. Following the impairment charge, there was no remaining goodwill balance for the Plant Nutrition reporting unit.

(g) On March 31, 2024, the Company recorded a goodwill impairment loss of $32.0 million related to the Company’s Fortress reporting unit included in the Corporate and Other segment, primarily due to the changes in assumptions surrounding the magnesium chloride-based fire retardants which impacted projected future revenues and cash flows. Following the impairment charges, there was no remaining goodwill balance for the Fortress reporting unit.