We had two important product launches in the quarter, Overwatch Herbicide based on our Isoflex active in Australia and Xyway fungicide in the U.S. Isoflex is one of 11 new active ingredients we plan to launch this decade.
Both launches have exceeded our expectations and have delivered approximately $50 million of Q1 sales.
We returned over $135 million to shareholders in the quarter through our recently increased dividend and share repurchases.
We reported $1.2 billion in first quarter revenue, which reflects a 4% decrease on a reported basis and a 5% decrease organically.
Adjusted EBITDA was $307 million, a decrease of 14% compared to the prior year period and $2 million above the midpoint of our guidance range.
EBITDA margins were 25.7%, a decrease of 290 basis points compared to the prior year.
Adjusted earnings were $1.53 per diluted share in the quarter, a decrease of 17% versus Q1 2020, but also $0.03 above the midpoint of our guidance range.
Q1 revenue decreased by 4% versus prior year, driven by a 4% volume decrease and a 1% price decline.
Sales in Asia increased 18% year-over-year and 13% organically, driven by double-digit growth in Australia, Japan, the Philippines, Thailand and Vietnam.
EMEA sales were down 4% year-over-year and 8% organically.
In North America, sales decreased 8% year-over-year.
Sales decreased 22% year-over-year and 13% organically.
As a reminder, we were facing a particularly difficult comparison in Latin America, where sales increased 26% year-over-year and 38% organically in Q1 2020.
Brazil's cotton business was very strong for us a year ago, which did not repeat this season as cotton hectares were down 15%.
EBITDA in the quarter was down $50 million year-over-year due to a very strong Q1 2020 comparison.
FMC full year 2021 earnings are now expected to be in the range of $6.70 and to $7.40 per diluted share, a year-over-year increase of 14% at the midpoint.
Our 2021 revenue forecast remains in the range of $4.9 billion to $5.1 billion, an increase of 8% at the midpoint versus 2020 and 8% organic growth.
EBITDA is still expected to be in the range of $1.32 billion to $1.42 billion, representing 10% year-over-year growth at the midpoint.
Guidance for Q implies a year-over-year sales growth of 6% at the midpoint on a reported basis and 5% organically.
We are forecasting EBITDA growth of 1% at the midpoint versus Q2 2020, and earnings per share is forecasted to be up 3% year-over-year.
Revenue is expected to benefit from 6% volume growth, with the largest growth in Asia and a 2% contribution from higher prices.
We expect new products to contribute $400 million in revenue this year.
We are taking cost control actions to limit the net cost headwind to an incremental $10 million versus what we showed in February.
We also intend to offset the higher raw material costs with an additional $10 million in price increases, which will come primarily in the second half of the year.
On the revenue line, we are expecting positive contributions from all categories: volume 4%, pricing 1% and FX 1%.
We forecast year-over-year revenue growth of 15% in the second half driven by five main elements.
Cotton in Brazil is the most obvious to us, as growers have indicated, a 15% increase in hectares for next season.
Our guidance also implies a 30% year-over-year EBITDA growth in the second half of the year.
FX was a modest tailwind for revenue growth in Q1 at 1% versus our expectations of a 2% headwind, as the U.S. dollar weakened against many currencies with the notable exception of the Brazilian reais.
Interest expense for the first quarter was $32.4 million, down $8.4 million from the prior year period, with the benefit of lower LIBOR rates as well as lower foreign debt and lower term loan balances, partially offset by higher average commercial paper balances.
We continue to anticipate interest expense between $130 million and $140 million for the full year.
Our effective tax rate on adjusted earnings for the first quarter was 13.1% as anticipated and in line with our continued expectation for a full year tax rate between 12.5% and 14.5%.
Gross debt at the end of the quarter was $3.6 billion, up over $300 million from the prior quarter, with the expected seasonal build of working capital.
Gross debt to trailing 12-month EBITDA was 3.0 times at the end of the first quarter, while net debt-to-EBITDA was 2.7 times.
Free cash flow for the first quarter was negative $354 million.
We continue to expect to generate full year free cash flow within a range of $530 million to $620 million, with the vast majority of this cash flow coming in the second half of the year.
We returned $137 million to shareholders in the quarter via $62 million in dividends and $75 million of share repurchases, buying back 696,000 shares in the quarter at an average price of $107.73 per share.
We continue to anticipate paying dividends approaching $250 million and repurchasing $400 million to $500 million of FMC shares this year.
We are on track to deliver more than $700 million to shareholders this year, building on a trend since 2018 of improving cash generation and returning excess cash to shareholders.

Summary:
We reported $1.2 billion in first quarter revenue, which reflects a 4% decrease on a reported basis and a 5% decrease organically.
Adjusted earnings were $1.53 per diluted share in the quarter, a decrease of 17% versus Q1 2020, but also $0.03 above the midpoint of our guidance range.
FMC full year 2021 earnings are now expected to be in the range of $6.70 and to $7.40 per diluted share, a year-over-year increase of 14% at the midpoint.
Our 2021 revenue forecast remains in the range of $4.9 billion to $5.1 billion, an increase of 8% at the midpoint versus 2020 and 8% organic growth.