For example, in North America, Irrigation, this year we've raised price five times on irrigation systems, totaling more than 30% inclusive of upcoming increases.
Record sales of $894.6 million increased $205.8 million or nearly 30% compared to last year, an increase more than 26% on a constant currency basis.
Starting with Utility, sales of $267.9 million grew $36.5 million or 15.8% compared to last year.
Moving to Engineered Support Structures, record sales of $269.4 million increased $16 million or 6.3% compared to last year.
Global lighting and transportation sales grew 3.3% as pricing improved in all regions, and international markets benefited from increasing stimulus and infrastructure investments, especially in Europe and Australia.
Wireless communication products and components sales grew 7.2% compared to last year.
Turning to Coatings, sales of $98.2 million grew $18.2 million or 22.7% compared to last year and improved sequentially from last quarter due to improving end market demand, favorable pricing and currency impacts.
Moving to Irrigation, record global sales of $282 million grew $131.3 million or 87.2% compared to last year with sales growth across all served markets, including more than 35% growth in our technology sales.
In North America, sales of $156.1 million grew 57.6% year-over-year.
International sales of $125.9 million grew 1.4 times compared to last year, led by the ongoing delivery of the Egypt project, strong European market demand and record sales in Brazil.
Regarding our project pipeline in Africa, we recently were awarded more than $20 million of additional projects from new customers in Egypt, Sudan and Rwanda demonstrating our market leadership, global operations footprint and project management capabilities.
Their technology is currently being used on over 5,300 fields on a variety of crops including corn, soybeans, potatoes, wheat, onions, alfalfa and tomatoes.
With this acquisition, we expect those particular sales to grow more than 50% per year over the next three to five years.
Prospera brings the strongest team in the industry and we are fortunate to have 100 highly talented and motivated employees on board, including experts in data science and machine learning.
We also completed the acquisition of PivoTrac, the subscription based AgTech company that provides remote sensing and monitoring solutions for the southwest U.S. market, helping grow our technology sales to $50 million year-to-date.
In the second quarter, we were awarded projects totaling $47 million.
Additionally, over the past 18 months, we received more than 30 orders for the North American market.
In the second quarter, we were awarded three projects, totaling $25 million.
Our environment and social quality scores have improved significantly this year from a 6 to a 2 for environment and from a 6 to a 3 for social, while governance has held steady at a solid 2.
Operating income of $90.9 million or 10% of sales grew $25.2 million or 38% compared to last year driven by higher volumes in irrigation, improved operating performance and a favorable pricing notably in Engineered Support Structures.
Diluted earnings per share of $3.06 grew more than 50% compared to last year, primarily driven by very strong operating income and a more favorable tax rate of 22.5%.
On Slide 10, in Utility Support Structures, operating income of $21.2 million or 7.9% of sales decreased $4.1 million or 300 basis points compared to last year.
Record operating income of $31.9 million or 11.9% of sales increased $9 million or 290 basis points compared to last year.
In the Coatings segment, operating income of $14.7 million or 14.9% of sales was $4.3 million or 190 basis points higher compared to last year.
In the Irrigation segment, operating income of $42.9 million or 15.2% of sales nearly doubled compared to last year and was 80 basis points higher year-over-year.
We delivered positive operating cash flows of $37 million and positive free cash flow this quarter despite continued inflationary pressures, increasing our working capital needs.
This quarter we closed on Prospera acquisition for a purchase price of $300 million, funded through a combination of cash on hand and short-term borrowings on our revolving credit facility.
We also acquired 100% of the assets of PivoTrac for $12.5 million, funded by cash on hand.
Capital spending in first half of 2021 was $49 million and we returned $42 million of capital to shareholders through dividends and share repurchases, ending the quarter with just over $199 million of cash.
Our balance sheet remains strong with no significant long-term debt maturities until 2044.
Our leverage ratio of total debt to adjusted EBITDA of 2.3 times remains within our desired range of 1.5 times to 2.5 times.
Net sales are now estimated to grow 16% to 19% year-over-year driven primarily by very strong agricultural market fundamentals.
Further, we now expect Irrigation segment sales to grow 45% to 50% year-over-year and continue to assume a foreign currency translation benefit of 2% of net sales.
2021 adjusted earnings per share is now estimated to be between $10.40 and $11.10.
In Utility Support Structures, we expect a meaningful sequential improvement to the quality of earnings, beginning in the third quarter driven by margin improvement as pricing becomes more aligned with steel cost inflation.
Demand for wireless communication products and components remains strong and we expect sales growth in line with expected market growth of 15% to 20%.
Moving to Irrigation, we expect a very strong year 45% to 50% sales growth based on strength in global underlying Ag fundamentals, the estimated timing of deliveries of the large Egypt project and another record sales year in Brazil.
Overall, we continue to see strong demand and positive momentum across all businesses, evidenced by backlog of more than $1.3 billion at the end of second quarter and the demand drivers are in place to sustain this momentum into 2022.
As we discussed at our Investor Day, we remain focused on the execution of our strategy, which is fueled by our dedicated and talented team of 10,000 employees and our differentiated business model.

Summary:
Record sales of $894.6 million increased $205.8 million or nearly 30% compared to last year, an increase more than 26% on a constant currency basis.
Operating income of $90.9 million or 10% of sales grew $25.2 million or 38% compared to last year driven by higher volumes in irrigation, improved operating performance and a favorable pricing notably in Engineered Support Structures.
Diluted earnings per share of $3.06 grew more than 50% compared to last year, primarily driven by very strong operating income and a more favorable tax rate of 22.5%.
Further, we now expect Irrigation segment sales to grow 45% to 50% year-over-year and continue to assume a foreign currency translation benefit of 2% of net sales.
2021 adjusted earnings per share is now estimated to be between $10.40 and $11.10.
In Utility Support Structures, we expect a meaningful sequential improvement to the quality of earnings, beginning in the third quarter driven by margin improvement as pricing becomes more aligned with steel cost inflation.