D. Barbour
Analyst · Baird
Thanks, Mike. Good morning, everyone. Thank you for joining us on today's call. We had a strong second quarter of fiscal 2021, with 10% net sales growth as demand and business activity remain favorable. I want to thank the ADS and Infiltrator employees for their execution and diligence in making that happen. I also appreciate our customers for working with us in new and imaginative ways to serve the construction markets.
We generated strong performance in key growth states, including Florida, the Carolinas, Tennessee, Georgia and Utah as well as more broadly across the South and Southeast regions of the United States. As a whole, we benefited from our national presence and geographic exposure as well as our increased residential exposure from Infiltrator and the focused homebuilder programs at ADS.
Infiltrator once again exceeded revenue expectations with 63% sales growth in the second quarter. Infiltrator continues to see double-digit growth in tanks and leachfield products, with particular strength in Florida, the Carolinas, Georgia, Tennessee and Alabama. Recall, the Infiltrator results are for 2 months of the prior year quarter, given the timing of the acquisition, which closed July 31, 2019.
In the residential end market, legacy ADS sales increased 15% this quarter. We see favorable dynamics in new construction, repair/remodel and on-site septic. Orders, backlog and sales remained strong through the period, with very limited impact from the slowdown in residential starts earlier this year.
As a whole, we are well positioned for growth in the residential market. On the front end of the cycle, the ADS products and go-to-market strategy are positioned for the land development phase, whereas Infiltrator products come in play towards the end of the cycle when construction is nearing completion.
Additionally, both Infiltrator and ADS have a repair and remodel component that is strong and growing. Its home improvement activity and existing home sales continue to rise. About 1/3 of the Infiltrator sales are related to repair and remodel. And at ADS, the repair and remodel exposure is covered through our retail and national accounts. The company's exposure to the residential market has increased to 38% of domestic sales compared to 28% at this time last year.
Sales in our nonresidential end market were up modestly, led by strong growth in HP Pipe and Storm Tech retention/detention chambers as we continue to benefit from our exposure to horizontal construction. We are tracking very closely to the segments of the nonresidential market that continue to do well such as data centers and warehouses as well as geographies that are experiencing growth like the Southeast and Atlantic Coast.
Importantly, we believe ADS is well positioned to continue to grow above market due to our conversion strategy, national coverage and water management solutions package. And given what we see in the market today, we believe the second half of the year will be similar to the market conditions we experienced in the first 6 months.
Agriculture sales were down just slightly this quarter as we called out to a tough comparison period. Still, the agriculture sales team has had a great first half of fiscal 2021, with sales up 14% year-over-year. In addition, the fall selling season is off to a great start as we continue to benefit from the programs we put in place around organizational changes, new product introductions and improving execution in the agriculture market.
International sales increased 3%, driven by double-digit growth in our Canadian business. Canada is doing well across both the construction and agriculture end markets. Mexico, on the other hand, is not performing as well, having been more significantly impacted by the COVID-19 pandemic. Overall, strong demand is causing some regional- and product-level constraints. Lead time and inventory levels are stretched as we get into this part of the season.
Based on this strong demand and our desire to more fully capitalize on opportunities in our core end markets, we are stepping up our capital investments, which we now expect will total between $80 million and $90 million for this fiscal year. The focus of our investments will be to improve safety, increase capacity for future growth and improve productivity.
We will rebuild finished goods inventory in the second half of the year by level-loading production at our facilities in our traditionally slow months, preparing both ADS and Infiltrator for good customer service and normal lead times. This build will depend on our second half demand, ramping up new capital and dealing with the COVID-19-related circumstances like employee retention, absenteeism and local conditions. Frankly, this is consistent with the environment we've been managing since the pandemic hit.
We are also making investments in talent, including the recent addition of a senior leader to accelerate new product introductions, marketing and innovation. As highlighted in a press release this morning, we created a new product management and marketing organization to accelerate the development, launch and marketing of new products to meet customer needs. I'm pleased to announce Brian King joined our organization in September to lead this effort as the Executive Vice President of Product Management and Marketing. Brian has 25 years of successful product management experience, and we're excited to have him join our team.
Moving to our profitability results. We achieved another quarter of record adjusted EBITDA during the period. Adjusted EBITDA margin increased 820 basis points overall with a 640 basis point increase in the legacy ADS business. This was driven by favorable material cost, leverage from the growth in Pipe and Allied Products, execution of our operational initiatives and contributions from the proactive cost mitigation steps we took earlier this year.
Infiltrator also achieved record profitability in the quarter due to strong demand, favorable material costs, contributions from our synergy programs and continued execution of their proven business model. The synergy programs are right on track to achieve the run rate targets we've previously communicated.
As we look ahead to the second half of the year, we are optimistic as our order book, project tracking, book-to-bill ratio and backlog all remain positive. We expect the normal seasonal patterns to apply to the second half of our fiscal year as installation activity slows down in geographies with colder temperatures. We also have some profitability headwinds coming up in the third and the fourth quarters, including inflationary costs for materials and labor. We are working to offset these headwinds through pricing actions, operational productivity initiatives and our synergy programs.
In summary, we did a very good job executing this quarter. We're focused on safety, managing through the COVID-19 environment, servicing our customers and driving these new levels of profitable performance. Though uncertainty still exists regarding the broader market environment, we are well positioned to capitalize on residential development and horizontal construction, while continuing to generate above-market growth through the execution of our material conversion and water management solution strategies. We remain focused on disciplined execution as we look to build off a very strong first half of our fiscal 2021.
With that, I'll turn the call over to Scott Cottrill to further discuss our financial results.