Warren Buffett's uber long-term approach to investing is legendary, and because Buffett remains one of the globe's wealthiest people, investors might want to follow in his footsteps -- especially, given market volatility lately. With that in mind, let's learn more about Buffett's big buys last quarter.

No. 1: Kinder Morgan (KMI 0.40%)
It wasn't all that long ago that Buffett dodged a big drop in energy stocks by paring back his exposure to them; but with energy stocks collapsing, and bargains in the discount bin, Buffett is back to buying. Last quarter, the Oracle of Omaha stepped up and acquired 26,533,525 shares of Kinder Morgan, a big enough stake to make it worth $466 million of his Berkshire Hathaway's (BRK.B 0.21%) (BRK.A 0.36%) $123 billion portfolio.

It appears Buffett's timing was spot on. Shares in Kinder Morgan fell 63%, to $14.79 in 2015, and they've already rallied 16% since the start of the year. That's pretty darn good.

Buffett's decision to buy Kinder Morgan could have been made because he felt energy stocks fell too far too fast, and because he believed that production cuts would shore up per-barrel oil prices. The number of active rigs drilling for oil in North America dropped 56% in the past year, and major oil producing countries, including Saudi Arabia, recently announced plans to freeze oil production at January's level, further supporting crude oil prices.

The macro environment, however, may only be one reason why Buffett warmed up to Kinder Morgan. Traditionally, Buffett prefers that corporations spend cash on their businesses, rather than dividends, and that mantra dovetails nicely with Kinder Morgan's decision in December to shift money from dividends to debt repayment.

Only time will tell if the spike in oil prices, and Buffett's interest in Kinder Morgan, will be long lasting. In the past, Buffett has been willing to trade around in energy stocks; if investors follow Buffett into this one, they might want to watch it closely.

Source: Deere & Co.

No. 2: Deere & Co (DE 0.98%)
Also intriguing is Buffett's decision to increase his stake in the agricultural equipment maker Deere & Company.

Deere & Co sales are tightly tied to global economic growth, and with questions remaining in China and Europe, and rising interest rates creating uncertainty in the U.S., it would seem there's plenty of reason to be cautious -- especially when the company's management recently reported that fiscal first-quarter sales slumped 13% year over year, and that sales will slip by another 10% this year.

Yet, rather than taking a wait-and-see approach to the company, Buffett upped his position in Deere & Co to 22.88 million shares last quarter. Buffett's decision suggests he thinks a recovery in oil could coincide with a recovery in grains, like corn and wheat, that have also fallen significantly in the past year. Of course, no one knows if grain prices can hold their recent lows, climb, and fatten farmer wallets again; but if prices do improve, then Buffett's bet on Deere & Co could prove savvy.

No.3: Liberty Global plc (LBTYA -0.49%)
Berkshire Hathaway's 12.5-million-share position in Liberty Global plc -- up 5% from last quarter -- makes it Liberty Global's third largest shareholder. Because Buffett has steadily increased his ownership in Europe's biggest cable group during the past year, it seems he has plenty of confidence in Liberty Global's billionaire Chairman John Malone, and Malone's strategy to expand the company into mobile services.

Recently, Liberty Global announced it's teaming up with Vodafone in the Netherlands in a joint-venture that creates a quad-play services powerhouse, and previously, Liberty Global spent $1.3 billion acquiring Belgian mobile operator Base. Both of those moves give Liberty Global plenty of up-selling opportunities to fuel growth.

Historically, Buffett has been a big fan of free cash flow and strong management teams. Because Liberty Global's free cash flow is growing, and Malone is arguably the best operator in the industry, there's little reason to think Buffett will sell soon. That could make this stock worth adding to portfolios, too.