From the “Petroleum Highway” — a rutted, dusty stretch of California State Route 33 — you can see the jostling armies of two giant industries. To the east, relentless rows of almonds and pistachios march to the horizon. To the west, an armada of oil wells sweeps to the foothills of the Temblor Range.

Fred Starrh, who farms along this industrial front, has seen firsthand what can happen when agriculture collides with oil. On an overcast February day, he drives his mother-of-pearl Lincoln Town Car down a dirt road through his orchards. Starrh Farms has 6,000 acres of pistachios, cotton, almonds and alfalfa. Starrh proudly points out almond trees planted 155 to the acre with the aid of lasers and GPS. At the edge of his land, he pulls up beside 20-foot-high earthen berms, the ramparts of large “percolation” ponds that belong to a neighbor, Aera Energy.

From the mid-1970s to the early 2000s, Aera dumped more than 2.4 billion barrels (or just over 100 billion gallons) of wastewater — known in the industry as “produced water” — from its North Belridge oilfield into those unlined ponds, Starrh says. The impact became apparent beginning in 1999, when Starrh dug several wells to augment the irrigation water he gets from the California Aqueduct. He mixed the groundwater with aqueduct water, applied it to a cotton field beside the berms — and the plants wilted. Eventually, the well water killed almond trees, Starrh says; he points out a few that look like gray skeletons.