Boise-based J.R. Simplot Company will close a manufacturing plant in California, and separately close a number of its Simplot Grower Solutions locations. The company announced last year it would shut down its plant in Lathrop, California, just south of Stockton. The plant is part of the food and agriculture conglomerates Mining & Manufacturing division, and according to the company’s website, makes fertilizer, feed phosphates and industrial products.