Watering the Cracks

We haven't had much rainfall for weeks. Dust clouds follow the sheep as they trot to the faraway alfalfa field. Each evening, I check my little patch in the garden where I planted spinach seeds. The plants aren't quite an inch high. As I water them, I gaze at the cracks that snake through the garden, threatening to gobble up those tender young plants. How much water would it take to fill those cracks?