Cumulative nitrogen inputs, exports and mass balances for 5 organic vegetable systems over eight years in Salinas, CA.

Systems differed by annual compost additions (0 vs. 7.6 Mg ha-1, oven-dry basis, before each vegetable crop), cover crop type (legume-rye, mustard, or cereal rye alone) and cover cropping frequency (quadrennially vs. annually planted). System 1 = no compost+legume-rye 4th year; System 2 = annual compost+legume-rye 4th year; System 3 = annual compost+legume-rye annually; System 4 = annual compost+mustard annually; System 5 = annual compost+rye annually.