A Comparison of Drill and Broadcast Methods for Establishing Cover Crops on Beds

Abstract

Cover crop stands that are sufficiently dense soon after planting are more likely to suppress weeds, scavenge nutrients, and reduce erosion. Small-scale organic vegetable farmers often broadcast cover crop seed to establish cover crops but lack information on the most effective implements to incorporate the seed into the soil. Experiments were conducted with winter- and spring-sown cover crops to compare drilling vs. broadcasting methods for establishing rye (Secale cereale L.) mixed with either purple (Vicia benghalensis L., winter) or common vetch (V. sativa L., spring) on bed tops at a seeding rate of 140 kg·ha−1 in Salinas, CA. Broadcast seed was incorporated with a rototiller, cultivator, or tandem disc. Cover crop stand uniformity was assessed visually, and cover crop emergence over time and seeding depth were measured. Stands were more uniform after drilling or broadcast + rototiller incorporation compared with the other methods. Cover crops emerged sooner and in higher densities after drilling compared with broadcasting. The delayed emergence of broadcast seed was most apparent during the cooler winter experiment, particularly with purple vetch. Most drilled seed emerged from 2-cm depth compared with the broadcast seed that emerged from up to 11-cm depth with the greatest variability after disc or rototiller incorporation. The data indicate that the cultivator and rototiller are preferable implements to incorporate broadcast seed on beds, but that 50% to 100% higher seeding rates for broadcasting than drilling are needed. The practical implications for weed and soil management, and planting costs are discussed.