Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2013
Publication Date: 4/1/2014
Citation: Brennan, E.B., Leap, J.E. 2014. A comparison of drill and broadcast methods for establishing cover crops on beds. HortScience. 49:441-447.
Interpretive Summary: Farmers need information on the most effective implements and methods for planting cover crops. This study compares drilling versus three different broadcast methods for planting cover crops on raised beds. The drill method produced the more uniform cover crop stands sooner after planting. Of the three implements used for incorporating broadcast seed into the soil, the cultivator and rototiller were preferable to the disc. However, with all broadcast methods, higher seeding rates are needed.
Technical Abstract: Cover crops 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 use broadcasting methods to establish cover crops but lack information on the most effective tool to incorporate the seed into the soil. Experiments were conducted with winter and spring sown cover crops to compare drilling versus 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 to broadcasting. The delayed emergence of broadcast seed was more 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 following 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.