Establishment of Alfalfa by Conventional and Minimum‐Tillage Seeding Techniques in a Quackgrass‐Dominant Sward1

Abstract

AbstractMinimum‐tillage establishment of forages offers potential advantages over the conventional method in terms of reducing energy and labor requirements, erosion hazard, and improving flexibility, and timeliness of operation. Our objective was to compare these methods of establishing alfalfa (Medicago sativa L.) with various herbicides, time intervals between herbicide application and seeding, and seeding dates. The seedings were established on a Charlton fine sandy loam (Entic Haplorthod) of high fertility in a sward dominated by quackgrass (Agropyron repens L.). Conventional renovation consisted of plowing, disking, cultipacking, and seeding; minimum‐tillage renovation consisted of mowing and seeding with a J. D. Powrtill seeder.Delaying application of glyphosate IN‐(phosphonomethyl) glycine] from 2 to 16 May had no apparent effect upon quackgrass control, but did lead to a significant reduction (52%) in densities of alfalfa seedlings and, subsequently, of second year alfalfa plants in plots seeded 21 May 1977 by minimum‐tillage. At the first harvest of the seeding year, a delay in glyphosate application resulted in significantly lower forage yield (1.84 vs. 2.82 metric tons/ha) and higher percent crude protein (20.0 vs. 16.8%) for the 21 May and 4 June minimum‐tillage seedings. In subsequent harvests, there were no yield differences due to glyphosate application date for alfalfa established by minimum‐tillage. Date of glyphosate treatment did not affect plant densities, forage yield, or quality of conventionally‐seeded alfalfa.For glyphosate treatments, conventional seeding resulted in an average of 0.6 metric tons/ha more alfalfa than minimum‐tillage during the seeding year. Yields of total forage and alfalfa seeded by the two techniques after glyphosate treatment were similar during the second year, except that yields for conventional seeding continued to be higher than for minimum‐tillage for the 4 June seeding (9.2 vs. 8.5 metric tons/ha of alfalfa).In terms of alfalfa and total forage yields, glyphosate was more important for minimum‐tillage than for conventional seedings. EPTC (S‐ethyldipropylthiocarbamate) produced yields similar to glyphosate with conventional seeding, while with paraquat (l,l'‐dimethyl‐4,4'‐ bipyridinium ion) yields were similar to those with glyphosate only at the earliest minimum‐tillage seeding. Seeding without herbicide led to substantial yield reductions, especially with minimum‐tillage seedings.