|Mueller Warrant, George|
Submitted to: Journal of Applied Seed Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/1996
Publication Date: N/A
Interpretive Summary: Two varieties of the perennial legume crownvetch were established for eventual seed production in the north island of New Zealand at seven different sowing dates. Similar to results in the United States, successful weed control was critical for good seed production in the first year after planting. Injury from a herbicide treatment applied to some, but not all of the sowings, had a dramatic impact on seed production reducing yield by 81% for the more sensitive variety. However, weeds that appeared in some of the untreated plots, and were therefore not controlled, also greatly reduced seed yield. Clipping crownvetch in midspring to simulate grazing reduced seed production an average of 55%. Because of the pattern of seed development in crownvetch, the highest yielding treatments were those that flowered the earliest and maintained a high density of flowers during a critical period from 30 to 60 days before harvest.
Technical Abstract: Seeding establishment, weed control, flowering patterns, and seed yield were determined for 2 crownvetch cultivars (G-34 and Aokautere) sown monthly between 10/93 and 4/94, with and without defoliation in early 11/94, and with and without the herbicide chlorimuron on 8/16/94. Crownvetch seedling densities were highest with March and April sowings, lowest with January sowing, and intermediate with the other sowings, corresponding to differences in rainfall soon after sowing. Defoliation in spring 1994 resulted in an average 12-day delay in flowering onset, 39% reduction in peak inflorescence density, and 55% reduction in seed yield. August application of chlorimuron controlled broadleaf weeds well, but reduced crownvetch dry matter production in the spring, delayed flowering, reduced the number of inflorescences m**-2, and reduced seed yield. Without chlorimuron treatment, Aokautere produced more dry matter in early spring than G-34, but Aokautere was also more sensitive to injury from chlorimuron. Peak flowering occurred approximately 30 days after flowering onset in most plots. Duration of flowering at greater than half-maximum density varied with treatment from 23 to 48 days, while the period from flowering onset to harvest varied from 63 to 93 days. G-34 must be sown by February for maximum seed yield the following summer, whereas Aokautere sown in March produced at least as well as with earlier sowing. G-34 produced more seed than Aokautere in 1995, the establishment year, while Aokautere outyielded G-34 in 1996, the 2nd year of production, by 31%.