Table 2 presents yield trial results over several locations and years in Missouri. The results show a positive response to drilling when yields are averaged over a large number of varieties. In dry situations, however, such as those encountered at Columbia in 1980 and 1983, drilled seeding did not increase average yields. Good early season weed control is essential until the canopy develops. This requirement places a high reliance on herbicides for weed control and may make the use of narrow rows on some weedy fields undesirable.
Perennial weeds are difficult to control without some cultivation.
By the time the perennials overtop the soybeans sufficiently to be treated, tractor wheels will probably damage soybean plants. So fields with many perennial weeds may be unsuitable for solid seeding. Seed costs increase. Emergence may be poorer in drilled seeding because planting depth is less uniform and because each seedling must emerge on its own. Rotary hoeing also reduces stand.