Soybean [Glycine max (L.) Merr.] grown without tillage often produces less grain on silty clay loam soils than soybean produced under conventional tillage. A 3‐yr (1982, 1983, and 1984) study was conducted to gain a better understanding of the factors affecting yield differences between conventional and no‐till soybean production systems on silty clay loam soils. The study was conducted near Columbia, MO, on a Mexico silt loam soil (Udollic and Mollic Ochraqualf). Conventional tillage consisted of spring moldboard plowing and secondary tillage. The no‐till treatment received a foliar application of glyphosate [N‐(phosphonomethyl) glycine] at the time of planting. Soybean grain yields were less for no‐till in 1982 (1890 kg/ha vs. 2260 kg/ha) and greater in 1983 (2310 kg/ha vs. 1510 kg/ha) and 1984 (1870 kg/ha vs. 1670 kg/ha). Seasonal rainfall was above average in 1982 and below average in 1983 and 1984. In 1983 and 1984, soybean in the no‐till plots depleted greater soil moisture at soil depths of 840 and 990 mm and had less plant water stress during podfilling, with afternoon leaf water potential measurements averaging 0.11 MPa greater in 1983 and 0.34 MPa greater in 1984, than soybean grown under conventional tillage. Conventionally tilled soybean had a greater yield potential due to greater vegetative growth, but with less than adequate rainfall the soybean in no‐till had less plant water stress, resulting in greater yields.

A 3-yr (1982, 1983, and 1984) study was conducted to determine the relationship between tillage and six weed control treatments for soybean [Glycine max(L.) Merr. ‘Williams 79′] production on silt loam (Udollic and Mollic Ochraqualfs). Conventional tillage consisted of spring moldboard plowing and secondary tillage with a combination tool just before planting. No-tillage consisted of a foliar application of glyphosate [N-(phosphonomethyl)glycine] at the time of planting. Weed control treatments included combinations of no weed control with and without soybean plants, preemergence herbicide application only, postemergence herbicide application only, and combined preemergence and postemergence applications with and without additional handweeding. In 1982, a year of above-normal seasonal rainfall, conventional tillage had significantly greater soybean grain yields than no-tillage for all weed control treatments except the preemergence-only treatment. Yields within tillage systems and between weed control treatments in 1982 were not significantly different because adequate rainfall reduced the effect of weed competition for soil moisture. Soybean seed yields in 1983 and 1984 in no-tillage were equal to or significantly greater than those of conventional tillage. No-tillage treatments had greater soil moisture conservation and soil moisture availability resulting in less plant water stress during podfilling in periods of drought in 1983 and 1984. In all 3 yr, conventional tillage had significantly greater early weed growth than no-tillage in the treatments with and without soybean plants where no preemergence or postemergence herbicides were used. Comparing treatments with and without soybean plants indicated an average increase of 36 and 38% weed control for no-tillage and conventional tillage, respectively.

‘Emerald’ crownvetch (Cornilla varia L.) and ‘Viking’ birdsfoot trefoil (Lotus corniculatus L.) were sod‐seeded into permanent bluegrass pastures. Three types of sod openers were evaluated along with the use of paraquat sprayed in a 15‐cm band over the seeded row to reduce competition from the existing sod. Forage production from these sod‐seeded treatments was compared with complete renovation and seeding to a mixture of orchardgrass (Dactylis glomerata L.), ladino clover (Trifolium repens L.) and red clover (Trifolium pratense L.) and to three rates of nitrogen topdressing on the undisturbed sward. All of the treatments significantly increased forage yields with annual applications of N at 448 kg/ha being the highest. However, such a practice is not economically practical at present. Sod‐seeding with crownvetch was as good as either complete renovation or 140 kg N/ha annually. Sod‐seeded trefoil was less productive but in the third year of the study it was higher yielding than complete renovation. Based on dry matter yields, birdsfoot trefoil and crownvetch offer good possibilities for improving permanent pastures production at minimum cost. These legumes can be seeded and the pasture fertilized in one trip over the field. Crownvetch is especially well suited to this type of seeding because of its spreading growth habit. The disk and disk‐spear openers were generally superior to the spear only. However, with crownvetch the spear plus paraquat was also satisfactory.

Herbicides and interim summer crop treatments were studied in 1984 to 1987 to replace fungal endophyte-infected with endophyte-free tall fescue or red clover to improve forage quality. Foliar glyphosate or paraquat were applied in spring across interim crops with PRE herbicides. The interim crops, grain sorghum with atrazine, sorghum-sudangrass hybrid with metribuzin, or soybean with imazaquin, were each applied as confounded treatments across glyphosate or paraquat. Within an interim crop system, a follow-up glyphosate treatment was serially applied the next fall or spring. Then either red clover or endophyte-free tall fescue was spring drilled within the fall or spring glyphosate follow-up treatments. Glyphosate controlled old tall fescue better than paraquat, and improved the stand of the endophyte-free tall fescue. Control of tall fescue was 97% from 1.7 kg ai/ha glyphosate. Glyphosate reduced the endophyte from a 77% original infection level to 20% over all interim crops after drilling the endophyte-free tall fescue. Among interim crops, grain sorghum or the sorghum-sudangrass hybrid was more competitive than soybean with the uncontrolled tall fescue. Replacement with endophyte-free tall fescue was best in grain sorghum or sorghum-sudangrass hybrid stubble the next spring. Grain sorghum or sorghum-sudangrass hybrid following foliar glyphosate or paraquat treatment of endophyte-infected tall fescue reduced endophyte infection level in tall fescue to 28%. A follow-up fall treatment with glyphosate controlled tall fescue better than the spring retreatment and red clover and endophyte-free tall fescue were established better from fall retreated glyphosate. Red clover was easily established by drilling into the sod after treating endophyte-infected tall fescue with either glyphosate or paraquat.