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Pronamide [3,5‐dichloro (N‐l,l‐dimethyl‐2‐propynyl)‐benzamide], simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine], and 2,4‐D [(2,4‐dichlorophenoxy)acetic acid] were evaluated for management of species composition in established swards of alfalfa (Medicago sativaL.) which had become colonized by orchardgrass (Dactylis glomerataL.), Kentucky bluegrass (Poa pratensisL.), and dandelion (Taraxicum officinaleWeber). Dormant application of 2,4‐D ester reduced seedling dandelions, but did not affect mature dandelions, alfalfa stands, or yields. Simazine did not affect total yield or botanical composition of forage in this study. Pronamide application reduced bluegrass and total forage yield in the first harvest. The alfalfa component of the forage and total yield of alfalfa increased with pronamide treatments. Total forage yield for the season was the same for all treatments. Counts of alfalfa plants per m2were made for individual plots and multiple regression analysis was used to determine the association of percent alfalfa composition of the first harvest and plant density with alfalfa yield. In pronamide treated plots as few as 10 to 20 alfalfa plants per m2utilized resources made available by reduction of other species and produced acceptable yields. These results contrast to the 50 to 60 plants per m2commonly considered necessary for productive stands and suggest the possibility that herbicides may be used to extend the productive life of swards containing alfalfa.

The no‐tillage method is used extensively to produce doublecrop soybeans [Glycine max(L.) Merr.] planted after winter grain harvest. Success of this method depends on proper selection and effective application of herbicides for weed control in the second crop. Herbicides were evaluated in the field during three seasons for doublecrop soybean production following winter wheat (Triticum aestivumL.) harvest. Both residual herbicides and herbicides having activity only when applied to the foliage of green plants were evaluated alone and in various combinations in this study. The design of the experiment allowed a partitioning of the effects of herbicides having activity only when applied to foliage and utilized to control weeds present in the wheat stubble from the effects of residual herbicides employed to control growth of weeds emerging after soybean planting and herbicide application. During two seasons, herbicides having activity only when applied to foliage accounted for one‐half and two‐thirds of the yield response to weed control. Residual herbicides accounted for the other part of the yield response. In the third season, very few weeds were present in the wheat stubble at harvest and herbicides active only when applied to foliage had no effect on yield. During this season, effective residual herbicides increased yields significantly. Residual herbicide combinations that included linuton [3‐(3,4‐dichlorophenyl)‐l‐methoxy‐l‐methylurea] and metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐ 5(4H)‐one] were most consistent for weed control and crop yield. Both glyphosate [N‐(phosphonomethyl)glycine] and paraquat (1,1′‐dimethyl‐4,4′‐bipyridinium ion) generally were satisfactory as herbicides used to control existing vegetation. Some of the residual herbicides used in this study also exhibit considerable activity on foliage of plants present but at rates used this was inadequate for maximum crop yields.

On 0.4‐ to 3.5‐ha watersheds, highest concentrations of atrazine (0.48 ppm) (2‐chloro‐4‐[ethylamino]‐6‐[isopropylamino]‐s‐triazine) and simazine (1.2 ppm) (2‐chloro‐4,6‐bis[ethylamino]‐s‐triazine) were present in runoff occurring soon after application and declined rapidly for later events. Quantity of herbicides transported increased with the amount of runoff, and was inversely related to the length of time between application and the runoff event. A maximum of 6% of the applied herbicide was transported from the field even under the most favorable conditions, and the average for all watersheds was < 2%. Less runoff and herbicide loss occurred from areas planted to no‐tillage than to conventional corn (Zea maysL.). In a multiple regression analysis of the factors, the natural logarithm (ln) of days after application and a tillage × application rate interaction were useful in predicting the natural logarithm of herbicide concentration in runoff. Factors from the multiple regression analysis used in this study were important in predicting concentration of atrazine and other pesticides when applied to data published by other workers.

Dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) effectively controls many dicotyledonous weeds, but nontarget species such as soybean [Glycine max(L.) Merrill) are susceptible to spray or vapor drift. Field studies were conducted on a Canfield silt loam (fineloamy, mixed, mesic Aquic Fragiudalf) soil to determine the response of ‘Elf’ and ‘Williams’ soybean to dicamba over a wide range of applied rates, and to evaluate the use of dicamba injury symptoms to predict yield reductions. Soybean yield in response to increasing rates of dicamba was described by equations of the form y= Aexp( −bx), where y= yield, A= maximum yield (rate = 0 g ha−1), bis a constant, and x= rate of dicamba applied. Height reduction, seed number ha−1, and morphological symptoms of dicamba injury were useful in assessing yield reduction. Except for Elf soybean treated at the midbloom stage, there was no yield reduction without height reduction, regardless of foliar symptoms. Seed number ha−1decreased with increasing rates of dicamba and was closely correlated with yield. Yield reductions greater than 10% were indicated by severe morphological symptoms of injury, such as terminal bud kill, splitting of the stem, swollen petioles, and curled, malformed pods. Other foliar symptoms, such as distinctive crinkling and cupping of the terminal leaves, occurred at rates much lower than those required to cause yield reductions.

Soybeans (Glycine max.L.) apparently predispose a field to greater erosion by water than does corn (Zea maysL.) at equal residue cover. Most of the available data have been obtained from locations with 5 years or less history of a specific management. This study measured soil loss during simulated rainfall from plots having an 18‐yr history of management to ascertain deviations, if any, from current expectations. The soil was a fine‐loamy, mixed mesic, Typic Fragiudalfs having an average slope of 3%. Tillage variables included no‐tillage, spring plow 20 cm deep, and spring plow 20 cm deep followed by 10 cm deep disking or equivalent. Rotations were continuous corn or corn‐soybeans. Kinetic energy of applied water was about 70% of natural rainfall at 63 mm/h rate. Runoff and soil loss were measured at 60‐s intervals during the 30‐ to 60‐min runs. Soil loss per unit of rainfall following either crop in the corn‐soybeans rotation was 45% greater than from continuous corn, after accounting for differences in residue cover by use of the Universal Soil Loss Equation (USLE). Soil loss per unit of rainfall for land not tilled for 1 or over 20 years was 90% less than expected according to the current version of the USLE.

Studies to compare the relative ability of a wide range of tillage and crop rotation combinations (3×3 factorial) to sustain corn (Zea maysL.) production on several soils typical of Ohio were initiated in 1962. Soils were a well‐drained Wooster silt loam (Typic Fragiudalf), an imperfectly drained Crosby silt loam (Aeric Ochraqualf), a very poorly drained Hoytville silty clay loam (Mollic Ochraqualf), and a very poorly drained Toledo clay (Mollic Haplaquept). Tillage treatments were no‐tillage; plow and then plant; and plow, disk, and plant. Rotations were continuous corn, corn‐soybeans, (Glycine maxL.) (2 year), and corn‐oats (Avena sativaL.)‐meadow (3 year) with each crop appearing each year in each rotation. Results are reported only for plots having equal plant density within a site‐year combination, and adequate weed control. Corn yields were remarkably insensitive to tillage. The two plowed treatments had equal yield for virtually all years at each site within the same rotation. The no‐tillage treatment averaged 975 kg/ha or 13% lower yield than the average of plowed treatments on the Mollic Ochraqualf soil for 10 years of continuous corn, but had the same yield as the plowed treatments for the other two rotations. The no‐tillage treatment averaged 750 kg/ha or 10% greater yield than the average of plowed treatments on the Typic Fragiudalf soil for 11 years of continuous corn or corn‐soybeans rotation. Otherwise tillage treatments generally produced the same corn yield within site‐rotation combinations.

A field experiment was conducted over a period of six cropping years to determine the relative merits of basic cation saturation ratio (BCSR) and of sufficiency level of available nutrients (SLAN) as bases for a p plying lime (Ca and Mg) and fertilizer K for crops. The study involved an acid Loudonville silt loam soil (Ulfic Hapludalf, fine‐loamy, mixed, mesic) which had been adjusted to 3 pH (Ca), 3 Mg, and 2 K levels, in all combinations. The sequentially grown crops were: corn (Zea maysL.), corn, soybeans (Glycine maxL. Merr.), wheat (Triticum aestivumL.), alfalfa (Medicago sativaL.), and alfalfa. The treatment variables for pH were: 5.0, 6.0, and 6.5; for percent Mg saturation of soil CEC were: 4, 6, and 10; and for percent K saturation of CEC were 2.4 and 4.3. Both yields and crop compositions were measured. The treatment variables resulted in an average soil Ca/Mg ratio range of 2.3 to 26.8 and an average soil Mg/K ratio range of 0.6 to 3.6. Direct correlation or association of crop yields with basic cation saturation ratios (BCSR) were quite low. Also, the treatments producing the five highest yields for each crop gave rather wide ranges in both Ca/Mg and Mg/K ratios which were to a large extent also common to those ratios associated with the five lowest yielding treatments. Thus, finding no evidence to support the validity of the BCSR concept as a basis for providing maximum crop yield conditions, the direct response of the crops to the basic nutrient cations (SLAN) concept was examined. Although yield responses to increased levels of the cations were not obtained in all cases, the results obtained were reasonable; and compositions of Ca, Mg, and K were in almost all cases increased as the levels of the respective cations were increased. The results strongly suggest that for maximum crop yields, emphasis should be placed on providing sufficient, but nonexcessive levels of each basic cation rather than attempting to attain a favorable BCSR which evidently does not exist.

Glyphosate (N‐[phosphonomethyl]glycine)3formulated as Round‐up® herbicide,4was applied on 0.3‐ to 3.1‐ha watersheds at rates of 1.10‐, 3.36‐, and 8.96‐kg/ha as a preseeding herbicide in the no‐tillage establishment of rescue (Festuca arundinaceaL.) and corn (Zea maysL.). Runoff from natural rainfall following early springtime treatments was measured and analyzed to define concentration and transport of glyphosate under these conditions. The highest concentration of glyphosate (5.2 mg/liter) was found in runoff occurring 1 day after treatment at the highest rate. Glyphosate (2 µg/liter) was detected in runoff from this watershed up to 4 months after treatment. For the lower application rates, maximum concentration of the herbicide in runoff was < 100 µg/liter for events occurring 9–10 days after application and decreased to <2 µg/liter within 2 months of treatment. The maximum amount of glyphosate transport by runoff was 1.85% of the amount applied, most of which occurred during a single storm on the day after application. In each of the three study years, herbicide transport in the first runoff event following treatment accounted for 99% of the total runoff transport on one watershed. Glyphosate residues in the upper 2.5 cm of treated soil decreased logarithmically with the logarithm of time; they persisted several weeks longer than in the runoff water.

Corn was grown for 3 years on Wooster silt loam, a soil on which the yield response of corn to cultivation exceeds that attributable to weed control. Treatments included conventional preplant tillage (plowing, disking) and no preplant tillage with three corn stover residue levels, 5% cover (stover removed), 45% cover (stover left in place), and 70% cover (double level of stover). Except for the first year when the tilled plots were not cultivated, grain yields with 45% cover (6,170 kg/ha) equalled the tilled check (5,970 kg/ha). Yields of treatments with 5% cover were significantly lower (4,770 kg/ha) than the tilled treatment and significantly higher with 70% cover (6,625 kg/ha). Soil moisture determined with gypsum blocks during the last 2 years was greater with increasing amounts of soil cover during the growing season. Soil cover did not increase during the experiment, even on treatments receiving double residue. At the end of the third year, water infiltration as determined with a sprinkling infiltrometer was significantly greater with 80% cover than for the other treatments. Results from these experiments indicate that mulch protection which may be readily available from previous crop residues is necessary to maintain no‐tillage corn grain yields on this and similar areas of Wooster silt loam. The beneficial effects of the mulch seem to be associated with increased soil moisture.

Neither grass nor legume intercrops improved corn or soybean yields where adequate nitrogen was supplied and where erosion was not a problem. Corn yields in continuous culture were maintained at a high level over a 6‐year period if adequate nitrogen was provided. Soybean yields were maintained whether or not nitrogen was applied. Legume intercrops supplied nitrogen to continuous corn not fertilized with nitrogen, but not enough to produce yields comparable to corn after a year of a legume meadow.

Relative effects of soil mulch cover and various tillage practices on corn (Zea maysL.) yield were studied as functions of previous crop and rainfall on a typic fragiudalf soil. Residues (mulch from previous crops of corn or tall fescue) were removed from the soil prior to tillage, manipulated according to action of the tillage implements, or replaced on the soil surface after tillage. Eight tillage treatments consisted of all possible combinations of moldboard plowing, disking, and post emergence cultivation. Mulch cover produced three times as great a yield effect as any other single variable, with the effect (kg/ha) = 36.2M − 0.00218 MS, where M is percent of the soil surface covered with mulch and S is yield in kg/ha of the plowed plus cultivated treatment. Tillage variables increased yield in order of cultivation > plow > disk, and results are expressed in terms of mulch cover required to produce an equal yield effect. Most tillage and mulch effects were additive. The major reason for mulch and tillage effects on corn yield is assumed to be their influence on soil water content. Possible extrapolation of these results to other soils and climates is discussed.

Corn was grown for 3 years following sod, using herbicides rather than tillage to destroy the vegetation. Several herbicide mixtures and rates were used in these experiments to determine materials and rates necessary to destroy vegetation and eliminate growth of weeds from seed present in the soil without injury to the corn plants. Several herbicide systems were satisfactory. Most of these contained atrazine or simazine for control of perennial grasses and annuals and 2,4‐D or similar herbicides for destruction of broadleaf perennials.