Soybean Stubble Research Articles

Automated Bale Mapping Using Machine Learning and Photogrammetry

An automatic method of obtaining geographic coordinates of bales using monovision un-crewed aerial vehicle imagery was developed utilizing a data set of 300 images with a 20-megapixel resolution containing a total of 783 labeled bales of corn stover and soybean stubble. The relative performance of image processing with Otsu’s segmentation, you only look once version three (YOLOv3), and region-based convolutional neural networks was assessed. As a result, the best option in terms of accuracy and speed was determined to be YOLOv3, with 80% precision, 99% recall, 89% F1 score, 97% mean average precision, and a 0.38 s inference time. Next, the impact of using lower-cost cameras was evaluated by reducing image quality to one megapixel. The lower-resolution images resulted in decreased performance, with 79% precision, 97% recall, 88% F1 score, 96% mean average precision, and 0.40 s inference time. Finally, the output of the YOLOv3 trained model, density-based spatial clustering, photogrammetry, and map projection were utilized to predict the geocoordinates of the bales with a root mean squared error of 2.41 m.

Elk (Cervus elaphus) grazing reduces volunteer soybean density

Management of glyphosate resistant volunteer soybean can be challenging and costly in other glyphosate resistant crops. This study examined the effect of elk (Cervus elaphus) grazing on volunteer soybean (Glycine max) management. Volunteer soybean density was assessed in four fields grazed by elk and three without elk in western Manitoba, Canada. This study determined that elk grazing of soybean stubble significantly reduced soybean volunteer density in the following crop. These results demonstrate that winter elk grazing can be an effective management technique for volunteer soybeans.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ ПЛУГА З ДИСКОВИМ ПОДРІБНЮВАЧЕМ

Studies were conducted on the operation of a plow with a disk disintegrator in a unit with an MTZ-82 tractor on black soil with a flat relief on soybean stubble with the amount of plant residues from 300 to 400 g/m2. During the research, the following parameters were changed: the disk approach angle, the disk section installation height, and the tractor speed. As a result of the study, it was found that at the speed of a plow with a disk disintegrator from 4 to 5 km/h, the depth of plant residues embedding is maximum and ranges from 15 to 19 cm, while fuel consumption becomes minimal in the range from 18 to 30 kg/ha.

Plant volatiles guide the new pest Dichelops furcatus to feed on corn seedlings.

Recently, in temperate and neotropical regions of South America the generalist stink bug Dichelops furcatus (Hemiptera: Pentatomidae) became a new pest of corn (Zea mays) seedlings. Implementation of no-tillage cultivation system left organic matter covering the soil, which shelters adults of stink bugs during winter. In spring, corn is sowed under soybean stubble and D. furcatus adults start to feed on seedlings. To determine corn-derived volatile organic compounds (VOCs) that attract this stink bug species, we evaluated stink bug preferences from two corn hybrids with contrast germplasm backgrounds, a temperate and a tropical hybrid. Stink bugs preferred to feed on temperate seedlings rather than on the tropical ones. GC-MS and PCA analysis of VOCs suggested that hybrids emitted contrasting blends. Linalool represented 68% of total VOCs emitted from temperate corn, while in the tropical hybrid this compound represented 48%. Olfactometer experiments demonstrated that linalool was attractive to stink bugs. However, 2 h of D. furcatus attack induced emission of 14 additional VOCs in temperate seedlings, and olfactometer bioassay and blend of VOCs emission suggested that perceived volatiles by stink bugs induced feeding avoidance. The increment of VOCs emission was associated with the induction of JA, JA-Ile, ABA, and IAA, and decreasing of SA concentrations. This is the first time showing a complete profile of defensive phytohormones induced by stink bugs feeding on corn, and further demonstrating that a blend of corn seedling-associated VOCs, mainly composed by linalool, modulates D. furcatus adults' behavior and feeding preferences. © 2021 Society of Chemical Industry.

Crop and stubble effects on seedling emergence of sourgrass, palmer amaranth, wild radish and fleabane

Crop diversity, crop structures and crop residue can modify the seed-bank environment, influencing the seedling emergence of some weeds. The objectives of this work were to analyse (1) the effect of winter crop canopies of canola and wheat and soybean stubble on seedling emergence of Conyza sumatrensis and Raphanus sativus and (2) the effect of different soybean crop structures and soybean stubble on Digitaria insularis and Amaranthus palmeri seedling emergence. Two different field experiments were conducted at Buenos Aires University in a completely randomised factorial design with five replicates. The two winter species showed differences in the emergence timing whereas the two summer species emerged at the same time but with differences between years. Seedling emergence of A. palmeri was reduced by the presence of crop residue while the effect on C. sumatrensis and R. sativus emergence were more variable between years and D. insularis was not affected. Crops did not affect seedling emergence of winter species or that of A. palmeri. However, D. insularis emergence was favoured by soybean presence, mainly with closer canopy structures. Management decisions that promote the presence of crop residues favour the reduction of seedling emergence of palmer amaranth. In contrast, evaluated crop plant densities and planting dates were not able to reduce the seedling emergence of C. sumatrensis, R. sativus and D. insularis. Planting soybean in more competitive crop structures with closer canopies is not a good option due to the improvement of seedling emergence of D. insularis. Crop management decisions that inhibit seedling emergence in some species could stimulate it in others.

Ammonia and Greenhouse Gas Concentrations at Surfaces of Simulated Beef Cattle Bedded Manure Packs

Abstract. Bedding is used in livestock operations to facilitate manure management and provide comfort for the animal. Our research objective was to determine differences in ammonia (NH 3 ), carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane (CH 4 ) concentrations from simulated beef cattle bedded manure packs (BP) related to storage length (0 to 3, 3 to 6, and 6 to 9 weeks), bedding material (corn stover (CS) or soybean stubble (SB)), and temperature (10°C or 40°C). Bedding, fecal material, and urine were added weekly to 24 laboratory-scale BP (n = 2 per treatment combination). Static flux chamber samples from BP headspace were analyzed for CO 2 , N 2 O, and CH 4 at 0, 24, 46, and 144 h and for NH 3 at 0, 5, 9, 23, 34, 46, and 144 h after weekly manure and bedding addition for three consecutive weeks using a doubly repeated measures design. Ammonia concentrations were three times higher above BP in the Hot chamber (1190 ppm, SE = 47) compared to the Cold chamber (400 ppm, SE = 9). Average concentrations for CO 2 (6033 ppm, SE = 211), CH 4 (42 ppm, SE = 4), and N 2 O (0.61 ppm, SE = 0.05) were approximately twice as high at 40°C as for CO 2 (3902 ppm, SE = 161), CH 4 (21 ppm, SE = 2), and N 2 O (0.39 ppm, SE = 0.03) at 10°C. At 40°C, NH 3 concentrations above CS treatments (1388 ppm, SE = 75) were higher than above SB treatments (992 ppm, SE = 51). Overall, a higher storage temperature increased all gas concentrations. Increases in concentrations with length of storage were detected for CH 4 and CO 2 , while bedding affected NH 3 at 40°C and impacted changes in increase for CH 4 concentrations. These data suggest that seasonal management decisions can impact gas production and release in barns using BP. During hot months, NH 3 , CO 2 , CH 4 , and N 2 O concentrations are expected to increase and when applying CS as the bedding, NH 3 concentrations will likely be higher with CS bedding compared with SB bedding. At temperatures around 10°C, CO 2 and CH 4 concentrations are anticipated to increase with longer storage lengths.

Abundance and Distribution of Overwintering Red-tailed Hawks and American Kestrels in an Agricultural Landscape in Northeastern Arkansas

Abstract Although Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) are common raptors in the U.S.A., their wintering population abundance and distribution has not been studied recently in Arkansas. We assessed the temporal and spatial variation in population abundance of Red-tailed Hawks and American Kestrels over the winter in northeastern Arkansas. We conducted weekly surveys from an automobile in Craighead and Poinsett counties, Arkansas, October 2012–March 2013. Abundance of Red-tailed Hawks (n = 854 total observations) and American Kestrels (n = 165 total observations) along the transect increased during winter months. The overall abundance indices were 7.05 Red-tailed Hawks per 10 km (highest ever recorded) and 1.36 American Kestrels per 10 km. We found no significant differences in the utilization of the various cover types (i.e., short rice stubble, soybean stubble, and fallow areas/roadsides) for either species. However, both species differed in their use of perch...

Perch-type Characteristics of Overwintering Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius)

Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) are primarily sitand-wait predators that rely on perches to forage most efficiently. Overwintering Red-tailed Hawks and American Kestrels use available perches (e.g., utility poles and wires, trees, fences, gates, etc.) to hunt for prey items in agricultural fields in northeast Arkansas. Observations were made from December 2011-March 2012 and November 2012-March 2013 in three representative cover-types (short rice stubble, soybean stubble, and fallow areas including roadsides) to determine which perch-types were used by Red-tailed Hawks and American Kestrels. Utility pole crossbeams at an average height of 6.3 m were the main perchtypes used by Red-tailed Hawks, demonstrating the use of man-made structures’. These perches were generally in or near fallow areas or short rice stubble fields. Conversely, American Kestrels usually perched on wires at an average height of 4.9 m, over fallow roadsides’. Fallow areas had high prey density and vegetation cover. Niche separation via differential use of perches may be one factor that allows these raptors to avoid inter-specific competition.

Effects of Crop Stubble on Physicochemical Properties of Continuous Cropping Soil and Cucumber Yield and Quality

By a pot experiment, two kinds of crop stubble (wheat, soybean) were added into continuous cropping soil of cucumber according to different quantity (0.5%, 1% and 2%), the effects of different kinds of stubble and quantity on the continuous cropping soil and growth of cucumber were investigated. The results showed that two kinds of crop stubble significantly decreased soil bulk density, and increased total porosity of soil. Each of all treatments significantly decreased the accumulation of salinity in soil within the entire growth period of cucumber. 2% wheat stubble treatment had the biggest drop in soil EC in the later period of cucumber growth. Soybean stubble treatment had the lesser effect on soil EC. Wheat and soybean stubble promoted the growth of cucumber, increased the yield of cucumber, and improved the quality of cucumber. 2% of wheat stubble treatment had a biggest increase in cucumber yield, which increased the yield by 34.23% compared with the control.

Runoff Nitrogen Loss with Simulated Rainfall Immediately Following Poultry Manure Application for Corn Production

Nitrogen loss from a soybean [Glycine max (L.) Merr.]–corn (Zea mays L.) rotation by runoff to surface water can be significant. This study was conducted to determine short‐term N loss in runoff immediately after poultry manure application and assess the effects of manure rate and incorporation on losses. The study was conducted for 3 yr at nine Iowa fields previously cropped to soybean. Poultry manure sources were applied in the fall or spring to untilled soybean stubble at intended rates of 0, 84, and 168 kg total N ha−1with three replications. Within 2 d of application, simulated rainfall was applied to 3‐m2 areas to provide a single 30‐min runoff event. The total Kjeldahl N (TKN) and NH4+–N concentration and load in runoff increased with higher manure rates, with the associated manure TKN and NH4+–N correlated with runoff losses. With the high manure rate, runoff TKN and NH4+–N concentration averaged 33 and 15 mg L−1 and the TKN and NH4+–N load 2.6 and 1.1 kg ha−1, respectively. Runoff concentration and load of TKN and NH4+–N was significantly decreased with incorporation, approximately 50% and 90%, respectively. Tillage increased TKN in runoff when no manure was applied, but loses were lower than the treatment with manure and incorporation. The NO3−–N load in runoff was low and not affected by manure application. The results show that rainfall shortly after surface application of poultry manure can result in increased runoff TKN and NH4+–N, with loss related to manure rate, specific N fraction, and incorporation, which significantly reduced manure N in surface runoff.

Soybean Residue Effect on Carbon Fractions and Gaseous Nitrogen Losses at Contrasting Moisture Contents

Most published studies related to crop effects on denitrification are not continuous and are based on the growing period. The objective of this work was to evaluate the effect of different amounts of soybean stubble, under different soil moisture contents, on gaseous nitrogen (N) losses by denitrification from an agricultural soil. The following soil moisture treatments were reached by adding distilled water to soil cores of a typic Hapludoll: 50 and 100% of water‐filled porosity space (WFPS). Residue treatments included no application of residues, amendment with 2600 kg ha−1 of soybean residues, and amendment with 5200 kg ha−1 of soybean residues. Cumulative nitrous oxide + dinitrogen (N2O + N2) emissions displayed great variability, ranging between 0 and 581.91 µg N kg−1, which represented 0 to 3.93% of the N residue applied. Under 50% WFPS moisture conditions, statistical differences in cumulative N2O + N2 emissions between residue treatments were not detected (p = 0.21), whereas at saturation conditions, cumulative N2O + N2 emissions decreased with the application of increasing amounts of soybean residues (p = 0.017). Daily and cumulative N2O + N2 emissions significantly increased as soil moisture increased, except at soils amended with 5200 kg ha−1 of soybean residues; this lack of statistical difference was probably due to the immobilization of native mineral N. Under 50% WFPS soil moisture contents, aeration seemed to be the main factor controlling redox conditions, limiting the denitrification process, and preventing differences in N emissions between residue treatments. The application of soybean residues to saturated soils notably decreased N2O + N2 emissions by denitrification through a strong mineral N immobilization into organic and nondenitrifiable forms.

The Feasibility of Winter Wheat Following Soybean in Northern Minnesota

Lack of a suitable previous crop and the risk of winter-kill are two main reasons why winter wheat (Triticum aestivum L.) is a minor crop in Minnesota. Soybean (Glycine max (L.) Merr.) is an excellent previous crop to hard red spring wheat in the Northern Great Plains. The objectives of this research were to determine whether (i) seeding winter wheat immediately following soybean harvest allowed for the winter wheat to get established and (ii) no-till seeding into standing soybean stubble reduced the amount of winter-kill. Winter wheat was successfully established and grown following soybean when more winter-hardy varieties were selected. No-till seeding tended to reduce winter-kill and improved spring vigor for more winter-hardy varieties, and no-till seeding improved grain yield and reduced grain protein content compared to conventional seeding.

Short‐Term Variations in Chemical Properties of Vertisols as Affected by Amounts, Carbon/Nitrogen Ratio, and Nutrient Concentration of Crop Residues

Wheat (Triticum aestivum L.), faba bean (Vicia faba L.), and soybean (Glycine max L.) are sown in rotation with cotton (Gossypium hirsutum L.) on eastern Australian Vertisols. Several long‐term studies, where soil was sampled annually, have reported that rotation crops affected only soil structure and soil nitrogen (N). The long time interval between sampling times in the field studies may have resulted in changes in soil quality remaining undetected. The objectives of this study were to (1) determine if mineralization of crop residues in Vertisols previously sown with cotton resulted in short‐term changes in soil properties, and (2) describe their nature. Short‐term changes in properties of Vertisols were studied in two laboratory experiments by adding milled residues to a sodic, heavy clay soil (635 g/kg clay, exchangeable sodium percentage, ESP, of 12) and a nonsodic medium clay soil (540 g/kg clay, ESP of 2). The crop materials used were vegetative and seed material from faba bean, vegetative material from wheat at anthesis (“green wheat”), cotton, wheat straw (“mature wheat”), and soybean stubble, which were added to the soils at five rates: 0% (untreated control), 2%, 5%, 10%, and 20% of the air‐dried weight of the soil. Soils were analyzed for pH (in CaCl2), EC1:5, exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) and were measured with an atomic absorption spectrophotometer after washing with aqueous alcohol and aqueous glycerol to remove soluble salts followed by extraction with alcoholic 1 M NH4Cl at a pH of 8.5. The sodicity indices ESP and EC1:5/exchangeable Na were then calculated. Most soil improvement, viz. distinct increases in exchangeable K and lower sodicity, occurred with green wheat residues, due to its high K concentration and low C:N ratio. Variation in soil changes between crop residues was directly related to the amounts added, their C:N ratios, and nutrient concentrations. The primary cause of the inability of rotations to cause extensive soil changes appears to be the small amounts and low mineral content of crop residues returned to the soil. Significant improvements of soil quality in Vertisols sown with cotton‐based farming systems are more likely if large amounts of green cereal crop residues are added.

Chaetomium globosum for reducing primary inoculum of Diaporthe phaseolorum f. sp. meridionalis in soil-surface soybean stubble in field conditions

Abstract The potential of an antibiotic-producing isolate of Chaetomium globosum (CgA-1) to suppress Diaporthe phaseolorum f. sp. meridionalis (Dpm) in soybean stubble was studied in field microplots of no-tillage, minimum-tillage, and shallow plowing. Mature soybean stems colonized in vitro with Dpm were spread on the soil surface and C. globosum ascospore suspension, without nutrient supply, was sprayed over the entire plot prior to any tillage operation. Perithecial formation and survival of Dpm in soybean stems, concomitantly with colonization by C. globosum, were monitored for a 180-day period (mid-autumn through winter and mid-spring), which is the normal interval between soybean harvest and sowing. The proportion of soybean stem segments occupied by Dpm and number of perithecia formed decreased linearly with time and showed a strong negative correlation with increase in the occupation by C. globosum. At the end of the study, which coincided with the soybean sowing season, the soybean stubble was free from viable Dpm and was colonized by C. globosum. The effectiveness of C. globosum in eliminating the pathogen from surface-borne residue or harrowed-in residue was similar but much slower than in the shallow-plowed microplots. C. globosum successfully competed with major interfering fungi such as, Trichoderma, Nigrospora, and Fusarium in colonizing the soybean stems above and under the soil surface. The data provide strong evidence for use of the antibiotic-producing isolate of C. globosum to control soybean stem canker disease.

Baiting blackbirds (Icteridae) in stubble grain fields during spring migration in South Dakota

Blackbirds (Icteridae) annually damage US$5–8 million of ripening sunflower in the northern Great Plains. Baiting blackbirds with avicide-treated rice during spring migration might reduce the regional breeding population. In March and April 1996–1997, we simulated a baiting program in eastern South Dakota to compare attractiveness of rice-baited plots placed in fields of corn and soybean stubble. Blackbirds used plots in corn stubble more often than plots in soybean stubble and chose rice-baited plots over unbaited reference plots. We conclude that blackbirds can be successfully baited with avicide-treated rice placed in corn stubble.

MANURE SOLIDS SEPARATION BY FILTRATION WITH FOUR CROP RESIDUES

Laboratory research was conducted to determine the effectiveness of using five crop residues as filters toseparate solids from liquid swine manure. Solids removal efficiencies and plugging characteristics were examined. Oatstraw, soybean stubble, and corn stover were found to be effective filter materials; corncobs and ground corncobs werenot. As expected, solids removal efficiencies were higher for manure with 6.0% solids initially than for manure with 1.4%solids, but plugging occurred sooner. Most of the separation occurred within the top portion of the filters.

Strip Intercropping of Corn-Soybean in Irrigated and Rainfed Environments

A strip intercropping system of corn (Zea mays L.) and soybean [Glycine Max (L.) Merrill] has the potential to reduce soil erosion and increase the biological and economic efficiencies of a corn-soybean rotational system. The objective of this study was to evaluate grain production in a corn-soybean strip intercropping system under irrigated and rainfed conditions in eastern Nebraska. Corn and soybean were grown in alternating 20 ft. (eight-row) strips in a north-south orientation on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudolls) at the University of Nebraska Agricultural Research and Development Center near Mead. A full-season corn hybrid was grown in strips in combination with soybean cultivars of different maturity groups. Yields of the two border rows of corn and soybean strips were machine harvested and compared with the middle four rows of each crop strip to determine border effects. Under irrigated conditions, corn yields in the outside two rows increased in 4 of 5 yr. A maximum yield increase of 28 bu/acre occurred in 1986, with a 5-yr average increase of 17 bu/acre (11%) in the corn borders. Under rainfed conditions, corn border row yield increases were less consistent, averaging 5 bu/acre. In 1989, a maximum corn yield increase of 19 bu/acre (23%) was obtained in the rainfed environments. Soybean yields were reduced in the outside two border rows compared with the middle four rows under both rainfed and irrigated environments. Yields from soybean rows adjacent to corn were reduced an average of 6 bu/acre over the 5-yr period. Land Equivalent Ratios (LER = land area needed in monoculture to equal production in one unit area of intercropping) averaged 1.00 and 0.96 for the irrigated and rainfed strip intercropping systems, respectively, suggesting no benefit under either condition for the multispecies systems. Although economics of the system are dependent on corn and soybean prices, results of these experiments indicate strip intercropping systems of corn-soybean show no consistent differences in systems yield or net returns compared with monoculture fields under the same conditions. Strip intercropping will then benefit by reducing erosion on soybean stubble.

Evaluation of Insecticides for Control of Larval European Corn Borer on Whorl-Stage Corn, 1997

Abstract Experimental and labelled insecticides were evaluated for efficacy against larval ECB in whorl-stage field corn near Clay Center, NE. Experimental design was a RGB with four replicates. ‘Dekalb 641’ hybrid field corn was planted on 25 Apr into soybean stubble at a seeding rate of 29,900 plants/acre. Each plot consisted of a single row, 40 ft long with a 30-inch row spacing. Soil type was a Crete silt loam with a 0-1% slope. A CO2-pressurized back-pack sprayer mounted on the planter was used to apply liquid insecticides at planting. A TeeJet #250017 nozzle positioned between the disc openers was used to direct an in-furrow spray of 1.25 gpa at 8 psi (LP). Five plants per plot were artificially infested with 10 ECB egg masses each on 20 Jun. These plants were free of larval whorl damage prior to infestation based on visual inspection. Also, five naturally infested plants which exhibited active larval whorl feeding were marked at the time of artificial infestation. When the crop was in 8-leaf growth stage, the plants were artificially infested with egg masses in black-head stage on 21 Jun. All whorl treatments were applied on 26 Jun when crop was in 10-11-leaf growth stage. Granular insecticides were applied using the mason jar ‘shaker’ method (G). Liquid insecticides were broadcast over the top of the plant whorl with a CO2-pressurized backpack sprayer at 21 gpa at 30 psi (L). The stalks of both the artificial and naturally infested plants were split lengthwise and the total number of tunnels in the five plants per plot were recorded to evaluate ECB larval damage. The percent infestation at evaluation was determined by the number of plants with a minimum of 1 cavity. The artificially infested plants were evaluated on 21 Jul. The naturally infested plants were evaluated on 22 Jul and 28-29 Jul. Data were analyzed by ANOVA for RCB with mean separation using DMRT.

Fungal parasitism of soybean cyst nematode, Heterodera glycines (Nemata: Heteroderidae), in differing cropping-tillage regimes

A 2 year field study was designed to determine if soybean-wheat double-cropping and reduced or no tillage altered the soil mycoflora antagonistic to the soybean cyst nematode, Heterodera glycines. Six treatments were sampled monthly: disc 10 cm deep, followed by roller harrow; chisel plow 20 cm deep, followed by disc and roller harrow; moldboard plow 15 cm deep, followed by disc and roller harrow; non-tillage in the previous year's soybean stubble (NT-Soy); non-tillage in standing wheat cover crop (NT-1); non-tillage after wheat cover crop (NT-7). Each treatment had been applied to the same plots for up to 7 years. At appropriate monthly intervals, nematode cysts, females, and eggs were collected and assayed for the presence of fungi, which were identified to species-level taxa. Effects of cropping-tillage regimes on numbers of infective juveniles, numbers of eggs within cysts, and vertical distribution of cysts were determined. Similarities of egg and female mycofloras in this study to those of previous studies were examined. A total of 61 species-level fungal taxa were identified, along with 20 non-sporulating isolates distinguished from one another by appearance, growth pattern, and color. Fusarium solani was the most frequent of 47 species infesting cysts. Fusarium solani and F. oxysporum were the most frequent of 20 taxa isolated from field-collected females; in females produced on soybean plants grown in field soil in the greenhouse, F. oxysporum was the most frequent of 21 taxa. Paecilomyces lilacinus was the most common fungus among the 38 species isolated from eggs. For all fungi, percentages of parasitized females and eggs were similar in all treatments, but some treatments affected the parasitism rates of Paecilomyces lilacinus and Verticillium chlamydosporium. Parasitism of females was relatively low in July and August, but tripled in September. Egg parasitism was generally below 10% regardless of sampling time. Vertical distribution of cysts had no discernible effect on sampling precision, since cysts were concentrated in the top 25 cm in two dissimilar treatments (moldboard plow, NT-7). No consistent treatment effects were seen on densities of soil-borne infective juveniles in winter or spring, nor on average numbers of eggs per cyst. Based on similarity indices among this study and four previous studies, a biogeography of H. glycines mycofloras is proposed.

Yield and Nitrogen Uptake of Spring Wheat Planted in a Ridge-Till System

Conservation tillage and inclusion of a cover crop that provides surface residue cover are two management options for reducing soil erosion losses commonly found in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr] rotation. Information is lacking, however, on the performance of a small grain planted in a ridge-tillage system in the Northern Corn Belt. A 3-yr (1992-1994) study was conducted to determine the effect of row position (ridge, shoulder, furrow, and wheel track furrows) on yield and N uptake of hard red spring wheat (Triticum aestivum L.) planted in a ridge-tillage system on poorly drained Webster clay loam (fine-loamy, mixed, mesic Typic Haplaquoll) soil at two locations in southern Minnesota. Spring wheat was planted after soybean in 15 ft wide strips. Wheat performance was affected by the position of the row across the ridged seedbed. Averaged across the 3 yr, grain yield of the wheat rows planted on ridge top and shoulder positions was 31% greater than those rows planted in the furrows at both locations. Grain yield of wheat in the wheel track furrows was reduced by 38% at Freeborn and by 33% at Waseca compared with those planted on ridge tops and shoulders when averaged across years. Moreover, grain yield in the wheel track furrows was reduced by 18% at Freeborn and by 12% at Waseca compared with non-wheel track furrows across years. Similar to grain yield, straw yield and total N uptake were greater in the ridge top and shoulder positions than in either non-wheel track or wheel track furrow positions. Lesser grain yield in the furrows and wheel track furrows correlated well with reduced head numbers in these row positions compared with ridge top and shoulder positions. The results from this study indicate that wheat can be successfully planted in a ridge-tillage system. Yield losses, however, occur in the furrows and controlled wheel track furrows, especially in wet years in this ridge-till system.