Soybean Stands Research Articles

Impact of Early Season Insecticide Applications on Soybean Stand Establishment, 2020

Impact of Early Season Insecticide Applications on Soybean Stand Establishment, 2020

Impact of Selected Insecticide Seed Treatments on Soybean Stand Establishment and Yield 2, 2019

Impact of Selected Insecticide Seed Treatments on Soybean Stand Establishment and Yield 2, 2019

Impact of Selected Insecticide Seed Treatments on Soybean Stand Establishment and Yield, 2020

Impact of Selected Insecticide Seed Treatments on Soybean Stand Establishment and Yield, 2020

Effect of Resistance and Ethaboxam Seed Treatment on the Management of Phytophthora Root Rot in Illinois and Iowa

Phytophthora root and stem rot (PRR) is a limiting factor for soybean production. Seed treatments are used for early-season management, but efficacy can depend on seed selection and the local environment. Ethaboxam is a new fungicide commercially available as a seed treatment to control oomycetes. Field experiments were established in Illinois and Iowa in 2017 and 2018 to evaluate the effect of ethaboxam + metalaxyl on PRR. Experiments included soybean lines with no resistance gene, Rps1c or Rps1k, and different levels of partial resistance. Seed treatments increased soybean stands in all locations and years. Significant yield effects were observed only in two locations that were inoculated with Phytophthora spp. Groups of soybean lines with the same Rps gene responded differently in each location, showing how Rps gene usefulness depends on the field. A comparison of the effect of seed treatment on lines with different levels of partial resistance showed that partial resistance alone cannot always protect against stand losses. Soybean lines with high levels of partial resistance had consistently higher yields than those with low levels of partial resistance across Illinois locations. These results show that ethaboxam seed treatment can protect early-season stands and that selection of cultivars with high levels of partial resistance is important for PRR management.

Impact of Selected Insecticide Seed Treatments on Soybean Stand Establishment and Yield 1, 2019

Impact of Selected Insecticide Seed Treatments on Soybean Stand Establishment and Yield 1, 2019

Cultural weed management practices shorten the critical weed-free period for soybean grown in the Northern Great Plains

Abstract Soybean [Glycine max (L.) Merr.] has recently become a popular rotational crop in the Canadian Northern Great Plains where herbicide-resistant (HR) soybean cultivars have been widely adopted. Intense reliance on herbicides has contributed to the development of HR weeds in soybean and other crops. Cultural weed management practices reduce the need for herbicides and lower the selection pressure for HR weed biotypes by improving the competitiveness of the crop. The effects of two row spacings, three target densities, and three cultivars on the critical weed-free period (CWFP) in soybean were evaluated as three separate experiments in southern Manitoba. In the row-spacing experiment, soybean grown in narrow rows shortened the CWFP by up to three soybean developmental stages at site-years with increased weed pressure. In the target density experiment, low-density soybean stands lengthened the CWFP by one soybean developmental stage compared with higher-density soybean stands. The effect of soybean cultivar varied among locations, yet tended to be consistent within location over the 2-yr study, suggesting that competitive ability in these soybean cultivars was linked to edaphic and/or environmental factors. Generally, the cultivar with the shortest days to maturity, which also had the shortest stature, consistently had a longer CWFP. Each of these cultural practices were effective at reducing the need for in-crop herbicide applications.

A long-term precision agriculture system sustains grain profitability

After two decades of availability of grain yield-mapping technology, long-term trends in field-scale profitability for precision agriculture (PA) systems and conservation practices can now be assessed. Field-scale profitability of a conventional or ‘business-as-usual’ system with an annual corn (Zea mays L.)-soybean (Glycine max [L.]) rotation and annual tillage was assessed for 11 years on a 36 ha field in central Missouri during 1993 to 2003. Following this, a ‘precision agriculture system’ (PAS) with conservation practices was implemented for the next 11 years to address production, profit and environmental concerns. The PAS was multifaceted and temporally dynamic. It included no-till, cover crops, crop rotation changes, site-specific N and variable-rate or zonal P, K and lime. Following a recent evaluation of differences in yield and yield variability, this research compared profitability of the two systems. Results indicated that PAS sustained profits in the majority (97%) of the field without subsidies for cover crops or payments for enhanced environmental protection. Profit was only lower with PAS in a drainage channel where no-till sometimes hindered soybean stands and wet soils caused wheat (Triticum aestivum L.) disease. Although profit gains were not realized after 11 years of PA and conservation practices, this system sustained profits. These results should help growers gain confidence that PA and conservation practices will be successful.

N2-fixation and N contribution by grain legumes under different soil fertility status and cropping systems in the Guinea savanna of northern Ghana

Continuous cereal-based cropping has led to a rapid decline in soil fertility in the Guinea savanna agro-ecological zone of northern Ghana with corresponding low crop yields. We evaluated the effects of cropping system and soil fertility status on grain yields and N2-fixation by grain legumes and net N contribution to soil fertility improvement in contrasting sites in this agro-ecological zone. Maize was intercropped with cowpea, soybean and groundnut within a row, with a maize stand alternated with two equally spaced cowpea or groundnut stands and in the maize-soybean system, four equally spaced soybean stands. These intercrops were compared with sole crops of maize, cowpea, soybean and groundnut in fertile and poorly fertile fields at sites in the southern (SGS) and the northern (NGS) Guinea savanna. The proportion of N derived from N2-fixation (%Ndfa) was comparable between intercrops and sole crops. However, the amount of N2-fixed was significantly larger in sole crops due to a greater biomass accumulation. Legumes in poorly fertile fields had significantly smaller shoot δ15N enrichment (−2.8 to +0.7‰) and a larger %Ndfa (55–94%) than those in fertile fields (−0.8 to +2.2‰; 23–85%). The N2-fixed however was larger in fertile fields (16–145kgNha−1) than in poorly fertile fields (15–123kgNha−1) due to greater shoot dry matter and N yields. The legumes grown in the NGS obtained more of their N requirements from atmospheric N2-fixation (73–88%) than legumes grown in the SGS (41–69%). The partial soil N balance (inkgha−1) was comparable between intercrops (−14 to 21) and sole legumes (−8 to 23) but smaller than that of sole maize receiving N fertiliser (+7 to +34). With other N inputs (aerial deposition) and outputs (leaching and gaseous losses) unaccounted for, there is uncertainty surrounding the actual amount of soil N balances of the cropping systems, indicating that partial N balances are not reliable indicators of the sustainability of cropping systems. Nevertheless, the systems with legumes seem more attractive due to several non-N benefits. Our results suggest that soybean could be targeted in the SGS and cowpea in the NGS for greater productivity while groundnut is suited to both environments. Grain legumes grown in poorly fertile fields contributed more net N to the soil but growing legumes in fertile fields seems more lucrative due to greater grain and stover yields and non-N benefits.

Suppression of Soilborne Diseases of Soybean With Cover Crops

Field trials were conducted from 2010 to 2013 at four locations in Illinois to evaluate the impact of cover crops (cereal rye [Secale cereal], brown mustard [Brassica juncea], winter canola [B. napus], and winter rapeseed [B. napus]) on soybean [Glycine max] stands and yield, diseases, pathogen populations, and soil microbial communities. Cover crops were established in the fall each year and terminated the following spring either by using an herbicide (no-till farms), by incorporation (organic farm), or by an herbicide followed by incorporation (research farm). Although shifts in soilborne pathogen populations and microbial community structure were not detected, cover crops were found to induce general soil suppressiveness in some circumstances. Cereal rye and rapeseed improved soybean stands in plots inoculated with Rhizoctonia solani and decreased levels of soybean cyst nematode in the soil. Cereal rye increased soil suppressiveness to R. solani and Fusarium virguliforme, as measured in greenhouse bioassays. Cereal rye significantly improved yield when Rhizoctonia root rot was a problem.

Effect of Tillage Depth System and Intercropping Patterns on Solid and Intercropped Soybean with Maize.

Two field experiments were carried out in Gemmeiza Research Station during the two summer successive seasons 2013 and 2014 to investigate the effect of three soil tillage depths i.e. 15, 20 and 25 cm and three intercropping patterns i.e. P1-100% maize (single cross 128) + 50% soybean (variety Giza 111) in ridges (0.70 m in width) P2- 100% maize + 50 % soybean in beds (1.40 m in width) and soybean was intercropped with maize at the two rows on bed back, whereas maize was planted at both sides of the bed and P3- Pure stands of maize and soybean were planted as recommended for each crop. The experiment was laid out in a strep plot design in three replicates. Results could be summarized as follows: All characters of maize was significant by affected increasing soil tillage depth from 15 up to 20 cm depth except, plant height in first season. On the other hand, maize grain yield recorded the highest value with tillage depth at 20 cm in both seasons. Maize pure stand recorded the highest values of all studied characters followed by planting in beds and the lowest values were obtained, when maize grown in ridges in both seasons, except, plant height behaved opposite trend of these characters. indicated that plant height in the second season, No. of kernels, ear weight-1, 100-kernel weight in the first season and maize grain yield fad-1 in both seasons were significantly affected by interaction between plowing depth and intercropping patterns. Also, all soybean characters were significantly affected by tillage systems in both seasons, where, tillage depth at 20 cm gave the highest values, followed by at 25 cm While, 15 cm depth gave the lowest values in both seasons. Whereas soybean pure stand recorded the highest values of yield in both seasons, followed intercropping 100% + 50% soybean on the beds in both seasons. The found that 100-seed weight and seed yield fad-1 in both seasons were significantly affected by the interaction between different tillage depth and intercropping patterns. Soil tillage depth at 20 cm and intercropping pattern (100% maize + 50% soybean) on beds recorded the highest values for LER (1.34) and LEC (0.43) in the combined analysis, which showed that intercropping had better grain yield performance when compared to sole cropping. All intercropping patterns were grown in different depths were positive for total income comparative to maize pure stand in combined analysis of both seasons. The highest total income and MAI were achieved with plowing depth at 20 cm in beds (8855.96and 2247.03 L.E. fad-1 ) and the lowest value was showed with plough at 25 cm in ridge (6426.63 and 126.01L.E.fad). Growing maize and soybean with plowing depth at 20 cm increased total income by 10.26 and 10.70%, while MAI increased by 0.88 and 28.80 % compared with plowing depth 15 and 25 respectively. It could be concluded that tillage at 20 cm depth and intercropping pattern (100% + 50%) maize/soybean planted in beds to obtain the best land usage and total income.

Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient

Influences of ozone (O3) on light-saturated rates of photosynthesis in crop leaves have been well documented. To increase our understanding of O3 effects on individual- or stand level productivity, a mechanistic understanding of factors determining canopy photosynthesis is necessary. We used a canopy model to scale photosynthesis from leaf to canopy, and analyzed the importance of canopy structural and leaf ecophysiological characteristics in determining canopy photosynthesis in soybean stands exposed to 9 concentrations of [O3] (37–116 ppb; 9-h mean). Light intensity and N content peaked in upper canopy layers, and sharply decreased through the lower canopy. Plant leaf area decreased with increasing [O3] allowing for greater light intensity to reach lower canopy levels. At the leaf level, light-saturated photosynthesis decreased and dark respiration increased with increasing [O3]. These data were used to calculate daily net canopy photosynthesis (Pc). Pc decreased with increasing [O3] with an average decrease of 10% for an increase in [O3] of 10 ppb, and which was similar to changes in above-ground dry mass production of the stands. Absolute daily net photosynthesis of lower layers was very low and thus the decrease in photosynthesis in the lower canopy caused by elevated [O3] had only minor significance for total canopy photosynthesis. Sensitivity analyses revealed that the decrease in Pc was associated with changes in leaf ecophysiology but not with decrease in leaf area. The soybean stands were very crowded, the leaves were highly mutually shaded, and sufficient light for positive carbon balance did not penetrate to lower canopy leaves, even under elevated [O3].

Effects of transgenic soybean on growth and phosphorus acquisition in mixed culture system.

Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 (OXp) or the soybean expansin gene GmEXPB2 (OXe) can improve phosphorous (P) efficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean-soybean mixed cultures were employed to illuminate P acquisition among plants in mixed stands of transgenic and wild-type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild-type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean-maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean in mixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls. These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.

Onset of deep drainage and salt mobilization following forest clearing and cultivation in the Chaco plains (Argentina)

moisture content and 94% lower chloride stocks compared to dry forest (0.05 6 0.04 kg/m 2 versus 0.77 6 0.4 kg/m 2 ). Estimates of groundwater recharge based on the displacement of chloride peaks suggested values of 27–87 mm yr � 1 for agricultural soybean stands, and 10.4 mm yr � 1 for pastures. While hydrological shifts in the regional groundwater system are poorly monitored and understood, our findings show that it is potentially sensitive to land use changes and to salinization processes.

Effects of elevated CO2 on leaf area dynamics in nodulating and non-nodulating soybean stands

The effects of elevated CO2 on leaf area index (LAI) vary among studies. We hypothesized that the interactive effects of CO2 and nitrogen on leaf area loss have important roles in LAI regulation. We studied the leaf area production and loss using nodulating soybean and its non-nodulating isogenic line in CO2-controlled greenhouse systems. Leaf area production increased with elevated CO2 levels in the nodulating soybean stand and to a lesser extent in the non-nodulating line. Elevated CO2 levels accelerated leaf area loss only in nodulating plants. Consequently, both plants exhibited a similar stimulation of peak LAI with CO2 elevation. The accelerated leaf loss in nodulating plants may have been caused by newly produced leaves shading the lower leaves. The nodulating plants acquired N throughout the growth phase, whereas non-nodulating plants did not acquire N after flowering due to the depletion of soil N. N retranslocation to new organs and subsequent leaf loss were faster in non-nodulating plants compared with nodulating plants, irrespective of the CO2 levels. LAI regulation in soybean involved various factors, such as light availability within the canopy, N acquisition and N demands in new organs. These effects varied among the growth stages and CO2 levels.

Effect of Fungicide Seed Treatments, Cultivars, and Soils on Soybean Stand Establishment.

Seedling diseases are one of the major production problems for soybean. The primary control of soybean seedling diseases is by fungicide seed treatments but comparisons of seed treatments are difficult because stand responses are often erratic in the field. The objective of this study was to determine the efficacy of soybean fungicide seed treatments in naturally infested soils under controlled environments at three temperatures. Seed of three soybean cultivars were treated with six fungicide treatments or not treated and planted in two soil types collected from two fields in April, May, and June 2008 and 2009. Tests were conducted in growth chambers at 21°C (April planting), 25°C (May planting), or 28°C (June planting). Stands were determined when at least 25% of the seedlings reached the V4 growth stage. Seed treatments improved stands at all three temperatures, in both soils, and in both years. In general, the broad-spectrum fungicides trifloxystrobin + metalaxyl and mefenoxam + fludioxonil + azoxystrobin resulted in the highest stands. The selective fungicide treatments metalaxyl and pentachloronitrobenzene + carboxin were effective at all three temperatures, implying that Pythium spp. and Rhizoctonia solani, respectively, were involved in seedling disease and active over a range of temperatures. The efficacy of fungicides was not consistently associated with the cultivars used in this study.

Crop Residue and Residue Management Effects on <I>Armadillidium vulgare</I> (Isopoda: Armadillidiidae) Populations and Soybean Stand Densities

In general, Armadillidium vulgare (Latreille) are considered nonpests of soybean [Glycine max (L.) Merrill], but changes in soil conservation practices have shifted the pest status of this organism from an opportunistic to a perennial, early-season pest in parts of central Kansas. As a result, soybean producers that rotate with corn (Zea mays L.) under conservation tillage practices have resorted to removing excess corn residue by using controlled burns. In a 2-yr field study (2009-2010), we demonstrated that residue removal in burned compared with unburned plots (measured as previous crop residue weights) had minimal impact on numbers of live and dead A. vulgare, soybean seedling emergence, and isopod feeding damage over time. Specifically, removal of residue by burning did not result in higher emergence rates for soybean stands or less feeding damage by A. vulgare. In a separate study, we found that number of live A. vulgare and residue weights had no consistent relationship with seedling emergence or feeding damage. Furthermore, seedling emergence was not impacted by higher numbers ofA. vulgare in unburned plots, indicating that emergence in this study may have been influenced by factors other than A. vulgare densities. These studies demonstrate that removing residue through controlled burning did not impact seedling emergence in presence of A. vulgare and that residue and feeding damage to seedlings did not consistently relate to A. vulgare densities. Other factors that may have influenced a relationship between residue and live isopod numbers, such as variable moisture levels, are discussed.

Temperature Dependence of Bulk Respiration of Crop Stands—Measurement and Model Fitting

The objective of the present study was to examine whether the temperature dependence of respiration at a crop-stand scale could be directly represented by an Arrhenius function that was widely used for representing the temperature dependence of leaf respiration. We determined temperature dependences of bulk respiration of monospecific stands of rice and soybean within a range of the air temperature from 15 to 30°C using large closed chambers. Measured responses of respiration rates of the two stands were well fitted by the Arrhenius function (R2 = 0:99). In the existing model to assess the local radiological impact of the anthropogenic carbon-14, effects of the physical environmental factors on photosynthesis and respiration of crop stands are not taken into account for the calculation of the net amount of carbon per cultivation area in crops at harvest which is the crucial parameter for the estimation of the activity concentration of carbon-14 in crops. Our result indicates that the Arrhenius function is useful for incorporating the effect of the temperature on respiration of crop stands into the model which is expected to contribute to a more realistic estimate of the activity concentration of carbon-14 in crops.

Distribution and Biocontrol Potential of phlD+ Pseudomonads in Corn and Soybean Fields

ABSTRACT The abundance and diversity of phlD(+) Pseudomonas spp. colonizing the rhizospheres of young, field-grown corn and soybean plants were assayed over a 3-year period. Populations of these bacteria were detected on the large majority of plants sampled in the state of Ohio, but colonization was greater on corn. Although significant variation in the incidence of rhizosphere colonization was observed from site to site and year to year on both crops, the magnitude of the variation was greatest for soybean. The D genotype was detected on plants collected from all 15 counties examined, and it represented the most abundant subpopulation on both crops. Additionally, six other genotypes (A, C, F, I, R, and S) were found to predominate in the rhizosphere of some plants. The most frequently observed of these were the A genotype and a newly discovered S genotype, both of which were found on corn and soybean roots obtained from multiple locations. Multiple isolates of the most abundant genotypes were recovered and characterized. The S genotype was found to be phylogenetically and phenotypically similar to the D genotype. In addition, the novel R genotype was found to be most similar to the A genotype. All of the isolates displayed significant capacities to inhibit the growth of an oomycete pathogen in vitro, but such phenotypes were highly dependent on media used. When tested against multiple oomycete pathogens isolated from soybean, the A genotype was significantly more inhibitory than the D genotype when incubated on 1/10x tryptic soy agar and 1/5x corn meal agar. Seed inoculation with different isolates of the A, D, and S genotypes indicated that significant root colonization, generally in excess of log 5 cells per gram of root, could be attained on both crops. Field trials of the A genotype isolate Wayne1R indicated the capacity of inoculant populations to supplement the activities of native populations so as to increase soybean stands and yields. The relevance of these findings to natural and augmentative biocontrol of root pathogens by these bacteria is discussed.

Ethylene Production throughout Growth and Development of Plants

Ethylene production by 10 or 20 m2 stands of wheat, soybean, lettuce, potato, and tomato was monitored throughout growth and development in an atmospherically closed plant chamber. Chamber ethylene levels varied among species and rose during periods of canopy expansion and rapid growth for all species. Following this, ethylene levels either declined during seed fill and maturation for wheat and soybean, or remained relatively constant for potato and tomato (during flowering and early fruit development). Lettuce plants were harvested during rapid growth and peak ethylene production. Chamber ethylene levels increased rapidly during tomato ripening, reaching concentrations about 10 times that measured during vegetative growth. The highest ethylene production rates during vegetative growth ranged from 1.6 to 2.5 nmol m-2 d-1 during rapid growth of lettuce and wheat stands, or about 0.3 to 0.5 nmol g-1 fresh weight per hour. Estimates of stand ethylene production during tomato ripening showed that rates reached 43 nmol m-2 d-1 in one study and 93 nmol m-2 d-1 in a second study with higher lighting, or about 50x that of the rate during vegetative growth of tomato. In a related test with potato, the photoperiod was extended from 12 to 24 hours (continuous light) at 58 days after planting (to increase tuber yield), but this change in the environment caused a sharp increase in ethylene production from the basal rate of 0.4 to 6.2 nmol m-2 d-1. Following this, the photoperiod was changed back to 12 h at 61 days and ethylene levels decreased. The results suggest three separate categories of ethylene production were observed with whole stands of plants: 1) production during rapid vegetative growth, 2) production during climacteric fruit ripening, and 3) production from environmental stress.

Analysis of a Novel Bedded Planting System for Dry Clay Soil Management of Full‐Season and Double‐Crop Soybean

Clay soils are difficult to manage to obtain a soybean [Glycine max (L.) Merr.] stand, especially when dry. A novel production system, recently observed on several farms in Arkansas, consists of bedding the dry clayey soil with disk‐bedders, broadcasting the soybean seed over the surface, re‐bedding the seedbed to cover the seed, rolling the beds to flatten the tops and finally furrow irrigating immediately thereafter. Typically this planting system provides a stand of soybean within 4 to 6 days after irrigation and is designated as “hipped” after the common reference of a disk‐bedder as a hipper. Studies were conducted on Sharkey soil at Keiser, AR from 1998 to 2000 for comparing this “hipped” system to more widely used planting methods. On dry clayey soils, a randomized complete block design with three replications was used to compare full‐season soybean under a conventional 96‐cm row system, drilled‐planting into a stale seedbed, and the “hipped” system. A similar study for double‐cropped wheat‐soybean involved straw management (burn or leave) coupled with no‐till drill, tilled drill, and “hipped” systems. Other small studies on the “hipped” system were conducted to investigate the sensitivity to planting depth, soybean plant population, and suitability for obtaining a stand on other crops such as cotton [Gossypium hirsutum (L.)] and grain sorghum [Sorghum bicolor (L.) Moench]. The “hipped” system worked well for obtaining stands of soybean, cotton, and grain sorghum. In essence the “hipped” system 1) provides insurance against poor planting conditions; 2) allows for a reduction in the uncertainty of planting and stand establishment time required; 3) can be used to achieve high plant populations; 4) requires a relatively higher seeding rate in double‐crop than full‐season systems; 5) shows promise for situations when wheat stubble burning becomes curtailed especially if planting can occur early to lead to improved canopy coverage and 6) leads to yield reductions in fields where depth of seed placement cannot be controlled easily.