V3 Growth Stage Research Articles

Impact of postemergence herbicides on soybean injury and canopy formation

AbstractField studies were conducted in 2017 and 2018 in Arkansas to evaluate the injury caused by herbicides on soybean canopy formation and yield. Fomesafen, acifluorfen, S-metolachlor + fomesafen, and S-metolachlor + fomesafen + chlorimuron alone and in combination with glufosinate were applied to glufosinate-resistant soybean at the V2 growth stage. Soybean injury resulting from these labeled herbicide treatments ranged from 9% to 25% at 2 wk after application. This level of injury resulted in a 4-, 5-, 6-, and 6-d delay in soybean reaching 80% groundcover following fomesafen, acifluorfen, S-metolachlor + fomesafen, and S-metolachlor + fomesafen + chlorimuron, respectively. There was a 2-d delay in soybean reaching a canopy volume of 15,000 cm3 following each of the four herbicide treatments. The addition of glufosinate to the herbicide applications resulted in longer delays in canopy formation with every herbicide treatment except glufosinate + fomesafen. Fomesafen, acifluorfen, S-metolachlor + fomesafen, and S-metolachlor + fomesafen + chlorimuron, each applied with glufosinate, delayed soybean from reaching 80% groundcover by 2, 7, 8, and 9 d, respectively, and delayed the number of days for soybean to reach a canopy volume of 15,000 cm3 by 2, 3, 2, and 2 d, respectively. No yield loss occurred with any herbicide application. A delay in percent groundcover in soybean allows sunlight to reach the soil surface for longer periods throughout the growing season, possibly promoting late-season weed germination and the need for an additional POST herbicide application.

Maize hybrids contrasting for drought tolerance differ during the vegetative stage

Maize hybrids contrasting for drought tolerance differ during the vegetative stage. Drought is the main constraint on maize production in developing nations. Differences during development between genetic materials of maize grown under water restriction suggest that the plant can be improved with a view to its adaptation. In maize, sensitivity to water stress can occur at any stage of its phenological development. However, few studies report its effects on the vegetative phase of the cycle. On this basis, this study was conducted to examine how shoot and root-system indices are expressed in cultivation under water deficit as well as determine which indicators best explain the difference between hybrids in the evaluated water regimes. Commercial seeds of hybrids BR1055 and DKB-390 (drought-tolerant) and BRS1010 (drought-sensitive) were germinated in PVC tubes (1.0 m × 0.1 m) in a randomized complete block design, in a 3 × 2 factorial arrangement. The experiment was developed in a greenhouse where two water regimes were tested: no water stress and with water stress from the VE stage. The soil consisted of quartz sand mixed with a commercial fertilizer. Stem and root traits were evaluated up to the V5 growth stage. Relative chlorophyll content, leaf temperature, stem length, phenology, shoot dry biomass, root length, root dry biomass, root surface area, root volume and D95 were responsive to water deficit. The parameters that allowed the distinction between the hybrids in water the regimes were relative chlorophyll content, leaf temperature, phenology and average root diameter.

Morphological Properties of Catharanthus roseus L. Seedlings Affected by Priming Techniques Under Natural Salinity Stress

Catharanthus roseus is a great medicinal plant used for treating diseases such as cancer, as it contains different biochemicals including terpenoids. Salinity is a major stress, significantly decreasing the growth and yield of medicinal plants, worldwide. However, to our knowledge, there is not any data on the growth improvement in C. roseus seedling under salinity stress using the priming techniques tested in the presented research. The objective was to investigate the effects of seed priming including hydro- (distilled water), osmo- (KNO3 1%), and hormonal priming (salicylic acid, SA 0.5 mM) on the seedling growth of C. roseus under natural salinity (salt obtained from Qom Lake, Iran) of 0, 2.95, 5.66, 8.13, and 10.66 dSm−1. The treated seeds were grown in Petri dishes and placed in a germinator (25 ± 1 °C) for germination and the growth of seedlings. The plant seedlings were planted in the greenhouse conditions and treated during the V6–V8 growth stage with the salinity treatments (a factorial design on the basis of a completely randomized block design with three replicates) under hydroponics conditions. Different morphological properties of C. roseus including the length and the dry weight of rootlet, plumule, and seedling as well as leaf relative water content (RWC) were measured. The results indicated the alleviating effects of different priming techniques on the growth of C. roseus under natural salt stress. Although the effect of priming was not significant on RWC, salt stress and its interaction with priming significantly affected RWC indicating that the alleviating effect of priming on RWC is a function of salinity level. With increasing the level of salinity, rootlet dry weight increased, which indicates the allocation of more carbon to the roots under stress. It is possible to plant C. roseus in saline fields using the priming techniques tested in this research work.

Influence of Burner Position on Temperature Distribution in Soybean Flaming

The main objective of this study was to identify optimal burner orientation for a newly designed flame cultivator by quantifying the flame temperature distributions of cross, back, and parallel position of burners at different heights of the soybean canopy (distance from the soil surface). Flame temperatures were measured within-row for three burner orientations at seven propane doses (20–100 kg/ha) and eight different canopy heights (0–18 cm above soil surface). Soybean plants in V3 growth stage were flamed with the same doses and burner orientations, and 28 days after treatment (DAT) crop injury (0%–100%), plant height (cm), dry matter (g) and grain yield (t/ha) were assessed. All three burner orientations had high flame temperatures at lower canopy heights (<6 cm high) that gradually decreased with increasing canopy height (6–18 cm). Measured temperatures ranged from 33 to 234 ℃ for cross flaming, 29 to 269 ℃ for back flaming and 23 to 155 ℃ for parallel flaming, with high variability in temperature patterns. Back flaming generated flame temperatures above 100℃ at a lower propane dose (27 kg/ha) compared to cross and parallel flaming (40 and 50 kg/ha). For all tested parameters, parallel and cross flaming had better impact on soybeans than back flaming, but for weed control in crop rows, cross flaming is recommended.

Adaptation to Early-Season Soil Waterlogging Using Different Nitrogen Fertilizer Practices and Corn Hybrids

Excessive rainfall occurring in the early spring season in the Midwestern United States result in waterlogged soils contributing to corn production losses. The objective of our study is to evaluate the impact of soil waterlogging [non-waterlogged or waterlogged for 7 days when corn was at V3 growth stage (corn plant having three fully developed leaves with collar visible)], different pre-plant nitrogen (N) fertilizer sources and post-waterlogging rescue N fertilizer on grain and silage yield of two commercially available corn hybrids with different flood tolerance. Pre-plant N fertilizer was applied at 168 kg N ha−1. Nitrogen sources were a non-treated control (CO), polymer coated urea (PCU), urea (NCU), and urea plus Instinct (NCU + NI). A post-waterlogging rescue N fertilizer was applied at V7 as 0 or 83 kg N ha−1 of urea plus N-(n-butyl) thiophosphoric triamide (NBPT) (NCU + UI). Waterlogging decreased grain and silage yields in different years; however, significant interactions were observed among treatments. Rescue N applications increased grain yields by 6–46% in non-waterlogged treatments, but not in waterlogged treatments. The PCU and NCU + NI increased grain yields compared to the CO. Pre-plant N sources showed no significant differences in grain yield, probably due to existing environmental conditions or incorporation of fertilizer. The N source, application method, and timing for post-waterlogging rescue N application and flood-tolerant corn hybrids needs further investigation in poorly-drained claypan soils prone to waterlogging under a changing climate.

Soybean Nodulation and Plant Response to Nitrogen and Sulfur Fertilization in the Northern US

Soybean [Glycine max (L.) Merrill] seed yields in the northern United States may increase with the application of fertilizers; however Nitrogen (N) may decrease root nodulation. This study was conducted to understand the impact of N and sulfur (S) fertilization on soybean nodulation, plant, shoot and root biomass. Two cultivars were planted in experiments across ten site-years during 2015-2016. Plant observations took place at the V4 and R4 soybean growth stages. There were 41% more nodules per plant at R4 compared to V4 (38.3 vs 27.2 nodules, respectively). Cultivars responded differently to N and S fertilizer. The nodules per plant between the cultivars (30.3 vs 24.4) were different as well as the percent medium and large-sized nodules, which indicates the need to evaluate additional genotypes. Adding N decreased root nodulation (from 31.8 to 23.7 nodules per plant) and decreased nodule size but had no effect on plant, shoot or root mass. Averaged across N rates total plant mass was 2.26 and 11.36 g per plant at V4 and R4, respectively. Shoot mass, average across N rates was 1.77 and 9.65 g per plant at V4 and R4, respectively, and root mass, average across N rates was 0.49 and 1.71 g per plant at V4 and R4, respectively. Sulfur did not have an effect on nodules per plant but increased the percent medium size nodules at the R4 observation. There was no N by S interaction observed for nodule number, size of the nodules, and plant, root and shoot mass. As cultivars differed in their nodulation response to N and S, additional research would be helpful to screen other cultivars.

Interseeding cover crops in corn

AbstractFarmers benefit from ecosystem services that cover crops provide, but time constraints limit the opportunity to seed cover crops following corn (Zea mays L.) harvest in the upper Midwest. Interseeding cover crops in corn during the early vegetative growth stages lengthens the cover crop growing season; however, cover crops may have difficulty establishing in standing corn, or conversely, compete with corn and reduce yield. The objectives of this research were to determine cover crop establishment when broadcast interseeded in corn from the V2–V7 growth stages, suppression of weeds by cover crops, and effects of cover crops on corn grain yield. Annual ryegrass (Lolium multiflorum Lam.), crimson clover (Trifolium incarnatum L.), oilseed radish (Raphanus sativus L.), and a three‐species mixture were interseeded in four site‐years in Michigan. Annual ryegrass density was highest compared with oilseed radish and crimson clover 30 d after interseeding and at harvest in October. Cover crop density was highest at the V4–V7 interseeding timings. Annual ryegrass produced more fall biomass (186 kg ha−1) compared with crimson clover (112 kg ha−1), and fall biomass was greatest at the V2, V3, and V5 interseeding timings. Spring biomass was 384 and 180 kg ha−1 for annual ryegrass and the cover crop mixture, respectively; these treatments reduced winter annual weed biomass. Corn grain yield was unaffected by cover crops at any interseeding timing. Crimson clover did not establish well in this experiment. Annual ryegrass and oilseed radish interseeded in V2–V7 corn did not reduce corn grain yield.

Ammonia volatilization and yield of corn fertilized with different nitrogen sources in the Brazilian semiarid

Abstract: The objective of this work was to evaluate the effect of the use of different nitrogen fertilizers on N losses by NH3 volatilization and on the grain yield of a corn (Zea mays) crop grown in the semiarid region of the state of Sergipe, Brazil. Corn was managed under rainfed conditions and conventional tillage. The fertilization treatments were: sulfur-coated urea (SU) and organo-mineral-coated urea (OMU). Regular urea and ammonium sulfate (AS) were also included as a reference of N sources of high and low NH3-volatilization potential, as well as a control without N fertilization. The N sources were applied to the soil surface at a rate of 150 kg ha-1 N as side-dressing at the V5 growth stage of corn. The experiment was carried out in 2015 and repeated in 2016. Losses of N through NH3 volatilization differed among the N sources in the two study years, with AS presenting the lowest N losses and regular urea, the highest. In the area treated with OMU, losses by NH3 volatilization were consistently controlled, showing a reduction of 74 and 67% in relation to that of regular urea in both years. SU, however, only mitigated NH3-N losses in 2015, increasing them in 2016, compared with regular urea. Corn plant grain yield and N status, assessed by the index leaf, did not clearly reflect N losses by NH3 volatilization. For the semiarid of Sergipe, OMU is the best urea-based fertilizer to mitigate N losses by NH3 volatilization, and the use of AS is an alternative to increase corn yield and eliminate N losses as NH3.

Dynamic patterns of circular and linear RNAs in maize hybrid and parental lines.

Hybrid vigor, also known as heterosis, has been widely utilized in agronomic production of maize (Zea mays L.) and other crops. However, the molecular mechanisms underlying heterosis are still not fully understood. To provide a more complete understanding of the transcriptomic dynamics associated with heterosis, we collected a comprehensive set of sequence data on linear mRNA transcripts and circular RNAs (circRNAs) from seedling leaves of two widely used maize inbred lines and their F1 hybrid at the V4 growth stage. We detected over 25,000 expressed genes with more than 1200 circRNAs that showed dramatic and distinct variations in expression level across the three genotypes. Although most linear and circular transcripts exhibited additive expression in the hybrid, the expression of circRNAs was more likely to be nonadditive. Interestingly, the levels of linear transcripts and their corresponding circRNAs from the same loci showed a significant relationship and coordinated expression mode across all three genotypes. Notably, in the hybrid, allele-specific expression of linear transcripts was significantly associated with the expression of circRNAs from the same locus, suggesting potential regulatory cross talk between linear and circular transcripts. Our study provides a deeper understanding of dynamic variations for both the linear and circular transcriptome in a classical hybrid triplet of maize.

Dry Mass Increment, Foliar Nutrientes and Soybean Yield as Affected by Aminoacid Application

Due to the importance of soybeans worldwide, there is a constant search for products or management systems that aim to increase the productivity of this crop. In this sense, some products that have amino acids in their composition have been used, however, there is still a lack of studies that aim to show the isolated effect of amino acids on growth parameters. Therefore, the present study aimed to evaluate the effect of the application of amino acids in the treatment of seeds and of the leaf in the soybean crop. Experiments were carried out in a greenhouse and in the field with the application of glutamate, phenylalanine, cysteine, glycine as a seed treatment (ST) and also as foliar application (FA) at the V4 growth stage. The dry mass accumulation of root, stem, leaves, total and yield of a soybean crop were evaluated. In addition, leaf element concentration in leaves was also evaluated. The use of phenylalanine in ST promoted the best results on stem mass, leaves, pods and total dry mass, with an increase of up to 152%, as compared to control. This same treatment led to higher productivity, with a 46% increase in relation to the control. In relation to foliar concentration of elements, the most effective application is the one that is carried out in both modes of application (ST and FA), mainly with glutamate and glycine. Therefore, the application of amino acids, especially in seed treatment promotes the greater accumulation of dry mass and productivity in soybean plants.

Maize (Zea mays L.) Grain Yield Response to Methods of Nitrogen Fertilization

ABSTRACTIn the developing world, fertilizer application is commonly achieved by broadcasting nutrients to the soil surface without incorporation. A commonly used nitrogen (N) source is urea and if not incorporated, can sustain N losses via ammonia volatilization and lower crop yields. This study evaluated the effect of planting, N rate and application methods on maize (Zea mays L.) grain yield. An experiment with a randomized complete block design (nine treatments and three replications) was established in 2013 and 2018 in Oklahoma. The planting methods included; farmer practice (FP), Oklahoma State University hand planter (OSU-HP), and John Deere (JD) mechanical planter. Side-dress N application methods included; dribble surface band (DSB), broadcast (BR), and OSU-HP. Nitrogen was applied at the rate of 30 and 60 kg ha−1 as urea and UAN at V8 growth stage. On average, planting and applying N at 60 kg ha−1 using OSU-HP resulted in the highest yield (11.4 Mg ha−1). This exceeded check plot yield (5.59 Mg ha−1) by 104%. Nitrogen application improved grain yield by over 57% when compared to the 0-N check (8.77 Mg ha−1). Mid-season N placement below the soil surface using OSU-HP makes it a suitable alternative to improve grain yield.

First Report of Macrophomina phaseolina Causing Dry Root Rot of Chickpea (Cicer arietinum) in Serbia

HomePlant DiseaseVol. 103, No. 10First Report of Macrophomina phaseolina Causing Dry Root Rot of Chickpea (Cicer arietinum) in Serbia PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Macrophomina phaseolina Causing Dry Root Rot of Chickpea (Cicer arietinum) in SerbiaD. Živanov, S. Tančić Živanov, N. Nagl, A. Savić, S. Katanski, and D. MilićD. Živanov†Corresponding author: D. Živanov; E-mail Address: dalibor.zivanov@ifvcns.ns.ac.rshttp://orcid.org/0000-0002-1011-6715Institute of Field and Vegetable Crops, Novi Sad, SerbiaSearch for more papers by this author, S. Tančić Živanovhttp://orcid.org/0000-0001-9556-2732Institute of Field and Vegetable Crops, Novi Sad, SerbiaSearch for more papers by this author, N. NaglInstitute of Field and Vegetable Crops, Novi Sad, SerbiaSearch for more papers by this author, A. SavićInstitute of Field and Vegetable Crops, Novi Sad, SerbiaSearch for more papers by this author, S. KatanskiInstitute of Field and Vegetable Crops, Novi Sad, SerbiaSearch for more papers by this author, and D. MilićInstitute of Field and Vegetable Crops, Novi Sad, SerbiaSearch for more papers by this authorAffiliationsAuthors and Affiliations D. Živanov † S. Tančić Živanov N. Nagl A. Savić S. Katanski D. Milić Institute of Field and Vegetable Crops, Novi Sad, Serbia Published Online:24 Jul 2019https://doi.org/10.1094/PDIS-03-19-0652-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Macrophomina phaseolina (Tassi) Goid has been reported as a severe pathogen of many plants worldwide (Mengistue et al. 2015), as well as in Serbia (Tančić Živanov et al. 2018). However, there has been no formal report of M. phaseolina causing dry root rot of chickpea (Cicer arietinum L.) in Serbia. In June 2018, the first symptoms were observed on affected field plants grouped in patches on approximately 10% of chickpea plants in a 3-acre area at Rimski Šančevi, Serbia. Withering and death of aerial parts and root rot were observed on chickpea plants at the V6 growth stage. Cuttings from symptomatic root tissues of five chickpea plants were surface disinfected with 1% NaOCl solution for 5 min, rinsed three times in sterile distilled water, air dried on sterilized filter paper, and plated on potato dextrose agar (PDA) and water agar amended with 100 mg/liter of streptomycin sulfate (Sigma-Aldrich). After 7 days of incubation at 28°C in the dark, isolates were preliminarily identified according to their morphological characters, as hyaline mycelia that turned from gray to dark with age and produced black pigmentation in agar caused by masses of dark oblong microsclerotia formed 3 days after incubation (Watanabe 2010). A representative isolate (K349) was purified by a hyphal-tip transfer technique for further analyses (Leslie and Summerell 2006). To confirm the morphological identification, the rRNA internal transcribed spacer (ITS) region of the isolate K349 was amplified with universal primers ITS1 and ITS4. The resulting ITS sequence (GenBank no. MK418768.1) was used in a BLAST search of the NCBI nucleotide database and showed 100% identity with M. phaseolina isolates (e.g., GenBank nos. KJ744350.1, KP784426.1, KU831518.1, etc.). Translation elongation factor 1-alpha gene (TEF1-α) was amplified using primers EF1-728 and EF1-986, and the resulting sequence (GenBank no. MK430416) had 97.2 to 99.5% identity with M. phaseolina isolates (e.g., GenBank nos. MH000354.1, MG434668.1, KX400854.1, etc.). After the amplification with primers MpKF1 and MaKR1, specific for M. phaseolina (Babu et al. 2007), a 350-bp PCR fragment was obtained, indicating that the isolate K349 was indeed M. phaseolina. The pathogenicity was confirmed according to Koch’s postulates. Chickpea seeds were surface disinfected with 1% NaOCl, air dried, and planted in 10-cm-diameter pots filled with sterilized potting mixture. In total, 10 plants (one per pot) were maintained in the growth chamber at a constant temperature of 25°C, 14-h photoperiod, with relative humidity 100%. Eight-day-old plants were inoculated with three PDA plugs of 5 mm diameter around the exposed stem base of each plant and covered with sterile soil mixture. PDA plugs without mycelia were used for control plants. After inoculation, plants were incubated under growth chamber conditions at 28°C with 14-h photoperiod and watered regularly. The first symptoms observed were wilting leaves and discoloration around the stem base 16 days after inoculation, whereas the control plants remained symptomless. The pathogen was successfully reisolated from the stem base and confirmed as M. phaseolina. To the best of our knowledge, this is the first report of M. phaseolina causing root rot on chickpea in Serbia.The author(s) declare no conflict of interest.

Boron fertilization enhances photosynthesis and water use efficiency in soybean at vegetative growth stage

Influence of boron (B) on photosynthesis and water use has not sufficiently been evaluated in soybean despite its worldwide importance as a crop. The objective of this work was to evaluate the effects of B application on photosynthesis and water use in soybean at vegetative growth stage. A pot experiment was carried out in a greenhouse. Soybean [Glycine max (L.) Merrill cv. M8644 IPRO] was grown in a clayey Oxisol previously fertilized with 4 B rates (0, 1.5, 3.0, and 6.0 mg dm−3). Net photosynthesis rate (Pn), intercellular CO2 concentration (Ci), transpiration rate (E), stomatal conductance (gs) were measured in the second trifoliate leaf of plants at the V4 growth stage. Instantaneous water use efficiency (WUEis = Pn/E) and intrinsic water use efficiency (WUEic = Pn/gs) were calculated. B application to soil increased all these variables. The most consistent increases were in Pn, WUEis, and WUEic. The critical level of hot water extractable B in soil that maximized photosynthesis and optimized water use by soybean at vegetative growth stage was calculated to be 0.38 mg dm−3.

Relationship of Drone‐Based Vegetation Indices with Corn and Sugarbeet Yields

Successful adoption of drone‐based remote sensing depends on changes in sensitivity over vegetation indices (VIs) and growth stage(s). During 2017–2018, experiments were conducted to relate between vegetation indices and corn (Zea mays L.) and sugarbeet (Beta vulgaris L.) yields in western Minnesota. Aerial images were collected using an unmanned aerial vehicle (UAV) equipped with a passive light optical sensor (Micasense RedEdge). Using Pix4D software, spectral reflectance data were derived from flights at V6 and VT growth stages of corn, and V10 and V15 growth stages of sugarbeet in 2017. In 2018, images were collected every week from the V4 to R2 growth stages in corn, and from the V4 to V15 stages in sugarbeet. In addition to red normalized vegetation index (RNDVI) and red edge normalized vegetation index (RENDVI), crop height was determined from UAV based digital terrain and digital surface models. Yield prediction (YP) model was derived from the linear regression between crop yield and vegetation indices. For corn‐YP model, R2 value increased over the growing period and optimized at the R1 growth stage. Considering 3 site‐years, RENDVI was the best predictor for corn YP than other VIs based on the maximum R2 value. For sugarbeet YP, model R2 value declined over the growing season and optimized at V7 or V10 growth stages. Considering 4 site‐years, RNDVI was best related to root yield and recoverable sugar yield. Drone‐based remote sensing can be successfully used for corn and sugarbeet YP. Drone‐based remote sensing has potential in corn and sugarbeet YP, but it varied over growing seasons.Core Ideas Drone‐based passive optical sensor can be used to predict crop’s yield. Red‐ and red edge‐normalized vegetation index and crop height are potential indices. Red edge normalized vegetation index best correlated with corn yield. Red normalized vegetation index best correlated with root yield prediction. Over growing season predictability improved for corn but declined for sugarbeet.

Corn Response to Sulfur Fertilizer in the Red River Valley

The recent incidence and severity of sulfur (S) deficiency due to a decrease in atmospheric S deposition and greater S removal by crops requires reevaluating current S recommendation for corn (Zea mays L.). Ten on‐farm field trials were conducted to evaluate corn response to S additions at sites in the Red River Valley of North Dakota and Minnesota between 2016 and 2017. Sulfur rates of 0, 11, 22, 33, 44 kg S ha–1 as granular (NH4)2SO4 were broadcasted and incorporated prior to corn planting using randomized complete block design with four replications. Plant tissue S concentration and N/S ratios were determined at two corn growth stages (V6 and V12 in 2016, V12 and R1 in 2017) and grain yield was measured at harvest. Plant tissue S did not increase with S fertilizer at V6 and V12 stages in 2016 whereas in 2017, tissue S increased with 11 kg S ha–1 at two sites in the V6 growth stage. Yield was not related to both soil S and plant parameters. Corn yield increased with 11 kg S ha–1 fertilizer rate at two of ten locations. Lack of response at the remaining sites suggests that S from organic matter and mineralization was enough for crop growth and hence applied fertilizer S had no effect on yield.Core Ideas Corn grain yield increased with S fertilizer at two of ten sites. No response to S fertilizer occurred due to dry early growing season. Plant tissue tests were not reliable indicators in predicting response.

The critical weed-free period in glyphosate-resistant soybean in Ontario is similar to previous estimates using glyphosate-susceptible soybean

A study consisting of 13 field experiments was conducted during 2014–2016 in southwestern Ontario and southcentral Nebraska (Clay Center) to determine the effect of late-emerging weeds on the yield of glyphosate-resistant soybean. Soybean was maintained weed-free with glyphosate (900 g ae ha−1) up to the VC (cotyledon), V1 (first trifoliate), V2 (second trifoliate), V3 (third trifoliate), V4 (fourth trifoliate), and R1 (beginning of flowering) growth stages, after which weeds were allowed to naturally infest the soybean plots. The total weed density was reduced to 24%, 63%, 67%, 72%, 76%, and 92% in Environment 1 (Exeter, Harrow, and Ridgetown) when soybean was maintained weed-free up to the VC, V1, V2, V3, V4, and R1 soybean growth stages, respectively. The total weed biomass was reduced by 33%, 82%, 95%, 97%, 97%, and 100% in Environment 1 (Exeter, Harrow, and Ridgetown) and 28%, 100%, 100%, 100%, 100%, and 100% in Environment 2 (Clay Center) when soybean was maintained weed-free up to the VC, V1, V2, V3, V4, and R1 stages, respectively. The critical weed-free periods for a 2.5%, 5%, and 10% yield loss in soybean were the V1–V2, VC–V1, and VC–V1 soybean stages in Environment 1 (Exeter, Harrow, and Ridgetown) and V2–V3, V2–V3, and V1–V2 soybean stages in Environment 2 (Clay Center), respectively. For the weed species evaluated, there was a minimal reduction in weed biomass (5% or less) when soybean was maintained weed-free beyond the V3 soybean growth stage. These results shows that soybean must be maintained weed-free up to the V3 growth stage to minimize yield loss due to weed interference.

Preemergence herbicide delays the critical time of weed removal in popcorn

AbstractUnderstanding the critical time of weed removal (CTWR) is necessary for designing effective weed management programs in popcorn production that do not result in yield reduction. The objective of this study was to determine the CTWR in popcorn with and without a premix of atrazine and S-metolachlor applied PRE. Field experiments were conducted at the University of Nebraska–Lincoln, South Central Agricultural Laboratory near Clay Center, NE in 2017 and 2018. The experiment was laid out in a split-plot design with PRE herbicide as the main plot and weed removal timing as the subplot. Main plots included no herbicide or atrazine/S-metolachlor applied PRE. Subplot treatments included a weed-free control, a non-treated control, and weed removal timing at V3, V6, V9, V15, and R1 popcorn growth stages and then kept weed free throughout the season. A four-parameter log-logistic function was fitted to percentage popcorn yield loss and growing degree days separately to each main plot. The number of growing degree days, when 5% yield loss was achieved, was extracted from the model and compared between main plots. The CTWR was from the V4 to V5 popcorn growth stage in absence of PRE herbicide. With atrazine/S-metolachlor applied PRE, the CTWR was delayed until V10 to V15. It is concluded that, to avoid yield loss, weeds must be controlled before the V4 popcorn growth stage when no PRE herbicide is applied, and PRE herbicide, such as atrazine/S-metolachlor in this study, can delay the CTWR until the V10 growth stage.

Does Irrigated Corn Require Multiple Applications of Sulfur?

Sulfur is applied to irrigated corn (Zea mays L.) grown on sandy soils. The objective of this study was to evaluate the sprinkler‐irrigated corn response to S. Treatments were a factorial combination of 0, 14, 28, and 42 kg S ha−1 as (NH4)2SO4 applied on the soil surface at four locations at planting and in season (V5). Tissue samples were collected at V8 and R2 and evaluated along with corn grain yield and soil pore water SO42––S concentration measured at 60 cm with suction tube lysimeters. Application of S increased V8 plant mass, V8 whole plant S concentration and S uptake, and R2 leaf S concentration but did not increase corn grain yield. Decreased V8 plant mass was a result of S deficiency and was only corrected when some S was applied at planting. A total of 28 kg S ha−1 was sufficient to ensure adequate plant growth and S uptake whether S was applied at planting, in‐season, or as a combination of the two timings. Concentrations of S were elevated in soil pore water from at planting and in‐season S application indicating a portion of the S applied were still available for most—and at the end of—the growing season. Sulfur fertilizer is crucial early in the growing season for irrigated corn to ensure optimal corn growth. Rate of application is more important than time of S application in irrigated corn production. Incidental applications of S may reduce the need of S fertilizer for irrigated corn.Core Ideas Application of sulfur at planting is required to maximize early irrigated corn plant mass. Delaying sulfur application to the V5 growth stage results in luxury uptake of S in corn. Rate of sulfur applied is of greater importance than timing and number of applications. Sulfur applied at planting will not fully leach from the root zone the year of application. Sulfur fertilizer may not be required to achieve maximum grain yield for irrigated corn.

Corn (Zea mays L.) response to sublethal rates of paraquat and fomesafen at vegetative growth stages

AbstractResearch was conducted from 2013 to 2015 across three sites in Mississippi to evaluate corn response to sublethal paraquat or fomesafen (105 and 35 g ai ha−1, respectively) applied PRE, or to corn at the V1, V3, V5, V7, or V9 growth stages. Fomesafen injury to corn at three d after treatment (DAT) ranged from 0% to 38%, and declined over time. Compared with the nontreated control (NTC), corn height 14 DAT was reduced approximately 15% due to fomesafen exposure at V5 or V7. Exposure at V1 or V7 resulted in 1,220 and 1,110 kg ha−1 yield losses, respectively, compared with the NTC, but yield losses were not observed at any other growth stage. Fomesafen exposure at any growth stage did not affect corn ear length or number of kernel rows relative to the NTC. Paraquat injury to corn ranged from 26% to 65%, depending on growth stage and evaluation interval. Corn exposure to paraquat at V3 or V5 consistently caused greater injury across evaluation intervals, compared with other growth stages. POST timings of paraquat exposure resulted in corn height reductions of 13% to 50%, except at V7, which was most likely due to rapid internode elongation at that stage. Likewise, yield loss occurred after all exposure times of paraquat except PRE, compared with the NTC. Corn yield was reduced 1,740 to 5,120 kg ha−1 compared with the NTC, generally worsening as exposure time was delayed. Paraquat exposure did not reduce corn ear length, compared with the NTC, at any growth stage. However, paraquat exposure at V3 or V5 was associated with reduction of kernel rows by 1.1 and 1.7, respectively, relative to the NTC. Paraquat and fomesafen applications near corn should be avoided if conditions are conducive for off-target movement, because significant injury and yield loss can result.

The impact of climatic factors on the relative chlorophyll content and yield of a maize hybrid in a long-term experiment

The impact of the climatic factors of crop year on the relative chlorophyll content of maize was examined for three years. The examinations were carried out on the Látókép Experiment Site of the University of Debrecen on calcareous chernozem soil in a small-plot, non-irrigated long-term field experiment with strip plot design. In addition to a non-fertilised (control) treatment, nitrogen (N) fertiliser doses were applied as base and top dressing. The 60 and 120 kg N ha-1 base dressing doses were followed by two top dressing doses at the V6 and V12 phenophases.
 Averaged over the different fertiliser treatments, SPAD readings increased in all three years as the growing season progressed. The highes SPAD value increase was observed in the average crop year (2017) at the V12 phenophase (11.8), which further increased at the R1 phenophas, by 3,7. No significant Spad value difference was observed between the average (2017) and the dry year (2018) at the V6 growth phase. However, in the wet crop year (2016), the V690 treatment provided the statistically highest relative chlorophyll content (46.8). At the V12 phenophase, the base dressing dose of 120 kg N ha-1+30 kg N ha-1 (V6150) showed to be successful in two years (2016 and 2018), while in 2017, the base dressing dose of A60 was successful. The impact of crop year on relative chlorophyll content can be clearly shown at the R1 growth stage. In all three years, the significantly highest relative chlorophyll content could be achieved at different nutrient levels: A60 in 2016, V6150 in 2017 and V690.
 In a wet year (2016), higher yield could be achieved as a result of the 60 kg N ha-1 base dressing and 30 kg N ha-1 at the V6 growth stage (V690) as top dressing in comparison with 2017 and 2018, when higher fertiliser dose (120 kg N ha-1 base dressing and 30 kg N ha-1top dressing at the V6 growth stage) was needed to achieve a significant yield surplus.
 Altogether, averaged over the different treatments, the highest yield (12.48 t ha-1) was observed in the wet year, when the relative chlorophyll content was also the highest (50.6).