V6 Growth Research Articles

Direct Infusion Metabolomics of the Photosystem and Chlorophyll Related Metabolites within a Drought Tolerant Plant Introduction of Glycine max.

Drought is the most prolific form of abiotic stress that legumes and cereal plants alike can endure, and the planting of an improper cultivar at the beginning of a season can cause unexpected losses up to fifty percent under water deficient conditions. Herein, a plant introduction (PI) of an exotic cultivar of soybean (Glycine max), PI 567731, which demonstrates a slow wilting (SW) canopy phenotype in maturity group III, was profiled under drought conditions in field trials in Missouri against a drought susceptible check cultivar, Pana. Metabolomic profiling was carried out on samples of leaves from each of these cultivars at V5 and R2 growth stages both while irrigated and while under drought stress for three weeks. PI 567731 was observed to have differential phytochemical content, and enhanced levels of chlorophyll (Chl) a/b and pheophytin (Pheo) were profiled by direct infusion electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Indicating drought induced changes of the photosystem and photosynthetic capabilities alongside water preservation strategies are important within the SW phenotype drought response. Subsequent multivariate analysis was able to form predictive models, encompassing the variance of growth and drought stress of the cultivar. Moreover, the existence of unique Chl-related metabolites (CRM) (m/z > 900) were confirmed through tandem mass spectrometry. The resultant coordination of fatty acids to the core of the porphyrin ring was observed and played an unknown role in the proliferation of the photosynthesis. However, the relative ratio of the most abundant CRM is undisturbed by drought stress in PI 567731, in contrast to the drought susceptible cultivar. These results provide key insights into drought related metabolic mechanisms.

Vegetation sensors as a tool for plant population identification and corn grain yield estimation

ABSTRACT The estimated corn grain yield is dependent on plant density and should be monitored from the beginning of its development, especially between the phenological stages V3 and V10, since these stages are more responsive to management strategies. This study aimed to evaluate the efficiency of two methods [normalized difference vegetation index (NDVI) and plant occupation index (POI)] to estimate the density of corn plants, in order to identify the plant population in different phenological stages and corn grain yield. Two field experiments were conducted in two crop seasons and treatments consisted of four plant densities (4, 6, 8 and 10 plants m-2). The NDVI measurements of the vegetative canopy were performed in the growth stages V4, V5, V6, V7, V8 and V9 (2014) and V3, V5, V6, V8, V9, V10 and V13 (2015/2016). For the POI, the measurements were performed in the stages V5, V6, V8 and V9, in both crop seasons. The different plant densities were efficient in generating variability in the NDVI and POI values throughout the corn crop development cycle, and both tools were efficient in identifying density variations. It was observed that these tools should be used between the V4 and V9 growth stages.

Intra-seasonal activity of ground dwelling spiders following six years of tillage, fertiliser and weeding treatments in an agricultural field in northern Zimbabwe

Spiders are important biological control agents whose activity and diversity can be negatively affected by agricultural practices. A study was conducted at Chinhoyi University of Technology experimental farm, northern Zimbabwe, to determine the impact of tillage, fertiliser application and weeding regimes on ground-dwelling spiders across three maize crop growth stages (early vegetative: V3; late vegetative: V6; and intermediate reproductive: R2). Lycosidae were the most abundant spider family (85.7%) while Salticidae were least abundant (0.8%). The spiders belonged to two functional groups, ground and plant wanderers with the former constituting 94.9% of pitfall catches. Spiders were most abundant during V3, followed by R2 and V6 maize growth stages. Spider community diversity was also greatest during the V3 (H′ = 0.45) and least during the V6 stage (H′ = 0.12). During the V3 and R2 stages, ground dwelling spider abundance was higher in the two reduced tillage systems than under conventional tillage. Based on the study findings, it can be concluded that reduced tillage is useful in increasing ground-dwelling spider community abundance and diversity during the V3 and R2 maize growth stages.

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.

Influence of Plant Growth-Promoting Rhizobacteria on Corn Growth Under Different Fertility Sources

ABSTRACTA greenhouse study was conducted to evaluate the effects of plant growth-promoting rhizobacteria (PGPR) on root establishment and biomass production of corn (Zea mays L.) using three fertility sources (poultry litter (PL), biosolids, and urea). Applying PL significantly improved root morphological parameters and increased plant biomass at the V4, V6, and VT growth stages when compared to the other fertility sources. At the V4 stage, PGPR stimulated root growth and enhanced aboveground biomass with urea and PL, while no differences were observed with biosolids. At the V6 stage, PL, biosolids, and urea with PGPR significantly increased some growth parameters (e.g., plant height, leaf area, and root morphology). However, at the VT stage, PGPR’s influence on plant growth was minimal regardless of fertility source. Applying the fertility sources at 135 kg N ha−1 may have masked PGPR’s influence on corn growth as the plants reached their later vegetative growth stages.

Maize Growth and Yield Response to a Biostimulant Amendment

ABSTRACTVarious companies are marketing biostimulant products with claims of higher yields and improved quality. Greenhouse and field experiments were conducted from 2010–2013 to determine the influence of Foliar Blend® (FB, Agri-Gro Marketing, Inc., Doniphan, MO), a chelated micronutrient/biostimulant amendment, on the growth and seed yield of maize (Zea mays L.). When applied pre-emergence and again at V5 growth, greenhouse-grown maize seedling heights and leaf area increased at 2.34 L FB/ha or greater and root and shoot dry matter increased at 7 L FB/ha compared with untreated plants. In field studies, maize yields increased at 2.34 L FB/ha or greater in 2011. In 2012, yields improved with FB but not significantly. Primary ear heights at 1.2 L FB/ha and 2.34 L FB/ha were greater than the control in 2011 but not in 2012. We conclude that FB can alter maize growth, but yield responses are inconsistent and possibly related to environmental interactions.

Comparison of two ground-based active-optical sensors for in-season estimation of corn (Zea mays, L.) yield

ABSTRACTThirty field experiments were conducted in North Dakota during 2011 and 2012 to compare two ground-based active-optical sensors for their relationship between sensor readings and INSEY (in-season estimate of yield). The experimental design at each site was a randomized complete block with four replications and six nitrogen (N) rate treatments: control, 45, 90, 134, 179, and 224 kg ha−1 applied pre-plant as ammonium nitrate within five days of planting. The two sensors, GreenSeeker® (Trimble, Sunnydale, CA, USA) (GS) and Crop Circle ACS 470® sensor (Holland Scientific, Lincoln, NE, USA) (CC) were used to scan over the top of the corn at V6 and V12 growth stages. The GS INSEY and the CC INSEY were similarly related to corn yield at V6. The CC using the red-edge lens option improved the INSEY relationship to corn yield compared to the GS or the CC using the red lens option at V12.

Optical sensing estimation of leaf nitrogen concentration in maize across a range of water-stress levels

Optical sensing techniques offer an instant estimation of leaf nitrogen (N) concentration during the crop growing season. Differences in plant-moisture status, however, can obscure the detection of differences in N levels. This study presents a vegetation index that robustly measures differences in foliar N levels across a range of plant moisture levels. A controlled glasshouse study with maize (Zea mays L.) subjected to both water and N regimes was conducted in Ottawa, Canada. The purpose of the study was to identify spectral waveband(s), or indices derived from different wavebands, such as the normalised difference vegetation index (NDVI), that are capable of detecting variations in leaf N concentration in response to different water and N stresses. The experimental design includes three N rates and three water regimes in a factorial arrangement. Leaf chlorophyll content and spectral reflectance (400–1075 nm) were measured on the uppermost fully expanded leaves at the V6, V9 and V12 growth stages (6th, 9th and 12th leaves fully expanded). N concentrations of the same leaves were determined using destructive sampling. A quantitative relationship between leaf N concentration and the normalised chlorophyll index (normalised to well fertilised and well irrigated plants) was established. Leaf N concentration was also a linear function (R2 = 0.9, P < 0.01) of reflectance index (NDVI550, 760) at the V9 and V12 growth stages. Chlorophyll index increased with N nutrition, but decreased with water stress. Leaf reflectance at wavebands of 550 ± 5 nm and 760 ± 5 nm were able to separate water- and N-stressed plants from normal growing plants with sufficient water and N supply. Our results suggest that NDVI550, 760 and normalised chlorophyll index hold promise for the assessment of leaf N concentration at the leaf level of both normal and water-stressed maize plants.

Determining the Optimal Timing of Foliar Insecticide Applications for Control of Soybean Aphid (Hemiptera: Aphididae) on Soybean

Field experiments were performed over 3 yr to examine the impact of insecticide application timing to control soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), populations and to prevent soybean yield losses. Experiments were conducted in early and late-planted soybean, Glycine max (L.) Merr. Insecticide applications were made based on soybean growth stages. In 2001, applications were made at V1, V3, R2, and R3 growth stages; in 2002 and 2003, applications were made at R2, R3, and R4 stages. Additional treatments consisted of an unsprayed control and a multiple spray treatment that received insecticide applications at 7-10-d intervals. Soybean aphid densities were recorded throughout the growing season, and yields were measured. Soybean aphid populations varied considerably across years and planting dates. In general, late-planted soybean exhibited higher aphid pressure than early planted soybean, and experiments in 2002 had lower aphid numbers than those in 2001 and 2003. The multiple spray treatment significantly increased yield over the control in four of the six experiments, the exceptions being 2002 late planted and 2003 early planted. This suggests that soybean aphid populations were not large enough to cause yield losses in these two experiments. The R3 spray treatment increased yield in three of the six experiments (2001 late planting, 2002 early planting, and 2003 late planting), the R2 spray treatment increased yield in two of six experiments (2001 and 2003 late plantings), and the V1 application increased yield over the control in the 2001 late-planted experiment. Results suggest that when aphid populations are high insecticide applications made at R2 and R3 plant stages are most effective in preventing yield loss.

Field Verification of the Barber–Cushman Mechanistic Phosphorus Uptake Model for Maize

A two‐year field study in southeastern South Dakota examined how phosphorus (P) fertilizer applied to a silt loam soil affected the predictability of P uptake in maize (Zea mays L.) using the Barber–Cushman mechanistic P uptake model. Liquid ammonium polyphosphate was applied to provide 0, 10, 20, and 40 kg P ha−1 comparing a concentrated single or double band application, or comparing a concentrated single band to a fertilizer band diluted with water. Soil, plant tissue, and roots were sampled intensely. The model simulation used observed measurements as well as reasonable estimates and assumptions derived from the literature. Predicted P uptake was affected more by soil solution P (C li ) than applied fertilizer P rate. The agreement of observed with predicted P uptake was improved when their regressions were grouped according to C li ranges rather than applied P rates. In 1991, the model predicted 86–90% of observed P uptake at the high C li range (21–77 µmol L−1) but only predicted 23–44% of observed P uptake at the low C li range (1–16 µmol L−1) at the V6 (6th leaf) and V12 (12th leaf) growth stages. Predicted P uptake was much lower than observed at all C li ranges for the simulation period at the R2 (silking) growth stage. Parameters used in simulating maize P uptake were suitable at the high C li values up to the V12 growth stage. At low C li values at the V12 and R2 growth stages, additional soil factors that may affect maize P uptake (i.e., root hair proliferation, mycorrhizal infection, rhizosphere acidification, root architecture) should be included in a simulation model to improve P uptake predictability.

Iron Deficiency Chlorosis and Seed Yield in Dry Edible Beans Grown on High-pH Calcareous Soils

Iron deficiency chlorosis (FeDC) can cause significant seed yield reduction in dry beans (Phaseolus vulgaris L.) grown on high-pH calcareous soils. To determine the effects of FeDC on seed yield, and the effect of Fe-spray as a correction factor for FeDC, 22 breeding lines/cultivars were planted on high-pH (8.0), calcareous (3.2–3.5 calcium carbonate equivalent), and low-Fe (1.8–4.2 ppm DTPA) sandy clay loam Tripp soils at Mitchell and Scottsbluff in western Nebraska. A split-plot design was used with Fe treatments as main plots and breeding lines/cultivars as subplots. Three foliar sprays of Fe-EDDHA (2.4 kg·ha–1) were applied at V4, R5, and R7 dry bean growth stages, during 1996 and 1997. Leaf chlorosis was measured simultaneously by using a Minolta Chroma-meter (CIE L* a* b* color space system), a Minolta Chlorophyll-meter (chlorophyll content index), and by visual ratings (1 = normal green to 5 = severe chlorosis). In 1996 no significant Fe-spray × line interaction (P = 0.776) and Fe-spray effect (P = 0.884) on seed yield was observed. Breeding lines showed significant differences in seed yield (P = 0.0001) with WM2-96-5 being the highest-yielding line (4047 kg·ha–1). In 1997 a significant Fe spray × line interaction (P = 0.029) was observed. The cultivar Chase without Fe spray (3375 kg·ha–1), and lines WM2-96-5 (3281 kg·ha–1), WM2-96-8 (3171 kg·ha–1) with Fe spray were the highest yielding entries under those treatments. Differences in visual ratings after the third Fe spray in 1997 were significant (P = 0.004) for Fe spray × line interaction. In 1996 visual ratings were different only for breeding lines. Chlorophyll content index showed a significant Fe spray × line interaction after the second Fe spray (P = 0.022) and after the third Fe spray (P = 0.0003) in 1997.

Controlling Kochia (Kochia scoparia) in Soybean (Glycine max) with Postemergence Herbicides

POST herbicides were applied at four soybean growth stages to evaluate their effect on triazine-resistant (TR) kochia in 1991, 1992, and 1993. Applying imazethapyr at 70 g ai/ha or bentazon plus imazethapyr at 1,120 plus 70 g ai/ha controlled 75 to 100% of 1- to 13-cm-tall TR kochia consistently across growth stages and years. Acifluorfen at 560 g ai/ha, chlorimuron at 13 g ai/ha, or chlorimuron plus thifensulfuron at 4 plus 4 g ai/ha controlled 68 to 96% of 1- to 2-cm-tall TR kochia at soybean growth stage VC to V1, and control was inconsistent at later growth stages. In most instances, soybean seed yield was greater with herbicides applied at the V1 or V2 growth stage of soybean compared with the V4 and V5 growth stage because of better weed control. No wheat yield reduction occurred because of herbicide carryover in 1992 and 1994. However, in 1993, imazethapyr and bentazon plus imazethapyr treatments applied in 1992 caused 22% injury and reduced winter wheat yield 10% when wheat was planted after soybean harvest.

Total Postemergence Herbicide Programs in Cotton (Gossypium Hirsutum) with Sethoxydim and DPX-PE350

Weed control and cotton yield with a herbicide program of sethoxydim and DPX-PE350 applied postemergence over-the-top was compared with that of a standard herbicide program of trifluralin applied PPI plus fluometuron applied PRE plus methazole and MSMA applied postemergence-directed. Control of pitted and entireleaf morningglory, smooth pigweed, and prickly sida was similar with the postemergence over-the-top program and the standard herbicide program when DPX-PE350 was applied to cotton in the V2 or V4 growth stages. Less weed control and lower yield were observed when DPX-PE350 was applied to V6-stage cotton. Good control of annual grasses was obtained with all herbicide programs.

Effect of Adjuvants on Weed Control and Soybean (Glycine max) Tolerance with AC 263,222

Field experiments were established to observe the effects of adjuvants and time of application on weed control and ‘Terra-Vig 515’ soybean tolerance with POST applications of AC 263,222. A nonionic surfactant or a crop oil concentrate increased sicklepod control with AC 263,222 applied at either V2 or V6 soybean growth stages. Sicklepod control increased as AC 263,222 was increased from 35 to 70 g ai ha–1only when applied without an adjuvant. Late in the season, there was no difference in sicklepod control between V2 and V6 applications. Adjuvants and application timing within herbicide treatments had no effect on pitted morningglory control, and, though adjuvants increased common cocklebur control, all treatments controlled more than 85% of both species. AC 263,222 with adjuvants at all rates and timings injured and stunted soybean more 2 wk after treatment compared to AC 263,222 alone. AC 263,222 at 35 or 70 g ha–1with crop oil concentrate reduced yields more than AC 263,222, with either a surfactant or no adjuvant when applied to V2 soybeans.

INFLUENCE OF SINGLE STRAINS AND A COMMERCIAL MIXTURE OF Bradyrhizobium japonicum ON GROWTH, NITROGEN ACCUMULATION AND NODULATION OF TWO EARLY-MATURING SOYBEAN CULTIVARS

Seven single strains and a commercial mixture of Bradyrhizobium japonicum were evaluated in association with two early-maturing Canadian soybean (Glycine max (L.) Merrill) cultivars, Maple Presto and Maple Amber. Inoculated and uninoculated plants were grown in pails outdoors. Soil temperature at 15 cm depth was monitored throughout the experiment. At the V2, V3, R2 and R4 growth stages, whole plants were removed from the pails. Nodules were counted and weighed; roots and tops were separated, weighed and analyzed for total nitrogen. Bradyrhizobium japonicum strains 61A148, 61A196, 61A194 and 61A155 were similar in effectiveness, but superior to strains 61A124a, 61A118b, 61A101c and the commercial mixture in earliness of nodule formation, number and weight of nodules per plant, and in promoting greater root and top growth and plant nitrogen accumulation. There were indications that soil temperature may have affected nodulation. Maple Amber showed the greater potential for symbiotic nitrogen fixation. This cultivar supported earlier nodulation, had a greater number of nodules, accumulated more nitrogen in the tops and roots and had greater growth than Maple Presto.Key words: Soybean, Glycine max (L.) Merrill, soil temperature, soybean growth stages, Bradyrhizobium, nodulation