Flag Leaf Emergence Research Articles

Response of grain sorghum to low rates of glufosinate and nicosulfuron

AbstractPrevious research has shown that glufosinate and nicosulfuron at low rates can cause yield loss to grain sorghum. However, research has not been conducted to pinpoint the growth stage at which these herbicides are most injurious to grain sorghum. Therefore, field tests were conducted in 2016 and 2017 to determine the most sensitive growth stage for grain sorghum exposure to both glufosinate and nicosulfuron. Field test were designed with factor A being the herbicide applied (glufosinate or nicosulfuron). Factor B consisted of timing of herbicide application including V3, V8, flagleaf, heading, and soft dough stages. Factor C was glufosinate or nicosulfuron rate where a proportional rate of 656 g ai ha−1 of glufosinate and 35 g ai ha−1 of nicosulfuron was applied at 1/10×, 1/50×, and 1/250×. Visible injury, crop canopy heights (cm), and yield were reported as a percent of the nontreated. At the V3 growth stage visible injury of 32% from the 1/10× rate of glufosinate and 51% from the 1/10× rate of nicosulfuron was observed. This injury was reduced by 4 wk after application (WAA) and no yield loss occurred. Nicosulfuron was more injurious than glufosinate at a 1/10× and 1/50× rate when applied at the V8 and flagleaf growth stages resulting in death of the shoot, reduced heading, and yield. Yield losses from the 1/10× rate of nicosulfuron were observed from V8 through early heading and ranged from 41% to 96%. Yield losses from the 1/50× rate of nicosulfuron were 14% to 16% at the flagleaf and V8 growth stages respectively. The 1/10× rate of glufosinate caused 36% visible injury 2 WAA when applied at the flagleaf stage, which resulted in a 16% yield reduction. By 4 WAA visible injury from either herbicide at less than the 1/10× rate was not greater than 4%. Results indicate that injury can occur, but yield losses are more probable from low rates of nicosulfuron at V8 and flagleaf growth stages.

Winter wheat growth assessment using Temporal Normalized Phenology Index (TNPI) in Bhuj Taluka, Gujarat State, India

In the present study on winter crop growth monitoring in Bhuj Taluka of Kachchh district was carried out using multi-temporal Sentinel-2 multi-spectral data (spatial resolution 10-m). Sentinel-2 multi-spectral data for the period from October-2018 to March-2019 was analysed in this study. The major objective of this study was to generate crop growth profiles of different crops and identify the relationships between crop phenology and crop growth stages by generating Normalized Difference Vegetation Index (NDVI) profiles of wheat and mustard crops.The results of spectral behavior of wheat (normal & late sown) and mustard during active growth stages indicated that these winter crops have distinct spectral signatures in Sentinel-2 spectral bands. The NDVI growth profiles of wheat and mustard indicate the temporal variations during different growth stages of these crops. The maximum temporal variations were observed during early growth stages to flowering & grain filling stages. The difference in sowing dates of wheat and mustard crops result in different phenological stages of these winter crops. The NDVI curve of Rabi Season-2018-19 was divided into different phenological growth phases namely, i) Phase-I: G0 (Spectral emergence) to G1(Flag leaf emergence), Phase-II: G1 (Flag leaf emergence) to Gmax (Flowering and Grain filling), Phase-III: Gmax (Flowering and Grain filling) to G2 (Dough Stage) and Phase-IV: G2 (Dough Stage) to G3 (Physiological Maturity). The temporal changes in the NDVI was analysed by computing the Temporal Normalized Phenology Index (TNPI) between different phenological phases from G0 to G3.Mean TNPI values of wheat crop for different phenological phases were computed which indicated that rising part of NDVI profile of growth phases from G0 to Gmax higher TNPI values whereas the declining part of NDVI profile of growth phases from Gmax to G3 showed lower TNPI values. The difference NDVI images were generated using the NDVI images of two different phenological phases of wheat crop which represent the temporal changes in wheat crop greenness, where “0” represents no temporal change and “1” represents the maximum temporal change in vegetation greenness across wheat crop areas in the study area.

Growth, yield, water use efficiency of wheat (Triticum aestivum) under different sowing dates, planting methods and irrigation treatments

Field experiments were conducted at the Research Farm, Department of Climate Change and Agricultural Meteorology, PAU, Ludhiana during rabi seasons of 2014-15 and 2015-16. Wheat (Triticum aestivum L.) variety WH-1105 was sown on 10th and 30th November under two planting methods (flat and bed) with three irrigation treatments (I1- three post-sowing irrigations at crown root initiation (20-25 days after sowing), flag leaf emergence (70-80 days after sowing) and soft dough stages (115-120 days after sowing), I2- I1+ fourth irrigation during last week of March (Hard dough stage) and I3- Recommended four post-sowing irrigations (crown root initiation, tillering, jointing/booting and milking) in sub-sub plots replicated four times. The experiment was planned to study the effect of sowing dates, planting methods and irrigation treatments on growth, yield and water use efficiency of wheat. Dry matter accumulation and leaf area index showed significant differences between different dates of sowing and planting methods during entire growing period however significant differences among irrigation treatments were observed at 120 DAS during both the seasons. The grain yield and water use efficiency was higher in 10th November sowing as compared to 30th November as well as under bed planting compared to flat planting. However by giving one extra irrigation during end of March under I2, the increase in grain yield was up to 6-13% over I3 and I1 treatments.

新潟県における越冬後追肥と止葉抽出期追肥の増量がオオムギ品種「はねうまもち」の収量・品質に及ぼす影響

新潟県における越冬後追肥と止葉抽出期追肥の増量がオオムギ品種「はねうまもち」の収量・品質に及ぼす影響

Nitrogen fertilizer rate and time effect on dryland no‐till hard red spring wheat production

AbstractIncreasing the efficiency of wheat (Triticum aestivum L.) production is vital for Montana growers’ sustainability and competitiveness in the market. Nitrogen fertilizer applications at the right rate and time in the growing season are important for optimizing wheat grain yield and quality. Two dryland field experiments were conducted in North Central Montana in 2014. The effects of N fertilizer rates (28, 84, and 140 kg N ha−1) and application times (seeding, tillering, jointing, and flag leaf emergence) on grain yield, test weight, protein content, protein yield, grain N uptake, and N use efficiency (NUE) were evaluated. Wheat grain yield and protein content was the highest with N fertilizer applied at 140 kg N ha−1 rate at tillering. Delaying N fertilizer until flag leaf resulted in significantly lower wheat yields and grain protein values. It is possible that higher N rates would have allowed to maximize both yield and protein content. Nitrogen use efficiency was the highest with N fertilization at tillering and jointing. Nitrogen response trials coupled with historical yield records did not provide accurate estimates of optimum N rates. Close monitoring of crop nutrient status throughout the growing season (using destructive sampling and/or crop sensors), coupled with appropriate preplant soil testing, and splitting N applications to tailor N supply with crop demand should help to improve NUE.

The Timing of Application and Inclusion of a Surfactant Are Important for Absorption and Translocation of Foliar Phosphoric Acid by Wheat Leaves.

Introduction: Foliar applied phosphorus (P) has the potential to provide a more tactical approach to P fertilization that could enhance P use efficiency. The aims of this study were to investigate the influence of adjuvant choice and application timing of foliar applied phosphoric acid on leaf wettability, foliar uptake, translocation, and grain yield of wheat plants. Materials and Methods: We measured the contact angles of water and fertilizers on wheat leaves, and the uptake, translocation and wheat yield response to isotopically-labelled phosphoric acid in combination with five different adjuvants when foliar-applied to wheat at either early tillering or flag leaf emergence. Results: There was high foliar uptake of phosphoric acid in combination with all adjuvants that contained a surfactant, but only one treatment resulted in a 12% increase in grain yield and two treatments resulted in a decrease in grain yield. Despite the wettability of all foliar fertilizers being markedly different, foliar uptake was similar for all treatments that contained a surfactant. The translocation of phosphorus from foliar sources was higher when applied at a later growth stage than when applied at tillering despite the leaf surface properties that affect wettability being similar across all leaves at both growth stages. Discussion: Both the timing of foliar application and the inclusion of a surfactant in the formulation are important for absorption and translocation of phosphoric acid by wheat leaves, however high foliar uptake and translocation will not always translate to a yield increase.

Zinc oxide nanoparticles alleviate drought-induced alterations in sorghum performance, nutrient acquisition, and grain fortification

Drought is a major environmental event affecting crop productivity and nutritional quality, and potentially, human nutrition. This study evaluated drought effects on performance and nutrient acquisition and distribution in sorghum; and whether ZnO nanoparticles (ZnO-NPs) might alleviate such effects. Soil was amended with ZnO-NPs at 1, 3, and 5 mg Zn/kg, and drought was imposed 4 weeks after seed germination by maintaining the soil at 40% of field moisture capacity. Flag leaf and grain head emergence were delayed 6–17 days by drought, but the delays were reduced to 4–5 days by ZnO-NPs. Drought significantly (p < 0.05) reduced (76%) grain yield; however, ZnO-NP amendment under drought improved grain (22–183%) yield. Drought inhibited grain nitrogen (N) translocation (57%) and total (root, shoot and grain) N acquisition (22%). However, ZnO-NPs (5 mg/kg) improved (84%) grain N translocation relative to the drought control and restored total N levels to the non-drought condition. Shoot uptake of phosphorus (P) was promoted (39%) by drought, while grain P translocation was inhibited (63%); however, ZnO-NPs lowered total P acquisition under drought by 11–23%. Drought impeded shoot uptake (45%), grain translocation (71%) and total acquisition (41%) of potassium (K). ZnO-NP amendment (5 mg/kg) to drought-affected plants improved total K acquisition (16–30%) and grain K (123%), relative to the drought control. Drought lowered (32%) average grain Zn concentration; however, ZnO-NP amendments improved (94%) grain Zn under drought. This study represents the first evidence of mitigation of drought stress in full-term plants solely by exposure to ZnO-NPs in soil. The ability of ZnO-NPs to accelerate plant development, promote yield, fortify edible grains with critically essential nutrients such as Zn, and improve N acquisition under drought stress has strong implications for increasing cropping systems resilience, sustaining human/animal food/feed and nutrition security, and reducing nutrient losses and environmental pollution associated with N-fertilizers.

In sink-limited spring barley crops, light interception by green canopy does not need protection against foliar disease for the entire duration of grain filling

Disease management in cereals is heavily reliant on the use of fungicides, but development of anti-microbial resistance, effects on non-target organisms and persistence of active ingredients in the environment and food chain challenge the sustainability of this approach. Better targeting of fungicides according to crop need within an integrated pest management (IPM) programme could improve the sustainability of disease management. The objectives of the present study were to determine 1) the duration of protection of post-anthesis canopy light interception required to maximise the yield of spring barley and 2) to relate this to the response of crops to timing of fungicide applications. As the yield of spring barley is considered to be sink-limited (limited by the number and storage capacity of grains) rather than source-limited (limited by the amount of carbon assimilates available for grain filling) in many environments, we hypothesised that the canopy would not need to be protected for the entire grain filling period. Field experiments were conducted at two sites in the UK (Edinburgh and Herefordshire) over four years, providing contrasting climates and soil types. Shading was used to determine the response of grain filling to reductions in light interception over defined intervals, thereby mimicking effects of foliar disease on light interception, as shading is easier to control than the onset and duration of disease epidemics. Shades giving ˜67% reduction in photosynthetically active radiation (PAR) were erected over plots of disease-free crops at weekly intervals commencing at flowering and leaving them in place until harvest. The required duration of protection of light interception was estimated as the period from flowering to the time at which the onset of shading had no effect on yield. In a separate experiment the response to five fungicide timing treatments was determined on three relatively disease-susceptible varieties. Timings were the start of stem extension (referred to here as T1 only) and T1 followed by a second application at either flag leaf emergence (early T2), flowering (mid T2) or the start of rapid grain growth (late T2); untreated plots served as controls. Results showed that canopy PAR interception does not need to be protected for the entire grain filling period in order to maximise yield. The critical period determined from shading was 3–5 weeks after 50% ear emergence depending on the site year, or the first 72–90% of grain filling. There was a significant yield response to fungicide treatment in all site-years of 0.33−0.74 t ha−1 irrespective of the disease severity and yield potential of the site. Where disease severity was low to moderate a T1 application on its own gave sufficient protection during grain filling to maximise yield. Later applications increased healthy area PAR interception further, but effects occurred late during grain filling and did not increase yield. When disease was severe a T1 plus mid T2 application was required to protect PAR interception during the critical early to mid- grain filling period. These results provide the necessary physiological understanding to help target fungicide applications according to crop need.

Sensitivity and Recovery of Grain Sorghum to Simulated Drift Rates of Glyphosate, Glufosinate, and Paraquat

A field experiment was conducted in 2017 and 2018 to evaluate the sensitivity and recovery of grain sorghum to the simulated drift of glufosinate, glyphosate, and paraquat at two application timings (V6 and flag leaf growth stage). Paraquat drift caused maximum injury to sorghum plants in both years, whereas the lowest injury was caused by glyphosate in 2017. Averaged over all herbicide treatments, injury to grain sorghum from the simulated herbicide drift was 5% greater when herbicides were applied at flag leaf stage, as compared to herbicide applications at the six-leaf stage in 2017. In 2018, injury from glyphosate drift was higher when applied at the six-leaf stage than at the flag leaf stage. Paraquat and glufosinate drift caused more injury when applied at flag leaf stage than at six-leaf stage at 14 days after application in 2018. About 21% to 29% of injury from the simulated drift of paraquat led to a 31% reduction in grain sorghum yield, as compared to a nontreated check in 2017. The simulated drift of glyphosate and glufosinate did not result in any significant yield reduction compared to the nontreated check in 2017, possibly due to the recovery of sorghum plants after herbicides’ drift application.

Control of net form of net blotch in barley from seed- and foliar-applied fungicides

Net form of net blotch (NFNB), caused by Pyrenophora teres f. teres, is a major foliar disease of barley (Hordeum vulgare L.) worldwide that can cause grain yield and quality loss in susceptible varieties. Seed- and foliar-applied fungicides were evaluated in six field experiments infected with NFNB during 5 years, for suppression of NFNB severity and protection of grain yield and quality. Suppression of NFNB severity varied between treatments and experiments. Grain yield and quality improvements were recorded in two experiments. Foliar fungicide applications at stem elongation (Zadoks growth stage Z31) and flag leaf emergence (Z39) or ear emergence (Z55) significantly reduced NFNB severity, increased grain yield by up to 23%, and improved grain-quality measurements of retention, screenings and weight. The seed-applied fungicide fluxapyroxad provided significant reductions in NFNB severity, improvements in grain yield of up to 20%, and improved grain quality. Where NFNB was severe, none of the seed or foliar fungicide application strategies provided complete control of NFNB, indicating that more than two applications were necessary when conditions were favourable for disease development in susceptible varieties.

Yield response to plant density, row spacing and raised beds in low latitude spring wheat with ample soil resources: An update

This paper reviews the results of published and unpublished experiments over 30 years looking at the effect on yield of planting density and row spacing, and of raised bed planting, of modern irrigated short wheat cultivars under the favourable climatic conditions of northwest Mexico. With optimum planting dates (mid Nov. to mid Dec.), regardless of row spacing, wheat yield was remarkably insensitive to planting density within the range normally studied (80–400 plants/m2). However yield was sensitive to row spacing: the most sensitive cultivars (erect dwarf cultivars) lost yield at spacing 30 cm and greater, while the least sensitive (some taller vigorous semidwarf cultivars) tolerated spacing up to at least 50cm without yield loss. Yield sensitivity to wide spacing was unaffected by density but varied between years, being less in favourable cooler years, and was markedly greater with later plantings (Jan.). The response to yield on narrow raised beds (2–3 rows per bed, 75–90 cm between bed centres), which have many agronomic advantages, could be explained by the aforementioned yield responses to spacing, in this case the furrow gap or distance between rows on adjacent beds being critical. Yield testing with a furrow gap of 44–50 cm appeared to select cultivars more suited to this system, but it wasn’t clear whether such cultivars represented the best option under normal 20 cm row spacing in the absence of raised beds. When testing was extended to very low plant densities, yield was remarkably insensitive (maximum yield often achieved with only 16/m2), provided the planting date was normal and the planting arrangement did not deviate greatly from a square grid, with the honeycomb design giving an additional small yield advantage.These yield responses reflect the great plasticity in wheat imparted especially by tillering, and appear to be reasonably well explained by the notion that maximum yield requires close to full light interception no later than just before flag leaf emergence, being the onset of dry weight accumulation in growing spikes. Greater leaf greenness and probably higher radiation use efficiency with very low densities (and wide gaps), and associated delays in 50% flowering, may also assist in compensation for gaps. In contrast to much conventional wisdom, it is suggested that a worthwhile breeding objective would be selection for high per spaced-plant yield, with a view to achieving normal (or better) commercial yields at very low plant densities (< 20/m2), thereby opening up opportunities for new breeding and agronomic strategies in this era of precision cropping.

Male sterility induction of sorghum using chemical hybridizing agent TFMSA, trifluoromethanesulfonamide

In sorghum, male sterility has been induced mainly using mechanical and genetic means with minimal use of chemical methods. Mechanical sterility induction is limited to producing small quantities of seed and genetic male sterility is limited to specific germplasm. An effective chemical hybridizing agent could be used to produce large amounts of seed and would not be limited by genotypes. The chemical trifluoromethanesulfonamide (TFMSA) was evaluated as a male gametocide in sorghum. In greenhouse conditions, TFMSA induced varying degrees of male sterility contingent on the dosage, timing of application, and sorghum genotype. If applied at or after the flag leaf emergence, panicles were male fertile but male sterile when applied at least 2 d before the flag leaf emerged. In terms of dosage, 2 mg of TFMSA rendered a BTx623 male sterile if applied 2–6 d prior to flag leaf emergence. However, 30 mg of TFMSA applied as much as 34 d before the flag leaf emerged also induced complete sterility of the panicle. There may be a genotypic effect as less TFMSA was necessary to induce complete male sterility in BTx623 than in BTxArg-1. No phytotoxic effects or reductions in female fertility were observed in dosages of TFMSA up to 40 mg. Germination of hybrid seed made on treated plants was equal to that of the parents and the hybrid seedlings were phenotypically normal. The results indicate that male sterility can be induced effectively in sorghum using TFMSA at appropriate dosages and application timings.

Fungicide and Cultivar Management of Leaf Spot Diseases of Winter Wheat in Western Canada.

A complex of leaf-spotting diseases-tan spot, the Septoria complex, spot blotch, and powdery mildew-are frequently observed on winter wheat in western Canada; however, there are few studies indicating varietal differences in reaction to these diseases or the benefit of fungicide application. To determine the benefit of varietal improvement and multiple fungicide treatments and application timings, field experiments were conducted at six site-years in western Canada. Two cultivars varying in reaction to leaf spot diseases were used in combination with fungicide treatments. Disease severity ranged from trace to 64% of the combined flag and penultimate leaf area diseased, differed between cultivars, and was reduced from the check by some fungicide treatments. Yield improvement by fungicide treatment varied from 3.3 to 13.2% greater than the nontreated check. At two site-years, the split application of two half rates of fungicide resulted in the greatest yield; however, in both cases, the yield benefit did not differ from a single application at the flag leaf growth stage. Cultivar selection and fungicide use under environments conducive to disease are beneficial components of an integrated leaf spot disease management program for winter wheat in western Canada.

The Effect of Foliar Application with Iron and Zinc on the Growth Characteristics of Sorghum Bicolor (L) Moench

A field has been carried out at the experimental station, college of Agriculture, in Abu-Ghralb, University of Baghdad, Iraq, during spring and autumn seasons 2014. The main objective is to find out the effects of iron concentration (0,60,90,120)mg.L-1, znic concentration (0,30,60,90) mg.L-1 and two stages of foliar application (flag leaf emergence and 50% flowering stage on some growth traits of Sorghum cv.Bohooth. 70.Layout of the experiment is R.C.B.D arranged in split-split plots designed with three replications, foliar application stages are assigned as main plots, iron as sub-plots, while zinc concentrations as a sub-sub plots. The results show, there is insignificant effects of foliar application stages on all growth traits. Also, the results show that the addition of iron at a con more than 60 mg.l-1 height, leaf area, percentage of chlorophyll in the leaf and percentage of iron and zinc in leaf. The Highest mean of plant height and leaf area 256 and 267cm is obtained when plants are sprayed with 90 and 120 mg.l-1 in spring and autumn seasons respectively. The Highest mean of 90 mg.l-1. leaf area(6709 and 6788)cm2is obtain when plants sprayed with 120mg.l-1. In addition the percentage of chlorophyll in the leaf and dry matter significantly influenced by iron con with 90mg.L-1 it is 40.6mmg.mg-1 chlorophyll in leaf and 14.465 t.ha-1 dry matter in spring season, while the percentage of chlorophyll and dry matter are 60.5 mmg.mg-1 and 14.429 t.L-1 dry matter in autumn season and are obtained by spraying plants with 120 mg.L-1 iron. Highest mean of iron in leaves in spring and autumn (75and 106) mg. kg leaf weight are obtained when plants sprayed with 120 mg.L-1 in spring and autumn seasons. Foliar application at time of flag leaf emergence give the highest plant height and leaf area, while foliar application at time of 50% flowering give the highest percentage of chlorophyll in leaf. There is no significant effect of time of foliar application on the percentage of chlorophyll, leaf area in autumn season, dry matter and percentage of iron and zinc in the leaf .Also, there is a significant effect of zinc concentration on plant height and leaf area,90 mg.L-1 Zn gives highest mean of high plant and leaf area (254 , 265 cm and 13.65, 13.662 t.h-1) in spring and autumn respectively. The result shows that zinc concentration 60 mg.L-1 give the highest mean of chlorophyll in the leaf in spring season, while 90 mg.L-1 of zinc give the highest mean of chlorophyll in the leaf autumn spring and autumn seasons. The highest mean of plant height and leaf area in spring season and percentage of chlorophyll in spring season is significantly influenced by zinc con in foliar application at time of flag leaf emergence, however, there are no significant effect of the time of foliar application of zinc on dry matter, percentage of iron and zinc in the leaves In terms of interaction between zinc and iron, there is a significant effect between 90 mg.L-1 iron in 90 mg.L-1 zinc and its give the highest mean of plan highest, leaf area and dray matter..

Evaluating the Profitability of Foliar Fungicide Programs in Mid-Atlantic Soft-Red Winter Wheat Production.

In mid-Atlantic soft-red winter wheat (SRWW) production, the standard timing for a fungicide application is between flag leaf emergence (Feekes growth stage [FGS] 8) and heading (FGS 10.5). However, two-pass and anthesis (FGS 10.5.1) applications are becoming common, although these programs have not been thoroughly evaluated for disease control, yield, and profitability. Experiments were conducted in the mid-Atlantic in 2015 and 2016 to evaluate fungicide programs with applications at FGS 8, FGS 10.5.1, and two-pass programs with an early application at green-up (FGS 5) followed by (FB) applications at either FGS 8 or FGS 10.5.1. Fungicide programs that included an application at FGS 10.5.1 resulted in the highest probability of no disease on the flag leaf (0.29 to 0.40). The estimated mean yield increases ( ) relative to the nontreated check ranged from 253.65 to 634.16 kg ha-1. Using a grain price of $0.18 kg-1 ($5 bushel-1), probabilities were similar between applications at FGS 8 (0.49 to 0.56) and FGS 10.5.1 (0.53). The probability of profitability ranged from 0.48 to 0.57 for FGS 5 FB FGS 8 applications and 0.52 to 0.59 for FGS 5 FB FGS 10.5.1 applications, indicating limited benefit to two-pass programs.

Suppression of scald and improvements in grain yield and quality of barley in response to fungicides and host-plant resistance

Scald, caused by Rhyncosporium commune, is a common foliar disease of barley in south eastern Australia, causing significant damage during cool, wet seasonal conditions. In this study, scald caused up to 30% (1.4 t/ha) grain yield loss, reduced grain plumpness and weight by up to 25% and 20% respectively and increased screenings by up to 6%. Seed, fertiliser and foliar applied fungicides reduced scald severity and provided improvements in both grain yield and quality. Dual foliar fungicide application of propiconazole at early stem elongation (Z31) and flag leaf emergence (Z39) was most effective in controlling scald and reducing grain yield and quality losses. The seed applied fungicide, fluxapyroxad was the most effective single application fungicide treatment. Varieties with host-plant resistance had less grain yield and quality loss than the very susceptible rated variety, however, these varied between seasons. This study demonstrated that an integrated disease management strategy is required for scald in barley that includes growing resistant varieties and timely fungicide applications.

Effects of Row Spacing and Nitrogen Rate on Wheat Grain Yield and Profitability as Influenced by Diseases.

In Ohio, changes in nitrogen (N) fertilizer application rates and row spacing in combination with fungicide applications have been proposed as possible strategies for increasing wheat productivity and profitability. Field experiments were conducted in 2013, 2014, and 2015 to evaluate the benefits of increasing row spacing and N rates in soft red winter wheat as influenced by diseases. Combinations of narrow (19 cm) and wide (38 cm) row spacings, N rates ranging from 34 to 180 kg ha-1, and the fungicide prothioconazole + tebuconazole applied at flag leaf emergence, boot, or early anthesis represented different management programs. Linear mixed model analyses were performed to evaluate the effects of N, row spacing, and fungicide timing on leaf rust, Fusarium head blight (FHB), and deoxynivalenol (DON), and to quantify relationships among leaf rust, N, grain yield (YLD), and test weight (TW). YLD, TW, grain prices and price discounts, as well as input costs were used to estimate net cash income (NCI) for each management program. Wide row wheat had statistically higher mean FHB and DON, and lower mean yield and test weight than narrow row wheat in 2014 and 2015 but not in 2013. There were significant positive linear relationships between leaf rust and N as well as YLD and TW with N. Differences in FHB and DON among N rates were not statistically significant. Leaf rust severity was consistently lower in treated plots, with efficacy influenced by N rate and application timing. Programs with narrow row spacing and treated with the fungicide generally resulted in the highest mean YLD and TW across N rates. Price discounts due to high FDK and DON, and low TW were higher, and consequently, NCIs were lower in 2014 and 2015 than in 2013. The highest NCIs were obtained for programs with the highest YLD and lowest price discounts, consequently programs with wide row spacing, a fungicide treatment, and high N rates were only economically beneficial when FHB levels were low and grain prices were high.

Evaluation of foliar fungicide programs in mid-Atlantic winter wheat production systems

Foliar fungicides are commonly used to manage foliar fungal diseases of soft-red winter wheat (SRWW) grown in the mid-Atlantic region, but data on the overall performance and utility of various products and application timings on yield and quality is lacking. Eight replicated experiments were conducted in Delaware and Maryland in 2015 and 2016 to evaluate the effects of 13 fungicide programs, consisting of five commercially-available fungicides applied at flag leaf emergence ([Zadoks growth stage (ZGS) 37], anthesis (ZGS 60), or in two-pass programs with the first application at green-up (ZGS 30) followed by applications at either ZGS 37 or ZGS 60, for utility on naturally occurring foliar diseases on the flag leaf and head, yield, and test weight compared to an untreated check. All fungicide programs reduced disease severity on the flag leaf and resulted in higher test weight and yield compared to the untreated check. Foliar disease on the flag leaf and glume blotch were best managed with ZGS 60 applications. Two-pass programs (ZGS 30 + ZGS 37 or ZGS 30 + ZGS 60) did not result in significantly lower disease severity compared to single applications at ZGS 37 or ZGS 60. Yield was highest within the ZGS 30 + ZGS 60 timing, and while significant, increases were small, ranging from 111 to 198 kg ha−1. Within a given application timing, Priaxor® (ZGS 37), Quilt Xcel® (ZGS 30 + ZGS 37), and Quilt Xcel® (ZGS 30) + Prosaro® (ZGS 60) provided the greatest yields. This information will help guide Integrated Disease Management (IDM) systems in the mid-Atlantic region and assist growers in avoiding unnecessary fungicide applications in SRWW.

Effects of free air carbon dioxide enrichment (FACE) on nitrogen assimilation and growth of winter wheat under nitrate and ammonium fertilization.

A 2-year Free Air CO2 Enrichment (FACE) experiment was conducted with winter wheat. It was investigated whether elevated atmospheric CO2 concentration (e[CO2 ]) inhibit nitrate assimilation and whether better growth and nitrogen acquisition under e[CO2 ] can be achieved with an ammonium-based fertilization as it was observed in hydroponic culture with wheat. Under e[CO2 ] a decrease in nitrate assimilation has been discussed as the cause for observed declines in protein concentration in C3 cereals. Wheat was grown under ambient [CO2 ] and e[CO2 ] (600ppm) with three levels (deficiency, optimal, and excessive) of nitrate-based fertilization (calcium ammonium nitrate; CAN) or with optimal ammonium-based fertilization. Ammonium fertilization was applied via injection of an ammonium solution into the soil in the 1st year and by surface application of urea combined with nitrification inhibitors (UNI) in the 2nd year. Results showed that ammonium-based fertilization was successfully achieved in the 2nd year with respect to nitrification control, as soil ammonium concentration was considerably higher over the growing season for UNI fertilized plots compared to optimal CAN plots. Also, stem nitrate concentration, flag leaf nitrate reductase activity, and transcript levels were lower in UNI fertilized plants compared to optimal CAN. Regarding the e[CO2 ] effect on nitrate reductase activity and transcript levels, no alteration could be observed for any nitrogen fertilizer treatment. Flag leaf growth was stimulated under e[CO2 ] leading to an enhanced nitrate reductase activity referred to m2 ground area at late flowering being in line with a higher nitrogen acquisition under e[CO2 ]. Moreover, nitrogen acquisition was considerably higher in nitrate fertilized plants compared to ammonium fertilized plants under e[CO2 ]. Our results obtained under field conditions show that a change from nitrate- to ammonium-based fertilization will not lead to a better growth and nitrogen acquisition of winter wheat under future e[CO2 ].

A Model for Predicting Onset of Stagonospora nodorum Blotch in Winter Wheat Based on Preplanting and Weather Factors.

Stagonospora nodorum blotch (SNB) caused by Parastagonospora nodorum is a serious disease of wheat worldwide. In the United States, the disease is prevalent on winter wheat in many eastern states, and its management relies mainly on fungicide application after flag leaf emergence. Although SNB can occur prior to flag leaf emergence, the relationship between the time of disease onset and yield has not been determined. Such a relationship is useful in identifying a threshold to facilitate prediction of disease onset in the field. Disease occurred in 390 of 435 disease cases that were recorded across 11 counties in North Carolina from 2012 to 2014. Using cases with disease occurrence, the effect of disease onset on yield was analyzed to identify a disease onset threshold that related time of disease onset to yield. Regression analysis showed that disease onset explained 32% of the variation in yield (P < 0.0001) and from this relationship, day of year (DOY) 102 was identified as the disease onset threshold. Below-average yield occurred in 87% of the disease cases when disease onset occurred before DOY 102 but in only 28% of those cases when onset occurred on or after DOY 102. Subsequently, binary logistic regression models were developed to predict the occurrence and onset of SNB using preplanting factors and cumulative daily infection values (cDIV) starting 1 to 3 weeks prior to DOY 102. Logistic regression showed that previous crop, latitude, and cDIV accumulated 2 weeks prior to DOY 102 (cDIV.2) were significant (P < 0.0001) predictors of disease occurrence, and wheat residue, latitude, longitude, and cDIV.2 were significant (P < 0.0001) predictors of disease onset. The disease onset model had a correct classification rate of 0.94 and specificity and sensitivity rates >0.90. Performance of the disease onset model based on the area under the receiver operating characteristic curve (AUC), κ, and the true skill statistic (TSS) was excellent, with prediction accuracy values >0.88. Similarly, internal validation of the disease onset model based on AUC, κ, and TSS indicated good performance, with accuracy values >0.88. This disease onset prediction model could serve as a useful decision support tool to guide fungicide applications to manage SNB in wheat.