Growth Stages Of Barley Research Articles

A new multispectral index for canopy nitrogen concentration applicable across growth stages in ryegrass and barley

Accurately monitoring Canopy Nitrogen Concentration (CNC) is a prerequisite for precision nitrogen (N) fertiliser management at the farm scale with carbon and N budgeting across the landscape and ecosystems. While many spectral indices have been proposed for CNC monitoring, their applicability and accuracy are often adversely affected by confounding factors such as aboveground biomass (AGB), crop type, growth stages, and environmental conditions, limiting their broader application and adoption; with AGB being one of the most dominant signals and confounding factors at canopy scale. The confounding effect can become more challenging as AGB is also physiologically linked with CNC across the growth stages. Additionally, the interplay between index form, selection of optimal wavebands and their bandwidths remains poorly understood for CNC index design. This study proposes robust and cost-effective 2- and 4-waveband multispectral (MS) CNC indices applicable across a wide range of crop conditions. We collected 449 canopy reflectance spectra (400–980 nm) together with corresponding CNC and AGB measurements across four growth stages of ryegrass (winter and summer), and five growth stages of barley (winter-spring) in Victoria, Australia, in 2018 and 2019. All possible waveband (400–980 nm) combinations revealed that the best combination varied between seasons and crop types. However, the visible spectrum, particularly the blue region, presented high and consistent performance. Bandwidths of 10–40 nm outperformed either very narrow (2 nm) or very broad bandwidths (80 nm). The newly developed 2-waveband index (416 and 442 nm with 10-nm bandwidth; R2 = 0.75 and NRMSE = 0.2) and 4-waveband index (512, 440, 414 and 588 nm with 40-nm bandwidth; R2 = 0.81 and NRMSE = 0.17) exhibited the best performance, while validation with an independent dataset (from a different growing period to those used in the model development) obtained NRMSE values of 0.25 and 0.24, respectively. The 4-waveband index provides enhanced performance and permits use of broader bandwidths than its 2-waveband counterpart.

Barcoding of white-spotted stink bug, Eysarcoris ventralis (Westwood) (Hemiptera: Pentatomidae) attacking Egyptian barley and its population density

White-spotted stink bugs, were noticed as a first time in a few numbers of the Egyptian barley cultivar Giza 138 plants in mid of January of 2019/2020 season at soil improvement and conservation Research department at Sakha Agricultural Research station, farm, Kafr El-Sheikh Government, Egypt. Morphological identification and DNA barcoding of mitochondrial gene cytochrome c oxidase subunit I (COI) were used identified the species of collected bugs. The results revealed a new record of Eysarcoris ventralis (Westwood 1837) (Hemiptera: Heteroptera: Pentatomidae). The results of pest insect survey of directly accounts on barley cultivar weekly during two growing winter 2019/2020 and 2019/2021 seasons displayed a significant effect of seasons on the E. ventralis population density. Positive significantly correlation was found between the E. ventralis population density and growth stages of barley under 2019/2020 and 2019/2021 seasons by (0.311 and 0.531) respectively. Regression coefficient, revealed that decrease of temperature by 1 °C increased population of E. ventralis by 0.051 and 0.036 insects per 10 tillers in 2019/2020 and 2019/2021 seasons respectively, while increase of relative humidity by 1% decreased population of E. ventralis by 0.047 and 0.31 insects per 10 tillers in 2019/2020 and 2019/2021 seasons. High population of E. ventralis was found in Anthesis stage of barley. Minor damage was found in immature grain at dough stage. Thus these results are so important to using feature integrated pest management (IPM) programs in barley to avoid the damage of Eysarcoris ventralis (Westwood 1837). Partial DNA sequence of collected sample using cytochrome c oxidase I (COI) mitochondrial gene with clear alignment of 576 bp. The tested sequence more related to Eysarcoris sp. and far from Nezara sp.). For more accuracy, BLAST was used for tested sequence with Eysarcoris sp. and found it closely related to E. ventralis. DNA sequence of COI as type effectively precludes the finding of a new evidence to resolve taxonomic problems.

QTL analysis of Chlorophyll Content at different growth stages of Barley

QTL analysis of Chlorophyll Content at different growth stages of Barley

A new phenology-based method for mapping wheat and barley using time-series of Sentinel-2 images

In recent years, various techniques have been developed to generate crop-type maps based on remote sensing data. Wheat and barley are two major cereal crops cultivated as the first and fourth largest grain crops across the globe. The variations in spectral temporal profile of both crops are generally insignificant at small scales and therefore the two crops are phenologically fairly clearly separated; however, at large scale areas the variance of phenological parameters increases for both crops due to the effects of various climatic and orographic factors which adversely influences discrimination of wheat and barley. Additionally, wheat and barley are usually cultivated as both spring and winter or early and late season crops in some areas, making it more difficult to distinguish them. Therefore, developing a new method based on remote sensing data for effective discrimination of wheat and barley is an important necessity in the field of precision agriculture. To this end, this research presents a new phenology-based method to discriminate barley from wheat. In this study, Sentinel-2 (S2) time-series data of a study site in Iran (Markazi) and two sites in the USA (Idaho and North California), are employed. Spectral reflectance values of wheat and barley are examined during the growing season and a new spectral-temporal feature is successfully developed for automatic identification of the barley heading date. The Relief-f algorithm is then employed to select appropriate spectral features of S2 to distinguish wheat from barley at the heading date. Finally, generated spectral features at the heading date are used as input to Support Vector Machine (SVM) and Random Forest (RF) to produce barley and wheat maps. The Kappa coefficient and overall accuracy (OA) obtained for the three study sites are more than 0.67 and 76%, respectively. The findings of this study demonstrate the potential of remote sensing data to identify the phenological growth stages of barley and distinguish it successfully from wheat.

Different G6PDH isoforms show specific roles in acclimation to cold stress at various growth stages of barley (Hordeum vulgare) and Arabidopsis thaliana

Low temperatures (0–10 °C) represent a major physiological stress for plants, negatively affecting both their growth rates and overall growth. Cold stress may induce a wide range of negative physiological effects, from oxidative stress to photosynthetic damage. We investigated the effects of low temperatures in two different model plants, Arabidopsis thaliana and Hordeum vulgare. We tested whether the oxidative pentose phosphate pathway (OPPP) is involved in the increase of reductants’ levels needed to counteract oxidative stress induced by cold. The expression, occurrence, and activity of different glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) isoforms during cold stress and plant recovery from low temperatures, were measured at different growth stages from early germinated to mature pot-grown plants. Our results showed plants exhibited changes in different stress markers; ascorbate peroxidase – APX, catalase - CAT, proline, malondialdehyde, H2O2, NADPH/NADP+. We found that a major role in cold acclimation for cytosolic- and peroxisome-located G6PDHs, and different roles for plastidial/chloroplastic isoforms. This suggests that G6PDH isoforms may regulate redox homeostasis in low temperatures, in order to support the increased and continued demand of reductants during both cold stress and recovery stages. Furthermore, we found a significant involvement of (6PGDH), strengthening the idea that the contribution of the whole oxidative pentose phosphate pathway (OPPP) is required to sustain reductant supply under cold stress.

Impact of Bulk ZnO, ZnO Nanoparticles and Dissolved Zn on Early Growth Stages of Barley-A Pot Experiment.

Zinc is among the most in-demand metals in the world which also means that a considerable amount of this element is released to the environment each year as a result of human activities. A pot experiment was conducted to study the impact of low- and high-dose zinc amendments on plant growth and biomass yield, with Calcic Chernozem as a growing medium and barley (Hordeum vulgare L.) as a model plant. The distribution of zinc in various plant parts was also investigated. Zn (II) was added in powder as bulk ZnO and in solution as ZnO nanoparticles and ZnSO4 in two dosages (3 and 30 mmol kg−1 soil) prior to planting. The plants were harvested after 10 days of growth. The three sets of data were taken under identical experimental conditions. The application of zinc in aqueous solution and in particulate form (having particle sizes in the range of <100 nm to >500 nm) at concentration of 3 and 30 mmol Zn kg−1 to the soil resulted in decreased growth (root length, shoot length) and biomass yield; the only exception was the addition of 30 mmol Zn kg−1 in the form of bulk ZnO, which had a positive effect on the root growth. The dry weight reduction (sprout biomass) was lowest in plants grown in soil treated with dissolved zinc. There were no statistically significant changes in the content of chlorophyll a, chlorophyll b, and total chlorophyll, although flame atomic absorption spectrometry (FAAS) analysis indicated that plants bioaccumulated the zinc applied. This implies that the transport of zinc into the above-ground plant parts is controlled by the presence of effective mechanical and physiological barriers in roots. Crop performance under zinc stress in relation to biomass production and the growth of roots and shoots is also partly a reflection of the effects of soil properties. Our findings emphasize the importance of considering plant-soil interactions in research of potential toxicity and bioavailability of zinc in the environment.

Canopy Indices: a Model to Estimate the Nitrogen Rate for Barley and Wheat

The objectives were to calibrate the Soil Plant Analysis Development (SPAD) and Green Seeker (GS) as tools to determine the differential of the economic optimum nitrogen rate (dEONR) at different growth stages of barley and to evaluate if a single SPAD or GS calibration model can be used for two cereal crops: barley and spring wheat. Fourteen field experiments were conducted (2016–2018) evaluating five N rates. Relative canopy indices were determined using a SPAD-502 (rSPAD) and a GS sensor (rNDVI) at Z24, Z31, and Z39 growth stages. The relationship between sensor indices and dEONR was evaluated by fitting quadratic-plateau (QP) regression models. Data from a previous study was used to evaluate if a unique QP model could predict dEONR from canopy indices for barley and wheat. Statistically significant QP models were determined for rSPAD and rNDVI at all evaluated growth stages. The sensitivity of these models was greater for rSPAD (0.0006 on average) than for rNDVI (0.0004 on average). A single QP model was developed to predict dEONR from rSPAD at Z31 and Z39 barley growth stages (R2 = 0.68). Also, a unique model was developed to predict dEONR from rSPAD at Z31 and Z39, but not only for barley but also for wheat (R2 = 0.64). A single model could be used to determine variable in-season N rates for barley and wheat, increasing the N use efficiency and limiting possible negative economic and environmental impacts of fertilization over the agroecosystems.

Crop growth stage estimation prior to canopy closure using deep learning algorithms

Growth stage determination plays an important role in yield prediction and cereal husbandry decision-making. Conventionally, crop growth stage determination is performed manually by means of visual inspection. This paper investigates wheat and barley growth stage estimation by classification of proximal images using convolutional neural networks (ConvNets). A dataset consisting of 138,000 images captured prior to the crop canopy closure stage was acquired from 4 sites (7 different fields) in Ireland. The dataset includes images of 12 growth stages of wheat and 11 growth stages of barley captured for a number of crop varieties, seed rates and brightness levels. A camera was held at 2 m from the ground and two camera poses were used—downward-looking and declined to $$45^\circ$$ below the horizon. Classification was carried out using three different machine learning approaches: (1) a 5-layer ConvNet model, including three convolutional layers, which was trained from scratch on our crop dataset; (2) transfer learning based on a VGG19 network pre-trained on ImageNet with an additional four fully connected layers, and (3) a support vector machine with conventional feature extraction. The classification accuracies of the aforementioned models were found to be (1) 91.1–94.2% for the ConvNet model, (2) 99.7–100% for the transfer learning model and (3) 63.6–65.1% for the SVM. For both crops, the best accuracy was obtained using the $$45^\circ$$ camera pose and the transfer learning ConvNet model. For the growth stage classification task, the transfer learning ConvNet has the advantage of significantly reduced training time when compared with the built-from-scratch ConvNet model.

Crop water stress maps for an entire growing season from visible and thermal UAV imagery

Abstract. This study investigates whether a water deficit index (WDI) based on imagery from unmanned aerial vehicles (UAVs) can provide accurate crop water stress maps at different growth stages of barley and in differing weather situations. Data from both the early and late growing season are included to investigate whether the WDI has the unique potential to be applicable both when the land surface is partly composed of bare soil and when crops on the land surface are senescing. The WDI differs from the more commonly applied crop water stress index (CWSI) in that it uses both a spectral vegetation index (VI), to determine the degree of surface greenness, and the composite land surface temperature (LST) (not solely canopy temperature).Lightweight thermal and RGB (red–green–blue) cameras were mounted on a UAV on three occasions during the growing season 2014, and provided composite LST and color images, respectively. From the LST, maps of surface-air temperature differences were computed. From the color images, the normalized green–red difference index (NGRDI), constituting the indicator of surface greenness, was computed. Advantages of the WDI as an irrigation map, as compared with simpler maps of the surface-air temperature difference, are discussed, and the suitability of the NGRDI is assessed. Final WDI maps had a spatial resolution of 0.25 m.It was found that the UAV-based WDI is in agreement with measured stress values from an eddy covariance system. Further, the WDI is especially valuable in the late growing season because at this stage the remote sensing data represent crop water availability to a greater extent than they do in the early growing season, and because the WDI accounts for areas of ripe crops that no longer have the same need for irrigation. WDI maps can potentially serve as water stress maps, showing the farmer where irrigation is needed to ensure healthy growing plants, during entire growing season.

Spring barley stand structure as an indicator of lodging risk

Field experiments were performed in Kroměřiž, Czech Republic in 2012–2014 and evaluated for spring barley comprising treatments which different sowing rates and nitrogen fertilization rates. The objective of this study was to determine parameters of stand structure in early (BBCH 39) growth stages of barley that would enable evaluation of lodging risk. Lodging was significantly affected by both year and nitrogen fertilization rate. Increased nitrogen fertilization rates demonstrably increased lodging. Higher fertilization rates manifested in increased tiller biomass weight, greater plant height, and smaller roots. Similarly, the protein content of harvested grain was strongly affected by year and nitrogen application rate. Higher fertilization rates also resulted in grain with higher protein content. Sowing density did not affect either lodging level or protein content. Yields were affected only by year. Increased tiller biomass weight and increased plant height during early growth stages are significant indicators of lodging risk. Correlation between lodging and tiller biomass and plant height was higher than 0.5 and statistically significant ( P = 0.000).

Effect of wastewater and grey water reuse on the germination and early growth of barley and onions

&lt;p&gt;This paper evaluates the effect of wastewater reuse on the germination and growth at early stages of barley and onions. Treated wastewater, partially treated industrial wastewater, grey water, and car wash water, in addition to tap water as control were used to test their effect on germination percentage and speed of barley and onions and on the early growth stages of barley. Results have shown that germination percentage and germination velocity of onions and barley were significantly reduced when treated wastewater and car wash water were used. All water qualities produced higher shoot lengths and lower root lengths of barley compared to tap water, with car wash water producing the highest shoot to root length ratio followed by treated wastewater. The shoot dry weight to root dry weight of barley of all irrigation water types used were not significantly different. The effect of wastewater reuse on germination and early growth of barley and onion has not been studied. The recommendation that resulted from this research is that these types of wastewaters should be avoided during the early growth phases of barley and onions.&lt;/p&gt;

The effect of companion crops management on biological weed control in the seeding year of lucerne

A 3-year experiment was conducted at the Research Station Pawłowice of the Wrocław University of Environmental and Life Sciences, Poland, to evaluate the effect of companion crops and their management on lucerne weediness and productivity. Weed density, weed structure and companion crop yield in the seeding year were evaluated. The experiment had two factors; the main factor was three harvest dates of the companion crops. The harvest date was assessed based on the barley growth stages. A subplot factor was a companion crop in which lucerne was sown: spring vetch (V), spring barley (B), mixture of spring vetch and spring barley (20%+80%, M-1) and mixture of spring vetch and spring barley (50%+50%, M-2). Lucerne without a companion crop was included as a control (L). At the companion crops harvest, spring vetch and spring barley sown alone or in mixtures significantly decreased weed density, compared with L by 53%, 70%, 78% and 83% for the companion crop V, M-2, B and M-1, respectively. Annual weed dry matter biomass ranged from 0.37 t ha− 1 in M-1 to 2.06 t ha− 1 in L. Purple deadnettle (Lamium purpureum) and lambsquarters (Chenopodium album) were the dominant weed species in the first two weed counts.

A hypothesis on physiological alterations during plant ontogenesis governing susceptibility of winter barley to ramularia leaf spot

The occurrence and epidemic spread of ramularia leaf spot (RLS) caused by Ramularia collo‐cygni was studied with relation to the plant age‐dependent alterations in the antioxidative defence systems in the leaves during mature stages of field‐grown winter barley. The breakdown of enzymatic activities of dehydroascorbate reductase, monodehydroascorbate reductase and glutathione reductase in the two uppermost fully expanded leaf layers correlated well with a decrease in the pool of the non‐enzymatic antioxidants ascorbate and glutathione. The general decline in the antioxidative systems occurred between 31 May and 8 June after ear emergence stages and preceded the first visible symptoms of RLS. The activities of peroxidases corresponded to an increase in phenolics and lignification which seemed to enhance the infectivity of the fungus rather than to protect the plant. The first R. collo‐cygni conidia were trapped in the field about 4 weeks before the latent infection was first detected by ELISA, and 5 weeks before the first disease symptoms became visible. Both the counts of airborne conidia and the weather data recorded between April and June suggest that neither inoculum nor the weather conditions are limiting factors for infection by R. collo‐cygni at earlier growth stages of barley. It is concluded that the relatively late development of RLS in the field in mid June is governed by the significant degradation of the antioxidative protection systems in the leaves of barley at the onset of ripening stages, rather than by environmental factors or the availability of airborne inoculum.

N release from livestock waste compost pellets in barley fields

N release patterns from dairy cattle, swine, and poultry waste compost pellets were studied using the buried glass filter paper method in barley fields. Field experiments with barley were also carried out to study the relationship between N release from pellets and N absorption by barley. Results showed that about 28, 36, 44% and of N were released from 3 types of compost pellets throughout the growth stages of barley, respectively. However, since more than 60% of N was released before the tillering stage of barley, barley absorbed a large amount of N and grew excessively in winter. When poultry and swine waste compost pellets were incorporated into dairy cattle waste compost at the N ratio of 1 : 1 or 2 : 1, N release rate from the incorporated pellets decreased, but N was still mainly released at early stage after application. Compost pellets made of dairy cattle and swine waste compost at the N ratio of 1 : 1 led to the highest production of barley in this experiment, followed by compost pellets made of dairy cattle and poultry waste compost at the N ratio of 1 : 1 and poultry waste compost pellets. The use of these three types of pellets resulted in a barely yield higher than that obtained with chemical fertilizers at the significant level of 1%. Amounts of P and K absorbed by barley in the pellet treatments exceeded those in the chemical fertilizer treatments, suggesting that additional application of chemical fertilizer containing phosphorus and potassium was not necessary when animal waste compost was used for barley production as basal fertilizer. Meanwhile, the balance of nutrients, such as N, P, and K, in the compost pellets should be considered also to achieve comprehensive management of nutrients for crop production.

Efficacy of Imidacloprid for Control of Cereal Leaf Beetle (Coleoptera: Chrysomelidae) in Barley

The toxicity of imidacloprid to the cereal leaf beetle, Oulema melanopus (L.), was measured under laboratory and field conditions. Insect mortality and plant damage were determined from artificial and natural infestations of O. melanopus applied to various growth stages of barley. All rates of imidacloprid formulated and applied as a seed treatment caused >90% mortality to cereal leaf beetle larvae when barley was infested with eggs at the 4-leaf stage, but were ineffective when barley was infested with eggs at the early tillering or flag-leaf stages of barley. This window of susceptibility influenced results obtained in field trials where peak larval emergence did not occur until the early tillering stage of barley. The resulting mortality in plants from treated seeds never exceeded 40% in the field. Foliar imidacloprid, however, caused >90% mortality in the field, and may be another option in the management of the cereal leaf beetle.

A field study of nitrogen dynamics and spring barley growth as affected by the quality of incorporated residues from white clover and ryegrass

Four different grass swards were grown on a sandy loam for 3 years, and then incorporated into the soil through rotovation in the spring. The treatments differed in the proportion of white clover ( Trifolium repens) and ryegrass (Lolium perenne), both through seeding in pure stand or mixture and through N fertilization (0 or 150 kg N ha 1 yr 1 ) for the white clover-ryegrass mixtures. A control treatment (fallow), differing from the others in that the grass sward had been incorporated one year earlier, was also included. A spring barley (Hordeum vulgarecv. texane) crop was established in half of the experimental site and the other half was left unplanted. Carbon and nitrogen mineralization from the residues was measured as soil surface CO2 flux and soil inorganic N accumulation in unplanted plots under non-leaching conditions. Residue decomposition processes, barley dry matter production and N uptake showed clear differences between the five treatments, due especially to the differences in amount of residue N incorporated. Incorporated residue N was highest in the white clover in pure stand (C150), and lowest in the ryegrass in pure stand (G150) treatments, with non-fertilized and fertilized white clover-ryegrass residues (CG0 and CG150, respectively) intermediate and similar in both amount and quality of the residues. However, in spite of this similarity the treatments differed greatly with respect to both C and N mineralization, indicating that other factors than the measured quality parameters (i.e. C, N, C-to-N ratio, water solubles, cellulose, lignin) influenced their decomposition pattern. The highest crop dry matter production and N uptake was measured in the C150 treatment, followed by the CG0 and the fallow treatment, with considerable lower yields in the CG150 and G150 treatments. There was a significantly higher inorganic N content, 60 kg N ha 1 , in the planted C150 and CG0 treatments during the seedling and tillering barley growth stages, with no significant difference between treatments during the later barley growth stages. Apparent net N mineralization measured in the unplanted CG0 treatment exceeded that of the C150, whereas the other treatments ranked similar to the barley N uptake rates. This indicated that availability of soil inorganic N at the early tillering stage was a key determining factor for the final barley dry matter yield and N uptake, with later N mineralization rates having lesser influence.

THE SPATIAL DISTRIBUTION OF LIMOTHRIPS DENTICORNIS HALIDAY (THYSANOPTERA: THRIPIDAE) EGGS ON SPRING BARLEY

AbstractThe within-plant spatial distribution of Limothrips denticornis Haliday eggs on spring barley (Hordeum vulgare L.) in North Dakota was examined during the growing seasons of 1987 and 1988. In both years, most eggs were found during inflorescence emergence (growth stages 10–10.5 on the Feekes scale), although eggs were detected both prior to and after these growth stages. Once inflorescence emergence was initiated, over 8.5% of the eggs were found in the top two leaf sheaths, with the majority in the flag leaf sheath. Over all barley growth stages, significantly more eggs (P≤0.05) were found in the middle third than in either the top or bottom third of the flag leaf sheath. No difference (P≥0.05) in the within-sheath location of eggs on lower leaves was detected.

Effect of Inoculations with Cochliobolus sativus at Specific Growth Stages on Grain Yield and Quality of Malting Barley1

Field experiments were conducted to characterize the relationship between severity of spot blotch epidemics in barley (Hordeum vulgare L.) and loss in grain yield and malt quality. The effect of spot blotch on yield and quality must be known to evaluate the economic benefit of specific disease control strategies such as the use of resistant cultivars or fungicide. Spot blotch epidemics of different intensities were established by inoculating field plots at specific barley growth stages and by using two cultivars, ‘Larker’ and ‘Dickson’, that differ in disease reaction to spot blotch. Inoculations with Cochliobolus sativus reduced yield, yield components, and malt quality of Larker more than Dickson. Yield and quality factors were more adversely affected if inoculation was just prior to flag leaf emergence or at anthesis than at early milk development. Reduction in yield in response to spot blotch epidemics was largely a function of reduction in kernel weight. In 1983, field plots of Larker, Dickson, ‘Glenn’, ‘Bumper’, ‘Robust’, and ‘Hazen’ were either inoculated with C. sativus spores or sprayed with fungicide to evaluate changes in cultivar resistance to spot blotch since the release of Larker in 1961. Based on percentage yield loss [(yield of inoculated plots)/(yield of fungicide‐treated plots)], a significant improvement in disease resistance was achieved with the release of Dickson in 1964. Percentage yield losses observed for Dickson (released in 1964), Glenn (released in 1978), Bumper (released in 1980), and Robust (released in 1983) were not statistically different from each other, indicating no further improvement in disease resistance over Dickson. However, a significant improvement in disease resistance was again achieved with the release of Hazen in 1984.

Drought Sensitivity at Various Growth Stages of Barley in Relation to Relative Evapotranspiration and Water Stress1

AbstractPrevious investigations into the influence of drought on yield of barley (Hordeum distichurn L.) have been related to either the intensity of water stress or the duration of drought periods. Little attention has been given to the combination of intensity and duration of water stress. In this investigation drought sensitivity (F), calculated as relative grain yield reduction (1 — u/U) of barley at various growth stages, was related to the number of stress days (SD). The number of stress days was calculated as the product of relative evapotranspiration deficit (1 — Ea/Er) and the duration of drought periods (days). Barley (‘Zita’), grown in loamy sand (mixed mesic Typic Udipsamment) in lysimeters, was exposed to drought at different development stages. The lysimeters were automatically protected from rain by a mobile glass roof. Each drought treatment consisted of a single period without irrigation. Watering resumed when all available soil water was used. The first drought occurred during jointing and the final one during ripening. Relative evapotranspiration (Ea/Er) was found to be a more sensitive expression for crop water stress than leaf water potential. Relative evapotranspiration began to decrease when two‐thirds of available soil water had been used. The length of drought periods is defined from that time until irrigation was resumed. Drought sensitivity per stress day (F/SD) was decreased from 0.14 during jointing to 0.08 during booting. For drought after heading F/SD was 0.038 corresponding to a 3.8% grain yield reduction per stress day. This means that one stress day corresponds to one day without grain growth.

ECONOMIC THRESHOLDS AND ECONOMIC INJURY LEVELS OF CEREAL APHIDS ON BARLEY IN SOUTHWESTERN QUEBEC

AbstractArtificial infestations of cereal aphids in caged plants were made at different growth stages of barley in the field in 1978 and 1979. Forty, 80, 160, and 200 aphids/tiller reduced grain yield significantly (P &lt; 0.01) when introduced into caged plants at flowering and milky stages for 2 weeks. Only the 150 and 200 aphids/tiller-treatments gave significant reductions in yield when introduction was at the mealy ripe stage. Twenty aphids/tiller gave a significant reduction in yield only when they were introduced at the beginning of ear emergence and flowering, but not at the milky ripe stage. Significant reduction in percentage protein was obtained only when 160 and 200 aphids/tiller were introduced at flowering and milky ripe stages. The economic injury and threshold levels were calculated as 10–18 and 8–16 aphids/tiller, respectively, depending on rate of increase of aphids, costs of chemical control, and the value of the crop in 1978 and 1979.