Small Field Plots Research Articles

Monitoring soil surface roughness under growing winter wheat with low‐altitude UAV sensing: Potential and limitations

AbstractSoil surface roughness (SSR) is an important factor in controlling sediment and runoff generation, influencing directly a wide spectrum of erosion parameters. SSR is highly variable in time and space under natural conditions, and characterizing SSR to improve the parameterization of hydrological and erosion models has proved challenging. Our study uses recent technological and algorithmic developments in capturing and processing close aerial sensing data to evaluate how high‐resolution imagery can assist the temporally and spatially explicit monitoring of SSR. We evaluated the evolution of SSR under natural rainfall and growing vegetation conditions on two arable fields in Denmark. Unmanned aerial vehicle (UAV) photogrammetry was used to monitor small field plots over 7 months after seeding of winter wheat following conventional and reduced tillage treatments. Field campaigns were conducted at least once a month from October until April, resulting in nine time steps of data acquisition. Structure from motion photogrammetry was used to derive high‐resolution point clouds with an average ground sampling distance of 2.7 mm and a mean ground control point accuracy of 1.8 mm. A comprehensive workflow was developed to process the point clouds, including the detection of vegetation and the removal of vegetation‐induced point cloud noise. Rasterized and filtered point clouds were then used to determine SSR geostatistically as the standard deviation of height, applying different kernel sizes and using semivariograms. The results showed an influence of kernel size on roughness, with a value range of 0.2–1 cm of average height deviation during the monitoring period. Semivariograms showed a measurable decrease in sill variance and an increase in range over time. This research demonstrated multiple challenges to measuring SSR with UAV under natural conditions with increasing vegetation cover. The proposed workflow represents a step forward in tackling those challenges and provides a knowledge base for future research. © 2020 John Wiley & Sons, Ltd.

Salinity: Electrical conductivity and total dissolved solids

AbstractThe measurement of soil salinity is a quantification of the total salts present in the liquid portion of the soil. Soil salinity is important in agriculture because salinity reduces crop yields by reducing the osmotic potential, making it more difficult for the plant to extract water, by causing specific‐ion toxicity, by upsetting the nutritional balance of plants, and by affecting the tilth and permeability of a soil. A discussion of the principles, methods, and equipment for measuring soil salinity is presented. The discussion provides a basic knowledge of the background, principles, equipment, and current accepted procedures and methodology for measuring soil salinity in the laboratory using electrical conductivity of aqueous extracts from soil samples and measurement of total dissolved solids in the saturated soil extract. Attention is also given to the use of suction cup extractors, porous matrix or salinity sensors, electrical resistivity, and electromagnetic induction to measure salinity in soil lysimeter columns and small field plots (< 10 by 10 m). Land resource managers, producers, extension specialists, Natural Resource Conservation Service field staff, undergraduate and graduate students, and university, federal, and state researchers are the beneficiaries of the information provided.

Chlorophyll Fluorescence Kinetics May Be Useful to Identify Early Drought and Irrigation Effects on Photosynthetic Apparatus in Field-Grown Wheat

To assess the reliability and sensitivity of non-invasive optical methods to detect the early effects of water deficit in the field, we analyzed the time-series of non-invasive measurements obtained in a dry season in a representative collection of wheat genotypes grown in small-plot field trials, in non-irrigated and irrigated variants. Despite a progressive water deficit and significant yield loss, the measurements indicated very minor changes in chlorophyll content or canopy cover. This corresponded well to the insignificant differences in spectral reflectance normalized difference vegetation index (NDVI) values. On the other hand, we identified the significant and rapid response of fast fluorescence kinetics data following the onset of irrigation. Analysis of parameters showed the main effects of drought were associated with changes in the amplitude of the I–P phase of the OJIP transient, indicating changes at the level of photosystem I and beyond. Statistical analyses identified the integrative parameter performance index PItot as the most sensitive parameter, which well-reflects the differences in responses of the genotypes to water deficit. Our results suggest that focusing on photosynthetic functions detected by the rapid chlorophyll fluorescence records can provide more accurate information on the drought stress level, compared to the structural data obtained by absorbance or reflectance measurements.

Compatibility of Bifenazate andPhytoseiulus persimilisfor Management of Twospotted Spider Mites in North Carolina Staked Tomatoes

The twospotted spider mite (TSSM, Tetranychus urticae Koch) is a key pest of tomatoes (Solanum lycopersicon L. [Solanales: Solanaceae]) in North Carolina, and its management has relied principally on synthetic acaricides. Augmentative biological control of TSSM is a commonplace and effective management strategy in greenhouses worldwide, but in field-grown vegetable crops biocontrol of TSSM is poorly developed. We conducted small-plot field experiments in 2016 and 2019 to test the ability of the predatory mite, Phytoseiulus persimilis Athias-Henriot, to establish, disperse, and reduce TSSM in staked tomatoes, as well as test their compatibility with a commonly used reduced-risk acaricide, bifenazate (Acramite). Across both years, the most effective treatment for reducing TSSM was the combination of P. persimilis + Acramite. Phytoseiulus persimilis successfully established both years, but its population growth and dispersal were greater in 2016 than 2019. Acramite alone significantly reduced TSSM pressure in 2019 and P. persimilis alone did not reduce TSSM pressure below the control in either year. However, results in 2016 were influenced by the eventual dispersal of P. persimilis into all experimental plots, despite efforts to hinder their movement with corn barriers. Results in 2019 were influenced by the late-season invasion of TSSM into the trial, which delayed P. persimilis releases and influenced their establishment and growth. This study is the first to demonstrate the utility and limitations of P. persimilis in staked field tomatoes, which is a promising option for growers to manage TSSM in tomatoes in the southeast United States.

Examination of drought stress of two genotype maize hybrids with different fertilization

In the growing season of 2019, we analysed stress resulting from climatic factors on maize hybrids of different genotypes, with the aim of gaining a better understanding of the physiological responses of each hybrid, which might support the elaboration of a cost-effective irrigation plan.
 Our experiments were carried out at the Látókép Experimental Station of the University of Debrecen on calcareous chernozem soil in a small-plot long-term field trial with strip plot design. In the scope of the experiment, N-fertilizer doses were applied as basic fertilizer and top-dressing in addition to the non-fertilized (control) treatment. The 60 and 120 kg N/ha doses applied as basic fertilizers in the spring were followed by top-dressing in the V6 phenophase with a +30 kg N/ha dose. Measurements were carried out with the involvement of the Renfor early (FAO 320) and Fornad (FAO 420) late maturity hybrids-
 The stomata of the plants became more and more closed with the progression of the phenological phases; their stomatal conductance decreased. However, the hybrids responded differently to environmental stress. In the case of the Renfor hybrid, the highest conductance (669 mmol/m2-s) was recorded in the V12 phenophase with the 150 kg N/ha treatment. The stomata were more open due to the high turgor pressure, allowing plants to evaporate properly. The plant was in its worst physiological condition on 2nd July, at the time of the appearance of the last leaf in the case of the 120 kg N dose (224 mmol/m2-s). The value measured in the V12 phenophase has already shown that the stomata were closing due to the self-regulating system of the plant. It would have been necessary to dispense irrigation water following the measurement. This confirms the finding that water stress can be prevented by measuring stomatal conductance.
 In the case of the Fornad hybrid, stomatal conductance was the highest on 12th June (630 mmol/m2-s) in the 90 kg N/ha treatment and it was the lowest (183 mmol/m2-s) in VT (emergence of the last leaf) phenophase in the 60 kg N/ha treatment. In this case, the appropriate time for applying irrigation water would have been early July, when the conditions for the plants were still adequate. Subsequently, the stomata began to close due to a reduction of the water resources available to them.
 There was a significant correlation between soil moisture and stomatal conductance, as well as between temperature and stomatal conductance.

Correlation analysis of the SPAD readings and yield of sweet potato (Ipomoea batatas L.) under different agrotechnical conditions

We studied the effect of planting method (flat and ridge planting) and row spacing (0.75-1.0 m) on the yield and SPAD readings of sweet potato (Ásotthalmi 12 variety) in a small-plot field experiment in 2017 and 2018. The experiment was set up in lattice design with 4 replications. The SPAD readings of sweet potato were measured four (2017) and three (2018) times during vegetation period (by Konica Minolta 502). A high yield level was reached both in 2017 (23.23-50.69 t ha-1 marketable yield) and 2018 (33.26-47.34 t ha-1) due to the effects of the favourable soil (chernozem), the near-optimal agrotechnical background, irrigation and the warmer-than-average vegetation period. In both years, higher yields were obtained with flat planting and 0.75 m row spacing. The proportion of non-marketable tubers was between 9.97-15.57% in 2017 and 8.65-11.01% in 2018. The SPADmax values were measured in July (39.61-50.31 in 2017) and in August (49.90-55.33 in 2018). Strong correlation observed among SPAD readings, the whole yield and the marketable yield in both years (r = 0.632*, r = -0.664* and r = 0.709**, respectively). Also, a strong correlation was observed between the planting method and the obtained SPAD readings (r = -0.847**, -0.682* in 2017 and r = -0.634*, -0.488 in 2018, respectively), while there was no correlation between row spacing and SPAD readings (r = -0.006NS-0.190NS). Crop year had a strong effect on SPAD readings (r = 0.639**-0.871**).

Effect of Sulphur Foliar Application on Yield and Grain Quality of Selected Malting Barley Varieties

The aim of the experiment was to assess the influence of foliar application of sulphur on grain yield, N-substances and sulphur content in the grain. The content of dimethylsulphide (DMS) and its precursors (PDMS) of malt were determined. The study was performed in the form of a small-plot field trial between the years of 2010 and 2012, at a field trial station in Žabčice (South Moravia). Three malting barley varieties for the production of Czech beer (Aksamit, Bojos and Radegast) and three malting barley varieties for the production of export beer (Prestige, Jersey and Sebastian) were tested in that period. Sulphur (8 kg S per ha) was applied on leaves in the form of a suspension of micronized elementary sulphur with bentonite in stem elongation – first node (BBCH 31) and before end of heading (BBCH 57) of growth stages. Sulphur fertilization in both vegetation phases increased significantly grain yield and the most significant increase was detected after the application in BBCH 57. On the other hand, there was no accumulation of sulphur in the grain nor an increase in N‑substances content. Sulphur fertilization did not increase DMS and PDMS content of malt as well.

Assessment of Multi-Image Unmanned Aerial Vehicle Based High-Throughput Field Phenotyping of Canopy Temperature.

Canopy temperature (CT) has been related to water-use and yield formation in crops. However, constantly (e.g., sun illumination angle, ambient temperature) as well as rapidly (e.g., clouds) changing environmental conditions make it difficult to compare measurements taken even at short time intervals. This poses a great challenge for high-throughput field phenotyping (HTFP). The aim of this study was to i) set up a workflow for unmanned aerial vehicles (UAV) based HTFP of CT, ii) investigate different data processing procedures to combine information from multiple images into orthomosaics, iii) investigate the repeatability of the resulting CT by means of heritability, and iv) investigate the optimal timing for thermography measurements. Additionally, the approach was v) compared with other methods for HTFP of CT. The study was carried out in a winter wheat field trial with 354 genotypes planted in two replications in a temperate climate, where a UAV captured CT in a time series of 24 flights during 6 weeks of the grain-filling phase. Custom-made thermal ground control points enabled accurate georeferencing of the data. The generated thermal orthomosaics had a high spatial accuracy (mean ground sampling distance of 5.03 cm/pixel) and position accuracy [mean root-mean-square deviation (RMSE) = 4.79 cm] over all time points. An analysis on the impact of the measurement geometry revealed a gradient of apparent CT in parallel to the principle plane of the sun and a hotspot around nadir. Averaging information from all available images (and all measurement geometries) for an area of interest provided the best results by means of heritability. Correcting for spatial in-field heterogeneity as well as slight environmental changes during the measurements were performed with the R package SpATS. CT heritability ranged from 0.36 to 0.74. Highest heritability values were found in the early afternoon. Since senescence was found to influence the results, it is recommended to measure CT in wheat after flowering and before the onset of senescence. Overall, low-altitude and high-resolution remote sensing proved suitable to assess the CT of crop genotypes in a large number of small field plots as is required in crop breeding and variety testing experiments.

INTEGRATING IMAGE AT DIFFERENT SPATIAL RESOLUTIONS AND FIELD DATA FOR SEAGRASS PERCENT COVER MAPPING

Abstract. There are not many discussion or previous works that specifically address the issue of integrating small field plot size (1 m2) and image at different spatial resolutions in the seagrass percent cover (PC) mapping using remote sensing. This is important to determine the spatial resolution of image that can still be effectively integrated with 1 × 1 m plot size field data. This research aimed at assessing the accuracy and spatial distribution of seagrass PC map modelled from image at different spatial resolutions, using seagrass field data measure at 1 m2 plot size. Two multispectral satellite images namely WorldView-2 (2 m) and PlanetScope (3 m) were used for this research and simulated to 5 m, 10 m, 15 m, and 30 m. Kemujan and Lombok Island were selected as the study area, and seagrass beds in each island have different characteristics. Machine learning random forest regression was used to perform empirical modelling and the mapping accuracy was assessed using independent seagrass PC samples. The results indicated that 1 m2 plot size is still effective to be integrated with image up to 30 m spatial resolution, where the RMSE and overall seagrass PC pattern is relatively similar but the level of information precision is reduced at lower spatial resolution. Furthermore, we found out that the main factor that strongly determines the success use of 1 m2 plot size and the mapping accuracy is the configuration of the seagrass bed in the study area. Seagrass PC in the more continuous seagrass bed can be mapped with higher accuracy than in patchy seagrass bed.

Sulphur nutrition index in relation to nitrogen uptake and quality of winter wheat grain

A sulphur nutrition index (SNI) is an analogue of the N nutrition index, which is a widely used simple indicator of plant N status. The aim of this study was to relate the SNI (ratio of S concentration in shoot biomass to critical S concentration - Sc) to N uptake, grain yield and breadmaking quality of winter wheat (Triticum aestivum L.) grain during 4-yr small-plot field experiments realized under non-limiting N conditions in three different locations in the Czech Republic. The model of S dilution curve (Sc) developed by Reussi et al. (2012) for spring wheat was used for expression of the SNI. According to the model, optimal S concentration in shoot biomass was calculated using nothing but shoot biomass weight. The constant value of Sc = 0.55 was determined for shoot biomass weight lower than 1.0 t ha-1. A very strong correlation was recorded between the SNI and an N to S weight ratio (N:S) in shoot biomass. Both, optimal N:S weight ratio in shoot biomass and qualitative parameters of grain (particularly Zeleny sedimentation volume, grain protein content and wet gluten content) were recorded if the SNI exceeded values of 0.80 at the beginning of stem elongation, 0.70 at the late boot stage, and even 0.60 at the beginning of heading despite the fact that the Reussi et al.’s model of S dilution curve was originally applicable only until the end of stem elongation. Correlation between the SNI and relative grain yield was weak

Устойчивость микробиологической активности дерново-подзолистой почвы в условиях применения диатомита и цеолита

Устойчивость микробиологической активности дерново-подзолистой почвы в условиях применения диатомита и цеолита

The effect of stand structure on the grain quality of spring barley

The results of 81 different crop management practices in spring barley grown in small-plot field trials on fertile soils in central Moravia were assessed during 2014–2016 with the aim to achieve the highest gross margin (GM – calculated as the difference between revenues and direct costs). GM was most affected by protein content in the grain below 12% corresponding to malting quality. Analyses identified greater determination level of non-linear relationships between stand structure elements and the content of nitrogen substances in the grain. This indicates that the probability of obtaining high quality malting barley is increased when a high level of sinks (number of grains/m<sup>2</sup>) corresponding to availability of sources, mainly water, is formed by optimal plant density (300–400/m<sup>2</sup>) and balanced combination of both structural elements of crop stand, i.e. – number of spikes per plant (2–4) and number of grains per spike (18–26). In case that the high level of sinks will be formed predominantly by one element, the risk of higher protein content in grain increases. This constitutes the requirement of early sowing and uniform, synchronized tillering and efficient use of nitrogen fertilizers.

Szarvasi-1 and Its Potential to Become a Substitute for Maize Which Is Grown for the Purposes of Biogas Plants in the Czech Republic

The domestic biogas market has been developing rapidly, and legislation (The Act) supporting the use of renewable energy sources has come into force. In light of this act and investment support from national programs co-financed by the European Union (EU), the total number of biogas plants has recently increased from a few to 600. The total capacity of electricity generation of those 600 installed plants exceeds 360 Megawatts (MW) (as of mid-2018). Such dynamic growth is expected to continue, and the targets of the National Renewable Energy Action Plan are projected to be met. The use of waste material, which was urgently needed, was the original aim of biogas plants. However, in certain cases, the original purpose has transformed, and phytomass is very often derived from purpose-grown energy crops. Maize is the most common and widely grown energy crop in the Czech Republic. Nevertheless, maize production raises several environmental issues. One way to potentially reduce maize’s harmful effects is to replace it with other suitable crops. Perennial energy crops, for example, are possible alternatives to maize. A newly introduced species for the conditions of the Czech Republic, Elymus elongatus subsp. ponticus cv. Szarvasi-1, and some other well-known species—Phalaris arundinacea L. and Miscanthus × giganteus—are suitable for Czech Republic climate conditions. This paper presents the findings of the research and evaluation of environmental, energy-related, and economic aspects of growing these crops for use in biogas plants. These findings are based on 5-year small-plot field trials. The energy-related aspects of producing Elymus elongatus subsp. ponticus cv. Szarvasi-1, Phalaris arundinacea L., and Miscanthus x giganteus are reported on the basis of experiments that included measuring the real methane yield from a production unit. The economic analysis is based on a model of every single growing and technological operation and costs. The environmental burden of the individual growing methods was assessed with a simplified life cycle assessment (LCA) using the impact category of Climate Change and the SimaPro 8.5.2.0 software tool, including an integrated method called ReCiPe. The research findings show that Szarvasi-1 produces 5.7–6.7 Euros (EUR) per Gigajoule (GJ) of energy, depending on the growing technology used. Szarvasi-1 generates an average energy profit of 101.4 GJ ha−1, which is half of that produced by maize (214.1 GJ ha−1). The environmental burden per energy unit of maize amounts to 16 kg of carbon dioxide eq GJ−1 compared with the environmental burden per energy unit of Szarvasi-1, which amounts to 7.2–15.6 kg of CO2 eq GJ−1, depending on the yield rate. On the basis of the above-mentioned yield rate of Szarvasi-1, it cannot be definitively recommended for the purpose of biogas plants in the Czech Republic.

Efficacy of biological formulations against Neoglocianus maculaalba and Dasineura papaveris in Papaver somniferum

The effectiveness of selected insecticides against capsule weevils (Neoglocianus maculaalba) and capsule midges (Dasineura papaveris), which are the main pests of breadseed poppy, was verified in a small-plot field experiment in 2015–2017. The effect of foliar application was evaluated according to boreholes on capsule surfaces caused by the feeding of capsule weevil adults and larvae numbers in capsules collected approximately 4 weeks after application. Biological efficacy of the tested biological formulations Spintor (active ingredient spinosad 240 g/l) in dosage 0.4 l/ha and NeemAzal T/S (active ingredient azadirachtin A 10.6 g/l) in dosage 3 l/ha against N. maculaalba larvae in individual years of monitoring ranged from 46.4% to 77.7% and from 67.7% to 82.9%, respectively. The effect of the formulation Prev B2 (boron ethanolamine corresponding to 2.1% of water-soluble boron) in 0.3% dosage was in the range of 59.5–81.9%. Their efficacy did not differ significantly compared to the registered chemical standards Biscaya 240 OD (active ingredient thiacloprid 240 g/l) and Decis Mega (active ingredient deltamethrin 50 g/l). Therefore, these biological insecticides are potentially useful for the effective control of N. maculaalba and D. papaveris population densities and reduction of damage they cause to breadseed poppy.

On the Regulation of the Joint Use of Growth Stimulants and Pesticides in Forest Growing

The results of studying the effect of the growth stimulants Verva and Verva-El on the growth qualities of pine ordinary seedlings grown under the pre-sowing soil preparation using the roundup (glyphosate) herbicide are presented. The necessity of the presented experiments is connected with the establishment of the impact of the joint effect of new growth-promoting drugs and pesticides traditionally used in forestry on woody plants. It was shown that under laboratory conditions, the simultaneous presence of the roundup herbicide in the growth medium (agaragar) and seed treatment with the growth stimulants Verva and Verva-El leads to an inhibition of the growth of two-week-old pine seedlings, due to a decrease in the size of the roots. In the small-plot field experiment, an increase in the stem height was found in the variants using stimulants relative to this indicator in the variant where the pine was grown only with the use of roundup.

Improvement of the K-Factor of USLE and Soil Erosion Estimation in Shihmen Reservoir Watershed

The estimation of soil erosion in Taiwan and many countries of the world is based on the widely used universal soil loss equation (USLE), which includes the factor of soil erodibility (K-factor). In Taiwan, K-factor values are referenced from past research compiled in the Taiwan Soil and Water Conservation Manual, but there is limited data for the downstream area of the Shihmen reservoir watershed. The designated K-factor from the manual cannot be directly applied to large-scale regional levels and also cannot distinguish and clarify the difference of soil erosion between small field plots or subdivisions. In view of the above, this study establishes additional values of K-factor by utilizing the double rings infiltration test and measures of soil physical–chemical properties and increases the spatial resolution of K-factor map for Shihmen reservoir watershed. Furthermore, the established values of K-factors were validated with the designated value set at Fuxing Sanmin from the manual for verifying the correctness of estimates. It is found that the comparative results agree well with established estimates within an allowable error range. Thus, the K-factors established by this study update the previous K-factor system and can be spatially estimated for any area of interest within the Shihmen reservoir watershed and improving upon past limitations.

Phenotypic diversity and heritability in Eragrostis tef under irrigated Mediterranean conditions

Tef (Eragrostis tef (Zucc.) Trotter) is a C4 annual cereal, common in Ethiopia, where it was presumably domesticated. Worldwide interest in tef cultivation and consumption has considerably increased in the last few decades because it is a gluten-free grain with high nutritional value. Here we report on the genetic diversity and heritability in a tef germplasm collection characterized in Israel. A total of 408 accessions of tef held in the Israel Gene Bank were grown in 2015 under common garden (screen-house) conditions for propagation and initial phenotyping. A diversity panel, consisting of 273 accessions representing the entire collection's range of phenotypic diversity, was assembled and evaluated in small field plots in 2016. Further evaluation was conducted in 2017, in single-plant field plots (to eliminate admixtures). A representative plant (plot) was selected from each accession grown in 2017 and its single seed descent progenies where grown in 2018 in single-plant plots. The collection exhibited a wide diversity for each of the measured phenotypic traits, across all four environments. High grain yield was associated in most cases with early flowering time, whereas higher biomass was associated with late flowering. Heritability estimates, calculated based on the 2017, 2018 data, varied between 0.11 for plant biomass and 0.75 for 1000 grain weight. This study shows that tef can successfully grow and produce under irrigated Mediterranean conditions. The wide diversity available in our germplasm collection can provide the foundations for breeding new tef cultivars that are better adapted to these conditions.

Natural 13C abundance reveals age of dietary carbon sources in nematode trophic groups

We determined the 13C/12C ratio (expressed as δ13C ‰) of microbial biomass and nematode trophic groups in a small-plot field experiment with soil converted from C3- to C4-crop (silage maize) 20 years ago. During this period, the plots were subjected to three different organic input treatments: 1) maize stubbles and roots left after harvest (MS), 2) MS plus annual addition of aboveground maize biomass (MS + B), and 3) MS plus annual addition of faeces from sheep fed exclusively with maize (MS + F). The different δ13C value of C3- and C4-crops allowed us to distinguish between old (>20 years old) C3-derived C and recent (<20 years old) C4-derived C incorporated into microbial biomass and nematodes.The δ13C value of phytophagous nematodes closely matched that of the maize. Bacterivorous nematodes had higher δ13C values than fungivorous nematodes and microbial biomass indicating that the C sources of bacterivorous nematodes are more recent than those of fungivorous nematodes and microbial biomass. At low abundance of fungivorous nematodes (MS and MS + F), the microbial biomass had higher δ13C values than the fungivorous nematodes, whereas their δ13C values were comparable at higher densities of fungivorous nematodes (MS + B). The higher C4-derived input in MS + F and MS + B treatments increased the δ13C values of bacterivorous nematodes and microbial biomass.In MS and MS + B treatments, recent C4-derived C accounted for 50 and 70% of microbial biomass-C, respectively. Corresponding values for fungivorous and bacterivorous nematodes were 30 and 75%, and 65 and 85%, respectively.We conclude that fungal-based decomposition pathways contribute more to the turnover of old soil C than bacterial-based decomposition. A substantial fraction of the microbial biomass and fungivorous nematode C in the MS treatment (50 and 70%, respectively) was C deposited in the soil more than 20 years ago, confirming that decade-old SOC remains biologically active.

Effect of different drip irrigation regimes on tuber and starch yield of potatoes

Small-plot field trials monitored the effect of drip irrigation of potatoes on tuber and starch yield. The trials were performed at two different localities in two trial years, 2016 and 2017. The subject of the evaluation included two cultivars with different vegetation periods (the very early cv. Monika and the semi-early cv. Jolana). Four repeated trials studied 4 irrigation treatments according to the available water capacity (AWC) of the soil, i.e. without irrigation, irrigation when soil humidity decreased below 60, 65 and below 70% AWC. All monitored parameters reflected a positive effect of irrigation in comparison to the non-irrigated control. The Žabčice locality showed the highest tuber and starch yields mostly after medium-intensity irrigation. The Valečov locality achieved the highest tuber and starch yields after the highest-intensity irrigation. Subject to the locality and the cultivar, the recommendation is to introduce automatic irrigation start when the soil humidity drops to 65% AWC for heavy soils and 70% AWC for medium heavy soils.

Sensitivity of sunflower cultivar PR63E82 to tribenuron and propaquizafop in different weather conditions

The aim of this work was to verify and assess the tolerance of the PR63E82 (ExpressSun) sunflower cultivar to tribenuron, propaquizafop and their tank-mix combination in two rates under various weather conditions. Three small-plot field trials were carried out on sunflower in Prague, Czech Republic, from 2015 to 2017. High phytotoxicity (25–56%) of tribenuron (TBM) + non-ionic surfactant was observed in 2015 and 2016 when the sunflower was sown in mid-April. In 2017, phytotoxicity was significantly lower (4–6%), probably due to a later sowing of sunflower (May), and hence higher temperatures. The main symptoms of TBM phytotoxicity were leaf chlorosis, necrosis and growth retardation. Propaquizafop (PQF) injury was minimal in 2015 and 2017. A higher phytotoxicity (10–13%) was recorded in 2016, probably due to a hail which occurred 2 days after T2 (second application term (sunflower BBCH 14)) application. Plant injury had puckered leaves and also made more side branches. TBM + PQF damaged sunflower plants most of the tested herbicide treatments (phytotoxicity 3–62%). High phytotoxicity caused stem branching, increased number of sunflower heads and decreased yield.