Outdoor Pot Experiment Research Articles

Rhizobial diversity impacts soybean resistance, but not tolerance, to herbivory during drought

Biodiversity within ecological communities has been shown to influence plant resistance and tolerance to herbivory, and may strongly interact with climate change. However, the effects of diversity within microbial symbionts on their plant hosts’ responses to herbivores is less well documented, particularly within the context of agricultural systems. Here we examine the interactive effects of rhizobial diversity and drought in promoting soybean resistance and tolerance to insect and mammalian herbivores in an outdoor pot experiment. We demonstrate that soybean plants provided with a diverse mixture of rhizobial strains experience 30% less damage by chewing insect herbivores under both drought (reduced watering and increased temperature) and ambient weather conditions, as well as half as much colonization by aphids under drought conditions. This effect was not due to the presence of any particularly beneficial rhizobial strain (i.e., not a selection effect), but rather due to an enhanced benefit provided by the rhizobial strains in combination (i.e., a complementarity effect). No effects of rhizobial diversity were observed on the rate of defoliation by rabbits. While rhizobial diversity did affect soybean resistance to insect herbivores, these differences in insect damage did not carry through to affect soybean growth or final yield. Thus, soybean plants exhibited high tolerance to herbivory regardless of our experimentally imposed rhizobial diversity or drought treatments. With future projections for increased pest outbreaks and drought, understanding the factors that can sustainably enhance agricultural yield is critical. Our results suggest that promoting rhizobial diversity within soybean agriculture may be one nature-based solution to promote the resistance of this critical crop to insect pests.

Biochar promotes the growth of apple seedlings by adsorbing phloridzin

Apple replant disease (ARD) has been reported in all major apple-growing regions of the world, and abiotic (phenolic compounds including phloridzin) and biological (bacteria, fungi and nematode) factors are important causes of ARD. This study aimed to assess the effect of phloridzin adsorption on biochar pyrolyzed at different temperatures and the effectiveness of biochar addition on the growth of Malus hupehensis Rehd. seedlings under phloridzin stress. Three biochar treatments were considered (BC300, BC400 and BC500), pyrolyzed at three different temperatures (300°C, 400°C and 500°C, respectively). Batch adsorption experiments revealed that BC300 had the maximum adsorption efficiency. The BC300 treatment was then selected for isotherm and kinetic fitting to investigate the influence of pH on the adsorption process and determine the phloridzin adsorption mechanism. The biochar was found to have a single-layer phloridzin adsorption effect, and the adsorption rate was related to the biochar concentration and pyrolysis temperature. A outdoorpot experiment was conducted to analyze the biochar adorption to phloridzin in soil. Phloridzin addition significantly inhibited seedling growth and biochar significantly reduced the soil phloridzin content. BC300 had the best adsorption effect of the three biochar treatments. Compared with the replant soil (CK), biochar (especially BC300) increased the biomass of the seedlings and the antioxidant enzyme activity in the leaves. The soil enzyme activity, organic matter and bacteria numbers increased significantly after biochar addition. The best seedling growth and soil conditions were found for BC300. These results reveal that biochar addition can significantly reduce the phloridzin content and promote seedlings growth, and the effectiveness of the biochar depends on the pyrolysis temperature.

Effects of combined nitrification inhibitors on soil nitrification, maize yield and nitrogen use efficiency in three agricultural soils

Application of nitrification inhibitors (NIs) with nitrogen (N) fertilizer is one of the most efficient ways to improve nitrogen use efficiency (NUE). To fully understand the efficiency of NIs with N fertilizer on soil nitrification, yield and NUE of maize (Zea mays L.), an outdoor pot experiment with different NIs in three soils with different pH was conducted. Five treatments were established: no fertilizer (Control); ammonium sulfate (AS); ammonium sulfate + 3, 4-dimethyl-pyrazolate phosphate (DMPP) (AD); ammonium sulfate + nitrogen protectant (N-GD) (AN); ammonium sulfate + 3, 4-dimethyl-pyrazolate phosphate + nitrogen protectant (ADN). The results showed that NIs treatments (AD, AN and ADN) significantly reduced soil nitrification in the brown and red soil, especially in AD and ADN, which decreased apparent nitrification rate by 28% - 44% (P < 0.05). All NIs treatments significantly increased yield and NUE of maize in three soils, especially ADN in the cinnamon soil and AD in the red soil were more efficiency, which significantly increased maize yield and apparent nitrogen recovery by 5.07 and 6.81 times, 4.39 and 8.16 times, respectively. No significant difference on maize yield was found in the brown soil, but AN significantly increased apparent nitrogen recovery by 70%. Given that the effect of NIs on both soil nitrification and NUE of maize, DMPP+N-GD was more efficient in the cinnamon soil, while N-GD and DMPP was the most efficiency in the brown and red soil, respectively. In addition, soil pH and soil organic matter play important role in the efficiency of NIs.

Water flux and biomass production of native plants at different substrate compactions for landfill phytocaps in Southeast Queensland, Australia

Phytocaps for landfills and degraded sites have multiple benefits provided by the established vegetation, including reducing substrate moisture content and drainage through evapotranspiration. One of the factors affecting plant development measured by biomass production is substrate compaction. However, the relationship between drainage and biomass production related to substrate compaction is largely unknown. In an outdoor pot experiment, four native plant species: Eucalyptus terreticornis, Acacia concurrens, Allocasuarina littoralis, and Themeda triandra, grown in coal overburden at three different relative compactions (RC) levels (64%, 77% and 87% of the maximum compaction) in Southeast Queensland, Australia, over seven months. Evapotranspiration rate was measured by change in pot weight. Drainage for each pot was collected in a container after every irrigation and rainfall. Biomass of plants were harvested for dry shoot and root weight measurement. Additionally, root length density was obtained by a root scanner. Our statistical model predicted that 69.8% RC for maximum weekly ET. Overall, 77% RC treatment resulted in higher total evapotranspiration (1.5%), more significant shoot and root biomass production (17.2% and 11.8%, respectively), higher root length density (33.4%) and lower total drainage (20%) compared to 64% and 87% RC treatments. Native woody species had a higher rate of evapotranspiration and a lower rate of drainage than the native grass. Reduction in drainage was correlated with increase in evapotranspiration rate for all plant species, as the soil moisture content decreases through evapotranspiration. These findings support the notion of maximising evapotranspiration to minimise drainage, a key objective for phytocap design. From biomass production, root biomass closely correlates to a reduction in drainage. Multiple lines of evidence from this study indicate that 77% RC treatment maximises evapotranspiration and plant development and minimises deep drainage for phytocap applications, even though harsh microclimate in this experiment may have constrained plant development and affected the water flux.

Yield and water-use related traits in landrace and new soybean cultivars in arid and semi-arid areas of China

Empirical soybean breeding has improved its yield in arid and semi-arid areas of China. The objective of this study was to identify the important traits found in successful commercial soybean cultivars following the domestication of landraces through breeding in the semi-arid region of North-west China. A further objective was to identify any key traits that can be targeted using trait-based selection to improve yield under drought. Seed yield, phenology, water-use, water-use efficiency and their related traits in soybean landraces and successful cultivars were compared over a four year period in the field and this was supplemented with an outdoor pot experiment. The results in both field and pot experiments showed that successful soybean cultivars have a reduced thermal time to flowering but the thermal time for seed filling has increased. This change in partitioning of phenological time in the commercial cultivars resulted in a lower number of pods, fewer seeds per unit area but an increase in 100-seed weight, harvest index and seed yield. New soybean cultivars with high seed yield also had a lower vegetative biomass and less water use in both field and pot experiments than landraces but the lower water use did not compromise seed yield. The commercial cultivars also had a lower pod wall ratio (ratio of pod wall weight to total pod weight at maturity) which also contributed to yield by improving harvest index. We conclude that the key traits that have been altered as a result of soybean breeding in arid and semi-arid areas of China have been (1) a shortening of the duration between sowing and flowering but an extension of the seed filling period, (2) fewer pods but an increase in seed number per pod and 100-seed weight and also a decreased pod wall ratio, (3) an increased harvest index and (4) a reduced water use, particularly in the deeper soil layers. • Yield improvements in soybean in dry areas were investigated in a study over four years. • Soybean breeding resulted in a shorter thermal time to flower but a longer thermal time for seed filling. • The longer reproductive period resulted in a higher seed number per pod, seed weight and seed yield. • A reduction in the thermal time to flowering reduced leaf fraction and total water-use but did not compromise seed yield. • Newer varieties had lower soil water use at depth but a higher HI than the landraces.

Effects of Biochar-Based Fertilizers on Energy Characteristics and Growth of Black Locust Seedlings

To understand ecological and energy problems in the karst area of Guizhou, China, the effects of using biochar-based fertilizers on the energy characteristics of different species of black locust were studied. To determine the most suitable species and the best rational application method of biochar, an outdoor pot experiment was performed using three species of black locust (White-flowered locust (W), Hong-sen locust (S), and Large-leaf fast-growing locust (L)). There were six treatments: control (CK), MF, RH2MF, RH4MF, W2MF, and W4MF (M—compost; F—NPK fertilizer; RH—rice husk biochar; and W—wood biochar), where the numbers represented the mass ratio of biochar to soil. Biochar-based fertilizers had significant effects on the total organic carbon (TOC), total nitrogen (TN), total potassium (TK), branch gross calorific values (GCV), and ash removal calorific values (AFCV) of seedlings. RH4MF had the best overall values. Different species had significant effects in all indicators (except for TN); the effect on S was better than that of W and L. Principal component analysis showed that RH4MF-S had the highest comprehensive scores. In summary, Hong-sen locust (S) was a high-quality energy species and RH4MF may be used as fertilization for energy forest development. This study provides a reference for future long-term energy forest research in this area.

Crops Change the Morphology, Abundance, and Mass of Microplastics in Mollisols of Northeast China.

Degradation of microplastics (MPs) by both physicochemical and biological processes in the natural environment is determined by the enzymes inside the soil, and which was severely influenced by crop growth and straw amendment (SA). However, it is still unclear how crop growth and SA influence degradation of MPs in soils. In this study, both catalase and sucrase were measured, and the stereomicroscope combined with microscopic infrared spectroscopy and scanning electron microscope (SEM) was used to detect the morphology and quantity of low-density polyethylene microplastic (LDPE-MP) and low-density polypropylene microplastic (LDPP-MP), after crop growth (maize and soybean, with and without SA, 1 and 2% MP) in an outdoor pot experiment, in the Mollisols. The results showed that the growth of the crops changed the morphology, functional groups (e.g., methylene, carbonyl), total mass, and abundance ratio of MPs of different sizes. These were possibly caused by enzymes that were significantly influenced by crop types, abundance, and types of MPs in the soils. Maize growth decreased the mass of LDPE-MP and LDPP-MP by 28.7 and 32.7%, respectively, and 2% (w/w) of LDPP-MP addition in soil decreased mass of 9%, which was higher than that in 1% (w/w) LDPP-MP addition in soil. Soybean growth with SA decreased the mass of LDPE-MP and LDPP-MP by 36.6 and 20.7%, respectively, than the control treatment (CK). Compared with CK, both crop growth and SA changed the abundance of MPs of different sizes and decreased the mean size of MPs. The LDPE-MP could be more easily degraded by enzymes in the soils compared to LDPP-MP when the MP size was smaller with surface roughness. Generally, both maize and soybean growth can accelerate MP change in soils, and MP change process was mainly determined by SA, MP types, and the dose effect of MP.

Phosphorus-modified biochar cross-linked Mg-Al layered double-hydroxide stabilizer reduced U and Pb uptake by Indian mustard (Brassica juncea L.) in uranium contaminated soil

The decommissioning of uranium tailings (UMT) is usually accompanied by uranium (U) contamination in soil, which poses a serious threat to human health and ecological security. Therefore, the remediation of uranium pollution in soil is imminent from ecological and environmental points of view. In recent years, the use of biochar stabilizers to repair uranium tailings (UMT) soil has become a research hotspot. In this study, a novel phosphorus-modified bamboo biochar (PBC) cross-linked Mg–Al layered double-hydroxide composite (PBC@LDH) was prepared. The hyperaccumulator plant Indian mustard (Brassica juncea L.) was selected as the test plant for outdoor pot experiments, and the stabilizers were added to the UMT soil at the dosage ratio of 15 g kg−1, which verified the bioconcentrate and translocate of U and associated heavy metal Pb in the UMT soil by Indian mustard after stabilizer remediated. The results shown that, after 50 days of growth, compared with the untreated sample (CK), the Indian mustard in PBC@LDH treatment possessed a better growth and its biomass weight of whole plant was increased by 52.7%. Meanwhile, the bioconcentration factors (BF) of U and Pb for PBC@LDH treatment were significantly decreased by 73.4% and 34.2%, respectively; and the translocation factors (TF) were also commendable reduced by 15.1% and 2.4%, respectively. Furthermore, the Tessier available forms of U and Pb in rhizosphere soil showed a remarkably decrease compared with CK, which reached by 55.97% and 14.1% after PBC@LDH stabilization, respectively. Complexation, precipitation, and reduction of functional groups released by PBC@LDH with U and Pb described the immobilization mechanisms of biochar stabilizer preventing U and Pb enrichment in Indian mustard. As well as, the formation of U-containing vesicles was prevented by the precipitation of −OH functional groups with free U and Pb ions around the cell tissue fluids and vascular bundle structure of plant roots, thereby reducing the migration risk of toxic heavy metals to above-ground parts. In conclusion, this research demonstrates that the PBC@LDH stabilizer offers a potentially effective amendment for the remediation of U contaminated soil.

Effects of Combined Nitrification Inhibitors on Nitrogen Transformation, Maize Yield and Nitrogen Uptake in Two Different Soils

ABSTRACT Nitrification inhibitors (NIs) affect nitrogen (N) cycle and crop yield, but how the combinations of NIs influence N transformation and maize yield remains unclear. An outdoor pot experiment was performed to explore the effect of three NIs (nitrapyrin (CP), 3, 4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD)) and their combinations on mineral N transformation, yield and N use efficiency (NUE) of maize in a brown soil and a cinnamon soil from northeast China. Higher yield and NUE were obtained in the brown soil than that in the cinnamon soil. All treatments with NIs significantly increased NH4+-N content, grain yield and NUE in both soils, especially for NIs combination (DMPP + DCD in the brown soil and CP + DCD in the cinnamon soil). These two treatments significantly increased yield and apparent nitrogen recovery by 1.84 and 2.31 times, 10.24 and 6.39 times, respectively, compared with N fertilizer treatment. They also showed lower apparent nitrification rates (17.2% and 53.7%, respectively) compared with single NIs treatments. Considering both the inorganic N supply and agronomic effect of NIs, DMPP + DCD and CP + DCD are the best strategies for the application of NIs in the brown soil and cinnamon soil.

The effect of fertilizer type on nitrogen uptake by maize from recently formed soil organic matter#

AbstractBackgroundSoil organic matter (SOM) formed under legume‐based grasslands may serve as an important source of nitrogen (N) for subsequent maize growth.AimWe aimed at studying effects of fertilizer type (organic and mineral N and phosphorus (P) fertilizers) on N release from recently formed SOM and N utilization by plants.MethodsThe effects of mineral and organic (meat and bone meal) N and P fertilization on SOM turnover were examined under maize (Zea mays L.) on a sand loamy typic hapludult in an outdoor pot experiment over 55 days. The plant uptake of N derived from recently formed SOM was investigated by dual labeling this SOM pool with 15N and 13C.ResultsOrganic and mineral fertilized maize acquired similar amounts of N derived from recently formed SOM, which was twice as high as for unfertilized plants. Rhizosphere soil with organic fertilizer had higher 13C loss than unplanted soil, whereas no extra 13C was lost under mineral fertilization. On the contrary, a lower 13C loss from planted compared to unplanted soil was observed in unfertilized soil.ConclusionsBoth mineral and organic fertilizers increased plant growth and N uptake, whereas only organic fertilizers accelerated SOM turnover in the rhizosphere as compared to bulk soil. Thus, this study implies that the fertilizer types differently affected the mechanisms controlling the utilization of N bound in recently formed SOM.

Effects of biochar and biochar compound fertilizer on the communities of nitrifier and denitrifier in a reclaimed soil from coal-mining area

As a new soil amendment strategy, the effects of biochar application on soil microbial community have been reported in literature, but little information is available on the response of nitrogen-related microbial communities to biochar application in the reclaimed soil from coal-mining area. Through an outdoor pot experiment with reclaimed soil from coal-mining area of Huaibei, the effects of biochar and biochar compound fertilizer on nitrifier and denitrifier communities were investigated by real time PCR (qPCR) and terminal-restricted fragment length polymorphism (T-RFLP). There were five treatments: control (CK), NPK fertilizer (CF), biochar compound fertili-zer (BF), 2% biochar and NPK fertilizer (LB), 4% biochar and NPK fertilizer (HB). Results showed that compared with the CK, the treatments CF, BF, LB and HB significantly increased the abundance of ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB), nirK and nirS genes of denitrifier. Compared with the CF treatment, BF, LB and HB significantly increased the abundance of AOB and nirK genes by 42.9%-82.1% and 33.5%-62.7%, respectively. Results of redundancy analysis showed that soil organic carbon, pH, NH4+-N and available potassium significantly affected AOB community structure, while soil organic carbon concentration, pH and NO3--N concentration significantly altered nirK-denitrifier community structure. Therefore, the application of biochar and biochar compound fertilizer could improve soil quality of the reclaimed soil from coal-mining area, and increase the abundances of nitrifier and denitrifier and alter community structure of AOB and nirK-denitrifier.

The effect of phosphorus split application on use efficiency and dynamic of phosphorus and zinc at the soil, aerial parts, and grain, and Zinc biofortification of two rice varieties (Oryza sativa L.) (Hashemi and Guilaneh)

Introduction: Despite the P vitality for rice cultivation, its recovery index in paddy soils is very low and less than 25% of added P, and the rest goes out of reach of rice plant through the P fixation by soil particles at different fractions. Also, despite abundant studies on the effect of basal soil P application, we face a lack of knowledge on research findings of the P splitting application and its effect on soil Zn concentration and tissues Zn content. Thus, the current research project was done to explore the effect of P splitting application at flooded conditions on the soil and rice plant tissues P and Zn variation trend at the different rice growth stages of two more common varieties (Hashemi and Guilaneh varieties). Materials and methods: The outdoor pot experiment was conducted on a three factors factorial experiment in a randomized complete block design with three replications in 2017 at the research farm of the rice research institute of Iran, Rasht. The experimental treatments were: phosphorus fertilizer split application at five levels, soil at two levels, and rice varieties at two levels (Hashemi (local variety) and Guilaneh(improved variety)), The P application treatments were: control (no added P), 100% basal, P split application at 50% basal and 50% at 20 days after transplanting (DAT), P split application at 50% basal and 50% at 60 days after transplanting (DAT), P split application at 50% basal, 25% at 20 days after transplanting, and 25% at 60 days after transplanting. Results: The results indicated that the highest soil available P and Zn concentrations were recorded at the flowering stage about 95.3 and 90.10, and 8.6 and 8.7 mgkg-1by two and three P split for Hashemi and Guilaneh, respectively. Also, the maximum P of rice grain was obtained about 0.17 and 0.20 mgkg-1 for Hashemi and Guilaneh, respectively. The Zn content of rice grain at P split pots was significantly more than control and 100% basal application. The highest agricultural recovery (13.31 and 12.72), physiological (693.19 and 740.10) and physiological-agricultural efficiency (482.00 and 753.00), P use efficiency (5.34 and 5.66), and apparent recovery (1998 and 1272.22 kg kg-1) were found for Hashemi and Guilaneh, respectively, in the two and three P split application. Furthermore, stepwise multiple regression analysis revealed that the soil available P concentration at ripening stage, Zn content of the grain, and Zn concentration at rice aerial parts can explain 52% of grain yield variations for studied rice cultivars. Conclusion: The three-stage P splitting (50% soil basal, 25% 20 DAT, and 25% 60 DAT) increased the Zn content of the Hashemi variety by about 54.72% at slit loam soil, whereas the Guilaneh rice variety was received a 37.5% increase in Zn content of grain in silty clay through two-stage P splitting (50% soil basal and 50% 20 DAT) compare to control (100 % basal). It can be concluded both three and two-stage P splitting might be positively significantly effective on rice grain nutritional quality.

Response of 15N to corn straw and biochar application in soils with different fertility levels, during corn seedling stage

Nitrogen (N) is a necessary and the most limiting nutrient in crop production. Addition of organic amendments to the soil can improve the use of N fertilizer in crops. However, the response of N to corn straw and biochar application in soils with different fertility levels is yet not well studied. This study investigates N utilization and uptake by corn plant at seedling stage using 15N-label tracer method. Two soils with different fertility levels were selected: (i) high fertility soil (HF), and (ii) low fertility soil (LF). The HF and LF soils were amended with biochar (HFB and LFB) and corn straw (HFC and LFC) in an outdoor pot experiment. The results showed that N absorption in corn plant increased by 23.47 − 30.58% (HFB), and by 10.34 − 13.59% (HFC) compared with unamended HF soil, and increased by 26.09 − 41.53% under LFB and by 13.59 − 20.23% in LFC compared with unamended LF soil. The 15N utilization rate increased in the order of: HFB > HFC > HF and LFB > LFC > LF, illustrating that biochar and corn straw application increases the efficiency by which corn plant utilizes N. Biochar and corn straw application significantly reduce 15N losses in the soil and improve 15N utilization in corn, particular in low fertile soil.

Evaluation of Maize Growth Following Early Season Foliar P Supply of Various Fertilizer Formulations and in Relation to Nutritional Status

The efficiency of phosphorus (P) use in agriculture needs to be improved, with farmers being increasingly forced by law to reduce P soil fertilization. Thus, P foliar application might become more important in agriculture. The effect of foliar P fertilization has not been widely studied in maize, despite it being a crop with high P demand during juvenile development. Our aim was to investigate the effect of P foliar application during juvenile development on maize crop growth and yield. We conducted outdoor pot experiments to investigate the effect on P uptake, translocation, and dry matter following three applications of foliar fertilizer of various P formulations and with additional P soil fertilization between the 4th and 6th leaf stage during two growing seasons. To determine direct and possible long-term effects, plants were harvested at various developmental stages. P foliar application resulted in a significant increase in P concentration in all plant parts ten days after the last application, regardless of P form, nutritional status, or year. P concentration remained high only in those parts of the plant that were present during foliar application. Biomass effects were sporadically visible until flowering, but not at maturity. We conclude that foliar P fertilization during juvenile development does not increase yield but might nevertheless be a useful remedy for short-term P deficits.

Acidified Biogas Residues Improve Nutrient Uptake and Growth of Young Maize

Biogas residues (BGR) contain a variety of plant nutrients and are, therefore, valuable fertilizers. However, ammonia (NH3) emissions occur during slurry and BGR application. These emissions can be reduced by lowering the pH of the BGR. Acidification technology works well for slurry, but little is known about the effects on fertilizer properties of acidified BGR (ABGR). This study aimed to examine the impact of acidification on the chemical composition of BGR and its influence on plant growth of juvenile maize and the soil pH, as well as the soluble soil phosphorous (P) and manganese (Mn), after application of ABGR. The soluble amount of nutrients in BGR was compared with that in ABGR. In an outdoor pot experiment, BGR and ABGR were incorporated in soil, and maize was grown for 8 weeks. Two different BGR P levels were compared with (NH4)2HPO4 and a control treatment without additional P. BGR acidification increased dissolved amounts of P from 15% to 44%, calcium from 6% to 59%, magnesium from 7% to 37%, and Mn from 2% to 15%. The dry matter of ABGR-fertilized maize was 34%, 45% higher than that of BGR-fertilized maize. The soluble Mn content in the soil was 74% higher with the low ABGR dose and 222% higher with the higher ABGR dose than the BGR treatments. The fertilizer efficiency of ABGR was higher than that of BGR, indicating that the absolute amount of applied fertilizer could be reduced in systems using ABGR.

Effect of emergence time on growth and fecundity of redroot pigweed (Amaranthus retroflexus) and slender amaranth (Amaranthus viridis): emerging problem weeds in Australian summer crops

AbstractRedroot pigweed (Amaranthus retroflexus L.) and slender amaranth (Amaranthus viridis L.) are considered emerging problematic weeds in summer crops in Australia. An outdoor pot experiment was conducted to examine the effects of planting time on two populations of A. retroflexus and A. viridis at the research farm of the University of Queensland, Australia. Both species were planted every month from October to January (2017 to 2018 and 2018 to 2019), and their growth and seed production were recorded. Although both weeds matured at a similar number of growing degree days (GDD), they required a different number of days to complete their life cycles depending on planting date. The growth period was reduced and flowering occurred sooner as both species experienced cooler temperatures and shorter daylight hours. Both species exhibited increased height, biomass, and seed production for the October-sown plants compared with other planting times, and these parameters were reduced by delaying the planting time. The shoot and root biomass of A. retroflexus and A. viridis (averaged over both populations) was reduced by more than 70% and 65%, respectively, when planted in January, in comparison to planting in October. When planted in October, A. retroflexus and A. viridis produced 11,350 and 5,780 seeds plant−1, but these were reduced to 770 and 365 seeds plant−1 for the January planting date, respectively. Although the growth and fecundity of these species were dependent on planting time, these weeds could emerge throughout the late spring to summer growing season (October to March) in southeast Australia and could produce a significant number of seeds. The results showed that when these species emerged in the late spring (October), they grew vigorously and produced more biomass in comparison with the other planting dates. Therefore, any early weed management practice for these species could be beneficial for minimizing the subsequent cost and energy inputs toward their control.

The Application Time-of-Day Effect for Trifloxysulfuron Against Velvetleaf as Affected by Nozzle Type

All previous studies reporting the application time-of-day effect for herbicides have been conducted with a single-orifice, flat fan nozzle. Whether an increased number of flat fans in the nozzle could affect the application time-of-day effect is unknown. A replicated outdoor pot experiment was conducted to determine the best application time for trifloxysulfuron from 05:00 (before sunrise), 07:00 (after sunrise), 09:00, 11:00, 13:00, 15:00, 17:00, 19:00 (before sunset), and 21:00 (after sunset) against velvetleaf when sprayed with a single-, dual-, or triplet-orifice flat fan nozzles. Trifloxysulfuron sprayed with the single-orifice flat fan nozzle at 05:00 was the least effective treatment reducing velvetleaf fresh weight by 51%. When the single-orifice flat fan nozzle was used, velvetleaf fresh weight, expressed as a quadratic polynomial function with a parabola opening upward, decreased as the application time changed from 05:00 to 11:00 (70% control); thereafter, it increased until 21:00. When the dual- and triplet-orifice flat fan nozzles were used, velvetleaf fresh weight, expressed as a quadratic polynomial function with a parabola opening downward, increased from 05:00 to 07:00; thereafter, it increased as the application time changed until 19:00 (the best application time, reducing velvetleaf fresh weight by 82%). Foliar nyctinasty in velvetleaf is responsible for decreased efficacy of trifloxysulfuron sprayed with the single-orifice flat fan nozzle before sunset. This obstacle can be overcome using the dual- or triplet-orifice flat fan nozzles.

The effect of potassium fertilization on the metabolite profile of tomato fruit (Solanum lycopersicum L.)

The macronutrient potassium (K) has vital physiological functions in plants and its availability can strongly impact quality of crops like tomato. The impact of K nutrition on conventional tomato fruit quality parameters has been described several times, but detailed investigations on the effect of K supply on the fruit metabolite profile are still rare. To fill this gap, we investigated the influence of K fertilization on the metabolite profile of tomato fruits. For this purpose, an outdoor pot experiment with three different cocktail tomato cultivars was performed. A fertilization regimen with five K levels was applied, ranging from deficiency to sufficient supply. Fruit samples were analyzed by untargeted GC×GC-MS to cover the primary metabolite profile as well as some secondary metabolites. As verified using ICP-OES, fruit K content was highly proportional to the supplied amount of K. At the metabolite profile level, the most prominent and cultivar-independent effect of increased K fertilization was the rise of tricarboxylic acid (TCA) cycle intermediates. Further effects were more cultivar-specific, for example an increase of the mobile nitrogen pool (e.g. amines like putrescine and amides like asparagine), changes in the profile of minor sugars (especially disaccharides) as well as higher levels of some secondary metabolites. Pronounced response patterns were mainly observed in the cultivars Primavera and Yellow Submarine that were recently characterized as higher yielding, demanding a stronger consideration of cultivar differences in future studies.

Sodium nitroprusside application regulates antioxidant capacity, improves phytopharmaceutical production and essential oil yield of marjoram herb under drought

Nitric oxide (NO) represents a crucial signal particle that plays a pivotal function in plant development, but its roles in improving drought tolerance in marjoram still unknown. The protective roles of foliage-spraying NO (as sodium nitroprusside, SNP; 0, 30, and 60 μM) on inducing drought tolerance in marjoram herb was evaluated by measuring the antioxidant defense system and phytopharmaceutical characteristics in an outdoor pot experiment. Under well-watered, SNP (30 and 60 μM) application significantly enhanced growth, essential oil (EO) yield, up-regulating antioxidant system, and improved water use efficiency (WUE) compared to untreated plants (0 μM SNP). Drought significantly inhibited marjoram growth, WUE, EO yield, catalase, and peroxidase activity as well as herbal extract reducing power and reflective index, whereas oxidative biomarkers (hydrogen peroxide, lipid peroxidation, protein carbonyl group accumulation, and electrolyte leakage) and EO specific gravity were drastically amplified relative to well-watered plants in the absence of SNP. Alternatively, under drought, SNP application mitigated drought induced-oxidative burst and improved WUE that associated with increasing plant biomass and EO assimilation relative to those in drought-affected herbs only. Phytopharmaceuticals of herbal extract (ascorbic acid, total soluble phenol, anthocyanin, and flavonoid) were significantly improved by drought and/or SNP foliar application. The promotive roles of SNP in moderating the depressing effect of drought on marjoram was attributable to up-regulating antioxidant capacity, improving secondary metabolite assimilation, and increasing WUE that accelerate drought tolerance and EO yield as well as improved EO fractions. The existing outcomes open innovative opportunities for obtaining precious natural antioxidants and phytopharmaceuticals by using arid regions.

Efficacy of increasing application rates and combination of herbicides and mowing at different growth stages of common teasel (Dipsacus fullonum)

AbstractCommon teasel is a troublesome invasive weed in North and South America. Additional information on the efficacy of herbicide application and mowing at different growth stages will help in common teasel management. First, an outdoor pot experiment was performed to assess the effects of increasing application rates and combinations of glyphosate and 2,4-D amine when applied at the 4-leaf, rosette, and bolting stages. Second, field experiments were performed to evaluate the impact of time of cutting on invasive common teasel height, head number, and head length. Finally, germinability of seeds collected from naturally growing plants was determined to evaluate the feasibility of mowing invasive common teasel after flowering. Only glyphosate applied at 1.08 kg ae ha−1 at the 4-leaf stage provided adequate control (&gt;90%). Although control was not satisfactory (&lt;90%) when applying glyphosate at 2.16 kg ae ha−1 at the rosette and bolting stages, and 2,4-D at 1.75 kg ai ha−1 at 4-leaf stage, significant injury and biomass decline were observed. Glyphosate and 2,4-D combinations did not improve common teasel control compared with single applications of each. Cutting rosettes strongly reduced inflorescence production (34%–49%) and cutting flowering plants prevented total regrowth. Germination of seeds averaged 14% when harvested 10 d after flowering, and maximum seed germination (&gt;90%) occurred 30 d after flowering. Glyphosate applied alone at the recommended commercial rate early in the growing season, together with cutting at the flowering stage, may be the most beneficial way of controlling invasive common teasel.