Grass Growth Research Articles

ВЛИЯНИЕ ВЛАГОУДЕРЖИВАЮЩИХ АГЕНТОВ НА ДЕКОРАТИВНЫЕ КАЧЕСТВА ГАЗОННОГО ПОКРЫТИЯ

The effect of wetting agents on the decorative qualities of the lawn covering formed by the plants of the bentgrass (Agrostis stolonifera L.) of the ‘PLS’ variety mixture has been studied. The studies were carried out in a small-plot field experiment on sandy soil, in the conditions of the Moscow region. All research is aimed at studying the demand in the golf industry, which will help to understand the effectiveness and appropriateness of the use of investigational agents. Watering is an important operation necessary for the normal growth and development of perennial grasses growing on a well-drained sandy profile of golf courses. It is also quite costly. Currently, there are a huge number of different agents, technologies and tools for monitoring the condition and care of the grass standg. According to the results of these studies, Revolution was the best wetting agent, with the lowest percentage of dry patches and optimum soil moisture throughout the entire study. According to the main indicators of decorativeness of the bentgrass, the highest scores on the NTEP scale were in the bentgrass stands with the use of Revolution in the volume of 20 l/ha: germination (6 / 6.6 / 5.6), color (6.6 / 7.6 / 6), uniformity (4.3 / 7 / 7.3) germination (6/6.6/5.6), colour (6.6/7.6/6), uniformity (4.3/7/7.3); with the use of Revolution in the volume of 10 l/ha – germination (5.6 / 6.6 / 5.6), color (6.6 / 7.6 / 6.6), uniformity (4.6 / 7.6 / 6).

Assessing grass water use efficiency through smartphone imaging and ImageJ analysis

Overwatering and underwatering grass are widespread issues with environmental and financial consequences. Current approaches to assessing grass water use efficiency (WUE) are inaccessible to the public. We developed an accessible method to assess grass WUE: combining smartphone imaging with open access color unmixing analysis. Images were converted from the RGB color space to the CIELAB color space using ImageJ—an open access, user-friendly software—to correct for uneven lighting without compromising image detail. We obtained parameters a* (unmixes green-to-red vector) and b* (unmixes blue-to-yellow vector). We hypothesized that WUE can be accurately determined from grass color and growth, which can be analyzed using CIELAB color unmixing. We tested how nine watering levels (100–900 mL every 4–5 days) affected Stenotaphrum secundatum (St. Augustine grass) over one month in Orange County, Southern California. Color was quantified using a*:b* ratios, growth was tracked using grass area, and pigment composition was analyzed using plot profiles. We analyzed whole samples in the uncontrolled real-world environment, individual leaves in a controlled homemade imaging box, and extracted pigments before and after paper chromatography. Results were clustered using Gaussian finite mixture models, implemented by R package ‘mclust’. Overall trends for grass coverage, a*:b* ratios, and pigment composition were consistent with real-world observations. Cluster analyses were consistent across image types, identified an ideal watering range (600–700 mL), and differentiated between underwatered and overwatered grass. Our hypothesis was supported. Our method can be applied in automated irrigation systems or apps, providing grass WUE assessment for regular consumer use.

Tannery Sludge Applied in High Doses in Elephant Grass as an Alternative Fertilization

ABSTRACT Tannery sludge has great potential for use in agriculture, however it is a potentially toxic waste, and it is necessary to establish the ideal dose for each crop. The objective of this study was to evaluate the influence of fertilization with liquid tannery sludge on growth, chlorophyll a fluorescence and gas exchange of Pennisetum purpureum in two production cycles. A 2 × 6 + 1 split plot scheme was used, where the first factor was composed of two productive cycles, the second factor different fertilizations doses: 0, 30, 70, 110, 150, 190 t ha−1 of liquid tannery sludge and an additional treatment with nitrogen, phosphorus and potassium control. Plant height, number of leaves and tillers, canopy and stem diameter, leaf area, dry matter, chlorophyll index (SPAD), chlorophyll a fluorescence and gas exchange were evaluated. The highest production of total dry matter was observed in the second production cycle. The range between 72–100 t ha−1 of liquid tannery sludge showed the greatest gains in growth and production of elephant grass. At doses above 150 t ha−1 of liquid tannery sludge, the photochemical apparatus begins to show possible damage to the photosystem II (PSII) and reductions in gas exchange.

Shade and nitrogen fertilization affect forage accumulation and nutritive value of C4 grasses differing in growth habit

AbstractLight reduction in silvopastoral systems and self‐shading in treeless grasslands can lead to shade‐avoidance responses by tropical grasses. Light environment in association with nitrogen (N) supply influence the growth and nutritive value of forage grasses. This study aimed to quantify forage accumulation (FA) and forage nutritive value of tropical grasses differing in growth habit in environments with contrasting light and N resources. A field study was conducted using ‘Jiggs’ bermudagrass [Cynodon dactylon (L.) Pers.] and ‘Mulato II’ hybrid brachiariagrass (Urochloa spp). Full‐sun environments were compared with shaded environments where shade cloth limited incident radiation to 45% of ambient. Low and high N treatments were imposed (30 and 120 kg N ha−1 after each harvest), resulting in a 2 × 2 × 2 factorial arrangement of treatments in four replicates of a randomized complete block design. Forage was harvested every 28 d from May to September in 2014 and 2015 to determine FA. Herbage crude protein (CP) concentration and in vitro digestible organic matter (IVDOM) were assessed. Annual FA was greater for Mulato II than Jiggs and for high‐N and full‐sun treatments. Species showed similar CP concentrations, but Mulato II had greater IVDOM than Jiggs, likely due to a greater leaf percentage. Shade increased CP concentration of the forages whereas effects on IVDOM were not consistent. Although more productive with greater leaf percentage and nutritive value than decumbent, stoloniferous Jiggs, upright‐growing, bunchgrass Mulato II was not persistent when multiple freeze events occurred during winter, limiting its adoption in cooler subtropical environments.

UROCHLOA GRASS GROWTH AS A FUNCTION OF NITROGEN AND PHOSPHORUS FERTILIZATION

The urochloa grass (Urochloa mosambicensis) is a perennial grass, C4 plant, with a high photosynthetic rate and CO2 fixation, persistent to water deficit, adapted to a wide diversity of soils and hot climate regions. Thus, the objective was to evaluate the urochloa grass growth and define the best models to estimate plant height as a function of nitrogen and phosphate fertilization. The experimental design was completely randomized, in the 2 x 2 factorial design (presence and absence of nitrogen presence and absence of phosphorus), with four replications. Was used a dose of nitrogen and phosphorus equivalent to 100 kg.ha-1 of N and 150 kg.ha-1 of P2O5, respectively. The following models were used: linear, power, gamma andlogistic to estimate plant height as a function of the following explanatory variables: days after planting, nitrogen and phosphorus doses. The criteria used to determine the best model(s) were as follows: higher adjusted coefficient of determination, lower Akaike information criterion, lower sum of square of residuals and high Willmott index. The plant height in the absence of nitrogen and phosphorus and when applied 100 kg.ha-1 of N and 150 kg.ha-1 of P2O5 was estimated more accurately by the Gamma model with high power of explanation. The adoption of the Gamma model allows to estimate the U. mosambicensis plant height, in a non-destructive manner, with high precision, speed and low cost, depending of age plant and nitrogen and phosphate fertilization.

English

Climate change has severely affected rainfall regularity, limiting grass growth and thus fodder availability. Finding unconventional resources has become a challenge for small and medium breeders to feed their livestock. The objective of this study is to determine whether the use of marine plant debris, Posidonia oceanica, as total or partial replacement of oat hay in alpine goat diets will affect or not milk yield and quality. The sea grass was characterized according to the sampling site. Chemical and phytochemical analysis revealed significantly higher levels of dry matter, minerals, total polyphenols and carotenoids in P. oceanica on banquettes than in floating Posidonia. The condensed tannin content was almost the same for both sites. Partial or total replacement of oat hay by P. oceanica in alpine goat rations significantly increased milk production and milk fat content, while somatic cell count decreased significantly. In addition, P. oceanica significantly enhanced milk biochemical composition by increasing flavonoid and total phenol contents. However, protein, lactose and freezing point parameters were not affected. Sensory analysis revealed substantial improvement in the organoleptic quality of P. oceanica fed goats’ milk compared to the other group, which was highly appreciated by most of the panelists. The seagrass P. ocanica could therefore be a safe solution to improve fodder availability for small and medium breeders, reduce production costs and increase milk market value. © 2021 Friends Science Publishers

Influence of Abiotic Factors on Walking Behavior of Hunting Billbugs (Coleoptera: Curculionidae).

The hunting billbug, Sphenophorus venatus vestitus Chittenden, is an important insect pest of warm-season turfgrass. Larvae and adult S. venatus vestitus feed on turfgrass and affect normal grass growth and development. In sod farms and golf courses, management sprays are typically confined to affected areas because of the high insecticide and application costs. Understanding the walking behavior of S. venatus vestitus adults would help us to refine management tactics. Thus, the objective of this study was to determine the influence of abiotic factors on the walking behavior of adult S. venatus vestitus. A series of laboratory, semifield, and field assays were conducted in 2019 and 2020. For the laboratory assays, field-collected S. venatus vestitus adults were acclimated at 15, 18, 21, 28, and 32°C for 24 h, and the distances walked by these pre-acclimated adults were measured on sand and filter paper substrates using Noldus EthoVision XT software. For the semifield assays, the total and net distances walked by pre-acclimated adults were measured on a paved indoor surface. Sphenophorus venatus vestitus males and females moved farther when the temperature increased from 15 to 28°C in the laboratory and semifield assays. For the field assays, field-collected S. venatus vestitus adults were not acclimated. The total and net distances walked by the adults were documented on a paved surface. Increases in temperature and relative humidity did not affect the distance moved by adults, but an increase in wind speed reduced the distance moved.

Nitrogen‐Induced Changes in Carbon Fluxes Are Modulated by Water Availability in a Temperate Grassland

AbstractCarbon fluxes of grasslands could be deeply affected by nitrogen (N) enrichment, however, it remains unclear how other factors modulate the N‐induced changes in carbon fluxes and the underlying mechanisms. In this study, we quantified the effects of N addition on net ecosystem CO2 exchange (NEE) and its two components (gross primary productivity (GPP) and ecosystem respiration (Re)), and how water availability modulates these effects in a temperate grassland, China. We found that N enrichment significantly increased foliar N content of grasses (related to a higher photosynthetic rate), leading to higher aboveground biomass (AGB) and therefore vegetation cover, implying higher photosynthetic leaf area. AGB was further enhanced as root: shoot ratio tended to be reduced by N‐addition. Consequently, GPP was significantly stimulated by N‐addition. Re insignificantly increased with N addition. With N‐induced larger increase of GPP and little change of Re, NEE, which is negative when an ecosystem sequestrates more carbon than it releases to the atmosphere, became more negative. Due to a significant sharper versus a relatively gentler N‐induced increase with increasing water availability for GPP and Re, respectively, the N‐induced reduction of NEE distinctly increased linearly with increasing water availability. The enlarged N‐induced stimulation of GPP and thus NEE at ample water conditions is mainly associated with luxuriant growth of grasses who got extra increase of foliar N content, AGB, and decrease of root: shoot ratio. Our findings facilitate an advanced understanding of carbon fluxes responding to climate change and provide knowledge for management in grassland ecosystems.

Effect of elevated temperature on growth and glyphosate susceptibility of Chloris truncata R.Br., Sonchus oleraceus L., and Conyza bonariensis (L.) Cronq.

ABSTRACT A temperature-controlled glasshouse study was conducted to evaluate the influence of elevated temperature (eT – 34/24 ± 2°C) on the growth and glyphosate susceptibility of windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronquist]; and to determine the morpho-physiological factors involved in differential glyphosate tolerance under eT. Results showed that elevation of temperature from ambient temperature (aT – 28/20 ± 2°C) to 34/24 ± 2°C increased growth and biomass production of C. truncata. In contrast, eT suppressed growth of S. oleraceus and C. bonariensis, resulting in fewer, thicker, and smaller leaves with reduced stomatal conductivity and less total plant biomass. In terms of herbicide susceptibility, the responses to glyphosate under different temperature regimes were species- and rate-specific. Slight variations in glyphosate susceptibility were observed when sprayed at sub-lethal rates at eT. Under eT, C. truncata, S. oleraceus, and C. bonariensis required 1.5, 2.0-, and 1.6-times higher glyphosate rates, respectively, to suppress biomass by 50% compared with plants grown at aT. Depending upon the species and glyphosate rate, differences in leaf characteristics (i.e. leaf chlorophyll content, leaf area/thickness, and stomatal conductance) could have promoted or delayed glyphosate activity under eT over the period, especially at sub-lethal rates. Overall, the glyphosate efficacy was unaffected since herbicide within the recommended rates completely controlled all tested weed species under both temperatures. Nomenclature: windmill grass, Chloris truncata R.Br., Common sowthistle, Sonchus oleraceus L., Flaxleaf fleabane, Conyza bonariensis (L.) Cronquist

Biomechanical properties of the growing and decaying roots of Cynodon dactylon

Root growth and decay may affect root reinforcement to soil erosion and stability. We measured the effects of growth and decay on the tensile strength of Cynodon dactylon roots considering different causes of mortality common to agricultural land conversion (i.e. burning and herbicide application). We applied three treatments to C. dactylon grass: (i) growth duration (60, 120 and 180 days), (ii) decay duration after burning (30, 60, 120, 180 and 360 days) and (iii) decay duration after herbicide application (15, 30 and 60 days). The diameter, tensile strength and cellulose and lignin contents of root samples (n = 303) in different treatments were measured. Tensile strength–diameter relations followed a negative power law regardless of treatment (R2 > 0.6). The increase in median tensile strength values due to grass growth was consistent with the increase in cellulose and lignin contents. Root decay by herbicide application caused significantly greater and faster reduction in tensile strength than burning treatment because of the faster reduction of cellulose and lignin contents. Root decay due to different causes of plant mortality can increase susceptibility to erosion and slope instability during the conversion of agricultural land. Measures on slope safety and erosion are vital when using herbicides for weed clearance in farmlands due to the faster deterioration of root chemical composition and root tensile strength (compared with burning).

Influence of Temperature Conditions during Growth on Bioactive Compounds and Antioxidant Potential of Wheat and Barley Grasses.

Wheat and barley grasses are freshly sprouted leaves of wheat and barley seeds, and are rich sources of phytochemicals. This study was conducted to investigate the effects of day and night temperatures on the growth, bioactive compounds, and antioxidant potential of wheat and barley grasses. Briefly, each grass was cropped in an organic growing medium at 10/5 °C, 20/15 °C, and 30/25 °C (day/night temperature) in a growth chamber by maintaining specific light (12/12 h light/dark; light intensity 150 µmol photons m−2 s−1) and humidity (60%) conditions for 8 days. The highest growth parameters (height, weight, and yield) were observed at the 20/15 °C growth conditions in both types of grass. Conversely, the lowest growth parameters were observed at 10/5 °C. However, the low growth temperature of 10/5 °C resulted in increased levels of bioactive compounds (total phenol, total flavonoid, and total vitamin C), antioxidant activities (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid and 2,2-Diphenyl-1-picrylhydrazyl radical-scavenging activity)), and antioxidant enzymes (guaiacol peroxidase activity, catalase activity, and glutathione reductase) in both types of grass. Therefore, proper temperature growth conditions of wheat and barley grasses may be a convenient and efficient method to increase bioactive compounds and antioxidant potential in our diet to exploit the related health benefits.

Simulating grazing beef and sheep systems

CONTEXTRuminant livestock make an important contribution to global food security by converting feed that is unsuitable for human consumption into high value food protein, demand for which is currently increasing at an unprecedented rate because of increasing global population and income levels. Factors affecting production efficiency, product quality, and consumer acceptability, such as animal fertility, health and welfare, will ultimately define the sustainability of ruminant production systems. These more complex systems can be developed and analysed by using models that can predict system responses to environment and management. OBJECTIVEWe present a framework that dynamically models, using a process-based and mechanistic approach, animal and grass growth, nutrient cycling and water redistribution in a soil profile taking into account the effects of animal genotype, climate, feed quality and quantity on livestock production, greenhouse gas emissions, water use and quality, and nutrient cycling in a grazing system. METHODSA component to estimate ruminant animal growth was developed and integrated with the existing components of the SPACSYS model. Intake of herbage and/or concentrates and partitioning of the energy and protein contained in consumed herbage and/or concentrates were simulated in the component. Simulated animal growth was validated using liveweight data from over 200 finishing beef cattle and 900 lambs collected from the North Wyke Farm Platform (NWFP) in southwest England, UK, between 2011 and 2018. Annual nitrous oxide (N2O), ammonia, methane and carbon dioxide emissions from individual fields were simulated based on previous validated parameters. RESULTS AND CONCLUSIONSA series of statistical indicators demonstrated that the model could simulate liveweight gain of beef cattle and lamb. Simulated nitrogen (N) cycling estimated N input of 190 to 260 kg ha−1, of which 37–61% was removed from the fields either as silage or animal intake, 15–26% was lost through surface runoff or lateral drainage and 1.14% was emitted to the atmosphere as N2O. About 13% of the manure N applied to the NWFP and excreta N deposited at grazing was lost via ammonia volatilisation. SIGNIFICANCEThe extended model has the potential to investigate the responses of the system on and consequences of a range of agronomic management and grazing strategies. However, modelling of multi-species swards needs to be validated including the dynamics of individual species in the swards, preferential selection by grazing animals and the impact on animal growth and nutrient flows.

Plant Community Diversity at Two Reclaimed Mine Tailing Storage Facilities in Québec, Canada

Mining activities generate residues during the ore concentration process. These wastes are placed into large tailing storage facilities, and upon mine closure, these tailings must be reclaimed. This study aimed to determine how different reclamation methods, involving combinations of planted boreal woody species and organic amendments application (paper mill sludge biosolids, chicken manure, and topsoil) affected plant community diversity at two tailing storage facilities in Québec, Canada. We recorded the composition of the plant communities using the percent cover of plant species within 1 m × 1 m quadrats. At the Niobec mine site, paper mill sludge mixed with topsoil enhanced total plant cover was compared with the use of topsoil only; the former amendment, however, reduced evenness (J′) and diversity (1−D) due to the increased growth of grasses and invasive forbs. At the Mont-Wright site, plots having received paper mill sludge mixed with a “Norco” treatment (a mixture of chicken manure, hay, and grass seeds) produced the highest total plant cover. The Norco treatment mixed with topsoil and the single application of topsoil and biosolids produced the highest evenness (J′) and diversity (1−D). Overall, organic amendment applications promoted vegetation cover on tailings and contributed to the colonization of diverse plant communities.

Assessing Competitiveness of Fine Fescues (Festuca L. spp.) and Tall Fescue (Schedonorus arundinaceous (Schreb.) Dumort) Established with White Clover (Trifolium repens L., WC), Daisy (Bellis perennis L.) and Yarrow (Achillea millefolium L.)

Regulatory restrictions on herbicide use for managing turfgrass weeds has prompted the search for alternative control strategies. Fescue (Festuca) species were identified for their potential to interfere with growth of annual and perennial weeds. In a study conducted in 2018 and 2019, six fescue cultivars were tested from five different species for interference with the growth of three common turfgrass weeds: white clover (Trifolium repens L., WC), daisy (Bellis perennis L.) and yarrow (Achillea millefolium L.). Fine (Festuca L. spp.) and tall fescues (Schedonorus arundinaceus (Schreb.) Dumort.) were sown and grown in a field trial for 14 days before overseeding with different weeds. vigor and visual quality of grasses, weed cover, and vegetation cover was recorded regularly for 84 days. Differences in mean temperatures and precipitation between the two years of the study resulted in differences in growth of grasses and weeds, as well as in the extent of weed interference of fescue cultivars. Cultivars Musica (F. rubra L. ssp. commutata Gaudin) and Barpearl (F. rubra L. ssp. littoralis) were least affected by weed growth during both years, but there was overlap with other cultivars for the measured parameters. Melyane (tall fescue) was deemed unsuitable for natural weed suppression because growth and vigor declined after first mowing, ultimately leading to unacceptable visual quality. Turfgrass visual scores were moderately negatively correlated to weed cover in both years. Future research should focus on F. rubra L. ssp. rubra Gaudin and F. rubra L. ssp. littoralis subspecies and identify the mechanisms used to interfere with weed growth.

Evaluation of cereal forage grasses and forages from them according to the content of protein insoluble in acid detergent

The nitrogen content was determined in acid-detergent fiber (ADF) isolated from awnless rump, meadow fescue and meadow timothy, depending on the phase of their the same phases are for silage and haylage. Samples for analyzes were dried at a temperature of 60-65 ° C. As the grasses grew, an increase in the content of CDC in them was observed, which was also accompanied by an increase in ADF from the phase of entering the tube to flowering in timothy grass - from 1.18 to 1.36%, in meadow fescue - from 0.96 to 1.58 5%. When preserving grasses, an increase in the content of CDC is observed in all phases of their growth as compared to the original grass, but the mass fraction of ADF in the dry matter of silage and haylage was no more than in the original grass. If the technology of harvesting silage and haylage is observed, the level of thermal damage to these forages does not increase. With the growth of grasses from the vegetative phase to flowering, the content of SP in grasses and forages from them decreases, while the proportion of ADF in it increases. The inverse relationship between these indicators had correlation coefficients of 0.83, 0.88 and 0.92 for grasses, silage and haylage, respectively. The need to harvest them in earlier phases of growth is noted.

Options and rationale for regional property‐based kangaroo production

SummaryThe larger kangaroos (Macropus giganteus, M. fuliginosus and Osphranter rufus) are widely distributed and have a national population which fluctuates in response to changes in grass growth and trends to 40 million. Most are outside parks and reserves and, on pastoral properties, particularly on the rangelands of southern Australia. High numbers compromise regenerative agriculture, pasture conservation, revegetation and stewardship programmes, and can have significant financial impacts on landholders by lowering livestock production and damaging sustainability. Some smaller macropods, wallabies and pademelons, also have a similar effect, especially in Tasmania and on other smaller Australian Islands where foxes are absent. Paradoxically, kangaroos have a wide range of potentially valuable production attributes and are unique, which should be a global comparative advantage. The kangaroo industry is established with a small domestic and international market, although demand has been falling in recent years. Non‐commercial culling is rising, which results in millions of carcasses being wasted and left to decompose in the field. Indigenous communities abhor such waste and its cultural implications. A stronger kangaroo industry would be a better solution to managing overabundant kangaroos than pest culling and exclusion fences. Because kangaroos move from property to property, populations need to be managed on a regional basis through ‘regional property‐based kangaroo production’. A form of proprietorship over this mobile resource would encourage landholders to play a role in creating greater demand for kangaroo products. They would have an incentive to raise the value of kangaroos. Through innovative harvesting, they could deliver high‐quality, environmentally branded, accurately described, gourmet, differentiated products integrated with other livestock industries. They could establish cooperatives and embark on promoting regional kangaroo products. Policy improvements are needed to achieve these production systems. Doing so would diversify their enterprises, convert a liability already on their properties into an asset, create employment, enhance rural economic resilience, and improve animal welfare and conservation outcomes while earning them carbon credits. These opportunities become even more profound as climate change progresses.

Growth stimulators and mineral fertilizers influence on Sudan grass growth, development and productivity

The article considers the results of research on the influence of seeding rates, fertilizers and growth stimulator on the development and productivity of the Sudan grass of the Julia variety in the conditions of chestnut soils of the Volgograd region. In the field two-factor experiment, we studied: factor A - the three seeding rates 1.0, 1.5 and 2.0 million germinating seeds per hectare; factor B - fertilizers and growth promoters: 1. Control without fertilizers; 2. N60 P60 K45 + N30; 3. Growth stimulator Raikat Start; 4. N60 P60 K45 + Raikat Start + N30. The use of mineral fertilizers increased the leaf surface area by 0.3-0.5 thousand m2/ha, the use of growth stimulators increased the leaf surface area by 0.1-0.2 thousand m2/ha, the combined use of mineral fertilizers and growth stimulators increased the leaf surface area by 0.9-1.2 thousand m2/ha. It was found that the highest yield of green mass of Sudan grass, 28.6 t/ha, was formed on the variant with a seeding norm of 1.5 million tons of germinating seeds per ha with the complex application of mineral fertilizers and the growth stimulator Raikat Start.

Soil Water Availability Changes in Amount and Timing Favor the Growth and Competitiveness of Grass Than a Co-dominant Legume in Their Mixtures.

The grasslands on the semi-arid Loess Plateau of China are expected to be particularly responsive to the size and frequency changes of extreme precipitation events because their ecological processes are largely driven by distinct soil moisture pulses. However, the plant growth and competitiveness of co-dominant species in response to the changes in the amount and timing of soil water are still unclear. Thus, two co-dominant species, Bothriochloa ischaemum and Lespedeza davurica, were grown in seven mixture ratios under three watering regimes [80 ± 5% pot soil capacity (FC) (high watering), 60 ± 5% FC (moderate watering), and 40 ± 5% FC (low watering)] in a pot experiment. The soil water contents were rapidly improved from low to moderate water and from moderate to high water, respectively, at the heading, flowering, and maturity stages of B. ischaemum, and were maintained until the end of the growing season of each species. The biomass production of both species increased significantly with the increased soil water contents, particularly at the heading and flowering periods, with a more pronounced increase in B. ischaemum in the mixtures. The root/shoot ratio of both species was decreased when the soil water availability increased at the heading or flowering periods. The total biomass production, water use efficiency (WUE), and relative yield total (RYT) increased gradually with the increase of B. ischaemum in the mixtures. The relative competition intensity was below zero in B. ischaemum, and above zero in L. davurica. The competitive balance index calculated for B. ischaemum was increased with the increase of the soil water contents. Bothriochloa ischaemum responded more positively to the periodical increase in soil water availability than L. davurica, indicating that the abundance of B. ischaemum could increase in relatively wet seasons or plenty-rainfall periods. In addition, the mixture ratio of 10:2 (B. ischaemum to L. davurica) was the most compatible combination for the improved biomass production, WUE, and RYTs across all soil water treatments.

APSIM model performance in simulating Piatã palisade grass growth and soil water in different positions of a silvopastoral system with eucalyptus

CONTEXTSilvopastoral systems aim to be more sustainable than conventional systems, increasing total productivity, diversifying agricultural production, and improving resource use efficiency. However, very few studies were performed to adapt crop models to simulate these systems. OBJECTIVEThis study investigates the current capacity of the APSIM Next Generation model to estimate Piatã palisadegrass growth and soil water in different positions in a silvopastoral system with eucalyptus by looking at the impact of modelling belowground and aboveground competition separately. METHODSA field experiment was conducted from December 2014 to January 2016 in a silvopastoral system with eucalyptus trees arranged in single rows, in East-West orientation, with 15 m between rows and 2 m between trees in the rows. This experiment was conducted under grazing management and rainfed conditions, during 11 growth cycles, with pasture variables, soil moisture and microclimatic conditions assessed at four distances from the eucalyptus north row (0.00 m, 3.75 m, 7.50 m and 11.25 m). APSIM testing was performed in two ways: focusing on belowground competition for soil water and nitrogen, using a multi-root-zone approach, and focusing on competition for solar radiation, using the measured data of solar radiation at each position. RESULTS AND CONCLUSIONSThe APSIM-Tropical Pasture model was effective in simulating pasture growth when only competition for solar radiation was considered (R2 from 0.75 to 0.86, Agreement index (d) from 0.88 to 0.96, and Nash-Sutcliffe efficiency (NSE) between 0.32 and 0.85). These simulations are promising taking into account the difficulties to simulate pasture growth in silvopastoral systems with grazing; however, in systems with strong belowground competition for soil water and nutrients, this approach has strong limitations. Simulations of pasture growth were not as effective when using the multi-root-zone approach (R2 between 0.57 and 0.87, d between 0.53 and 0.74, and NSE from −5.32 to −1.20), despite reasonable simulations of soil water for the positions between the tree rows (R2 between 0.70 and 0.80, d from 0.91 to 0.94, and NSE between 0.60 and 0.77). In view of these results, improvements should be performed in APSIM to better simulate silvopastoral systems, mainly for solar radiation transmission and tree roots growth and distribution. SIGNIFICANCEThis study allowed identifying the key drivers of competition within the studied environment and to inform where the main efforts should be targeted in building a more effective model for silvopastoral systems. This is important to help model development teams in organising and optimising their efforts.

Testing Combined Effect of Amendments and Inoculation with Bacteria for Improving Phytostabilisation of Smelter Waste Extremely Contaminated with Trace Elements

Smelter waste deposits pose environmental and health threats and require remediation actions. Phytostabilisation techniques, based on soil amendments, help to establish plant cover and limit the secondary emission of potentially toxic trace elements. However, methods to optimize their effectiveness are needed. The application of bacterial inoculants in combination with soil amendments in the remediation of soils and wastes contaminated with metals still has not been extensively tested. Therefore, the aim of this study was to determine the effectiveness of indigenous (Streptomyces sp., Pseudomonas sp.) and foreign (Streptomyces costaricanus) strains of bacteria in supporting grass growth on extremely contaminated waste slag. They were applied alone and in combination with compost mixed with phosphate fertilizer or iron oxide. The tested strains improved plant growth and increased plant availability of phosphorus. The interaction of the soil amendments and some bacterial strains also stimulated a decrease in the extractability of metals, likely through the phosphate-induced precipitation of lead. Our data show that the effectiveness of soil amendments in the phytostabilisation of heavily polluted smelter deposits can be enhanced by plant growth-promoting bacteria (PGPB).