High Soil Moisture Conditions Research Articles

Emissions of atmospherically reactive gases nitrous acid and nitric oxide from Arctic permafrost peatlands

Soils are important sources of nitric oxide (NO) and nitrous acid (HONO) in the atmosphere. These nitrogen (N)-containing gases play a crucial role in atmospheric chemistry and climate at different scales because of reactions modulated by NO and hydroxyl radicals (OH), which are formed via HONO photolysis. Northern permafrost soils have so far remained unexplored for HONO and NO emissions despite their high N stocks, capacity to emit nitrous oxide (N2O), and enhancing mineral N turnover due to warming and permafrost thawing. Here, we report the first HONO and NO emissions from high-latitude soils based on measurements of permafrost-affected subarctic peatlands. We show large HONO (0.1–2.4 µg N m−2h−1) and NO (0.4–59.3 µg N m−2h−1) emissions from unvegetated peat surfaces, rich with mineral N, compared to low emissions (⩽0.2 µg N m−2h−1 for both gases) from adjacent vegetated surfaces (experiments with intact peat cores). We observed HONO production under highly variable soil moisture conditions from dry to wet. However, based on complementary slurry experiments, HONO production was strongly favored by high soil moisture and anoxic conditions. We suggest urgent examination of other Arctic landscapes for HONO and NO emissions to better constrain the role of these reactive N gases in Arctic atmospheric chemistry.

Effects of Shade and Planting Methods on the Growth of Heracleum moellendorffii and Adenophora divaricata in Different Soil Moisture and Nutrient Conditions.

In this study, the interacting effects of shade and planting methods on the growth and competitive ability of two understory plants Heracleum moellendorffii Hance and Adenophora divaricata Franch. & Sav. were investigated under different soil moisture and nutrient conditions. One-year-old seedlings were subjected to different light levels (0%, 35%, and 55% shade) and planting methods (monoculture and mixed) under contrasting soil moisture (1.2 L/m2 and 2.3 L/m2 of water) and soil nutrient conditions (unfertilized and fertilized). Here, shading significantly improved the height growth of H. moellendorffii (10–20 cm increase) in unfertilized and fertilized plots and at high soil moisture conditions. Contrarily, A. divaricata seedlings planted singly at full sunlight yielded a higher aboveground biomass growth (8–17 g plant−1), compared with those shaded and intercropped seedlings (0.9–3.9 g plant−1). The increased competitiveness of H. moellendorffii suppressed the growth of A. divaricata across different light conditions when planted together. The amount of light, soil moisture, and nutrients and their interactions significantly affected the growth of the seedlings, resulting in asymmetric interspecific competition between the two species. Results provide us with a better understanding of the environmental factors affecting plant growth for forest farming in the understory.

Populations of Heracleum sosnowskyi and H. mantegazzianum (Apiaceae) in Kyiv (Ukraine)

Abstract In connection with the increasing negative impact of invasive alien species on biodiversity and the environment in general, their research, as well as throughout the world, is relevant. The distribution of the Heracleum sosnowskyi and H. mantegazzianum of the secondary range on the example of the Kyiv agglomeration is investigated in the work. In our study we aimed to evaluate the possibility of spontaneous spread of giant hogweeds in the secondary range, adaptation of the species to the new conditions of the environment that favor to control of these species’ expansion and reduce the threat to the urban ecosystems and citizens’ health. We hypothesise that in the secondary range H. sosnowskyi and H. mantegazzianum settle sites with relatively high temperature (Tr), lightening (Lc), and soil moisture conditions similar to that in their natural range. 17 populations and four localities (sites) of H. sosnowskyi and H. mantegazzianum were studied. They were found within forest, meadow, riverine and ruderal plant communities. It is indicated that the advent species fully adapted to the conditions of the environment. The difference by ecological indicators Lc2 and Tm1 is pointed out. According to the results of our research, for the area of Kyiv urban agglomeration the growth of H. sosnowskyi and H. mantegazzianum is indicated in the plants communities of six classes. They spread most in ruderal plant communities of the: Robinietea, Artemisietea, Epilobietea classes. The studied species belong to invasive plant species in Ukraine and are characterized by extremely high effect on the environment and high invasive potential.

English

Studies have shown arbuscular mycorrhizal fungi (AMF) enhance phosphorus (P) uptake and drought tolerance in maize (Zea mays L.) grown in semiarid soils. However, little is known regarding the contribution of AMF to maize treated with different levels of phosphorus and grown in different soil moisture levels. This study was conducted to determine the effects of AMF (Glomus fasciculatum) inoculation on growth and P uptake of maize treated with different levels of soil P and soil moisture. Different P levels (0, 50, and 100 kg P ha-1) were applied on maize grown in soils with and without mycorrhizal fungi, and at different moisture levels producing -0.05, -0.4, -0.8, and -1.5 MPa of drought stress. Increasing P rates significantly (p < 0.05) reduced mycorrhizal colonization. Mycorrhizal colonization was higher under moderate than under lower soil moisture levels. Drought stress × soil P content × AMF inoculation interaction had significant (p < 0.05) effect on maize shoot and root dry weight and tissue P concentration. Overall, results of this study suggest that mycorrhizal inoculation enhances P uptake and maximizes maize biomass under low, moderate, and high soil moisture conditions without P applications. Except for the lowest soil moisture level (-1.5 MPa), mycorrhizal plants produced higher biomass, with greater tissue P content than nonmycorrhizal plants at all soil P and soil moisture levels. These results indicate that establishing efficacious AMF with maize could be an efficient alternative for growers than relying on P fertilizer application and its associated costs and environmental concerns. Keywords: Arbuscular Mycorrhiza Fungi, Drought Tolerance, Phosphorus Levels, Maize Plants.

The multifactorial assessment of the Zn impact on high and low temperature stress towards wheat seedling growth under diverse moisture conditions (optimal and wet) in three soils

Anthropogenic activities leading to chemical contamination of soil and global climate change may increase the level of stress for plants. Recent decades studies (mainly two-factors) have reported that the ecotoxicity of soil contaminants could be modified by climate factors. To date, little is known about: the combined climate-chemical stress on plants; the interaction of chemicals with high soil moisture conditions; the impact of soil properties on the combined climate-chemical stress and questions regarding the response of organisms to combined effect of all key factors influencing the ecotoxicity of chemicals under field conditions remain unanswered. Our study sought to fill the knowledge gap on the multifactorial interaction of four main factors encounter in polluted areas (soil chemical contamination: heavy metal (Zn); temperature: 10, 23, 35 °C, moisture: 55, 80%WHC; soil properties). The assessment of combined effect of multiple stressors based on the multiple ANCOVA model (n = 108; adjusted R2 = 0.68) and calculated indicators showed: 1) all studied factors significantly interacted and influenced the phytotoxic effect of Zn; 2) Zn modified the plant response to temperature stress depending on moisture conditions and soil properties. This study improves methods for assessing the hazardous effects of soil chemical contamination in the real environment.

ТЕОРЕТИЧЕСКИЕ ПРЕДПОСЫЛКИ ПОВЫШЕНИЯ СЕПАРИРУЮЩЕЙ СИСТЕМЫ МАШИНЫ ДЛЯ УБОРКИ КОРНЕПЛОДОВ ТЕПЛОВОЙ ЭНЕРГИЕЙ СИСТЕМЫ ОТРАБОТАВШИХ ГАЗОВ

To improve the quality indicators of harvesting root crops in conditions of high humidity, it is proposed to mount a separating device on the combine, which ensures the separation of root crops from soil and plant impurities with simultaneous blowing of their surface with hot exhaust gases from the power plant of the harvesting machine. Heat losses with exhaust gases (Q_G = 51960 J/s) exceed its amount equivalent to useful work (Q_A = 50900 J/s), therefore, it is necessary to ensure efficient use of the heat released into the atmosphere to increase the efficiency of the energy component of harvesting root crops and potatoes in conditions of high soil moisture. The aim of the study is to theoretically substantiate the improvement of the quality of separation of sugar beet root crops in conditions of high humidity with the use of blowing the working surface of the cleaning devices with exhaust gases from the power plant of the self-propelled harvester in the separation system of the harvester. The subject of research is the separation system of a combine harvester, represented by a cleaning star with installed deflectors for blowing the working surface. The condition for the uniform distribution of a heap of commercial products over the separating working surface is determined and theoretical dependences of the angular velocity v_EL and the rotational speed n_SP of the separating star on the forward speed of the sweeper and the radius of the separating star with uniform blowing of exhaust gases on the working surface are obtained

Relationships among carbon isotope composition, growth, and foliar nitrogen in soybean

ABSTRACT Interactions between carbon isotope composition (δ13C), foliar nitrogen concentration (foliar N), and biomass accumulation (growth) merit further investigation in soybean (Glycine max (L.) Merr.) and other species as these metrics may be valuable for assessing moisture stress and for screening of drought-resistant varieties. To this end, we examined the response of six soybean genotypes to water-deficit stress in a greenhouse study. Two treatments were imposed: low soil moisture (5–10% volumetric water content) and high soil moisture (30–38% volumetric water content). Above-ground biomass accumulation, foliar N, and δ13C were measured at the end of the experiment. Leaf water potential and midday gas exchange (net assimilation, stomatal conductance, and transpiration) were measured multiple times throughout the experiment. All measurements were affected by water-deficit stress. Significant, but weak, positive relationships were found between δ13C and biomass accumulation in both soil moisture treatments. Foliar N was significantly, but weakly, correlated to growth in the high soil-moisture treatment, but not in the low soil-moisture treatment. The data suggest that selection for genotypes with higher δ13C values could result in improved biomass accumulation. The relationship between foliar N and δ13C was negative under high soil-moisture conditions and positive under low soil-moisture conditions. The relationships between δ13C and foliar N could be a highly informative metric to help understand the effects of water-deficit stress and may further indicate whether water or nitrogen acquisition is limiting in a specific environment, which should help in breeding improved soybean cultivars.

Environmental effects on efficacy of herbicides for postemergence goosegrass (Eleusine indica) control

Experiments were conducted to understand environmental effects on efficacy of herbicides used to control goosegrass (Eleusine indica L. Gaertn.). Herbicides were applied to goosegrass maintained at soil moisture contents (VMC) of < 12%, 12 to 20%, or > 20%. Herbicides included fenoxaprop-p-ethyl (140 g ha−1), topramezone (25 g ha−1), foramsulfuron (44 g ha−1), 2,4-D + dicamba + MCPP + carfentrazone (860 + 80 + 270 + 28 g ha−1), and thiencarbazone-methyl + foramsulfuron + halosulfuron-methyl (22 + 45 + 69 g ha−1). Goosegrass control increased as VMC increased. Vapor pressure deficit (VPD) and air temperature were manipulated to determine effects of evaporative demand on foramsulfuron. Effects of soil drying were also studied following foramsulfuron application. Reductions in transpiration rate (TR) and leaf area were greatest with foramsulfuron applications to goosegrass in silt-loam under high evaporative demand (3 kPa VPD, 38 °C). Foramsulfuron had no effect on goosegrass in silica-sand regardless of evaporative demand. TR dropped to 0.2 mmh−1 within eight days after application to goosegrass in silt-loam compared to 18 days in silica-sand. Overall, foramsulfuron efficacy on goosegrass was maximized under conditions of high soil moisture and evaporative demand, and may be reduced in sandy soils that hold less water.

Genetic Diversity of Hydro Priming Effects on Rice Seed Emergence and Subsequent Growth under Different Moisture Conditions.

Seed priming refers to seed enhancement methods that stimulate seed metabolism. This study evaluated the genetic diversity of hydro priming efficacy in 27 different genotypes of rice under dry to wet soil moisture conditions. The genotypes included 21 genotypes of Oryza sativa, five genotypes of Oryza glaberrima, and one genotype of NERICA (New Rice for Africa). The treated rice seeds were sown in plastic boxes under four soil moisture conditions (5%, 10%, 15%, and 20% (w/w)). The genotypes were categorized into six groups based on growth parameters using hierarchical cluster analysis. Furthermore, emergence properties were investigated by using principal component analysis based on the mean emergence time of control and primed seeds. Seed priming enhanced growth performance under the moderate dry conditions of 10% and 15% soil moisture. Meanwhile, priming efficacy was low in water stress conditions of 5% and 20% soil moisture. There were wide-ranging genotypic differences of priming efficacy under 20% soil moisture condition. Our findings indicate that the anaerobic-tolerant genotypes tend to exhibit priming efficacy under high soil moisture conditions. Furthermore, one group included all upland genotypes of Oryza sativa. This group originally adapted to 10% and 15% of dry conditions, and seed priming improved their features greatly.

Light availability controls rhizosphere priming effect of temperate forest trees

Plant can accelerate or slow down the soil organic carbon (SOC) decomposition by the rhizosphere priming effect (RPE). In forest ecosystems, the change of light availability due to canopy gap formation strongly influences growth of young trees and rhizosphere microbial activities in soil. However, the responses of RPE of forest young trees to light availability and its driving mechanisms remain elusive. We investigated the effects of about 60% shading on RPE of two dominant forest tree species (i.e., shade-tolerant species maple and photophilic species oak) over the four months of the growing season using the 13C natural tracer approach. Our results showed that the effects of shading on RPE were not dependent on the tree species. Under natural light, negative RPE on SOC decomposition prevailed during the experimental period (The loss of soil carbon via CO2 was 31.9% lower in planted soil than in unplanted soil). RPE under shading was 71.1% more positive than that under natural light. Under natural light mineral nitrogen (N) content and microbial biomass nitrogen (MBN) were lower in planted soil than in unplanted soil, suggesting that N competition between roots and microbes due to N uptake by plants may be responsible for the negative RPE. The results of two-way ANOVA showed that although shading only had the tendency of increasing MBC, it significantly increased MBN and C-acquiring enzyme activities. These changes contributed to more positive RPE under shading. The main reason for this result may be the alleviation of root-microbes competition, the higher demand of available substrates from SOC by microbes and the higher soil moisture conditions under shading. Our study also highlights the importance of soil microbial biomass and enzyme activity when studying the mechanisms of the responses of RPE to shading or other environmental changes.

Timeliness and traffic intensity in spring fieldwork in Norway

Future increase in precipitation in Scandinavia may exacerbate the dilemma of spring fieldwork that farmers have, concerning topsoil compaction versus delayed sowing on autumn ploughed soil. The former may lead to soil physical degradation, while the latter may lead to a shorter growing season, both with consequential loss of cereal yield potential. In order to enable farmers to adapt their spring fieldwork to climate change, research needs to include seedbed preparation at higher soil moisture conditions. A split-plot experiment in southeastern Norway in 2014–2017 explored the effects of timing (early, medium, late) and traffic intensity (zero, one, two or three additional wheelings) of spring fieldwork on soil physics and yield. Early spring fieldwork in the unfavourably wet conditions of 2016 gave rise to larger and stronger aggregates, higher penetration resistance, changed pore characteristics and reduced yields. Increased penetration resistance persisted until autumn. The small effect of traffic intensity was explained by location, soil type and intensity range involved. In this context of spring fieldwork timeliness, the proportion of 2–6 mm aggregates and penetration resistance were the properties most strongly correlated with other soil physical properties and cereal yield.

Coffee and shade trees show complementary use of soil water in a traditional agroforestry ecosystem

Abstract. Globally, coffee has become one of the most sensitive commercial crops, being affected by climate change. Arabica coffee (Coffea arabica) grows in traditionally shaded agroforestry systems in tropical regions and accounts for ∼70 % of coffee production worldwide. Nevertheless, the interaction between plant and soil water sources in these coffee plantations remains poorly understood. To investigate the functional response of dominant shade tree species and coffee (C. arabica var. typica) plants to different soil water availability conditions, we conducted a study during near-normal and more pronounced dry seasons (2014 and 2017, respectively) and a wet season (2017) in a traditional coffee plantation in central Veracruz, Mexico. For the different periods, we specifically investigated the variations in water sources and root water uptake via MixSIAR mixing models that use δ18O and δ2H stable isotope composition of rainfall, plant xylem and soil water. To further increase our mechanistic understanding of root activity, the distribution of below-ground biomass and soil macronutrients was also examined and considered in the model as prior information. Results showed that, over the course of the two investigated dry seasons, all shade tree species (Lonchocarpus guatemalensis, Inga vera and Trema micrantha) relied, on average, on water sources from intermediate (&gt;15 to 30 cm depth: 58± 18 % SD) and deep soil layers (&gt;30 to 120 cm depth: 34±21 %), while coffee plants used much shallower water sources (&lt;5 cm depth: 42±37 % and 5–15 cm depth: 52±35 %). In addition, in these same periods, coffee water uptake was influenced by antecedent precipitation, whereas trees showed little sensitiveness to antecedent wetness. Our findings also showed that during the wet season coffee plants substantially increased the use of near-surface water (+56 % from &lt;5 cm depth), while shade trees extended the water acquisition to much shallower soil layers (+19 % from &lt;15 cm depth) in comparison to drier periods. Despite the plasticity in root water uptake observed between canopy trees and coffee plants, a complementary use of soil water prevailed during the dry and wet seasons investigated. However, more variability in plant water sources was observed among species in the rainy season when higher soil moisture conditions were present and water stress was largely absent.

Reduction of soil layer losses when harvesting sugar beet in the conditions of the central black earth region

When cultivating sugar beets, harvesting is one of the most labor-intensive operations. But in terms of quality and operational and technological performance, the machines used do not meet modern agrotechnical requirements, especially in conditions of high soil moisture (25 - 29%). With an increase in soil moisture, its adhesion to the working surfaces of the digging organs and the heap cleaner increases, reducing their separating ability. We propose to improve the cleaning technology by modernizing the design of the separating stars. This is achieved by using cylindrical brushes (in the amount of three pieces), which are mounted vertically to the horizontal plane of the star's rods. One end of the cylindrical brush is attached to one of the ends of the star bar, and the other end of the brushes is in the hollow bracket. All brushes are located at the same distance from each other along the periphery of the star. The second ends of the brushes, located in the hollow bracket, are fixed to each other and move freely in it. This improved design will allow the brushes to interact with the contaminated surface of the sprocket guard, improving their cleaning ability and eliminating cleaning breaks when working in harsh conditions.

Вплив зрошення на розвиток совки озимої в посівах пшениці озимої та кукурудзи

Relevance of research. Irrigation is a precondition for stable production of agricultural products, especially in regions with insufficient and unsustainable moisture. Studies have shown that the application of irrigation provides a change in the structure, chemical composition of the soil, as well as affect its aeration. The result of artificial irrigation is a change in the intensity of physiological processes in plants, their biomass, species composition of weeds in agrocenoses. These factors further significantly affect the species and quantitative composition of the entomofauna of agrocenoses, including winter wheat and maize. The purpose of the study was to determine the effect of drip irrigation and sprinkling on phenological and biological features of turnip moth development. Therefore, one of the main tasks of the research is to determine the dependence of fluctuations in the number of phytophagus on the type of irrigation. Results of the research. It has been established that drip irrigation and sprinkling are effective measures of crops’ protection against damage and invasion caused by turnip moth. The most dangerous for maize plants is the turnip moth in the “caterpillar” stage of the I-II age of spring generation. Sprinkling irrigation during the period of mass egg’s deposition and the revival of caterpillars of turning moth contributes to a significant decrease (by 6,8-67,7%) in the share of this type of pest, compared to conditions without an irrigation. Corresponding results were also obtained from a study of the effect of the different irrigation types on oulema in winter wheat crops. That is, the amount of the indicated phytophage under irrigation conditions was less than 3–6 times compared with the control (without irrigation). It was proved that in the case of sprinkling, compared with the control (without irrigation), the number of caterpillars of younger ages L1-L2 over the years ranged from 0,2 to 6,2 sp./m 2 , while in the control the density was 3,3 – 14,5 sp./m 2 . It has been established that the caterpillars of turnip moth in conditions of high soil moisture are more susceptible to entomopathogenic species of entomophoric fungi Beauveria bassiana (Bals.) Vuill. and B. tenella (Delacr.). Minimal damage to the pest by the indicated pathogens was noted on the caterpillars of older ages L3-L4. Without an irrigation, the proportion of infected caterpillars was 2,2 – 0,5%, which is 1,6 – 2,4 times less than sprinkling, and 1,1 – 4,8 times drip irrigation. Crop irrigation also affects the distribution of the pests over the soil layers. In dry and loose soil in rainfed areas, larvae and pupae of turnip moth occur at a depth of 10-20 cm, while in moist, compacted soil of irrigated fields up to 5 cm. This makes them more accessible for destruction during cultivation and other surface treatments. Conclusions. In the conditions of the Dry Steppe of Ukraine the terms of the turnip moth occurrence varies by years, depending on the weather factors. On average, during the years of research, the occurrence of a dangerous stage of turnip moth’ development (caterpillars) was observed in the third decade of May - the second decade of June. Irrigation and drip irrigation are effective enough to reduce the density of the phytophage population. During the observation period, it is noted that irrigation of crops by the method of sprinkling is a significant factor in limiting the number of caterpillars of turnip moth. The reduction in the proportion of the pest relative to the conditions without irrigation was 6.8-67.7%. The caterpillars of the L1-L2 younger generations are more vulnerable to the effects of irrigation in maize crops. It is noted that irrigation maximally reduces the number of eggs of turnip moth and pests in the early stages of development. That is, clarification of the effects of irrigation on the development of biting scoops in maize agrobiocenoses in the Steppe Dry region allows to determine the degree of threat to crops, reduce the density of the phytophage population, as well as to plan and adjust the main measures of crop protection against these damage.

Field dissipation of S-metolachlor in organic and mineral soils used for sugarcane production in Florida

AbstractDissipation of S-metolachlor, a soil-applied herbicide, on organic and mineral soils used for sugarcane production in Florida was evaluated using field studies in 2013 to 2016. S-metolachlor was applied PRE at 2,270 g ha−1 on organic and mineral soils with 75% and 1.6% organic matter, respectively. The rate of dissipation of S-metolachlor was rapid on mineral soils compared with organic soils. Dissipation of S-metolachlor on organic soils followed a negative linear trend resulting in half-lives (DT50) ranging from 50 to 126 d. S-metolachlor loss on organic soils was more rapid under high soil-moisture conditions than in corresponding low soil-moisture conditions. On mineral soils, dissipation of S-metolachlor followed an exponential decline. The DT50 of S-metolachlor on mineral soils ranged from 12 to 24 d. The short persistence of S-metolachlor on mineral soils was likely attributed to low organic matter content with limited adsorptive capability. The results indicate that organic matter content and soil moisture are important for persistence of S-metolachlor on organic and mineral soils used for sugarcane production in Florida.

Nutritional status of ‘Hass’ and ‘Fuerte’ avocado (Persea americana Mill.) plants subjected to high soil moisture

In this study, the effect of increased soil moisture on the nutritional status of two key commercial avocado (Persea americana Μill.) cultivars, ‘Fuerte’ and ‘Hass’, was examined. The results revealed that prolonged exposure of plants to high soil water content conditions (waterlogging) reduced the total nutrient content (absolute quantity) of almost all of the nutrients in scion’s tissues (leaves and stems) of both cultivars. The decrease of nutrient content in the ‘Fuerte’ leaves was more prominent/severe compared to the ‘Hass’ leaves, which could be the outcome of the reported higher sensitivity of the cultivar to soil waterlogged conditions in previous studies. Interestingly, the inability of ‘Fuerte’ avocado plants to withstand high soil moisture conditions was not reflected in the relative concentrations of most nutrients, both in leaves and stems. Indeed, significantly higher concentrations of P, K, B, Fe, and Zn were found in the leaves of ‘Fuerte’ waterlogged plants than in well-watered ones. This fact reveals that under marginal/stressful conditions, like waterlogging, nutrient concentration in tissues does not reflect potential negative effects on total nutrient uptake of avocado plants, obviously due to concentrated nutrient phenomena primarily created by the stress-dependent growth inhibition. Therefore, total nutrient content is proposed as a more representative indicator for assessing plant response to waterlogged conditions.

Effect of Farming Systems on the Spatial Variability of Soil Physical Properties and Soybean Yield

In no-tillage (NT) and minimum tillage (MT) areas, spatial variability of soil physical properties may affect crop yield. The aim of this study was to assess the spatial distribution of soil physical properties, as well as the yield components and grain yield of soybean (GY), based on the mapping of areas under soil conservation farming systems. We assessed yield components, GY and the physical properties of an Oxisol, under NT and MT using the t-student test, and geostatistics to assess spatial variability. The largest population of NT plants showed no spatial dependence and did not influence GY, but the components related to plant height and soil properties differed between systems. From a spatial standpoint, the kriging maps demonstrated that mass of one thousand grains (MOG), total porosity (TP) and soil bulk density (BD) influenced GY under NT, whereas TP1 exerted the most influence under high soil moisture conditions and MT. The maps make it possible to assess the spatial distribution of soil physical properties and the influence on GY, making them an important tool for more accurate production planning in soil conservation systems.

Persistence of imazapyr+imazapic in irrigated rice area and effect on soybean due to soil moisture and phytoremediation in the off-season

ABSTRACT The residue of imidazolinone herbicides in soil can be detrimental to soybean cultivation in rotation with Clearfield® rice. Thus, this research aimed to evaluate the ryegrass phytoremediation capacity on the imazapyr+imazapic residue in the soil in two soil moisture conditions in the off-season, and the effect on soybean growth in the next growing season. Two experiments were conducted between 2016 and 2017 in Santa Maria, Rio Grande do Sul state, Brazil. It was used the randomized block design in a 3 × 2 factorial. The first factor being the residue in the soil of 0, 210 and 420 g c.p.·ha–1 of the formulated mixture of the herbicides imazapyr+imazapic(525 + 175 g a.i.·kg–1) applied to rice in the 2015/2016 growing season, and the second factor being the presence or absence of ryegrass in the off-season. One experiment was conducted under soil moisture above 70% of field capacity in the off-season, and the other under ambient condition of soil moisture. The soil residue of the application of 420 g c.p.·ha–1 of the imazapyr+imazapic herbicides performed129 days before planting caused phytotoxicity and reduced dry matter of ryegrass under high soil moisture condition in the off-season in irrigated rice areas. Soybean, when planted 359 days after application, has its initial root and shoot growth affected by the residue of 210 and 420 g c.p.·ha–1 rates in high soil moisture condition in the off-season, regardless of ryegrass cultivation during the same period. However, grain yield is not affected.

Adaptation of seedbed preparation for spring cereals to unfavourably high soil moisture conditions in loam soil

ABSTRACTIn the future, increased precipitation in spring may force Scandinavian farmers to prepare their cereal seedbeds under conditions with excessive soil moisture, and thereby risk soil compaction, oxygen deficiency and yield loss. To adapt to climate change and avoid yield loss, a possible strategy may be to increase moisture loss from the seedbed, in contrast to earlier seedbed research, which has focused on minimising moisture loss. In this study, we compared light and heavy mechanisation alternatives for secondary tillage in an experiment with relatively dry and excess moisture conditions. The mechanisation alternatives’ suitability for excess moisture conditions was assessed in terms of resultant aggregate size distribution, penetration resistance, bulk density, air-filled porosity, air permeability, soil moisture content and cereal emergence. In general, lighter mechanisation created more favourable seedbed characteristics and seemed to be more suitable under excess soil moisture conditions. Larger aggregates after heavier mechanisation did not result in lower soil moisture content, probably because of compaction in the seedbed. We conclude that, under Norwegian conditions, the most important adaptation to climate change in seedbed preparation for spring cereals is the avoidance of compaction. Implement management for seedbed preparation should be more differentiated.

Impact of rainfall to the effectiveness of pig slurry shallow injection method for NH3 mitigation in a Mediterranean soil

Ammonia emission from fertilized cropping systems is an important concern for stakeholders, particularly in regions with high livestock densities producing large amounts of manure. Application of pig slurries can result in very large losses of N through NH3 volatilization, thus decreasing the N use efficiency (NUE) of the applied manure. Shallow incorporation has been shown to significantly abate these losses. In this field study, we assessed the impact of contrasting weather conditions on the effectiveness of shallow injection to abate NH3 emissions from pig slurry application to a Mediterranean soil. As potential trade-offs of NH3 abatement, greenhouse gas emissions were also measured under conditions of high soil moisture. Compared with surface application of slurry, shallow injection effectively and significantly decreased NH3 losses independently of weather conditions, but reductions of NH3 emission were greater after heavy rainfall. In contrast, under these conditions, shallow injection triggered higher emissions of N2O and CH4. Our findings reinforce the idea that any single-pollutant abatement strategy needs to be designed and assessed in a regional context and considering potential trade-offs in the form of other pollutants.