Lysimeter Experiment Research Articles

Seasonal effects reveal potential mitigation strategies to reduce N2O emission and N leaching from grassland swards of differing composition (grass monoculture, grass/clover and multispecies)

Multispecies pastures containing grasses, N-fixing legumes and forage herbs can maintain high herbage dry matter (DM) yield, while reducing the need for fertiliser N inputs thus potentially reducing harmful N losses such as nitrous oxide (N2O) emission and nitrate (NO3−) leaching to the wider environment. However, our understanding of these processes in grassland swards of contrasting composition is still very limited. A lysimeter experiment was carried out over 12 months to test the hypotheses that (1) cumulative and (2) seasonal N2O emission and N leaching would be highest from the Perennial Ryegrass only (PRG, 250 kg N ha-1 yr-1) treatment compared to three other treatments; Perennial Ryegrass and Low White Clover (PRG+LWC, 90 kg N ha-1 yr-1), Perennial Ryegrass and High White Clover (PRG+HWC, 0 kg N ha-1 yr-1) and Perennial Ryegrass, White Clover and Ribwort Plantain (PRG+WC+P, 45 kg N ha-1 yr-1) and (3) that the soil N cycling pathways (nitrification/denitrification) linked to these N losses would be different between treatments. Cumulative N2O emissions (2.74–3.25 kg N2O-N ha-1), leached N (10.91–13.70 kg N ha-1), DM yields (5083–5493 kg DM ha-1 yr-1) and N uptake (122–169 kg N ha-1 yr-1) were not significantly different between treatments. Nitrogen yield scaled N2O emissions were significantly lower from all other treatments compared to the high fertiliser N input PRG monoculture. A significant interaction between treatment and season showed that in Spring, N2O emission was significantly higher from PRG (1.39 kg N2O-N ha-1) and PRG+LWC (1.19 kg N2O-N ha-1) than PRG+HWC (0.81 kg N2O-N ha-1) and PRG+WC+P (0.85 kg N2O-N ha-1). This result was linked to a numerically lower fraction of nitrification (FN) for PRG+WC+P potentially indicating that biological nitrification inhibition associated with ribwort plantain could lessen N2O emissions. This study demonstrates some of the environmental benefits of grassland management systems that require less intensive chemical fertiliser N input.

PFAS concentrations in soil versus soil porewater: Mass distributions and the impact of adsorption at air-water interfaces.

Determining the risk posed by PFAS leaching from soil to groundwater requires quantification of the magnitude and temporal/spatial variability of PFAS mass discharge from the vadose zone, which is governed in part by the concentrations of PFAS in soil porewater. Porewater concentrations are impacted and mediated by the properties of the PFAS and soil, multiple transport and fate processes, and site conditions. The objective of this research was to delineate the relationship between soil porewater concentrations and soil concentrations, based on a comprehensive model of PFAS mass distribution within a soil sample volume. Measured parameters representing solid-phase sorption and air-water interfacial adsorption are used to illustrate the impact of soil and PFAS properties on the distribution of representative PFAS between soil and soil porewater. Literature data reported for soil and soil porewater concentrations of several PFAS obtained from outdoor lysimeter experiments are used to test the distribution model. Soil-to-porewater concentration ratios predicted with the model compared very well to the measured concentration ratios. The nondimensional distribution coefficient that describes the distribution of PFAS mass amongst all domains within a soil sample was observed to be a function of PFAS molecular size. Numerical simulations conducted for a model fire-training source area were used to illustrate the ranges in magnitude of soil versus porewater concentrations for representative field conditions. The results of the measured and simulated data sets demonstrated the importance of air-water interfacial adsorption for the distribution of the longer-chain PFAS within soil samples. PFAS soil porewater concentrations are anticipated to range from ng/L to mg/L depending upon soil concentrations, which in turn depend upon the nature of the site.

Optimization of Aeration for Accelerating Municipal Solid Waste Biodrying

Biodrying technology is commonly used in Thailand to produce refuse-derived fuel (RDF), however, this technology remains ineffective on high-moisture waste. Air supply is key to ensuring homogenous temperature development within the waste matrix during biodrying, increasing RDF quality. This study investigated negative aeration during local municipal solid waste biodrying to meet RDF standards in reduced time. Lysimeter experiments were performed on pre-shredded waste (300 kg/m3) using different aeration patterns. The temperature, vent gas oxygen level, weight loss, and leachate volume during the biodrying process were monitored. In addition, the treated waste’s temperature, moisture, and heating values were evaluated to determine the biodrying process efficiency. The results indicate that shorter heating phases can be achieved during continuous aeration. No significant temperature variation was observed in the waste layers, with a low standard deviation of 1.96% during constant air supply, indicating homogeneous temperature development during the biodrying process. The vent gas contained 15–20% oxygen and non-detectable methane, evidencing sufficient air supply. The total heat development was independent of aeration pattern; therefore, biodrying was unaffected by excess air supply at a 95% confidence level. The highest weight loss and moisture content reduction were 25% and 66%, respectively. The optimal aeration was continuous mode with non-excessive aeration, increasing the lower heating value from 2,884.0 to 4,938.0 kCal/kg, and reducing the moisture content from 48.5% to 22.2%. RDF quality can be improved 1.7 times to meet Thailand’s standards within a short biodrying period of 7 days using homogeneous temperature distribution operated under continuous aeration

AI-based ensemble modeling of landfill leakage employing a lysimeter, climatic data and transfer learning

Predicting leachate pollutants is of prime importance in detecting the amount of pollution in water resources adjacent to sources of leakage. In this study, Electrical Conductivity (EC) as a physicochemical water pollution parameter with the possibility of portable measurement was used as an indicator of leachate quality for the Tychy-Urbanowice operating and closed landfill complex. In order to simulate landfill conditions, two lysimeter experiments were conducted simultaneously. Using sensors mounted in the lysimeters, from the end of November 2018 to the end of December 2019, EC, waste temperature and waste moisture were measured for the open lysimeter and only waste moisture for the closed lysimeter. Additionally, meteorological data obtained from the nearest synoptic station and soil moisture and temperature acquired from the GLDAS satellite were employed as external data to analyze various conditions. Thereafter, Artificial Neural Network (ANN), Neuro-Fuzzy Inference System (ANFIS), and Emotional ANN (EANN) models were developed to determine the parameters affecting the EC value recorded for the open lysimeter and subsequently, predict the missing EC parameter of the closed lysimeter by employing the transfer learning method. Following that, in order to improve the precision of EC predictions, ensemble techniques were applied to the outputs of the models that were developed. The results showed that the moisture of the lysimeters made a significant contribution to the EC value prediction. It is worth mentioning that among ANN, ANFIS, and EANN, the EANN model yielded more precise results in EC estimation, with the average DC above 0.80 and 0.90 for individual and ensembled modeling in both the training and verification phases, respectively.

A three-year data set of gaseous field emissions from crop sequence at three sites in Germany

The purpose of the StaPlaRes project was to evaluate two innovative techniques of urea fertiliser application and to quantify greenhouse gas (GHG) emissions. All GHG emissions, as well as other gaseous emissions, agronomic and environmental variables were collected for three years (2016/2017–2018/2019) at three experimental field sites in Germany. All management activities were consistently documented. Multi-variable data sets of gas fluxes (N2O and NH3), crop parameters (grain and straw yield, N content, etc.), soil characteristics (NH4-N, NO3-N, etc.), continuously recorded meteorological variables (air and soil temperatures, radiation, precipitation, etc.), management activities (sowing, harvest, soil tillage, fertilization, etc.), were documented and metadata (methods, further information about variables, etc.) described. Additionally, process-related tests were carried out using lab (N2 emissions), pot and lysimeter experiments (nitrate leaching). In total, 2.5 million records have been stored in a Microsoft Access database (StaPlaRes-DB-Thuenen). The database is freely available for (re)use by others (scientists, stakeholders, etc.) on the publication server and data repository OpenAgrar for meta-analyses, process modelling and other environmental studies.

Стратегічне управління продуктивністю агроценозів у системі осушуваного землеробства

Goal. To improve the zone agrotechnological aspects of growing market-oriented crops in the system of drained agriculture. Methods. The experiment and research were carried out using generally accepted methods of field and lysimeter experiments in agriculture and crop production. Results. The results of experimental research on conducting highly efficient managed agriculture on drained lands, which ensures the creation of the most favorable conditions for the formation of highly productive agrocenoses and the expansion of their productive functions in the Polissia zone, are given. The influence of purposeful optimization of the technological parameters of the main links of reclamation agriculture: water-air and nutrient regimes of the drained soil with the use of the crop rotation factor on the formation of the yield of the commercial grain of commercially attractive crops was studied. Fertilizer systems for intensive technical crops adapted to the conditions of Polissia were improved. The effect of additional regulation of the water-air regime of the drained soil following the requirements of crops (favorable conditions of moisture) on their productivity was studied. The standards for the consumption of biogenic nutrients for crop formation were updated and clarified. The economic parameters of the technologies — the break-even points at which effective cultivation of crops could be achieved — were determined. The productivity potential of the proposed intensive short crop rotation, aimed at market conditions of farming, was evaluated. Conclusions. Strategic management of water, air, and nutrient conditions of the soil with effective plant nutrition in the conditions of a perfect meliorative system makes it possible to increase the productivity of arable land in the Polissia zone by 2.8 times (from 40 t/ha to 110 t/ha), which ensures effective development of plant industry in this territory and rational use of the resource potential of drained lands.

Effects of Timing in Irrigation and Fertilization on Soil NO3−-N Distribution, Grain Yield and Water–Nitrogen Use Efficiency of Drip-Fertigated Winter Wheat in the North China Plain

In the North China Plain, drip irrigation is gradually used in winter wheat production, and the improper management of water and fertilizer aggravates the risk of crop instability and groundwater pollution. A lysimeter experiment with three levels of fertilization timing (T1 = beginning; T2 = middle; and T3 = end of the irrigation cycle) and two irrigation rates (W1 of 30 mm and W2 of 20 mm) was carried out to investigate the effects of irrigation rate and fertilization timing on the soil NO3−-N distribution, crop development, yield, and water–nitrogen usage efficiency of winter wheat. The results indicated that, under the condition of delayed fertilization timing (T2 and T3), the trend of NO3−-N migration to the edge of moist soil became more apparent. The treatments of irrigation rate and fertilization timing significantly affected the plant height, water–nitrogen utilization efficiency, aboveground biomass, grain yield, and leaf area index. The maximum grain yield of 7688.67 kg ha−1 was found at W1T2, which had a nitrogen partial factor productivity (NPFP) of 32.04 kg kg−1. Moreover, W1T2 did not result in a significant reduction in irrigation water use efficiency (IWUE) (4.27 kg m−3) in comparison with other treatments (4.00–5.43 kg m−3). Based on crop growth, N uptake, yield, IWUE, and NPFP, the irrigation rate of 30 mm combined with fertilization in the middle of the irrigation duration could be considered as suitable irrigation and nitrogen timing for drip-irrigated wheat.

Effects of Water and Nitrogen Management on Water Productivity, Nitrogen Use Efficiency and Leaching Loss in Rice Paddies

Effective water and nitrogen (N) management strategies are critical for sustainable agricultural development. Lysimeter experiments with two deep percolation rates (low percolation and high percolation, i.e., LP and HP: 3 mm d−1 and 5 mm d−1) and five N application levels (N0~N4: 0, 60, 135, 210 and 285 kg N ha−1) were conducted to investigate the effects of controlled drainage on water productivity (WP) and N use efficiency (NUE) in water-saving irrigated paddy fields. The results demonstrated that NH4+-N and NO3−-N were the major components of total nitrogen (TN) in ponded water and leachate, accounting for more than 77.1% and 83.6% of TN, respectively. The risk of N leaching loss increased significantly under treatment of high percolation rates or high N application levels. High percolation loss required greater irrigation input, thus reducing WP. In addition, N uptake increased with increasing N application, but fertilization applied in excess of crop demand had a negative effect on grain yield. NUE was affected by the amount of N applied and increased with decreasing N levels. Water and N application levels had a significant effect on N uptake of rice, but their interaction on N uptake or NUE was not significant. For the LP and HP regimes, the highest N uptake and WP were obtained with N application levels of 285 kg ha−1 and 210 kg ha−1, respectively. Our overall results suggested that the combination of controlled drainage and water-saving irrigation was a feasible mitigation strategy to reduce N losses through subdrainage percolation and to provide more nutrients available for rice to improve NUE, thus reducing diffuse agricultural pollution. Long-term field trials are necessary to validate the lysimeter results.

Does macropore flow in no-till systems bypass mobile soil nitrogen after harvest?

Reduced tillage practices, including no-till, have been proposed to reduce NO3- leaching in agricultural soils. However, this is not universally supported by experimental data, and the effect of reduced tillage on NO3- leaching is likely connected to the interaction between macropore flow and resident solutes. To investigate this, we carried out infiltration experiments on intact soil cores from conventionally tilled (CT) and no-till (NT) plots, recording resident concentrations and breakthrough curves (BTCs) of three solutes (a tritium pulse, resident Br- tracer and native NO3-). We then fitted a dual porosity model implemented in HYDRUS-1D, to the experimental BTCs. By assuming different initial solute distributions between phases, we investigate possible bypass mechanisms. In the lysimeter experiment, leaching of all solutes initiated and peaked earlier in NT compared to CT, indicating increased macropore flow. However, total leached NO3- was greater in CT, and higher resident NO3- concentrations were found after the experiment in NT, suggesting an overall bypass effect. In the fitted dual porosity model, saturated water contents in the mobile phase were six times smaller in NT than in CT, with smaller horizontal solute transfer rates for NO3- than for Br-. The optimal initial proportion of total resident NO3- in the mobile phase was 7.5% in NT and 65% in CT. Our results suggest a bypass effect of native resident NO3- in NT soils related to a smaller volume of soil involved in macropore flow. Added solutes, however, remain susceptible to quicker leaching in NT compared to CT under intense precipitation.

Autumn Tillage Reduces the Effect of Plant Cover on Topsoil Nitrogen Leaching

Keeping cover crops to reduce nitrogen leaching often conflicts with timing tillage operations before the soil becomes un-trafficable during winter, while leaving cover crops in the field until spring raises concerns over pre-emptive competition with the following crop. Therefore, farmers may resort to tilling their fields in autumn after letting cover crops remain in the fields for only a short period of time. We explore the effects of this practice in a laboratory lysimeter setting by analyzing the leaching of nitrate from intact topsoil cores. Cores were extracted from no-till (NT) plots and plots tilled in autumn (AuT), in areas kept bare (B) and with volunteer winter rye plant cover (V) after harvest. Nitrate breakthrough curves show that V significantly reduced N leaching by 61% relative to B in NT, but did not have a significant effect in AuT. Dissection of leached cores and undisturbed reference cores indicated a significant removal of mineral N from the soil during the lysimeter experiment for all treatments except V in NT. This indicates that volunteer cover removed a crucial amount of leachable N and suggests that tillage counteracted the effect of V in AuT, likely due to a combination of reduced uptake and re-mineralization of N in cover crop residue.

THE INFLUENCE OF THE SALINITY AND WEED CONTROL TREATMENTS ON SOME BARLEY CULTIVARS AND ITS ASSOCIATED WEEDS

In Egypt barley cultivated in new and outlying lands, its yield and quality affected by salinity as abiotic and weeds as biotic stresses which constraints to barley production. Two lysimeter experiments were conducted during seasons 2019/2020 and 2020/2021 winter seasons. In the present work, studied four saline water levels (2.33,4,8 and 12dSm-1) to distinguish the salinity stress tolerance among four of Egyptian barley cultivars (Giza 123, Giza 132, Giza 137 and Giza 138), in addition to find a suitable weed control treatments under salinity stress using three factors in completely randomized design (CRD) with three replications The main findings illustrated that four SSR primers (Bmac 0040, EBmac0871, Bmag 135 and Bmag 770) were generated clear patterns with the high polymorphism (100%); and enable plant breeders to select individual plants based on their marker pattern (genotype) rather than their observable traits (phenotype). Using Bmag 770, amplified specific allele with molecular size 260 bp found in the salt tolerance cultivars (Giza 123 and Giza 137) as a tolerant to salinity. Each of the three studied factors (salinity, weed stress and weed control treatments) individually and their interactions had a significant effect on weed populations and on barley yield economically. The interaction among the factors of the trial and the recommended of the two herbicides (bromoxynil octanoate at 1 L fed-1) +( clodinafop propargyl 2.5% + Pinoxaden 2.5%) at 0. 5 L fed-1) gave the highest means of the characters studied and economic criteria. Therefore, these interactions could be recommended in barley farms to achieve reduction in weed growth under saline conditions and harmful effect of them and boosting barley plantations productivity as well. Economic criteria display that Giza 137 is a good choice cultivar for salinity soil because of its high weed tolerance ability (WTA) and Giza 123 good cultivar for grown in salinity soil but it poor WAT so advised to using by herbicides as weed management to reduce weeds population and increase yield toward increasing farmer’s income under salinity soil area.

Evapotranspiration partitioning for winter wheat with shallow groundwater in the lower reach of the Yellow River Basin

Accurately partitioning evapotranspiration (ET) remains one of the key research gaps in agro-ecosystem water research. The interaction of shallow groundwater with winter wheat increased the complexity of ET partitioning. Here we proposed a cutting method to partition ET into soil evaporation (E) and transpiration (T). Field multiple lysimeter experiments under 4 different watertable conditions were conducted at the Yucheng Experimental Station to investigate the partitioning of ET for winter wheat under shallow groundwater. Results showed that the cutting method is applicable and could obtain reasonable ratio of T to ET for crop land of winter wheat. Moreover, the T/ET could be generalized into a curve for representing the ratio of T to ET (i.e. K=T/ET) at the mid- and late-season stages of winter wheat. The maximum value of generalized T/ET curve (Kmax) increased with the increase of groundwater table depth (DTW), and was 0.651, 0.768, 0.771 and 0.869 for the depth of 0.4 m, 0.7 m, 1.1 m and 1.5 m, respectively. The higher transpiration proportion corresponded to the higher yield of winter wheat, which indicated that increased groundwater depth was benefit to enhance the groundwater consumption by transpiration and hence yield when watertable depth was within 1.5 m. Moreover, the lower evaporation proportion might lower the soil salinization risk due to less soil evaporation. It is important for the understanding of the interaction between evapotranspiration components of crop with shallow groundwater and the sustainable management in the lower reach of the Yellow River Basin.

Treating acid mine drainage with decomposed organic soil: Implications for peatland rewetting

Acidification and salinisation of groundwater and surface water bodies are worldwide problems in post-mining landscapes due to acid mine drainage (AMD). In this study, we hypothesised that highly decomposed peat offers a suitable substrate for mitigating AMD pollution of water bodies and that hydraulic load affects the removal efficiency of iron and sulphate. A lysimeter experiment was conducted mimicking peatland rewetting to quantify iron and sulphate removal and pH changes at different loading rates. The low initial pH of 4 rose to 6 and electrical conductivity declined by up to 47%. The initially high concentrations of iron (>250 mg/L) and sulphate (>770 mg/L) declined by, on average, 87 and 78%, respectively. The removal efficiency of sulphate was negatively correlated with either the hydraulic or the sulphate load, respectively, i. e. the lower the hydraulic load, the higher the removal efficiency of sulphate. However, the removal of iron was not explained by the load. The results imply that desulphurication and thus subsequent precipitation of iron sulphides was the main removal process and that peatland rewetting is an effective measure to mitigate AMD pollution of freshwater systems. For the heavily AMD-polluted studied section of the River Spree, we estimated by combining experimental with field data that a sulphate load reduction of the river by about 20% (36,827 tons/yr) will occur if all peatlands in the sub-catchment (6067 ha; 6.7% of the total area) are rewetted. Future investigations must show if the pollutant removal is declining over time in decomposed peat layers due to acidification and/or lack of bioavailable carbon and how the rewetting of peatland with AMD will affect the restoration of their ecosystem functioning in the long term.

Effect of Some Organic Substances and Foliar Application of Nano-Silica on Physico-Chemical Soil Properties and Yield of Wheat in Salt Affected Soils

Ensuring food security under climate change scenario requisites amending degraded soils and sustainably boost staple crops yield in a biologically viable way through effective plant nutrition management strategies. Two multi-year lysimeter experiments at Sakha Agricultural Research Station, Kafr El Sheikh, Egypt, were conducted to investigate the impact of soil organic substances and foliar application of nano-Silica on physico-chemical soil properties and yield of wheat in salt affected soils (2017/18 and 2018/19 winter seasons). The experiment was executed in split plot with three replicates having organic substances (Molas (M),Compost tea (CT), K-humate (KH), M+CT, M+KH, CT + KH, M+CT+KH and control treatment in main plots while sub plots had foliar application of (tab water and nano-Silica).The results showed that physico-chemical properties (bulk density, porosity , cation exchange capacity, electrical conductivity, exchangeable sodium percentage etc.) and fertility (availability of Nitrogen, Phosphorus and Potassium ) of the soil were significantly influenced by all organic substances, however co-application of molas+K-humate+compost tea remained unmatched. The same treatment combination also remained effective in boosting Nitrogen and protein in grain along with wheat yield during both seasons. With foliage applied nano Silica remained superior by recording the highest yield attributes and grain yield of wheat. Therefore, it is inferred that co-application of organic substances and foliage applied of nano-Silica could be developed as an effective approach to restore and conserve the soil and increase wheat productivity in salt affected soils environment arid and semi-arid regions.

Dynamics in Diffusive Emissions of Dissolved Gases from Groundwater Induced by Fluctuated Ground Surface Temperature.

During the lateral transport with subsurface flow, amounts of manufactured volatile organic chemicals and gases dissolved in groundwater are emitted into the atmosphere via upward diffusion through soils. Quantifying gas emissions is important for assessing environmental risk associated with these constituents (e.g., air pollution and global warming). It is widely recognized that the temperature would affect gas spreading in soils, which in turn regulates the gas emission from groundwater. However, the upward diffusive gas emission induced by the fluctuated ground surface temperature (GST) remains unexplored. A coupled heat transfer and gas transport model is developed to investigate emissions of tetrachloroethylene (PCE) and N2O, a typical manufactured volatile organic chemical and a natural gas, from groundwater with seasonally fluctuating GSTs. The results indicate that both PCE and N2O emissions vary significantly from month to month. Moreover, fluctuations of emissions lag obviously behind the fluctuation of GST due to the damping effects of both capillary fringe and soil sorption. The proposed model agrees with the observed data from a monolith lysimeter experiment well. The model is also applied to the estimations of N2O emissions from 12 aquifers in Walloon Region, Belgium. The estimated N2O emission is 12.6 μg N/m2/d that falls in the estimated range (9.0-21.5 μg N/m2/d) using the IPCC emission factor approach that commonly accounts for the N2O emission of groundwater discharge to surface water only. It suggests that the upward diffusion is non-negligible for estimations of N2O emission from groundwater.

Partitioning evapotranspiration using water stable isotopes and information from lysimeter experiments

ABSTRACT Stable isotope techniques can be used to investigate evapotranspiration and its partitioning into evaporation and transpiration. However, verification is often difficult due to missing information about actual evapotranspiration. Therefore, in this study a methodology tested for laboratory conditions was modified for field applications. Evapotranspiration, which was determined with weighing lysimeters, and isotope techniques were combined with soil water and lysimeter measurements to calculate evaporation and transpiration rates of soybean under natural conditions. The case study was made 2019 in Groß-Enzersdorf, Austria. The results showed that the methodology was suited to measure actual variations of evaporation and transpiration ratios, even during dry periods. Weekly evaporation (0.5 – 2.2 mm d−1) and transpiration (1.3 – 4.3 mm d−1) rates as well as the respective ratios (transpiration 43-85 %) agreed with the results of numerical modeling and values from literature confirming the applicability of the modified methodology for portioning evapotranspiration in the field.

Municipal sewage sludge as a source of microelements in sustainable plant production: a laboratory lysimeter study

The aim of the work was to characterize the samples of sewage sludge (SSL) originated from the Wastewater Treatment Plant Piešťany (TAVOS, a.s., Trnava, Slovakia) in terms of their potential application into the soils. Within the physico-chemical characterization of SSL, the samples were analysed in terms of the values of pH, cation exchange capacity (CEC), total organic carbon (TOC), water holding capacity (WHC), as well as the presence of heavy metals. It was found that SSL contained significant amounts of microelements Zn (1,269 mg.kg-1, d.w.) and Cu (224 mg.kg-1, d.w.). Laboratory lysimeter experiments involving the application of SSL into the top layer of agriculturally used soil (0 – 10 cm) forming a soil column, in which seedlings of tobacco (Nicotiana tabacum L.) were cultivated, showed that in the case of SSL application in the highest permitted amounts (15 t.ha-1) only 0.11 % Zn and 0.07 % Cu were released into the soil eluate during a 28 day of exposure, while in tobacco plants 0.13 % Zn and 0.05 % Cu were accumulated from the total amount of Zn and Cu originated from the application of SSL (Zn – 133 mg and Cu – 23.5 mg). When applying SSL in amount 30 t.ha-1 i.e., in the dose exceeding the permitted limits, only 0.02 % Zn and 0.04 % Cu were released into the soil eluate and 0.16 % Zn and 0.09 % Cu were accumulated in tobacco plants from the applied amount of SSL (Zn – 267 mg and Cu – 47.0 mg).

AGRO-PHYSIOLOGICAL AND SEED VIABILITY RESPONSE OF FIVE EGYPTIAN CLOVER GENOTYPES TO DIFFERENT LEVELS OF SALINE IRRIGATION WATER

Salinity is a major barrier to Egyptian clover production because it disrupts its growth, physiological, and biochemical processes, hence economically reducing yield. Laboratory and lysimeter experiments were conducted to evaluate five Egyptian clover genotypes (Sakha 4, Sakha 2000, Sakha 2014, Gemmiza 1 and Serw1) under three levels of saline irrigation water (control, 4.5 and 9.0 dS m-1) during 2018 / 2019 and 2019 / 2020 seasons. Results demonstrated that irrigation with 9.0 dS m-1 recorded the lowest values of all seed viability parameters, fresh, dry forage yields, plant height, number of stem, fresh leaf / stem and dry leaf/ stem percent, chlorophyll content, relative water content, K/ Na ratio, on contrary the contents of both proline and malondialdehyde (MDA) increased under irrigation with 9.0 dS m-1 as a result of salt stress. Among the studied five genotypes, Sakha 2014 was superior to other genotypes and ranked first in all studied traits except K/Na ratio, followed by Serw1 and Sakha 4 with insignificant differences between them, while Gemiza 1 and Sakha 2000 recorded the lowest values of physiological and agronomic traits also with insignificant differences between them. It could be concluded that the cultivation of Sakha 2014, Serw1, and Sakha4 is suitable to obtain high yield of Egyptian clover under saline conditions.

Effects of waterlogging at different stages and durations on maize growth and grain yields

Lysimeter experiments were conducted under a rain shelter to investigate the effects of waterlogging imposing at different stages and with different durations on maize growth, grain yield and yield components in 2017–2019 seasons. The waterlogging treatments were implemented for different durations (2, 4, 6, 8 and 10 days respectively) at the seedling (V3), jointing (V6), tasseling (VT) and milk maturity (R3) stages, with non-waterlogging treatment as control (CK). Results shown that waterlogging stage, duration, and the interaction of stage and duration have significant affects (P < 0.01) on all growth index, all yield index, and nearly all yield components indexes in the three seasons. The waterlogging stress decreased plant height, leaf area index, chlorophyll content index, ear length, ear diameter, grain row number per ear, 100-grain weight, grain number per ear, aboveground biomass and harvest index, and increased the bald tip length, and eventually a significant reduction in the grain yield of summer maize. In addition, the severity of the adverse effects increased generally with the lengthening of waterlogging duration. The results of dominant influencing factors indicated that waterlogging occurred at V6 stage have the greatest effects on maize growth and grain yield, followed by V3, VT, and R3 stages, and that the 100-grain weight and grains per ear had the largest effect on grain yield, and other indexes affected maize yield by affecting the 100-grain weight and grains per ear.

Zeolite increases paddy soil potassium fixation, partial factor productivity, and potassium balance under alternate wetting and drying irrigation

Alternate wetting and drying irrigation (AWD) affects soil and plant K availability in the paddy field. However, it is unclear how zeolite amendment alters soil K fixation, K utilization, and K balance in the paddy rice systems under AWD compared with continuous flooding irrigation (CF). A two-year lysimeter experiment with a split-plot design was used to evaluate the effect of irrigation regime and fertilization management in paddy fields in Donggang, northern coastal China in 2018 and 2019. The field experiment included two irrigation regimes (CF and AWD) as the main plots, and three zeolite/K managements (Z0K0, no added zeolite or K; Z5K30, 5 t ha–1 zeolite and 30 kg ha–1 K; Z0K60, no added zeolite and 60 kg ha–1 K) as the subplots. The results showed that zeolite mitigated the reductions in grain yield and aboveground biomass caused by water stress in AWD. Zeolite addition also caused soil K fixation under AWD, which reduced K leaching losses and avoided excessive K absorption by rice plants, thus contributing to sustainable rice production by preventing soil K depletion. The Z5K30 treatment had lower total K leaching losses and higher K partial factor productivity (the ability of rice to use K to produce yield) than the commonly used practice (Z0K60). Compared with Z0K60 under CF, the Z5K30 treatment under AWD produced higher grain yield, economic benefit, water use efficiency, and total K balance. Therefore, appropriate zeolite and K amendments could be economically and environmentally feasible for rice production under AWD conditions.