The Effects of Soil Drying Out and Rewetting on Nitrogen and Carbon Leaching—Results of a Long-Term Lysimeter Experiment

As a result of global climate change, heavy rainfall events and dry periods are increasingly occurring in Germany, with consequences for the water and solute balance of soils to be expected. The effects of climate change on nitrogen and carbon leaching were investigated using 21 non-weighable manually filled lysimeters of the UFZ lysimeter facility Falkenberg, which have been managed since 1991 according to the principles of the best management practices and organic farming. Based on a 29-year dataset (precipitation, evaporation, leachate, nitrate and dissolved organic carbon concentrations), the lysimeter years 1995/96, 2018/19, and 2003/04 were identified as extremely dry years. Under the climatic conditions in northeastern Germany, seepage fluxes were disrupted in these dry years. The reoccurrence of seepage was associated with exceptionally high nitrogen concentrations and leaching losses, which exceeded the current drinking water limits by many times and may result in a significant risk to water quality. In contrast, increased DOC leaching losses occurred primarily as a result of increased seepage fluxes.

Effect of Chemical Reclamation on the Physiological and Chemical Response of Rice Grown in Varying Salinity and Sodicity Conditions

Salinity and sodicity are the major abiotic constraints that prevail in arid and semi-arid regions. Proper management is required for productive use of this land. Reclamation of sodic and saline-sodic soils is highly site-specific that describes the diverse response of different soils to different amendments. These reclamation practices also alter the plant's physiological and ionic characteristics. This experiment aimed to better understand the physiological and ionic responses of rice crop at different salinity/sodicity levels. A lysimeter experiment was set forth with soil having ECe (dS m-1):SAR (mmol L-1)1/2 levels as 4:20, 8:40, 12:60 and 16:80 and all the levels were treated with organic (farm manure at 25 Mg ha-1) and inorganic (gypsum at 100% soil gypsum requirement (SGR) and sulphuric acid equivalent to 100% SGR) amendments keeping no ammendment as control. Results revealed that the maximum relative increase in physiological attributes (photosynthetic rate, transpiration rate, stomatal conductance and total chlorophyll contents), ionic contents (nitrogen, potassium and K:Na ratio) and growth of rice were recorded with sulphuric acid application followed by gypsum. On an average 25%, 31% and 45% increase in biological yield, plant height and paddy yield, respectively was observed with sulphuric acid application over control. It is concluded that sulphuric acid and gypsum both were the best amendments for reclamation of soil having a low level of salinity/sodicity whereas, at higher salinity/sodicity levels, only sulphuric acid seemed better for improved rice production. © 2021 Friends Science Publishers

Utilization of Fish Farm Effluent for Irrigation Short Rotation Willow (Salix alba L.) under Lysimeter Conditions

Efficient utilization, treatment, and disposal of agricultural wastewater and sewage sludge are important environmental risks. In our research, effluent water from intensive aquaculture was evaluated for the irrigation of short rotation energy willow in a lysimeter experiment. Two different water types and their combinations were applied with weekly doses of 15, 30, and 60 mm, respectively. Our results revealed that implementing effluent water instead of fresh water could potentially increase the yield of the willow due to its higher nitrogen content (29 N mg/l). The biomass of irrigated short rotation coppice (SRC) willow plants were between 493–864 g/plant, 226–482 g/plant, and 268–553 g/plant dry weight during experiment period (2015–2017), respectively. However, due to the chemical properties (Na concentration, SAR value) of effluent water, the increase of the soil exchangeable sodium percentage (ESP) was significant and it can lead to soil degradation in the long term. The current study also investigated the relationship between chemical composition of the plant tissue and the irrigation water. In the case of K-levels of willow clones, an increasing trend was observed year-by-year. In terms of N and Na content was localized in leaf parts, especially in samples irrigated with effluent. Less N and Na values were detected in the stem and in the samples irrigated with surface water. In SRC willow plants, phosphorus was mostly localized in the stem, to a lower extent in the leaf part. The difference is mostly observed in the case of the amount of irrigation water, where the P content of the examined plant parts decreased with the increase of the amount of irrigation water. In the case of phenological observations, higher values of plant height were measured during diluted and effluent irrigation. Moreover, the SPAD of the plants irrigated with effluent water exceeded the irrigated ones with surface water.

Can biochar restore soil quality in a degraded forest and vineyard soil in a one-year percolation lysimeters study, in Portugal?

<p>The use of biochar has increased worldwide in the last years due to its good results for several soil quality indicators. However, restoration potential depends on the type and amount of biochar for each specific soil and land use. In order to investigate this restoration potential differential, we conducted an experiment where we amended two contrasting degraded soils with the same biochar. We installed a controlled and fully randomized percolation lysimeter experiment (3 replicates) with 15 lysimeters on a moderately steep slope angle, monitored for one year. Two types of soil were collected, a low organic matter, hydrophilic vineyard soil and a high organic matter, hydrophobic forest soil. Biochar was applied at 4% for both soils, and an additional treatment at 2% for the forest soil only. Selected soil quality indicators are: soil organic matter, medium weight diameter, aggregate stability, bulk density, pH, electric conductivity, potassium (K), phosphorus (P), soil water repellency, biomass quality. The present study comprises four data collections in different seasons along the year, enabling to compare the development of the biochar effects on different types of soil and its short- and medium-term behaviour.</p>

Risk evaluation of radionuclides contamination on soil and groundwater under different scenarios simulating by HYDRUS-1D

<p>A large number of radionuclides, produced by nuclear accidents or nuclear waste, may cause radioactive contamination in the agricultural and aquatic ecosystems. Under these circumstances, it is necessary to optimize the remediation of agricultural areas polluted by radionuclides using innovative monitoring and prediction techniques. To mitigate radioactive contamination in farmland soil and effectively protect groundwater, some measures should be taken against on field investigation, laboratory experiment and model prediction. In this study, the HYDRUS-1D model was used to simulate the vertical migration of <sup>137</sup>Cs and <sup>60</sup>Co in farmland soil in northern China calibrating by the soil lysimeter experiment, and the scenario simulations of <sup>137</sup>Cs and <sup>60</sup>Co migration were conducted under different radioactive levels. Results showed that the order of sensitivity in saturated water content (θ<sub>s</sub>), residual water content(θ<sub>r</sub>), saturated hydraulic conductivity(K<sub>s</sub>) and distribution coefficient (K<sub>d</sub>) applied in HYDRUS 1D model was K<sub>d</sub> > θ<sub>s</sub> > θ<sub>r</sub> >K<sub>s</sub>. The simulated concentrations ​​of <sup>137</sup>Cs and <sup>60</sup>Co in Brown soil and Aeolian sandy soil on day 175 and 355 were significantly positively correlated with the measured values​​ (r>0.90, p<0.01). The verification results showed that the predictive values on the 577<sup>th </sup>day were also significant positive correlated with the measured values ​​(r>0.90, p<0.01). The RMSE, CRM and NRMSE calculating by simulated and measured values ​​of <sup>137</sup>Cs and <sup>60</sup>Co in soil were very small, indicating that HYDRUS 1D can be used to simulate the migration of radionuclides in farmland soil. Scenarios simulation results revealed that radionuclides were concentrated in the surface layer within 5 cm, but the migration depth has exceed 10 cm soil depth, and even reaches up to 23.5 cm depth at high concentration level. The surface soil should be cleaned timely to protect groundwater with high level from radioactive contamination and further study should be done about horizontal transport and numerical simulation.</p>

Amorphous silica increases the water holding capacity of soils – from mechanistic understanding to field experiments

<p>A main problem currently facing agriculture is drought. More frequent and longer drought periods are predicted to threaten agricultural yields in future. The capacity of soils to hold water is a highly important factor controlling drought stress intensity for plants during the growing phase. Amorphous silica (ASi) has been suggested to be able to mitigate these problems. Amorphous silica pools in natural soils are in the range of 0-6%. However, ASi pools have declined in agricultural soils since the development of high intensity agriculture to values of <1% due to yearly crop harvests, decreasing the water holding capacity of the soils. Here, we analyzed the effect of ASi on the water holding capacity (WHC) of soils. ASi was mixed at varying rates with different soils. Afterwards, the retention curve of the soils was determined. Here we show that ASi increases the soil water holding capacity substantially, by forming silica gels with a water content at soil saturation higher than 700%. An increase of ASi by 1% or 5% (weight) increased the water content at all studied water potentials and plant available water increased by >40% and >60%, respectively. In a lysimeter experiment we found that ASi strongly increased the WHC of soils, too. In a field experiment we found an increase of soil moisture after ASi fertilization over the whole growing season. Furthermore, wheat plant grown in this field experiment suffered less from drought and had a later onset of senescence. Our results suggest that ASi is a main control on soil water availability, potentially decreases drought stress for plants in future.</p>

Field evaluation of a boron recycling fertiliser

Boron (B) is a plant nutrient and a limited mineral resource. Therefore, secondary B sources such as end-of-life cellulose fiber insulation (CFI) should be preferred for B fertiliser production over primary borates. In addition, crop B fertilisation is challenging because B is only weakly adsorbed in soils and prone to leaching in particular if the soil pH is below 7. The objectives of this study were to assess the effect of pyrolysed CFI (B-Biochar) on crop B uptake in the field and on B leaching in a lysimeter study. B-Biochar was pyrolysed at 600 °C and tested (1) in a field experiment with maize (Zea mays L.) and sunflower (Helianthus annuus L.), and (2) in a lab microlysimeter experiment to study B leaching under simulated rainfall. In the field experiment, B concentration in plant tissue increased by up to 100% with B-Biochar compared to the control (from 29.6 to 61.6 mg B/kg in young sunflower leaves) and was only slightly lower (–10% to –20%) than with water-soluble Na-tetraborate (Borax). This lower uptake was attributed to the slow-release properties of the B-Biochar. In the lysimeter experiment, 41% and 55% of added B through B-Biochar was leached below 16 cm depth when fertilised with 1 and 2 kg B/ha, respectively, but B concentration of the leachate remained below the 1 mg B/L threshold value for drinking water in the European Union. In conclusion, CFI has a strong potential as a secondary B source for fertiliser production, and pyrolysis appears to be a suitable process for that purpose. During the processing of CFI to fertiliser, more focus should be given to slow B release in the future in order to reduce losses by leaching.