LAI estimation through remotely sensed NDVI following hail defoliation in maize (Zea mays L.) using Sentinel-2 and UAV imagery

Extreme events such as hailstorms are a cause for concern in agriculture, leading to both economic and food supply losses. Traditional damage estimation techniques have recently been called into question since damages have rarely been quantified at the large-field scale. Damage-estimation methods used by field inspectors are complex and sometimes subjective and hardly account for damage spatial variability. In this work, a normalized difference vegetation index (NDVI)-based parametric method was applied using both unmanned aerial vehicles (UAV) and Sentinel-2 sensors to estimate the leaf area index (LAI) of maize (Zea mays L.) resulting from simulated hail damage. These methods were then compared to the LAI values generated from the Sentinel-2 Biophysical Processor. A two-year experiment (2020-2021) was conducted during the maize cropping season, with hail events simulated during a range of maize developmental stages (the 8th-leaf, flowering, milky and dough stages) using a 0-40% defoliation gradient of damage intensities performed with the aid of specifically designed prototype machines. The results showed that both sensors were able to accurately estimate LAI in a nonstandard damaged canopy while requiring only the calibration of the extinction coefficient k ( ϑ ) in the case of parametric estimations. In this case, the calibration was performed using 2020 data, providing k ( ϑ ) values of 0.59 for Sentinel-2 and 0.37 for the UAV sensor. The validation was performed on 2021 data, and showed that the UAV sensor had the best accuracy (R2 of 0.86, root-mean-square error (RMSE) of 0.71). The k ( ϑ ) value proved to be sensor-specific, accounting for the NDVI retrieval differences likely caused by the different spatial operational scales of the two sensors. NDVI proved effective in parametrically estimating maize LAI under damaged canopy conditions at different defoliation degrees. The parametric method matched the Sentinel-2 biophysical process-generated LAI well, leading to less underestimations and more accurate LAI retrieval.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11119-023-09993-9.

Emerged macrophytes to the rescue: Perfluoroalkyl acid removal from wastewater and spiked solutions

This study evaluated the potential for three emergent aquatic macrophytes to remove perfluoroalkyl acids (PFAAs) from contaminated waters in constructed wetland systems. Three plants (Iris pseudacorus L., Phragmites australis (Cav.) Trin. Ex Steud., and Typha latifolia L.) were exposed to an effluent from a tannery wastewater treatment plant (WWTP) that contained residual PFAAs, and to three spiked solutions with increasing concentrations of 11 perfluorocarboxylic acids (PFCAs) and three perfluorosulfonic acids (PFSAs) (500, 2500, and 5000 ng L^-1, each). Thirty-six lightweight expanded clay aggregate- and vegetation-filled tanks (0.35 × 0.56 × 0.31 m) were exposed to the tested solutions at the Acque del Chiampo SpA WWTP in Arzignano (NE Italy). Throughout the experiment, PFAA concentrations and physicochemical water parameters were monitored via measures of the clay material, plastic tank inner surfaces, and below- and above-ground biomasses (after harvest). Vegetation growth was shown to be unaffected by increased PFAA levels in the spiked solutions. Alternatively, total biomass was significantly reduced when WWTP water was used, although we attribute this finding to the relatively high salinity that mainly restricted Typha and Iris development. The tested macrophytes were found to remove a significant PFAA mass from the contaminated waters (36% to ca. 80%, on average) when Phragmites was subjected to the highest PFAA concentrations. Such large accumulations were primarily associated with long C-chain PFAA stabilization in belowground biomass (26%, on average). Most PFAA translocations were observed in Typha, which accumulated mostly short perfluorinated C-chain PFBA, PFPeA, and PFHxA in the aboveground biomass (16%, on average). Despite some growth limitations, Iris was still the most efficient macrophyte for translocating PFBS under WWTP.

Uptake and translocation of perfluoroalkyl acids by hydroponically grown lettuce and spinach exposed to spiked solution and treated wastewaters

Perfluoroalkylated acids (PFAAs) are ubiquitous xenobiotic substances characterized by high persistence, bioaccumulation potential and toxicity, which have attracted global attention due to their widespread presence in both water and biota. In this study, the main objective was to assess PFAAs uptake and accumulation in lettuce (Lactuca sativa L.) and spinach (Spinacia oleracea L.) when fed with reclaimed wastewaters that are usually discharged onto a surface water body. Lettuce and spinach were grown in hydroponic solutions, exposed to two different municipal wastewater treatment plant (WWTP) effluents and compared with a spiked-PFAAs aqueous solution (nominal concentration of 500 ng L-1 for each perfluoroalkyl acid). Eleven perfluoroalkyl carboxylic acids and three perfluoroalkyl sulfonic acids were determined in the hydroponic solution, as well as quantified at the end of the growing cycle in crop roots and shoots. Water and dry plant biomass extracts were analyzed by liquid chromatography-electrospray ionization tandem spectrometry LC-MS/MS technique. The bioconcentration factor of roots (RCF), shoots (LCF), and the root-shoot translocation factor (TF) were quantified. In general, results showed that PFAAs in crop tissues increased at increasing PFAAs water values. Moreover some PFAAs concentrations (especially PFBA, PFBS, PFHxA, PFHpA, PFHxS) were different in both shoots and roots of lettuce and spinach, regardless of the type of water. The long C-chain PFAAs (≥9) were always below the detection threshold in WWTPs effluents. However, when PFAAs were detected, similar bioconcentration parameters were found between crops regardless the type of water. A sigmoidal RCF pattern was found as the perfluorinated chain length increased, plus a linear TF decrease. Comparing bioconcentration factor results with findings of previous studies, lettuce RCF value of PFCAs with perfluorinated chain length ≤ 9 and PFSAs was up to 10 times greater.

Trade-offs among ecosystem services advance the case for improved spatial targeting of agri-environmental measures

Agri-environmental measures (AEMs) are meant to foster environmentally-friendly farming techniques. The use of AEMs to enhance agroecosystem quality is still under debate due to site-specific spatial mismatches that often occur between adopted AEMs and delivered ecosystem services. Here, a site-specific approach was employed to assess the advantages and disadvantages of AEMs adopted from the Rural Development Programme and applied in the Veneto Region (NE Italy) during 2014-2020. Specifically, a DayCent model-GIS platform compared business-as-usual (BAU) and AEM scenarios. The effect of AEMs on ecosystem services was assessed by integrating high-resolution spatial data from multiple pedo-climates and land managements and combined agronomic and environmental outcomes. Results showed that AEM adoption generally improved ecosystem service delivery, especially by reducing water pollution and increasing soil fertility. Among simulated practices, permanent soil cover and minimum soil disturbance (i.e., conservation agriculture, pasture and meadow maintenance) produced the best results across the Veneto Region, despite compromises in agronomic performance due to AEM-specific commitments (e.g., narrow crop rotation in conservation agriculture, fertilizer use restrictions in pastures and meadows). Other AEMs (e.g., organic farming) appeared highly dependent on their spatial distribution and were influenced by a strong interaction between pedo-climatic characteristics (e.g., soil properties) and management techniques (e.g., type and quantity of nutrients input). The spatial-target approach is highly recommended to identify AEMs that achieve environmental quality objectives and develop indications as to where they should be encouraged to maximize ecosystem services delivery.

Green walls to treat kitchen greywater in urban areas: Performance from a pilot-scale experiment

An increase in water use in urban areas is forcing scientists and policy makers to find alternative solutions for freshwater management, aimed at attaining integrated water resources management. Here, we tested in a 2-year experiment (June 2017-April 2019) the treatment performance of an innovative wall cascade constructed wetland (WCCW) system. The aim was to combine the multifunctional benefits of green walls (e.g. aesthetic, surface area requirements) with those of constructed wetland systems (e.g. high pollutants removal efficiencies, water recycling) to treat kitchen greywaters. The WCCW was a terraced system of six phytoremediation lines, each of which was composed of three plastic tanks (3 × 0.04 m³), filled with lightweight porous media, and vegetated with different ornamental species, namely Mentha aquatica L., Oenanthe javanica (Blume) DC., and Lysimachia nummularia L. Physicochemical (temperature, pH, electrical conductivity, dissolved oxygen, turbidity) and chemical parameters (chemical oxygen demand, biochemical oxygen demand, anionic surfactants, Kjeldahl, ammonium and nitric nitrogen, total orthophosphate) were monitored at a frequency of at least 15 days, depending on the season and WCCW management. Results showed that the WCCW significantly reduced the main water pollutants (e.g. organic compounds, nutrients), suggesting its potential application in urban environments for water recycling in the context of green infrastructures and ecological sanitation. A culture-independent taxonomic assessment of suspended bacterial communities before and after the treatment showed clear treatment-related shifts, being the functional ecology attributes changed according to changes in greywater chemical parameters. Future research should attempt to optimize the WCCW system management by regulating the nutrients balance to avoid macronutrients deficiency, and setting the most suitable water flow dynamics (hydraulic retention time, saturation-desaturation cycles) to improve the greywater treatment.

Optimizing irrigation and determining the most sensitive development stage to drought in barley (Hordeum vulgare L.) in a semi-arid environment

Rising temperatures and increasing water scarcity, which are already important issues, are expected to intensify in the near future due to global warming. Optimizing irrigation in agriculture is a challenge. Understanding the response of crop development stages to water deficit stress provides an opportunity for optimizing irrigation. Here we studied the response of two barley varieties (Rihane, Martin), to water deficit stress at three development stages (tillering, stem elongation, and heading) by measuring water status and grain yield components in a field experiment in Tunisia. The three stages were selected due to their importance in crop growth and grain development. Water deficit stress was initiated by withholding water for 21 days at the three stages with subsequent re-watering. Water deficit led to a progressive decrease in leaf water potential. In both varieties, heading was the stage most sensitive to water deficit. Leaf water potential measurements indicated that water deficit stress was more severe during heading, which to some extent may have influenced the comparison between growth stages. During heading, the number of ears per plant and weight of a thousand grains were reduced by more than 70% and 50%, respectively compared with stress at tillering. Comparison of yield components showed differences between the two barley varieties only when the water deficit was produced during the tillering stage.

Helping stakeholders select and apply appraisal tools to mitigate soil threats: Researchers' experiences from across Europe

Soil improvement measures need to be ecologically credible, socially acceptable and economically affordable if they are to enter widespread use. However, in real world decision contexts not all measures can sufficiently meet these criteria. As such, developing, selecting and using appropriate tools to support more systematic appraisal of soil improvement measures in different decision-making contexts represents an important challenge. Tools differ in their aims, ranging from those focused on appraising issues of cost-effectiveness, wider ecosystem services impacts and adoption barriers/opportunities, to those seeking to foster participatory engagement and social learning. Despite the growing complexity of the decision-support tool landscape, comprehensive guidance for selecting tools that are best suited to appraise soil improvement measures, as well as those well-adapted to enable participatory deployment, has generally been lacking. We address this gap using the experience and survey data from an EU-funded project (RECARE: Preventing and REmediating degradation of soils in Europe through land CARE). RECARE applied different socio-cultural, biophysical and monetary appraisal tools to assess the costs, benefits and adoption of soil improvement measures across Europe. We focused on these appraisal tools and evaluated their performance against three broad attributes that gauge their differences and suitability for widespread deployment to aid stakeholder decision making in soil management. Data were collected using an online questionnaire administered to RECARE researchers. Although some tools worked better than others across case studies, the information collated was used to provide guiding strategies for choosing appropriate tools, considering resources and data availability, characterisation of uncertainty, and the purpose for which a specific soil improvement measure is being developed or promoted. This paper provides insights to others working in practical soil improvement contexts as to why getting the tools right matters. It demonstrates how use of the right tools can add value to decision-making in ameliorating soil threats, supporting the sustainable management of the services that our soil ecosystems provide.

Buffer Strips on the Low-Lying Plain of Veneto Region (Italy): Environmental Benefits and Efficient Use of Wood as an Energy Resource

Vegetated buffer strips (VBS) are recognized as a cost-effective way to reduce agricultural nonpoint-source pollution. In agroecosystems with high field fragmentation, only narrow VBS that partially compromise farmers' revenue are accepted. This study aimed to identify some ecosystem services as provided by VBS in terms of soil and water quality, and VBS performance in terms of wood for energy purposes. Buffer strip design (3 vs. 6 m wide) and composition were considered to define best practices for wood use at the farm level and for the local firewood market. Results showed that yearly wood pole production was 0.5 t 100 m, on average, ranging between a minimum of 0.22 t 100 m and a maximum of 0.72 t 100 m per row. Wood production had negligible effects on farmers' revenue. By contrast, water quality was enhanced, especially with 6-m-wide VBS. Specific subsidies for the maintenance of VBS increased total income despite a reduction in crop production (-17.5% in 6-m VBS with two rows). Subsidies might be better quantified at a site-specific level by taking into account all ecosystem services that are provided by VBS. Promising solutions to increase farmers' income are related to the wood seasoning process for firewood production; reducing the moisture content to <25% before the start of the winter season increases its market value.

Newly-established free water-surface constructed wetland to treat agricultural waters in the low-lying Venetian plain: Performance on nitrogen and phosphorus removal

Constructed wetlands offer promising solutions for controlling nutrient pollution in agricultural systems with relatively low costs and energy inputs. In mainly central and northern Italy, semi-natural and reconstructed Free-Water Surface Constructed Wetlands (FWS CWs) are designed to treat nonpoint-source pollution from agricultural catchments. However, their performance depends on system design and time of establishment. This paper evaluates the efficiency of a recently established FWS CW to remove nonpoint-source nutrient pollution due to agricultural drainage in the low-lying Venetian plain (NE Italy). The system was established in 2014 by creating five consecutive sub-basins vegetated with macrophytes to restore a semi-natural wetland, and later monitored in terms of water quality parameters and nutrients removal over three consecutive agricultural seasons (2014-2016). Total (TN) and nitrate (N-NO₃) nitrogen concentrations showed peaks (16.37 and 15.31 mg l^-1 for TN and N-NO₃, respectively) in the various sub-basins during spring 2015, associated with fertilisation of surrounding croplands and intense rain events. Performance improved over the three years, with increasing median removals of TN (33.3-49.0%) and N-NO₃ (32.2-80.5%), corresponding to average mass of 1355 kg y^-1 and 1011 kg y^-1 for TN and N-NO₃. Concentrations of ammonium (N-NH₄) and orthophosphate (P-PO₄) were generally low (<1 and <0.3 mg l^-1 for N-NH₄ and P-PO₄, respectively), with average yearly mass removals of 50 kg for N-NH₄ and 9 kg for P-PO₄. According to the overall treatment performance, the FWS CW could treat a total area of about 30 ha with a wetland/catchment ratio of 7%. However, we expect that treatment efficiency will increase as a result of bank stabilisation and improvement of the aquatic environment, together with increases in surface vegetation.

Control of Maize Vegetative and Reproductive Development, Fertility, and rRNAs Silencing by HISTONE DEACETYLASE 108

Histone deacetylases (HDACs) catalyze the removal of acetyl groups from acetylated histone tails that consequently interact more closely with DNA, leading to chromatin state refractory to transcription. Zea mays HDA108 belongs to the Rpd3/HDA1 HDAC family and is ubiquitously expressed during development. The newly isolated hda108/hda108 insertional mutant exhibited many developmental defects: significant reduction in plant height, alterations of shoot and leaf development, and alterations of inflorescence patterning and fertility. Western blot analyses and immunolocalization experiments revealed an evident increase in histone acetylation, accompanied by a marked reduction in H3K9 dimethylation, in mutant nuclei. The DNA methylation status, in the CHG sequence context, and the transcript level of ribosomal sequences were also affected in hda108 mutants, while enrichment in H3 and H4 acetylation characterizes both repetitive and nonrepetitive transcriptional up-regulated loci. RNA-Seq of both young leaf and anthers indicated that transcription factor expression is highly affected and that the pollen developmental program is disrupted in hda108 mutants. Crosses between hda108/hda108 and epiregulator mutants did not produce any double mutant progeny indicating possible genetic interactions of HDA108 with distinct epigenetic pathways. Our findings indicate that HDA108 is directly involved in regulation of maize development, fertility, and epigenetic regulation of genome activity.