High-quality Soil Research Articles

Assessing the bioenergy potential of abandoned cropland in China: Toward an optimal distribution of bioenergy crops

Bioenergy has gained wide attention due to its potential to reduce fossil fuel consumption and greenhouse gas emissions. Abandoned cropland is a promising option for cultivating bioenergy crops, as it does not compete with food production. The vast amount of abandoned cropland in China provides extensive opportunities for the development of bioenergy. However, the bioenergy potential of China's abandoned cropland remains unclear. In this study, we identified abandoned cropland in China for the period of 2000–2020. Based on this, we estimated the bioenergy potential from conventional food crops (maize and wheat), and perennial bioenergy crops (miscanthus and switchgrass), on the abandoned cropland in China. We optimized the planting of conventional food and two perennial bioenergy crops by maximizing crop yield and accounting for water limits. The results show that 29.49 Mha of abandoned cropland was found in the past twenty years. Spatially, it was mainly located in eastern China with relatively high soil quality, in contrast to that in the U.S. and Europe. By optimizing the crop distribution on abandoned cropland, the bioenergy potential primarily shows a spatial distribution of higher potential in the south and lower potential in the north, with a total yield reaching 9.52 EJ. This is approximately 1.43 times higher than that of solely cultivating miscanthus and 8.28 times that of wheat. This potential accounts for 6 % of China's total primary energy consumption in 2022 and 7.66 % of the carbon emission peak target for 2030. It holds significant importance for the national emission reduction strategy. These findings highlight the immense bioenergy potential of abandoned cropland, providing support for the development of bioenergy.

Metal-modified biochars prepared from blue algae and their ability of adsorbing phosphates from water and utilization as soil amendment

The problem of blue algae accumulation can be alleviated by utilizing blue algae as biomass for resource utilization, which can remove excess phosphates from water to alleviate eutrophication. Herein, Magnesium (Mg) and/or lanthanum (La) were used to modify biochar via high-temperature slow pyrolysis with blue algae as the raw biomass. These modified biochars exhibited abundant carbon (18.0%-50.3%), oxygen content (17.4%-49.1%), along with a high specific surface area (82.26-233.80 m2/g). The surface of metal-modified biochar was enriched with hydroxyl and carboxyl groups and metal elements were efficiently incorporated into biochars. Adsorption kinetic and isotherm experiments were conducted under the optimal pyrolysis temperature of 600 °C, pH of 6.0, and adsorbent dosage of 2.0g/L. The adsorption kinetics studies by metal-modified biochars for phosphate fitted well pseudo-second-order model Redlich-Peterson isotherm model. Biochar modified by Mg and La exhibited the highest removal efficiency (97.8%) for phosphate at adsorption equilibrium. The adsorption mechanism involved the electrostatic interaction between hydroxylated metal oxides and negatively charged phosphate ions and the precipitation of phosphate ions through chemical reactions with metal oxides in the solution. After phosphate adsorption, the pristine and metal-modified biochars derived from blue algae were applied as the soil amendment. Biochar adsorbed phosphate apparently improved the germination rate of seeds facilitated the height, width, weight, and chlorophyll content of vegetable seedlings, and induced oxidative stress, which proved that the biochar recovered after adsorption was a high-quality soil amendment. This study provides a new approach for the treatment of phosphate wastewater and the algae application.

Soil fertility and plant nutrition in an organic olive orchard after 5 years of amendment with compost, biochar or their blend

The agronomic use of compost and biochar as soil amendments may exhibit contrasting results in terms of soil fertility and plant nutrition. The effects of the biennial application of biochar, compost and a blend of compost:biochar (90:10; % dw:dw) on the agronomical performance of an organically managed and well established 25-year-old olive orchard was assessed 5 years after the initial application. The agronomical evaluation was based on the assessment of the soil physical, chemical, and biological characteristics, and the assessment of the soil fertility by both crop production and nutritional status of the orchard, and the bioassay with olive plantlets. Biochar mainly benefited the physical properties (bulk density, total porosity, aeration, water retention capacity) of soil, especially in the top 0–5 cm. Compost and its blend with biochar improved microbial activity, soil nutritional status (increasing the content of soluble organic C, N, and P) and favoured the formation of aggregates in soil. The bioassay conducted with young plantlets confirmed the enhanced soil fertility status in the three amended treatments, particularly in the case of biochar and its blend with compost. However, this effect was not significantly observed in the adult plants after 5 years of application, reflecting the slow response of adult olive trees to changes in fertilization. Based on these results, alongside the desirable long-residence time of biochar in soil and the ready availability of compost, the blend of biochar with compost assayed in this study is defined as a valid strategy for preparing high quality soil organic amendments.

Agrivoltaics in Germany - Status Quo and Future Developments

Ground-mounted photovoltaic facilities in open spaces have been common in Germany for many years. However, according to the legislation, these are only supported by the government on poorer quality soils, former military training areas, or along traffic routes. Nevertheless, also on high quality soils it is not forbidden to install ground-mounted photovoltaic facilities. In recent years, Germany has started implementing agrivoltaics, which is an alternative land use concept that combines agriculture and renewable energy production. This opens the possibility to use land of higher soil quality for energy generation without necessarily creating land-use conflicts and being subsidized by the government. This study aims to provide a comprehensive overview of existing and planned agrivoltaic facilities in Germany analyzing them based on various parameters. The data for this study was collected through a community questionnaire and supplemented with data from state institutions. The results indicate that as of March 2023, 21 agrivoltaic facilities with a total capacity of 81.67 MWp have been installed. A strong increase of the installed capacity is expected in 2023 and 2024, reaching approximately 382.59 MWP by the end of 2024. The market development of agrivoltaics is mainly driven by changes in the legal environment which present opportunities for further market ramp-up of agrivoltaics. The adoption of agrivoltaics shows a notable spatial diversity in Germany which appears to be influenced by the interaction between regulatory environments and agricultural structures.

Geoinformatics-Based Mapping of Environmental Sensitive Areas for Desertification over Satara and Sangli Districts of Maharashtra, India

Desertification processes in arid, semi-arid, and dry sub-humid conditions have been enhanced in recent decades. The geospatial database and associated satellite data can be effectively employed for regional planning to address desertification and land degradation. In this study, the Mediterranean Desertification and Land Use (MEDALUS) model has been used to map environmentally sensitive areas due to desertification in the Satara and Sangli districts of Maharashtra, India. This was achieved by combining Landsat-8 multispectral data, Census data, soil data, and climatic variables like temperature, rainfall, and evapotranspiration. The algorithm of MEDALUS is the geometric mean of four indicators, namely soil quality index (SQI), climate quality index (CQI), vegetation quality index (VQI), and socio-economic quality index (SEQI). The findings indicated that the majority of the study area comes under the potential category of desertification (60.32%) followed by fragile (27.87%) and critical (11.81%). Areas with a high propensity for desertification were found over the low to very low climatic quality and moderate to high soil quality including lower socio-economic quality. The lower socio-economic quality is mainly due to high to very high population density (>100 people/km2), low to moderate illiteracy rate (<16%), and low to moderate work participation rate (<50%) that incentivize unsustainable land use practices. The study provides a valuable tool for understanding and managing natural resources. It offers a detailed analysis of the environmental sensitivity of the study area, taking into account various factors like land use, vegetation cover, slope, and soil erosion potential. The developed comprehensive map of the area helps in identifying the most sensitive regions and developing appropriate conservation strategies. The information obtained from the study can be utilized to develop and implement successful measures to prevent or alleviate desertification, which is crucial for sustaining the health of ecosystems and the welfare of local residents.

Assessing inconsistencies in historical land-use reconstructions for Africa at 1800

Reconstructing historical land-use and land-cover change (LULCC) inevitably involves interpolation across regions for which there is limited data to support reconstructions. Here, we evaluate the extent to which the global land-use model HYDE v3.2.1 reflects historical land use in sub-Saharan Africa (including Madagascar) when compared to archaeological and historical reconstructions. Both the HYDE models and Widgren’s archaeological and historical reconstructions estimate that agriculture was widely scattered across sub-Saharan Africa in 1800 CE. However, in steep terrain, at slopes greater than 10°, the HYDE model estimated 0% cropland allocation while archaeological and historical observations suggest intensive, mixed and extensive farming was common in these areas. In addition, while HYDE allocates farmland primarily into high-quality soils, archaeological reconstructions suggest that intensive farming occurred across a wide range of soil qualities. Gaps in our knowledge of cropland distribution have significant impacts on models of biodiversity change since understanding biodiversity in the Anthropocene is reliant on our understanding of past land-use changes. While HYDE’s mismatches are known, the research presented here provides an important resource in identifying where these allocation rules fail. These mismatches in global land-use models such as HYDE might also be replicated for other regions of the world, such as South America. These mismatches also need to be accounted for when generating model projections that use historical land-use models to impute present and future trends in land-use, climate and biodiversity change. Localised archaeological and historical data can therefore be used to support historical global land-use reconstructions for Africa and other regions across the world.

Effect of Biochar, Potting Mixture and their Blends to Improve Ocimum basilicum Growth in Sandy Soil

Biochar has received significant interest as a soil amendment but its relative performance to addition of high-quality soil is not well assessed. This study compared different loadings of cabbage-waste biochar produced at 360 °C against potting mixture (PM) as amendments to enhance basil (Ocimum basilicum) growth in sandy soil. Pot tests for six conditions of biochar, PM or their blend were tested at both 2% or 6% loading, plus a control, with soil and plant characteristics monitored. The combination of 6% biochar and 6% PM increased seed germination by 85% compared to the control, while 6% biochar applied in sandy soil reduced seed germination by 29%. However, significant benefits were realized later in the growing stage in comparison to the control and most other tested conditions. The 6% application of biochar to the soil enhanced leaf chlorophyll and carotenoid contents, membrane stability index, and leaf relative water content by 198%, 150%, 15%, and 5% over the control, respectively. The highest shoot and total biomass were achieved with the combined application of 6% biochar and PM, followed by 6% biochar only. When comparing only application of biochar or PM, biochar was the more favorable soil amendment at both 2% and 6% loadings. Biochar was also effective at enhancing plant uptake of beneficial nutrients, while immobilizing Al, which is detrimental, in the soil. Overall, biochar is a better soil amendment for sandy soil than equivalent quantities of PM, but mild benefits occur through their combined application.

Subsurface organic amendment of a saline soil increases ecosystem multifunctionality and sunflower yield

Salt stress poses a growing constraint to crop productivity in arid regions globally. Previous evidence indicates that organic amendment is a pivotal management practice for enhancing crop yield and soil fertility in agroecosystems. How organic amendment depth influences the interaction between soil health, ecosystem multifunctionality (EMF), and crop yield, however, still remains unclear. Thus, a 3-year field experiment was carried out to investigate the impacts of surface (0–15 cm) and subsurface (15–30 cm) applications of humic acid and manure on the soil quality index (SQI), enzyme activities, EMF, and crop yield on saline soils. Subsurface organic amendment improved the SQI (at the 0–45 cm layers) by 20–47 %, while the surface amendment improved the SQI at the 0–30 cm layer by 15–51 %. The higher soil quality under subsurface organic amendment was characterized by increases in soil organic carbon and available nutrients, and a decrease in electrical conductivity compared to surface organic amendment. The organic amendment increased microbial diversity and richness, stimulated enzyme activities, and ultimately improved soil EMF. The soil EMF increased by 122–214 % at the 0–30 cm layer under subsurface organic amendment and by only 178 % at the 0–15 cm layer under surface organic amendment. Pairwise comparisons further confirmed that electrical conductivity was negatively, and soil organic carbon positively, correlated with soil ecological functions within the 0–45 cm layer. The higher soil quality and microenvironment with better EMF under subsurface organic amendment increased sunflower yield by 16 % and 8 % as compared to inorganic fertilizer only and surface organic amendment, respectively. This relates to the considerable improvement in soil electrical conductivity, soil organic carbon, β-glucosidase activity, and diversity and richness of microbial communities resulting from deep organic amendment. Overall, subsurface organic amendment is an effective way to enhance soil EMF and crop yield on saline soils.

Microbial electrochemical composting: A sustainable strategy to enhance lignocellulose conversion into humus

Achieving satisfactory levels of humification during composting is recognised as a challenge due to the recalcitrance of lignocellulose and the uncertainty of current biofortification techniques. Therefore, a novel microbial electrochemical composting technology was developed from insights into microbiology and electrochemistry in this study to strengthen microorganisms’ function promoting the conversion from lignocellulose into humus. Firstly, a fungus (Aspergillus oryzae) was introduced which exhibited a higher propagation rate (29.9%) and secreted more lignocellulose-degrading enzymes (18.9–74.9%) under electric field assistance. Subsequently, an in-situ composting trial was conducted with supplementary electric fields simultaneously combined with Aspergillus oryzae inoculation. The abundance of Aspergillus oryzae increased 3.0–7.8-fold under the influence of electric field, which enabled the production of more extracellular enzymes (by 8.4–149.5%) to promote the conversion of lignocellulose to humus (increased by 7.0–20.2%). The results indicated electric field can act as an activator of Aspergillus oryzae and magnify its function. It provides an innovative and efficient technique for enhancing humification during composting that contributes to the conversion of organic waste into high-quality soil conditioner products.

Quality of Soils in Soybean Producing Areas in Caraga Region

This study aims to determine the soil quality of selected soybean producing farms in the Caraga region using soil quality index (SQI) measurements. Five sites were selected in the municipalities of San Miguel, Surigao del Sur and Trento, Agusan del Sur. Three 10×10 m soil monitoring plots were established within soybean fields in each site. Within each monitoring plot, three composite samples were collected coming from 10 subsamples using a soil probe. SQI was calculated following three general steps, (1) selection of minimum dataset (MDS) via Principal Components Analysis (PCA), (2) Scoring of MDS via linear method, and (3) Calculation of weighted overall SQI. Out of the 16-soil property indicator, a total of five soil properties (exchangeable Ca, % Sand, Electrical conductivity, available P, and Soil respiration) were extracted and used as the MDS for the calculation of SQI in each site. The main indicator properties for determining the quality of the soils in the area were Exchangeable Ca and % Sand contents offering a 68% and 26% weights over other soil properties, respectively. High SQI classification was found on four out of five sites evaluated, these were the two sites in the Municipality of Trento (Cebolin.M (61%) & Cebolin.T (54%)) and two sites in the Municipality of San Miguel (Libag-Gua (68%) & Upper Carromata (93%)). One site in San Miguel revealed a low SQI (Lower Carromata (41%)). These SQI values indicate that in these areas, soils with very high Exchangeable Ca and Sand content could have a low-quality condition, and sites with optimal Exchangeable Ca (400 - 600 ppm) contents and loamy to sandy loam texture could be classified as high quality soils. Proper drainage system could be best done to manage the very high exchangeable Ca content in these soil and thus, could improve its quality.

Ecological plasticity and sustainability of cotton in the Southern Steppe of Ukraine

Depending on the length of the cotton growing season, the area of cultivation and its highest productivity potential are determined, and the prompt ripening of raw cotton allows for home-grown harvesting and high-quality soil preparation. The purpose of this study was to identify samples adapted to the conditions of the Southern Steppe of Ukraine from the cotton gene pool. The study used methods of plant variety expertise: phenological observations, morphological studies, and evaluation of breeding material for valuable traits. Based on the study results, parental components were selected to expand the process of forming early-ripening forms and productivity of raw cotton. The ability of cotton plants to grow in extreme conditions of the Southern Steppe of Ukraine was assessed and its homogeneity or stability, the index of growing conditions, the coefficient of variation – the difference in the numerical values of the trait duration of the period “germination – beginning of flowering” of plants in varieties with different growing season and their fluctuations around the average value were determined. It was found that according to the determined plasticity (bi), the variance of stability (Si2), and the coefficient of variation of the duration of “germination – the beginning of flowering” higher tolerance to environmental factors was characterised by ultra-early ripening varieties. The average regression coefficient (bi ) was -0.36; the variation in the duration of the period by year was 10.1%, which is significantly lower compared to early-ripening varieties – -0.77% and 12.9%, mid-ripening varieties – -0.80% and 15.0%, and late-ripening varieties – -1.30% and 16.6%, respectively. The maximum average productivity to frosty raw cotton of 49.4 g/plant was formed by the sample Pidozerskyi 4 (UF0800003), the duration of the period “germination – beginning of flowering” was 47 days, and “germination – full ripening” – <103 days. The lowest raw cotton productivity of 21.2 g/plant was demonstrated by the late-ripening sample Joloten 32 (IU14056549) of Turkmen selection, the duration of the growing season of which was 145 days on average over the years of research. The findings of this study will be used in further breeding to create high-yielding cotton varieties with increased environmental plasticity and stability and highquality fibre

Qualitative soil quality assessment is efficient in a grazing system with or without trees.

Soil quality (SQ) assessment is affected by methods that convert data sets into indices, and such analyses are expensive and time-consuming. Qualitative SQ assessments are faster and cheaper than quantitative methods and they can be repeated to monitor SQ in crop and pasture systems. We evaluated SQ using qualitative and quantitative SQ indicators of two grazing systems under Voisin rational grazing (VRG) with trees (WT) or without trees (NT). We took an adjacent native forest as a reference and we used principal component analysis (PCA) to compare the accuracy of the assessment methods. According to the set of indicators used for quantitative assessment, the WT system and the Forest had higher SQ than other systems as a result of higher values of soil physical and chemical indicators. This the reflected better performance of soil in functions related to structural support, nutrient cycling and biological productivity. According to the set of indicators used for qualitative assessment, the WT system showed better SQ than the NT areas because of the higher scores of all indicators and better performance of the soil functions, and those values were close to the Forest in the indicators. PCA applied to integrate the data of qualitative and quantitative indicators indicated that SQ in WT was similar to Forest. The qualitative evaluation was as efficient as the quantitative evaluation for SQ assessment in VRG areas with and without trees. Its use can promote farmers' autonomy and the development of skills to identify environmental factors that help to evaluate their practices. © 2023 Society of Chemical Industry.

Application of life cycle assessment to high quality-soil conditioner production from biowaste

The recent large-scale urbanization and industrialization resulted in an impressive growth of solid waste generation worldwide. Organic fraction generally constitutes a large fraction of municipal solid waste and its peculiar chemical properties open to various valorization strategies. On this purpose, life cycle assessment is applied to an innovative industrial system that processes 18 kt/y of agricultural and livestock waste into a high-quality soil conditioner. The high-quality soil conditioner production system consists of a series of processes, including anaerobic digestion and vermicomposting, allowing the generation of a peat-like material with high carbon content, porosity, and water-holding capacity. The presence of a photovoltaic plant and a cogeneration plant, fed with the biogas produced in the anaerobic digestion, makes the system entirely self-sufficient from the national grid and generating a surplus of electricity of 1177MWh/y. The high-quality soil conditioner showed better environmental performances in 15 out of 18 impact categories when compared to alternative scenarios. In particular, the high-quality soil conditioner and the related biowaste management resulted in a carbon saving of around 397 kg CO2 eq/ton compared with a scenario involving the employment of peat in place of the high-quality soil conditioner and a traditional biowaste management, and 165 kg CO2 eq/ton compared with a scenario where cogeneration is replaced by biomethane upgrading. This study demonstrates the possibility of using organic waste as an environmentally sustainable and renewable source for energy and carbon to soil conditioning.

Application Rates of Cricket Feces Influencing Soil Properties and Rice Yield in Soils of Different Moisture Contents

Background: Cricket feces is a potential high-quality soil amendment, but there is currently no established optimum rate for its application in paddy soils with varying moisture contents. This study therefore aimed to evaluate the effects of varied rates of cricket feces on soil properties, rice growth, and yield in paddy soils with differing moisture contents. Methods: Two study factors were evaluated: (i) the maximum water-holding capacity (WHCmax) and flooded soils, and (ii) cricket feces applied at rates of 0 (unamended), 3.125 (low), 6.25 (medium), and 12.5 (high) t/ha. Result: The total grain weight of rice in soil with WHCmax was 2.60, 4.33, 6.91, and 7.49 g/hill under the cricket feces from unamended to high rates, respectively, with no significant difference between the medium and high rates. Meanwhile, the total grain weight in flooded soil was 1.85, 4.02, 4.70, and 5.72 g/hill, respectively. Cricket feces increased the content of essential elements and decreased the acidity and toxicity of Al, Ca, and Na in the soil, thereby promoting rice growth and yield. The optimal application rates of cricket feces for rice in the WHCmax soil was determined to be the medium rate, while that in flooded soil was the high rate.

Long-term application of controlled-release fertilizer enhances rice production and soil quality under non-flooded plastic film mulching cultivation conditions

Agricultural practices that integrate plastic film mulching (PM) cultivation and controlled-release urea have been widely used to conserve water and increase crop yields. The interactive responses of rice productivity and soil quality to long-term plastic film mulching cultivation and controlled-release urea have not yet been comprehensively elucidated, and whether or not plastic film mulching cultivation combined with controlled-release urea is suitable for rice production remains unclear. A 12-year field experiment with two water regimes (continuously flooded [CF] and PM) and three nitrogen (N) fertilization treatments (no N fertilizer, urea, and controlled-release urea) was conducted to explore the long-term effects on rice yield, soil physicochemical and biological properties, and soil quality in a single rice cropping system. Compared to continuously flooded system, the plastic film mulching system maintained rice productivity (CF: 6.9 t ha−1; PM: 7.1 t ha−1) with higher water productivity (CF: 0.9 g L−1; PM: 2.0 g L−1). Controlled-release urea treatments improved rice yield by 11.9% and 44.6% compared to treatments with urea and no N fertilizer, respectively. Random forest analysis indicated that enzyme activity was the main factor affecting rice yield. Compared to continuously flooded system, the plastic film mulching system significantly increased soil pH by 3.4% and decreased soil organic matter content by 9.3%. Moreover, the plastic film mulching system exhibited significantly higher enzyme activity than the continuously flooded system. Principal coordinate analysis of enzyme activities showed that N fertilization influenced enzyme activities considerably more than water regime. According to Pearson’s analysis, soil fungal alpha diversity was more sensitive to soil physicochemical properties than bacterial alpha diversity. Overall, treatment with controlled-release urea in the plastic film mulching system resulted in the highest soil quality index values, which were positively correlated with rice yield (R2 = 0.61, p = 0.000). The positive direct effects induced by continuously flooded cultivation (i.e., satisfying the water requirements of rice) were counterbalanced by the negative indirect effects of altered enzyme activity. The N fertilizer type indirectly influenced rice yield by altering soil nutrients, enzyme activity, and microbial diversity. Therefore, controlled-release urea could maintain rice production with high soil quality under non-flooded plastic film mulching cultivation conditions.

Carbon Storage in Cropland Soils: Insights from Iowa, United States

The restoration of soil organic matter (SOM, as measured by soil organic carbon (SOC)) within the world’s agricultural soils is imperative to sustaining crop production and restoring other ecosystem services. We compiled long-term studies on the effect of management practices on SOC from Iowa, USA—an agricultural region with relatively high-quality soil data—to highlight constraints on detecting changes in SOC and inform research needed to improve SOC measurement and management. We found that strip-tillage and no-tillage increased SOC by 0.25–0.43 Mg C ha−1 yr−1 compared to losses of 0.24 to 0.46 Mg C ha−1 yr−1 with more intensive tillage methods. The conversion of cropland to perennial grassland increased SOC by 0.21–0.74 Mg C ha−1 yr−1. However, diversifying crop rotations with extended rotations, and supplementing synthetic fertilizer with animal manure, had highly variable and inconsistent effects on SOC. The improved prediction of changes in SOC requires: the use of methods that can identify and disentangle multiple sources of variability; looking beyond total SOC and toward systematic collection of data on more responsive and functionally relevant fractions; whole-profile SOC monitoring; monitoring SOC in long-term studies on the effect of multiple conservation practices used in combination; and deeper collaboration between field soil scientists and modelers.

Steps to circularity: Impact of resource recovery and urban agriculture in Seattle and Tacoma, Washington

Capturing the value in urban residuals (food scraps and wastewater) is a critical component of urban sustainability and a circular nutrient economy. Food production in urban areas has also been recognized as an important component of urban health. Data from two cities (Seattle and Tacoma, WA) with active resource recovery and community garden programs were used to quantify nutrient recovery and food production potential. Yield data from growth trials conducted using soil amendments produced from locally generated organic residuals were used to model yields in existing urban agriculture programs. Our survey showed much lower than expected volume of food scraps from both residential and multifamily housing for both cities. Nutrient generation rates from food scraps were estimated as 0.55–0.67 kg N and 0.09–0.11 kg P capita−1 yr−1. Recovery rates for Seattle with an established food scrap collection program were 0.21 kg N and 0.006 kg P capita−1 yr−1. Nutrient recovery from wastewater biosolids was higher; 1–1.67 kg N and 0.23–0.76 kg P capita−1 yr−1. Data on effluent quantity and nutrient concentrations from these programs suggests that effluent has a high potential for nutrient recovery (4.03–5 kg N and 0.3–0.5 kg P capita yr−1). Yield was modeled for kale (brassica oleracea) considering the number of people that could be fed per hectare for one year using a 67 g portion by comparing yields from synthetic fertilizer and residuals-based amendments in both high and low quality urban soils. The Tacoma biosolids potting soil yielded enough for 310 and 736 people ha−1 yr−1 for the high and low quality soils, respectively. The modeled food/yard compost produced from the food scraps yielded sufficient kale for 148 to 353 people ha−1 yr−1. Relative yield from fertilizer for the low and high quality soils was 15 and 263 people ha−1yr−1, respectively. Considering yield, enough biosolids are produced to meet 6.7–29.2% of the vegetable needs of each city. These results suggest that significant nutrients can be recovered using existing infrastructure. With enhanced nutrient capture from wastewater effluent, sufficient nutrients could be recovered to meet the N and P needs for food crops for the residents of each city.

A multi-data approach to evaluate progress towards land degradation neutrality in Central Asia

Central Asia hosts one of the largest continuous grassland areas on our planet, that is of vital importance for food security, biodiversity and carbon sequestration. However, this region is also subjected to some of the most intense land degradation processes, related to large scale land use change and climate change.To combat land degradation and pursue sustainable land management the concept of land degradation neutrality (LDN) has been proposed. LDN assessments are recommended to be based on global data in regions that lack sufficient regional data such as Central Asia. However, it remains unclear how the selection of datasets influences the estimated extent of land degradation. We followed the LDN framework and first calculated changes to three LDN indicators: land productivity, land cover, and Soil Organic Carbon (SOC). We then evaluated the impact of using different regional and global land cover data on the extent of land degradation in the region. Finally, we calculated a regionally specific integrated indicator on soil quality that we used to assess the “like-for-like” principle which enables counterbalancing losses and gains.Our results indicate that particularly the selection of land cover data has a significant impact on the overall assessment of degradation state. The extent of land between 2000 and 2019 varies considerably depending on the data and ranges between 15 and 34 % of the whole Central Asian region. Our findings reveal that the area of degraded land on high quality soils is twice as high as the area of high quality soils where the land condition has improved (12 % versus 6 %). In areas with low soil quality, 13 % was subject to degradation, and 10 % improved.Whilst the degradation extent varies according to the selected land cover datasets, our results demonstrates that Central Asia is undergoing land degradation affecting high quality soils. Sensitivity analysis of multiple datasets can reduce the risk of misjudgement in degradation extent assessments, especially in regions with mosaic ecosystems, such as grasslands.

Recent developments in soil law and policy in New Zealand

New Zealand has a reputation for successful and efficient agricultural production, although it has a limited supply of high-quality versatile soils. These valuable resources are under threat, both from natural forces including extreme weather events, and from the pressures of expanding urban growth into adjacent areas of high-quality soils. In this article recent developments in the legal and policy framework for soils in New Zealand are considered, and in particular the effect of the National Policy Statement for Highly Productive Land 2022 (‘NPS-HPL’). Recent caselaw involving residential and urban expansion into rural areas, often to the detriment of the continued availability of high-quality soils, will also be examined. The significant effects of recent extreme weather events in New Zealand on soil issues and productive land will be discussed, and some observations made on the lessons that can be learnt as we face increasing impacts from climate change. Finally, some comments will be offered on future developments, including proposed major resource management legislative reforms, in the context of soil law and policy in New Zealand.

The Practice and Development of T-Bar Penetrometer Tests in Offshore Engineering Investigation: A Comprehensive Review

In recent years, the development of marine hydrocarbon resources has led to an increased demand for research on the marine soil bearing capacity and cyclic loading effect in marine engineering design. Because of the difficulties and high costs involved in obtaining high-quality soil samples from offshore sites, in situ testing techniques have become the preferred method of determining design parameters in offshore geotechnical engineering projects. This paper provides a review of the current state of marine penetrometer deployment technology used in offshore engineering investigations and presents a summary of the T-bar penetrometer test for measuring marine soft clay. The existing literature research on penetration mechanisms, numerical simulations, laboratory experiments, and field tests of the T-bar penetrometer in the field of marine geotechnical engineering are analyzed. Finally, the potential difficulties, challenges, and prospects of the T-bar penetrometer tests are discussed.