Organic materials and their humic substances as sources of free and immobilized enzymes for soils and plants

[SPA] El principal desafío de los países mediterráneos es restaurar la fertilidad y productividad de sus suelos agrícolas degradados ubicados en zonas áridas y semiáridas, mediante la adición de materia orgánica exógena (enmienda orgánica), consiguiendo así frenar los procesos de degradación y desertificación, e incentivado la introducción de C exógeno en el suelo que será capaz de aumentar la calidad biológica, bioquímica y microbiológica del mencionado suelo. Con la materia orgánica exógena añadida al suelo, basada en muchas ocasiones en residuos orgánicos que sean de calidad, se incluyen sustratos que pueden incentivar la síntesis de algunas enzimas, y por esta razón, los ciclos de elementos como C, N, P o S, consiguiendo así aumentar la fertilidad del suelo y su productividad. El uso de residuos orgánicos (posiblemente tratados) procedentes de origen animal, vegetal o incluso urbano (lodos de depuradora) representa un "valor añadido" para los suelos donde se adicionan, tanto desde el punto de vista económico como ecológico. El objetivo de la presente Tesis Doctoral es el estudio de residuos orgánicos sin estabilizar o estabilizados mediante compostaje, y su valorización desde diferentes puntos de vista: i) como fuente de enzima total de interés en los ciclos de elementos; ii) como fuente de enzimas inmovilizadas en las sustancias húmicas, quedando por tanto dichas enzimas estabilizadas y resistentes a la desnaturalización térmica, iii) conocer el efecto de las diferentes enmiendas orgánicas estudiadas (basadas en residuos orgánicos de diferente origen: urbano, animal o vegetal), sobre la calidad bioquímica, biológica y microbiológica de los suelos degradados donde se adicionan; iv) determinar los cambios de tipo químico estructural de las sustancias húmicas (ácidos húmicos y ácidos fúlvicos) obtenidas de los suelos degradados cuando son enmendados con materiales orgánicos, v) por el efecto sobre el crecimiento de las raíces de las plantas de maíz, debido a las sustancias húmicas del suelo modificado, con esto los desechos orgánicos. La presente Tesis Doctoral se compone de 5 experimentos correspondientes a los objetivos mencionados.[ENG] The objectives of this study are to compare the biochemical responses of soil microorganisms to different organic amendments and doses and the dynamics of humic-enzyme complexes versus total enzyme activity. The experiment was carried out under laboratory conditions using soil microcosms (500 g) amended with two different doses (5 and 10g) of different materials during 360 days: sewage sludge from a wastewater treatment plant (SS), compost from that sludge (CSS), the organic fraction of municipal solid wastes (MSW), and compost from MSW (CMSW). The different carbon fractions, such as the total organic carbon (TOC), water-soluble carbon (WSC), and microbial biomass carbon (MBC), increased compared to the control soil without amendment, as well as dehydrogenase and hydrolytic enzymes (β-glucosidase and urease) activities. The immobilized enzymes in the soil humic extracts exhibited different behaviors compared to total activity, depending on the origin of the organic material which suggest neo-formation of humic-enzyme complexes.Universidad Politécnica de CartagenaPrograma de doctorado en Técnicas Avanzadas en Investigación y Desarrollo Agrario y Alimentari

From Lab to Field: Role of Humic Substances Under Open-Field and Greenhouse Conditions as Biostimulant and Biocontrol Agent

The demand for biostimulants has been growing at an annual rate of 10 and 12.4% in Europe and Northern America, respectively. The beneficial effects of humic substances (HS) as biostimulants of plant growth have been well-known since the 1980s, and they can be supportive to a circular economy if they are extracted from different renewable resources of organic matter including harvest residues, wastewater, sewage sludge, and manure. This paper presents an overview of the scientific outputs on application methods of HS in different conditions. Firstly, the functionality of HS in the primary and secondary metabolism under stressed and non-stressed cropping conditions is discussed along with crop protection against pathogens. Secondly, the advantages and limitations of five different types of HS application under open-fields and greenhouse conditions are described. Key factors, such as the chemical structure of HS, application method, optimal rate, and field circumstances, play a crucial role in enhancing plant growth by HS treatment as a biostimulant. If we can get a better grip on these factors, HS has the potential to become a part of circular agriculture.</p

How Does Maize-Cowpea Intercropping Maximize Land Use and Economic Return? A Field Trial in Bangladesh

Cultivating multiple crops together can provide numerous benefits, including improved soil health and crop yield. The objective of our study was to determine the optimum planting techniques in intercropping systems, and to maximize their benefits by mitigating competition for resources such as land, space, light interception, and nutrition. The performance of successively planted maize (Zea mays L.) grown with cowpea (Vigna unguiculata L.) was evaluated with a field trial in Bangladesh. The treatments in our study were: (a) sole maize, (b) sole cowpea, (c) crops sown simultaneously, and (d) crops sown with different time lags (1, 2, and 3 weeks) between the maize-sowing and cowpea-sowing dates. Data on the crops&rsquo; physiological parameters were recorded. These included light interception, leaf area index (LAI), Soil Plant Analysis Development (SPAD), harvest index, and yield. Simultaneously, canopy coverage was measured using camera-based photo analysis. In addition, an economic analysis of intercropping maize with soybean or cowpea was conducted using gross margin analysis and benefit-cost ratio. In our results, the below-canopy photosynthetically active radiation (PAR) was significantly higher in intercropping treatments when maize was sown three weeks after cowpea. In contrast, the LAI value of the maize and cowpea was significantly greater when sown on the same day than in other intercropping treatments. As a result, the maize yield reduced when intercropped with cowpea. This reduction maximized when both species were sown simultaneously due to higher competition for resources, including nutrients and light. Intercropping was more beneficial in terms of land equivalent ratio than both sole cropping of maize and cowpea, especially when maize was planted three weeks later. However, this benefit was not retained when calculated as maize equivalent yield since the contribution of cowpea was small in the overall maize yield, suggesting the importance of the relative economic value of the component species. Among all treatments, the lowest maize equivalent yield (6.03 &plusmn; 0.14 t ha&minus;1) was obtained from sole cowpea, and the largest land equivalent ratio (1.67 &plusmn; 0.05) was obtained from intercropping with maize sown three weeks after cowpea. This treatment provided a net income of USD 786.32 &plusmn; 25.08 ha&minus;1. This study has shown that together, maize&ndash;cowpea intercropping with a temporal niche difference of three weeks may be a better option for sustainable crop production in Bangladesh, maximizing land use. However, it may not provide a significantly greater maize equivalent yield and economic return

Efecto de la aplicación de compost en las fracciones de carbono y humificación del suelo en una finca ecológica frutícola

Las sustancias húmicas del suelo se consideran la parte más recalcitrante y estable de la materia orgánica del suelo (MOS) y contribuyen a la sostenibilidad agrícola a largo plazo mediante el aumento de la productividad de los cultivos y la fertilidad del suelo. En este trabajo, se evaluó la influencia del manejo orgánico del suelo durante 5 años sobre el ciclo del carbono y la estructura química de los ácidos húmicos del suelo agrícola. El experimento se realizó con dos enmiendas diferentes: i) la incorporación de los residuos vegetales o biomasa del cultivo, producidos dentro de la parcela (hojarasca, residuos de poda y siega de la hierba), (S+V) y ii) la aplicación de estiércol compostado además de la incorporación de la vegetación espontánea y restos de poda (S+V+C). Después de 5 años, en relación a la influencia sobre la calidad del suelo y el ciclo del carbono, el aporte continuado con compost muestra un aumento en el contenido de materia orgánica (de 0,95% a 2,46%) así como de la fracción de carbono soluble en agua (47%). Con respecto a las características de los ácidos húmicos del suelo el 1º y 5º año, analizados con resonancia magnética nuclear de 13C (13C-RMN), se muestra una evolución de la estructura hacIa formas más estables en ambos suelos (S+V y S+V+C), debido al proceso de biodegradación y humificación de la materia orgánica. Especialmente el aumento de grupos funcionales en el complejo húmico tipo grupos aromáticos y carboxílicos, reforzando el carácter recalcitrante de los ácidos húmicos, se observa más claramente en los suelos tratados con compost (S+V+C). La aplicación de compost mejora a largo plazo la fertilidad del suelo.Soil humic acid fraction is regarded as the most-recalcitrant and stable part of the soil organic matter (SOM) that contributes to long-term agricultural sustainability by increasing crop productivity and soil fertility. The our study was conducted to evaluate influence of organic soil managements over 5 years on carbon cycle and chemical structure of soil humic acid. Plot experiment was done with two different amendments : i) the incorporation of residue from the inherent vegetal materials, produced inside the plot (leaf litter, pruning residue, and cutting grass after mowing), (S+V) and ii) the application of composted manure in addition to the incorporation of the inherent vegetal materials (S+V+C). After 5 years, Concerning to the influences on the soil quality and soil carbon cycles by the continuous compost treatment, the increase of organic matter content (0.95%-2.46%) and water soluble C fraction (47%) were shown. Regarding to the study of soil humic acids characteristics over 5 years with 13C nuclear magnetic resonance (13C-NMR), gradual reformation of more stable structure were shown in both soils (S+V and S+V+C), due to the selective biodegradation and humification process after the amendments. Especially, the increase in functional groups in the humic complex such as aromatic and carboxylic groups, reinforcing the recalcitrant character of humic acid were observed more clearly in the soil treated with compost application (S+V+C). The continuous compost application to orchard soils in the long-term improved soil fertility.A1 Sistemas de producción de base agroecológica (Trabajos científicos).Facultad de Ciencias Agrarias y Forestale

Efecto de la aplicación de compost en las fracciones de carbono y humificación del suelo en una finca ecológica frutícola

Las sustancias húmicas del suelo se consideran la parte más recalcitrante y estable de la materia orgánica del suelo (MOS) y contribuyen a la sostenibilidad agrícola a largo plazo mediante el aumento de la productividad de los cultivos y la fertilidad del suelo. En este trabajo, se evaluó la influencia del manejo orgánico del suelo durante 5 años sobre el ciclo del carbono y la estructura química de los ácidos húmicos del suelo agrícola. El experimento se realizó con dos enmiendas diferentes: i) la incorporación de los residuos vegetales o biomasa del cultivo, producidos dentro de la parcela (hojarasca, residuos de poda y siega de la hierba), (S+V) y ii) la aplicación de estiércol compostado además de la incorporación de la vegetación espontánea y restos de poda (S+V+C). Después de 5 años, en relación a la influencia sobre la calidad del suelo y el ciclo del carbono, el aporte continuado con compost muestra un aumento en el contenido de materia orgánica (de 0,95% a 2,46%) así como de la fracción de carbono soluble en agua (47%). Con respecto a las características de los ácidos húmicos del suelo el 1º y 5º año, analizados con resonancia magnética nuclear de 13C (13C-RMN), se muestra una evolución de la estructura hacIa formas más estables en ambos suelos (S+V y S+V+C), debido al proceso de biodegradación y humificación de la materia orgánica. Especialmente el aumento de grupos funcionales en el complejo húmico tipo grupos aromáticos y carboxílicos, reforzando el carácter recalcitrante de los ácidos húmicos, se observa más claramente en los suelos tratados con compost (S+V+C). La aplicación de compost mejora a largo plazo la fertilidad del suelo.Soil humic acid fraction is regarded as the most-recalcitrant and stable part of the soil organic matter (SOM) that contributes to long-term agricultural sustainability by increasing crop productivity and soil fertility. The our study was conducted to evaluate influence of organic soil managements over 5 years on carbon cycle and chemical structure of soil humic acid. Plot experiment was done with two different amendments : i) the incorporation of residue from the inherent vegetal materials, produced inside the plot (leaf litter, pruning residue, and cutting grass after mowing), (S+V) and ii) the application of composted manure in addition to the incorporation of the inherent vegetal materials (S+V+C). After 5 years, Concerning to the influences on the soil quality and soil carbon cycles by the continuous compost treatment, the increase of organic matter content (0.95%-2.46%) and water soluble C fraction (47%) were shown. Regarding to the study of soil humic acids characteristics over 5 years with 13C nuclear magnetic resonance (13C-NMR), gradual reformation of more stable structure were shown in both soils (S+V and S+V+C), due to the selective biodegradation and humification process after the amendments. Especially, the increase in functional groups in the humic complex such as aromatic and carboxylic groups, reinforcing the recalcitrant character of humic acid were observed more clearly in the soil treated with compost application (S+V+C). The continuous compost application to orchard soils in the long-term improved soil fertility.A1 Sistemas de producción de base agroecológica (Trabajos científicos).Facultad de Ciencias Agrarias y Forestale

Interaction between humic substances and plant hormones for phosphorous acquisition

Phosphorus (P) deficiency is a major constraint in highly weathered tropical soils. Although phosphorous rock reserves may last for several hundred years, there exists an urgent need to research efficient P management for sustainable agriculture. Plant hormones play an important role in regulating plant growth, development, and reproduction. Humic substances (HS) are not only considered an essential component of soil organic carbon (SOC), but also well known as a biostimulant which can perform phytohormone-like activities to induce nutrient uptake. This review paper presents an overview of the scientific outputs in the relationship between HS and plant hormones. Special attention will be paid to the interaction between HS and plant hormones for nutrient uptake under P-deficient conditions.</p

Unmanned Aerial Vehicle (UAV) for Detection and Prediction of Damage Caused by Potato Cyst Nematode G. pallida on Selected Potato Cultivars

High population densities of the potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis cause substantial yield losses to potato production (Solanum tuberosum) due to the delay caused to tuber formation by the retardation of plant growth. It requires meticulous estimation of the population densities by using soil sampling and applying the right combination of nematode management to deal with the PCN problem. This study aims to assess the use of an unmanned vehicle (UAV) in detecting and estimating the effect of ranges of densities of a PCN, G. pallida, on four cultivated potato cultivars with resistance to PCN in a naturally infested potato field in The Netherlands. First, the initial population density (Pi) of G. pallida was estimated by using an intensive sampling method of collecting about 1.5 kg of soil per m2 from the center of each 3 &times; 5 m plot. At harvest, the fresh tuber yield of the potato cultivars (Avarna, Fontane, Sarion, and Serresta) were assessed. The Seinhorst yield loss model was used to investigate the relationship between Pi and fresh tuber yield. Secondly, the spatial data of UAV with optical and thermal sensors were analyzed to find any relationship between Pi and UAV indices. By using the classical yield loss model, all four cultivars were found to be affected by Pi with a relative minimum fresh tuber yield m, which ranged from 0.26 to 0.40. The maximum fresh tuber yield varied from 49.48 to 80.36 tons (ha)&minus;1. The density at which the fresh tuber yield started to deteriorate was in the range of 0.62&ndash;2.16 eggs (g dry soil)&minus;1. A regression was observed between Pi, and all UAV indices in a similar pattern to that of the fresh tuber yield by using the Seinhorst yield loss model, except for the cultivar Avarna for the two UAV indices (NDRE and NDVI). Unlike the tolerance limit, the relative minimum values of the UAV indices&mdash;except the chlorophyll index&mdash;differ when compared among each other and when compared with that of the fresh tuber yield within the same cultivar. This indicates that all indices can be useful for detection and decision making for statutory purposes but not for estimating damage (except the chlorophyll index)

Comparative Assessment of Biochar Stability Using Multiple Indicators

Biochar application is one strategy proposed to improve carbon sequestration in soil. Maintaining high carbon content in soil for a long period requires stable biochar. In this work, we assessed biochar stability by two methodologies, i.e., laboratory incubation and chemical oxidation. Biochar was produced at four different temperatures (400 &#176;C, 500 &#176;C, 600 &#176;C, and 800 &#176;C) from rice (Oryza sativa L.) straw and husk, applewood branch (Malus pumila), and oak (Quercus serrata Murray) residues. Results showed that the high-temperature biochars were more stable in both abiotic and biotic incubations, whereas the low-temperature biochars had reduced longevity. In addition, we showed biochars originated from woody material have higher stable carbon than those produced from rice residues. Finally, the oxidative assessment method provided a more reliable estimation of stability than the biotic incubation method and showed a strong correlation with other stability indicators

Innovative feasibility study for the reclamation of the cascajo wetlands in Peru utilizing sustainable technologies

Wetlands are an important feature for our society that provides versatile benefits, such as habitat for diverse wildlife, shoreline erosion protection, flood control, and mitigation of climate change through capture and storage of carbon. The aim of this work was to assess the application of nanotechnologies for the restoration of the water quality in the CascajoWetlands, Peru, where the water quality was deteriorated. Ceramic-based bio-filters (CBBFs) were used to reduce and buffer the contamination rates of pollutants, whereas micro-nano bubbles (MNBs) were applied to increase the dissolved oxygen and release free radicals in water. Additionally, bio-fence was implemented to prevent water intrusion from the ocean. Remote sensing data through the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) was used to monitor the water surface condition. With treatment of CBBFs and MNBs for 13 months, we observed reduction in the chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), and total phosphate (TP) in the water body, showing removal percentages of 98.5%, 97.5%, 98.1%, 98.5%, and 94.6%, respectively, in comparison with values before starting the implementation. The trends of NDVI and EVI over seasons are not completely aligned with the results taken from the wetlands treated with MNBs, CBBFs and bio-fence. While TN was highly correlated with the empirical value of TN based on remote sensing, no correlation was observed between COD and empirical COD. The use of eco-friendly techniques has performed efficiently to remove the pollutant.</p

Exploring the Influence of Work Integration Social Enterprises on Consumers through Differentiated Customer Value Proposition

In the endeavour towards an inclusive society, work integration social enterprises (WISEs) play an important role in workplaces and labour market. Customers of WISEs are an underexplored field, and thus, this study looked at the influence of WISEs on customers using the concept of customer value. It deployed qualitative and quantitative study of two cases of WISEs in the Dutch agriculture and food industry. Market basket analysis was conducted to find interactions between customer characteristics and customer values. The results of our study show that taste as a functional value is a minimum requirement as well as a unique selling proposition for these two cases. The fact that they are a WISE was presented at different explicitness levels to customers: sometimes with a direct statement, other times with a phrase or visual hinting at this social aspect. Customers not always received this message or misinterpreted it as the WISEs intended. The results also indicate that products from these two cases are not associated with lower quality despite findings by earlier studies on socially oriented organisations. However, it is yet to be explored how the general Dutch population perceives the products and services of WISEs