Agro-industrial Composts Research Articles

Enhancing the cultivation of Salicornia fruticosa with agroindustrial compost leachates in a cascade cropping system: evaluating the impact of melatonin application.

Cascade cropping systems (CCS) utilize leachate from a primary crop to grow secondary crops and enhance the efficient use of water and fertilizers in areas with scarce water resources. A preliminary study investigated the effect of melatonin in a cascade cropping system to potentially improve plant tolerance to abiotic stresses. This study aimed to cultivate Salicornia fruticosa in this cropping system to reduce nutrient discharge and assess the impact of exogenous melatonin on Salicornia growth and quality. The CCS included a primary crop of Salicornia grown in an agro-industrial compost or peat. Leachates from these media were used to cultivate the same plant once again in a floating system under four treatments: compost leachate (T1), peat leachate (T2), 100% nutrient solution (NS) (T3), 50% NS (T4) strength. Four concentrations of exogenous melatonin were applied in foliar spray: 0, 100, 200, and 400 µM. Melatonin application increased yield, with the highest values observed when plants were grown in T1. Water use efficiency was also maximized in T1 and with both 200 and 400 µM melatonin applications. The highest nitrogen use efficiency was achieved in plants grown in peat leachate. The lipid membrane damage was assessed revealing that plants grown in compost leachate exhibited the lowest MDA values regardless of melatonin concentrations. The accumulation of some antinutritional compounds (nitrate, oxalate, and sodium) were the highest in those plants grown in compost leachate. Overall, shoots grown in peat leachate exhibited the best phytochemical profile (total phenol content, total flavonoids, and antioxidant capacity), with peak values in plants treated with 200 µM melatonin. These findings suggest that S. fruticosa can be effectively cultivated using leachate from a previous crop in a floating system and that exogenous melatonin application enhances the yield and nutritional quality of Salicornia shoots.

Potential of producing organic lettuce seedlings without peat using agricultural and agro-industrial compost

Peat is an unrenewable resource. Compost can partially replace peat in the growing seedling substrates due to its high electrical conductivity (EC), bulk density (BD), and pH. This study aimed to assess the potential of substituting peat for seedling substrate with compost made from a mixture of agricultural and agro-industrial wastes. Four compost piles (C1–C4) were constructed as follows: C1: a 1:1:1.5 weight ratio mixture of filter mud, mushroom waste, and date-palm fronds, while C2–C4: a 0.5:1 weight ratio mixture of either bagasse, cutting grassland, or date-palm fronds and cattle dung. After four months of decomposition, the compost’s physical, chemical, and biological properties were estimated in comparison to commercial compost (CC), peatmoss (PM), and their ideal ranges (IR) for seed germination and seedling growth. Composts differed significantly in their physical and chemical properties. Some composts revealed property values within the IR. In comparison to PM, Composts have a lower C/N ratio and organic matter, along with higher BD, EC, and pH. Cattle manure enhanced organic matter and carbon, total nitrogen and potassium, and ammonium levels, and reduced ash levels in C2–C4 compared to filter mud in C1. In winter 2018 and 2019, C1–C4 substrates were compared with CC and PM substrates to determine their suitability for producing crisp lettuce ‘Big Bell’ seedlings under plastic-house conditions. Substrates had significant effects on lettuce seedling traits. Shoots of C2–C4 substrate seedlings grew more rapidly than those of other substrate seedlings due to the increased length and diameter of their stem and leaf area.

Combined effect of an agro-industrial compost and light spectra composition on yield and phytochemical profile in mizuna and pak choi microgreens

This work aimed to evaluate the growth of two species of microgreens (mizuna and pak choi), using agro-industrial compost as growing media in two different mixes versus one hundred percent peat, under two different LED illumination spectra (LED 1 and LED 2) in a 14 h photoperiod. The experiment was carried-out for two times. Biomass yield, glucosinolates, and phenolic compounds, and nitrate (NO3−) content were analysed in leaf tissues. In both species, the highest fresh and dry biomass production was in compost:peat (50:50%) and LED 2 (Blue/Red/Far Red). In general, compost had a greater influence on nitrate content than light, but in the microgreen pak choi, the anthocyanin content was inhibited by the compost treatment. In the other hand both LED illumination had a positive effect on mizuna for glucosinolates and anthocyanins, and LED 2 also showed a positive effect on pak choi for anthocyanin. Therefore, the use of agri-food compost: peat (50:50%) with LED 2 (blue/red) lighting treatment to obtain microgreens in indoor crops is a plausible technology that provides nutritionally and phytochemically rich crops.

Agro-Industrial Compost in Soilless Cultivation Modulates the Vitamin C Content and Phytochemical Markers of Plant Stress in Rocket Salad (Diplotaxis tenuifolia (L.) DC.)

Rocket salad is an important vegetable for the ready-to-eat sector, normally cultivated under greenhouse conditions, either in soil or soilless systems. In the latter case, as well as in the nurseries, its cultivation is usually carried out by using peat as a growing medium—a non-renewable substrate—for which it is urgent to find a replacement. Similarly to peat, compost may be used as a growing medium; however, depending on its origin, the chemical and physical characteristics may not bet suitable for plants’ cultivation. In this study, we propose the use of agro-industrial compost as a substitute for peat for rocket salad cultivation. Plants grown in compost, alone or in combination with the second cut of rocket salad, gave better results in several biometric parameters, without negatively affecting yield and dry weight percentage. As a mechanistic approach to further understand how compost can affect plants’ stress, the qualitative profile of phytochemicals (glucosinolates and (poly)phenols)—recognized markers of biotic and abiotic plant stress—were monitored and exhibited a decreasing trend in plants grown using compost relative to those cultivated with peat. The analysis of vitamin C provided information on the achievement of an enhanced concentration by the compost, especially in the second cut. It can be inferred from the results obtained that the compost used as a growing medium may be used as a peat-free substrate for rocket crop cultivation.

Compost application in an olive grove influences nitrogen dynamics under Mediterranean conditions

Agro-industrial composts represent both a sustainable alternative to inorganic fertilizers and a waste recycling management tool. Albeit, there is still a great deal of uncertainty as to what extent their use can contribute to the global N2O budget. Here, two different composts [olive waste “alperujo” (AC) and biosolid (BC)] were tested during a three-year period to evaluate changes in N pools (NH4+ and NO3−), N2O emissions and key N-cycle associated genes [ammonia monooxygenase (amoA) and N2O reductase (nosZ)] in comparison with a control, treated only with mineral fertilization. To that end, a low dose (equivalent to 17.8 kg per tree of AC or BC) and high dose (equivalent to 26.7 kg per tree of AC+ or BC+) was applied to each individual plot composed of nine olive trees without irrigation in a completely randomized design. N2O emissions rates showed a high spatial and temporal variability and no significant changes were detected in N pools when comparing with the control. However, the fact that the soil treated with BC+ presented 20% more NO3− compared to the control after the second compost addition and that the low doses of both composts displayed about 30% less NH4+ than the control, suggests different pathways in N mineralization. Moreover, the N balance showed that soils treated with AC used all N provided and in turn promoted native N consumption while soil amended with BC only consumed part of the exogenous N provided. The assessment of the bacterial amoA and nosZ genes reflected that it was tillage practices rather than fertilization which had the most significant impact on their abundance, decreasing this effect towards the end of the experiment. Our results showed that under Mediterranean conditions the use of agro-industrial byproducts do not contribute to N2O emissions and therefore it could be potentially used as a replacement of inorganic fertilizers favouring a circular economy of zero waste.

The influence of feedstocks and additives in 23 added-value composts as a growing media component on Pythium irregulare suppressivity

Alternative materials with added-value functions, such as phytopathogen suppression and biostimulant and/or biofertilising activity, have been proposed as peat substitutes in growing media. The aim of this work was to evaluate the effect of 23 agro-industrial composts as components of growing media for baby-leaf lettuce transplant production and their activity against the plant pathogen Pythium irregulare. The composts were produced by mixing different starting feedstocks—tomato waste, leek waste, olive mill cake and vineyard pruning waste—with different additives (coffee, thyme, lavender and rockrose waste), which were incorporated at the beginning of the maturation phase. The results obtained indicated that the composts were mature enough to be used as growing media. The fresh weight of the lettuce plants grown with the different composts was significantly higher than in plants obtained with peat. Composts with the coffee additive produced higher lettuce fresh weight, while those with thyme yielded a lower fresh weight. Moreover, composts as components of growing media showed significantly higher P. irregulare suppressiveness than peat. The composts with additives produced lower lettuce fresh weight than composts without additives, but showed higher suppressiveness. Composts with additives showed opposite results depending on whether they were exposed to pathogens or not. Composts with additives showed opposite results according to pathogen pressure or not. Out of all the composts studied, the compost with tomato waste and leek waste as the initial feedstock, and lavender as an additive, showed the highest suppressive capacity. After lettuce harvesting, the growing media with composts showed significantly lower concentrations of P. irregulare than peat. Principal Component Analysis (PCA) revealed that the growing media with compost can be grouped together according to the additive type

Spraying Agro-Industrial Compost Tea on Baby Spinach Crops: Evaluation of Yield, Plant Quality and Soil Health in Field Experiments

Compost tea is a liquid fraction extracted from composts, and it is of great interest in sustainable agriculture because it reduces the unsustainable use of chemical-based pesticides and fertilizers. In this study, during two spinach field cycles, we evaluated the potential beneficial effect of the foliar application of a compost tea made from onion and vineyard composts either by itself (CT) or implemented with the beneficial microorganism Trichoderma harzianum T78 (CT + Th) on the “healthy quality” and yield of baby spinach. Results showed that both the CT and CT + Th treatments produced a higher spinach yield than the control, but these treatments did not result in an increase in soil dehydrogenase activity (DHA) or soil nutrient content. Furthermore, CT + Th treatment showed the highest yield, phenolic content, antioxidant capacity and flavonoid levels. Nitrate levels were below legal amounts, and they were significantly (p ≤ 0.05) lower in the CT and CT + Th treatments than in the control. Data suggest that compost tea extracts from onion waste and vineyard compost and/or enriched with T. harzianum can be used in a sustainable agriculture to increase yield and quality of baby spinach.

ADDITION OF BOILER CHARCOAL WASTE TO COMPOST FOR USE AS SUBSTRATE FOR VEGETABLE SEEDLINGS

ABSTRACT The recovery of waste from the broiler production chain (BPC) is consistent with the principles of a circular economy. Besides turning waste into organic compost, its use as substrate for the production of vegetable seedlings further increases its economic value. However, it is necessary to adapt its characteristics to enable its use as substrate. To this end, the addition of boiler remnant charcoal wastes (BCW), another type of waste generated in the BPC, to the organic compost resulting from the composting of BPC waste with different bulking agents (BAs) was studied. The addition of BCW to agro-industrial compost reduced the electrical conductivity (EC) of substrates. Multiple linear regression showed that, of the 13 variables (physical, chemical and physicochemical) studied, three (EC, pH and N content) are sufficient to explain the seedling quality index (SQI). Simple nonlinear regression showed that, in order to achieve higher SQIs and easier removal of clod from tray, an additional 30% in weight of BCW is required for compost, using urban tree pruning, wood sawdust and sugarcane bagasse BAs. The use of cotton and Napier grass waste as BAs is not recommended for BPC waste mixtures, as they cause a large increase in substrate EC.

An agroindustrial compost as alternative to peat for production of baby leaf red lettuce in a floating system

Peat alternatives are being developed using materials such as agroindustry compost. The aim of this work was to study whether an agroindustrial compost could be used as substitute for peat in a floating system for cultivating baby leaf red lettuce. For this, two different experiments were carried out over two growing cycles (summer and autumn) in the same greenhouse at the same time. The first experiment compared the two organic substrates (peat and compost) and the second involved a suppressive bioassay using both substrates inoculated with Pythium irregulare. The results showed that compost increased the percentage of seed germination and the quality of baby leaf red lettuce by reducing nitrate accumulation and increasing the antioxidant capacity and vitamin C content of leaves compared with peat. Furthermore, under P. irregulare pressure plants grown in compost showed less incidence of the disease (a higher percentage of plant survival) and produced higher yields. It is concluded that the agroindustrial compost used in this study shows promise as an alternative to peat for use as organic substrate in a sustainable soilless production system for baby leaf red lettuce, since it is not only able to control the effect of P. irregulare, but also improve the yield and quality of the product.

Agroindustrial compost as a peat alternative in the horticultural industry of Ecuador

This work was conducted in order to investigate the possibility of using different agroindustrial composts in the production of horticultural seedlings, thereby replacing part of the peat in the growing media. Three vegetable species differing in salt sensitivity - tomato (Solanum lycopersicum L. var. Malpica) (the least sensitive), courgette (Cucurbita pepo L. var. Mastil F1) (moderately sensitive) and pepper (Capsicum annuum L. var. Largo de Reus Pairal) (the most sensitive) - were grown in nine media containing three composts, prepared by co-composting vegetable waste (flower, broccoli or tomato waste) with laying hen manure and sawdust, as well as peat in various ratios. The proportions of the three composts in the mixtures elaborated with peat were 25%, 50% and 75% (v/v). A substrate of 100% peat was used as control. The experiment was arranged in a completely-randomised design, with two replicates per treatment, under greenhouse conditions. Prior to sowing, some physical, physico-chemical and chemical properties of the growing media were determined and the seed germination and fresh and dry weights of the aerial parts and roots of the seedlings were also measured, as well as the mineral composition of the aerial parts of the plants.In most cases, the addition of compost to the growing media produced an increase in the pH, salt content and macronutrient concentrations, in comparison to peat, whereas the physical properties of the compost based-substrates had values very similar to those of an ideal substrate. Also, multivariate analysis showed that the media prepared with flower waste compost, at all concentrations, and the medium with tomato waste compost at 25% were the most suitable substrates for the three plant species tested.

Fecal sludge-derived pellet fertilizer in maize cultivation

Fecal sludge (FS) contains significant amounts of plant nutrients and organic matter although it also contains pathogens. Therefore, FS can be used as fertilizer after proper sanitization. This study was designed to test dried fecal sludge (DFS)-based pellet fertilizers on maize cultivation. The DFS fertilizers were produced by composting, co-composting with sawdust, or irradiated by gamma-irradiation, and then nitrogen-enriched and pelletized using gelatinized or gamma-irradiated cassava starch. These DFS pellet fertilizers were compared to each other and to no-fertilization, mineral fertilizer, and agro-industrial waste compost. The fertilizer applications were 150 or 210 kgN/ha. Maize was cultivated in pots containing Cambisol and Ferric Lixisol growth media. The EC-SDFS-PG pellet (DFS + sawdust co-composted, enriched with nitrogen and pelletized) at a rate of 210 kgN/ha produced the highest maize yield (4.4 ton/ha) among all other treatments, while mineral fertilizer produced 3.9 ton/ha. It is concluded that the EC-SDFS-PG pellet produces similar or higher maize yields than mineral fertilizer and more than the agro-industrial compost in both growth media types.

Identification of predictor parameters to determine agro-industrial compost suppressiveness against Fusarium oxysporum and Phytophthora capsici diseases in muskmelon and pepper seedlings.

The lack of reliable prediction tools for evaluation of the level and specificity of compost suppressiveness limits its application. In our study, different chemical, biological and microbiological parameters were used to evaluate their potential use as a predictor parameter for the suppressive effect of composts against Fusarium oxysporum f. sp. melonis (FOM) and Phytophthora capsici (P. capsici) in muskmelon and pepper seedlings respectively. Composts were obtained from artichoke sludge, chopped vineyard pruning waste and various agro-industrial wastes (C1: blanched artichokes; C2: garlic waste; C3: dry olive cake). Compost C3 proved to offer the highest level of resistance against FOM, and compost C2 the highest level of resistance against P. capsici. Analysis of phospholipid fatty acids isolated from compost revealed that the three composts showed different microbial community structures. Protease, NAGase and chitinase activities were significantly higher in compost C3, as was dehydrogenase activity in compost C2. The use of specific parameters such as general (dehydrogenase activity) and specific enzymatic activities (protease, NAGase and chitinase activities) may be useful to predict compost suppressiveness against both pathogens. The selection of raw materials for agro-industrial composts is important in controlling Fusarium wilt and Phytophthora root rot.

Biological control of plant pathogens by microorganisms isolated from agro-industrial composts

Plant diseases caused by pathogenic bacteria and fungi are a severe problem for Mediterranean agriculture and some composts have shown a suppressive capacity due to the antagonistic action of microbial communities inhabiting those substrates. The purpose of this work was to isolate and identify those microorganisms from agro-industrial waste-based compost able to antagonize Xanthomonas campestris and Fusarium oxysporum f.sp. melonis, two devastating phytopathogens in the Southeast of Spain. To this end, a collection of 135 strains comprising bacteria, actinobacteria and fungi was isolated and their suppressiveness tested in vitro. Those strains with the best inhibition indexes were selected for in vivo tests.While performing in vitro assays, half of the tested strains were effective only against F. oxysporum f.sp. melonis, less than a 4% of the tested strains only antagonized X. campestris and eight strains were noticed to be antagonists against both phytopathogens. In vivo assays were performed using five strains selected because of their higher inhibition indexes and identified by molecular methods as Acetobacter indonesiensis, Bacillus pumilus, Paecilomyces variotii, Streptomyces griseus and Acremonium chrysogenum. Additional assays were carried out to check the plants health status in the absence of pathogens so as to discard possible damaged caused by those five biocontrol agents. The in vivo tests succeeded in pointing out P. variotii as a broad spectrum biocontrol agent effective against both bacterial spot of tomato and fusarium wilt of melon.

The potential of near infrared reflectance spectroscopy (NIRS) for the estimation of agroindustrial compost quality

Composting is an environmentally friendly alternative for the recycling of organic wastes and its use is increasing in recent years. An exhaustive monitoring of the composting process and of the final compost characteristics is necessary to certify that the values of compost characteristics are within the limits established by the legislation in order to obtain a safe and marketable product. The analysis of these parameters on each composting batch in the commercial composting plant is time-consuming and expensive. So, their estimation in the composting facilities based on the use of near infrared reflectance spectroscopy (NIRS) could be an interesting approach in order to monitor compost quality. In this study, more than 300 samples from 20 different composting procedures were used to calibrate and validate the NIRS estimation of compost properties (pH, electrical conductivity (EC), total organic matter (TOM), total organic carbon (TOC), total nitrogen (TN) and C/N ratio, macronutrient contents (N, P, K) and potentially pollutant element concentrations (Fe, Cu, Mn and Zn)). The composts used were elaborated using different organic wastes from agroindustrial activities (GS: grape stalk; EGM: exhausted grape marc; GM: grape marc; V: vinasse; CJW: citrus juice waste; Alpeorujo: olive-oil waste; AS: almond skin; EP: exhausted peat; TSW: tomato soup waste; SMS: spent mushroom substrate) co-composted with manures (CM: cattle manure; PM: poultry manure) or urban wastes (SS: sewage sludge) The estimation results showed that the NIRS technique needs to be fitted to each element and property, using specific spectrum transformations, in order to achieve an acceptable accuracy in the prediction. However, excellent prediction results were obtained for TOM and TOC, successful calibrations for pH, EC, Fe and Mn, and moderately successful estimations for TN, C/N ratio, P, K, Cu and Zn.