Vermicompost and millicompost as a resource in sustainable agriculture in semiarid: decomposition, nutrient release, and microstructure under the action of nitrogen and organic-mineral fertilizers.

With the expansion of organic agriculture, research is needed to indicate economically and ecologically viable fertilizer options, especially in semiarid regions, with low soil organic matter and nitrogen content. In the Brazilian semiarid region, vermicomposts are widely used by farmers and are scientifically investigated; however, there is no information for millicompost, a new type of organic compound that has shown very promising results in other regions. Thus, this study aimed to analyze the decomposition rate, nutrient release, and microstructure evaluation of vermicomposts from different sources and of millicompost produced from plant residues, with the application of mineral nitrogen-urea and organo-mineral fertilizer in the Brazilian semiarid region. The experimental design was a randomized block in a 4 × 3 factorial scheme, with four replicates; four organic composts (millicompost, commercial vermicompost, vermicompost from bovine manure, vermicompost from goat manure); and three types of fertilization (without fertilizer, with mineral-urea and organo-mineral fertilizer). The organic composts were decomposed using litterbags at the soil surface. The variable's decomposition rate and the nutrient release were evaluated at six-time intervals (0, 30, 60, 90, 120, and 150 days), and microstructure was evaluated at the beginning and the end of the experiment, with scanning electron microscopy (SEM). The highest decomposition was verified for commercial vermicompost rich in macro and micronutrients and with lower P contents. The lignin:N ratio and the initial P content were more important in the permanence of the organic compost in the field than the C:N ratio. Regardless of the organic composts, the use of urea as a mineral fertilizer stimulated decomposition more than the organo-mineral fertilizer. The initial composition of the nutrients was decisive in the dynamics of nutrient release, mass loss, and decomposition of C. There was no pattern in the release order of macronutrients. However, for the micronutrients, the release order was Cu > Fe > Mn, in all treatments. Microstructure analysis is a visual analysis where differences are detected through microphotographs and the biggest difference occurred with millicompost, which showed elongated fibers and fiber bundles, forming a relatively open structure characteristic of the presence of fulvic acid. However, the addition of organo-mineral fertilizer formed agglomerates in compacted micro-portions, helping the mineralization of C and N.

Evaluation of the consumption of agricultural and urban waste by the diplopod Trigoniulus corallinus as a strategy for formulating new combinations for the millicomposting process.

This study aimed to measure the consumption of different types of plant waste by the diplopod species Trigoniulus corallinus, in order to determine which would be the most suitable for the millicomposting process. To this end, a waste consumption experiment was carried out in the laboratory, using a completely randomized experimental design with 15 replicates and 13 organic residues from different sources. After 10 days, the following parameters were evaluated: dry mass of the waste used to feed the diplopods, dry mass of the fecal pellets, and diplopod mortality. Significant differences were observed in the consumption rates of the diplopods in the different treatments, with the highest rates being observed for Mimosa caesalpiniifolia, with 44.49%, followed by Gliricidia sepium chips, with 38.24%. The highest values for pellet mass were obtained from the decomposition of Mimosa caesalpiniifolia litter (0.891 g). The treatment with Syngonium auritum shavings showed 93% mortality after consumption, followed by the treatment with Heliconia psittacorum shavings, which showed 53%. Both species are ornamental and widely found in gardens and backyards. The diplopods have a preference for Mimosa caesalpiniifolia litter and Gliricidia sepium shavings. There is limited consumption of ornamental plant waste, with reports of toxicity to other organisms. Based on these results, a mixture of waste will be tested for millicomposting in urban farming areas that excludes toxic plants.

Effect of the application of vermicompost and millicompost humic acids about the soybean microbiome under water restriction conditions.

Humic substances (HSs) are constituent fractions of organic matter and are highly complex and biologically active. These substances include humic acids (HA), fulvic acids (FA), and humin. HS are known to stimulate the root system and plant growth and to mitigate stress damage, including hydric stress. Humic acids have already been reported to increase microbial growth, affecting their beneficial effect on plants. However, there is scarce information on whether HA from vermicompost and millicompost, along with Bradyrhizobium, improves the tolerance of soybean to water restriction. This study aimed to evaluate the responses of soybean plants to the application of vermicompost HA (HA-V) and millicompost (HA-M) along with Bradyrhizobium sp. under water restriction. The experiment was carried out in a greenhouse, and the treatments received Bradyrhizobium sp. inoculation with or without the application of HA from vermicompost and millicompost with or without water restriction. The results showed that HA provided greater soybean growth and nodulation than the control. The application of HA-M stimulated an increase in the richness of bacterial species in roots compared to the other treatments. After the application of water stress, the difference between the treatments disappeared. Microbial taxa were differentially abundant in plants, with the fungal fraction most affected by HA application in stressed roots. HA-V appears to be more prominent in inducing taxa under stress conditions. Although the results showed slight differences between HA from vermicompost and millicompost regarding plant growth, both humic acids promoted an increase in plant development compared to the control.