Onion biomass monitoring using UAV-based RGB imaging

Biomass monitoring is one of the main pillars of precision farm management as it involves deeper knowledge about pest and weed status, soil quality, water stress, and yield prediction, among others. This research focuses on estimating crop biomass from high-resolution red, green, blue imaging obtained with an unmanned aerial vehicle. Onion, as one of the most cultivated vegetables, was studied for two seasons under non-controlled conditions in two commercial plots. Green canopy cover, crop height, and canopy volume (V_canopy) were the predictor variables extracted from the geomatic products. Strong relationships were found between V_canopy and dry leaf biomass and dry bulb biomass. Adjusted coefficient of determination (\({\text{R}}_{\text{adj}}^2\)) values were 0.76 and 0.95, respectively. Nevertheless, crop management practices and leaf depletion at vegetative stages significantly affect the accuracy of the canopy model. These results suggested that obtaining biomass using aerial images are a good alternative to other sensors and platforms as they have high spatial and temporal resolution to perform high-quality biomass monitoring.     

Structure-function relationship of vermicompost humic fractions for use in agriculture

Purpose

The use of humic substances (HS) in agriculture is beneficial and has positive environmental impacts. However, to optimize the use of HS possible links between their structural characteristics and bioactivity must be shown. The goal of this study is to evaluate the bioactivity of different humic fractions extracted from vermicompost (VC) in rice plants and to shed light to possible structure-function relationships.

Materials and methods

Humic-like fractions were obtained from cattle manure vermicompost processed by African nightcrawlers (Eudrilus eugeniae spp.). Humic-like acid fraction using only water as extractor (HLAw), HLA fraction extracted following the International Humic Substances Society (IHSS) recommended method, and the solid residue (humified residual (HR)) after extraction of HLA were characterized using complementary chemical, physic, and spectroscopic technics (elemental composition, UV-Vis and Fourier transform infrared spectroscopy (FTIR) spectroscopies, ¹³C-CP MAS NMR, and MEV). Biological activity of the three HS was conducted in growth chambers and measured in roots using WinRhizo Arabidopsis software. Principal component analysis (PCA) was used to find a grouping pattern between the structural variables evaluated and the obtained root parameters.

Results and discussion

Differences were found in elemental composition among HS with larger C/N ratio in HR than in HLA and HLAw. HLA and HLAw FTIR spectra showed carboxyl band at 1714.66 cm^?1 better resolved than in HR. Bands at 1642 cm^?1 (amide I) and 1510 cm^?1 (lignin), were better resolved in HLA. ¹³C-NMR showed the following order of aromaticity: HLA > HLAw > HR. For HLAw bioactivity, the structures C_Alkyl-H,R, C_C=O, and C_COO-H,R correlated with the number and growth of smaller root. The aromatic C_Ar-H,R, C_Ar-O,N, and aliphatic C_Alkyl-O,N, C_Alkyl-O, and C_Alkyl-di-O structures in HLA, correlated with larger roots growth. HR also stimulated root growth and development in rice plants.

Conclusions

Aliphatic and oxygenated structures in HLAw showed a relation with induction of initial root emissions, whereas the presence of aromatic compounds in HLA was related with root growth stimulation activity. Higher concentration of HLAw was necessary to produce an equivalent stimulus compared with HLA; it could indicate that, although both fractions showed similar types of structures in their composition, differences in the predominant structures may be determining different effects on the root.

     

Cover Crops as Affecting Soil Chemical and Physical Properties and Development of Upland Rice and Soybean Cultivated in Rotation

Cover crops can provide changes in soil chemical and physical properties, which could allow a sustainable development of soybean and upland rice rotation in Brazilian Cerrado. The objective of this study was to determine the effects of cover crops(cultivated in the offseason) in the soybean-upland rice rotation(cultivated in the summer season) on the soil chemical and physical properties, yield components and grain yield of the cash crops. The experimental design was a randomized block design in factorial scheme 4 × 2 with six replications. Treatments were composed by four cover crops: fallow, millet(Pennisetum glaucum) + Crotalaria ochroleuca, millet + pigeon pea(Cajanus cajans), and millet + pigeon pea + Urochola ruziziensis in the offseason with one or two cycles of cover crops, with rice(Oryza sativa)or soybean(Glycine max) in the summer season. Cover crops alone provided no changes in soil chemical properties. However, the rotation cover crops/cash crops/cover crops/cash crops reduced p H, Al and H + Al and increased Ca, Mg, K and Fe contents in the soil. The cover crops millet + pigeon pea and millet + pigeon pea + U. ruziziensis improved soil physical properties in relation to fallow,especially in the 0–0.10 m soil layer. In spite of the improvement of the soil physical properties after two years of rotation with cover crops and cash crops, the soil physical quality was still below the recommended level, showing values of macroporosity, S index and soil aeration capacity lower than 0.10 m3/m3, 0.035 and 0.34, respectively. Upland rice production was higher under mixtures of cover crops than under fallow, mainly because of soil physical changes done by these mixtures of cover crops.Soybean grain yield was similar under all cover crops tested, but was higher after the rotation cover crops/upland rice/cover crops than after only one cycle of cover crops.     

Prebiotic,probiotic, and synbiotic in the diet of Nile tilapia post-larvae during the sex reversal phase

This study evaluated the use of the prebiotic Active-MOS® (mannanoligosaccharides—Biorigin®) and two probiotics: PAS-TR® (Bacillus subtilis and Bacillus cereus var. toyoi—Imeve®) and Bioplus 2BC® (1.6 × 10¹⁰ UFC g^?1 de Bacillus subtilis and 1.6 × 10¹⁰ UFC g^?1 Bacillus licheniformis—Christian Hansen®) tested separately and together, in the diet of Nile tilapia post-larvae during the sex reversal phase. The experiment was conducted in two stages: (i) a total of 2160 3-day-old post-larvae (PL) (10.39 ± 0.85 mm and 12.28 ± 3.15 mg) were used and distributed in 24 tanks of 40 L each (3.0 PL L^?1). Growth performance, chemical analysis of carcass, bacterial recovery, and histomorphometry of intestinal villi were evaluated; (ii) 240 tilapia (4.28 ± 0.19 cm and 1.19 ± 0.09 g) from the previous experiment were used and stocked at 10 PL per aquarium. The parameters evaluated were survival and relative protection level after bacterial challenge against Aeromonas hydrophila. Six treatments with four replications in a completely randomized design were used for both experimental stages. Additives in the diet of tilapia post-larvae did not determine significant differences in growth, survival, microbiological, or histomorphometric parameters in this study. Nevertheless, after the experimental infection, advantages on the use of the additives were observed in terms of higher relative protection levels (38.10%) and relative percent survival in fish receiving Active-MOS® + Bioplus 2BC®. Therefore, we recommend the use of synbiotic (Active-MOS® + Bioplus 2BC®) in the farming of Nile tilapia PL with recurrent outbreaks of bacterial diseases during the sex reversal phase.     

<Emphasis Type="Italic">Aloysia triphylla</Emphasis> in the zebrafish food: effects on physiology,behavior, and growth performance

Dietary supplements are commonly used by animals and humans and play key roles in diverse systems, such as the immune and reproductive systems, and in metabolism. Essential oils (EOs), which are natural substances, have potential for use in food supplementation; however, their effects on organisms remain to be elucidated. Here, we examine the effects of dietary Aloysia triphylla EO supplementation on zebrafish behavior, metabolism, stress response, and growth performance. We show that fish fed diets containing A. triphylla EO presented an anxiolytic response, with reduced exploratory activity and oxygen consumption; no changes were observed in neuroendocrine stress axis functioning and growth was not impaired. Taken together, these results suggest that the A. triphylla EO supplementation is a strong candidate for use in feed, since it ensures fish welfare (anxiolytic behavior) with decreased oxygen consumption. This makes it suitable for use in high-density production systems without causing damage to the neuroendocrine stress axis and without growth performance being impaired.     

Morpho‐demographic traits of two maërl‐forming algae in beds with different depths and fishing histories

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Effect of diet on growth and body biochemical composition of juvenile four‐sided sea cucumber Isostichopus badionotus (Selenka, 1867)

The farming of sea cucumber is a growing industry that demands feeds that are tailored to the organism's nutritional needs. Therefore, in this study, the effect of diet composition, with and without additives, on the growth, survival, specific growth rate (SGR) and body biochemical composition of the four‐sided sea cucumber Isostichopus badionotus was evaluated over a period of 3 months. Four diets were used: D1 (Macrocystis sp. and Sargassum sp.), D2 (Macrocystis sp. and Spirulina sp.), D3 (Sargassum sp. and Spirulina sp.) and D4 (Macrocystis sp., Sargassum sp. and Spirulina sp.), and the same diets enriched with 0.22% of Algamac 2000^® (D1H, D2H, D3H and D4H) were also tested. The organisms fed the diets containing Spirulina sp. demonstrated the highest growth rates and significantly greater SGR (% per day) (p < .05), an effect that was enhanced by the food additive (D2 0.67%; D2H 0.78%; D3H 0.76%). Survival and body composition were not affected by diet type. Based on these results, the use of Spirulina sp. combined with supplements rich in PUFA content is recommended in the formulation of diets to promote the growth of I. badionotus juvenile.     

Oxytetracycline depletion and withdrawal time estimation following intraperitoneal administration in three species from Chilean salmon farming

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