RESUMO
This study aimed to determine the effects of the nitrogen (N) application period and level on the fate of fertilizer N and the contribution of N absorption and translocation to apple organ N. Two N application periods (labeled by the 15N tracer technique in spring and summer, represented by SP and SU, respectively) and three N levels (N0, MN, and HN) were used to determine the physiological indexes and aboveground, root, and soil 15N content of 4-year-old dwarf ('Red Fuji'/M9T337) and arborized ('Red Fuji'/Malus hupehensis Rehd.) apple trees. The results showed that HN led to shoot overgrowth, which was not conducive to the growth of the apple root system (root length, root tips, root surface area, and root volume) or the improvement of root activity. The contribution of soil N to apple organ N accounted for more than 50%, and the contribution of N application in summer to fruit N was higher than that in spring. Under HN treatment, the proportion of soil N absorbed by trees decreased, while that of fertilizer N increased; however, the highest proportion was still less than 50%, so apple trees were highly dependent on soil N. Under MN treatment, fertilizer N residue was similar to soil N consumption, and soil N fertility maintained a basic balance. Under HN treatment, fertilizer N residue was significantly higher than soil N consumption, indicating that excessive N application increased fertilizer N residue in the soil. Overall, the 15N utilization rate of arborized trees (17.33-22.38%) was higher than that of dwarf trees (12.89-16.91%). A total of 12.89-22.38% of fertilizer 15N was absorbed by trees, 30.37-35.41% of fertilizer 15N remained in the soil, and 44.65-54.46% of fertilizer 15N was lost. The 15N utilization rate and 15N residual rate of summer N application were higher than those of spring N application, and the 15N loss rate was lower than that of spring N application. High microbial biomass N (MBN) may be one of the reasons for the high N utilization rate and the low loss rate of N application in summer.
RESUMO
BACKGROUND: The crab processing industry has generated a considerable quantity of by-products, and these untapped residues resulted in environmental problem and waste of natural resources. Therefore, the purpose of this research was to evaluate the further usage potential of Ovalipes punctatus extract. The proximate composition, minerals, fatty acids, amino acids, tasty components (free amino acid, flavour 5'-nucleotides, glycine betaine and inorganic ions) and volatile flavour components were studied. RESULTS: O. punctatus extract was found to have a high protein (31.2 g kg⻹), but a low fat content (0.13 g kg⻹). The protein contained high amounts of arginine (110.2 g kg⻹ protein) and glutamic acid (108.9 g kg⻹). The fatty acid profiles were dominated by saturated fatty acids, while C20 n-3 and n-6 fatty acids accounted for 85% of its polyunsaturated fatty acids. Arginine, alanine, glycine, glycine betaine, glutamic acid and chloridion (taste active value greater than 1) were primary taste-active components. A total of 77 volatiles were identified, and benzaldehyde and pyrazines were the major flavour contributors to the aroma of O. punctatus extract. Furthermore, sensory evaluation with a five-point hedonic scale showed that the overall flavour of O. punctatus extract had high acceptance. CONCLUSION: Results presented in this study indicated that O. punctatus extract could be utilised to produce nutritious food or value-added products.