Effect of almond shell addition to substrates in Phaseolus vulgaris L. (cv. Saxa) growth, and physiological and biochemical characteristics

Abstract

Purpose In the almond industry, the major by-product is the shell, the woody outer layer of the almond fruits. The goal of this research was to study the consequence of the incorporation of almond shell to cultivation substrates on green bean plant grown in a growth chamber. Methods Almond shell was mixed with peat (20%:80%) (AS), or used as mulch (AM) on top of the control (C) substrate (33.3%:66.6% vermiculite and peat). Evaluated parameters included green bean pod production and characteristics and their biochemical parameters, namely pigments, total phenolics and antioxidant activity, and soluble sugars and proteins, but also leaf gas exchange parameters. Results The use of almond shell as a mulch resulted in unexpected higher crop growth rate, relative leaf growth rate, and leaf area index, with similar production and dimension of pods, when compared to the control assay, with comparable amounts of phenolic compounds, antioxidant capacity, and soluble sugars and proteins, even if gas exchange parameters were negatively affected. By other hand, the data from the almond shell:peat mixture indicate important increase of carotenoid content, contrasting to the control substrate. Conclusion These results indicate that almond shell has some potential as growing medium for green bean cultivation, when mixed with peat or used as a mulch.

Almond By-Products Substrates as Sustainable Amendments for Green Bean Cultivation

“…These differences were attributed to the substrate effect ( p (S) < 0.001). This is contrary to the results obtained by Oliveira et al (2019) [ 35 ], who obtained significant differences in the values of photosynthetic pigments presented by green bean pods from distinct substrates. However, the results obtained in our study were notably higher than those obtained by these authors for all types of pigments evaluated.…”

“…Looking at Figure 5 D, it can be seen that the lowest protein content was obtained in pods from the MIX100 substrate (3.439 ± 0.001 mg BSA g −1 FW), but the substrates AH100 (5.609 ± 0.977 mg BSA g −1 FW), AH50 (5.846 ± 0.360 mg BSA g −1 FW), and MIX50 (4.994 ± 0.621 mg BSA g −1 FW) presented values comparable to the C100 (5.926 ± 0.152 mg BSA g −1 FW) and to C50 (5.747 ± 0.654 mg BSA g −1 FW). All the values align with those reported by Oliveira et al (2019) [ 35 ]. Nevertheless, unlike this previous study, which did not identify significant differences in the protein content of green bean pods across various substrates, the current research suggests a certain substrate influence ( p (S) < 0.01).…”

“…Using the ABTS method, there was also a significant influence of irrigation ( p (R) ABTS < 0.001) and the interaction between the substrate and irrigation ( p (S×R) ABTS < 0.001) for both methods; higher AC was recorded in the C100 substrates, while for the ABTS method, lowest values were found in pods from the AH100 and using the DPPH method, lower values were recorded in pods from the MIX50 substrate. Oliveira et al (2019) [ 35 ] did not obtain significant differences between substrates, with regard to the AC of the pods, by DPPH and ABTS methods, which varied between 4.21–4.46 µmol TE g −1 FW, in the pods from C substrate (80% peat:20% vermiculite), and in the pods from AM substrate (control + shell mulch) for AC-DPPH, respectively; and between 14.62–15.71 µmol TE g −1 FW, in the pods from C substrate, and in the pods from AS substrate (80% peat:20% shells) for AC-ABTS, respectively. Comparing our results with those obtained by Oliveira et al (2019) [ 35 ], our results were superior compared to AC-DPPH and lower compared to AC-ABTS.…”

“…To mitigate expenses and negative environmental consequences associated with traditional substrates, including peat, various researchers have studied the potential utilization of organic residues and agricultural by-products as alternatives in soilless cultivation systems [ 26 , 27 , 28 , 29 , 30 , 31 ]. Some studies have explored the potential of incorporating almond by-products into substrates for potted ornamental and horticultural plants [ 32 , 33 ], as a natural soil fertilizer and as mulch in Phaseolus vulgaris plants [ 3 , 7 , 34 , 35 ]. Nevertheless, there remain significant uncharted possibilities in this field.…”

Effect of Almond Shell Waste on Physicochemical Properties of Polyester-Based Biocomposites

“…This by-product is normally incinerated or dumped without control, which results in the production of large amounts of waste and pollution [2]. Several researchers have focused on different alternatives for using almond shell wastes based on their potential uses as biomass to produce renewable energy [3]; as a source of organic biopesticides [4], heavy metal adsorbents [5], dye adsorbents [6], growing media [7], the preparation of activated carbons [8] and xylo-oligosaccharides [9], antioxidants [10] or as additives in eco-friendly composites [11][12][13].…”