Hydroponic cultivation of Tetragonia decumbens in seawater dilutions for commercial agriculture

Abstract

The production of agricultural products is severely impacted by climate change, rising soil salinity, and developing freshwater shortages in many different nations, most notably South Africa. Soil salinization is a serious environmental threat to agricultural productivity and food security around the world. It impairs the structure of the soil, the availability of nutrients, and the growth of plants, resulting in lower agricultural yields. Freshwater shortages also represent a few of the agricultural factors impacting the production of agriculture and the availability of food in South Africa. It has been noted that water needs have been rising since the 1950s, yet the availability of freshwater has been steadily declining. In water-constrained regions, the development of agricultural irrigation competes with rising household and industrial requirements, which could result in excess water being transferred to high-priority sectors at the expense of agriculture. As food production and a lack of water develop, these complex changing factors put strain on agriculture in many areas where traditional water sources are used for irrigation. Therefore, investigation on dune spinach propagation, salinity stress, cultivation, and nutritional values is required. The aim of this research is to examine the impact of diluted seawater and different pruning intervals on the nutritional profile, antioxidant capacity, and vegetative development of T. decumbens shoots grown hydroponically. Tetragonia decumbens cuttings were collected from a specific clone plant that was flourishing alongside the coastline at Granger Bay, Western Cape. A stem cutting propagation technique was used to root new plant material. Four identically designed Nutrient Film Technique (NFT) structures configured in a full block design were set up, with different diluted seawater concentrations (100% tap water/50L, 20% seawater/50L, and 40% seawater/50L) in each sump. Nutrifeed was essential for proper nutrition across all systems. Dune spinach plants grown within these circumstances had four different pruning intervals (unpruned, 15 cm, 30 cm, and 45 cm cuts). The plant growth was measured with a tape measure, and the pruned fresh and dry plant components were weighed on a laboratory scale. The data obtained from shoot samples subjected to diluted seawater and different pruning intervals was statistically computed using a two-way examination of variance (ANOVA). The Fisher’s least significant difference will be used to compare the significant differences between treatment means at p≤0.05 using MINI-TAB statistical software. The amount of chlorophyll in dune spinach plants was determined using a Konic Minolta meter (SPAD-502). Dune spinach shoots were dried and tested for total flavonols, total polyphenols, ABTS, ferric reducing antioxidant power (FRAP), and DPPH to determine phytochemicals and antioxidants. The dried T. decumbens shoots were evaluated by using tests for crude proteins, crude fat content, ash content, moisture content, Neutral Detergent Fibre (NDF) and Acid Detergent Fibre (ADF), macro-elements (sodium, phosphorus, magnesium, potassium, calcium, K/Ca+Mg, nitrogen), and micro nutrients (magnesium, zinc, copper and iron) to determine its nutritional values. Plants cultivated in 20%SW with pruning intervals of 30 and 45 cm produced large quantities of both dry and fresh weights of dune spinach shoots at weeks 4 and 12, but at week 8 they started to decline. Increased polyphenol, flavonol, and FRAP capacity were observed in diluted seawater (20%SW) at pruning intervals of 15 and 30 cm. In contrast, the control shown enhances both DPPH and ABTS capacity. Macronutrients (magnesium, salt, and nitrogen), micronutrients (copper and zinc), and proximate components (ash, moisture, and crude protein) produced significant yields in plants cultivated in 20%SW with three different pruning intervals (15 cm, 30 cm, and 45 cm).