Leaf elemental composition of Cleome gynandra L. as influenced by giant kelp extract and kraal manure application

Abstract

<i>Cleome gynandra</i> L. (spider plant) is a traditional leafy vegetable that contains minerals, vitamins, proteins, and phytochemical compounds. However, little is known about the effects of sole KM (kraal manure), GKE (giant kelp extract), and GKE + KM on spider plant leaf mineral composition. This study aimed to determine the effect of sole GKE, KM, and GKE + KM on leaf mineral composition. It is hypothesized that 1 mL/L GKE supplemented with 30 kg/345 m² KM will influence leaf nutrient composition. This hypothesis was tested using a split-plot design across two growing seasons at the University of Fort Hare research farm, to assess treatment-specific effects on macro- and micronutrient accumulation in spider plant leaves. The main plots comprised three levels of KM (0, 30, and 60 kg/345 m²) and subplots comprised five levels of GKE (0, 1, 2, 3, and 4 mL/L), each replicated three times. A two-way analysis of variance test was performed using JMP Pro 18 statistical software package to determine the effects of various levels of GKE and KM application on leaf chemical parameters. Canonical correspondence analysis was performed using R Studio version 4.1.2 (2024). Results showed that application of 30 kg/345 m² KM in season 1 increased (p < 0.05) nitrogen, calcium, magnesium, potassium, sodium, iron, manganese, and zinc. Spider plant treated with 2 mL/L GKE showed increased levels of iron, manganese, and zinc in both summer seasons. Additionally, the combination of 2 mL/L GKE + 30 kg/345 m² KM increased leaf nitrogen, iron, manganese, and zinc. This study confirms that GKE, KM, and GKE + KM play a significant role in leaf mineral uptake.