Effect of a commercial seaweed extract (Kelpak®) and polyamines on nutrient-deprived (N, P and K) okra seedlings

In agriculture, nutrient depleted soil is a common problem, hence large amounts of applied fertilizer are required to maintain optimal nutrient levels. Nutrient-deficient plants are often vulnerable to pathogens and show a reduction in yield. In this study, the nutrient-stress-relieving effects of the seaweed concentrate, Kelpak® and a polyamine (PA) solution were investigated. Kelpak® is prepared from Ecklonia maxima (Osbeck) Papenfuss and recently shown to contain endogenous PAs. Okra seedlings [Abelmoschus esculentus (L.) Moench] deprived of nitrogen (N), phosphorous (P) and potassium (K) were treated with either a 0.4% Kelpak® solution or a 10−4 M PA solution (a combination of putrescine, spermidine and spermine) three times a week under greenhouse conditions. Both Kelpak® and PA treatments significantly enhanced seedling vigor under nitrogen-deprived conditions. Kelpak® treatment was effective in significantly improving most of the seedling growth parameters under P and K deficiency compared to the respective controls. Although, the PA treatment resulted in some improvement in the growth of the seedlings in P and K deficient plants, these results were not significantly different from the control. The beneficial effect of Kelpak® in relieving nutrient deficiency, especially N deficiency, may in part be due to the PAs present in Kelpak® acting in synergy with other plant growth regulators such as auxin. The application of seaweed concentrate as part of a fertilizing regime could potentially help mitigate the detrimental effects of major nutrient deficiencies, minimizing the use of expensive chemical fertilizers.

► Seaweed concentrate improved seedling growth of okra under nutrient deficiency.
► 0.4% Kelpak® was effective primarily under phosphorus and potassium deficiency.
► Seaweed concentrates can overcome nutrient stress in crop plants.