Changes in growth and quality performance of Roselle (Hibiscus sabdariffa L.) in response to soil amendments with hydrogel and compost under drought stress

Abstract Drought and low organic carbon content are two main problems for agriculture in arid and semiarid regions. Application of hydrogels and compost may decrease adverse effects of drought on plants. A factorial experiment with a randomized complete block design with three replicates was conducted to evaluate the effect of hydrogels and compost application on yield and growth parameters of Roselle (Hibiscus sabdariffa L.) under drought stress (DS). These factors manipulated with seven treatments of soil amendments with 0, 150 (H1) and 300 (H2) kg ha−1 hydrogel, 10 (C1) and 20 (C2) ton ha−1 compost, 150 kg ha−1 hydrogel + 10 ton ha−1 compost (H1C1), and 150 kg ha−1 hydrogel + 20 ton ha−1 compost (H1C2) upon three DS levels (D1: 25% depletion of available soil moisture (DASM) as no-stress condition, D2: 50% DASM as mild-stress and D3: 75% DASM as severe-stress treatment). Results showed that drought stress significantly decreased growth parameters and relative water content (RWC) while increased ion leakage (IL), antioxidant activity (AA), and total phenolic content (TPC). H1, H1C1, and H1C2 Treatments significantly increased chlorophyll content index (CCI), leaf area (LA), leaf water potential (LWP), RWC, AA, and TPC compared to control under mild and severe stress conditions. In addition, only H1C2 treatment significantly increased calyx yield (CY) under mild and severe drought conditions. Interaction between 150 kg.h−1 hydrogel and 20 ton ha−1 compost compared to the each treatment alone led to the highest SDW, LA, and CY amounts under severe DS treatment. The CCI showed a strong positive correlation with CY (R2 = 0.61, p = 0.01), while revealed a negative correlation with TPC (R2 = -0.72, p = 0.01) and AA (R2 = -0.68, p = 0.01). These results confirm that hydrogel and compost could be suitable for agricultural use under DS conditions. The amount of hydrogel and compost application is very important on plant performance under DS.