This study evaluated the agronomic performance and economic viability of integrated nutrient management paired with humic acid and seaweed extract under abiotic stress in Yazd, Iran. Two field experiments were conducted using randomized complete block designs with three replications. Experiment 1 (Abarkooh) evaluated the salt-tolerant cultivar 'Sistan' under 10 irrigation cycles (EC = 10.4 dSm-1). Experiment 2 (Marvast) evaluated cultivar 'Roshan' (irrigation 6 cycles due to power outages) in highly saline-sodic loamy sand (EC=44.6 dSm-1, SAR = 36.12, ESP = 34.22). Treatments: Farmer’s Customary Practice (T1: single traditional urea), Soil-Test-Based Supplemental Fertilization (T2), and Anti-Stress Management (T3: T2+ soil humic acid + foliar micronutrients + seaweed extract). Results showed that T3 significantly increased growth, yield components, and biological yield across both sites (p < 0.05). In Abarkooh, T3 achieved a grain yield of 10,170kg ha-1a 147% increase over T1). In Marvast, T3 buffered yield failure under stress, increasing grain yield from 350 kg ha-1 (T1) to 1,636 kg ha-1a 367% relative increase). Partial budgeting demonstrated that T3 was highly profitable in Abarkooh (net benefit: 1,075,735 times 10^3 IRR ha-1; B/C = 2.03). In Marvast, despite a positive marginal B/C of 2.16, commercial viability was unfeasible due to absolute yield falling below the provincial economic threshold.
Introduction
In Yazd these challenges are compounded by falling water tables, poor soil quality, and unpredictable agricultural well power outages that disrupt irrigation schedules. Exogenous seaweed extract, such as soil-applied humic acids and foliar seaweed extracts, offer a practical physiological buffer. Humic substances improve cation exchange capacity and root growth, while seaweed extract supply osmolytes and phytohormone precursors that preserve turgor pressure and delay leaf senescence. This study examined the agronomic and economic impacts of integrated anti-stress management across two contrasting stress regimes.
Materials and Methods
Two field experiments were conducted during recent cropping seasons in Yazd Province, Iran:
1. Abarkooh: Silty clay loam (EC = 10.4 dS m-1, pH = 7.1), irrigated with water of EC_w = 7.4 dS m-1 across 10 complete cycles using cultivar 'Sistan'.
2. Marvast: Saline-sodic loamy sand (EC = 44.6 dS m-1, ESP = 34.22), irrigated with water of EC= 6.38 dSm-1 under 6 irrigation cycles (severe water deficit) using cultivar 'Roshan'.
Both experiments were arranged in RCBD with three replications (500 m2 plot size). Three treatments were applied: T1 (Farmer’s Customary Practice: 400 kg ha-1 Urea), T2 (Soil-Test Supplemental Fertilization: N, P, K tailored to soil test), and T3 (Integrated Anti-Stress Management: T2 + 5 kg ha-1 soil humic acid + foliar chelated Fe, microelements, and Ascophyllum nodosum extract applied at tillering and booting). Agronomic parameters were measured at maturity, data were analyzed using SAS (v9.4), and economic profitability was determined via partial budgeting and Benefit-to-Cost (B/C) ratios.
Results and Discussion
ANOVA revealed significant treatment effects on plant height, spike density, biological yield, and grain yield at both locations.
In Abarkooh, T3 produced the highest grain yield (10,170 kg ha-1), outperforming T1 4,117 kg ha-1 by 147% and T2 6,053 kg ha-1 by 68%. T3 also significantly increased plant height (86.67 cm), spike density (465 spikes m-2), and biological yield (9,468 kg ha-1. This improvement resulted from correcting severe baseline phosphorus deficiencies via balanced fertilization, combined with seaweed extract -driven root stimulation and cellular osmotic adjustment under salt stress.
In Marvast, in T1 (350 kg ha-1 grain yield). Treatment T3 mitigated yield loss, achieving 1,636 kg ha-1 grain yield, along with higher thousand-grain weight (34.31 g) and spike density (192 spikes m-2). Osmolytes and micronutrients (notably Zn) in T3 maintained membrane integrity and photosynthetic activity under extreme salt and drought accumulation.
Comparative evaluation demonstrated that relative responsiveness to seaweed extract was higher under extreme stress (+367% in Marvast vs. +147% in Abarkooh), confirming their protective buffering capacity under harsh conditions.
Economic Evaluation and Conclusion
Partial budgeting showed that in Abarkooh, T3 generated an additional net profit of 1,075,735 \times 10^3 IRR ha-1 over T1 with a B/C ratio of 2.03, establishing it as highly profitable. In Marvast, T3 yielded a marginal B/C ratio of 2.16; however, absolute yield (1,636 kg ha-1) remained below the commercial viability threshold (3,000 kg ha-1). In conclusion, replacing traditional fertilization with integrated anti-stress management is highly recommended for saline soils with adequate water. |