This study applies Material Flow Cost Accounting to analyze the economic and environmental performance of four key crops - watermelon (Citrullus lanatus), onion (Allium cepa), tomato (Solanum lycopersicum), and wheat (Triticum aestivum) - in Sistan and Baluchestan Province, Iran. The research objectives were to: (1) quantify material and energy flows throughout production cycles, (2) identify inefficiencies in input utilization, and (3) evaluate sustainability trade-offs among crops under arid conditions. The methodology utilized official agricultural data (2022-2023) to examine inputs (water, fertilizers, pesticides, labor, energy) and outputs (yield, emissions, losses) on a per-hectare basis, following ISO 14051 standards. Energy flows were calculated in MJ ha⁻¹, while economic indicators included Gross Value of Production ($ ha⁻¹), Gross Return ($ ha⁻¹), Benefit-Cost Ratio, and Economic Productivity (kg $⁻¹). Environmental impacts were assessed through emission factors for nitrate leaching (kg ha⁻¹), ammonia volatilization (kg ha⁻¹), and pesticide residues.Results demonstrated distinct performance patterns. Onion production showed the highest economic returns (Gross Value of Production: $7352.7 ha⁻¹; Benefit-Cost Ratio: 12.6) but significant environmental costs, including nitrate leaching (57.6 kg ha⁻¹) and ammonia emissions (51.7 kg ha⁻¹). Tomato exhibited moderate profitability (Gross Value of Production: $5337.6 ha⁻¹) with poor energy efficiency (Net Energy: -30622.44 MJ ha⁻¹; Energy Ratio: 0.42). Watermelon demonstrated balanced performance (Gross Value of Production: $3114.6 ha⁻¹; Economic Productivity: 100.1 kg $⁻¹; Energy Ratio: 0.84), while wheat, though economically limited (Gross Value of Production: $681.6 ha⁻¹), had the lowest environmental impacts. The analysis revealed that high-value crops (onion, tomato) incurred substantial material losses (onion: $382.3 ha⁻¹ negative product costs) and energy deficits, whereas low-input crops (wheat, watermelon) showed better sustainability metrics. Key findings include tomato's significant pesticide emissions to soil (2.8 kg ha⁻¹) and wheat's energy inefficiency (Specific Energy: 10.59 MJ kg⁻¹). These results provide empirical evidence for crop selection in arid regions, suggesting: (1) optimized input management for high-value crops, (2) promotion of watermelon in resource-limited systems, and (3) integration of energy-environmental indicators in agricultural planning. The study establishes Material Flow Cost Accounting as an effective tool for comprehensive sustainability assessment in dryland farming systems.
