Mizyed (2026) Analysis of anthropogenic nitrogen loads and their impacts on nitrogen surplus and groundwater contamination in Palestinian agricultural systems

Identification

• Journal: Hydrology research
• Year: 2026
• Date: 2026-01-31
• Authors: Amjad Mizyed
• DOI: 10.2166/nh.2026.174

Research Groups

Civil and Environmental Engineering, Joint Water Technology Program, IUG, AUG, Gaza, Palestine

Short Summary

This study quantifies anthropogenic nitrogen flows in citrus and olive orchards in Northern Gaza using field data and modeling, revealing a substantial nitrogen surplus that indicates inefficient nutrient use and a high risk of groundwater contamination. It demonstrates that reducing organic manure application and improving irrigation water quality are critical for mitigating environmental degradation and enhancing agricultural sustainability.

Objective

• Evaluate the environmental implications of nitrogen surplus generated by agricultural activities (specifically citrus and olive cultivation) in the Gaza Strip, Palestine.
• Quantify the major anthropogenic nitrogen inputs and outputs associated with citrus and olive production systems.
• Estimate nitrogen surplus levels and their potential contribution to groundwater contamination.
• Assess the relative influence of irrigation water quality and organic manure application on overall nitrogen loading.
• Evaluate the sensitivity of nitrogen surplus to changes in key management practices to support improved, integrated nitrogen and water management.

Study Configuration

• Spatial Scale: 30 hectares of agricultural land in Northern Gaza (site A1), focusing on citrus and olive orchards. The study area overlies the most vulnerable section of the Gaza coastal aquifer.
• Temporal Scale: Annual nitrogen inputs and outputs, and seasonal crop water requirements, reflecting current farmer practices.

Methodology and Data

• Models used: FAO CROPWAT 8.0 model (for crop water requirements), input-output balance approach (for nitrogen surplus calculation), empirical models (e.g., Bouwman et al., 2002a for gaseous losses).
• Data sources: Field measurements, farmer surveys (45 validated questionnaires covering 30 hectares), GPS-based mapping of crop distribution, laboratory analysis of irrigation water for nitrate and ammonium concentrations, climatic data from the local meteorological station in Beit Lahia, and water quality data from local monitoring stations operated by the Palestinian Water Authority (WSRC 2022).

Main Results

• The base scenario revealed substantial annual nitrogen surpluses: 545 kg N/hectare for citrus and 205 kg N/hectare for olives, indicating inefficient nutrient use and a high risk of environmental losses.
• Organic manure was the dominant nitrogen input, contributing 600 kg N/hectare/year for citrus and 300 kg N/hectare/year for olives. Irrigation water was also a significant source, contributing 189 kg N/hectare/year for citrus and 138 kg N/hectare/year for olives (at an average concentration of 17.2 mg N/L).
• Sensitivity analysis showed that reducing organic manure application had the most significant impact on nitrogen surplus. A 50% reduction in manure decreased the surplus to 289 kg N/hectare/year for citrus and 77 kg N/hectare/year for olives.
• Reducing irrigation water nitrogen concentration from 17.2 mg N/L to 12 mg N/L slightly reduced the surplus to 495 kg N/hectare/year for citrus and 169 kg N/hectare/year for olives.
• The combined strategy of a 50% reduction in manure inputs and a lower irrigation water nitrogen concentration (12 mg N/L) resulted in the lowest surpluses: 241 kg N/hectare/year for citrus and 41 kg N/hectare/year for olives, approaching a near-balanced nitrogen cycle for olives.
• Farmers' actual irrigation volumes (approximately 11,000 m³/hectare for citrus and 8,000 m³/hectare for olive) were substantially higher than the estimated net irrigation requirements (7,340 m³/hectare for citrus and 6,350 m³/hectare for olive), indicating over-irrigation which can accelerate nitrate leaching.

Contributions

• Provides a novel, integrated assessment linking orchard-scale nitrogen balances with irrigation water quality and groundwater contamination risk under sandy soil and saline irrigation conditions in the Gaza Strip.
• Addresses a research gap by focusing on tree crops (citrus and olives) in a semi-arid, resource-constrained, and politically complex region.
• Highlights the critical, often underestimated, role of irrigation water quality as a nitrogen source in areas dependent on nitrate-rich groundwater.
• Offers actionable insights and a foundation for policies and practices to enhance fertilizer efficiency, protect water resources, and advance sustainability in agricultural systems under challenging environmental and socio-political conditions.

Funding

Not explicitly stated in the paper.

Citation

@article{Mizyed2026Analysis,
  author = {Mizyed, Amjad},
  title = {Analysis of anthropogenic nitrogen loads and their impacts on nitrogen surplus and groundwater contamination in Palestinian agricultural systems},
  journal = {Hydrology research},
  year = {2026},
  doi = {10.2166/nh.2026.174},
  url = {https://doi.org/10.2166/nh.2026.174}
}