Abstract

Agriculture is considered one of the main nitrogen (N) pollution sources through the diffuse emissions of ammonia (NH3) and nitrous oxide (N2O) to the atmosphere and nitrate (NO3−) to water bodies. The risk is particularly high in horticultural production systems (HPS), where the use of water and fertilizers is intensive and concentrated in space and time, and more specifically, in the case of vegetable crops that have high growth rates, demanding an abundant supply of water and nitrogen forms. Therefore, to comply with the EU environmental policies aimed at reducing diffuse pollution in agriculture, there is the need for mitigation practices or strategies acting at different levels such as the source, the timing and the transport of N. HPS are often well suited for improvement practices, but efficient and specific tools capable of describing and quantifying N losses for these particular production systems are required. The most common mitigation strategies found in the literature relate to crop, irrigation and fertilization management. Nevertheless, only the success of a mitigation strategy under specific conditions will allow its implementation to be increasingly targeted and more cost effective. Assessment methods are therefore required to evaluate and to quantify the impact of mitigation strategies in HPS and to select the most promising ones.

Highlights

  • Diffuse or non-point source pollution refers to both water and air pollution caused by a variety of activities that have no specific point of discharge

  • The potential risk of ammonia volatilization from urea fertilizer can represent up to 65% of the N applied, depending on soil and climatic conditions [46]. This aspect is very important in orchards, as urea application is common at the post-harvest stage, to enable a fast-nutrient uptake that confers adequate nutrient storage and a good plant performance for the following spring

  • As denitrification is favored by high NO3 − and C availability, it is likely to occur in wet horticulture soils, in particular immediately after rainfall or an irrigation event when soil pores may become filled with water and the oxygen supply may be temporarily restricted [58]

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Summary

Introduction

Diffuse or non-point source pollution refers to both water and air pollution caused by a variety of activities that have no specific point of discharge. Irrigation and/or by the precipitation occurring during the post‐harvest season, both situations Their residues take a particular position relative to arable crops due to often large amounts of biomass, with a high N content (up to 200 kg·ha−1 ) and low C:N ratios, left behind on the field [16,17]. These adverse characteristics can be exacerbated by the incorrect management of irrigation and/or by the precipitation occurring during the post-harvest season, both situations maintaining excessively high moisture conditions in the soil surface and drainage fluxes out of the root zone. A description of the available strategies to mitigate these losses is presented; followed by the revision of three methods to evaluate the success of the different types of measures

Nitrogen Loss Pathways and Processes
Nitrate Leaching
Ammonia Volatilization
Nitrification and Denitrification
Management of Crop Residues
Use of Cover Crops
Crop Rotations
Use of N Use-Efficient Plants
Irrigation and Fertilization Management
Irrigation Water Management
Fertilizer Management
Assessment of the Effectiveness of Mitigation Measures
Measurements
Assessment Method
Farm Surveys and Nutrient Budgets
Modelling Water and N-Related Processes in Horticultural Systems
Findings
Conclusions
Full Text
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