Soil system budgets of N, Si and P in an agricultural irrigated watershed: surplus, differential export and underlying mechanisms

Pinardi, Monica; Soana, Elisa; Laini, Alex; Bresciani, Mariano; Bartoli, Marco

doi:10.1007/s10533-018-0484-4

Cited by 13 publications

(19 citation statements)

References 124 publications

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“…The average areal N surplus of the Oglio and Mincio portions was similar to that calculated on the whole watershed level [14,73]. Within these basins, the municipalities with the highest N surpluses are located in the high-medium plain included in the watershed portions under study, which are characterized by high livestock densities [14,73]. The soil N budgets of the sub-basins in the alpine sector of the Po River watershed underwent temporal and spatial variations related to changes in land use and farming practices [86].…”

Section: Excess Manure Availability and Use Of Synthetic Fertilizers supporting

confidence: 75%

“…The large availability of organic N does not exclude the use of synthetic fertilizers, which represent the second N input utilized in agriculture (about 25% of the total N input). The average areal N surplus of the Oglio and Mincio portions was similar to that calculated on the whole watershed level [14,73]. Within these basins, the municipalities with the highest N surpluses are located in the high-medium plain included in the watershed portions under study, which are characterized by high livestock densities [14,73].…”

Section: Excess Manure Availability and Use Of Synthetic Fertilizers supporting

confidence: 69%

“…A soil system N budget was performed using farming census data [62] at the spatial resolution of the individual municipalities included within each watershed, and then aggregated at the sub-basin level [69][70][71]. We compared N inputs (livestock manure, synthetic fertilizers, atmospheric deposition, and biological fixation) and outputs (crop uptake, ammonia volatilization, and denitrification) across the Utilized Agricultural Area (UAA) of the considered watershed portions [14,72,73]. The input and output terms and the N balance were expressed in unit of mass per time (t N year −1 ).…”

Section: Nitrogen Mass Balance Calculations At the Watershed Levelmentioning

confidence: 99%

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Is Flood Irrigation a Potential Driver of River-Groundwater Interactions and Diffuse Nitrate Pollution in Agricultural Watersheds?

Racchetti

Salmaso

Pinardi

et al. 2019

Water

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In the Po plain, northern Italy, rivers within agricultural basins display steep summer increases in nitrate (NO3−) concentrations. Flood irrigation in overfertilized, permeable soils may drive such diffuse pollution, facilitating interactions between NO3−-rich groundwater and surface waters. We discuss multiple, indirect evidence of this mechanism in the Adda, Oglio, and Mincio rivers. These rivers drain agricultural soils with elevated nitrogen (N) surpluses, averaging 139, 193, and 136 kg ha−1 in the Adda, Oglio, and Mincio watersheds, respectively. The three rivers cross a transitional area between highly permeable and impermeable soils, where summer NO3− concentrations may increase by one order of magnitude over short distances (8–20 km). Upstream of this transitional area, a major fraction of the river flow is diverted for flood irrigation, a traditional and widespread irrigation technique for permeable soils. We speculate that diverted water solubilizes soil N excess, recharges the aquifer, and transfers soil N surplus into groundwater, resulting in NO3− pollution. Groundwater–river interactions were estimated experimentally, via water and NO3− budgets in 0.3 to 1 m3 s−1 km−1 and in 1500 to 5400 kg NO3−–N day−1. The data suggest a pronounced east–west gradient of groundwater to river diffuse water inputs among the three adjacent basins, reflecting the soil permeability and the width of the river–groundwater interaction zone. Given the large stock of NO3− in groundwater, management interventions performed at the basin scale and aimed at decreasing N excess will not produce an immediate decrease in river NO3− pollution.

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Section: Excess Manure Availability and Use Of Synthetic Fertilizers supporting

confidence: 75%

Section: Excess Manure Availability and Use Of Synthetic Fertilizers supporting

confidence: 69%

Section: Nitrogen Mass Balance Calculations At the Watershed Levelmentioning

confidence: 99%

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Is Flood Irrigation a Potential Driver of River-Groundwater Interactions and Diffuse Nitrate Pollution in Agricultural Watersheds?

Racchetti

Salmaso

Pinardi

et al. 2019

Water

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“…In this basin, livestock densities are low, and cereals are the dominant crops, amended almost exclusively with synthetic fertilizers. NUE (nitrogen use efficiency), i.e., the proportion of all N inputs exported via crop harvest, reached~60%, a value markedly higher than those calculated for other sub-basins of the Po river system characterized by higher availability of livestock manure and greater amounts of applied N that are potentially lost via leaching or runoff [25,51,52]. Synthetic fertilizers are more easily dosed and allow more accurately fulfilling crops' N requirements without generating large excesses and losses in the environment.…”

Section: Discussionmentioning

confidence: 68%

“…The specific knowledge of key factors governing N transport and transformation pathways in agricultural areas are not yet fully clarified. Several studies highlighted that, in agricultural irrigated watersheds, the generation of large N loadings does not necessarily translate into high exports to terminal waterbodies or coastal zones [9,31,52], and they demonstrated the relevance of small human-made waterways as elective sites for N processing and removal [19,49,54]. In the investigated basin, N removal via denitrification within the canal network represents only a small flux in the whole N budget on annual basis.…”

Section: Discussionmentioning

confidence: 99%

In Search for the Missing Nitrogen: Closing the Budget to Assess the Role of Denitrification in Agricultural Watersheds

et al. 2020

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Although representing a paramount mechanism against nitrogen excess in agricultural landscapes, soil denitrification is still a largely unknown term in nitrogen balances at the watershed scale. In the present work, a comprehensive investigation of nitrogen sources and sinks in agricultural soils and waters was performed with the aim of gaining insights into the relevance of soil denitrification in a highly farmed sub-basin of the Po River delta (Northern Italy). Agricultural statistics, water quality datasets, and results of laboratory experiments targeting nitrogen fluxes in soils were combined to set up a detailed nitrogen budget along the terrestrial–freshwater continuum. The soil nitrogen budget was not closed, with inputs exceeding outputs by 72 kg N·ha−1·year−1, highlighting a potential high risk of nitrate contamination. However, extensive monitoring showed a general scarcity of mineral nitrogen forms in both shallow aquifers and soils. The present study confirmed the importance of denitrification, representing ~37% of the total nitrogen inputs, as the leading process of nitrate removal in heavily fertilized fine-texture soils prone to waterlogged conditions.

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Silicon concentrations and stoichiometry in two agricultural watersheds: implications for management and downstream water quality

et al. 2022

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Agriculture alters the biogeochemical cycling of nutrients such as nitrogen (N), phosphorus (P), and silicon (Si) which contributes to the stoichiometric imbalance among these nutrients in aquatic systems. Limitation of Si relative to N and P can facilitate the growth of non-siliceous, potentially harmful, algal taxa which has severe environmental and economic impacts. Planting winter cover crops can retain N and P on the landscape, yet their effect on Si concentrations and stoichiometry is unknown. We analyzed three years of biweekly concentrations and loads of dissolved N, P, and Si from subsurface tile drains and stream water in two agricultural watersheds in northern Indiana. Intra-annual patterns in Si concentrations and stoichiometry showed that cover crop vegetation growth did not reduce in-stream Si concentrations as expected, although, compared to fallow conditions, winter cover crops increased Si:N ratios to conditions more favorable for diatom growth. To assess the risk of non-siliceous algal growth, we calculated a stoichiometric index to quantify biomass growth facilitated by excess N and P relative to Si. Index values showed a divergence between predicted algal growth and what we observed in the streams, indicating other factors in uence algal community composition. The stoichiometric imbalance was more pronounced at high ows, suggesting increased risk of harmful blooms as environmental change increases the frequency and intensity of precipitation in the midwestern U.S. Our data include some of the rst measurements of Si within small agricultural watersheds and provide the groundwork for understanding the role of agriculture on Si export and stoichiometry.

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Soil system budgets of N, Si and P in an agricultural irrigated watershed: surplus, differential export and underlying mechanisms

Cited by 13 publications

References 124 publications

Is Flood Irrigation a Potential Driver of River-Groundwater Interactions and Diffuse Nitrate Pollution in Agricultural Watersheds?

Is Flood Irrigation a Potential Driver of River-Groundwater Interactions and Diffuse Nitrate Pollution in Agricultural Watersheds?

In Search for the Missing Nitrogen: Closing the Budget to Assess the Role of Denitrification in Agricultural Watersheds

Silicon concentrations and stoichiometry in two agricultural watersheds: implications for management and downstream water quality

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