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Assessment of Atmospheric Deposition of Nutrients in Minnesota

Start Date: 2020
Principal Investigator: Paulo Pagliari
Co-Investigators: Fabian Fernandez and Dr. Daniel Kaiser
Organization: University of Minnesota
Status: Ongoing

Background Info

The primary goal of this research to monitor atmospheric deposition of N and S in selected sites where current N and S rate studies are being conducted. Over the last few years many of the studies being conducted to evaluate crop response to added N fertilizer are showing a decrease in the amount of N required to reach the economic optimum nitrogen rate, in certain parts of the state. One possible explanation is that more N is coming down with rainwater and snow during the winter and being stored in the soil. During the growing season, the plant can then utilize this N in addition to any other N that was applied in the fertilizer form. It is therefore, important to assess the distribution of N being deposited from atmospheric rain and snow fall throughout the state so that better N management practices can developed and implemented. Atmospheric S deposition has also played a key role in plant nutrient for many decades. However, due to advanced technology, the amount of S emitted to the atmospheric has significantly been decreasing over the decades. Today many sites are starting to show increased grain yield when S is applied, however inconsistent results are observed, and we cannot predict which site will and or will not respond to S application. Being able to monitor N and S deposition throughout the state can help shine some light on this issue and help us improve N and S recommendation for Minnesota growers.

Objectives

The objective of this study is to monitor the atmospheric deposition of S and N.

Key Findings

Crookston

Rainfall total reported at Crookston was 14.9” from March to August. Rainfall water pH was also highly variable; however, the pH was much higher than what was observed at Becker. At Crookston rainwater pH was always above 5.59 (ranging between 5.59 and 7.99) when rainfall was below 1”. For events above 1” rainwater pH ranged between 5.59 and 7.23. The amount of rainfall in each event was evenly distributed throughout the year with very several events higher than 1”, 2.78” being the highest. The majority ranged between 0.14 and 1”. Nitrate concentration in the rainwater was very low and ranged between 0.01 ppm to 1.19 ppm. Ammonium had higher concentrations than nitrate and ranged between 0.01 and 16.5 ppm.

Lamberton

Rainfall total reported at Lamberton was 18.2” from April to September. Rainfall water pH was also highly variable. At Lamberton rainwater pH was never below 6.4 (ranging between 6.4 and 8.6) regardless of rainfall amount. The amount of rainfall in each event was evenly distributed throughout the year with very several events higher than 1”, 2.25” being the highest. Nitrate concentration in the rainwater was very low and ranged between 0.02 ppm to 1.97 ppm. Ammonium concentrations were higher than nitrate and ranged between 0.02 and 3.53 ppm. Ammonium concentration tended to be higher in the spring and early summer and during rainfall events that were below 0.5”.

Waseca

Rainfall total reported at Waseca was 19.2” from April to August. Rainfall water pH was also highly variable. At Waseca rainwater pH was mostly above 6.0 (ranging between 4.4 and 8.0). The amount of rainfall in each event was evenly distributed throughout the year with several events higher than 1”, 4.4” being the highest. Nitrate concentration in the rainwater was very low and ranged between 0.04 ppm to 0.80 ppm. Ammonium had higher concentrations than nitrate and ranged between 0.13 and 1.20 ppm. Ammonium concentration tended to be higher in the spring and early summer and during rainfall events that were below 1.0”.

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