Slurry Acidification as a Solution to Minimize Ammonia Emissions from the Combined Application of Animal Manure and Synthetic Fertilizer in No-Tillage

Abstract

The combined application of manure/slurry and synthetic fertilizer (SF) might be a solution to decrease transport and application costs involving those by-products as well as enable access to them in regions where availability is low. Moreover, their joint application can potentially reduce environmental pollution, enlarge the manure benefits to more areas, and enhance the SF efficiency. However, such a strategy might result in increased ammonia emissions when applied to crop residues. Two experiments were implemented to assess ammonia emissions from stubble-covered soil fertilized with manure amended with SF. In Experiment 1 (E1), urea (U) and calcium ammonium nitrate (AN) were applied combined with dairy manure (MAN). In Experiment 2 (E2), urea was combined with acidified pig slurry (APS) and applied just after sowing (T0) or eight days later (T8). The combinations U + MAN and AN + MAN increased the ammonia emissions, while APS decreased the emissions from U, in APS + U combination, by more than 75%. Therefore, manure combined with SF applied on stubble-covered soil should not be recommended. T8 reduced ammonia emissions from U. APS enhanced the efficiency of U, being then an interesting strategy to mitigate ammonia emissions when applied on stubble-covered soil, as in no-tillage.

Can Dairy Slurry Application to Stubble, without Incorporation into the Soil, Be Sustainable?

“…MS, MB, ADS and IN led to the highest values of N-ANR, significantly superior to RDS T16. Several studies have confirmed the ability of acidified slurry and ammonium sulphate to reduce ammonia emissions [ 30 , 47 , 48 , 49 ] while decreasing soil pH [ 30 , 50 , 51 , 52 ]. Additionally, a soil pH slight below the neutrality can improve the nutrient availability for plants [ 37 , 53 ].…”

“…Dried ryegrass and wheat stubble samples were ground at 1 mm in a grain mill. Wheat stubble analysis procedures are described in [ 49 ]. For the ryegrass, the total-nitrogen was determined by the Kjeldahl method, following the digestion, distillation, and titration steps [ 69 ], while the NH 4 + − N content was determined directly by distillation and titration.…”

“…Slurry analyses were performed as described by [ 49 ]. The soil pH and EC were determined in a soil: water (1:2.5 w / v ) suspension.…”

“…The soil pH and EC were determined in a soil: water (1:2.5 w / v ) suspension. The methods used to determine soil texture, organic matter, total and mineral N, extractable P and K are fully described in [ 49 ]. Cation exchangeable and extractable micronutrients were performed as described by [ 70 ].…”

Dairy Slurry Application to Stubble-Covered Soil: A Study on Sustainable Alternatives to Minimize Gaseous Emissions

“…Irrigation, when available, allows for slurry incorporation through rapid infiltration by water downwards into the soil when watering occurs immediately after slurry application [24]. Acidification is a technique, already used at field-scale [25], that can efficiently decrease NH 3 volatilization from animal slurry applied to soil [12,[26][27][28], although the slurry is applied on stubble-covered soil [29]. In-season slurry application (i.e., side-dressing application) may also contribute to decreasing N losses, as plants already emerged from the soil can uptake part of the available N [30].…”