Nitrous oxide fluxes from liquid pig manure and urea fertilizer applied to annual crops

• Published in: Agriculture, ecosystems & environment ecosystems & environment, 2021-06, Vol.313, p.107393, Article 107393
• Main Authors: Adelekun, Mayowa, Akinremi, Olalekan, Nikièma, Paligwendé, Sparling, Brad, Tenuta, Mario
• Format: Article
• Language: English
• Subjects: Annual crop; Greenhouse gas; Inorganic fertilizer; N2O flux; Pig manure
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2021.107393

•Crop yield and nitrogen (N) uptake are marginally affected by N source.•Source of N, liquid pig manure vs urea fertilizer, affected estimate of growing season daily and cumulative N2O emissions.•Lower N2O was emitted per unit of crop grain yield from liquid manure compared to urea. Manure can serve as a comparable source of nitrogen (N) as synthetic fertilizer; however, soil nitrous oxide (N2O) fluxes may differ substantially between these two N sources. This study was carried out during three growing seasons (2011, 2013, and 2014) in a replicated field experiment, cropped to either barley (Hordeum vulgare L.) or wheat (Triticum aestivum L.). The experiment included three treatments in a randomized complete block design with four replicates: zero N amendment (CON), liquid pig manure (LPM) at a rate of 56,000 L ha−1 yr−1, and urea (FER) at N rate matching the total available N content in the manure. In all three years, crop yield and N uptake were slightly higher in the LPM treatment compared to the FER treatment, but the difference was not statistically significant. In 2011 and 2014, when applied N rate was moderate but the application time coincided with a long period of drought, cumulative N2O emissions, emission intensity and factor were significantly higher in the FER treatment than in LPM treatment. In 2013, however, when applied manure N was relatively high, and soil moisture mostly adequate, no such effect was observed. Soil available N content, temperature, and moisture together were positively correlated (P < 0.05) with N2O emission in both LPM and FER samples, and explained about 40 % of the overall variability of N2O emission. We conclude that the use of liquid manure N in cropping system is an environmentally advisable strategy. However, from both nutrient management planning and N2O emission reduction stand points, the results of this study highlight the challenges associated with manure N variability, and emphasis the need for applying manure based on its known N content in addition to soil N test, so that application rate can meet the crop N demand and minimize N2O emissions.