Alternatives to regular urea for abating N losses in lettuce production under sub-tropical climate
Citation
Cantú, R.R., Aita, C., Doneda, A., Giacomini, D.A., Dessbesell, A., Arenhardt, M., De Bastiani, G.G., Pujol, S.B., Rochette, P., Chantigny, M.H., Giacomini, S.J. (2017). Alternatives to regular urea for abating N losses in lettuce production under sub-tropical climate. Biology and Fertility of Soils, [online] 53(6), 589-599. http://dx.doi.org/10.1007/s00374-017-1202-4
Plain language summary
Nitrification inhibitors are increasingly used in agricultural soils to reduce accumulation of nitrate following fertilization and to reduce greenhouse gas emissions and leaching of nitrogen to groundwater. Composted manure is also thought to be less reactive in the environment than mineral fertilizers or raw manure. In the context of our collaboration with brazilian colleagues (e.g. projects #1259, 1642), we participated to a study carried out in Brazil on the efficacy of nitrification inhibitors and use of composted manure to reduce pollution from crop fertilized with urea. Overall, use of compost and use of nitrification inhibitors reduced greenhouse gas emisisons by an order of magnitude, compared to urea. These alternative practices resulted in greater use efficiency of supplied N than with urea. Nitrate concentration of the soil solution was reduced by up to 17 times, thus greatly reducing risks for nitrogen leaching losses. We conclude that, as compared to regular urea, the use of composted manure and the addition of nitrification inhibitors to urea are good practices to reduce environmental N losses from crop production under sub-tropical climate. It is most likely that these conclusion also apply to cooler climate in Canada.
Abstract
Alternative fertilization practices are needed for reducing gaseous and leaching N losses at high urea application rates. The objective of this study was to compare gaseous N emissions (N2O and NH3) and NO3− concentrations in the soil solution during two successive lettuce cropping seasons under contrasting fertilization practices. Treatments were fertilization with regular urea (U), urea treated with urease [N-(n-butyl) thiophosphoric triamide (NBPT)] and nitrification [dicyandiamide (DCD)] inhibitors (UIs), non-acidified pig slurry compost (PSC), acidified pig slurry compost (APSC), and an unfertilized control (C). Acidification of pig slurry during composting had no impact on soil cumulative N2O emissions during the cropping seasons. The use of composts resulted in emission factors (EFs) (PSC, 0.09% of applied N; APSC, 0.16%) an order of magnitude smaller than with regular urea (1.63%). Similarly, adding NBPT and DCD to urea reduced the N2O EF from 1.63 to 0.37% of applied N and fertilizer-induced NH3 emissions from 30.2 to 3.4% of applied N. Composts and UI resulted in yield-scaled N2O emissions that were 33 to 49% lower than the unfertilized control and 64 to 73% lower than the regular urea estimates, indicating a greater efficiency of supplied N with composts and UI. Nitrate concentration of the soil solution (at 0.1 and 0.3 m) in PSC, APSC, and UI plots was similar to the control and up to 17 times lower than with regular urea, indicating reduced risks for leaching losses. We conclude that, as compared to regular urea, the use of composted pig slurry, with and without acidification, and the addition of NBPT and DCD inhibitors to urea are good practices to reduce environmental N losses from lettuce production under sub-tropical climate.