The Combined Use of Liquid Fertilizer and Urease/Nitrification Inhibitors on Maize Yield, Nitrogen Loss and Utilization in the Mollisol Region

Abstract

Nitrification inhibitor (NI) and urease inhibitor (UI) with fertilizer have the potential to reduce nitrogen (N) loss as well as improve grain yields. Urea–ammonium nitrate (UAN) solution as liquid fertilizer is superior to conventional solid nitrogen (N) fertilizer in terms of fertilizer efficiency, energy savings, environmental pollution reduction and economic benefits. However, comprehensive assessments of UAN with inhibitors from an environmental and agronomy perspective, including insights into the mechanisms of UAN with inhibitors, are lacking. In a field trial, three single-inhibitor and two double-inhibitor (DI) treatments were set to quantify the grain yield, the N losses and the N recovery efficiency of maize treated with urea supplemented with dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP) and N-(n-butyl) thiophosphoric triamide (NBPT). Compared with the UAN treatment, the supply of urease inhibitors reduced NH3 emission by 13.0% but increased N2O emission by 13.0%. The supply of nitrification inhibitors delayed the conversion of ammonium N to nitrate N and improved NH3 emission by 23.5–28.7%, but reduced N2O emission by 31.4% and significantly increased the maize yield by 21.3%. The combined use of NBPT and DCD were not compatible in UAN and cannot achieve the maximum potential for optimizing yields and reducing nitrogen losses. Considering the grain yield, the N use efficiency and the N losses, the combined use of NBPT and DMPP in maize production system significantly improved the grain yield and N use efficiency, as well as reduced N losses.

Selected Carbon and Nitrogen Compounds in a Maize Agroecosystem under the Use of Nitrogen Mineral Fertilizer, Farmyard Manure, Urease, and Nitrification Inhibitors

“…There were also no significant effects of inhibitor use with farmyard manure on the NH 4 -N concentrations, although the treatments with nitrification and double inhibitors had numerically greater contents than the FYM and FYM+UI treatments. The addition of DMPP with the UAN fertilizer effectively decreased the nitrification rates in the soil, raised the content of NH4-N by 8.70%, and lowered the NO3-N concentration by 14.46% (Figures 8 and 9), which is consistent with the results of other studies [7,24,41]. DMPP extends the residence time of NH4-N in soils due to the deactivation of the enzyme responsible for the first step of nitrification, i.e., the oxidation of NH4 + to NH2OH via indiscriminate binding and suppressing ammonium monooxygenase activity [23][24][25][41][42][43].…”

“…The addition of DMPP with the UAN fertilizer effectively decreased the nitrification rates in the soil, raised the content of NH4-N by 8.70%, and lowered the NO3-N concentration by 14.46% (Figures 8 and 9), which is consistent with the results of other studies [7,24,41]. DMPP extends the residence time of NH4-N in soils due to the deactivation of the enzyme responsible for the first step of nitrification, i.e., the oxidation of NH4 + to NH2OH via indiscriminate binding and suppressing ammonium monooxygenase activity [23][24][25][41][42][43]. Abalos et al [44] noticed that NI applications could diminish denitrification-induced N losses by decreasing the soil NO3-N contents for denitrification, which allows the available nitrogen to be retained in the soil and become absorbed by the plants for a longer time.…”

“…In previous studies [43], mineral fertilization with NI and UI inhibited not only nitrification but also urea hydrolysis, which resulted in significant decreases in the NO3-N The addition of DMPP with the UAN fertilizer effectively decreased the nitrification rates in the soil, raised the content of NH 4 -N by 8.70%, and lowered the NO 3 -N concentration by 14.46% (Figures 8 and 9), which is consistent with the results of other studies [7,24,41]. DMPP extends the residence time of NH 4 -N in soils due to the deactivation of the enzyme responsible for the first step of nitrification, i.e., the oxidation of NH 4…”

“…+ to NH 2 OH via indiscriminate binding and suppressing ammonium monooxygenase activity [23][24][25][41][42][43]. Abalos et al [44] noticed that NI applications could diminish denitrification-induced N losses by decreasing the soil NO 3 -N contents for denitrification, which allows the available nitrogen to be retained in the soil and become absorbed by the plants for a longer time.…”

“…A direct emission factor for N 2 O from N inputs (mineral and organic) applied to soils is 0.01 kg N 2 O-N/kg N input [22]. Several mitigation strategies have been developed to decrease the N emissions in agroecosystems, including the application of urease and/or nitrification inhibitors (UI and NI) [20,21,23,24]. NIs delay the bacterial oxidation of NH 4 -N by depressing the activities of nitrifiers in soil, whereas UIs slow down the hydrolysis of urea to NH 4 -N by preventing its binding to the enzyme urease [23,25].…”