Impact of urease and nitrification inhibitor on NH₄⁺ and NO₃⁻ dynamic in soil after urea spring application under field conditions evaluated by soil extraction and soil solution sampling

Abstract

The application of mineral nitrogen (N) fertilizers is one of the most important management tools to ensure and increase yield in agricultural systems. However, N fertilization can lead to various ecological problems such as nitrate () leaching or ammonia and nitrous oxide emissions. The application of N stabilizers (i.e., inhibitors) combined with urea fertilization offers an effective option to reduce or even prevent N losses due to their regulatory effect on ammonium () and release into the soil. The present field experiment therefore aimed at soil N speciation dynamics after urea spring fertilization (225 kg N ha−1) in the presence of a urease inhibitor (UI), a nitrification inhibitor (NI), both inhibitors (UI+NI) or when no inhibitor was applied at all. The study focused on the distribution of N species among soil matrix and soil solution. Plant cultivation was completely omitted in order to avoid masking soil N turnover and speciation by plant N uptake and growth dynamics.Application of UI clearly delayed urea hydrolysis in the top soil, but a complete hydrolysis of urea took place within only 10 days after fertilization (DAF). Nitrification was significantly reduced by NI application, leading to higher and lower concentrations in treatments with NI. Due to sorption of to the soil matrix a significantly larger fraction of was always detected in the soil extracts compared to soil solution. However, while in soil extracts the impact of NI application was less apparent and delayed, in soil solution a quick response to NI application was observed as revealed by significantly increased soil solution concentrations of . Because of the “asymmetric” soil phase distribution soil solution was predominant over only initially after fertilization even in inhibitor treatments (≈ 8 to 10 DAF). Nevertheless, inhibitor application tended towards closer ratios of to concentration in soil solution and hence, might additionally affect concentration dependent processes like plant N uptake and root development. Despite cold spring conditions urea application along with UI and/or NI did not indicate a limited supply of plant available and .

Dynamics of localised nitrogen supply and relevance for root growth of Vicia faba (‘Fuego’) and Hordeum vulgare (‘Marthe’) in soil

“…The temporal and spatial resolution chosen for soil solution collection was sufficient to illustrate the change in NH 4 + to NO 3 − ratio and absolute concentrations over time as well as the change in pH associated with N transformation in soil and plant N assimilation. Although the absolute numbers are smaller, similar tendencies for N-dynamics were found in a field study by Kirschke et al 60 , using similar types of urea fertilisers. The large discrepancies between NH 4 + and NO 3 − ratios in soil solution compared to soil extraction nicely illustrate the problem of transferring concentration related results from hydroponics and agar plates to soil systems and will be discussed in more detail below.…”

“…Hence, sorption but also the soil specific dynamic equilibrium between absorbed and NH 4 + in solution needs to be taken into account to evaluate the potential for root growth responses to external NH 4 + , NO 3 − and the ratio of both N-forms. As shown here and recently reported by Kirschke et al 60 the soil solution concentration of NH 4 + is maintained at a considerable level by NI application, highlighting nitrification as a key process of in situ NH 4 + concentration and thus, suggest a possible interrelation of soil nitrification rates and root architecture.…”

Seed Yield and Nitrogen Efficiency in Oilseed Rape After Ammonium Nitrate or Urea Fertilization

“…In addition, it must be taken into consideration that most likely a considerable fraction of fertilized ammonium became immobilized by adsorption to the soil matrix, further decreasing ammonium uptake and recovery in the xylem sap. Large amounts of ammonium-N detected in the soil samples ( Supplementary Table 2 ) most likely overestimated plant-available ammonium, because ammonium was extracted with the strong extraction agent KCl that also desorbs ammonium bound to the soil matrix ( Kirschke et al, 2019 ). Urea fertilization stimulated the translocation of urea as N form whenever xylem sap was sampled shortly after fertilization ( Figures 1 , 2 and Supplementary Figure 3 ), which relies on low-affinity and especially high-affinity urea transport systems ( Kojima et al, 2007 ), whose transport capacities are lower than those for ammonium or nitrate ( Tan et al, 2000 ; Arkoun et al, 2012 ).…”

Urease and Nitrification Inhibitors—As Mitigation Tools for Greenhouse Gas Emissions in Sustainable Dairy Systems: A Review

“…Nitrification inhibitors have gained interest as a possible mitigation strategy for lowering N 2 O emissions as well as reducing water pollution associated with use of fertilizers. Some examples of nitrification inhibitors include DCD and DMPP, thiourea, carbon sulfide (CS2), thioethers, ethylene: C2-H2, 2-ethynylpyridine, 3-amino-1,2,4-triazole, N-2,5-dichlorophenyl succinamic acid (DCS), 2-amino-4-chloro-6-methyl pyrimidine (AM), nitrapyrine (NP) and ammonium thiosulphate (ATS) [11], and N-[3(5)-methyl-1H-pyrazol-1-yl) methyl] acetamide (MPA) [75].…”