Three-dimensional dynamics of nitrogen from banded enhanced efficiency fertilizers

Abstract

A range of enhanced efficiency fertilizers (EEFs) have been developed in response to widespread recognition of poor nitrogen (N) use efficiency (NUE) in agriculture; however, their effective utilization is not properly understood when applied in sub-surface bands. This study quantified soil chemical changes and the distribution of N species that arose from sub-surface banding of urea, a controlled release polymer-coated urea (PCU) and urea coated with either nitrification inhibitors (NIs) or a urease inhibitor (UI), over 71 days in a field trial. Banding NIs extended the duration of nitrification inhibition for up to 50 days longer than banded urea, although the duration of NI-conferred inhibition was dependant on the rate of NI-urea application. The UI preserved urea-N at a concentration which was 16-fold higher cf. standard urea over 7 days, but no urea-N was detected after 21 days. This suggests that the NUE benefits of UIs are transient when applied in sub-surface bands. Slow release of urea-N from banded PCU resulted in lower concentrations of N in the soil solution. This reduced N dispersal by ca. 50 mm cf. urea, resulting in a N-enriched zone which was considerably smaller. Relatively benign chemical conditions around PCU bands enabled rates of nitrification (NH4–N:NO3–N ratio of 46%) which were similar to urea. Collectively, these results demonstrate the relative efficacy and risks of the different EEF technologies, when applied in fertilizer bands. This knowledge supports the effective utilization of band-applied EEFs for improved NUE in agricultural systems.

Impact of contrasting fertilizer technologies on N dynamics from sub-surface bands of ‘pure’ or blended fertilizer applications

“…due to waterlogging). This impact on seasonal or product 'life-time' losses has also been reported in several other studies of PCU (Janke et al, 2020;Parkin and Hatfield, 2014) and PCU-urea blends (Schwenke and Haigh, 2019), and is an important consideration for effective CRF utilization.…”

“…However, several trials in sugarcane (Dowie et al, 2019;Wang et al, 2016a), which has a longer N-uptake period, reported similar crop N uptake from lower rates of DMPP-urea than from urea applied at rates 20-25% higher (i.e., industry-standard rates), resulting in greater NUE with this EEF. Recent studies (Janke et al, 2020;Janke et al, 2022) suggest that banding NI and PCU fertilizers may prolong the inhibitory effects and N release from these products, further exacerbating differences in EEF efficacy between long and short-season crops. Additional constraints for improving N uptake from EEFs, despite reduced N losses, can arise due to unfavourable soil moisture dynamics.…”

“…Additional constraints for improving N uptake from EEFs, despite reduced N losses, can arise due to unfavourable soil moisture dynamics. For example, in conditions where the fertilized layer is dry / drying, N largely remains in shallow fertilizer bands, but plant roots may follow moisture down the soil profile (Janke et al, 2020). Moisture dynamics were not addressed in this study but are an important factor in the multi-faceted challenge of synchronising N availability from fertilizer inputs with crop N demand.…”

Integrated field assessment of nitrogen release dynamics and crop recovery of band-applied controlled-release fertilisers

“…In addition, since urea-N was only monitored in the immediate vicinity of the fertiliser band (location #2; Fig. 1) it is also possible that a substantial portion of urea-N was leached into deeper profile layers and was therefore not detected (Janke et al 2020). The irrigation (65 mm to dry soil) applied the day after fertiliser application likely dissolved the urea immediately, with the resultant wetting front moving a significant proportion of this N to soil layers below the fertiliser band.…”

Fertilizer interactions with micronutrients in tropical volcanic soils

“…The addition of high rates of N-P-K fertilizer to soil systems could modify the pH values Janke et al, 2020;Qaswar et al, 2020;Tkaczyk et al, 2020), becoming an important factor to consider for zinc deficiencies/toxicities management and for reducing the zinc leaching from agricultural fields. Regarding papaya and banana production systems, most of the potassium required by the crop is typically applied in a clearly defined area around the plant using KCl sources, which according to Du et al Based on the aspects mentioned above, we hypothesize a possible role of KCl applications in continuous and high quantities for zinc adsorption/desorption and leaching in volcanic soils:…”