Dynamics of mineral nitrogen, water-soluble carbon and potential nitrification in band-steamed arable soil

Summary

Steaming of narrow soil bands prior to sowing is a new technique that reduces the need for intra-row weeding in herbicide-free row crops. However, the steam treatment may eliminate both weed seeds and non-target soil organisms, thereby affecting the nutrient cycling in the soil. This study tested the effect of band-steaming on N and C dynamics in a sandy loam soil that was steamed in situ to
maximal temperatures of 70–90°C using a prototype bandsteamer. Soil samples (0–5 cm depth) were collected during 90 days from band-steamed soil, undisturbed control soil, and control soil treated just mechanically with the bandsteamer. In the steamed soil, ammonium concentrations
increased from 1.1 to 20.3 μg NH4+-N g−1 dry weight
during 28 days. This coincided with an immediate and
persistent inhibition of potential nitrification (33–61%
inhibition during 90 days). Assays of the temperature
response of potential nitrification confirmed the temperature sensitivity and showed an optimum temperature of
27.1°C and a temperature coefficient (Q10) of 1.9. The
effects of band-steaming on concentrations of nitrate and
water-soluble carbon were divergent and stimulatory,
respectively, but generally not statistically significant.
Mechanical effects of band-steaming were negligible. The
observed ammonium surplus could be of agronomic benefit
and should be evaluated in integrated studies of the effects
of band-steaming on crop growth and plant N uptake.