Wheat and maize growers farming saline or alkaline soils have new research to consider — a two-year field trial published in the Journal of Soil Science and Plant Nutrition found that wood vinegar applied as a foliar spray increased wheat yields by 12.4 to 44.3% and maize yields by 6.8 to 13.7% in a saline-alkali cropping system. The research also found wood vinegar enhanced fertiliser efficiency, with nitrogen utilisation significantly improving when wood vinegar was combined with urea humate.

The trial was conducted over two consecutive seasons on saline-alkali soils using a wheat-maize rotation — one of the most common broadacre cropping systems. Seven treatments were tested, combining three rates of urea humate (none, 50%, and 100%) with and without foliar wood vinegar applied at 90 litres per hectare. A no-nitrogen control was included as a baseline.

The yield results were notable. Wood vinegar applied alone — without urea humate — produced wheat yield increases of 12.4 to 44.3% depending on the season. Maize yields increased by 6.8 to 13.7%. When wood vinegar was combined with urea humate, nitrogen use efficiency improved significantly relative to urea humate alone, pointing to a synergistic effect between the two inputs.

The soil biology findings were equally significant. Compared to the no-urea-humate treatment, microbial biomass carbon increased by 9.8 to 24.9% and microbial biomass nitrogen by 18.1 to 29.2% by the end of the two-year trial. Urease activity — an enzyme involved in nitrogen breakdown that can drive nitrogen losses when elevated — decreased by 16.6 to 25.0%. At the same time, mineral nitrogen in both ammonium and nitrate forms increased through the top 40 centimetres of the soil profile, indicating improved nitrogen availability for plant uptake.

For dryland and irrigated grain growers managing saline or sodic soils, the combination of factors here is practically significant. Saline-alkali soils constrain microbial activity, nitrogen availability, and crop productivity simultaneously. The findings suggest that wood vinegar, particularly when used alongside humate-based fertilisers, may address several of these constraints at once — supporting soil biology, retaining nitrogen in plant-available forms, and reducing enzyme-driven nitrogen losses.

The two-year duration adds credibility to the results, as single-season pot trials often fail to capture soil biology changes that accumulate over time.

Source: Combined Urea Humate and Wood Vinegar Treatment Enhances Wheat-Maize Rotation System Yields and Nitrogen Utilization Efficiency Through Improving the Quality of Saline-Alkali Soils — Sun et al., Journal of Soil Science and Plant Nutrition, 21, 2021 (https://doi.org/10.1007/s42729-021-00477-1)

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