Making better use of water is becoming increasingly important for vegetable growers as droughts put crops under pressure. One way to assess how efficiently crops use water is water use efficiency (WUE). Generally, WUE describes crop yield relative to the amount of water used or supplied. Depending on the assessment method, this can refer to water inputs from precipitation and irrigation or to evapotranspiration (ET), which combines evaporation from the soil and transpiration by plants.
Can covering the soil with organic material make a difference?
Testing transfer mulch in pointed cabbage
In 2025, Hochschule Geisenheim University investigated this question in a field trial with pointed cabbage. Cabbage grown on uncovered soil was compared with cabbage grown on soil covered by a layer of clover–grass transfer mulch, applied approximately two weeks after planting.
What did the trial show?
The mulched treatment showed numerically higher water use efficiency than the unmulched control. When calculated based on cumulative water input, WUE was 11.6% higher under mulch. When considering evapotranspiration, the difference was even greater, with a 20.1% higher of WUE under mulch. Both indicators express marketable fresh-mass yield per unit of water supplied or lost through evapotranspiration. These findings suggest that organic mulching has the potential to improve water productivity.
What does this mean for growers?
Covering the soil with organic material can help retain moisture and may reduce unproductive soil evaporation. Mineral fertiliser applications were reduced in the mulched plots to account for the estimated nutrient contribution from decomposing clover–grass. This aimed to provide comparable nutrient supplies across treatments, although differences in nutrient release and availability cannot be ruled out. These first-season results suggest that mulch could support more water-efficient vegetable production. Further trials are needed to establish how consistently these benefits occur under different growing conditions.
