Biofuels grow better when willows weep less

A challenge for biofuels is water use. A successful biofuel strategy will have water-efficient plants.

Climate change doesn’t just mean a change in temperatures. Rainfall is likely to change too. Some areas will get more rain, some less and many may get a greater division between dry and wet seasons. Water use by plants may therefore become a critical factor in growing biofuels. “The great challenge is to optimize trade-offs between carbon harvest and water use by choosing cultivars that combine low water use with high productivity,” said Richard and colleagues in their paper, Optimizing the bioenergy water footprint by selecting SRC willow canopy phenotypes: regional scenario simulations.

Weeping willow
Image: Canva.

They studied the water use of a number of willow genotypes. They examined how water use varied in the LUCASS (light use and carbon assimilation in Salix species) model. They found that narrow leaved willow tended to be much less water-intensive than broad-leaved willow. They also found that crop rotation could make a big difference.

“The difference between 2- and 3-year rotation cycles implies a probability that drought hits more frequently during the first year of rotation in a 2-year rotation and so have more chance of impact on the whole rotation, as shown by our results,” said Richard and colleagues. “In particular, early drought has a negative impact on canopy development and usually results in lowers yields, which, in turn, will have greater impact for a cultivar with a larger canopy. Our results suggest choosing a 3-year rotation management to decrease drought risk and its impact on canopy regrowth after coppicing to improve the performance of small canopy phenotypes on marginal soils under dry conditions.”

Getting the right cultivar could make a big difference to the impact willow plantations have on their local environments. Richard and colleagues said, “High-productivity NL cultivars can save >20 mm of water in droughty years, which is a considerable resource with expanding plantations and changing climate.”