Silicate nutrition and its biological mechanisms involved in water use efficiency in sugarcane and energy cane crops under water deficit

Sugarcane and recently energy cane strengthen the world’s renewable bioenergy production capacity. Notwithstanding, climate change has resulted in droughts that limit their growth. One of the strategies to attenuate water deficit damage in these crops concerns the contribution of silicate nutrition to physiology. This strategy is likely to increase water use efficiency, thus favoring the sustainability of these crops. However, studies on this issue are still incipient. This study assesses whether Si applied via fertigation and foliar spraying in the seedling production phase and as a complement after transplanting to the soil is efficient in attenuating water deficit effects in sugarcane and energy cane. The study further elucidates the physiological and biochemical mechanisms involved in this process. For this, the authors conducted two experiments, one with sugarcane and the other with energy cane. The treatments consisted of a 2 x 2 factorial scheme, with absence (-Si) and presence of Si (+Si) applied via fertigation and foliar spraying; and two water regimes: 70% (no deficit) and 30% (severe water deficit) of the soil water retention capacity. The treatments were arranged in randomized blocks with 5 replications. Silicon supply occurred during the formation phase of pre-sprouted seedlings and during their transplanting to pots filled with samples of Entisols (Quartzipsamments). In the latter, water regimes were induced from 7 to 160 days after transplanting. Severe water deficit reduced the water content and water potential of plants, inducing oxidative stress and impairing gas exchange and photosynthetic water use efficiency, with a consequent reduction in plant growth. Silicon supply via fertigation in association with foliar spraying in the seedling formation phase with complementation after transplanting was efficient in increasing the accumulation of the element in the plants. Silicon was effective in attenuating severe water deficit damage until initial culm formation through mechanisms that maintain water and physiological balance by favoring the antioxidant defense system in sugarcane and energy cane plants.