Pre-sprouted Sugarcane Plantlets Produced in Ebb-and-flow Subirrigation Automated by Soil Moisture Sensors

Abstract

There is a growing demand for innovation in the sugarcane production chain to increase crop productivity. The recent use of sugarcane plantlets to improve planting efficiency in the field is a viable option, and nurseries are seeking for enhanced irrigation systems to accelerate the production of high-quality plantlets and optimize water and fertilizer inputs. This research aimed to determine the adequate substrate volumetric water content (VWC) to produce pre-sprouted sugarcane plantlets using ebb-and-flow subirrigation automated by soil moisture sensors and the effects on plant growth in greenhouse on acclimation stages #1 and #2. We tested three thresholds to trigger subirrigation automatically when sensor readings dropped below the setpoints: VWC 45% (v/v), VWC 35%, and VWC 25%. Plantlets were cultivated in 54-cell flat trays with 130-cm3 cone-shaped containers filled with commercial substrate in ebb-and-flow benches controlled by capacitive soil moisture sensors connected to a datalogger. The results indicated the automated subirrigation system worked properly, successfully irrigating the plantlets based on the target VWC. VWC 35% was the most efficient treatment, reducing fertilizer solution consumption in 44.78% (368.47 L and 2.41 mm d−1) in comparison with VWC 45% (667.28 L and 4.37 mm d−1) and increasing water use efficiency in 43.18% (7.62 g L−1) when compared to VWC 45% (4.33 g L−1), which produced less biomass with the same amount of water. VWC 45% treatment also resulted in the highest number of irrigation events, with the greatest electrical conductivity value in the substrate at the end of the experiment. All plant growth variables such as stem diameter, plant height, first ligule height, and shoot and root dry weight responded positively to the increase in VWC (P < 0.05). VWC 45% resulted in the highest biomass except root dry weight where VWC 35% was superior. VWC 35% was statistically the same to VWC 45% in all biometric responses (P < 0.05) and showed the best efficiency rate in fertilizer solution consumption and water use. Based on our results, we recommended VWC 35% as the setpoint for water management to produce pre-sprouted plantlets using automated ebb-and-flow subirrigation.