Autonomous Rotary Mower versus Ordinary Reel Mower—Effects of Cutting Height and Nitrogen Rate on Manila Grass Turf Quality

Abstract

High-quality sports turfs often require low mowing and frequent maintenance. Sports turfs often consist of hard-to-mow warm season turfgrasses, such as zoysiagrass (Zoysia sp.) or bermudagrass (Cynodon sp.). Although autonomous mowers have several advantages over manually operated mowers, they are not designed to mow lower than 2.0 cm and are consequently not used on high-quality sports turfs. All autonomous mowers are only equipped with rotary mowing devices and do not perform clipping removal. An ordinary autonomous mower was modified to obtain a prototype autonomous mower cutting at a low height. The prototype autonomous mower was tested on a manila grass (Zoysia matrella) turf and compared its performance in terms of turf quality and energy consumption with an ordinary autonomous mower and with a gasoline reel mower. A three-way factor experimental design with three replications was adopted. Factor A consisted of four nitrogen rates (0, 50, 100, and 150 kg·ha−1), factor B consisted of two mowing systems (autonomous mower vs. walk-behind gasoline reel mower with no clipping removal), and factor C consisted of two mowing heights (1.2 and 3.6 cm). Prototype autonomous mower performed mowing at 1.2-cm mowing height whereas ordinary autonomous mower mowed at 3.6-cm mowing height. The interaction between the mowing system and mowing height showed that the turf quality was higher when the turf was mowed by the autonomous mower and at 1.2 cm than at 3.6 cm. Autonomous mowing not only reduced the mowing quality, but also reduced the leaf width. Lower mowing height induced thinner leaves. Nitrogen fertilization not only increased the overall turf quality, reduced weed cover percentage, but also reduced mowing quality. Autonomous mowers also had a lower energy consumption if compared with the reel mower (1.86 vs. 5.37 kWh/week at 1.2-cm mowing height and 1.79 vs. 2.32 kWh/week at 3.6-cm mowing height, respectively). These results show that autonomous mowers can perform low mowing even on tough-to-mow turfgrass species. They could also be used on high-quality sports turfs, thus saving time as well as reducing noise and pollution.