In Italy, the most widespread cool-season turfgrass is tall fescue (
Festuca arundinacea Schreb.) [
1]. Tall fescue is noted especially for its wear resistance, weed competition, shade tolerance, and deep root system. Compared to other cool season turfgrass species, tall fescue is the most resistant to drought, high temperatures, and salinity [
2]. For sports turf applications, tall fescue is not commonly used, since it has difficulty withstanding low mowing heights [
3] and its leaves tend to partially wither in winter [
4]. Burns [
5] revealed how tall fescue is affected by mowing height, showing that the best quality was achieved at heights ranging from 2.5 to 4 cm. In addition, several authors have studied dwarf-type tall fescue cultivars selected to withstand low mowing. Based on the lower growth rate of these cultivars, appropriate levels of fertilization and mowing are required [
6,
7,
8]. Grossi et al. [
9] studied the effects of low mowing height (ranging from 1.0 cm to 2.5 cm) on two cultivars of tall fescue. The highest quality was achieved with the lowest mowing height, proving that tall fescue cultivars selected to withstand low mowing heights are suitable for sports turf applications. Dernoeden et al. [
4] studied the effects of mowing, nitrogen fertilization, and herbicides on the weed management of tall fescue turf. The two main species of weeds found in tall fescue turf were crabgrass (
Digitaria ischaemum Schreb.) and white clover (
Trifolium repens L.). Herbicides were effective in controlling weed populations, irrespective of nitrogen fertilization. High mowing (8.8 cm) was the best cultural management for reducing crabgrass infestation. Mowing at lower heights (3.2 and 5.5 cm) led to higher crabgrass infestation. White clover, on the other hand, was more competitive as the tall fescue height increased. In contrast, Burns [
10] observed a larger infestation of white clover in tall fescue mowed at 4.0 cm compared to tall fescue mowed at 8.0 cm. Burns also found that tall fescue density was higher after three years when mowed at 8.0 cm. Turf mowing originally required human labour. The height and frequency of mowing were performed in order to respect the “1/3 rule”, which means that mowing does not involve more than one third of the total height of the grass, in order to prevent scalping and physiological stress [
11]. The most widespread lawnmowers in Italy are electric rotary mowers for small gardens and gasoline-powered rotary mowers for larger gardens [
12]. However, autonomous mowers are becoming more common. The first autonomous mower was produced in 1995 by Husqvarna, a Swedish company, and was powered by solar energy. Current autonomous mowers are battery-powered machines that autonomously perform turfgrass mowing. Autonomous mowers usually move randomly within a precise perimeter for a predetermined period of time. The perimeter is defined by a shallow-buried boundary wire which generates an electro-magnetic field. Once the autonomous mower reaches the boundary wire or an obstacle, it stops and changes direction. However, autonomous mowers do not know which areas have or have not been cut. Given a sufficient time interval, the autonomous mower is likely to cut most of the lawn [
13]. It is an effective solution to cover areas with many obstacles, but leads to frequent overlapping [
14]. There are various alternative ways to prevent mowing overlap. Chandler [
13] developed a texture-based vision system to enable the autonomous mower to detect where the grass has already been cut. The working capacity of autonomous mowers designed for private or industrial areas ranges from 400 to 5000 m
2. The largest autonomous mowers can manage up to 30,000 m
2 [
15,
16]. To prevent mowing overlap, autonomous mowers working on large areas can be equipped with a GPS which provides a “random assisted” pattern [
17] or with differential GPSs for systematic trajectories [
16]. Autonomous mowers can be equipped with razor-like pivoting blades mounted on a cutting disc [
17,
18] or with solid blades, with three or four cutting edges [
16,
19]. Autonomous mowers have several advantages. Firstly, although autonomous lawn mowers do not replace humans managing turfgrass (professionals or just lawn owners), they help to save a great amount of time. Time saving enables the person managing the turf to have time for other turf management operations or simply for other purposes. Not having to mow the turf also prevents humans from coming into contact with dust, allergens, polluting gasses (if the engine is a gasoline engine), and noise [
14,
20]. Secondly, autonomous mowers do not produce polluting gasses or dust. Thirdly, they are so silent that they can perform the mowing even at night. Fourthly, given that autonomous mowers are usually programmed to operate every day, the clippings are very small and are left in place. Autonomous mowers do not collect clippings, which become integrated into the turf and thus recycling nutrients. This process is called “grasscycling”. Grasscycling leads to a higher turf quality, lower weed percentage, lower need for nitrogen fertilization, and does not contribute to the formation of thatch [
21]. However, there are some differences between the effects of autonomous mower clippings and ordinary mulching rotary mower clippings. Ordinary walk-behind rotary mowers are usually used following the “1/3 rule”. Clippings from ordinary walk-behind rotary mowers are generally larger than clippings from autonomous mowers. Macolino and Ziliotto [
22] observed that ordinary rotary mower clipping release in tall fescue led to a severe reduction of root density and root length, losing up to 45% of total root weight. Ferguson and Newell [
23] observed the effects of the autonomous mower, Bigmow, compared to a reel mower. Turf mowed by Bigmow had a lower disease incidence and lower broad-leaved weed infestation. In some studies on
Poa pratensis L. and
F. arundinacea Schreb. [
24,
25,
26], mulching has increased turf quality compared to mowing with clipping removal. Mulching also improved turf colour in the autumn and winter, and did not lead to any variation in thatch thickness. Grossi et al. [
27] compared the effects of mulching and mowing with clipping removal in a tall fescue turf. Turf quality and turf colour were higher when mulching was performed. Thatch was not influenced by the mowing system. Weed control is an important task in turf management. Weeds can greatly reduce turf quality. Any stress factor that reduces turfgrass cover, such as poor management practices, disease, or extreme environmental conditions, can result in weed infestation. As previously mentioned, weed control in turfgrass over the years has mainly been performed with chemical herbicides. However, the use of chemical herbicides has been increasingly restricted because of their highly negative impact on the environment and on human health. The trend is to find alternative solutions for weed control in turfgrass based on management practices in order to reduce the use of chemical active ingredients. To date, very little is known about the effects of autonomous mowers on weed control. The main purpose of this trial was to compare the effects of an autonomous mower, an ordinary gasoline-powered mower, and nitrogen (N) fertilization rates on weed development in an artificially infested tall fescue (
Festuca arundinacea Schreb.) turf. The trial was carried out to simulate the spontaneous weed infestation of a cool-season turf with different nitrogen (N) levels, and to evaluate the turf quality and energy consumption of the two mowing systems.