  Citation: Assirelli, A.; Ciaccia, C.; Giorgi, V.; Zucchini, M.; Neri, D.; Lodolini, E.M. An Alternative Tool for Intra-Row Weed Control in a High-Density Olive Orchard. Agronomy 2022, 12, 605. https:// doi.org/10.3390/agronomy12030605 Academic Editors: Sudheesh Manalil and Anestis Karkanis Received: 7 February 2022 Accepted: 25 February 2022 Published: 28 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). agronomy Article An Alternative Tool for Intra-Row Weed Control in a High-Density Olive Orchard Alberto Assirelli 1 , Corrado Ciaccia 2 , Veronica Giorgi 3 , Matteo Zucchini 3 , Davide Neri 3 and Enrico Maria Lodolini 4, * 1 Council for Agricultural Research and Economics, Research Centre for Engineering and Agro-Food Processing, 00015 Monterotondo, Italy; alberto.assirelli@crea.gov.it 2 Council for Agricultural Research and Economics, Research Centre for Agriculture and Environment, 00184 Rome, Italy; corrado.ciaccia@crea.gov.it 3 Department of Agricultural, Food and Environmental Sciences, Marche Polytechnic University, 60131 Ancona, Italy; v.giorgi@staff.univpm.it (V.G.); m.zucchini@pm.univpm.it (M.Z.); d.neri@staff.univpm.it (D.N.) 4 Council for Agricultural Research and Economics, Research Centre for Olive, Fruit and Citrus Crops, 00134 Rome, Italy * Correspondence: enricomaria.lodolini@crea.gov.it Abstract: In high-density olive orchards, weed control along the row is pivotal to avoid the compe- tition between the young trees and the weeds to promote a strong vegetative growth of the olives during the first years after planting. Two different mechanical weeders were compared in a high- density olive orchard (1250 trees ha −1 ) planted in 2019. An intra-row hoeing machine (Control) and an alternative system with a high-pressure water blast (Grass Killer) were compared. The treatments were carried out in summer and autumn. The effects of the two control systems were assessed through the weed soil coverage and indirectly through the growth of olive trees. The effect on weeds in summer was marked without showing significant differences between the applied treatments, even if the Grass Killer did not eradicate totally the weeds. In autumn, the hoeing machine showed a higher weeding capacity, even though the presence of weeds along the row treated with the high-pressure water weeder can contribute to reduce the soil moisture in wintertime. No differences were seen for the young olive tree growth. Results showed a good weeding capacity of the alternative machine, and its use can be managed in combination with other mechanical systems. Keywords: green cover management; plant growth; competition; water weed-killing machine; Olea europaea 1. Introduction The renovation of the olive orchards with new intensive planting systems that allow earlier and more abundant yield, and complete mechanization of harvest, is nowadays a reality [1]. Olive growing is expanding in new areas of the world using high-density planting orchards (or as it is known, super-high-density, SHD), generally using few cultivars that recorded overall adaptability to diverse climatic conditions, early bearing, low-vigour and high-yield efficiency characteristics [2–5]. Strong vegetative growth of the plantlets is required during 2–3 years after planting to form the hedgerow and allow an early onset of fruit production. A previous study under the same pedoclimatic conditions has highlighted different canopy behaviours linked to the different cultivars [6]. Weed control along the row is pivotal to reduce the competition for water and nutrients during this early critical period of the tree growth [7]. This competition during the early stages after plantation can be very strong, thus reducing the growth of the young olive trees and delaying the onset of fruit production [8] as reported by different authors [9,10]. In addition, in intensive cropping systems, water provided by drip irrigation contributes to the accelerate vegetative Agronomy 2022, 12, 605. https://doi.org/10.3390/agronomy12030605 https://www.mdpi.com/journal/agronomy