Developing different robotic platforms for farm operations is vital to addressing the increasing world population. A harvesting robot significantly increases a farm’s productivity while farmers focus on other relevant farm operations. From the literature, it could be summarized that the design concepts of the harvesting mechanisms were categorized as grasping and cutting, vacuum suction plucking systems, twisting and plucking mechanisms, and shaking and catching. Meanwhile, robotic system components include the mobile platform, manipulators, and end effectors, sensing and localization, and path planning and navigation. The robotic system must be cost-effective and safe. The findings of this research could contribute to the design process of developing a harvesting robot or developing a harvesting module that can be retrofitted to a commercially available mobile platform. This paper provides an overview of the most recent harvesting robots’ different concept designs and system components. In particular, this paper will highlight different agricultural ground mobile platforms and their associated mechanical design, principles, challenges, and limitations to characterize the crop environment relevant to robotic harvesting and to formulate directions for future research and development for cotton harvesting platforms.

Delineating the depth and extent of the watermelon [ Citrullus lanatus (Thumb.) Matsum. & Nak.] root zone assists with proper irrigation management and minimizes nutrient leaching. The objective of this 3-year field study was to measure root distribution and root length density of watermelon (cv. Wrigley) grafted on two different rootstocks ( Lagenaria siceraria cv. ‘FR Strong’ and Cucurbita moschata × Cucurbita maxima cv. Chilsung Shintoza) and grown under three soil moisture treatments. Irrigation treatments tested were: no irrigation (NI), briefly irrigated for fertigation and early-season plant establishment; minimally irrigated (MI), irrigated when soil moisture in top 0.30 m of soil fell below 50% available water capacity (AWC); well irrigated (WI), irrigated when soil moisture in top 0.30 m of soil fell below 15% (AWC). Root length density (RLD) was measured from 75-cm-deep soil cores at two locations three times per growing season and a third location at the end of the season. Cores 1 and 2 sample locations were 15 cm to the side of each plant: Core 1 on the same side as the drip tape and Core 2 on the opposite side. At the end of the season, Core 3 was taken 15 cm outside of the bed in bare ground. RLD was significantly greater in the 0- to 30-cm soil depth and dropped dramatically below 30 cm; it was not significantly affected by irrigation treatment or rootstock. Core 1, next to the drip tape, had greater RLD than Core 2, 30 cm from drip tape, but only at the later sampling dates. Roots were found in Core 3 at all depths, but the RLD was significantly less than that measured in Cores 1 and 2. These findings suggest that the effective root zone depth for watermelon is 0 to 30 cm and that the particular scion/rootstock combinations tested in this study do not differ in root system size or location.

Cotton (Gossypium hirsutum L.) is an important industrial crop. It is a perennial crop and has indeterminate growth habit, however, in most parts of the United States, it is grown as an annual crop with the application of growth regulators. Defoliation is a major production practice influencing harvester efficiency, fiber trash content, cotton yield, and fiber quality. Currently, defoliant application is done by using a conventional boom sprayer and aerial spraying in which both systems spray chemicals horizontally downwards from the top of the canopy, which causes minimal chemical to reach at bottom canopy. However, for successful defoliation, each leaf must receive the defoliant as chemicals do not move within the plant. Thus, a new autonomous ground sprayer was developed using robotics and pulse width modulation, which can be run in between two rows covering the whole canopy of the plant. Field research was conducted to study the effect of three duty cycles (20%,40%, and 60%) on cotton fiber quality using autonomous spraying system. The result indicated that the defoliants could be applied safely at either of the three duty cycles without compromising most of the fiber quality parameters except for nep/gm, length (Ln), L (5%), SFC, trash content in field 1 and micronaire, nep size, length (Ln), L (5%), SFC, and fiber fineness in field 2 which were significant. However, application of 20% duty cycle will significantly reduce the chemical use therefore, 20% duty cycle could be a good choice for the autonomous cotton defoliation. The development of autonomous spraying technology would encourage the development of new sprayer industries and the unmanned ground vehicle industries, together with the need for the global development of an agricultural system with broad market prospects and brings about huge economic, social, and ecological benefits.

Chemical spraying is one of the most important and frequently performed intercultural agricultural operations. It is imperative to select the appropriate spraying technology as a selection of ineffective one leads to the wastage of a considerable volume of applied chemicals to the non-target area. Many precision technologies have been developed in the past few decades, such as image processing based on real-time variable-rate chemical spraying systems, autonomous chemical sprayers using machine vision and nozzle control, and use of unmanned aerial and ground vehicles. Cotton defoliation is a natural physiological process, but untimely and inadequate leaf defoliation by natural process hinders the mechanical cotton harvest. Induced defoliation is practiced by applying defoliants to address the issue with the natural process of defoliation. This paper covers spraying technologies in agriculture, cotton plants, cotton defoliation, new defoliant spraying systems, and the recent field test. The new spraying system attached to an autonomous mobile robot aims to improve the delivery of defoliant chemicals by adding a spray unit on the side of the plant. Preliminary results of the water-sensitive paper test at the field showed adequate penetration with low flow rates. This is a huge development as there is a huge potential to save on the cost of applying defoliant chemicals.

Intercropping of seedless watermelon [ Citrullus lanatus (Thumb.) Matsum. & Nak.] and cotton [ Gossypium hirsutum (L.)] in the eastern geographical area of South Carolina requires changes in normal crop-management programs but has the potential to improve grower profits compared with typical production of each crop separately. The alteration and timing of several normal crop-production practices for both crops can present challenges and must be well-defined for successful intercropping of watermelon and cotton in the region. Notable adjustments in production for watermelon are delayed planting date, reduced row spacing and bed width, and modification of herbicide applications. Significant changes in normal cotton production also include modification of herbicide applications, but additional considerations, such as temporal limits on side-dressed fertilizer and insecticide applications, are needed because of the raised beds and plasticulture used for watermelons and also because of labeling restrictions for pesticides across crops. Research was conducted to 1) identify modifications in standard crop-management procedures for watermelon and cotton intercropping; and 2) determine the feasibility and profitability of intercropping the crops. Although there was a slight numerical reduction in intercropped watermelon yield each year, there were no significant differences in total watermelon yield between intercropping and watermelon monoculture in any of the years. There were also no significant differences in watermelon fruit quality parameters (size, brix, hard seed, hollow heart) in any of the years. Intercropped cotton yield was significantly less than monoculture cotton yields in each of the three years. The net income from intercropping in each year was slightly less than the net income from watermelon monoculture.

Delineating the depth and extent of the industrial hemp ( Cannabis sativa L.) root zone assists with proper irrigation management and minimizes nutrient leaching. The objective of this 3-year field study was to measure root distribution and root length density of industrial hemp cultivars produced for cannabinoids grown under polyethylene mulch with drip irrigation. Root length density (RLD) was measured from 75-cm-deep soil cores obtained during vegetative growth, at early bloom, and at flower harvest. Cores were taken in-row and 15 cm to the side of each plant. In addition to root cores, the trench profile method was used during 2020 to observe in situ gross root architecture of a direct-seeded cannabinoid cultivar. RLD was significantly greater in the 0- to 30-cm soil depth and dropped dramatically below 30 cm; RLD was not significantly affected by cultivar. These findings suggest that the effective root zone depth for industrial hemp cultivars produced for cannabinoids is 0 to 30 cm and that the cultivars tested in this study do not differ in root system size or location.