2017 ASHS Annual Conference

Physical control methods such as cultivation and hand weeding are used to manage weeds in vegetable crops. Hand weeding of the intra-row space to remove weeds not controlled by other methods is effective, but expensive. Furthermore, the pool of laborers available to perform hand weeding is shrinking and increasingly more expensive. Our project objective is to integrate various engineering and automation technologies to develop cost-effective weed control systems for intra-row weed control in lettuce and tomato. Differentiation of crops and weeds is a major obstacle to automation of weed removal. Crop/weed differentiation, in theory would allow for very precise weed detection and removal while leaving the crop untouched. We seek to differentiate weeds from the crop by a marker on the crop detectable by a camera. Three approaches to mark the crop are 1. Physical markers that do not contact the crop plant; 2. Topical markers on the plant; 3. Root absorbed markers that translocate from the roots to the foliage. Physical markers under evaluation include biodegradable plastic straws that are readily detected, indicating close proximity to the crop. The advantage to the straws is that they do not contact the crop and could be used in organic fields. The disadvantage is that the straws stunt the crop when placed in seedling trays with the germinating crop, and growers do not like plastic clutter in the field. Topical markers include easily detectable fluorescent paint applied to the crop plants before or during transplanting. The paint does not contact harvestable portions of the crop. However, crop growth and sprinkler irrigation causes the marker to quickly fade, especially in lettuce. Root absorbed markers have been difficult to implement. The ideal material could be applied as a seed treatment that is absorbed by the growing crop plant and then translocated to foliage where it can be rapidly detected during the first 4 to 5 weeks of growth. The product also must be food safe if it is to be used on crops like lettuce and tomato. Products that we have tested thus far do not translocate readily and are hard to detect unless high doses are applied. The weed control actuator used in the project is an intra-row cultivator under control of the crop detection system. The detection system controls pneumatic cylinders that push cultivator knives in to cultivate intra-row space between crop plants and pulls the knives out to protect the crop.