Abstract: A method for treating plants comprises estimating a growth state or maturity state of a plant based on a planting date, a current date and the crop type of the plant. A root zone estimator or data processor estimating a size, diameter or radius of a root zone of the plant based on the determined growth state or maturity state. The data processor adjusts a lateral offset of a distribution pattern of a crop input or nutrient from at least one nutrient knife based on the size, diameter or radius of the root zone and safety zone about the root zone, where the at least one nutrient knife tracks a path outside of or bounded by the root zone.

Abstract: The spike wheels of the harrow are arranged in gangs to rotate about a common axis during ground engagement. Each wheel has a plurality of spikes that project outwardly from a cylindrical hub having a pair of opposite ends. Projections at one end of the hub are matingly received within notches in the opposite end of the hub of the next adjacent wheel so that the wheels are interlocked for rotation in unison. The projections on each hub are offset angularly from the notches by a certain amount so that adjacent wheels are correspondingly rotatively offset from one another. The outermost tips of the spikes of each wheel are inturned to a certain extent so as to render each wheel generally concavo-convex, with the concave sides of the wheels leading as the machine is pulled through the field. Front gangs of the wheels are disposed in a certain oblique attitude with respect to the path of travel of the machine, while rear gangs are disposed in opposite oblique attitudes.