To solve the long lag time problem, Vondricka and Schulze Lammers proposed a direct nozzle
injection system (DNIS) concept, in which the point where the chemical was injected into the system
was changed to be at the nozzles [11]. This improvement shortened the chemical flow path and hence
reduced the lag time significantly. Subsequently, their team focused on many aspects of this DNIS.
Vondricka addressed on the problem of mixture homogeneity and Doerpmund assessed the
cleanability of this DNIS [12–14]. However, there is still a need to investigate the performance for
DNIS metering and chemical flow rate control, which is the premise for realizing site-specific and
variable-rate application of chemicals.
The objective of this article was to test the injection uniformity of RRVs within a boom section
of the DNIS, to present a closed-loop control method to meter and stabilize the chemical application
rate with the help of a thermodynamic flowmeter, and to evaluate the performance of the control
system and the DNIS by an EC sensor.