Input Voltage: 24V
Current Draw: 160mA
Use a multimeter to measure the valve's DC resistance. If you measure 150 ohms then it is specified for DC: 24V/150R = 160mA. If you measure a much lower resistance value then it's probably specified for AC.
However the FarmBot's power supply is 24V DC so the solenoid is most likely specified for 24V DC.
So... problem is to convert 46V AC into something that can drive your valve. I assume it's 46V RMS, not peak, right?
Simplest solution would be to measure the AC current in the solenoid with 46V AC power and add a 5W resistor in series to drop current to 160mA RMS. Resistor value will depend on solenoid inductance, so you can either measure the inductance and do the math, or wing it and try various values.
If it still vibrates and groans, then maybe it is designed only for DC. In this case you'll need a rectifier and a way to drop the voltage down. You could use a 1:2.5 transformer to drop 46VAC down to 18.5VAC which should end up close to 24V after rectification and smoothing. If solenoid inductance is high enough you may not need a smoothing cap.
A 1:2.5 transformer is basically an off the shelf 110V to 48V transformer (more or less) with output current of at least 160mA, so 10-20 VA.
You could also just rectify and smooth the 46VAC power which will give about 64VDC but then you'll need a step down converter which is probably going to be hard to find given the unusual voltage.
So here's a simple 2-transistor hysteretic switching constant current driver. The inductance L1 is the solenoid, Rs is its internal resistance.
When it is powered up, D2/D3 create a 1.2V reference and Q1 turns on, trying to keep its emitter at 0.6V above ground. Q1's collector current turns Q2 on, and current begins to rise in the inductor. When current through L1 is high enough so voltage on R1 reaches 0.6V, then Q1 turns off, turning Q2 off, and current decreases. Then the cycle repeats. C2 is the important part as it provides feedback and hysteresis which allow the circuit to oscillate. C2 also sets the oscillator frequency. Without C2 it would be a simple linear constant current driver.
Simulated switching waveforms:
Note this circuit has an "ENABLE" input to turn it on or off, it's the top of R6 which is connected to the power supply, but you can use a signal from a microcontroller or anything else to control it.