The Agriculture Department will make Australian Public Service history this month as it embarks on an unprecedented fifth attempt to convince its employees to accept a new deal on pay and workplace conditions.

Agriculture's 4100 public servants do not appear to be looking kindly upon the proposed deal and their main workplace union says the objections have little to do with sickies.

Top of the bosses' agenda in the new proposal is their long-held desire to be able to force employees to provide medical evidence when they call-in sick.

Agriculture's record on "unscheduled absence" is bad and getting worse.

The average departmental employee clocked up nearly 15 days, or three working weeks, in no-shows in the 2015-2016 financial year, even more than the previous year and way above the public service average, with four-fifths of the days-off put down to illness.

"Supporting evidence" is rarely required from Agriculture Department public servants taking sick leave.

It takes an intervention from departmental secretary Daryl Quinlivan to force the production of a sick note and even then the request for a medial certificate must be put in writing with reasons why documentation is required.

Mr Quinlivan made his feelings clear in early 2016, during a previous attempts to get a proposed enterprise agreement over the line, telling his workers he wanted to stop the "misuse" of personal leave.

There has been no direct appeal from the secretary this time, but the material distributed to staff encouraging a yes-vote goes straight to the point, stating that a medical certificate or other evidence would be required after eight no-shows in a year or three consecutive days.

The department's pitch says the proposed agreement is "drafted jointly with [Community and Public Sector Union, [is] easier for you to read, includes conditions and entitlements and confirms consultation and representational rights."

The proposed EA also offers a front-loaded 6 per cent pay rise, with all of it to be paid in the first 18 months of the three year deal.

But the CPSU is still urging its members to reject the deal "because despite the offer having improved since the fourth no-vote, the offer is still not as good as your current agreement and reduces your conditions and rights."

The union cites the loss of a public holiday at Christmas-time, the removal of consultation rights on rostering and the end to a commitment to permanent jobs as the "usual basis" for working at the department among many other reasons to vote-no.

"It's disappointing that in the recent round of staff meetings, when [departmental] management were seeking feedback, that they have failed to make a single improvement to their draft EA offer despite clear and consistent feedback from staff and the CPSU on the above issues," the union recently told its members.

The ballot commences on Tuesday, 13 June 2017 and closes on Friday, 16 June 2017.