Otago, Southland and Canterbury - all previously regions of rapid dairy expansion - have seen the most pronounced decline in the value of farm building consents over the past six months.
Values have fallen significantly over the past 12 months and, for the year to February, were 18% lower than the same period a year earlier, BNZ's latest Rural Wrap said.
While monthly consents could be highly volatile, it appeared consents had taken another tumble over recent months.
The $68million decline in the annual value of farm building consents since its most recent peak 18 months ago would, in all likelihood, understate the reduction in overall farm spending associated with that activity, the report said.
For example, it did not include the expenditure on professional services associated with the building activity or on any spending related to building fit-out from the likes of manufacturers.
The reduction in primary incomes over the past 18 months was having flow-on effects to other industries but it was difficult to tell the overall extent of that.
There had been a huge hit to dairy income, along with softness in grain prices and below-average lamb returns, the report said.
But there had also been some positives, such as buoyant beef prices, above-average venison prices, higher wine returns, rising forestry prices, better wool prices, good apple returns and rapid kiwifruit volume growth, which were helping to cushion the negatives.
While there was no shortage of anecdotal evidence of, and comment on, reduced farmer spending, there was no overall spending measure for the primary sector so it was impossible to be precise.
One indicator of farm spending was wholesale sales of basic materials, including agricultural product wholesaling and agricultural chemical wholesaling.
Latest quarterly figures showed those sales were 3.8% down on a year ago.
Another indicator was wholesale sales of machinery and equipment, which included agricultural and construction machinery.
Latest figures showed those sales were 2.5% lower than a year earlier.
In the year to February this year, tractor registrations averaged 236 per month, which was 4% lower than the average over the previous year.
Agricultural debt was trending higher, standing at $59billion at the end of February, which was $4.6billion, or 8.4% higher than at the same point a year ago.
The low level of farmer confidence and current investment intentions did not point to a rapid turnaround in primary sector spending in the near term, the report said.
