Statistics New Zealand figures released yesterday showed a surplus of $534 million compared with market expectations of $634 million.
Westpac predicted a $700 million surplus and ASB a $900 million surplus.
Exports were $4.5 billion - a $553 million increase since April last year, and led by milk powder, butter and cheese - while imports lifted 5% to $4 billion.
Most of the month's weakness was on the export volumes side, which ASB rural economist Nathan Penny attributed to normal volatility in the monthly trade data.
Seasonally-adjusted dairy volumes were down more than 5% for the second consecutive month, despite what had been a very strong end to the dairy production season.
Meat and forestry volumes were also down, compounding the ''downside surprise''.
Export volumes were expected to rebound over coming months.
From next month, he expected the trade data to begin to reflect recent GlobalDairyTrade auction price falls.
In imports, capital imports continued to lead the way, reflecting the purchase of equipment for the Canterbury rebuild, as well as for the commodity export boom.
Households continued to show restraint and spending on imports was lagging the rest of the economy, Mr Penny said.
