Why did the Lindman government choose to resign over their agricultural program? Did (members of) the government expound on why they chose to take the agricultural program as a matter of confidence despite passing half of it successfully?
Today, 90 years ago, on 31st May 1930, the Arvid Lindman's Government's proposal to legislate that all imported grain should be milled along with a proportion of domestic grain in order to support domestic agriculture was halted in a parliamentary committee because the opposition did not approve of this measure. As this was a matter of principle for the government, they prepared to resign, formalized a week later.
Agricultural prices had been rising steadily since about 1925, and the Lindman government therefore submitted a twofold program designed to stabilize internal prices for Swedish wheat and rye. The government proposed on the one hand a higher tariff on cereal imports and on the other hand a regulation according to which all Swedish flour mills would be required to use a certain minimum percentage of Swedish grain. While the Socialists rose to the defense of consumer interests and condemned the entire program, the Liberals rejected the tariff but endorsed the second part of the government proposal. Ekman, once again presiding over committee deliberations, succeeded in getting the special committee that was handling the bill to go along with he Liberal plan. During the floor debate the government remained adamant and made acceptance of the whole program a question of confidence. At this point a large group within the government's own party, fearful lest the entire program be defeated, voted for the committee proposal, which thus carried a majority.
—Rustow, D.A., 'Politics of Compromise'
Carl Gustaf Ekman, the leader of one of the minority parties, replaced Lindman as PM within a week. Yet, as it turns out, this was clearly by Lindman's choice! Further, it looks as if a minority government did not have to resign after a vote loss in the Riksdag:
At the 1929 session a Liberal-Socialist majority defeated three major government proposals---one to introduce a protective tariff on sugar, one to reduce income and property taxes, and one to increase military expenditures in order to strengthen the artillery.
—Rustow, D.A., 'Politics of Compromise'
The sources above (and other, less detailed narratives such as Wikipedia) do not describe the motive as to why Lindman chose to make this a matter of confidence, even though he had failed to pass other tariff issues previously.
The sources also don't describe whether the bill was popular with the public, even if it was not popular with the other Riksdag parties. Lindman's General Electoral League was content to pass a lesser version of the bill despite the party's leader -- based on the narrative we have -- being against that version. There is also no mention of Lindman himself being unpopular as the leader of his party, and given he continued in that position for another five years, it's not clear why the party would disobey Lindman nor why Lindman wanted to go out on this note.
Public descriptions of Lindman also praised his ability to do cross-bench work—something which seems to have been entirely missing from this saga (for some, presently unspecified, reason).
While perhaps not as relevant, it looks as if Ekman's decision in this case was counter-productive with The Great Depression looming. Many other countries explicitly imposed tariffs on imported goods in this period. Ekman suffered for this during his own premiership (from here):
Ekman returned as Prime Minister in 1930, when he and Per Albin Hansson defeated the government's proposal to raise tariffs on grain. His second period as Prime Minister was difficult; the international depression that had begun after the Wall Street Crash of 1929 reached Sweden, affecting both industry and agriculture. Ekman's traditional attitude of thriftiness made it difficult for him to accept economic-stimulation programs that would involve heavy public spending.