The leader of Poland's United Peasants' Party resigned in a dispute over who will head the Agriculture Ministry in the new, Solidarity-dominated government. Roman Malinowski quit when Prime Minister Tadeusz Mazowiecki insisted in nominating Czeslaw Janicki, a Peasants' Party member party leaders do not support. Malinowski, 54, has been under growing criticism in the party for failing to adapt to liberalization in Poland. He was replaced by Dominik Ludwiczak, a party vice chairman. Party leaders had wanted Kazimierz Olesiak, also a party member, to keep the agricultural post he held in the outgoing Communist government. The new Cabinet is to be sworn in today.