Models of the optimal distribution of fertilizers and vehicles in grain production Abdizhapar Saparbayev, Aiymzhan Makulova, Azamat Eleusov, Ulzhan Meirmanova and Zaure Klyshbayeva E3S Web Conf., 280 (2021) 06002 Published online: 30 June 2021 DOI: 10.1051/e3sconf/202128006002