Mixture of NPK 4-14-8 with MAP as an alternative for the planting fertilization of 'Atlantic' potato

Two experiments were carried out to evaluate whether the mixture of MAP to NPK 4-14-8 to maintain the P dose and reduce N and K amounts at planting according to nutritional demands of 'Atlantic' potato could maintain or increase yields and the specific gravitys of commercial tubers. In both experiments, a randomized block design was used, with 6 treatments and five replications, being: 0) Control, without fertilization of planting; 1) Standard treatment with 3 Mg ha-1 of NPK 4-14-8 (120, 420, 240 kg ha-1 of N, P2O5 and K2O, respectively); 2) 25% of the P2O5 dose as MAP; 3) 50% of the P2O5 dose as MAP; 4) 75% of the P2O5 dose as MAP and 5) 100% of the P2O5 dose as MAP. In soil with very high levels of P and K, the 'Atlantic' potato crop does not respond to traditional fertilization with NPK 4-14-8, NPK 4-14-8 mixtures with MAP and or to isolated MAP application. In soil with low P and K average values, the application of 420 kg ha-1 of P2O5, half as NPK 4-14-8 and half as MAP, halved the amounts of N and K in the planting and maintains the marketable yields and N, P and K exports of tubers relative to fertilization with 3 mg ha-1 of NPK 4-14-8.