Tamanhos de tubérculo-semente e doses de fertilizante e gesso no crescimento e produtividade da cultura da batata

Abstract

The objective of this study was to identify the effect of fertilizer rates and sizes of seed potatoes on growth, yield and profitability of potato cultivation, in addition to verifying the efficiency of the use of gypsum as a calcium source, aiming at complementing the smaller doses of the fertilizer NPK 4-14-8, in the region of Guarapuava, Paraná state. Three experiments were conducted in the region, one in commercial potato crop, from December 2010, and other two experiments in a greenhouse with plastic cover on Campus CEDETEG of Midwestern State University, in July/August and August/September 2012, 1st and 2nd experiment, respectively. In the field experiment the treatments were 0, 2, 4 and 6 Mg ha?¹ of mineral fertilizer 4-14-8 (plot) and seed potatoes type I and III (subplot), arranged in a split plot design in a randomized block design with three replications. In greenhouse, treatments consisted of four fertilizer rates (0, 2, 4, 6 Mg ha?¹) of NPK 4-14-8, and three rates of 2 Mg ha?¹ of the same formulated supplemented with doses of 0.6; 1.2 and 1.8 Mg ha?¹ of gypsum (20% Ca). The analyzed characteristics were: main steam length, number of stems, number of nodes per stem, leaf area index (field experiment) and leaf area (experiments in the greenhouse), total dry matter (DM); fresh weight, DM and number of tubers formed and started. In the field experiment it was determined the maximum agronomic and economic efficiency of fertilizer rates. Data were collected at 7, 14 and 21 days after emergence (DAE) (in greenhouse experiments) and at 24, 41 and 57 DAE, and at harvest (field experiment). Under field conditions, there was no significant interaction between fertilizers rate and potato seed tuber size for any analyzed characteristic. The rate of fertilizer influenced all the analyzed plant characteristics, where, in general, the higher the rates, the higher the values of the characteristics. However, the rates of fertilizers had low effect on the number of stems, which was the characteristic most influenced by the seed size; it was higher in plants from seed type I. The size of the seed potatoes had no influence on tuber yield. The number of tubers initiated showed the same tendency, i.e., plants that received greater doses of fertilizer started greater number of tubers compared with the other plants, and in greenhouse the fertilizer supplementation with gypsum leads to tuber initiation similar to the use of the higher rate of the fertilizer, showing that under the conditions of this study, the use of 2 Mg ha?¹ of the fertilizer 4-14-8 supplemented with rates of 1.2 Mg ha?¹ of gypsum showed the best economic option for tuber initiation. However the maximum economic efficiency was achieved with 3.5 Mg ha?¹ of the fertilizer, concluding, therefore, that the use of rate of 3.5 Mg ha?¹ and seed potatoes type III resulted in the best economical choice for the growers.