Análise econômica sobre adubação com sulfato de zinco via foliar na produção do cafeeiro (Coffea arabica L.)

Abstract

This work was carried out with the objetive of studyíng the economic effect of zinc sulphate applied on the leaves of coffee plant (Co£&2.cl aH.abi.ccL L, cultivar Bourbon). The amount of zinc sulphate as we11 as the time period were determined in order to help the coffee farmer to decide which and how much fertilizer should be used taking into account the price ratio fertilizer - coffee gram. Data were collected from the experiment on Distrophic Dark Red Latossol (Orthox) carried out by SILVA (52) in the "mu nicípio" of Nepomuceno, Minas Gerais, from 197** to 1976. The experimental design was randomized blocks, split- -plot on time, with eleven treatments and two rep1 ications . The amount of zinc sulphate (ZnS0\ 7H20 - 22% Zn) were: 0,0; 1,0; 2,0; 4,0; 6,0; 8,0; 10,0; 12,0; U,0; 16,0 e 18,0 grams/plant/ year. Foliar spray was in October for the treatment 1,0 and 2,0 and splitted in October and March for the other treatments'. The effect of each treatment was analized based upon coffee yield, during three consecutive years. The theoretical method utilized was based upon yield economy in which zinc sulphate was the variable input. Q_uadratic, cubic, transcendental and Mitscherlich production functions were tested. Statistical results showed that cubic function was the one best fitted for coffee plant yield. By using the average moving method, price stability was set from January 1381 to December 1986. The monthly carrected prices were used as a basis to calculate price re1 ationships. The zinc sulphate rate was found to vary from 5,kk to 5,^6 grams/p1ant/year and divided into two parts in themonths of October and December. The general concl usion is that the econornic amount was almost the same as the maximum yield amount. A one gram reduction will not occur until the price is 30 times higher than the processed coffee price what will hardly occur since the price of fertilizer was found to be lower than that for coffee ki logram.