EFFECT OF IRRIGATION, LIMESTONE APPLICATION AND COVER FERTILIZATION ON THE KINETIC CONSTANTS OF RESPONSE OF CORN TO THE FERTILIZER NPK 4-14-8 AND CORRELATIONS AMONG SOME PRODUCTIVE VARIABLES

Abstract

In the first experiment, it was performed the evaluation of kinetic constants of some measures of corn growth as a function of levels of fertilization with NPK 4-14-8, in four different ways: without irrigation, with irrigation, irrigation plus limestone, and irrigation plus limestone at seeding plus ammonium sulfate at 35 days. The kinetic constants Ks (amount of fertilizer to reach half maximum response) and Kmax (maximum plant response) were obtained based on Lineweaver-Burk model. They were made measures of plant height, diameter of stem and volume at 80 days of plant age. The Kmax for height and diameter of the corn plant was low altered by availability of water, water + limestone and water + limestone + ammonium sulfate, but the Ks was great reduced by the limestone treatments. These treatments potentialized the effect of fertilizer on the plant growth, decreasing need of fertilization to reach Kmax. In the second experiment, it was made evaluation of corn response to fertilization with NPK 4-14-8 and covering with sulfate of ammonia in same amount at 34 days. They were made measures of height of the plant, diameter of the stem and volume at 34 and 70 days of age of the plant and corn production (weight of the ear corn) at 134 days. All the variables were highly correlated (above 0.90), showing that any one of the obtained measures in a premature way allows to obtain good estimate of the final production of grains. The kinetic constant Kmax was little altered by the availability of water, but the constant Ks was reduced drastically by irrigation. The located irrigation in small amount and at right time potentiates the effect of the fertilizer on the growth of the plant, reducing the fertilizer need. There is need of more researches on this theme, but the expectation is the decrease of the dependence of fertilizers and water in grain production.