Maize is one of the most demanding grasses in terms of nitrogen fertilization. There is a need to estimate accurately the amount of N applied to the soil so that this crop can be properly supplied during its whole cycle. The soil organic matter content, grain yield expectation and N contribution from the decay of the preceding crop are the parameters currently used in the States of Rio Grande do Sul and Santa Catarina, Brazil, to define maize nitrogen rates. Nitrogen has a complex dynamics in the soil. Furthermore, the crop’s ontogeny interferes substantially with N demand. Considering such variations, other parameters can help to improve the management of N side-dress fertilization in maize. Several plant parameters have been used to indicate N level in the tissue. Among them, the nitrate content in the stem, the nitrogen content and accumulation in the leaf or plant and the relative chlorophyll content in the leaf deserve special consideration. The estimation of leaf chlorophyll content through a portable chlorophyll meter have been intensively studied in the last years because it is fast, cheap and efficient. This review has the purpose of describing the major plant parameters that can be used as indicators of the plant nitrogen level in order to foresee the need of N side-dress application in maize, aiming to enhance the N use efficiency and to decrease the environmental impact of N application.
Zea mays; nitrogen; efficiency of use; grain yield
