Uso do clorofilÃmetro e de agricultura de precisÃo no manejo da adubaÃÃo nitrogenada do milho / Chlorophyll meter and precision agriculture use in nitrogen sidedressing management for corn.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The complex dynamics of nitrogen (N) exerts influence on the management of nitrogen fertilization for corn crop. In this sense, tools which aim to detect the spatial and temporal variability of the factors linked to its availability, as well as, the timing between topdressings and the phenological stages of highest demand for the nutrient are essential strategies to refine its N management. The present study aimed to: 1) evaluate and validate the sensitivity of the chlorophyll meter in predicting the nutritional status of corn in response to N along its vegetative cycle, identifying and correcting the possible nutrient deficiencies, and, 2) correlate, in a spatialized perspective, the grain yield and variables indicating the N supply for corn, in response to the doses of the nutrient topdresse. To reach those objectives, experiments under controlled and field conditions have been developed. Nitrogen nutrition was monitored with the use of the chlorophyll meter. Along the crop cycle, the relative contents of chlorophyll, the weight of shoot dry matter, the N contents in leaf, in grain, organic matter and mineral-N in soil and grain yield were evaluated. The results showed that the chlorophyll meter is sensitive in detecting variations in corn nutrient status in response to different characteristics of soil and of the N supply, though, it overestimated the amount of N topdressing necessary to optimize corn yield. Lower correlation coefficient among SPAD reading, leaf N and yield were found when it was considered their spatial variability. Nevertheless, the joint interpretation of the maps of SPAD reading and yield allowed to identify sub-areas with smaller capacity of N supply by soil, subsidizing the delimitation of zones for the site-specific nitrogen management.

ASSUNTO(S)

nitrogÃnio nitrogen ciencia do solo zea mays (l.) zea mays (l.) variabilidade espacial spatial variability spad spad

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