Optical sensor to support the nitrogen recommendation on the sugarcane crop

Author(s)

Lucas Rios do Amaral

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2011-01-21

Examining board members

Jose Paulo Molin; Heitor Cantarella; Ricardo Yassushi Inamasu

• Advisor: Jose Paulo Molin

Abstract

Globally there is a great demand for alternative sources of energy, propitiating an intense expansion to the Brazilian sugarcane sector that becomes avid for more technologies to maximize the sugarcane production and increase the economical return. In this context, it is extremely important the proper management of nitrogen applied to sugarcane crop. The use of precision agriculture techniques, especially using sensors that make possible the nitrogen fertilization in variable rate and real time, is receiving great attention from researchers around the world. The present research had as main objective verify the potential of a terrestrial active optical sensor (Crop Circle, Holland Scientific) to support the nitrogen recommendation in variable rate application on the sugarcane crop, in agreement with the need for each area. To reach this goal, two experimental areas were conducted counting in each area with a plots experiment and a strips experiment. The plots aimed to evaluate the crop response to nitrogen, measured by different methods. The strips had the function to test different strategies of nitrogen fertilizer recommendation on variable rate based on the use of the terrestrial optical sensor. The crop did not respond significantly to the applied nitrogen in terms of productivity, while the leaf analyses to evaluate the plants nutritional status proved to be inconclusive. It was observed lower correlation between leaf nitrogen content and the amount of chlorophyll measured by a portable chlorophyll meter, being these two methods insufficient to evaluate the efficiency of the optical sensor on estimating the nitrogen nutrition of the sugarcane, as the vegetation indices measured by this equipment had values increasing according to the amount of nitrogen applied. The methodology of nitrogen fertilization recommendation, starting from curves of input/response obtained in the plots proved to be problematic, because it recommends nitrogen over application and does not take into account the crop response to this nutrient. The other strategy, based on estimated crop response in a strip that has received the appropriate nitrogen rate, resulted in smaller nitrogen amounts, being more consistent with the low response of sugarcane found in the experimental plots. The optical sensor is a useful tool to recommend nitrogen to the sugarcane crop, taking into account its spatial variability. Further studies are necessary to assess the best strategy and best vegetation index to be used for the recommendation, and possible factors that may interfere in the obtained results. (AU)

• FAPESP's process: 09/03372-0 - Sugar cane nitrogen fertilization management using ground active optical sensor
• Grantee: Lucas Rios do Amaral
• Support Opportunities: Scholarships in Brazil - Master