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Effects of variable rate fertilization on orange groves during four seasons

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André Freitas Colaço
Total Authors: 1
Document type: Master's Dissertation
Press: Piracicaba.
Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
Defense date:
Examining board members:
Jose Paulo Molin; Gustavo Di Chiacchio Faulin
Advisor: Jose Paulo Molin

Citrus has an important role in the Brazilian agriculture, however it now faces economical and fitossanitary challenges that restricts its sustainability. So, new management strategies that provide higher efficiency and lower production cost has been searched. In this context, Precision Agriculture (PA) is considered as one of several alternatives to increase competitiveness in the production sector. PA relies on the management of crops based on their special variability therefore managing actions must be applied site specifically within a production field. In citrus, although this technology has been approached by research in the late 1990\'s, adoption is still low in Brazil. The main technique of the site-specific management is the variable rate application of inputs however the effects on citrus agronomical aspects are still unknown, especially during long periods of observation. Thus, the objective of this work was to evaluate the effects of the variable rate application of fertilizers and lime on input consumption, yield, soil fertility, plant nutrition and on fruit and juice quality on citrus. Two citrus groves were used to allocate the variable rate (VR) and fixed rate (FR) treatment. They were placed in intercalated pairs of tree rows along the two fields. On the VR treatment applications of nitrogen, phosphorus, potassium and lime were carried according to prescription maps, which were based on soil and leaf georeferenced sampling and on yield mapping. In the FR treatment application followed the conventional prescription method, based on a single soil and leaf sample and on yield estimation. Treatments were conducted during four years, from 2008 to 2011. Significant reduction on input consumption was observed, mainly for nitrogen (37 and 51% less on each area) and potassium fertilizers (41 and 18% less on each area). In one of the two fields better fertility levels were found on the VR treatment, once it reduced regions with excess of nutrients and enlarged areas of adequate levels of potassium and bases saturation. Yield gains up to 13.1% occurred on this field. In the second field loss on soil fertility and yield was found on the sitespecific management in two of the four years evaluated. Better juice quality occurred on the variable treatment regarding acidity and soluble solids and acidity ratio. Leaf nutrition was not affected by the treatments. PA allowed optimization and higher fertilizer use efficiency. This study also showed the potential of this technology to increase yield and improve soil fertility management. (AU)

FAPESP's process: 11/05303-6 - The effect of variable rate fertilization on yield of orange trees over four seasons of evaluation
Grantee:André Freitas Colaço
Support Opportunities: Scholarships in Brazil - Master