Login
Toggle navigation
Home
ICPA
Conference
Abstract Management
Abstract Topic Groups
Author Instructions
Registration
Registration Information
16th ICPA - Conference Registration
Registrants Map
Hotel and Travel Information
Tour
Workshops
Sponsors
Become A Sponsor
16th ICPA Sponsors
Conference Program
General Outline
Oral Program
Awards
Proceedings
Leadership
ISPA Leadership
Officers
Past Presidents
Officer Responsibilities
Country Representatives
Election Candidates
Communities
Community Guidance
On-Farm Experimentation
Nitrogen
Latin America
Economics
African Association for Precision Agriculture
Membership
ISPA Member Benefits
Membership Form
Events
ISPA Events
ACPA
ACPA Proceedings
AfCPA
AfCPA Proceedings
CLAP
CLAP Proceedings
ECPA
ECPA Proceedings
ICPA
ISPA Webinars
OFE
AAPA
Latin American
Robotics and Automation Symposium
Event Overview
Registration
Program
Venue
Speakers
About ISPA
Newsletters
History
Jobs
Precision Ag Definition
Agriculture Course Database Submission
Publications
ICPA Proceedings
ECPA Proceedings
Contact Us
Members
Suggestion Form
Conference
Abstract Management
Abstract Topic Groups
Author Instructions
Registration
Registration Information
16th ICPA - Conference Registration
Registrants Map
Hotel and Travel Information
Tour
Workshops
Sponsors
Become A Sponsor
16th ICPA Sponsors
Conference Program
General Outline
Oral Program
Awards
Proceedings
Proceedings
Search
Authors
Topics
Years
Types
Find matching any:
Reset
» Add more years
Add filter to result:
A Five Year Study Of Variable Rate Fertilization In Citrus
J. P. Molin, A. F. Colaço
University of São Paulo
Citrus is a major crops in Brazil, especially in the São Paulo state, which is the main citrus production region in the world. Yet, site specific technology is still in early stages of adoption. Variable rate application of inputs is the most important tool in a Precision Agriculture system, however its effect on citrus agronomical aspects are still unknown, especially during long periods of observation. Thus, variable rate fertilizer application has been tested in citrus orchards in Brazil in a long term study. The goal is to evaluate the effects of this technology on input consumption, soil fertility, plant nutrition and on fruit yield. Two 25.7 ha commercial orange fields (field 1, 32% clay and field 2, 14% clay) were divided into variable and fixed rate fertilizer strip treatments. Data of soil electrical conductivity, elevation and soil texture were used to assess the variability of these fields. Variable rate prescriptions (lime, N, P and K) were based on soil and leaf grid sampling and yield data. Fixed rate applications followed standard prescriptions based on soil sampling and yield expectation. Results from the first two years (2008 and 2009) were presented at the last ICPA, in 2012 (Colaço and Molin, 2012). Data from three more years were gathered and analyzed, accomplishing so far five out of six year data planned for this study. Results presented here are from five yield data (2008 until 2012) and four variable rate fertilizations (2008 until 2011). Field 1 showed more variability than field 2 regarding soil texture, EC and elevation. Site specific applications provided significant reduction on input consumption, mainly for nitrogen (37 and 51% less on field 1 and 2, respectively) and potassium fertilizers (41 and 18% less on field 1 and 2, respectively). In field 1, better fertility levels were found on the variable rate treatment. Along the years of evaluation, it reduced regions with excess of nutrients and enlarged areas of adequate levels of potassium and base 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 site-specific management in two out of the four years of variable rate applications. This field presented lower natural nutrient fertility and the variable rate prescriptions used were considered not suited for this soil condition. Fertilizer use efficiency (fruit yield divided by fertilizer input) was higher in the variable rate treatment in both fields. Leaf nutrition was not affected by the treatments. Overall results were better for the field with higher variability. Site specific management allowed optimization and higher fertilizer use efficiency. This study showed the potential of this technology to increase yield and improve soil fertility management.
Keyword
: variable rate fertilization; long term study; brazil
J. P. Molin
A. F. Colaço
Precision Fertilization of Horticultural Crops
Oral
2014
Download paper