Field trials are very important in maize research. In particular, breeders conduct different types of fi eld trials
in the process of developing new varieties. Each type of trial has its peculiarities. Apart from those conducted
by the individual breeders in their research programs, there are collaborative trials conducted nationally or
internationally. Annually, national collaborative trials are constituted from candidate varieties submitted by
participating researchers in a country. Similarly, IITA coordinates international trials from candidate varieties
developed by IITA’s scientists and their national counterparts in the countries of WCA. Data obtained from
fi eld trials are intended for use in arriving at decisions on the varieties to release, the agronomic practices to
recommend, and the disease, insect, or weed control measures to adopt. Therefore, a certain measure
of uniformity of execution that would minimize spurious results is expected in national and regional
The experience of maize researchers accumulated over several decades in the subregion has clearly indicated
the need for training researchers and technicians in the conduct and management of maize fi eld trials. The data
recovery rate from national and particularly from international (regional) trials has never been 100% in WCA.
Very often, data returned to trial coordinators are not analyzable and are, therefore, not usable. Sometimes, the
coeffi cients of variation (CV) associated with measured traits are too large, thus rendering such data unusable.
Researchers defi ne certain traits differently. An example is plant height. Some researchers defi ne it as the
distance from the soil surface to the node bearing the fl ag leaf (topmost leaf); some others defi ne it as the
distance from the soil surface to the height of the central tassel branch.
The purpose of this book is to correct these anomalies as far as possible. The materials were carefully thought
out and are presented in a logical sequence by the authors. The contents have been used in several training
courses and refi ned over time. Starting with the purpose and types of maize variety trials, the authors follow
with an exhaustive description of designing, laying out, and conducting maize variety trials. Sources of spurious
data in maize research include the timing and rate of application of agronomic practices, data collection,
harvesting, and preparation of data for analysis. The authors focus attention on these areas in four different
sections. Examples, illustrations, practice problems, materials needed for fi eld work, and revision questions
are given in the annexes. Students, technicians, as well as research scientists will fi nd this book an invaluable
companion in the execution of their research work.