AgroBriefs© are short articles of 4-14 pages on an agricultural topic, a frequently asked question, or a subject that is not covered by our other publications. Agrobriefs are published as PDF files. Upon request they can be printed and mailed to Agromisa readers who do not have access to a good Internet connection. © Copyright of the AgroBrief remains with Agromisa Foundation. You may copy and distribute unaltered copies of this publication, in any medium, provided that you conspicuously and appropriately display an accurate copyright notice on each copy.