官方APP下载:英语学习播客(支持苹果手机、安卓手机)
创办于2003年
UNSV记不住?那就记中文谐音“忧安思危”吧!
  Slow and Steady Wins the Race!
UNSV英语学习频道 - Slow and steady wins the race!
公众微信服务号(英语全能特训)
英语全能特训(微信公众服务号)
UNSV英语学习频道淘宝网店
客服短信:18913948480
客服邮箱:web@unsv.com
初级VIP会员
全站英语学习资料下载。
¥98元/12个月

AGRICULTURE REPORT - Why Holding Fruit on Trees May Limit Next Year's Crop

作者:Jerilyn Watson 发布日期:11-10-2009

This is the VOA Special English Agriculture Report.

Alternate bearing is a widespread problem for growers of citrus and other fruit trees. It can affect a large area or just individual trees or even part of a tree. No, it is not a disease. Alternate bearing is when a tree produces a heavy crop one year, called an "on-crop," followed by an "off-crop" the next year.

On-crop trees produce a large number of small fruit with little value. Off-crop trees produce no fruit or a small number of large fruit that often have thick, unappealing skins.

Mandarin trees heavy with fruit in an on-crop year
Mandarin trees heavy with fruit in an on-crop year

Citrus growers know that the number of fruit in their current crop has an inverse effect on the number of flowers in the return bloom. In other words, if one number is big, the other number will be small.

Two researchers recently did a study to understand how this happens. Johannes Verreynne is now at Stellenbosch University in South Africa. Carol Lovatt is at the University of California, Riverside. They studied "Pixie" mandarin trees in the Ojai Valley of California. Mandarin oranges are also known as tangerines.

The study showed that fruit on the tree reduces the next bloom by stopping buds from appearing. This limits the number and length of summer and fall shoots. As a result, there is a reduction in the number of nodes, or joints, that produce groups of flowers along stems. Fruit on the tree during spring bloom stops the growth of flowering shoots.

During an on-crop year, growers often treat the fruit so it can stay on the tree longer. The purpose is to extend the harvest season. Yet Carol Lovatt says holding fruit on the tree makes alternate bearing worse. The researchers advise growers to investigate the effects of thinning or pruning to reduce the number of fruit in early summer of the on-crop year.

The findings appeared in the Journal of the American Society for Horticultural Science.

Other kinds of trees that can experience alternate bearing include nut trees. Scientists recently studied the effects of mechanical thinning on two kinds of pecan trees in the southeastern United States. The results from the University of Georgia appeared in HortTechnology, also published by the society.

The study compared trees that had been thinned by machine with those that had not been thinned. The findings suggest that thinning during the on-crop year can increase the value of off-year pecan crops.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. I'm Bob Doughty.

版权所有©2003-2019 南京通享科技有限公司,保留所有权利。未经书面许可,严禁转载本站内容,违者追究法律责任。 互联网经营ICP证:苏B2-20120186
网站备案:苏公网安备 32010202011039号苏ICP备05000269号-1中国工业和信息化部网站备案查询
广播台