单项选择题

The Grass Is Greener at Harvard There is an underground revolution spreading across Harvard University this fall. It’s occurring under the soil and involves fungi(真菌) ,bacteria, microbes(微生物) and roots, which are now fed with compost tea (混合肥料) rather than pesticides and synthetic nitrogen (合成氮).
The results have so surprised university administrators that what started as a one - acre pilot project in Harvard Yard has spread organic practices through 25 acres on the campus.
"Our goal is to be fully organic on the 80 acres that we maintain within the next two years. " said Wayne Carbone, Harvard’s manager of landscape services.
Harvard’s president, Drew Gilpin Faust, who last year started a university effort to reduce greenhouse gases by 30 percent by 2016, has adopted the organic program at Elmwood, the Dresident’s house on Brattle Street. Dr. Faust became interested by the effort last spring when she saw a display that the Harvard Yard Soils Restoration Project had set up outside her office.
As the project proceeded, "I saw the impact, I was really excited," Dr. Faust said. "I think it’s an integral part of the larger effort to advance sustainability at Harvard. "
The organically grown grass on campus is now green from the microbes that feed the soil, eliminating the use of synthetic nitmgen, the base of most commercial fertilizers. No herbicides(除草剂)or pesticides are used, either. Roots reach eight inches into soil that was once so compacted the trees planted in it were dying.
"At commencement(毕业典礼), rain or shine, we have 10,000 people here," Mr. Carbone said, gazing at the expanse where chairs are traditionally set in front of Memorial Church. "We get about 6,000 to 8,000 people here every day. "
But the microbial activity beneath their feet has now aerated(使生气勃勃) the soil. Tree roots can breathe because they are absorbing nutrients and water. Newly planted oaks outside Mass Hall, a few steps from Harvard Square, are thriving.
Soil tests show the Dresence not only of beneficial bacteria and fungi but also of the micro - organisms that feed on them, recycling nitrogen back into the soil. This dog- eat- dog(竞争激烈的) world underground also retains moisture.
Thanks to these efforts, the university has reduced the use of irrigation(灌溉) by 30 percent, according to Mr. Carbone, thus saving two million gallons of water a year.
And the 40 - year - old orchards at Elmwood, which have been treated with compost tea, are recovering from leaf spot(叶斑病) and apple scab(疮痂病).
The expanse in front of Memorial Church gets no more than 6,000 people every day.