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New Mexico State University

Issue: January 23, 2010

Too much manure can reduce garden's yield.

Q. I need some help. I worked an 8x16 foot patch of ground last summer that had never been worked. I added 7 bags of manure, 10 wheelbarrows of mulch, some bone meal, and the compost pile went into it.

I planted tomatoes, cucumbers, beets, carrots, strawberries and raspberries. All the plants looked beautiful. The beets, carrots and raspberries produced. However, there were no tomatoes, no cucumbers, or strawberries. What is my garden lacking?

A. Your garden may not be lacking anything; it may have too much nitrogen. The quantity of manure suggests that you added a lot of nitrogen to your garden. If the mulch and compost pile contained manure it is very likely that there is too much nitrogen. However, even if the 7 bags of manure were all that was added to that rather small garden area, it could explain the problem.

A common garden complaint is that tomatoes, cucumbers, and other plants grew very well, but produced no fruit. You said your plants were beautiful. When you get excellent growth and little flowering and fruit production, surplus nitrogen is often the cause. Nitrogen stimulates vegetative growth at the expense of flowering and fruit production. The bone meal would have added the phosphorus needed for flowering and fruiting, but in our calcareous soils, bone meal is slow to release the phosphorus.

I asked Dr. Ron Walser, NMSU Extension Urban Small Farm Specialist, who began to anticipate the nitrogen problem even before I described your plants to him. He stated that your garden should be in great shape for this year and recommends that you do not add any more manure or nitrogen source. He said the raspberries may have produced because they require fairly large quantities of nitrogen, but still suggests that you should not add any more this year even for the raspberry plants. The strawberries may not have produced fruit for several reasons. He suggests that they are either spring bearers or that they were planted too late to produce last year if they are "ever-bearing" strawberries. He said you should see flowers this spring and recommends that you prepare to cover the plants when flowering to prevent frost damage. If the plants are everbearing varieties, he thinks that they should produce both a spring and fall crop this year.

If you add no more nitrogen to your garden this year, tomatoes and cucumbers should also produce well along with the other plants.

For more gardening information, visit the NMSU Extension publications World Wide Web site at

Send your gardening questions to:

Yard and Garden, ATTN: Dr. Curtis Smith
NMSU Cooperative Extension Service
9301 Indian School Road, NE, Suite 112
Albuquerque, NM 87112

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.