Q: Beets, Swiss chard, and spinach languish here as if the soil were not fertile, even though I’ve added lots of organic fertilizers. What should I do? — Ann Dell, Oklahoma City, Okla.
A: Sluggish beets, chard, and spinach usually signal a shortage of nitrogen (N) in the soil. Organic fertilizers vary widely in their N levels, so no matter how many amendments you’re working in, you may still be stinting on nitrogen. Home compost typically contains one percent nitrogen or less. A good high-N (about five percent) organic fertilizer is alfalfa meal, on a par with the popular synthetic fertilizers labeled 5-10-5 (that’s 5 percent N, 10 percent phosphoric acid, and 5 percent potash). Soybean meal is a little richer, about seven percent N. Both soybean and alfalfa meal are widely available, easy to handle, and easy on the nose. Right before planting, lightly cover the ground with either meal, about 3 pounds per 100 square feet. Other dry organic fertilizers sold at many garden centers are blood meal, fish meal, and composted manure; check labels for exact nutrient proportions and application rates.
To find out whether vegetables are indeed nitrogen-deprived, feed the crop with a liquid fertilizer such as fish emulsion about four weeks after seedlings emerge. If they respond dramatically, you’ll know that they needed the extra N that these solutions provide. You can safely apply more liquid fertilizer every two weeks, following the directions on the container, but stop feeding two weeks before harvest. It’s also possible that large applications of organic mulches, leaf compost, or peat have made the soil too acidic for your crops. A pH value of 6.5 to 7 is best. To determine your soil’s pH, contact your county Cooperative Extension Service for soil-testing information. The soil-test report will advise you on how to correct your pH.