WSU Extension Q&A: Soil, drought can affect nitrate levels in alfalfa

Q. What causes high nitrates in alfalfa?

A. Normally alfalfa is considered at a low risk for nitrates especially compared to annual grasses. However, under the right circumstances even alfalfa can have high nitrates. They include high or excessive soil nitrogen or nutritional deficiencies that restrict plant growth and can be any nutrient other than nitrogen. High nitrates can also be caused by drought or lack of irrigation water or any other factor that restricts growth. So how do you know when hay has too much nitrate? The only way is to have the hay tested for nitrates (NO3). The level is considered safe in most circumstances when it is below 564 NO3-N or 2,500 NO3. You must look at the report to know and see how your laboratory reports nitrate to know which ppm range is appropriate. For more information you can find a fact sheet I wrote at: http://extension.wsu.edu/benton-franklin/agriculture/forages/ and look for the guide sheet titled “Nitrate Poisoning in Ruminants.”

Q. Is it important to prime seed for the vegetable garden?

A. Priming starts the germination process by soaking for a predetermined amount of time in a solution, most typically water. This is done to increase uniformity of germination and emergence from the soil, and thus enhance vegetable stand establishment. Many gardeners promote soaking hard-shelled seeds such as beans, peas and cucurbits before planting to promote more rapid uniform emergence. In practice, this helps plants emerge rapidly and avoid some problems with soil borne fungus. Perhaps a better approach is to plant seeds at uniform depth (six times the width of the seed), in soil that is warm enough for rapid germination and is not excessively wet to achieve the same beneficial results. Pay attention to the required minimum temperature for germination of the specific type of seed prior to planting and ensure that the soil temperature reaches that minimum threshold before planting.

Q. I heard you should only use food-grade plastic when storing or preparing food. How do I know which plastic is food grade?

A. Unfortunately there is no symbol that tells you when a plastic is food grade. Your best bet is to use a plastic container designed for use with food. This means the product is intended to be used with food, either at the home or commercial level. This contrasts with plastic buckets, garbage cans, laundry detergent buckets, pet food, or pet litter containers. These plastics were not designed to hold human food and should not be used in that capacity.

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This story was originally published March 2, 2018 at 5:43 PM with the headline "WSU Extension Q&A: Soil, drought can affect nitrate levels in alfalfa."