By: Talia Plaskett, Protected Crop Specialist
As summer production of tunnel vegetables slows down, it is time for winter greens to move on into the greenhouse! Spinach, along with a variety of other cool season greens, can be grown in high tunnels throughout the offseason. This allows you to maximize your use of the otherwise empty greenhouse space without cutting into the production of your summer crops. A recent study done by the Northern New York Agriculture Development Program (NNYADP) examined the effect of nitrogen(N) fertilizer rates on winter-grown, high tunnel spinach production.
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| A study out of New York examined the effect of nitrogen rates on winter-spinach - photo credit Johnny's Seeds |
In the winter of 2018-2019, they examined the effect of different pre-planting N applications on overall spinach yields. The same N source was used across the four treatments, allowing them to make direct comparisons to yield based on input. Rates of 0 lbs/ac, 65 lbs/ac, 130 lbs/ac or 200 lbs/ac were applied to their treatment plots about 1 week prior to transplanting the spinach. Plants were seeded in two batches, one on August 27 (early planting) and one September 10 (late planting). These were transplanted into the tunnel on September 21 and October 9, respectively. Yield measurements were based on harvesting the plants at the baby-medium leaf stage at 4 dates.
When looking at the total yield for each treatment, there was no significant difference between those plots that received 0 lbs/ac and those treated with 200 lbs/ac. Planting date did make a difference to the spinach harvested in the fall and in the winter, where the early planting produced more compared to that of the later planting. Over the course of the season, however, the later planting caught up to the earlier one, to produce similar yields by the April harvest date. The importance of the planting date may depend on when your summer crop is pulled in the fall, and when the subsequent summer crops are started in the spring. If you plan to have your summer transplants started by late winter (February/March), a later planting of winter greens may not have the time to catch up to the production of the earlier planting.
