Monday, January 25, 2021

What the 2020 garden told me


The garden on June 20, 2020

In this post from last year, I discussed why I asked the 2020 garden what the effect would be of replacing my previous source of garden nitrogen, cottonseed meal, with urine. I also described a psychological issue associated with safely using urine and referenced this 2019 post for information on potential environmental and health hazards, and I described how I would collect and apply the urine. Now it’s time to let you know how the garden answered my question.


When I wrote the post last February, COVID-19 was in the US but not yet widespread. By the time the growing season began, Mike and I, along with most people in the US, were under some form of lock-down. COVID-19 can be carried in both urine and feces. If I knew I had COVID-19, I would not used my urine on the garden, just as I would not have used it if I had any of the other diseases whose infectious agents can be spread through urine. As it happened, I have not experienced symptoms of COVID-19, nor has anyone told me they exposed me to it, so I felt it was safe to fertilize with urine throughout the growing season. As the 2019 post notes, there is as close to no chance as I can imagine that any urine would find its way outside of our property to be a health hazard to anyone.


I decided to apply urine to all of the vegetable and grain beds to replace all of the cottonseed meal I would have otherwise used. Thus I did not have any control beds in which I used cottonseed meal rather than urine. In order to have space for control beds I would have needed to expand the garden into areas covered with grass and weeds and unprotected from rabbits. This would have introduced variability in newly gardened versus previously gardened soil, variability in rabbit pressure, and a reduction in the time I spent on each garden bed compared to what I have done in past years, which would have made it harder to compare this year’s yields to those of previous years. Instead, I compared the yields I obtained in 2020 to the best yield I obtained for each of the varieties over the past six years, after I had settled on Steve Solomon’s re-mineralization practice and the spacing for all the crops that I grow. The only exception was for soybeans, because the last time I grew them before 2020 was in 2011. Hence I compared the soybean yield with a different variety grown in 2011 using the same spacing between stations but more seeds per station.


When I began collecting urine I used the same system as I had used in 2019: I urinated into a urinal and then transferred the contents of the urinal to a 2 gallon bucket. The next morning I emptied the collected urine from the bucket into a sprinkling can, added water to fill the sprinkling can, and applied the diluted urine directly to the bed, on top of the plants in it. However, I soon grew weary of leakage around the edges of the urinal. For those of you with flexible appendages to deliver urine, many possible ways to collect urine without making a mess suggest themselves. For those of us who, like me, lack such appendages, avoiding messes when using a urinal is more difficult. Fortunately we have a camp toilet, inherited from my father-in-law.


 The camp toilet, with the lid open to show its resemblance to a water-flush toilet. A sliding valve at the bottom allows the urine to drain by gravity into the bottom container and that container to be sealed off between uses. I collected and composted the toilet paper I used.

Side view of the camp toilet. The top chamber unbuckles from the bottom chamber so that the urine collected in the bottom container can be emptied into a sprinkling can.


Using the camp toilet to collect the urine removed the mess factor from the collection experience. Each morning I poured the urine collected the previous day into the sprinkling can, diluted the urine with water to fill the can, and then sprinkled the urine onto the bed and the plants it contained, following it with a sprinkling can of water to wash the diluted urine off the plants and onto the soil. As in 2019, I collected urine only when urinating was all I was doing, and I only collected it during the day because the camp toilet was located in our basement and I had no desire to descend the steps into the basement when I had to urinate overnight. Thus I collected perhaps two-thirds to three-quarters of the total urine I produced in a 24 hour period, but I calculated how much urine to add to each bed as if I had collected all of the urine I produced in a day.


To calculate how much urine to apply to each bed, I proceeded similarly to the calculation for the 2019 corn bed experiment. The daily urine production of the averages adult contains about 0.024 pounds of nitrogen. My growing season is about 180 to 200 days long. Using 180 days for my growing season, if I collect urine every day and apply all of it over the course of the growing season:

180 days * 0.024 pounds of nitrogen per day = 4.3 pounds of nitrogen


According to Solomon, cottonseed meal is 6% nitrogen, and he recommends applying 6 pounds of nitrogen to a 100 square foot bed (twice that for potatoes). Thus the amount of nitrogen applied via cottonseed meal is:


6 pounds * 0.06 = 0.36 pounds of added nitrogen to a 100 square foot bed

12 pounds * 0.06 = 0.72 pounds of added nitrogen to a 100 square foot bed of potatoes


Dividing the 4.3 pounds of nitrogen from all the urine I produce in a 180 day growing season by 0.36 pounds of nitrogen needed per bed, that amount of urine will supply all the needed nitrogen for twelve 100 square foot beds.


I grow a total of nine beds of vegetables and grains, two beds of small fruits, and one bed of herbs and flowers in the garden. The latter three beds are not re-mineralized. Since the potato bed needs twice as much nitrogen as the other beds, then I needed to apply urine to the equivalent of 10 beds. I had 12 beds’ worth of urine to apply during the 180 day growing season. Thus I began collecting urine on April 1 and applied the collected urine to bed 1 the next day. That day’s collected urine was applied to bed 2 the following day, with this rotation continuing through bed 6. For bed 10, which held the potatoes, I collected and applied urine two days in a row, then treated beds 11 and 12 as I had treated beds 1 through 6. After applying urine to bed 12, the next day’s urine was collected and applied to the subtropical trees and shrubs I keep in containers. Then I began again with collecting and applying urine to bed 1 and so forth. When the soil was saturated, I did not apply urine, waiting until the soil drained to resume the application sequence. Later in the season I altered the collection and application sequence, as discussed below.


Wood ashes are a potential source to replace all of the calcium and some to all of the potassium required for re-mineralizing garden soil. In 2020 I did not have enough wood ashes on hand to remedy the full deficiency of potassium, and I had an excess of calcium. However, the soil test indicated that magnesium was deficient. Wood ashes contain about 3% magnesium. Therefore I added enough wood ashes to the re-mineralization mix to supply 10% of the magnesium deficiency, as Solomon suggests in the Acid Soil Worksheet. This avoids the risk of having too much magnesium relative to calcium in the garden soil. I made up the remaining potassium deficiency and the deficiencies in the other minerals in the usual way.


Most years the weather has a strong effect on the conversation between the garden and me. But unlike some other aspects of 2020, the weather gave me a break. The last spring frost was on April 18; the first fall frost occurred on October 16, for a growing season of 181 days. April and May were cooler and wetter than normal. June was warmer and drier than normal, while July temperatures were close to normal but accompanied by excessive rainfall. August was cooler and wetter than normal while September was about average in temperature but drier than normal. October was near normal in both temperature and rainfall, while November was warmer than normal with about normal rainfall. Since there was nothing particularly unusual about 2020’s weather (which is the only unusual thing about it), I do not need to take weather into account when discussing what the 2020 garden taught me.


The yields for all the vegetable and grain crops I grew in 2020 are shown in the following figures.




A first glance reveals that the 2020 yields varied compared to the best previous years. To better understand the variability, I considered together the crops grown at different times during the growing season. These fall into the following groups.


Group 1: planted in autumn 2019 for harvest in late spring 2020. This group includes garlic and potato onions.


Group 2: planted in April 2020 for harvest later in spring or in summer. This includes bok choy, cabbage, endive, spring lettuce, and potatoes.


Group 3: planted in April 2020 for harvest in summer and autumn. This includes beets, carrots, and leeks.


Group 4: planted in May and June 2020 for harvest in summer and autumn. This includes pole snap beans, dent corn, cowpeas, cucumbers, eggplant, muskmelon, sweet peppers, soybeans, various squashes, and tomatoes.


Group 5: planted in August 2020 for autumn harvest. This includes arugula, bok choy, Chinese broccoli, Chinese cabbage, kale, fall lettuces, mustard greens, daikon and winter radishes, and turnips.


Within Group 1, yields were around 15% to 25% below the best previous value.


Within Group 2, I ignored endive since it was first grown in 2020. Cabbage and bok choy yields were much below the best previous, by a factor of 3 or more, and the romaine lettuce yield was lower by a factor of about 8. The loose-leaf lettuce yield was about 25% lower than the best previous yield, while the potato yield was about 40% lower than the best previous.


Within Group 3, yields were about 40% less than the best previous for the beets and about 25% lower than the best previous for leeks. For the carrots, compared to the same variety the 2020 yield was about 15% lower, but it was much lower than for the other variety shown.


Within Group 4, the 2020 yield of dent corn was about half of the best previous, and the 2020 yield of cowpeas was about 75% lower than the best yield (but of a different variety). On the other hand, the pole snap bean yielded better in 2020 than in 2019, though not as well as a different variety. The soybean yielded about half as much as a different variety planted with more seeds per station in 2011.


The 2020 cucumber yield was higher than the best previous for both the May and June plantings. The 2020 muskmelon and winter squash yields were much lower than the best previous. One of the zucchini varieties yielded poorly but the other one yielded about two-thirds of the best previous (of a different variety). The ‘Desi’ summer squash yielded as well as the better of the two zucchini varieties grown in 2020.


The three sweet pepper varieties yielded 10-25% lower in 2020 compared to the best years, while two of the four tomato varieties matched their best yields from previous years and the eggplant variety yielded better than a different variety.


Within Group 5, the bok choy variety doubled its best previous yield, and a different variety of Chinese cabbage yielded almost a factor of 4 more than in previous years. The kale variety also outperformed the previous best yield of a different variety; the same held true for the two mustard varieties grown in 2020. On the other hand, the 2020 yields of arugula, daikon and winter radishes, and turnips were all below the best previous yields.


What can we learn from this data? The first thing to notice is that overall yields were comparable to, though somewhat lower than, the best previous year. The total weight of the crops harvested in 2020 was 560 pounds, bested only by 2015’s total of 687 pounds and considerably exceeding 2016 and 2018 (about 390 pounds each).


Within the groups, only in Groups 4 and 5 did some, but not all, of the crops grown match or exceed the best previous yields. All other crops yielded below the best previous, some by a large factor.


By June of 2020, as I observed the slow growth of the cabbages compared to previous years, I began to suspect that rotating applications of urine across the entire garden meant that I had not applied sufficient nitrogen to shorter-maturity crops like the spring greens. I also wondered if applying urine before I planted a crop meant that the urine I applied before planting did not contribute to growth of the crop. The following figure gives the bed number, the crop(s) planted in that bed, when the crop(s) were planted, the days on which urine was applied to that bed, the total amount of nitrogen contained in the applied urine, and how much of the nitrogen was applied while the crop was present in that bed. 




With the results from the figure in hand, let us look at our five groups of crops again. My hypothesis is that for crops which received 0.36 pounds or more of N from urine while they were in the ground (0.72 pounds for potatoes), the yield would be about the same as for previous years. Crops which received significantly less than this while they were in the ground would yield lower than in previous years.


Group 1 (bed 4): when I planted the potato onions and garlic in early November of 2019, I added a quarter of the usual amount of cottonseed meal, which contained about 0.09 pounds of nitrogen. This was to give them a good start, as they begin to grow after planting and pick up growing again in early spring, before I began applying the urine. Thus the total nitrogen applied was 0.23 pounds, about 63% of the amount that I intended to apply. As hypothesized, observed yield is lower than the best previous yield.


Group 2 (beds 10 and 11): the potatoes and the spring greens received significantly less nitrogen than intended (the spring greens received only about half as much nitrogen), and the yields were less than the best previous yields, as hypothesized.


Group 3 (bed 11): while these beds received more nitrogen in urine than from cottonseed meal, they yielded less well than the best previous. There were other gardening issues with these crops that I believe contributed to the lower yields. I did not keep up with removing weeds in this bed after I harvested the spring greens; thus I suspect that the weeds used some of the nitrogen and minerals that I had meant for the crops. The weeds also shaded the crops to an extent, reducing their productivity. I did not thin the carrots or the beets, which caused overcrowding, another factor that may have contributed to reduced yields. Finally, many of the carrots in the carrot patch rotted over the summer, reducing the carrot yield.


Group 4 (beds 1-3, the summer planting of bed 4, beds 5 and 6, and bed 12): I will take a closer look at the various beds and their crops below.


Beds 1, 2, and 3 all grew corn and pumpkins. All were planted on the same date; all received some of the urine before planting. As hypothesized, because the amount of nitrogen applied after planting was about 52% of the amount I calculated would be required, the yield was lower than that obtained the previous year. I also note that some of the stalks lodged (fell over) in July after applying urine, and more lodged during a windstorm. Ears of corn that lay on or near the ground were predated on, presumably by small mammals. I suspect this accounted for some of the yield loss, but I believe that the lower than intended amount of urine accounted for a large part of the yield loss. This is bolstered by the 2019 results, when all of the intended nitrogen was applied to the corn bed to which I applied urine, and which yielded as much as the two beds to which cottonseed meal was applied for nitrogen.


The summer planting of bed 4 did not receive as much nitrogen from urine as intended. It was, however, sufficient to grow a much higher yield of cucumbers than I obtained from the same variety planted at about the same time in 2019, as well as about half the yield of soybeans compared to a variety planted more densely (same spacing but more seeds per station) in 2011. Possibly using the intended amount of urine would result in higher yields for both of these crops. The zucchini variety planted at this time yielded poorly, and did not perform well in the main crop planting in 2019. I will not grow this variety again, as it seems poorly suited to my conditions.


Beds 5 and 6 both received some urine before planting, but the total amount received after planting was about 80% of that intended. Compared to the same varieties grown in previous years, the cucumbers yielded more, two of the tomatoes yielded about the same, the peppers yielded somewhat less, and the melons and squash yielded much less. This suggests that factors other than the amount of nitrogen applied affected some of these crops. However, because some of them yielded as well or better than previously, this suggests that urine can supply all the nitrogen these crops need when enough of it is applied.


Bed 12 contained legumes: lima beans, cowpeas, and pole green beans. Only the last was the same variety as grown previously. While it yielded more in 2020 than in 2019, other factors need to be considered. In July 2019 a rabbit fed on some of the plants as they began to vine, setting them behind in growth. Also, I had not added any re-mineralization mix to the legume bed in 2019, because legumes can supply their own nitrogen through rhizobacteria in root nodules, and to conserve on the re-mineralization mix. I did not remember this until late July of 2020, after which I ceased applying urine; the 2020 legume bed received the same re-mineralization mix as the other beds. I cannot untangle the effect of the urine from the other factors discussed.


Group 5 (bed 10, planted 8/23/20): this bed received more than the amount of nitrogen I had intended to give it. This was in part due to a lessening need for urine on other beds as I finished harvesting from them, and in part because I made sure to apply at least as much as I had calculated it needed. Notice that all of the leaf crops except for arugula out-performed the previous best yield, but none of the root crops did so. One possible explanation is that I did a better job of thinning the leaf crops than the root crops. Because I left too many roots in each row for too long, they competed with each other, so that I harvested too many small roots rather than the larger roots that are easier to use in the kitchen. Another possibility is that the ratio of nitrogen to phosphorus and potassium became too large; the latter two are needed for good root growth, so that the turnips and radishes may have grown their leaves at the expense of their roots.


Overall, considering that I did not apply enough urine to fully meet the needs of most of the crops, the 2020 yields are high enough to justify continuing to use urine in place of cottonseed meal for most of the crops that I grow. I will need to adjust the application schedule to ensure that I apply enough urine to each crop I use it on to replace all of the nitrogen that had been met by applying cottonseed meal in past years. The details of that schedule are yet to be worked out; when it is available, I will post it here, as well as anything else I want to share about what I’ll ask the garden in 2021. Till then, enjoy life!



  1. Hi Claire,

    Kudos to you for the methodical application of the urine to the garden beds. And the camp toilet is a seriously neat idea.

    My urine is ending up in the garden beds adjacent to the orchard and I'm applying it there as a possible snake deterrent. I'd heard old tales about the use of ammonia, and noted they were ineffective and wondered whether the source of those old tales was the application of urine. But it is an experiment at this stage.

    Thanks to your recommendation I'm reading Steve Solomon's book on Growing Vegetables South of Australia which discusses his adventures in Tasmania. Given the elevation here above sea level it is candidly not a dissimilar climate despite being on the mainland continent. He has a really lovely way with words and like your writing, provides clear explanations backed by evidence.

    Good to read that your growing season weather was acceptable for your plants.

    I'm impressed at the output of your garden. But yes, weather, spacing, weeds, minerals and water - not to mention plant breeding play an extraordinary role in what ends up on our plates.

    The depth of knowledge and skills required to garden well is quite astounding, and always the soil minerals disappear from the patch.

    Top stuff and I'm in awe of the data you collected.



    1. Hi Chris,

      I hope that the urine helps deter your snakes! The few poisonous snakes we have are far less so than yours, and they prefer different habitats than mine. There are plenty of snakes in the yard, but they are nonpoisonous and help to keep other creatures in check. I always say hello and thanks to them when I encounter them. I would not react that way to your snakes.


  2. Claire, for the urine-collection process, you might consider using a simple device like the P-Mate:

    I use them on long hikes - a godsend. You might even make some yourself out of repurposed cardboard (such as cereal boxes) and then compost them afterward.

  3. I wonder how consistent the nitrogen content of urine is. I suppose that it depends on how much protein one consumes, which probably varies a great deal. Maybe there's some simple chemical assay that could be run to quantify it.
    I know what you mean about excess nitrogen and carrots, by the way. In 2020, I had fabulous tops, but useless roots, probably because of the urine-soaked stable bedding that I put in.

    1. A doctor friend of mine tells me that you are correct: it does depend on how much protein a person consumes. I don't know if there are any tests available for laypeople for protein content in urine, as there are for pregnancy, for instance. If there are such, it would be handy to have.

      Thanks for mentioning your carrot results from last year! That strengthens my suspicions about excess nitrogen and root crops. Another potential experiment ...