T2: Sand-Loam Tree Line  (30.06.2023)

The soil profile dug for T2 last year missed the beginning of the sandy area by about 6 meters, so this is the first profile dug directly into the largest area of sand-loam on site.

Soil Surface

The soil surface is covered with a mulch of composted horse manure. There are very few plants: even the weeds barely grow and the small garlic cloves have failed by this point in the drought.

T2 soil surface; notice beyond the silage tarp how many grasses died from the tillage in this patch of sand-loam soil; also inside the tree line the lack of plants, notice the dearth of garlic- most had died by this time. The dark color under the center line is due to the irrigation system working to save the system after drought.

Soil Profile

A profile was dug down to 50 cm. The topsoil reaches down 20 cm until there's a very distinct color shift from brown sand-loam to an orange, reddish tinted sand, perhaps from oxidized iron in the soil. There are quite a lot of stones, their size and quantity increase by 30 cm depth, with a very large stone found there. The topsoil has a very fine texture- just like the subsoil- but the dark color until 20 cm corresponds to 1) more soil moisture being held by the soil carbon and 2) the residual effect of the plant roots on soil aggregation. However, you can only see one type of root.

Example of soil texture: almost exclusively sand; very little aggregation due to the fact that the roots are dead- having been tilled in 2022 to prepare the site and the inability of us to establish a cover crop then due to drought and the lack of precipitation to support the garlic in 2023 prior to the irrigation system.

The old root system of the grass is still quite visible, some dead roots are found to the bottom of the profile. Given the porosity of this sandy patch, it is not surprising to find roots down to 30 cm in larger quantities than elsewhere.

However, aggregation is extremely poor to nonexistent. Tillage killed most of the grasses in this patch and without a strong garlic crop we don't even have aggregation in the top 1-5 cm like we find elsewhere.

Compaction is not an issue, though there are many stones. Likewise, the smell is neutral and very little odor to be expected from sand.

I have highlighted one earthworm burrow (teal star) observed in the photograph, but not seen while taking these notes. I did not see any living earthworms or other soil organisms.

The only hint that plowing took place in this profile is the dramatic shift in soil color seen after 20 cm depth, which corresponds with the typical depth found elsewhere. 

Overall

Despite having dug the tree holes here earlier it was still surprising to me the quantity and proportion of sand in this section of T2. The profile may be more accurately described as sand with some loam rather than as a sand-loam. However, given the heterogeneity of glacial soils, we will continue to use this phrase as even a few meters away you find true sand-loam. Each soil sample has come back from the NIR test with rather wide range of soil composition.

With precipitation and irrigation, I suspect that this soil could recover quicker than the clay-loams due to the lack of a very serious compaction problem. Fostering diverse living roots, keeping the soil covered, and encouraging the growth of perennials will do good things.

A3: Clay-Loam Alley (05.07.2023)

Note: the following soil profiles were dug a week later than T2 on July 5th, 2023.

Soil Surface

The surface is alternately bare and vegetated. Vegetation is in strips where the Vibroflex and harrow did not kill the couch grass. The recent rain (in the past week) has moistened the surface enough for the cover crop sown at the end of May (over one month ago) to begin to germinate, some of those seedlings are visible. The germination rate is poor and the grass is going to out compete many of the cover crop species. 

A3 general view: very much still drought conditions at the start of July.

Compared to the plan, very little biological activity for the first week of July. Still, more growth than in the Sand-Loam Tree Line.

Soil surface: some cover crops can be made out, particularly those of the tillage radish.

Soil Profile

When I look at the soil profile, we can see that the near monoculture of grass has grown densely with rhizomes about 10 cm down from the soil surface. The color of the soil is darker in the top soil until around 20 cm. This is what I had observed in previous soil profiles. The soil is more moist at the bottom of the profile than the soil surface, despite the recent light rain. There is very little evidence of much going on in terms of biology: aggregation is poor and there are no visible soil macrofauna. The soil is very, very dense and it took considerable effort to remove the smearing of the wall of the profile enough to see some original texture.

Despite the density of the soil, roots extend all the way down to the bottom of the soil pit. The roots are fine roots. I don't see any strong taproots from any other species. 

Aggregation is restricted to the topmost 5 cm or so; after which the density of roots noticeably declines.

Compaction is evident with the remnants of straw buried by tillage 20 cm down, as in previous profiles here and elsewhere on the farm. The soil does get a little bit looser after you break through the compaction.

The soil doesn't smell anaerobic despite the compaction.

I saw one or two earthworm burrows although I did not see any earthworms.

Overall

No change worth noting from the previous profiles dug in similar soils last year. Subsoiling once we have living roots from a well established cover crop could be a good way to accelerate conditions for regeneration. Without moisture and plants the soil cannot recover.

T4: Clay-Loam Tree Line (05.07.2023)

Soil Surface

Like T2, this is been covered with compost since early August of last year. Unlike T2, this profile is being dug in the east side of the tree line. I am also digging it where we will be turning the tree line into a margin due to the new design. This was the last part of the tree lines to be covered with silage tarps in June, so it has been under occultation for exactly three weeks. This is not long enough to have killed the grass, though much of it is turning yellow now. The compost layer is still intact.

View of the east side of T4 being uncovered for digging a soil profile.

A closer look at the surface, the effect of 3 weeks of occultation on couch grass.

Soil Profile

The soil is a little bit different than the adjacent alley profile. There appears to be a trace more sand here, particularly towards 35-40 cm deep and below. The soil removed from the bottom of the profile is noticeably lighter in texture. Although there is more sand, the soil is still quite blocky. Roots do go all the way down to the bottom of the 50 cm profile and you see a color shift at 20-25 cm deep.

Aggregation is as poor as all of the other profiles: only very small aggregates around the most active root layer, the compost and say 5-10 cm below that mulch.

It is drier because of the silage tarp preventing most infiltration. 

I do not see any soil organisms or earthworm burrows.

Plow pan is evident at the usual depth with correspondingly lower root observations below 20 cm.

Smell is neutral, neither earthy nor anaerobic.

Overall

No changes from the previous year.

M1: Clay-Loam Margin (05.07.2023)

Soil Surface

The soil surface is much less populated by plants than the alley profile. This is likely due to the extra harrowing that took place here: to accesss the alleys, one needs to use the margins more and thus the harrow was run here more often. Also, by turning to other alleys, the harrow was run in multiple directions (parallel to the fence, but also in semicircular fashion when turning into another alley), so not only were more passes undertaken but they tilled the soil in multiple directions.

Above: A simple illustration of the multiple passes the headlands received when harrowing the grass clods before planting. Depending on the tools used and the objectives, this passing of the soil in multiple directions may be more useful than a single pass. Future management of grasses in the alleys may be hindered by the fact that it will only be possible to cultivate in a single direction.

Germination of the cover crops is just beginning here as well, like A3, not as thick or strong as one would wish.

View of M1 looking towards T4: notice how much more grass is living in A3 (to right of T4, marked by the blue lay-flat irrigation hose)

M1 soil surface: a lot less grass, germination of cover crops is visible but not strong

Soil Profile

The soil here seemed less compact than the other two that I dug with similar clay-loam soil. Oddly the soil here was coming off in larger chunks even if it was easier to dig. This may be due to the extra harrowing that took place here pulverizing the soil.

The top soil is very similar to the other ones. There are less fine roots from the grass than in other sections, but it follows the same pattern as before in which we have more roots present until you reach 20 cm down where the old plow pan is. After that, the number of roots diminishes.

The main difference is the pulverization from the more successful attempt to kill the grass here than elsewhere. This has resulted in an unclear soil surface, no large numbers of strong living grass roots creating aggregation. It is a good example of what soil disturbance can do.

We can see straw buried underground that has not decomposed at that level (circled in pink).

Soil is blocky, same smell as other profiles.

Likewise with the other samples, no observed earth worms or other soil life.

Overall

No improvements over the previous year. Perhaps the only benefit here is that the grass has been suppressed better than elsewhere.

When and how many? 

In the chart on the left, you can see when we collected samples, which species, where they were collected from, how many samples on that date per crop, and explanatory notes. Given the total number of samples we collected and the number of PDF reports we have, we will not be uploading every analysis.

If you wish to have the raw data in an excel format you can contact me with a request.

Phosphorus (P)

One of the most interesting things we found is that despite both conventional and NIR soil testing indicating a general lack of available phosphorus, P was rarely deficient in any of the sap samples with suggested levels from NCC. According to our conventional tests, the average available phosphorus measured across 2023 clay-loam samples was just 4,4 mg/l. The NIR sampling suggested we had more available P than the conventional tests, with 5/10 measurements being in the “good” range. Of the other half of the measurements, P was a “little low” 4 times and low once. As mentioned in the 2022 analysis, both laboratory measurements of soil P indicated that total reserves available are quite high (e.g., > 3 000 kg/ha).

So, what did the sap show?

Garlic

In 17 garlic samples, phosphorus was deficient in 8. However, of those 8, only 4 were at least 10% below the threshold of optimal. Garlic P levels were optimal 7 times and excessive twice (both the old and new leaves of the very first sap analysis).

Grasses

In the alley grasses, P was never deficient and in fact it was excessive 15/20 times. (Left: graph showing the P levels in each normal alley sample ["good" and "poor" measurements were only taken twice over this period] in parts per million, optimal range lies between the two black square dotted lines)

In the margin grasses, P was never deficient and was excessive 16/22 times.

Radish

Finally, in the radish samples, P was excessive 6/6 times.

P summary

Of 65 samples from three species with recommended levels from NCC, P was deficient only 12% of the time and excessive 60% of the time. It is worth noting that 75/81 (92,5%) of the sap samples were collected after the drought broke and water was no longer a limiting factor (of course damage had taken place to the system’s overall health). In fact, the only deficiencies in P were recorded during the drought period in garlic alone. Were the grasses and radishes accessing P from the reserve pool? Would the garlic have had enough phosphorus if ample water were available? We cannot say for sure, but it is very interesting that despite rather low P measurements in the soil, the plant sap analysis said P was excessive so often.

Nitrogen (N)
 

Before diving into nitrogen, it is interesting to note that our sap analysis showed very low levels of nitrates in the plant sap. Nitrates were either always optimal or even deficient in garlic, grass, and radish. In rhubarb, however, nitrate levels were much higher than any other species on 29.08.2023 (coinciding with the large rain event) and those levels remained elevated over prior samples or other species even into September.

Soil tests do not tell us how much nitrogen is available, but the NIR soil test does provide a nitrogen “release capacity.” Like with other nutrients in the NIR test, these figures are labeled as low, a little low, and good. Of the ten clay-loam samples, only once was this figure labeled as “good” and barely reached that threshold when it did (100 kg N/ha release capacity in Clay-Loam Margin Spring 2023). The same tests, however, suggest that the total nitrogen reserve, is, on average, more than 5 000 kilograms per hectare. Now, under no circumstances would anyone wish to have even 10% of that be available. What it does mean, however, is that there is nitrogen in the system which some suggest that, under the right circumstances, could be moved from the inaccessible reserve to the plants through biological mechanisms.

Keep in mind that no nitrogen has been applied to the soil in the alleys and margins since 2018. The only nitrogen provided directly to the system in quantity is from the composted horse manure applied to the tree lines. Later, nitrogen was applied in the form of fish hydrolysate in a mix with compost extract and seaweed extract with the tractor’s sprayer to the alleys and margins on 24.07.2023.

So, what did the sap show for total nitrogen? We could also look at ammonium (NH4) and nitrate (NO3) results, but to keep this manageable and understanding our single season of data, we will just look at the total nitrogen.

Garlic

In 17 garlic samples, total nitrogen was deficient in just 2 samples. Otherwise, it was optimal 12/17 times and excessive 3 times (two of these are the first paired sample from May). Neither of the two deficiencies were > 3% beneath the threshold for optimal garlic sap.

We thought that nitrogen should be available in greater amounts here because of the compost, however, the NIR tests do not indicate any significant difference in the N release capacity between the two tree lines where compost was added and two other sampling locations compost. This is likely in part because the compost was added a mulch and only partially mixed into the soil during management (weeding and harvesting). Therefore, most of the impact of the N in the compost would come from leaching, which could be detected by the NIR soil test as releasable N. But this is not what the soil tests indicate so far.

Despite low release capacity in the soil across the time frame, our garlic had ample or even excessive nitrogen available to it.

Grasses

In the alley samples, total nitrogen was deficient just once. This deficiency was detected in a sample of grass that we labeled as being in “poor” condition; when tested two weeks later this same area of grass returned to optimal levels. Otherwise, alley grasses were optimal 12/20 times and excessive 7 times. Of those excessive nitrogen measurements, 4 were from A1; every grass sample from A1 had more nitrogen than NCC considers optimal. (Right: graph showing the N levels in each normal alley sample ["good" and "poor" measurements were only taken twice over this period] in parts per million, optimal range lies between the two black square dotted lines)

In the margins? Grass was deficient once, optimal 12/22, and excessive 9/22 times. Of those excessive measurements, 4 were samples collected from the area of M1 where the compost had sat prior to being used as mulch. This area consistently had the highest nitrogen levels and always was excessive.

As mentioned above, the alleys and margins were sprayed in late July with 1,5 liters of fish hydrolysate in a foliar mix (150 l water, 1% solution). We recorded from sap samples taken immediately prior and one week later, an average increase in total N of about 200 ppm. We cannot say that this 1% by volume application of fish plus compost and seaweed extracts necessarily caused this result, but an intervention took place and changes were recorded after.

Continued monitoring of the grasses across the site showed that the nitrogen levels remained consistently optimal even weeks to months after application.

Radish

Total N in the 6 radish samples were optimal 5/6 times and excessive once, no deficiencies.

N Conclusion

If we accept NCC’s recommended values, nitrogen was not a limiting factor in any of the crops we tested. This is an unexpected result given the history of fertilization, the differing crop species, and the impression we had from both soil samples and our own observations.

Potassium (K)
 

Potassium has consistently been a nutrient that both laboratory soil analyses report as being both available and in reserve in ample or excessive quantities across the testing period. In fact, as the samples were collected in summer and autumn 2023, the NIR test suggested that the available potassium would be in excess. This coincides with the increased soil moisture as the season progressed, particularly after the very large storm which dropped ±100 mm of precipitation at the end of August, right around the time of summer soil sampling.

Excess potassium has several negative effects not only on the plants, but also on soil chemistry. In clay soils, it may cause dispersal/poor stability of clay particles in addition creating availability issues of key micronutrients in plants.*

*See, for example, "Effect of applied potassium concentration on clay dispersion, hydraulic conductivity, pore structure and mineralogy of two contrasting Australian soils, link."

If so, this could help account for the lack of soil structure across the site.

Garlic

Garlic displayed a general lack of potassium throughout the growing season, including in the first samples collected in mid-May (12.05.2023) and early June (09.06.2023) when the drought was steadily progressing. The situation with the garlic was deteriorating rapidly by early June, which can severely limit the availability of potassium to plants. This could have been picked up on by the sap analysis with a reversal in the relative concentration of potassium in the samples: the May young garlic leaves had higher than the old, whereas by June this had reversed.

Overall, potassium was rated deficient 14/17 times and only optimal three. Never excessive in garlic. On average the old leaves had 1,21 times as much potassium as the new leaves. When examining the difference from the lowest threshold for optimal, garlic old leaves were on average only 99% of the lowest optimal, while the new leaf average was 18% below that same number.

Grasses

The grasses began to be tested after the drought broke, which can help explain the difference between the garlic and grass.

In the alleys, the grass measured: excessive 13/20, optimal 6/20, deficient 1/20. These results closely align with the suggestion from the NIR tests that we would have excessive available potassium, as opposed to the conventional soil test which reported satisfactory or good levels. (Left: graph showing the K levels in each normal alley sample ["good" and "poor" measurements were only taken twice over this period] in parts per million, optimal range lies between the two black square dotted lines)

In the margins: excessive 15/22, optimal 5/22, deficient 2/22. Similarly to nitrogen, we see elevated levels of potassium in grasses from M1 where the compost sat. In the M1 compost patch sample, at the end of July (coinciding with 7 days after the spray mentioned earlier), potassium levels rose to more than ten thousand parts per million, fully 1,5 times the high range of optimal. By late August and September, these numbers and dropped some but were still wildly excessive (> 6650 ppm).

Radish

Potassium was measured as excessive in all six samples, with the older leaves containing more potassium than the new ones.

K Conclusion

A lack of potassium does not appear to be a limiting factor in production at this site, from soil and sap perspectives. In fact, the opposite appears to be the case. The soil’s cation exchange capacity is imbalanced towards potassium (and magnesium [Mg]) with a limited calcium component. Will it even be possible to remediate excess potassium without altering the soil’s chemistry through the application of limestone? Only time will tell if a focus on plant community diversity and removing roadblocks to plant health through foliar applications will alter the soil’s chemistry to any significant degree.

Calcium (Ca)
 

The soil reports regarding calcium are very similar to those about phosphorus: our soil is reported as deficient or low, sometimes with NIR readings as low as only 10 kg of calcium per hectare. With no additional calcium being added to the soil in the near term, except which came with the horse manure compost, the expectation would be to have very low calcium readings.

Garlic

Calcium in the garlic leaves changed dramatically between the May, June, and July samples. In May, both the old and new leaves were very deficient: the young leaves in May had only 17% of the lowest optimal calcium parts per million suggested by NCC. The older leaves were better, but only by comparison, about 51% of the lowest optimal. These levels began to improve by June’s sampling, with the young leaves still strongly deficient at 28% of the lowest optimum, but the older leaves had improved to just within the optimal range. By the time we harvested, the situation reversed: the young leaves began to, except on one of six sets of paired garlic samples, have more calcium than the old leaves. In each case, the levels were well within the optimal range and one pair of garlic leaves (from T4’s 10-20 meter section) the calcium levels were in excess.

In total, calcium was measured as: excessive 2/17, optimal 12/17, and deficient 3/17.

Grasses

In the alleys, calcium was measured as: excessive 5/20, optimal 10/20, and deficient 5/20. Of those deficiencies, two samples were less than 90% of the lowest optimal. (Right: graph showing the Ca levels in each normal alley sample ["good" and "poor" measurements were only taken twice over this period] in parts per million, optimal range lies between the two black square dotted lines)

In the margins, calcium was measured as: excessive 4/22, optimal 11/22, and deficient 7/22. Interestingly, the excessive calcium measurements always came from the species of grass growing along the fence in the M4 collection area (which also included couch grass and another species growing adjacent to the tree line).

Radish

Radishes displayed very low levels of calcium: all 6 samples were deficient. If one needed a strong indication that excessive potassium can influence the uptake of other nutrients such as calcium, this would be a good one to look at. However, the excess of potassium did not seem to impact the boron (which were optimal- the only deficiency was less than 1% of optimal) or manganese (which was almost universally excessive) levels. The average calcium level was only 38% of the lowest optimal range.

Ca Conclusion

This is an interesting conundrum. The calcium levels are, by most laboratory measures, low in our soil. Even the reserves are considered low. Yet, only the radishes were consistently deficient. Otherwise, the grasses across the site generally had sufficient or even excessive amounts of calcium in their sap. And with the garlic, we saw that by the end of their growing season, levels had reached optimal levels or been driven to excess on one occasion.

In the case of our garlic, the plants received some calcium through foliar applications which included whole cow’s milk on three occasions: 150 ml on 23.05, 100 ml on 06.06, and 200 ml on 14.06; or 1,25%, 0,8%, and 1,6% of the 12-liter mix, respectively. Whether the calcium in the whole milk, compost extract, seaweed extract, or fish hydrolysate could account for the increases in calcium measured once again, more than one month later, in July is questionable.

In the case of the grasses, we did see an increase in calcium that coincided with the application of the fish, seaweed, and compost foliar. Fish hydrolysate is made from whole fish, bones and their calcium included. But given the limited mobility of calcium within plants, would this account for the sufficient levels of calcium seen throughout the rest of the season, with measurements being taken many weeks to months later?

As the project heads into spring 2024 and we begin to collect plant sap analysis again, we will continue to monitor all the plant nutrients closely. Calcium is going to be high on our list to detect deficiencies for and attempt to help through foliar applications, despite their limited function. Our goal will be to continue assisting the plants in the creation of healthy soil which can begin to move nutrients from the reserves. Will this be enough in the face of competitive ions such as potassium being in such excess? Again, only time will tell. However, as stated elsewhere, if we apply lime to the soil to increase pH and provide additional calcium, we will not be able to test if the plants could have managed it together with our assistance from above. Unless, of course, we wait 7+ years for the effect of the limestone to diminish and "start over."

Plant Sap Analysis: Micronutrients
 

One reason we want to use sap analysis is to see levels of nutrients which are not reported on our soil tests, such as molybdenum (Mo), boron (B), and iron (Fe). Nearly all nutrients play important roles in the plants’ overall health. Despite not being needed in large amounts, when plants are deficient in these three nutrients, their capacity to photosynthesize is decreased. Iron is perhaps one of the oddest of the micronutrients in that its presence in the soil can almost be taken for granted as the most abundant element in earth’s crust, but iron is often deficient in many plants.

The results of our plant sap analysis indicate that, across garlic, grasses, and radish, molybdenum was either deficient or barely optimal.  We also found that boron was a limiting factor at different times for different species, with levels dropping in the summer-early autumn samples across the board. (Left: graph showing the Mo levels in each normal alley sample ["good" and "poor" measurements were only taken twice over this period] in parts per million, optimal range lies between the two black square dotted lines)

Finally, iron was not even vaguely uniform in its uptake across the species. It was found in ample amounts early in the garlic, but levels began to decrease later in the season. With radish, iron levels increased as the plants aged from deficient to optimal and excessive amounts. In the grass samples, iron was more likely to be optimal than the other species. Still, it is one to keep a close eye on and have available for formulating into foliar applications as it plays such a critical role in the plant’s growth.

Other micronutrients, such as copper (Cu), zinc (Zn), and even silica (Si) all have a role to play. But with more than 80 samples and 22 parameters each, the “complete” look at sap analysis would take a lot more time and effort than it is worth at this stage. We can only look at the basics for now. In 3 years, when we have 4 years of sap analysis, we can start to get serious about trends and statistics.