- Author: Mark Bolda
Part of my work has come to include substrate production of caneberries. Some of these are easy since they are pest management issues which don't vary that much from field problems, but others, like the nutritional situation depicted below, are far more complex.
A couple of things going on in this field, which are raspberries being grown in substrate under macro-tunnels. First, the very young leaves have a light yellow cast (see photo one below) to them and second the older leaves are seeming to have some difficulty (see second picture below), again becoming a sterner sort of yellow. I don't worry as much about the older leaves as I do the newer ones, which after all represent the future of the plant.
As you know, I'm not making any call without doing some thorough sampling. In this case, we took multiple samples of the younger leaves demonstrating the lighter shade of yellow and the same for the older yellowed leaves. To set the baseline, adult normal leaves (those surrounding the yellow leaves in the first picture below) were also sampled in multiple.
An important comment. We are sampling leaves of 3 different ages, and we should be aware that this is going to distort some of the concentrations. For example N, P, and K as plant mobile will by default trend higher in younger leaves, and nutrients such as Ca and B are going to trend higher in the older.
And sure enough in perusing the analysis below, N,P and K are higher in our newest leaves and lowest in the older, with the adult leaves in between. Likewise, Ca and B are very much higher in the oldest leaves than the other two age leaves, and as a matter of fact in the newest leaves these two nutrients are lower than what one normally would see recommended.
Mineral | Adult normal leaf | New, yellow | Old, yellow |
N (%) | 3.1 | 3.6 | 2.3 |
P (%) | 0.21 | 0.32 | 0.20 |
K (%) | 1.6 | 2.3 | 2.1 |
Ca (%) | 0.9 | 0.6 | 1.4 |
Mg (%) | 0.5 | 0.4 | 0.7 |
Na (%) | 0.02 | 0.02 | 0.03 |
Fe (ppm) | 503 | 336 | 1321 |
B (ppm) | 33 | 20 | 78 |
Zn (ppm) | 23 | 28 | 23 |
Cu (ppm) | 4.1 | 5.8 | 3.7 |
Mn (ppm) | 343 | 321 | 469 |
Moving on however to the levels of iron things get a bit more interesting. While it is highly accumulated in the oldest leaves, it is far less so in the youngest at 4x less, and 3x in the normal adult leaves. Calcium shows a similar pattern of concentration, but the visual symptoms are nothing like what we know calcium deficiency to look like. Iron deficiency, on the other hand, usually described as chlorosis of one type of another, as a matter of fact does. In addition, we know that nitrogen can accentuate iron deficiencies because of growth promotion.
The older leaves turning yellow? It seems to me they are just old leaves, might be some dieback being pushed by high tunnel heat but nothing that excites a lot of attention.
In other words, it looks like the plant is outgrowing its ability to pull up iron for the moment. Given that we've had (still in October of all things!) some pretty hot plant growth weather, once the weather cools down a lot of this should disappear.
My advice to the grower is watch this one, I'm not sure yet concrete action is merited yet, best to see if once the plant slows down in its growth and nitrogen accumulation these symptoms subside.
![Note the contrast of these newer leaves to the midtier leaves around them. Not an plant mobile nutrient, like NPK, so what could be the issue? Note the contrast of these newer leaves to the midtier leaves around them. Not an plant mobile nutrient, like NPK, so what could be the issue?](/blogs/blogcore/blogfiles/56057.jpg)
![On the other hand, many of the very oldest leaves were showing these symptoms, which look a lot like heat or salt damage. On the other hand, many of the very oldest leaves were showing these symptoms, which look a lot like heat or salt damage.](/blogs/blogcore/blogfiles/56058.jpg)
- Author: Mark Bolda
Pretty decent article here from the Capitol Press on how growers are struggling with how to make sense of the really large amounts of data so easily available to them in our increasingly technological age.
The fact of the matter is that reduced computing costs have created an enormous wave of information, and in a recent article in the Wall Street Journal written by Michael Milken and Igor Tulchinsky, caution us to buckle up because this already large tsunami of data "doubles in size every few years". The two authors, while conceding that this is a challenge, also recognize it as an opportunity.
As many are finding, the problem of understanding the meaning of lots and lots of data is deeper than just pressing the whole undifferentiated mass into Google and getting an actionable answer. I would suggest it is rather more a matter of sorting out the unimportant data from the important, and then having the mastery of that body of knowledge to which the data refer and only then be able put it all together to arrive at a good decision.
The book titled "The Signal and the Noise", written by statistician Nate Silver makes some progress on this issue. A lot of the data available to decision makers and prognosticators in a wide range of fields, from weather, to markets, to sports events, to elections, and yes to agriculture is not that useful, is not worth listening to and can be called noise, while those bits that are really useful, the signals, are where we should be spending our time and attention.
Complicating this however is the fact that it's very rarely just one signal that merits our attention, but rather it can be a multiple or even further an interaction of these signals which is most meaningful, and yet not all are as equally important. Take for the example the malnourished plant with a compromised root system. Is the malnourishment truly just the roots, or do we also face some deficiencies in the soil? What of the soil pH or CEC which might be impeding the transmission of these nutrients to the plant? The knowledgeable person is going to know what compromises a root system, what soil nutrient deficiencies look like, what a pH of x means to the whole shebang and weighs its value, pieces the important parts together, discards the rest and then makes the call on how to proceed.
In short, it is a deception to think that simply having access to ever greater amounts data effortlessly bestows upon one the ability to make better and more accurate decisions. Really it takes some accomplishment, experience and quite frankly a lot of hard work as an individual to sort out the signals from the noise, and further be able to put this concert of signals into a comprehensible whole.
![What were the signals and what was the noise for investors to avoid this near 50% schmeissing on this insurance stock? A clue, the big signal isn't even here. What were the signals and what was the noise for investors to avoid this near 50% schmeissing on this insurance stock? A clue, the big signal isn't even here.](/blogs/blogcore/blogfiles/42902.png)
![That about sums it up. That about sums it up.](/blogs/blogcore/blogfiles/43851.jpg)
- Author: Ben Faber
Since Greek and Roman times, the appearance of a plant has been used to help identify plant health. The plant speaks through distress signals. The message may be that there is simply too little or too much water. Or the sign may tell us of a disease caused by a microorganism, such as a bacteria, virus or fungus. The plant may show symptoms of attack by nematodes, insects or rodents or from injuries from frost or lightning. According to the plant species these signals may differ slightly, but frequently they can be generalized.
It is also possible to generalize about the signals linked to the nutritional status of a plant. Learning these symptoms can alert us to appropriate steps to correct the toxicity, deficiency or imbalance of nutrients.
There are 17 elements essential for plant growth. Hydrogen, oxygen, and carbon come either from the air or water. The others come from the soil. Depending on the quantity needed by the plant, these are called either primary or trace (micronutrients) nutrients. The micronutrient nickel is required in such small amounts (50 -100 parts per billion) by plants that it was identified only last year as being an essential nutrient. Other micronutrients are iron, manganese, boron, chlorine, zinc, copper and molybdenum. Some other nutrients have been identified as being essential for only certain plants, such as silicon for sugar cane.
The primary nutrients are measured on a percent (parts per 100) dry weight tissue basis. These are nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. The trace elements are measured on a part per million dry weight basis. For example, a typical analysis of a dried leaf from a healthy cherimoya might show 2% nitrogen, 1% potassium, 100 ppm (parts per million) iron and 50 ppm boron.
Although plants require more primary than trace nutrients, all the essential elements need to be present for a healthy plant. An excess, deficiency or even an imbalance of these elements will lead to individual symptoms which are characteristic to most plants. Because of our climate and soils, Southern California has different nutritional problems from those of much of the rest of the country. What is a problem in Massachusetts may rarely be a problem here. The following list is a description of the more common nutritional problems in most plants in Southern California.
Excess or toxicity (usually related to irrigation practices)
*Boron - chlorosis (yellowing), leading to tissue death (necrosis) along the margins of older leaves.
*Sodium , Chloride - necrosis of the leaf tips and margins on older leaves.
Deficiency
*Phosphorus - frequently the only symptom is smaller plants, but occasionally the leaves are darker than normal or may have a reddish cast, a common symptom in sweet corn. Phosphorus deficiency in California trees is rare.
*Potassium - scorching or firing along leaf margins that usually first appears in older leaves. Plants grow slowly and have a poorly developed root system. Stalks are often weak and fall over.
*Nitrogen - plants are light green or yellow. Older leaves are often affected first, but in trees the chlorosis may appear on any part of the plant.
*Zinc - depending on the plant there may be interveinal (between the leaf veins) chlorosis on younger leaves, but frequently the leaves are small and appear in a rosette.
*Iron - very sharply defined interveinal chlorosis of younger leaves, with little size reduction. Can often be associated with wet soil conditions.
*Manganese - mild interveinal chlorosis of younger leaves, with no size reduction.
These and other problems can be corrected with appropriate fertilizers, amendments and manures and also by soil and water management. In well-managed plants you may never see these signs, but learning the signals can help direct your activities if you do. Sweet corn is a wonderful indicator plant which develops very prominent symptoms according to the deficiency. Planting a row of sweet corn (not field) is a tasty way to determine if your soil has a generic nutritional problem.
![iron dieback citrus iron dieback citrus](/blogs/blogcore/blogfiles/29236.jpg)
- Author: Mark Bolda
Excellent article posted on the Salinas Valley blog by colleagues Richard Smith and Tim Hartz on zinc nutrition of crops and soils in the Salinas Valley.
Key takeaways:
1- Historically zinc deficiency was common in California, but now because of widespread use of zinc fertilizers, zinc deficiency is pretty rare. I concur, and as a matter of fact have yet to find a single plant sample which was deficient for zinc.
2- Bioavailability of zinc is limited by increasing soil pH, high clay content, high phosphorous and low soil temperature.
3- Tissue zinc sufficiency is between 15- 30 ppm (anecdotal note- blackberries tend to be in the range of 40 ppm)
4- Most common soil zinc test is DTPA extraction, which gives a good estimate of what is plant available. Generally, soil DTPA extracts from 0.5 ppm - 1.5 ppm means crop plants in that soil would probably respond to the addition of a zinc fertilizer, while a test above 1.5 ppm means there likely will be no plant response to zinc addition.
You really should read the whole article, it's quite good and definitely worth the while:
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13163
![Zinc Zinc](/blogs/blogcore/blogfiles/21411.jpg)
- Author: Richard Smith and Stuart Pettygrove, Farm Advisor, Monterey County and Soil Specialist, UC Davis
Potassium is a critical nutrient in vegetable production in the Salinas Valley. In nearly all key vegetable crops that are produced here, the amount of potassium removed in the harvested crop is similar to or exceeds that of nitrogen (Table 1). Potassium dynamics in the soil are distinctly different from nitrogen, and the need for it can be assessed by a soil test. Ammonium acetate extraction is the most common technique for assessing potassium availability in the soil. Some laboratories use the Mehlich-3 test, which gives numerically a similar result to the ammonium acetate method. In general crops growing in soils with test values above 200 ppm do not respond to potassium fertilization (Table 2). In general, the decomposed granite soils on the eastside tend to have the lowest potassium levels in the Salinas Valley, while clay loams and clays tend to have higher values (Table 3). However, due to fertilization practices there are some exceptions noted in the 2010 survey of Central Coast soils.
However, there are some details about potassium that need to be kept in mind; the standard soil tests for K (ammonium acetate and Mehlich-3 analytical methods) provide an index of available potassium and not a quantitative measure of soil potassium content. Other cations in the soil solution (calcium, magnesium, sodium, ammonium) can compete for plant uptake, and therefore it can be helpful to look at the percent potassium of exchangeable soil cations. Cation competition with potassium is not a problem if potassium makes up more than 3% of exchangeable cations. In soils where potassium makes up less than 2% of exchangeable cations, potassium uptake may be restricted. Table 3 shows examples of soils with relatively high potassium levels; in some of these soils potassium is relatively low as a percent of exchangeable cations and may be of concern.
Potassium uptake by plants is affected by the density of the root system of the plant. Factors that affect root development affect potassium uptake: rooting depth, irrigation system (drip vs sprinkler), soil compaction and root disease. In general, any production practice or unfavorable soil condition that reduces rooting density will reduce potassium uptake. An advantage of drip irrigation over sprinkler is the ability to deliver a concentrated dose of potassium by fertigation at the time of the season when demand is highest.
Certain soils have a tendency to fix potassium and make it unavailable or only slowly available to plants. Soils that contain large amounts of the silicate mineral vermiculite have the ability to trap the potassium ions between layers of the crystalline structure of the mineral, thereby making it unavailable to plants. Vermiculite is generally associated with soils derived from granite, but the type of granite affects the levels of vermiculite. In addition, the age of the alluvium and the degree of weathering impacts the quantity of vermiculite in the soil. Very young soils may not have had sufficient time for all the parent material potassium (in mica and hydrous mica) to weather out of it, and will not have a significant K fixation potential. On the other hand, in very old soils, the vermiculite may have weathered to a different type of clay (smectite) which does not have the proper crystalline structure to fix potassium. Soils with high levels of potassium (e.g., > 200 ppm) are likely low in vermiculite and have little or no potential to fix potassium.
Potassium fixation potential has been identified in some soils used for cotton and other crops on the east side of the San Joaquin Valley but has not been examined in other parts of California. In a recent survey of a small number of soil samples from Salinas Valley vegetable field, none were found to fix potassium in a UC Davis laboratory test for this. The lack of fixation capacity in Salinas Valley soils may reflect the impact of crop production and past fertilization practices. Crop production may affect the weathering of vermiculite on the surface layer of soil. Fertilization practices over the years result in higher soil potassium levels which can saturate potassium fixing sites in the soil minerals.
Potassium is also capable of leaching from soils. We conducted an evaluation of leaching during winter storms on a sandy loam soil on the eastside of the Salinas Valley. The amount of anions and cations leached was measured using suction lysimeters placed two feet deep in the soil; in addition, we measured the quantity of moisture moving through the soil during each rain event. The data indicates that there was movement of potassium and other ions deeper in the soil profile (Table 4). It is interesting to note that, the relative loss of potassium was much less than other cations. Potassium is bound to the negatively charged sites on clay and soil organic matter and losses of potassium due to leaching are generally assumed to be low rich in these materials.
In general, there appears to be robust levels of potassium in some Salinas Valley soils. This is particularly true for heavier soils. However, crop removal by many Salinas Valley crops is also quite robust. Fertilization with potassium does not have the environmental consequences that we observe with nitrogen and phosphorus and it seems prudent to utilize potassium fertilization programs that replace potassium that leaves the farm in harvested product and to use soil testing to monitor the situation.
Table 1. Nutrient content of Salinas Valley crops at harvest (lbs/acre).
Crop |
Nitrogen |
Potassium |
Lettuce |
90 – 1401 |
150 – 180 |
Broccoli |
180 – 220 |
160 – 240 |
Cauliflower |
180 – 220 |
160 – 240 |
Celery |
180 – 240 |
350 – 450 |
Spinach - clip |
60-1102 |
25-552 |
1 – higher nitrogen uptake occurs on 5-6 seedlines on 80 inch beds;
2 – these values are currently being evaluated by a research project
Table 2. Soil adequacy levels of potassium for Salinas
Valley cool season crops
Crop Response |
Potassium ppm |
|
Celery |
Other cool season vegetables |
|
Response unlikely |
>200 |
>150 |
May respond |
150 – 200 |
100-150 |
Response likely |
<150 |
<100 |
Table 3. Analyses of 14 Central Coast soils for available potassium
(ammonium acetate extraction top foot of soil) in 2010
No. |
Soil Type |
Potassium ppm |
Potassium percent of all cations |
Sand % |
Silt % |
Clay % |
1 |
Chualar Loam |
182 |
3.2 |
53 |
30 |
17 |
2 |
Metz loamy sand |
112 |
3.7 |
84 |
10 |
6 |
3 |
Metz loamy sand |
182 |
2.7 |
80 |
10 |
10 |
4 |
Gary sandy loam |
147 |
2.0 |
69 |
16 |
15 |
5 |
Cropley clay |
419 |
3.1 |
27 |
31 |
42 |
6 |
Mocho silty clay |
317 |
2.3 |
15 |
52 |
33 |
7 |
Salinas clay loam |
500 |
3.8 |
33 |
31 |
36 |
8 |
Sorrento clay loam |
424 |
3.7 |
21 |
50 |
29 |
9 |
Chualar sandy loam |
370 |
7.9 |
75 |
15 |
10 |
10 |
Clear lake clay |
496 |
3.6 |
18 |
41 |
41 |
11 |
Salinas loam |
217 |
2.6 |
35 |
41 |
24 |
12 |
Antioch sandy loam |
171 |
1.6 |
38 |
34 |
28 |
13 |
Sorrento clay loam |
346 |
3.5 |
26 |
45 |
29 |
14 |
Sorrento clay loam |
261 |
2.0 |
37 |
29 |
34 |
|
Mean |
296 |
3.3 |
44 |
31 |
25 |
Table 4. Estimate of cations and anions leached during winter
storm events (winter 2009-2010) under three cover crop treatments
Cover crop treatment |
Nutrient leached (lbs/A) |
|||||
K |
Ca |
Mg |
Na |
Cl |
SO4-S |
|
Bare Fallow |
9 |
133 |
32 |
88 |
158 |
36 |
Triticale |
18 |
216 |
55 |
178 |
275 |
60 |
Rye |
16 |
226 |
63 |
191 |
289 |
69 |