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Connecticut

After reading the article “Potassium Paradox” (link: http://journals.cambridge.org/raf/potassium) that was posted on the message board, I had some differing opinions that I wanted to share with the community. In science there are often varying opinions so I have done the best to not only present my thoughts but also provide links to support my ideas.

While all three parts are important to read and understand growers may find part 3 on salt the most interesting and eye opening. I do not know of many growers that would say they have added high amounts of salt to their patch, but as I show, odds are you have added high amounts of salt to you patch already.

This posting is not intended to add confusion but more importantly add some greater detailed information to help all growers understand some of the concepts brought up in the article and some other ways of considering the information presented.

If you want a general background on potassium fertilization in relation to crop production at a look at these links:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCkQFjAA&url=http%3A%2F%2Fwww.ianrpubs.unl.edu%2Fepublic%2Flive%2Fec155%2Fbuild%2Fec155-3.pdf&ei=R5yCUqr8GsqNtQagmYHoBA&usg=AFQjCNE34Rdxn_9VEwH_g_NTPSeW1CsPBw&bvm=bv.56146854,d.Yms

Here is another source worth looking at:

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex917

11/12/2013 6:37:15 PM

Connecticut

Part 1 Testing for K

First off, growers need to realize that soil test do not measure the total amount of nutrients in the soil. Soil tests represent an estimated value of plant available nutrients in the soil. While the study indicates there are some variables, to suggest soil testing has no practical use is simply not true and I think offers a misleading statement. If this statement was true than if a plot was sampled multiple times over the course of a year there should be widely varying results, and while I have multiple samples from the same plot I have data to show very consistent potassium levels. This makes it hard to believe that the soil testing is variable to the point it is not usable information, when there can be consistency in results over time.

Even if this was the case, I do not see in the article a suggestion for what the authors think is a reliable source for determining potassium levels. So, while it is easy to attack one method it is challenging to determine an improved system that is supported by data. Also, as the article points out a possible reason for the variability is basic field moisture content as this can affect the availability of potassium, which is true, but it goes on to say that labs that dry soil are providing inaccurate values, which I have not found to be the case.

To offer some data to soil test recommendations access this source:
http://www.dpi.vic.gov.au/agriculture/farming-management/soil-water/soil/understanding-soil-tests-pastures

Relating this to Giant Pumpkin Growers: Realize that soil test data is supported by tens of thousands of samples and has been tested over a long period of time. Also, the soil report you get back from the lab measures plant available levels and does not represent the total amount of potassium (or any other nutrient) in the soil. So, continue to take your soil samples properly and make decisions based on the data that is reported back to you.

11/12/2013 6:37:54 PM

Connecticut

Part 2 (section 1 of 2) KCl does not increase yields

KCl is not only an inexpensive form of potassium fertilizer but it is also one of the most nutrient dense forms of potassium fertilizer. To the farmers this means that that can buy less total tonnage of fertilizer and save shipping volume to reduce freight, and overall costs which is a benefit to all.

However, in the article you have to also consider the crops tested. Out of the crops mentioned there are no pumpkins or even squash. Grain crops are very different than cucurbits so the correlation between fertilizer and yield may not match across all plant species. I know that potassium can increase corn yield in some cases, but in comparison pumpkins have a greater potassium requirement.

Soil is a great storage capacity of potassium but this gets back to part #1 where we as growers are looking at the plant available nutrient levels and not the total levels in the soil. Potassium can be held tightly by some soil types, but to suggest potassium is immobile in soil I think again is misleading. In situations where sites are being irrigated with water that is high in sodium or where calcium and magnesium are being adding a ferti-irrigation style system can increase the potential for leaching. Highly organic soils, much like the ones we artificially create can have increased potassium leaching.

Good source to check out:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.soils.wisc.edu%2Fextension%2Fpubs%2FA2521.pdf&ei=7O2AUvWDM4aYtQbcu4CACg&usg=AFQjCNHHF3vMtkx9RL0PSnAtA6smEW4EKg&bvm=bv.56146854,d.Yms

This article does relate to turf grass but it does relate to potassium in the soil profile:

http://jimmcafee.tamu.edu/files/potassium%20a%20key%20nutrient%20for%20plant%20growth.pdf

11/12/2013 6:41:12 PM

Connecticut

Part 2 (section 2 of 2) KCl does not increase yields

“Large amounts of K+ are leached from soils in areas where crops are irrigated with water that contains significant concentrations of Ca2+ and other cations.” http://www.sciencedirect.com/science/article/pii/S0140196306002333

While our pumpkins are mostly water weight, it is important to note that depleting the very important plant available forms of potassium is typically first to occur in the soil.

Also, to suggest that if the soil report comes back optimum or high there is no fertilizer required is accurate because (back to part 1) the levels are based on thousands of data points and studies, so it should be common sense that if you are at the optimum level you do not need to add any more as there will be no yield / economic benefit.

Relating this to Giant Pumpkin Growers: Realize that there is no benefit to adding nutrients beyond the optimum rate in soil tests, and potassium can leach from the soil so you want to time your application closer to when your plants have a greater demand. (Pollination to season’s end is the time period pumpkins require more potassium.) Also, pumpkins are not represented in any part of the study being discussed, so when reading the article you can only infer how pumpkins and your soil type may react.

11/12/2013 6:42:07 PM

Connecticut

Part 3 (section 1 of 2) Negative effects of Cl

While this article seems to really focus on the negative effects of chloride I have a few interesting points that may put this into perspective for growers. While chloride does have potential negative effects in soil (this is why early civilizations would salt fields of their enemies to reduce their ability to produce food) there are many sources of salts and in some cases (and quantities) it can be beneficial.

First off, sodium chloride can actually reduce the incidence of fusarium on asparagus plots. Specifically for asparagus these plants have a high salt tolerance so that can influence this finding, and this shows how species of plant being tested can have a great influence on the results and findings. This is has open access, so you can view it in a pdf form if you want to read all the details.

http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS.2001.85.12.1271

While it is easy to calculate and see the salt in fertilizer and say it is negatively impacting the soil, most growers commonly add large doses of manure. Manure in most cases actually has a very high salt content. To give you some idea in 1,000sq feet 50 pounds of KCl would be extremely high (very, very excessive!) recommendation, but this would add about 25 pounds of salt! Who would want to do this? Hoverer, in comparison I know many growers that add 5 tons of manure to this same area. Well the manure that was added contains about 500 pounds of salt!!!!! (According to University of California Cooperative Extension, see link below) This sure makes the 25 pounds seem like trace amounts. So, remember salt is in more than just bagged fertilizer.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC8QFjAB&url=http%3A%2F%2Fcetulare.ucanr.edu%2Ffiles%2F82031.pdf&ei=_5uCUtCEGMrPtQbngoGACA&usg=AFQjCNF7V1GC4tQIQbn8MoLhyiFO8VAaFQ&bvm=bv.56146854,d.Yms

11/12/2013 6:43:45 PM

Connecticut

Part 3 (section 2 of 2) Negative effects of Cl

For reference here is a chart with some products and their salt index:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&sqi=2&ved=0CCkQFjAA&url=http%3A%2F%2Fwww.algreatlakes.com%2FPDF%2Ffactsheets%2FALGLFS15_Fertilizer_Salt_Index.PDF&ei=sZyCUtLLMYmStQaRmoH4Cg&usg=AFQjCNHIUEHC-0N_Ea7Sz66WauGWgSsIgQ&bvm=bv.56146854,d.Yms

Relating this to Giant Pumpkin Growers: Key part is not to over add nutrients and realize what you are actually adding to your soil. Just because it is ‘natural’ does not mean it could have negative impacts.

11/12/2013 6:44:42 PM

Torrance, Ca.

Wow, thanks for that Matt!

11/12/2013 7:07:34 PM

Millville, UT

I will be combing through all this information, this is the stuff I need to study. I do know salt can be a very big problem here in Utah. We get virtually no rain during most of the growing season. From mid May through the end of August Cache Valley received less than a ¼ inch this year, so salt will tend to build up through the summer just from our very hard irrigation water. The only time I would ever add manure to my patch would be in the fall and hope the snow melt leaches the salt out. I will be doing my soil test in the spring and hope the snow has done its job.

11/15/2013 5:14:58 PM

Anamosa, IA [email protected]

I'm not worried about the salt in the manure that I get. It comes from a small farm, and is well composted outside. It is turned at least twice per year and has 3 to 5 years of aging. With normal rains I think that most of the salt gets leached out. At least me soil tests don't show a salt problem. Also the cows have access to the pasture or open lot, so there isn't a lot of urine in the manure. It is the urine that contributes a lot of salt to manure. I would hesitate to use manure from a deep bedded confinement where all of the urine goes into the manure and bedding.

11/15/2013 9:40:29 PM

Connecticut

cachekin- Out of curiosity, are you under water regulations in your area? I know some growers in your region have water application limits to try and reduce the drainage of the underground aquifer.

Iowegian- Having natural rain hit the manure stack will help leach some of the salt, but with it nutrients will also be lost. Urine does contribute to the salt content, and where there is manure there is also urine. Also, only turning it twice a year is not going to allow for the greatest aeration to occur. Also the carbon to nitrogen ratio plays a role in the speed of breakdown. There are many good articles, but this one has most of the basics...

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=15&ved=0CEcQFjAEOAo&url=http%3A%2F%2Fextension.oregonstate.edu%2Flincoln%2Fsites%2Fdefault%2Ffiles%2Fdocuments%2FProcesses_in_Compost_Making.pdf&ei=K4ONUrWPBonVsgbEzIFg&usg=AFQjCNGwll7yXTNou8Fj_BHz4Qq6MASJAQ&bvm=bv.56987063,d.Yms

11/20/2013 10:55:50 PM

Millville, UT

For my patch I use culinary water but it is very hard water. We haven’t been restricted but it can get very expensive if your usage gets over a certain level. To save I try to water my yard with irrigation ditch water when I can. For my patch I used the Thad Starr sprinkler set up and by the end of the summer all my sprinkler heads were white. I'm soaking them in vinegar before next year. Most of the composted manure for purchase around here comes from feed lots and there is a lot of urine in it. The local university here cautions against using too much of the manure for this reason. After reading your post I know I will be looking to use the KCa instead of the KCl, but I will be looking at my soil test really closely.

11/21/2013 1:29:00 PM