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osunpk

osunpk

Since 2008 I have served as the Precision Nutrient Management Extension Specialist for Oklahoma State University. I work in Wheat, Corn, Sorghum, Cotton, Soybean, Canola, Sweet Sorghum, Sesame, Pasture/Hay. My work focuses on providing information and tools to producers that will lead to improved nutrient management practices and increased profitability of Oklahoma production agriculture

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Banding P as a band-aid for soil acidity, not so cheap now.

Whoi Cho, PhD student Ag Economics advised by Dr. Wade Brorsen
Raedan Sharry, PhD Student Soil Science advised by Dr. Brian Arnall
Brian Arnall, Precision Nutrient Management Extension.

In 2014 I wrote the blog Banding P as a Band-Aid for low-pH soils. Banding phosphate to alleviate soil acidity has been a long practiced approach in the southern Great Plains. The blog that follows is a summary of a recent publication that re-evaluated this practices economic viability.

Many Oklahoma wheat fields are impacted by soil acidity and the associated aluminum (Al) toxicity that comes with the low soil pH. The increased availability of the toxic AL3+ leads to reduced grain and forage yields by impacting the ability of the plant to reach important nutrients and moisture by inhibiting root growth. Aluminum can also tie up phosphorus in the soil, further intensifying the negative effects of soil acidity. More on the causes and implication of soil acidity can be found in factsheet PSS-2239 or here (https://extension.okstate.edu/fact-sheets/cause-and-effects-of-soil-acidity.html). The acidification of many of Oklahoma’s fields has left producers with important choices on how to best manage their fields to maximize profit.

Wheat Trial, Cimarron Valley Research Station

Two specific management strategies are widely utilized in Oklahoma to counter the negative impacts of soil acidification: Lime application and banding phosphorus (P) fertilizer with seed. While banding P with seed ties up Al allowing the crop to grow, this effect is only temporary, and application will be required every year. The effects of liming are longer lasting and corrects soil acidity instead of just relieving Al toxicity. Historically banding P has been a popular alternative to liming largely due to the much lower initial cost of application. However, as P fertilizers continue to increase in cost the choice between banding P and liming needed to be reconsidered.

A recent study by Cho et al.,2020 compared the profitability of liming versus banding P in a continuous wheat system considering the impacts that lime cost, wheat price and yield goal has on the comparison. This work compared the net present value (NPV) of lime and banded P.  The study considered yield goal level (40 and 60 bu/ac) as well as the price of P2O5 fertilizer and Ag Lime. The price of P2O5 used in this study was $0.43 lb-1 while lime price was dictated by distance from quarry, close to quarry being approximately $43 ton-1  and far being $81 ton-1. For all intents and purposes these lime values are equivalent to total lime cost including application. Wheat prices utilized in the study were $5.10 bu-1  and $7.91 bu-1. It is important to note that baseline yield level was not considered sustainable under banded P management in this analysis. This resulted in a decrease in yield of approximately 3.2 bu ac-1  per year. This is attributable to the expected continued decline in pH when banding P is the management technique of choice.

The analysis in this work showed that lime application is cost prohibitive in the short term (1 year) when compared with banding P regardless of lime cost, yield goal level, and wheat value (within the scope of this study). This same result can be seen over a two-year span when yield is at the lower level (40 bu ac-1). While in the short-term banding P was shown to be a viable alternative to liming, as producers are able to control ground longer lime application becomes the more appealing option, especially when producers can plan for more than 3 years of future production. In fact, under no set of circumstances did banding P provide greater economic return than liming regardless of crop value, yield, or liming cost when more than 3 years of production were considered and only under one scenario did banded P provide a higher NPV in a 3-year planning horizon.

While historically banding P was a profitable alternative to lime application for many wheat producers the situation has likely drastically changed. At the time of writing this blog (09/17/2021) Diammonium Phosphate (DAP) at the Two Rivers Cooperative was priced at $0.78 lb-1. of P2O5. This is a drastic increase in P cost over the last year or so since Cho et al. was published in 2020. With P fertilizer prices remaining high it will be important for producers to continue to consider the value of liming compared to banded P. This is particularly crucial for those producers who can make plans over a longer time frame, especially those more than 3 years.

Addendum: As fertilizer prices have continued to rise a quick analysis utilizing the $0.78 lb-1 of P2O5was completed to consider the higher P fertilizer cost. Under this analysis an estimated decrease in NPV of approximately $38 an acre for P banding occurred. When considering this change in NPV, lime application becomes the more profitable option for alleviation of soil acidity symptoms even in the short term (assuming lime price values are equivalent to the previous analysis). This underlines the fact that it is imperative to consider the impact on profitability of the liming vs. banding P decision in the current economic climate for agricultural inputs.

Link to the Open Access Peer Reviewed publication “Banding of phosphorus as an alternative to lime for wheat in acid soil” https://doi.org/10.1002/agg2.20071

DAP in short supply? Revisiting, DAP vs MAP, Source may matter!

From mid August through October, fertilizer applicators and grain drills are running across the southern great plains wheat ground. Di-ammonium Phosphate (DAP 18-46-0) is maybe the most popular form of phosphorous (P) utilized in wheat production today. DAP delivers a high content of nitrogen (N) while efficiently binding the toxic aluminum (Al) ions low pH soils. However due to the flooding that occurred throughout the spring the Ports have been closed and DAP could be in short supply. I have heard that many companies and Co-ops have already sourced Mono-ammonium phosphate (MAP 11-52-0) to supplement the lack of DAP for our early planted wheat crop. With this happening, I wanted to share some points about the two sources. In a broadcast incorporated scenario I do not have much preference for one over the other. It is when producers are applying the fertilizer in-furrow or applying to alleviate Al toxicity that source can matter. As described in the post below, in a soil with a neutral pH DAP and MAP perform equally well. So in this scenario I give MAP a slight edge over DAP if the price is the same. I say this as you can run less material per acre with MAP and refill a little less often. Many worry about the drop in N delivered with MAP versus DAP but in my work I see that is the P in the starter that gives us a good response and not the N, which can be delivered with pre-plant or top-dress. However, DAP wins out in soils with a pH below 5.5. The original blog below shows the results when DAP and MAP are banded in acidic soils using the same rate of P per acre.  The reason we see this happen is that when MAP dissolves it forms a slightly acidic solution (approx 4.0) while DAP will dissolve to form a slightly basic solution (approx 7.5). In our work BOTH DAP and MAP increased yield above the check in acidic soils, which goes to show MAP is an affect tool for short term remediation of aluminium toxicity (Band P for Al toxicity Blog). However it might require more MAP per acre to reach the equivalent results. Because of what we saw when comparing the two sources at equivalent rates of P, I would recommend increasing the rate of P2O5 from 30 lbs per acre to 35 or 40. This would be going from 65 lbs of DAP to 67-77 lbs of MAP per acre.

So the take home would be as this wheat season takes off and you find that DAP is hard to locate and you A) Have overall neutral (5.5+) pH levels do not hesitate using MAP. Run the normal amount of material getting a few extra lbs of P or apply less material to get the same amount of phosphate. B) Have a acidic situation and are banding to alleviate aluminum toxicity use the same amount of material or a little bit more.  Keep in mind in acidic soils with a low soil test P level you have to apply enough phosphate to take care of the Al and enough to take care of the P deficiency. Note the results of the NPKS wheat response strip (NPKS BLOG)

Original Post Published July 18, 2016
DAP vs MAP, Source may matter!

Historically the two primary sources of phosphorus have had different homes in Oklahoma. In general terms MAP (11-52-0) sales was focused in Panhandle and  south west, while DAP (18-46-0) dominated the central plains.  Now I see the availability of MAP is increasing in central Oklahoma. For many this is great, with MAP more P can be applied with less material. which can over all reduce the cost per acre. There is a significant amount of good research that documents that source of phosphorus seldom matters. However this said, there is a fairly large subset of the area that needs to watch what they buy and where they apply it.

If you are operating under optimum soil conditions the research shows time and time again source does not matter especially for a starter.  In a recent study just completed by OSU multiple sources (dry, liquid, ortho, poly ect ect) of P were evaluated.  Regardless of source there was no significant difference in yield.  With the exception of the low pH site. The reason DAP was so predominate in central Ok, soil acidity.  See an older blog on Banding P in acidic soils.

Picture1

Figure 1. The cover of an extension brochure distributed in Oklahoma during the 1980s.

When DAP is applied, the soil solution pH surrounding the granule will be alkaline with a pH of 7.8-8.2. This is a two fold win on soil acidity aka aluminum (Al) toxicity.  The increase in pH around the prill reduces Al content and extends the life of P, and as the pH comes back down the P ties up Al and allows the plant to keep going. However, the initial pH around the MAP granule ranges from an acid pH of 3.5-4.2.  There is short term  pH change in the opposite direction of DAP, however the the Al right around the prill becomes more available and in theory ties up P even faster.

Below is a table showing the yield, relative to untreated check, of in-furrow DAP and MAP treatments in winter wheat.  The N401 location had a ph 6.1  while Perk (green) has a pH of 4.8.  At Perkins in the low pH, both forms of P significantly increased yield, almost 20 bushel on the average.  DAP however was 5 bushel per acre better than MAP. At the N40 site the yield difference between the two sources was 1 bushel.

MAPvDAP2

Relative yield winter wheat grain yield MAP and DAP both applied at equal rates of P (32 lbs P2O5 ac) when compared to a untreated check.

In general it can be said that in acid soils DAP will out preform MAP while in calcareous high pH soils MAP can out preform DAP. So regarding the earlier statement about the traditional sales area of MAP or DAP if you look at the soil pH of samples went into the Oklahoma State University Soil, Water, and Forage Analytical lab the distribution makes since.

State pH

Average soil pH of samples sent into OSU soil water forage analytical lab by county.

In the end game price point and accessibility drives the system.  In soils with adequate soil pH levels, from about 5.7 to around 7.0, get the source which is cheapest per lbs of nutrient delivered and easiest to work with. But if you are banding phosphorus in row with your wheat crop because you have soil acidity, DAP should be your primary source.

DAP vs MAP, Source may matter!

Historically the two primary sources of phosphorus have had different homes in Oklahoma. In general terms MAP (11-52-0) sales was focused in Panhandle and  south west, while DAP (18-46-0) dominated the central plains.  Now I see the availability of MAP is increasing in central Oklahoma. For many this is great, with MAP more P can be applied with less material. which can over all reduce the cost per acre. There is a significant amount of good research that documents that source of phosphorus seldom matters. However this said, there is a fairly large subset of the area that needs to watch what they buy and where they apply it.

If you are operating under optimum soil conditions the research shows time and time again source does not matter especially for a starter.  In a recent study just completed by OSU multiple sources (dry, liquid, ortho, poly ect ect) of P were evaluated.  Regardless of source there was no significant difference in yield.  With the exception of the low pH site. The reason DAP was so predominate in central Ok, soil acidity.  See an older blog on Banding P in acidic soils.

Picture1

Figure 1. The cover of an extension brochure distributed in Oklahoma during the 1980s.

When DAP is applied, the soil solution pH surrounding the granule will be alkaline with a pH of 7.8-8.2. This is a two fold win on soil acidity aka aluminum (Al) toxicity.  The increase in pH around the prill reduces Al content and extends the life of P, and as the pH comes back down the P ties up Al and allows the plant to keep going. However, the initial pH around the MAP granule ranges from an acid pH of 3.5-4.2.  There is short term  pH change in the opposite direction of DAP, however the the Al right around the prill becomes more available and in theory ties up P even faster.

Below is a table showing the yield, relative to untreated check, of in-furrow DAP and MAP treatments in winter wheat.  The N401 location had a ph 6.1  while Perk (green) has a pH of 4.8.  At Perkins in the low pH, both forms of P significantly increased yeild, almost 20 bushel on the average.  DAP however was 5 bushel per acre better than MAP. At the N40 site the yield difference between the two sources was 1 bushel.

MAPvDAP2

Relative yield winter wheat grain yield MAP and DAP both applied at equal rates of P (32 lbs P2O5 ac) when compared to a untreated check.

In general it can be said that in acid soils DAP will out preform MAP while in calcareous high pH soils MAP can out preform DAP. So regarding the earlier statement about the traditional sales area of MAP or DAP if you look at the soil pH of samples went into the Oklahoma State University Soil, Water, and Forage Analytical lab the distribution makes since.

State pH

Average soil pH of samples sent into OSU soil water forage analytical lab by county.

In the end game price point and accessibility drives the system.  In soils with adequate soil pH levels, from about 5.7 to around 7.0, get the source which is cheapest per lbs of nutrient delivered and easiest to work with. But if you are banding phosphorus in row with your wheat crop because you have soil acidity, DAP should be your primary source.