# CONSEQUENCES OF EXCESS SOIL PHOSPHORUS BUILDUP



## vhaby (Dec 30, 2009)

Adequate soil phosphorus (P) may be defined as the soil test level at which no additional yield response is obtained when P is applied. Soil P levels above this point might be considered excessive by some, and some states environmental agencies have set 300 ppm soil test P as the maximum allowable level. This level is attained by repeated applications of broiler litter from broiler house cleanout applied on limited acreage, or by excessive application of other manure slurries such as laying hen effluent, hog manure, or dairy effluent.

Excess soil P can have a negative effect on the environment when rainfall runoff carries soil clay particles with attached P or soluble P off the soil surface and into ponds. streams, and lakes where the P level that had been relatively low now is raised to a more adequate level for the growth of algae (algae bloom) and other water loving plants. Eventually these plants die and the decomposition process requires oxygen that is removed from the water (eutrophication). The lowered oxygen content in the water may cause fish kills.

High to excess P levels in soils normally have little consequence to forage or row crop production except in some cases where soil zinc may be limiting and a zinc deficiency-like symptom occurs on the leaves.

Another consequence of excess soil P is the lightening of one's billfold. It is not impossible, but is highly unlikely that a crop producer can afford to apply sufficient fertilizer P to cause an excess level of soil P except over many years of applying more fertilizer P than crops need.


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## terraceridge (Jul 21, 2011)

Thank you very much. Normally I associate nitrogen with fish kills, but I didn't know phosphorous could contribute, too. I asked the question because there are some hay farmers around here who fertilize with chicken litter exclusively. It seems like, in order to get enough N, they are over applying P. Is that correct?
Also, what is the usual nutrient analysis for chicken litter?


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## vhaby (Dec 30, 2009)

terraceridge said:


> Thank you very much. Normally I associate nitrogen with fish kills, but I didn't know phosphorous could contribute, too. I asked the question because there are some hay farmers around here who fertilize with chicken litter exclusively. It seems like, in order to get enough N, they are over applying P. Is that correct?
> Also, what is the usual nutrient analysis for chicken litter?


Not all of the total N in broiler litter is available for plant uptake in the year of application. If one assumes that possibly 60% of the N in broiler litter might be available, and the litter contains 60 lb of N/ton and the crop needs 120 lb of N for a cutting, broiler litter would be applied at a rate approximating 3.5 tons/ac to satisfy the current crop needs for N. This rate of broiler litter would apply about the same amount of phosphorus. Over years of broiler litter application at this rate, the P level in the soil will have increased beyond the needs of the crop. Broiler litter should be applied to satisfy the P needs of the crop and commercial fertilizer needs to be added to satisfy the N and K needs of the crop.

One multiple sample average of the nutrient content of broiler litter in pounds:

________________Average-----Range
Nitrogen, N----------------62--------34- 96
Phosphorus, P2O5------59--------22-142
Potassium, K2O----------40-------13 - 99
Calcium, Ca---------------35-------13- 98
Magnesium, Mg-----------8--------3- 34
Sulfur, S--------------------6-------0.2- 13


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## darwood (Jun 7, 2010)

Are areas in TX having issues with P buildup in soils? Are neighboring states suing TX for P runoff into other city water supplies? Do TX producers have to have a nutrient management farm plan? Are TX producers limited on the amount of P fertilizer that can be applied to their property? Are there any designated nutrient surplus areas identified in TX? The reason I ask all these questions is because in AR all of the above questions can be answered with a yes, and believe me, it is a huge PITA dealing with all the regs.


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## Vol (Jul 5, 2009)

darwood said:


> Are areas in TX having issues with P buildup in soils? Are neighboring states suing TX for P runoff into other city water supplies? Do TX producers have to have a nutrient management farm plan? Are TX producers limited on the amount of P fertilizer that can be applied to their property? Are there any designated nutrient surplus areas identified in TX? The reason I ask all these questions is because in AR all of the above questions can be answered with a yes, and believe me, it is a huge PITA dealing with all the regs.


Darwood, which "neighboring" state(s) is suing AR over P runoff ??

Regards, Mike


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## hay wilson in TX (Jan 28, 2009)

Darwood has not seen the depth of knowledge shared by our good friend vhaby, He is truly a flowing spring of fertility &c information.
The last time I checked he map Texas puts very little water into the rivers and lakes of other states. We get salty water down the Pecos from NM, which flows into the Rio Grand which borders Mexico but does not go into Mexico. The Red River in the Pan Handle flows along the Oklahoma territory. The Red River is mostly in OK even though it is the border. Then it goes into Louisiana. Some tributaries of the Sabine start in Texas but again mostly the river is the State Boundary. Mostly our rivers flow directly into the Gulf of Mexico.
So to answer Darwood's question, *NO*. There are no downstream states to take Texas to court for excessive phosphate in the waters.
For the uninitiated it is phosphate that supports a algae bloom that stinks up the waters and kills fish through oxygen starvation.


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