# phosphorus instead of nitrogen for coastal renovation



## charlesmontgomery (Jun 4, 2011)

I read somewhere but now can't find it that phosphorus was more effective in renovation coastal bermuda than nitrogen. I have a field that the drought hurt pretty bad and want to know if some phosphorus would help. I fertilized the field about 6 1/2 weeks ago with 400 lbs/a of 29-14-0 (I don't apply K because the cows graze the field the rest of the year and reapply the K themselves). This field has spent most of the time just sitting there. My other fields were cut two weeks ago and had a good yield. This field was overgrazed last fall so I guess it's spending it's energy building back roots and putting out new runners as it tries to recover from last years drought. The field in the best places is about 12" at 6 weeks tall. The rest varies from 3" to 8" to hardly no coastal at all around the tree lines. I just cut the field today and remembered reading that article about applying P instead of N for better results in renovating it. I do not plan on baling this field again. After it grows I will let the cows graze it. I am considering a 18-46-0 @ 200 lbs/A and then pray for rain.

I need to retest the soil as it has been two years but the last test called for 125-60-0 for a yield of 3 tons per acre.


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## Texasmark (Dec 20, 2011)

You may be on the right track. Since P is for flowers if flowering plants, and root development, then surely it would help an over grazed, drought stricken field recover.

I have read many places including Ag Us all over the country, that P applied with N makes the N all that much more available as compared to N alone.

I have a coastal pasture recovering from the severe drought we had here in N. TX. last year and I poured on the P...with the N. It is looking real nice considering. 
Course we have had some lovely and timely rains and that surely was part of the equation. Some places are lush and others coming along. I ran a pasture renovator over it spring of 2011 and the clay opened up along the cut lines of the renovator which I contoured to the hills here. When the rains came all that moisture went right into the sub soil. The cows have been grazing it all year at the rate of 2 acres per head and it is out producing them with me having mowed weeds 3 times. Course I trained them to eat weeds (spring flowering growth). Ha.

Best I can do.

Mark


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

Maybe So- Maybe No-- maybe a little something else.

Consider some potash also:

http://www.fluidjournal.org/article1.php
*"•High soil test K level in Warsaw's field helped maintain the plant growth regulator activity that keeps N uptake and use functioning at full capacity longer*
•*With lower K levels, the N uptake system begins to decline, and the photosynthetic enzyme, RuPD carboxylase (the primary N storage compound in corn leaves), begins to be broken down to supply the N needs of the developing grain*
•*This deterioration of the photosynthetic mechanism of lower leaves leads to less sugar supply to the roots, further decreasing the ability to absorb water and nutrients*
• *high soil K levels kept lower leaves healthy longer, leading to increased yield potential.*"
The better crops version
http://www.farmresearch.com/ppiweb/bcrops.nsf/$webindex/768E8C2C854019AE852568EF00543357/$file/00-1p20.pdf
*Potassium is "a poor man's irrigation", now it makes more sense beyond stomata explanations.*
It is possible to experience a yield drag from excessive levels of phosphate. 
This can be very evident if the P is not accompanied with enough K.

There is an almost guaranteed positive response to adding nitrogen.

Over grazing usually does damage from hoof compaction.

Now might be a good time to evaluate your stocking rate. You might find that the local Normal Stocking Rate is really a built in over stocking rate. Maybe go to one animal unit to 10 or 12 acres of "grass"? Roads, buildings, nor stream beds or water tanks count.

Consider including ammonium *Sulfate* in you fertilizer blend. Maybe a 4-1-4 +S blend?


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## charlesmontgomery (Jun 4, 2011)

When is the right time of year to apply P and K? Only early spring or any time?

Thanks


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## vhaby (Dec 30, 2009)

What are your soil test levels of P and K? What is the texture (sand? clay?) of your soil? What is your location???

On a sandy loam soil that is very low in P and K, I would apply all the P in the first application of fertilizer for bermudagrass regrowth. Also, at that time, apply one-half the recommended amount of K with the second half of the recommended amount of K being applied after the second cutting, assuming that you will be making three or four cuttings.

If the soil test indicates medium or high levels of P and K, any recommended P fertilizer can be applied with each successive N application between cuttings. Any K to be applied should be applied with each additional N application. On low-K soils, the rate of K to be applied for bermudagrass should equal the amount of N applied, or perhaps more K than N in order to maintain bermudagrass stand density.


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## charlesmontgomery (Jun 4, 2011)

vhaby said:


> What are your soil test levels of P and K? What is the texture (sand? clay?) of your soil? What is your location???
> 
> On a sandy loam soil that is very low in P and K, I would apply all the P in the first application of fertilizer for bermudagrass regrowth. Also, at that time, apply one-half the recommended amount of K with the second half of the recommended amount of K being applied after the second cutting, assuming that you will be making three or four cuttings.
> 
> If the soil test indicates medium or high levels of P and K, any recommended P fertilizer can be applied with each successive N application between cuttings. Any K to be applied should be applied with each additional N application. On low-K soils, the rate of K to be applied for bermudagrass should equal the amount of N applied, or perhaps more K than N in order to maintain bermudagrass stand density.


Soil test calls for 125-60-0. Soil is crockett loam and a little crosstell fine sandy loam. Has a high enough clay content that in last year's drought it had cracks that were over 6' deep and several inches wide. pH is 6. Phosphorus was 16 lbs/A, Potassium was 352 lbs per acre extractable nutrient. 4.8% organic matter. CEC is 19.6. The field has two sides with trees in the fence lines. These trees sucked all of the moisture from the coastal during last summer's drought and not much coastal remains from the tree line to as far as 40-50' out from the fence rows.

One problem is that different folks (educated folks from different universities, extension agents, etc) have different opinions on whether or not the K in my soils is usable by the plants. Some say that it is not, others say that it is. I don't mind putting out the K, but it would be nice to know for sure if i really need it.

Thanks


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## vhaby (Dec 30, 2009)

Charles, we still don't know where you are located. Growing Coastal bermudagrass indicates that you are located somewhere in the southern states, but with 6-ft deep cracks during last year's drought you likely are located in Texas. Be careful regarding those "several inch wide cracks." A calf could break a leg if it stepped into one of these while running across the meadow.

A soil designated as loam can range from 7 to 27% clay, 24 to 52% sand, and 28 to 50% silt. With a CEC of 19+ and 352 lb K/acre, (lbs or ppm?, usually a soil test lists K as ppm) your Crockett loam must be in the high end of the clay percentage. You are so fortunate to have soil with such high organic matter.

Regarding the K soil test, especially if the testing lab was using the extractant called Mehlich III, university and private testing labs have very little if any research data to support potassium recommendations based on that test. Most extractants will remove soluble and exchangeable K from soils. Both forms are considered available for plant uptake. However, most testing laboratories dry the submitted soil samples before analyzing them. If they use heat to dry the soils, certain types of clay will release K that is trapped between clay plates that would not normally be available for plant uptake. This can give a higher test result for plant avaliable soil K. If these labs would analyze field moist soil samples for K, their test results would be more valid. Since they don't do this, there is uncertainty in the test results for plant available K.

Certainly, some of the extracted K is available for plant uptake, but without supporting research to verify crop response to potash application at varying soil test K levels, it is no wonder there is confusion among university scientists and extension agents regarding plant availability of extracted soil K. There simply is little to no support funding these days for soil scientists to do soil fertility research in support of the soil tests that we depend on for fertilizer recommendations.

With that said, I would suggest that you consider applying some potash for your Coastal bermudagrass. Potash (K2O, or muriate of potash) actually is potassium chloride. Our research on Tifton 85 bermudagrass at Texas A&M AgriLife Research-Overton, showed that Tifton 85 responded not only to potassium but also to the chloride in the potash. With your 352 lb/acre K soil test you probably could get by for a few years without applying potassium but eventually your bermudagrass stand will begin to decline (become less dense.) Potassium also helps plants do better during dry periods because it helps the guard cells around stomates in leaves (microscopic holes) to regulate the size of these holes to control transpiration (water loss.) How much potash to apply is a good question. On acid sandy Coastal Plain soils, my recommendation is to apply as much potassium as nitrogen, but your soils have more clay, a higher CEC, and more extractable soil K so you may need to apply less potash.

You might want to read some of the posts by Hay Wilson who has a much different philosophy about K application on his Blackland soils.

At 16 lb of P per acre, your soil certainly needs additional phosphorus. The recommendation to apply 60 lb of phosphate per acre seems about right based on this test result. The Mehlich III phosphorus soil test is better correlated with crop response to applied P than it is to K. With this low P level, you should apply all the fertilizer P at one time for the first cutting.


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## charlesmontgomery (Jun 4, 2011)

vhaby said:


> Charles, we still don't know where you are located. Growing Coastal bermudagrass indicates that you are located somewhere in the southern states, but with 6-ft deep cracks during last year's drought you likely are located in Texas. Be careful regarding those "several inch wide cracks." A calf could break a leg if it stepped into one of these while running across the meadow.
> 
> A soil designated as loam can range from 7 to 27% clay, 24 to 52% sand, and 28 to 50% silt. With a CEC of 19+ and 352 lb K/acre, (lbs or ppm?, usually a soil test lists K as ppm) your Crockett loam must be in the high end of the clay percentage. You are so fortunate to have soil with such high organic matter.
> 
> ...


Thanks

I am in Texas. The K is 352 lbs/Acre Extractable Nutrient according to the soil test. Servi-Tech is the lab and they use Mehlich 3 and ICP extractant (whatever the heck that is) for P, K, Ca, Mg and Na. This field is normally used for grazing but for the last 3 or 4 years I have taken one cutting of hay off of it because of the dry weather. I have to mow off the Rescue grass and other winter grasses off in late May each year, then I fertilize it and cut it for hay about 4 1/2 to 5 weeks later.

On another hay meadow I am in my second year of applying Roundup before the coastal greens up to avoid the expense of mowing and to clean up the first cutting of coastal. It is helping but the application date is tricky. Too early and the winter grasses will come back out again. Too late and I can damage my coastal.


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## Texasmark (Dec 20, 2011)

hay wilson in TX said:


> Maybe So- Maybe No-- maybe a little something else.
> 
> Consider some potash also:
> 
> ...


Mr. Wilson,

Along these lines, I have converted to Sulfates rather than Nitrates for my fertilizer up here 30 miles south of the river in Houston Black Clay. Even though I have had the controversy over years about the K in the soil and the available K, I add K to the ration anyway.

Question is on the Sulphur. I was looking at some 21-0-0-24 the other day to get some extra N and the Sulphur content seemed excessive.

Do you know what the effects of too much are?

Thanks,
Mark

I have a hard bound copy of the Ag research conducted at Renner in the late '60's for most of my forage advice like one would do for a thesis. I really don't care for their format as they conduct experiments and give you the results. I like a pro active approach better, but it's better than nothing. So, obviously the K gets kicked around pretty good. Not much advise on S.


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## charlesmontgomery (Jun 4, 2011)

All I know about it is that ammonium sulfate is said to require 3 times more lime to correct pH than ammonium nitrate- and lime, transport charges and application ain't cheap


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## Texasmark (Dec 20, 2011)

charlesmontgomery said:


> All I know about it is that ammonium sulfate is said to require 3 times more lime to correct pH than ammonium nitrate- and lime, transport charges and application ain't cheap


 I'm in black clay and have a slightly acid ph.

Mark


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

*Potassium was 352 lbs per acre extractable nutrient. 4.8% organic matter. CEC is 19.6*

The lab really reads the soil test in PPM and converts it to lbs/A. So 352/2=176 ppm. Now is that 176 ppm of K2O or K. I assume they mean K2O so devide that by 1.2 = 147 ppm K. So in normal soil (dirt) we want 140 to 160 ppm K. So you look ok, Except with your CEC you probably need to multiply your 20 CEC by 9.5 and 12.5 for a desired 190 ppm to 250 ppm K.

Your lab should have a soil testing book with a chart on what you want for each CEC value to have an ideal level of K, Mg, Ca, &c.

Some of the soils around Waco are close to nuetral in pH and their clay is not as tricky as they are in Bell & Williamson, . This is not a universal observation for the Waco area as where they are working on I-35 there is a lot of lime material near the surface. There are clay soils (dirt) that tends to slip when wet rather than swell as it does in Bell County.

Good night, it is past my bed time.


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