# Knifing liquid NPK; opinions



## Cen-Tex (Jan 13, 2015)

I'm looking to maxamize my coastal fertilizer dollars and I hope some of you might offer me some insite. My place is in Comanche county Tx and is some of the most wore out blow sand (thanks to peanuts & poor farming practices) in the state. I am spending too many dollars each summer and not getting enough tonnage to sustain the expense. I do soil samples once or twice a year and follow the reccomdations as much as my bank account will allow.

I read a lot on another website about side dressing this and that and it got me to thinking I could do the same thing in my grass. I bought a DMI anhydrous applicator at a auction last summer with the intentions of converting it to apply liquid. I am going to put a ground drive pump on it, but I'm a little unsure which model john blue to buy. How many GPA would I be applying? Are the rates the same as spraying broadcast? This rig has 11 shanks on 15" spacing.


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## endrow (Dec 15, 2011)

what type of a liquid NPK blend are you referring to


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## aawhite (Jan 16, 2012)

Would this create a streaking problem? Not sure that shanks at 15" will give you real good coverage. They are designed to feed a targeted root zone. Slide them closer and add more shanks?


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## Mike120 (May 4, 2009)

Our place where I grew up was outside of Devine, TX. I hate to argue with you about who has the worse blow sand or soil in the State. Thankfully, I've got a decent sandy loam now.

I looked at the same approach a number of years ago but I was going to put injection knives on my pasture renovator just to experiment with the approach. I couldn't find a cheap applicator at any of the auctions and buying the coulter mounted knife assemblies to build one was just too expensive. However, the more I read, the more I talked to people and the more I messed with the concept, I came to the conclusion that it wasn't worth the effort.....I still like the theory though 'cause I like to build things.

I'm fortunate that I've got access to a liquid dealer (Simplot - bought the old Texas Liquid bunch) and a granular dealer within easy driving distance. Both have applicators I can rent and both can custom apply it. The liquid applicators use the little 3-port drench nozzles on the boom that give you pretty close spacing on the ground. It will burn the grass unless you get rain on it pretty quick, but the grass recovers and it does fine. Liquid fertilizer is a little cheaper and you have a lot more flexibility in your blending and addition of micro-nutrients, etc. But, it's not that much cheaper and more trouble than I think it's worth. I've come to the conclusion that there would be little difference between dribbling it on the surface or dribbling it 8-9" below the surface other than an expensive John Blue pump, more HP to pull the rig, and more ground disturbance. I still use liquid once in a while, but for me granular is just a lot easier and I get a better distribution.

With granular you are pretty much dependent on rain/moisture to transport the fertilizer to the roots. The same goes for liquid; by injecting you're just giving it a head start. Side-dressing is great for seeds and young row plants because the roots will grow into the fertilizer or you are putting it close to a shallow root zone. An established Bermuda field typically has deep roots. My view is that a productive hay field needs regular applications of fertilizer to replace the nutrients you are removing from the hay and to maintain the fertility of the deeper soils where a lot of the roots are. Those deep roots are what sustain the plants during our all-too-frequent droughts. It takes a while to get that "deep fertility" but I still got three cuttings during the 2011 drought instead of my usual six, so it makes sense to me to keep throwing fertilizer on the fields. My theories may be all wrong, but.......

I personally think that 15" is too wide but I was never able to really find any information that would allow me to mathematically model the fertilizer penetration/distribution in the soil. With liquid in a hay field you are either dependent on the liquid distributing like a triangle as it penetrates to get to all of the roots or, all of the roots being able to access the band of fertilizer you are applying. With granular I can rely on random surface distribution for coverage. This is the curse of an engineering education.....I think too damn much. Good luck, I'm really curious how it works for you!


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## rjmoses (Apr 4, 2010)

I've experimented with knifing anhydrous on orchard grass three years now. Soil is gray over clay and I've had mixed results.

AA on Potomac OG two years good results for first cutting, not as good on Tekapo third year. Fields were ridged and a little rough in some spots where there was compaction or insufficient moisture such that the knives pulled up clumps of soil. Tekapo field was rough enough that I ran the cultimulcher over it. But I did like the way the soil was opened up.

AA didn't seem to migrate very fast, but the retention was high. Biggest issue with limited experience seems to be get the nitrogen at the right depth so the roots can reach it on a timely basis. OG has a shallower root system, so I don't think I was getting the full punch of the N from AA.

I would be concerned about leaching and other losses with AA in sandier soils.

This year, I am top dressing all of my nitrogen, although I am considering knifing some 28 on a pasture as a test.

I have not knifed P or K; top dress those.

Just my thoughts.

Ralph


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## swmnhay (Jun 13, 2008)

I tried some AA on some mixed grass on 30" centers.I ended up with green streaks about 6" wide.I was applying about 6" deep in heavy soil.I did maybe 8 acres next to a field I was applying for corn.I wouldn't do it again.Have much better luck with Urea.


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## Cen-Tex (Jan 13, 2015)

I have a neighbor up the road that hired phos knifed in last summer. The guy had a KBH drag rig that was on 36" rows primarily used for side dressing cotton. They ended up going over the field in a checkerboard pattern and man did they make the grass. I was told however that they had to come back later in the summer and do it again because the grass had used it all up. This field has similar if not the exact type of soil mine has, under irrigation also. I don't have much money tied up in my rig, I could still sell it or use it as a renovator.

My gut tells me this will work.


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## somedevildawg (Jun 20, 2011)

If I had irrigation, granular would be my choice, just more expensive.....I don't thnk you can put enuf K through liquid practically. If I have to spin K might as well spin it all. I do use the Hayking once a year when first topdressing goes on....


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## vhaby (Dec 30, 2009)

In the mid-1980's, I designed and we built an experimental fluid fertilizer applicator for use on Coastal bermudagrass in small-plot research studies. This applicator had shanks preceded by a rolling coulter and attached to a 4" x 4" steel bar the width of the applicator. Also attached to this bar was a series of spray booms from which we could spray or dribble band the liquid fertilizer. Spray nozzles were set 20-inches apart and dribble -banding nozzles using orifice plates were set in gangs so that we could dribble fluid fertilizer at 7, 14, 21, and 28-inches apart. The fluid application was powered by CO2 in a 5-gallon pressurized beverage container like the ones used to dispense soft drinks. The fluid fertilizers were applied from similar beverage containers using the CO2. This unit was calibrated similar to calibrating a pesticide sprayer.

Using this applicator, we evaluated spray broadcast, surface banded, and attempted shanked-in application of 32-0-0. When spray broadcast, the bermudagrass initially became chlorotic as Mike mentioned. Also, surface dribble banding initially caused chlorosis. In both cases, the grass rapidly (within about a week) grew out of the chlorosis. In surface and attempted dribble banding, the bermudagrass in the area over the band initially grew away (exceeded) from the grass between the bands, but by harvest time, 28 or so days later, there was no observable difference in grass height across the bands. The same amount of 32-0-0 was applied in plots wherein the bands were 7-, 14-, 21- or 28-inches apart. At harvest, bermudagrass yielded the same regardless of width between the bands. Bermudagrass grows by rhizomes (below surface runners) and stolons (above ground runners). These runners grew across the banded nitrogen materials, put down roots into the applied fertilizer, and continued to grow across the distance between the bands, all the while feeding the new growth from the bands.

Above, I mentioned that we attempted to shank-in the 32-0-0. As heavy as our applicator was and with about seven??? shanks across the applicator, we could not get the coulters and shanks to cut through the bermudagrass sod to shank-in the 32-0-0 (UAN), so the shanked treatments were similar to the dribble-banded material. I could stand on one of these coulter shanks and it might cut a little into the sod. The applicator was heavy, but not heavy enough. Soil on two sites was a loamy sand and a sandy loam.

We could blend N, P, K, and whatever other nutrients we wanted to apply in this fluid material, similar to using granular fertilizers, although the concentrations were more dilute in order to prevent salting out of the blend.

The greatest concern with using fluid fertilizers is ammonia volatilization from the urea component in the 32-0-0 that is about half ammonium nitrate and half urea plus water. Sprayed or surface dribble banded UAN will volatilize ammonia causing loss of nitrogen applied to acid soils, limed acid soils, and naturally alkaline (pH above 7) soils. The percentage loss will vary, but this loss from surface application of UAN and blends will be greater than any volatilization loss from use of prilled ammonium nitrate nitrogen fertilizer, unless about 0.4 inch of rain is applied within 24 or so hours after application.

The urease enzyme that causes the urea material to take on water (hydrolyze) and convert to ammonium hydroxide is present in soil, on growing vegetation, and on surface plant residue. The ammonium hydroxide raises the soil pH and is caused to convert to ammonia and water, thereby allowing loss of ammonia as a gas.


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## endrow (Dec 15, 2011)

In our area I know there was a time people tried to come up with those hot mixes of npk so that everything could be applied in liquid with just one pass . Many have gone back to applying there nitrogen in a liquid and their p&k dry..


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## somedevildawg (Jun 20, 2011)

That's what I do ^^^^ cost is a bit more but in the entire scheme of things, I think it's a payoff...


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