P R O C E E D I N G S — F O U R T H G E N E R A L M E E T I N G 37 P e n e t r a t i o n
P e n e t r a t i o n varies according to the t y p e a n d condition of the soil. In open sandy soils it is obviously much greater t h a n in close- packed, alkaline, clay soils. In most soils the phosphorus is r e t a i n e d in the first foot, but in some cases it is found to p e n e t r a t e as much as 20 to 30 inches.
Dispersion
Because of better penetration of the liquid fertilizer t h e r e is al- most complete dispersion of the added phosphorus t h r o u g h o u t the root zone. As the very dilute phosphoric acid flows into the soil it is fixed by the bases present. In the past, fixation has been considered a very serious change occurring to phosphate fertilizers, b u t more recent ob- servations in which we see the effect of one application of phosphate continuing from 2 to 4 years indicates t h a t the losses are not as much as was formerly believed. In fact fixation is a very i m p o r t a n t provi- sion of n a t u r e to prevent losses of the valuable element, phosphorus.
W i t h any form of phosphorus fixation m u s t occur, a n d we m u s t rely on the plant to give off acid in the form of carbon dioxide from its roots to redissolve the solid phosphates. In the case of liquid fer- tilizers the dilution is so great t h a t phosphorus may be taken up by the growing plant without going through the solid stage. However, the greater p a r t of the phosphorus used in irrigation water is precipi- tated in a finely divided state throughout the entire root zone where it will be subject to the action of carbon dioxide from all the roots of the plant, rather than only a few roots as when solid fertilizer is ap- plied.
The practice of feeding crops by side dressing as they need p l a n t food has been widely used with v a r y i n g success. W h e n solid phos- phates are placed near enough to a growing p l a n t to be of value there is usually p r u n i n g of new roots. Often this i n j u r y offsets any advan- tage gained by the added p l a n t food. W i t h liquid fertilizer the new material moves in and a r o u n d the roots with the irrigation water with- out disturbing the p l a n t at all. Also the new food material is so dilute that no root has to grow through or combat a concentrated zone of fer- tilizer material as when the material is applied in the solid state with a side dressing tool.
Conversion of N a t u r a l P h o s p h a t e s
W h e n phosphoric acid moves into the soil it is fixed t e m p o r a r i l y as described above. This change is brought about by the bases in t h e soil acting with the phosphoric acid. A portion of these bases a r e n a t - u r a l phosphates resembling r a w rock phosphate which are converted by the acid to more soluble forms of phosphorus. The effect is the same
38 AMERICAN SOCIETY S U G A R - B E E T TECHNOLOGISTS
as t h a t carried out in the production of treble superphosphate in the m a n u f a c t u r i n g plant where phosphoric acid is added to raw rock phos- phate.
Saving in Cost of Application
The saving in cost of application of liquid fertilizers over the ap- plication of solid fertilizers is considerable. I r r i g a t i o n must be car- ried on in a n y event, and after the d r u m s are placed over the ditch it is only a small effort to regulate the flow of acid. No drills or expen- sive equipment are required to a p p l y liquid fertilizer; only a small de- vice to go into the opening of the d r u m s to regulate the flow of acid.
This device costs about 25 cents.
Exact Timing of Fertilizer Application
Another outstanding advantage of liquid fertilizer is t h a t it may be applied to a crop at a n y stage of development. As formerly stated a growing crop can use a portion of the liquid fertilizer at once, and the remainder is placed in a very advantageous position about the roots. Effects of the fertilizer can begin immediately, whereas with solid fertilizers there is delayed action. W i t h some crops, and especial- ly with sugar beets, it is important t h a t the p l a n t s have their phos- phate early in life. To meet this situation a system known as pre-irri- gation is p r a c t i c e d ; t h a t is, the laud is irrigated and phosphoric acid applied before planting. In some localities pre-irrigation is practical, or in other districts where beets are irrigated up the use of liquid fer- tilizer will fit into the plan of operation. Phosphoric acid applied ear- ly to beets has the best o p p o r t u n i t y to aid the crop.
Evidence is accumulating which indicates t h a t seeds germinate better when crops are i r r i g a t e d up with water containing liquid phos- phoric acid. Continued observations are being made on this effect of liquid fertilizer.
In Practice
In the field it has been difficult to get actual comparisons of solid versus liquid phosphates. A serious effort is now being made to get these data. Recently the writers conferred with users of liquid phos- phoric acid in the Salinas a n d I m p e r i a l Valleys of California a n d the Salt River a n d Y u m a Valleys of Arizona. The p r e v a i l i n g opinion is much in favor of liquid phosphoric acid. Its use on crops in these areas has reached well beyond the experimental stage. At present the alfalfa crop represents the greatest acreage fertilized with liquid phos- phate.
P R O C E E D I N G S — F O U R T H G E N E R A L M E E T I N G 39 On beets some measurements of the results of the use of phos-
phoric acid have been made. On the Tsabell-IIartner farm at P h o e n i x an increase of over 800 pounds of beet seed, per acre was p r o d u c e d with an application of 200 pounds of phosphoric acid.
Tests conducted in the Delta region of Utah on alfalfa last sea- son gave outstanding results. Also in Montana comparative tests with phosphoric acid versus treble superphosphate were conducted on potatoes at the Donick ranch at Deerlodge. The phosphoric acid gave an increased yield of 27 sacks per aere as against 13 sacks from the treble superphosphate. With trees the actual results of a given fer- tilizer must be observed over a long period of time a n d because t h e r e are usually various combinations of fertilizers used it is difficult to evaluate the results. On the F r a n k Cihak place at El Centro, Calif., a grapefruit orchard produced over 27 tons of fruit following a 3-year treatment with phosphoric acid a n d other fertilizers. This is said to be one of the highest production records in the district.
P e r h a p s the best results from the use of phosphoric acid has been on vegetable crops and alfalfa. On the whole, the use of phosphoric acid represents a step forward with fertilizers to increase a g r i c u l t u r a l production.