Effect of Nitrogenous and Potassic Salts with Phosphates on the Yield and Phosphorus,Nitrogen, Potassium, and Manganese Contents of Oats (Avena sativa L.)l

HERMAN A. HAMILTON2

ABSTRACTOn a neutral Grey Wooded soil receiving identical rates of

N, P, and K from different sources, there were significant dif-ferences (at the 5% level) in oat grain yields as well as strawyields. The choice of salts used influenced differently the yieldsof straw and those of grain. Whereas maximum grain yields wererealized with monocalcium phosphate monohydrate (MCP) +(NH4)2SO4 + KC1, maximum straw yields were obtained withMCP + (NH4)2SO4 + K2SO4. With diammonium phosphate(DP) as a source of N and P, there were no significant differencesin yield of grain or straw with the use of K2SO, or KC1, howeverN, P and K uptake by straw was invariably greater with K2SO4than with KC1. Despite the equivalence of N, P, and K applied,there were considerable differences in the nutrient compositionof grain and straw. With the exclusion of the control treatment,N in straw varied from 0.40 to 0.54%, P from 0.021 to 0.046%,K from 3.38 to 3.94%, and Mn from 9.4 to 63.4 ppm. In a com-parison of the nitrogenous sources associated with MCP + KC1,Mn uptake was in the order NH4C1>(NH4)2SO4>NH,NO3.While the symptoms of Mn deficiency were most pronounced forthe control treatment, these symptoms disappeared in all thefertilized treatments excepting MCP + KNO3.

IN THE USE OP phosphatic fertilizers, the most commonlyoccurring situation is one in which different potassic and

nitrogenous salts are also used to provide for the majornutrient requirements of plants. Common sources of N are(NH4)2S04, NH4N03, and NH4C1; and in the case of K, KOI,and K2SO4. The acidity which results from the nitrificationof ammonium fertilizers has been used to explain the greateruptake of P with ammonium rather than nitrate sources ofN (12). Viets (21) found the P content of corn leaves to begreater with (NH4)2S04 than with calcium nitrate as thesource of N. He concluded that the effect of acidity was not asimportant as those arising from the effects induced by the useof a monovalent cation as opposed to a divalent one. Rennieand Soper (16), after simulating the acid-forming effects ofammonium salts, concluded that acidifying effects could notaccount for the role of N in promoting the uptake of fertilizerP. Teater et al. (20) found no significant difference in yield orP uptake of maize with (NH4)2S04 or NH^Cl as nitrogenoussources, though soil acidity was greater with (NH4)2S04.

In connection with the interaction between P and K, Kurtz

et al. (9) observed that P concentration in soil solution wasdepressed by KOI, and Lehr and Wesemael (10) showed thatespecially at pH 7 P concentration in soil solution was lowerin the presence of KC1 and KNCH than with comparableamounts of K2S04. McGeorge and Breazeale (13) found thatboth KOI and K2S04 decreased the solubility of rock phos-phate and soil phosphate. Using K20 at the rate of 120 lb/acre, Younts and Musgrave (22, 23) found corn yields, Puptake, and N uptake to be significantly greater with K2S04than with KOI.

Increased soil acidity with the use of (NH4)2S04 andNH4NO3 has been suggested to be the cause of increaseduptake of Mn by plants (1,3), and the ability of superhosphateto promote the uptake of Mn has been ascribed also toresidual acidity (7, 18, 19). Because of the complex reactionsresulting on the application of fertilizer materials to soil, it isdifficult to accept that a single factor such as pH can explainthe increased uptake of Mn, though it could be a predominantfactor.

Bouldin and Sample (2) observed that the effect of associ-ated salts on the availability of concentrated superphosphatecould largely be explained on the basis of measured chemicaldifferences. It has also been shown (5) that when various saltswere allowed to react with soil, considerable differences in themovement and chemical characteristics of the soil solutionoccurred. It might therefore be expected that these differenceswould in turn be reflected in crop response or nutrientcomposition. It was the aim of the present investigation todetermine the relation between nitrogenous and potassic saltsin association with P as reflected in the yield and nutrientcomposition of oats.

MATERIALS AND METHODSAn imperfectly drained Grey Wooded clay soil at the Exper-

mental Farm, Kapuskasing, Ontario was sampled to a depthof 6 inches, air-dried, and made to pass a 0.5-inch mesh sieve.Subsamples from the bulk sample were crushed to pass a 2-mmsieve, and then retained for chemical analysis. Using the pro-cedures outlined by Peech et. al. (15) the soil was found to have apH of 7.0, organic matter 5.16% and an exchange capacity of31.2 meq/100 gm of soil. Sodium bicarbonate-soluble P asrecommended by Olsen et al. (14) was 6.0 ppm of soil, and phos-phoric acid-soluble Mn as outlined by Hoff and Mederski (8)was 12.3 ppm of soil.

A preliminary greenhouse experiment with oats showed that,with increasing rates of P as monocalcium phosphate monohy-drate (MCP) plus 166 pp2m of K as KC1, and 60 pp2m of Nas (NH4)2S04, there was a highly significant (P 0.01) differencein oat yields at 87 pp2m of P compared to 43.5 pp2m of P.Further, there was no significant (PO.05) difference between yield

240 SOIL SCI. SOC. AMEH. PBOC., VOL. 30, 1966

at 87 and 130.5 pp2m of P, respectively. On this basis, 65.2pp2m of P was chosen for use in this study, since changes in yieldmight be most sensitive in the range of 43.5 to 87 pp2m of P.

With N, P, and K at 60, 65.2, and 166 pp2m of soil, respec-tively, the following fertilizer materials shown below werethoroughly mixed in 10 Ib of soil placed in glazed 1-gallon pots:

1) No fertilizers (control)2) MCP + (NH4)2SO4 + KOI3) MCP + NH4NO3 + KOI4) MCP + NH4CL + KCL5) MCP + (NH4)2SO4 + K2S046) MCP + NH4C1 + K2SO47) MCP + KNO>38) DP + KC19) DP + K2SO4

All fertilizer materials were reagent grade pure. Garry oatswere seeded and after 1 week thinned to 25 plants per pot. Sup-plemental fluorescent lighting was used to ensure a 16-hour day-length period, and greenhouse temperature was maintained atapproximately 70F. Soil moisture was adjusted to the calculatedfield capacity with distilled water, and maintained by frequentweighing. After 70 days when oats had reached maturity, theabove-ground portion of the plants was harvested, separatedinto grain and straw, then dried at 70C for 8 hours. The driedmaterial was retained for the determination of N, P, K, and Mnas outlined by Greweling (Thomas Greweling, 1960. The chemicalanalysis of plant materials. Mimio Rep., Agronomy Dep., CornellUniversity).

RESULTSDespite the equivalence of N, P, and K in the sources used,

there were significant differences in grain yields as well as instraw yields (Table 1). With, treatments containing P, lowestgrain yields were obtained with KN03 and highest grainyields with (NH4)2S04 + KOI. Maximum straw yieldsresulted with the use of MCP + (NH4)2SO4 + K2S04. WithMCP as the source of P, and KOI as the K source, there wereno significant differences in grain or straw yields with the useof the different ammonium salts supplying N. However, whenK2S04 replaced KOI as the K source, grain yields weresignificantly greater with NH4C1 than with (NH4)2SO4 as theN source, and the reverse held true for straw yields. With DPas the source of P, there were no significant differences ingrain or straw yields with the use of KC1 or K2S04 as a sourceof K. Grain yields obtained with MCP + (NH4)2S04 + KOIor MCP + NH4C1 + K2S04 were significantly greater thanthose obtained with DP + K2S04. When K2S04 as the Ksource was used with DP, straw yields significantly exceededthose with MCP + NH4N03 + KOI; however with DP 4-KOI straw yields were significantly lower than in presenceof MCP + (NH4)2S04 + K2S04.

Chemical CompositionThe percentage of N in oat grain (Table 2) ranged from

1.92% in the case of the control and DP + KC1 treatments to2.20% for the MCP + (NH4)2S04 + KC1 treatment. WithMCP + KNOs or MCP + (NH4)2SO4 + K2SO4, the per-centage N was significantly lower than with MCP +(NH4)2S04 + KCL In the presence of MCP and (NH4)2S04,the percentage N was significantly greater with KC1 thanwith K2SO4, but in the presence of DP it was significantlygreater with K2S04 than with KC1.

The highest percentage of N in straw was obtained with the

Table 1—Average dry matter yield of oat grain and straw asinfluenced by different salts with monocalcium and

diammonium phosphates (mean of 4 replications)

Treatments Yield

Grain Straw

ControlMCP + (NH4)2S04 + KC1MCP + NH4NOs 4- KOIMCP + NH<C1 + KC1MCP + (NH4)2S04 + K;SO4MCP + NH4C1 + K2SO4MCP + KNOsDP + KC1DP + KsSO.

6.12d*10.57 a10.15ab10.21 ab9.37 be

10. 52 a8.78 e9.99ab9. 29 be

7.78d11.05 be9.89 c

10.36 be12. 50 a10.71 be10.76 bo10. 47 be11.60ab

* Any two means not followed by the same letter are significantly different atthe 5% level (4).

use of MCP + NH4N03 + KC1 or MCP + KN03, and byusing MCP + K2S04, percentage N was greater with NH4C1than with (NH4)2S04 as the N source. With DP as thenitrogenous and phosphatic source, a greater percentage of Nin straw was obtained with K2S04 than with KCL

Irrespective of phosphatic source, the percentage of P ingrain was significantly in excess of that for the controltreatment (Table 2), but in the case of straw, the percentageP was greater in the control treatment than for some treat-ments receiving P. Percentage P in straw varied from 0.021%to 0.046%. The highest percentage P in grain or straw wasobtained with MCP + (NH4)2S04 + K2SO4. By using MCP+ KC1, there were no significant differences in the percentageP of oat grains with the different ammonium salts as a sourceof N; but in straw, P percentage was significantly higher withNH4N03 than with (NH4)sSOt or NH4C1. With DP as thephosphatic source, the percentage P in straw was significantlygreater with K2S04 than with KC1 but for grain there was nosignificant difference.

The K composition of grain was not significantly affectedby the different treatments imposed, but slight differencesarose in the composition of the straw, and in this respect thehighest percentage was obtained with MCP + NH4C1 +K2S04.

Under greenhouse conditions, leaf chlorosis with greyishbrown necrotic spots and a sagging of the leaf forming asharp kink was most pronounced for the control treatment,and to a lesser degree for the MCP + KN03 treatment. Thesesymptoms are typical of 'grey-speck disease' and are causedby a deficiency of Mn. The Mn content of oat grain variedfrom 13.8 ppm for the control to 54.9 ppm for the MCP +NH4C1 + KCL treatment. If the control treatment were neg-lected, itis still outstanding that with equivalent rates of N, P,and K, Mn concentrations in the grain varied by more than100%. This effect was considerably more pronounced for Mnconcentrations in the straw where variations were 9.4 to 63.4ppm. In general, there was a tendency for greater concentra-tions of Mn with the use of MCP as opposed to DP, and particularly so, for straw.

Total Nutrient UptakeIrrespective of treatments used, the greatest contribution

in total uptake of N and P originated from oat grain, and inthe case of K from oat straw (Table 3). Except for the MCP+ NH4C1 + KC1 treatment, where the greatest uptake of Mnoccurred, there were always greater amounts of Mn in the

HAMILTON: EFFECT OF N AND K SALTS WITH P ON YIELD AND P, N, K, AND MN OF OATS 241

Table 2—Nutrient composition of oat grain and straw as influenced by different salts with monocalcium and diammoniumphosphates (mean of 4 replications)

Treatments Grain Straw

% P %K ppm Mn % N % % K ppm Mn

ControlMCP+ (NIMMCP + (NHONO«MCP + NH4C1 + jMCP + (NH4)2SO4

+ KC1KOI+ K2S04

MCP + (NH»)C1 + K2S04MCP + KNOsDP + KC1DP + K2SO4

1.2.2.2.1.22!12

,92c*20a,14abllab99bc,06abc.OObc.92c.09ab

0.285d0.333c0.336c0.332c0.380a0.3390O.SSlbc0.346bc0.366ab

0.50a0.53a0.56a0.52a0.54aO.S6a0.54a0.54aO.Sla

13. 8h43. 6b33.4ef54. 9a37. Scd39. le25. 2g26. Og34. Ide

0.49abc0.48abc0.54a0.48abc0.53a0.40c0.54a0.43bc0.53a

0.0.0.0.0.0.0.0.0

,028c021d.029c,026cd046a,025cd,042ab,027c.037b

3.38d3.38d3.68abc3.70abc3.74ab3.94a3.47cd3.54bcd3.70abc

6.0d36. 4b19. 4c63. 4a17. 9c

31. 6b9.4d

10.3d12.6cd

* Any two means not followed by the same letter are significantly different at the 5% level (4).

grain than in the straw. With the use of MCP and KOI, thetotal uptake of N varied with the ammonium salts used tosupply N, and this variation was more attributable tovariations in uptake by straw then by grain. Significantlygreater amounts of N were taken up with the use of (NH4)2S04or NH4N03 than with NH4C1. The lowest uptake of N fortreatments receiving fertilizers was obtained with MCP +KN03. The K source supplied with DP influenced the totaluptake of N being significantly greater with K2S04 thanwith KC1.

The total uptake of P and K was greatest with MCP +(NH4)2S04 + K2S04, and was not significantly different fromthat occurring with the use of DP + K2SC>4. With DP as thephosphatic source, significantly greater amounts of K weretaken up with K2S04 rather than KC1 as the K source;however, the uptake of P was not significantly different forthese two sources of K. The total uptake of Mn was con-siderably greater with the MCP + NH4C1 + KC1 treatmentthan for any other treatment, and despite the equivalenceof N, P, and K in the treatments used, total Mn ranged from323.1 Mg to 1,224.1 Mg/pot.

DISCUSSIONIn connection with investigations involving the supply of

the three major nutrient requirements of plants, namely N, P,and K, the great emphasis placed on the nutrients themselveshas not been paralleled with an equal interest in the accom-panying ions in the salts supplying the necessary nutrients.The results of this investigation clearly indicated that despitean equivalence of N, P, and K in the materials used, adistinctly varying effect on yield as well as chemical composi-tion of oats resulted. Moreover, a choice of salts would seem tobe capable of influencing differently, economic yields (grain)

on the one hand and total yield (grain + straw) on the other.It will be observed that whereas grain yields reached amaximum with MCP + (NH4)2SC>4 + KCL, straw yieldeswere at a maximum with MCP + (NH4)2S04 + K2S04. Des-pite a lack of significant differences in yield between some treat-ments, there were nevertheless significant differences in nutrientcomposition for these same treatments. This could reasonablybe explained on the basis of chemical composition being areflection of the products of soil-fertilizer reactions whichmight be in excess of plant requirements; and further that theplant does not selectively absorb these residual products fromthe soil. While there was no significant difference in grain orstraw yields with DP + K2S04 or DP + KC1, the total uptakeof N, P, and K in straw were significantly greater with DP +K2S04 than with DP + KCL On the other hand, it is inter-esting to note that with MCP + (NH4)2S04, the percentageN in oat grains was greater with KC1 than with K2S04.

For treatments receiving fertilizer applications, there weregreater concentrations of N and P in grain than in straw,while greater concentrations of K occurred in straw than ingrain. These results were essentially similar to those obtainedby Sayre (19) working with corn plants.

Because of the greater acidity which develops when MCPreacts in soil (11), and also because of the residual aciditywhich develops from soil nitrification processes, it is under-standable that these acidifying or secondary effects have beengreatly emphasized in explaining crop response and thechemical composition of crops receiving fertilizers (1, 3, 12,18, 19). However, other products of soil-fertilizer reactionsshould not be neglected in that they might even assume adominant role. For instance, it is usually stated that soilacidity facilitates the greater uptake of soil Mn. It seemsdoubtful that the magnitude of differences between theresidual acidity of NH4C1, (NH4)2S04, and NH4N03 would be

Table 3—Total uptake of N,P,K, and Mn by oats as influenced by different salts with monocalcium and diammonium phosphates (meanof 4 replications)

Treatments

ControlMCP + (NH4)!S04 + KC1MCP + NH4NOa + KC1MCP + NH4C1 + KC1MCP + (NH1)2S01

+ K,SO<MCP + NH4C1 + K*SO4MCP + KNOsDP + KC1DP + KsSO4

N, mg/pot

Grain

117. 5d«231. la216. 5a215. la

185. Ibe217. Oa175. 4c191. Obc193. 5b

Straw

38. 4e52.4bcd53.3bcd49.7cd

64. Sa43.2deSS.Oabc44.5de60. Sab

Total

155. 9e283. Sa269. Sab264. 8bc

249. 9cd260. 2bc233. 4de235. 5d254. 3bc

Grain

17.45d34.85a34.17a33. Slab

35.22a35.74a30.80bc34.45a33.96ab

P, mg/pot

Straw

2.20e2.31C2.89c2.69o

5.74a2.66c4.55b2.80e4.27b

Total

19.65c37.16b37.06b36.50b

40.96a38.40ab35.35bc37.25b38.23ab

Grain

30. 4d55.6ab57.0ab53. 4b

49. 9c58. 9a47. Oc54. Ob47. Oc

K, mg/pot

Straw

262. 3e372. Scd363. 2d382.6bcd

466. 2a421.0abc373. 4cd370.3d428. Sab

Mn, Mg/Pot

Total

292. 7e428. 4cd420. 2d435.9bcd

516. la479. 9ab420. 4d424.3d475.3abc

Grain

84. 4g459. 8b338.10562. Sa

352. 8c413. 9b221. 9ef261. Ide316. 2cd

Straw

46. 7f400. 5b190.6de661 . 3a

220. 7d338. 6bc101.2ef107.7ef143.7def

Total

131. le860. 3b528. 7c

1224. la

573.50752. 5b323. Ide368. 9d459. 9cd

* Any two means not followed by the same letters are significantly different at the 5% level (4).

242 SOIL SCI. SOC. AMEH. PROC., VOL. 30, 1966

of the order to account for the considerable differences in thetotal uptake of Mn observed in the investigation, or alterna-tively, a relatively small change in pH has a pronounced effecton Mn uptake. Teater et al. (20) found the residual acidityfrom (NH4)2S04 to be only very slightly greater than that forNH4C1. It seems more probable that there is some relationbetween high fertilizer chloride concentrations and the greateruptake of Mn.

The findings of Hammes and Berger (6) that Mn deficiencyin oats can be expected when soil Mn extracted with O.lNphosphoric acid is < 20 ppm was borne out in this investiga-tion where soil Mn was 12.3 ppm, and the typical symptomsof Mn deficiency were quite pronounced for the controltreatment.

The facilitating effect of P as well as the salts associatedwith P on the uptake of Mn would seem to indicate that evenin the event of a naturally low soil Mn concentration, wide-spread occurences of the deficiency are not likely to show upin the field when normal fertilizer practices are adhered to.