J. Agronomy and Crop Science 159, 199—201 (1987)© 1987 Paul Parey Scientific Publishers, Berlin and HamburgISSN 0931-2250

Department of Soil Science, University of Manitoba,Winnipeg, Manitoba, Canada R3T 2N2

Effect of NH4''" Nitrogen on Phosphorus Uptakeby Canola, Lentils, Soybeans and Wheat

U. R. SANGAKKARA and C. M. CHO'

Authors' addresses: Dr. U. R. SANGAKKARA, Faculty of Agriculture, University of Peradeniya, Peradeniya,Sri Lanka and Prof. Dr. C. M. CHO, Department of Soil Science, University of Manitoba, Winnipeg,Manitoba, Canada R3T 2N2.

With one table

Received October 21, 1986; accepted November 28, 1986

Abstract

Phosphorus and ammonium nitrogen placed together has been shown to increase P uptake by crops,especially cereals. Thus, the objective of this study was to compare this effect on four crops grown inManitoba. Plants harvested at flowering indicated greater P uptake in lentils, soybean and wheat, when P andNH4^-N were placed on the same band. In contrast, canola did not respond to this treatment. Possiblerelationships of these ions are presented.

Introduction

Nitrogen has been shown to enhance theuptake of applied phosphorus especially whenboth fertilizers are placed in a single band inthe soil (GRUNES 1959, ENGLESTAD and ALLEN

1971, LEIKAM et al. 1983). This effect is mostconsistently demonstrated when N is suppliedas NH4^-N rather than NO3"-N (LEONCE andMILLER 1966, MILLER 1974). Many factors areattributed to this phenomenon (MILLER 1974).

Most studies reporting this N-P relationshiphas been carried out with cereals (RENNIR andSoPER 1958, FLATENand RACZ 1985, WESTERMAN

and EDWARD 1985). Very few studies (e.g.,RACZ et al. 1965) indicate this effect in otherspecies. Thus a study was carried out toobserve the generality of this phenomenon infour crops commonly grown in Manitoba.

' Visiting I.A.E.A. fellow and Professor of SoilScience, respectively. Address of senior author:Faculty of Agriculture, University of Peradeniya,Sri Lanka.

Materials and Methods

A growth chamber experiment was conducted using"P labelled K,HPO4 during October 1985—Januar>'1986. The four crops. Wheat {Triticum aestivum).Lentils {Lens esculenta). Soybeans {Glydne max) andCanola {Brassica napus) were seeded into pots con-taining 5 kg of an Elm Creek soil (a VFSL; pH 8.0;available PO4^ 17.2 mg kg''). The environmentalconditions used were 22 °C—50 % RH day/15 °C—80 %. RH night with a 16 h daylength.

A basal application equivalent to 200 kg ha"' ofpotassium was added to the pots prior to seeding.The NHj "̂ was added in the form of NH^NOj into a20 mm deep band 25 mm away from the seed, at arate equivalent to 100 kg N ha"'. The labelled P wasapplied onto the NH^* fertilizer band or onto theopposite side of the NH4' band, at a similar depthand distance. The rate of P was equivalent to 50 ks,ha-'.

Seedlings were thinned to three plants per potsoon after germination. Plants were harvested at 45days after germination, which corresponded with theflowering stage. Plants were dried at 80 °C for 24 h,weighed and ground. Total P content was deter-mined colorimctrically and the uptake of radioactiveP measured by liquid scintillation counting.

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200

Table 1.

Crop

Phosphorus utilization

Treatment*

patterns when banded

Total Puptake

mg pof'

with or without

Fert. Puptake

mg pof'

NH/-N

PDFF

SANGAKKARA and

% Soil Puptake

mg pot"'

CHO

Canola

Lentils

Soybeans

Wheat

TlT2

Tl

T2

TlT2

TlT2

2941.92847.1

2473.51480.5*

4534.62928.0*

3215.31960.7*

409.1397.5

600.3171.9*

1489.6546.4*

1202.5409.7*

13.9113.97

24.3211.72*

32.84

18.66*

37.4220.89*

2532.72449.9

1873.1

1308.6*

3045.1

2381.5*

2012.7

1550.9*

* Tl = P & N banded together; T2 = P & N banded separately.* Indicates significant differences (P = 0.05) between treatments.

Results

The effects of banding P fertilizer togetherwith NH4''"-N or separately upon P uptake byfour crops are presented in Table 1. Wheat,soybeans and lentils show increased uptake ofP when added together with NH4'^-N. How-ever, this effect is not observed in canola,indicating a lack of response to this treatment.

Addition of P together with NH4^-Nincreased total P uptake in lentils, wheat andsoybeans by 67 %, 64 % and 54 % respec-tively. This effect was most prominent in theuptake of fertihzer P, where P uptake overseparate treatment in lentils, wheat and soy-beans were 249 %, 197 % and 172 %, respec-tively. A similar pattern of increases wereobserved in P derived from fertilizer (PDFF)although the value obtained with lentils wasless than that observed in wheat and soybeans.

The addition of P together with NH4'^-Nalso increased the uptake of soil P by lentils(43 %), wheat (30 %) and soybeans (28 %).This suggests that the addition of fertilizer Ptogether with NH4''' not only increases fer-tilizer P uptake, but also soil P, causing asynergistic effect on the uptake of both formsof P from soil.

Discussion

Many mechanisms have been cited to explainthe effect of NH4''"-N in increasing P uptakewhen both are applied together (MILLER 1974).However, research has not identified specificmechanisms although the phenomenon is

amply demonstrated especially in cereals. Theresults of this study also support thisphenomenon in wheat, soybeans and lentils.

Canola is considered an efficient utilizer of P(RACZ et al. 1965) when compared with othercrops. This is also shown in this study, wheretotal P uptake by canola is greater than lentilsand wheat when NH4"^-N and P are bandedseparately. Hence, the lack of response to theaddition of P together with NH4'^-N could beconsidered a resultant function of the ability.

While much emphasis is placed on the effectof NH4'^-N in increasing P uptake, few studies(e.g., STAROSTKA and HILL 1955, FRANKLIN 1972and SWAN 1984) illustrate similar effects on thepresence of other cations. Thus, interpretationof results such as those of this study shouldalso be considered in the above context, whereother cations and not NH4''' alone could have astimulating effect on the uptake of P. As thisstudy did not attempt to identify the causalfactors, further experiments are required toelucidate the mechanisms of the relationshipbetween NH4'*" or other cations and increasedsoil and fertilizer P uptake by crops and thelack of response by crops such as canola to thistreatment.

Zusammenfassung

Einflufi von NH4+-Stickstoff auf die Phos-phoraufnahme durch Canola, Linsen, Soja-bohnen und Weizen

Phosphor und Ammonium-Stickstoff gemein-sam plaziert ausgebracht bewirken eine Zunah-

Effect of NH4'̂ Nitrogen on Phosphorus Uptake by Canola, Lentils, Soybeans and Wheat 201

me der P-Aufnahme durch Kulturpflanzen,insbesondere Getreide. Ziel der Arbeit war es,diesen Effekt bei vier Kulturpflanzenarten, diein Manitoba angebaut werden, zu untersu-chen. Die Pflanzen wurden zur Bliitezeit ge-erntet; sie zeigten eine hohere P-Aufnahme beiLinsen, Sojabohnen und Weizen, wenn P undNH4"''-N plaziert als Banddiingung ausge-bracht wurde. Im Gegensatz dazu reagierteCanola nicht auf diese Behandlung. MoglicheBeziehungen der Ionen werden diskutiert.

Acknowledgements

The senior author is grateful to the InternationalAtomic Energy Agency, Austria for the fellowshipto enable him to undertake this study.

References

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