On the use of aspergillus niger for the determination of plant nutrients in the soil

ANALYTICA

782

ON NIGEX

ASP,?‘XGILLUS PLANT

THE FOR

NUTRIENTS

CHIMICA ACTA

USE

VOL. 2 (1948)

OF

THE IN

DETERMINATION THE

OF

SOIL

17.C. GERRETSEN AgrrcuZlzrraZ JZxjxviruexl Siatiow and Insfllute for Soal Research, Grouinpn (Netlrcvla~zds)

T.N.O.

In the search for reliable, quick and cheap methods to determine plant nutrients in the soil, increasing attention is being paid to microbiological methods. The main principle underlying these methods is the law of minimum of LIEBIG (x843), according to which the growth of a plant (mould in this case) is a function of the nutritive constituent, which is present in minimum amount. Moreover the way in which a mould absorbs the nutrients from the soil generally shows more resemblance with the behaviour of a plant than the chemical methods do. BUTKIZWITSCH~ was the first to show that the weight of the mycelium of the As#evgiZZzcs nigev increases in a regular way with the content of potassium or of phosphorus in the nutrient solution. However with the minor elements and especially with copper, the situation is somewhat different, because a very minute quantity of this element suffices for the growth of the mycelium, whereas for the development of the spores and specially of the black colour of the spores, larger quantities of copper arc wanted. In this case the colour of the spores is a reliable measure for the estimation of very small quantities of copper (MULDIXR~). NIKLAS and coworlcer9 were the frst to develop a method for the determination of phosphorus and potassium in soil, which could be used for routine work. They use 30 ml of a nutrient solution deficient in the one element to be determined in Erlenmeyer flasks of 75 ml; they add 2.5 g soil, which has to furnish the missing element and they inoculate with a spore suspension or with a mixture of dry spores and talcum. After cultivating 4 days at 35” C the mycelium is washed, dried and weighed. It is evident, that the culture solution must be complete with regard to all the other requirements of the mould; when this is not the case, different soils will provide different quantities of these lacking nutrients and the results will not reflect the actual situation with regard to the element to be determined. References p. 7gr.

VOL. 2 (1948) When

PLANT

following

exactly

strain, which

he

had

put

larities could

be

traced

NUTRIENTS

NIKLAS'

instructions

following

I. The

culture

solution

was

2. The

weight

of the mycelium

TIXE

783

SOIL

and

using

disposal, the results were

at our to the

IN

AspergiZZus

his own

conflicting; the irregu-

causes:

insufficiently buffered. was

markedly

affected

by

the

calcium-content

of the soil. 3. The

culture

favoured

solution

the growth

4. The pensive

Asfwrgillus for mass

was

not optimal,

some

soils contained

substances

which

Aspergihcs.

of the NIKLAS

wanted

determinations

peptone

and

favours

for optimal the growth

growth,which

is ex-

of contaminating

micro-

organisms. Our

first task

changes

was

during

being

that

the

the

left behind

to improve growth

fungus

the

of the

produces

culture

fungus

citric acid

after the assimilation corresponds

with

from

from

the

more

phosphate

Webegan not

because

behind

the

reduced,

an

mould

as well. With

radical.

prefers

Asparagine

urea

the

seemed

moreover

pkI changes

TZIE

ammonium the

however very

grows

0.002 0.006 0.010

INFLUENCE

In

0.39 1.07 1.42

order

to

References p. 7gr.

acid

is

phosphate

and

in the soil,

is not constant, butislowcr,

by

60%.

grew The

solution

the pH

we

cnd

were

peptone

for

assimilated, urea

acid greatly

optimal

ON YIELD AND 4 DAYS 37’C)

Aspev-

in isolating

growth.

FINAL

~;~;%,:fnThsc

With

in Table

an

urea I.

PH

(Nl-M,SO,

%!EF

the

as a sole nitrogen

results are summarized

Asp;traglnc G 8/l

_--..-F bcglnmng

would

unsuitable,

becomes

changes

succeeded

escellentwith

TABLE I THE NITROGEN SOURCE (A_+. 9lZgCY STRAIN GRONINCEN,

increase

the

which

to be

for mass-analyses.

it. However

OF

3.41 3.43 3.41

and

well and

proved

as it is altogether

did not want

reduced

nitrate

is too expensive

promising

this strain were

wclght of the myceln3m. g

pn

cause

sulphuric

by a nitrogensource,

to nitrate

mould

Urea 4 g/l p,o* 1Il %

The

main

of the mould

of available

Ammonium

gillus NIKLAS did not grow well with Aspevgillus strain from currents, which source;

and

dependsonthegrowth

the quantity

ammoniumsulphatc

acid

the substance

Though

points.

the soil contains.

to replaccthc

leave

these

to 1.3, the

sugar

it is evident that the pn at which the soil is extracted the

on

3.5

of theammoniumfromthcammoniumsulpl~ate.

of the acids produced

Asthequantity this in its turn

solution

ran

6 s/l

-

-*

2.89 3*2.65

the

buffer

0.39 1.02 1.50

capacity

;::: 361

of the

2.86 2.72 2.43

solution,

0.40 1.17 1.58

;:Z 3.62

calciumcitrate

2.88 2.24 x.84

was