THE SIGNIFICANCE OF NITROGEN MOBILIZATION WITH
RESPECT TO THE DEVELOPMENT OF BARLEY

Yrjö Pessi and Mauri Takala

Society of Peat Cultivation Experimental Station, Leteensuo
Received July 8, 1959

Numerous factors affect the rate of development of plants, temperature being
one of the most essential ones. The quantity in the soil of nitrogen utilizable by the
plants also exerts an influence upon their time of growth. The present investigation
carried out at the Experimental Station of Leteensuo, permits some conclusions to
be drawn in regard to the significance of the said factors for the development of
barley plants.

The procedure of investigation was to sow the test plants simultaneously on two
growth sites differing distinctly with respect to nitrogen mobilization. The air and
soil temperatures were measured on both sites and observations were made of the
different stages of development of the plant, i.e. the shooting, the coming into ear,
and the ripening. One of the growth sites had a tilled layer consisting of forest peat,
in which the nitrogen mobilization is abundant enough to obviate the use of nitrogen
fertilizer. The substrate on the other growth site was Sphagnum peat originating
from 5. fuscum moss, with a very slight nitrcgen mobilization. The fertilization app-
lied to fen soil consisted of 300 kg superphosphate ard 150kg 50% potassium chloride
per hectare, while the peat bog received 200 kg Oulu saltpetre per hectare in addition.
The barley was of the Pirkka variety. The method of air and soil temperature
measurements has been described in an earlier publication. 1

Table 1. Stages of development of Pirkka barley on fen and Spahgnum bog soil at Leteensuo in the
summer of 1958

Soil type Sown on Shoöting Coming Ripening
into ear

Fen 11. VI 17. VI 26. VII 15. IX
Sphagnum bog 11. VI 18. VI 28. VII 8. IX

1 Pessi, Y. & Takala, M. 1959. Some results of measurements at the Leteensuo Experimental
Station relating to the temperatures of air and soil and to the humidity of air in the summer of 1958.
Selostus; Eräitä ilman ja maan lämpötilaa sekä ilman kosteutta koeskevia mittaustuloksia Leteensuon
koeasemalta kesällä 1958. Maat. tiet. aikak. 31:207—211.



249

Table 2. Air temperature at the upper limit of the plant cover, and soil temperatures at 5 and 10 cm
depth, on the growing sites of Pirkka barley

Soil type Monthly mean of air Monthly mean of soil temperature

temperature f> cm depth ]() cm depth

VI VII VIII VI VII VIII VI VII VIII

Fen 16,0 17,2 15,3 14,9 17,0 15,1 13,4 16,3 14,7
Sphagnum bog 16,4 16,9 15,2 14,7 16,4 15,3 13,0 15,8 14,7

The weather conditions in the summer of the investigation were characterized
by the fact that every month of the growing period had a mean temperature about
1° C lower than normal. The mean temperature of the period May to September
was 12.1° C. The rainfall during the period May to September was 240 mm.

Table 1 shows the different stages of development of the barley plants, and Table
2 the air and soil temperatures. It can be seen that up to the time of coming into ear
the barley had developed at nearly the same rate on both growing sites, although
its development had been slightly slower on the Sphagnum bog. However, the period
of development from the coming into ear to the ripening was nine days shorter on
the Sphagnum bog than on the fen site. It is evident from the temperature figures
that the slower initial development of the barley plants was probably caused by
the lower soil temperature. On the other hand the temperature of air as well as soil
had been largely the same on both sites during the last period of development, i.e.
the period from the coming into ear to the ripening. It appears likely, therefore,
that the longer duration of this period on the fen site would account for the different
mobilization of nitrogen. Since in the Sphagnum bog the nitrogen situation during
the growing period is probably primarily such that the quantity of nitrogen utilizable
by the plants at the beginning of the growing period is perhaps equivalent to that in
fen soil, owing to the fertilization administered and to the low nitrogen mobilization,
the nitrogen quantitity will become less as the plants use it up towards the autumn.
In fen soil, on the other hand, the quantity of usable nitrogen can be assumed to
increase owing to nitrogen mobilization, and this results in a delay in the ripening.
The possible differences of soil moisture conditions between various peat types was
probably not the cause of the difference at the time of ripening mentioned above,
because e.g. in August it rained 47 mm, so that the plant stands were not affected
by dryness.

Summary
In the investigation has been stated, that up to time of coming into ear the

barley had developed at nearly the same rate on the Sphagnum bog and the fen,
which are differing distinctly with respect to nitrogen mobilization. However, the
period development from the coming into ear to the ripening was nine days shorter
on the Sphagnum bog than on the fen site. The temperature of air as well as soil
had been largely the same on both sites during the period of development, from the
coming into ear to the ripening. It appears likely, therefore, that the longer duration
of this period on the fen site would account for the different mobilization of nitrogen.
2



250

SELOSTUS;

TYPEN MOBILISAATION MERKITYKSESTÄ OHRAN KEHITYKSEEN

Yrjö Pessi ja Mauri Takala

Suoviljelysyhdistys , Leteensuon koeasema

Tutkimukset on suoritettu siten, että samanaikaisesti on koekasvi kylvetty kahdelle, typen mobili-
saation puolesta erityisen selvästi toisistaan poikkeavalle kasvupaikalle. Lisäksi on mitattu ilman ja
maan lämpötila molemmissa paikoissa sekä tehty havainnot kasvin eri kehitysasteista, nimittäin oras-
tumisesta, tähkälletulosta ja tuleentumisesta. Toisen kasvupaikan muokkauskerros on ollut metsäsara-
turvetta, jossa typen mobilisaatio on siksi runsasta, että typpilannoitusta ei tarvitse käyttää. Toisen
kasvupaikan kasvualusta on ollut taas Sp. /«scwm-sammaleesta muodostunutta rahkaturvetta, jossa
typen mobilisaatio on erittäin vähäinen. Lannoituksena annettiin mutasuolla 300 kg superfosfaattia ja
150 kg 50-%-kalisuolaa hehtaarille. Rahkasuolle annettiin näiden lannoitteiden lisäksi 200 kg Oulun-
salpietaria hehtaarille. Lajikkeena oli Pirkka-ohra. Ilman ja maan lämpötilan mittaustapa on selostettu
aikaisemmin (ks. kirjallisuusviittaus s. 248).

Taulukossa 1 esitetään ohran eri kehitysvaiheet sekä taulukossa 2 ilman ja maan lämpötila. Niistä
ilmenee, että ohra on kehittynyt tähkälletuloon saakka molemmissa kasvupaikoissa lähes yhtä nopeasti,
joskinrahkasuolla hieman hitaammin. Kehitysvaihe tähkälletulosta tuleentumiseen on rahkasuolla ollut
kuitenkin 9 päivää lyhyempi kuin mutasuolla. Lämpötila-arvoista ilmenee, että ohran hitaampi alkukehi-
tys rahkasuolla lienee johtunut maan alhaisemmasta lämpötilasta. Toisaalta sekä ilman että maan läm-
pötila on ollut viimeisen kehitysvaiheen aikana, siis tähkälletulon ja tuleentumisen välillä, jokseenkin
sama molemmissa kasvupaikoissa. Mainitun kehitysvaiheen muodostuminen mutasuolla 9 päivääpitem-
mäksi kuin rahkasuolla johtunee näin ollen typen mobilisaation erilaisuudesta kasvupaikkojen kesken.
Kun typpitilanne rahkasuossa kasvukauden aikana lienee lähinnä sellainen, että kasveille käyttökelpoisen
typen määrä on annetun lannoituksen ja vähäisen typen mobilisaation johdosta kasvukauden alussa
ehkä mutasuon typpitilannetta vastaava, vähenee typen määrä syksyä kohti kasvien käyttäessä sitä.
Sen sijaan rautasuossa typen mobilisaation ansiosta käyttökelpoisen typen määrä lisääntynee syksyä
kohti, mistä on seurauksena tuleentumisen viivästyminen. Maan kosteusolojen mahdollinen eroavuus
eri turvelajien kesken ei liene aiheuttanut mainittua eroa tuleentumisajankohdassa, sillä mm. elokuussa
satoi 47 mm, eikä kuivuus vaivannut kasvustoja.