W HA T H A P P E N S TO THE PH O SPH O R U S
FROM SU PE R P H O SPH A T E IN THE SO IL NOT ABSORBED BY PL A N T S AS ESTA B LISH ED ON THE B A SIS O F FIELD
EX PER IM EN T S CARRIED ON FO R M ANY YEARS
D epartm ent of A gricultural Chemistry, A gricultural U niversity, W arsaw Head — Prof. Dr. J. G óralski
W hen ph o sp h ate fertiliz e rs are used, on ly one fifth of th e p h o sp hate is absorbed b y p la n ts in th e firs t y ear. M any reasons m ay be given to e x p lain w h y th e p lan ts absorb o nly a sm all q u a n tity of ph o sp h ate o u t of p h o sp h ate fertiliz e rs. T he m o st im p o rta n t are: th e ré tro g ra d a tio n of phosphate, i.e. its developing into a fo rm w hich is less soluble th a n th a t g e n e ra lly used in fertilizers, an d th e fac t th a t ro o t system s can come into touch w ith a lim ite d q u a n tity of availab le ph osphates, an d th e ir diffusion is a slow process.
It is an in te re s tin g p o in t for a g ric u ltu re to get to know in w h a t com pounds th e u n u sed p h o sp h ate of th e p h o sp hate fertiliz e rs su b seq u e n tly develops and w h a t is its a v a ilab ility for p lan ts in th e follow ing years. R esearch w ork on th e p h o sp h ate fra c tio n has b een c a rrie d on b y C h a n g and J a c k s o n [3, 4].
In th e p re s e n t p a p e r th e re s u lts of th e re se a rc h w ork on th e fa te of th e un u sed ph o sp h ates w hich re m a in in th e soil w h e n su p e rp h o sp h a te w as used in th e podzolic soil a re given. F or th is p u rp o se som e soil sam ples o b tain ed from field e x p e rim e n ts a t Skierniew ice ca rrie d on san d y loam w e re an alysed fo r th e p h o sp h ate com pounds. (The long te rm average of ra in fall w as estim a ted a t 500 m m . a year).
In 1962 soil sam ples w ere o b tain e d fro m fo u r fields using th e follow ing com binations of fe rtiliz e rs a t th e E x p e rim en ta l F ield a t Skiern iew ice w h ere th e sam e fe rtiliz e rs h av e been used since 1923:
1 M. Petrovic — Faculty of Agriculture and Atom ic Energy Commission — Beograd-Zem un, Yugoslavia.
8 2 S. Moskal, M. Petrovic
F ield A m — N K 30 kg. N (sodium n itra te ), 60 kg. K 20 (potassium m uriate), N P K as N K + 30 kg. P 20 5 (superphosphate), C aN PK as N P K + 16 q CaO e v e ry fo u r year.
F ield A F n j — th e sam e fe rtiliz e r as in A m b u t th e n itro g e n w as used in th e fo rm of am m onium su lp h ate. In fields А щ and A F n i th e a rb itra ry ro ta tio n has been applied. M anu re has n o t been u sed and legum e p la n ts have n o t been cu ltiv ated .
F ield D v — fe rtiliz e r N P K as used in th e field А щ , b u t 12 q CaO for 1 ha p er y e a r w as ap p lied for th e CaN PK . P o tato es a re alw ays p lan te d .
F ield D VI — th e sam e as Dy. R ye in alw ays grow n.
T he soil in each p a rtic u la r field h a d a slig h tly d iffe re n t m echanical com position and p h o sp h oru s co n ten t.
T h e m e t h o d o f r e s e a r c h w o r k . T he soil phosp ho ru s fra c tio n a tio n w as c a rrie d on according to th e system in tro d u c ed by C h a n g a nd J a c k s o n [3]. T otal soil phosph orus w as e stim ated by digestion w ith p erchlo ric acid — th e m eth o d in tro d u c ed b y V o l k a nd J o n e s and m odified b y B r a y a nd K u r t z [1].
In th e soil u n d e r rese a rc h th e to ta l am o u n t of phosp ho ru s w as esti m ated ; th e loosely b o u nd phosphates, th e non-occluded alum iniu m and iro n p h o sp h ates and th e easily available p ho sphates w ere e stim ated w ith th e E gn er-R iehm m eth o d ; th e chem ical p o ten tia l of p h osp hates — w ith S chofield's m eth o d. T he re su lts of th e above rese a rc h w ork are given in Tab. 1.
F e rtiliz atio n by m eans of su p e rp h o sp h a te in all th e fields in qu estio n b ro u g h t in crease (30— 100%) of th e ph osph orus c o n te n t in th e soil. Also th e co n ten t of loosely bound p h o sph ate and non-occluded alu m in iu m and iro n p h o sph ates as w ell as th e p h o sp h ates estim ated by E g n e r’s m ethod, w as h ig h er in N P K th a n in NK.
It w as easily n oticed th a t lim ing h ad a ffected th e p h osp ho ru s co n ten t in th e soil. The to ta l am o u n t of p h osph orus in th e lim ed plots w as m a rk e d ly low er th a n in th e n o n -lim ed ones. A ltho ug h in g en eral th e pho sp horu s co n te n t in th e lim ed plots w as low er, th e q u a n tity of easily b ou nd p h o sp h ates and ph o sp h ates estim ated b y E g n e r’s m eth o d w as m u ch h ig h er. This suggested th a t th e reaso n for th e low er co n te n t of p h osph oru s foun d in g e n e ra l in th e lim ed plots m ay be ex p lain ed in p a rt b y th e h ig h er ab so rp tio n of p h o sp h o ru s b y p lan ts. T he analysis of th e
Influence of 40 years using o f f e r t i l i z e r s on phosphorus sta tu s at Skierniew ice Experimental S tation In plough la y er 0-20 cm. 20-40 cm. F ie ld F e r tiliz e r treatment PH t o ta l phospho rus lo o se ly bond phospho rus alumi nium phospha te s iroh phospha te s calcium phospha te s phospho rus by method Scho f i e l d ' s phos phate poten t i a l depfth Total phosphor, mg. P20f 1000 g. s a i l
h2o KC1 mg. P2O5/IOOO g . of the s o i l IO“* M
H2P04 /g A rîitraxy ro ta tio n UK-30 kg. N(NaNOj) 60 kg. KgOUCl) NPK-30 kg. N(NeNOz) 60 kg. KgOCKCl) ♦ 30 kg. P2O5 ( superphosphate) CaNPK as NPK+16 \ CeO/ha/4 years
5 .3 5 .6 6.5 4 .3 4 .5 6 .0 425 820 720 6 .0 13 .7 28.7 70.0 143.7 110.0 9 4.0 100.0 9 5.0 68.0 65.0 76.2 3 2 .0 8 8.0 147.0 0 .4 2 .4 6 .5 575 536 527 ^ I I I Arbitrary ro ta tio n NK as in A jjj № 4)2 • S04 4 .5 4 .2 342 7 .0 4 2.5 6 5 .0 54.0 29.0 0 .4 335 NPK as in Aj j j 4 .4 4 .2 770 10.0 100.0 115.0 68.7 95.0 1.4 288 CeUPK as in | 6 .0 5 .5 720 3 0 .0 75.0 77.5 67.5 120.0 4 .7 329 % NK as in A jjj 5 .2 4 .4 520 7.5 6 6.2 100.0 58.7 3 9.0 0 .7 395 Continuous p otatoes NPK as in Ajj j 5 .9 5 .2 670 20.0 I 25.O 108.7 75.0 9 4.0 3 .5 310 CaNPK as NPK + 12 q. CaO 6.8 5 .9 '640 33.7 53.7 100.0 8 1.2 140.0 4 .« 346 Manure 200 'q /h a /y e a rly 5 .5 4 .6 580 8 .7 58.7 95.0 5 6.2 4 5 .0 1 .4 -%I NK as in Aj jj 5 .4 4 .4 275 6 .0 3 4 .0 4 8 .0 77.0 1 6.0 0 .4 274 Continuous rye NPK as in Aj jj CaNPK as in A jjj NPK + 12 <1 ЪаО 5 .7 7 .2 4 .8 6 .1 450 400 11.2 28.7 67.5 57.5 6 5.0 4 0 .0 53.7 65.0 5 0.0 125.0 1.3 1.6 288 271 F at e of th e p h o sp h a te s unabsorbed by p la n ts
84 S. Moskal, M. Petrovic
p la n t m a te ria l has p a rtly confirm ed o u r supposition (Tab. 2 i) . The ph osph orus c o n ten t in, and th e ab so rp tio n of th e p ho sp h o ru s by, th e p lan ts in th e lim ed plo ts w ere m u ch h ig h er th a n in th e n o n-lim ed p lots in th e A F jn field, a n d slig h tly h ig h er th a n in th e Dy! field; no m a rk e d d iffe re n c e w as noticed in th e А щ field, an d in th e D y field th e resp e c tiv e fig u res w ere low er. It is q u ite possible th a t in th e y ears w h en some o th e r p la n ts w ere g row n th e re th e p h o sp horus ab so rp tio n of th ese plots
w as som ew hat d iffe re n t.
T a b l e 2
Y ield o f p la n ts , percentage and uptake of phosphorus
F ield P erti l i - zer tr e a t ment Plant
Y ield q/ha Percentage o f P20^ Uptake of phosp
kg.P20^/hahorus grain
tuburs straw s terns graintubers strawstems graintubers strawstems t o ta l
ai i i NPK Bye 27.3 4 9.5 0.680 0.255 18.6 11.1 29.7 CaNPK 27.2 4 9.5 0.700 0.260 19.0 11.3 30.3 " i l l NPK Wheat 2.3 9 .2 0.560 0.125 1.3 1.1 2.4 CaNPK 27.3 50.3 0.680 0.090 18.6 4 .5 23.1 NPK Potatoes 113.0 0.161 18.2 CaNPK 100.0 0.122 12.2 NPK Эуе 16.5 41.5 0.620 0.210 10.2 8 .7 18.9 CaNPK 18.6 42 6 0.670 0.225 12.5 9 .6 2 2.1
T he low er co n ten t of to ta l p h o sp h o ru s in th e plough lay e r in C aN PK (by sim ilar u ptak e) m a y be caused also by less in te n siv e u p tak e of p h o sp ho rus from deep er lay e r or by trans'location of phosp ho ru s to subsoil because h ig h er so lu b ility of p hosphates. H ow ever h ig h er co n ten t of to ta l p h o sp horu s in C aN PK in c o m p a rtm e n t 20— 40 cm. deep was on ly in A F jn an d D v fields.
M arked differen ces in th e p h osph o ru s co n ten t w ere noticed in th e neig h b o uring fields w h e re p otatoes and ry e w ere con tinu ou sly grow n. In th e D v field u n d e r p otatoes th e to ta l p h o sphorus co n te n t and p h o sph ate easily availab le for p la n ts was m uch h ig h er th a n in th e Dyr field u n d e r rye. T he sam e applies to th e fields A m an d A F jn w h ere d iffe re n t p lan ts w e re cu ltiv a te d and w h e re th e phosp h orus co n te n t w as m uch hig her.
C ontinuous ry e grow ing leads to g re a t e x h a u stio n of p hosp h o ru s in th e p lough lay e r and a t p re se n t th e ry e crop in th e D yi field is m uch low er th a n in th e А щ field, w h e re th e sam e fertiliz e rs h a d been used.
T he a m o u n t or loosely b ound p h o sphates in th e D y field, w h ere m a n u re an d n itra te -p o ta ssiu m fe rtiliz e r w ere a lte rn a te ly applied, was
co n sta n t b u t m uch low er th a n in th e case w hen n itra te , p h osph orus and po tassiu m fe rtiliz e rs w ere used.
T he co n ten t of non-occluded alu m in iu m p h o sp hates (the occluded a lu m in iu m w as n o t ta k e n into consideration) in N P K in all th e fields w as m a rk e d ly h ig h er th a n in C aN PK . T he co n te n t of iron pho sp h ates w as also h ig h er in N P K . As reg a rd s th e c o n ten t of calcium p ho sp h ates th e in v erse p h eno m enon w as observed. In th e N P K plots of th e А ш , D v and Dy! fields a little sm a lle r q u a n titie s of calcium ph o sp h ates w ere found th a n in th e C aN PK plots. In th e A F ni field th e re w as no difference in th e above co n te n t irre sp e c tiv e of th e com bination of fertiliz e rs used. T he co n te n t of calcium p h o sp h ates w as sim ilar in all fields.
A lth o u g h su p e rp h o sp h a te had b een used for 40 y ears, th e c o n ten t of calcium p h o sp h ate in th e soil w as o n ly v e ry slig h tly if a t all in creased b y th is fertilizatio n . B u t a t th e sam e tim e th e co n te n t of non-occluded alu m in iu m p h o sph ates w as tw o tim es h igher. In th e case of a v e ry acid soil in th e A F m field, w h ere n itro g e n w as used in th e fo rm of am m o niu m su lfate, th e c o n ten t of th e iro n p h o sp hates w as increased alm ost tw ofold. T his m ay lea d to th e conclusion th a t in th e conditions existin g in th e Sk iern iew ice soils th e calcium p ho sp h ates w hich have no t been tak e n up by p lan ts change into-non -o cclu d ed alu m in iu m or, if th e soil is v e ry acid, into iro n p ho sp h ates as w ell. T hese p h osp hates re m a in p resu m a b ly for a long tim e in th e colloidal form w hich can be easily absorbed by p lan ts. This is p roved b y th e m u ch h ig h er q u a n tity of phosph o rus e stim a ted b y E g n e r’s m eth o d in th e soil sam ples w ith a h ig h er co n ten t of non-o cclud ed pho sp h ates and iro n p hosphates. Colloidal alum in ium and iro n p h o sp hates a re q u ite a good source of phosph orus fo r p lan ts [6, 8, 9].
If w e assum e th e q u a n tity of phosp h orus e stim ated by E g n e r’s m eth o d as a m ea su re of th e a v a ilab ility of p h osphates, th e n th e a v ailab ility of non-occluded alu m in iu m for p la n ts w as m uch h ig h er in th e lim ed plots.
In th e p lots fertilized b y su p erp h o sp h ate, ab o u t tw o th ird s of th e pho sp horu s easily av ailab le fo r p la n ts (estim ated b y E g n e r’s m ethod) w as o b tain ed fro m th e p h osph o ru s fertiliz e rs used. If besides su p e rp h o sp h a te lim e w as also used, th e n th e q u a n tity of av ailable fe rtiliz e r phospho rus w hich h ad n ot b een used b y p lan ts in p revious y ears w as even g rea ter.
W ith th e ex ception of th e continuous ry e field, th e co n te n t of phos ph o rus estim a ted by E g n e r’s m eth o d in th e plots w h ere th e sam e fertiliz e rs h ad b een used w as closely sim ilar, irre sp e c tiv e of th e k in d of th e n itro g e n fe rtiliz e r u sed and of th e p la n ts cu ltiv ated .
T he q u a n tity of loosely bound p h osphates in creased succesively as follow s: N K < N P K < C aN PK , and w as closely sim ilar in all th e fields
86 S. Moskal, M. Petrovic
irresp ectiv e of th e to ta l co n te n t of ph o sphorus and of its fractio ns w hich proves th a t th e above q u a n tity w as in flu en ced and controlled by th e sam e factors in e v e ry field.
S cho field’s p h o sph ate chem ical p o ten tia l w as m a rk e d ly h ig h er in C aN PK th a n in N PK . O n C aN PK plots of th e field w ith continuous ry e th e ph osp h ate p o ten tial w as sev eral tim es low er th a n in o th e r fields.
REFERENCES
[1] B r a y R. H.* K u r t z L. T.: D eterm ination of total, organic available forms of phosphorus in soils. Soil Sei. 59, 1945, 39—45.
[2] C h a n g S. C., C h u W. K.: The fate of soluble phosphate appield to soils. J. Soil. Sei. 12, 1961, nr 2, 286—293.
[3] C h a n g S. C., J a c k s o n M. L.: Fractionation of soil phosphorus. Soil Sei., 84, 1957, 133— 144.
[4] C h a n g S. C., J a c k s o n L. M.: Soil phosphorus fractions in some representative soils. J. Soil Sei., 9, 1958, 109—110.
[5] H e r m a n R., L e d e r l e : B estim m ung laktalöslicher Phosphorsäure in Boden m it „Photorex”.Bodenkunde und Pflanzenernähr., 26, 7, 1954, 105— 142. [6] H u f f m a n E. O.: Reactions of phosphate in soil. Recent research by TVA
The Fertilizer Society, Proc. 71, London 1962.
[7] J a c k s o n M, L.: Soil chem ical analysis. Eaglywood Cliffs. 1960.
[8] L i n d s a y W. L., T a y l o r A. W.: Phosphate reaction products in soil and their availability to plants. Trans. 7th Int. Congr. Soil Sei. M adison Wise. USA 1960, IV, 73, 580—589.
[9] S t r e b e у к о P.: W pływ reakcji gleby na przyswajalność różnych form k w a su fosforowego. Roczn. Nauk Roln. i Leśn., 34,. 1935, 152—202.
[10] S c h o f i e l d R. K.: Can a precise m eaning be given to “availab le” soil phosphorus? Soil and Fertil., XVIII, 1955, 373—375.
S . M P S K A L , M . P E T R O V I C
BEOBACHTUNGEN DES VON SUPERPHOSPHAT HERKÖMMLICHEN UND VON DEN PFLANZEN NICHTGENUTZTEN PHOSPHORS
IM BODEN AUF GRUND LANGJÄHRIGER FELDVERSUCHE
L e h r s t u h l f ü r L a n d w i r t s c h a f t l i c h e C h e m i e , L a n d w i r t s c h a f t l i c h e H o c h s c h u l e , W a r s z a w a
Z u s a m m e n f a s s u n g
Auf dem V ersuchfeld in Skierniew ice (podsolige lehm ige Sandböden) w urden seit dem Jahre 1923 w erschiedene D üngem ittel angewandt, w obei man den Einfluss von Stickstoff, Phosphor und K ali auf den Ertrag von Pflanzen untersuchte.
Nach 40 Jahren wurde eine A nalyse der Böden durchgeführt, um festzustellen, inw iefern das Düngen m it Superphosphat und Kalk den Gehalt an verschiedenen Phosphaten in der Pflugschicht des Bodens beeinflusst haben.
Es w urde bestim mt: Gesamtphosphor, lose gebundene Phosphate, nichtokklu- dierte A lum inium - und Eisenphosphate, sow ie Calciumphosphate, leicht aulnehm barer
Phosphor m it H ilfe der Egner-Riehm Methode, ferner das chem ische P otential von Phosphaten nach der M ethode von Schofield.
Das Düngen m it Superphosphat im V erhältnis 30 kg P205 pro Hektar verursachte eine Steigerung des Phosphatgehaltes im Boden um 30— 100%. Auch der G ehalt an schwach gebundenen Phosphaten, sowie an A lum inium - und Eisenphosphaten, der Gehalt des nach der Egner-Riehm M ethode bestim m ten Phosphors, sow ie nach Schofields M ethode bestim m ten Phosphatpotentiale w aren auf dem m it Super phosphat gedüngten Boden hoher. Der Gehalt an Calcium phosphaten steigerte
sich infolge der D üngung nur sehr w en ig oder auch gar nicht. D er Gehalt an Alum inium phosphaten stieg jedoch zweifach. A uf stark sauren Böden, bei A nw en dung von Am m onium sulfat, vergrösserte sich der G ehalt an Eisenphosphaten fast zw eifach.
D er Kalkdünger w irkte sich so aus, dass die Phosphorm enge auf den m it K alk gedüngten Parzellen im allgem einen kleiner war, dagegen w aren die M enge der schw achgebundenen Phosphate und der nach der Egner-R iehm M ethode bestim m ten Phosphate, sow ie die Phosphatpotentiale der Böden v iel grö sser. D er G ehalt an Alum inium phosphaten auf den Parzellen NPK w ar grösser als auf den CaNPK Parzellen. Ganz ähnlich gestaltete sich der Gehalt an E isen phosphaten. Der Gehalt an Calcium phosphaten w ies um gekehrte G estaltung auf.
S . M O S K A L , M . P E T R O V I C
LE PHOSPHORE NON-UTILISÉ PAR LES PLANTES DA NS LE SOL, PROVENANT DE FERTILISATION AU MOYEN DE SUPERPHOSPHATE.
RESULTATS DE LONGUES ANNÉES D ’EXPÉRIENCES D ANS LE CHAMP
C h a i r e d e C h i m i e A g r i c o l e à l ’U n i v e r s i t é A g r o n o m i q u e d e V a r s o v i e R é s u m é
D epuis 1923 divers systèm es de fertilisation furent m is en oeuvre dans un champ d’essais à S kierniew ice (sol alcalin, argiles sablonneux) afin de constater l ’influence exercée sur les récoltes par l ’azote, le phosphore et le potassium . Après 40 ans, les analyses furent effectu ées pour étaclic (influence du superphosphate et du chaulage sur la teneut de la couche arable en phosphates du sol. Le phosphore total fut determine, ainsi que les phosphates libres, les phosphates d’alum inium et de fer non-occlus, les phosphates de calcium, le phosphore aisém ent accessible par la m éthode Egner-Riehm , et le potentiel chim ique des phosphates d’après Schofield.
La fertilisation par superphosphate à raison de 30 kg de P205 par hectare annuellem ent a determ ine une augm entation de 30— 100% de la teneur du sol en phosphore total. La teneur en phosphates libres, phosphates d’alum inium et de fer, ainsi qu’en phosphore determ ine d’après la m éthode Egner-Riehm et le potentiel phosphatique du sol d’après Schofield avait augm enté dans les sols fertilisés au superphosphate. La teneur en phosphates de calcium augmenta insensiblem ent, au point après le m êm e engrais. La teneur en phosphates d’aluminium a pourtant augm enté de 2 fois. Dans un sol fortem ent acide où fut appliqué le sulfate d’am monium, la teneur en phosphate de fer a doublé.
Le chaulage a pour résultat la dim inution du phosphore total dans les champs d’essais et une augm entation de la quantité de phosphates libres, de phosphates
88 S. Moskal, M. Petrovic
determ ines suivant la m éthode Egner-Riehm et du potentiel phosphatiques dans le sol. La teneur en phosphates d’alum inium dans les champs d essa is fertilisés à Г NPK, était plus grande que dans les champs d’essais au CaNPK. La teneur en phosphates de fer était pareille inversem ent à celle des phosphates de calcium.
S . M O S K A L , M . P E T R O V I C
LOSY NIE WYKORZYSTANEGO PRZEZ ROŚLINY FOSFORU Z SUPERFOSFATU W GLEBIE NA TLE DŁUGOLETNICH
DOŚWIADCZEŃ- POLOWYCH
Z a k ł a d C h e m i i R o l n i c z e j , S G G W W a r s z a w a
S t r e s z c z e n i e
Na polu D ośw iadczalnym w Skierniew icach (gleba bielicow a p iaszczysto-gli- niasta) od roku 1923 stosowano różne nawożenie badając w p ływ stosow ania azotu, fosforu i potasu na plony roślin. Po 40 latach przeprowadzono analizy gleb w celu w yjaśnienia, jak w pływ ało nawożenie superfosfatem i w apnow anie na zaw artość różnych fosforanów w glebie w w arstw ie ornej. Oznaczono fosfor ogółem, fosforany glinu i żelaza, fosforany wapnia, fosfor łatw o dostępny metodą Egnera-R iehm a i po ten cjał chem iczny fosforanów w g Schofielda.
N aw ożenie superfosfatem w ilości 30 kg P205 na hektar rocznie spowodowało 30— 100°/o zw yżkę zaw artości fosforu ogółem w glebie. Również zawartość fosfo ranów luźno zw iązanych oraz fosforanów glinu i żelaza, a także fosforu oznaczone go m etodą Egnera-Riehm a i potencjał fosforanow y gleb w g Schofielda były w ięk sze na glebie nawożonej superfosfâtem . Zawartość fosforanów w apnia w glebie zw iększyła się nieznacznie lub w ogóle się nie zw iększyła pod w pływ em tego n a wożenia. Zawartość fosforanów glinu wzrosła jednak 2-krotnie. Na glebie silnie kwaśnej, gdzie stosowano siarczan amonu (AFin) zw iększyła się praw ie dw ukrot nie zawartość fosforanów żelaza.
W apnowanie działało w ten sposób, że ilość fosforu ogółem na poletkach w ap nowanych była w yraźnie niższa, a ilość fosforanów luźno związanych, fosforanów oznaczonych m etodą Egnera-Riehm a i potencjał fosforanow y gleb były dużo w ięk sze. Zawartość fosforanu glinu na poletkach NPK na w szystkich polach była w ięk sza niż na poletkach CaNPK. Podobnie k ształtow ała się zawartość fosforanów że laza. Zawartość fosforanów wapnia układała się odwrotnie.
с. м о с к а л ь , м. П Э Т Р О В И Ч Ь УЧАСТЬ НЕИСПОЛЬЗОВАННОГО РАСТЕНИЯМИ ФОСФОРА СУПЕРФОСФАТА В ПОЧВЕ НА ФОНЕ ДЛИТЕЛЬНЫХ ПОЛЕВЫХ ОПЫТОВ К а ф е д р а А г р о х и м и и В а р ш а в с к о й С е л ь с к о х о з я й с т в е н н о й А к а д е м и и Р е з ю м е На опытном поле Скерневице (подзолистая песчаносуглинистая почва) от 1923 года применяют минеральные удобрения, исследуя влияние вносимого азота, ф осф ора и калия на урож ай растений. После 40 лет проведен был анализ
почвы чтобы выяснить как повлияло удобрение суперф осф атом и известью на содерж ание различных ф осф атов в пахотном горизонте почвы. Определяли валовой ф осф ор, подвижные фосфаты , неокклюдированные ф осф аты полутор ных окислов, ф осф аты кальция, доступный ф осф ор по методу Эгнера-Рима и химический потенциал фосфатов по Ш офильду. Удобрение суперфосфатом в годичной дозе 30 кг Р2О5 на гектар повышало содерж ание валового ф осф ора в почве на 30 — 100°/о. Содержание обменных ф о с фатов как и фосфатов алюминия и ж елеза, а такж е ф осф ора определенного по Эгнеру—Риму и ф осф атны й потенциал почв по Ш офильду были выше в поч вах удобряемых суперфосфатом. Под влиянием этого удобрения повысилось не значительно или вовсе не повышалось содерж ание фосф атов кальция. Содер ж ание фосф атов алюминия возросло 2-кратно. На сильно кислой почве, в ва рианте где был применен сернокислый аммоний, содерж ание ф осф атов ж елеза повысилось почти 2-кратно. Действие известкования проявилось в следующем: на известкованных д е лянках количество валового ф осф ора было отчетливо ниже, но количество подвижны х фосфатов, фосф атов определенных по методу Эгнега—Рима и ф о с фатный потенциал почв, были на много выше. С одержание фосф атов алюми ния на делянках NPK всех опытных полос было выше чем на делянках CaNPK. Аналогично формировалось содерж ание фосфатов ж елеза. Обратную зависи мость обнаружено в содержании фосф атов кальция.
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