Journal of Agricultural Science and Technology
Journal of Agricultural Science and Technology
JAST
Agriculture
http://jast.modares.ac.ir
1
admin
1680-7073
2345-3737
10.22034/jast
en
jalali
1384
10
1
gregorian
2006
1
1
8
1
online
1
fulltext
en
Contribution of Inorganic Phosphorus Fractions to Plant
Nutrition in Alkaline-Calcareous Soils
To evaluate the relationships between soil inorganic phosphorus P (Pi) fractions, the soil P test and plant parameters such as plant P uptake, dry matter yield, tissue P concentra-tion and relative yield, glasshouse experiments and chemical analyses were conducted on 13 calcareous soils from six agricultural and seven adjacent bushland (virgin soil) sites. Four rates of P (0, 15, 30, 60 mg/kg soil) were applied as reagent-grade KH2PO4 to the soils in a randomised complete block design with three replications. Perennial ryegrass (Lolium perenne cv. Roper) was grown and forage was harvested five times over a period of 210 days. Successive harvesting resulted in the depletion of plant available P as meas-ured by NaHCO3-extractable P, which coincided with the decrease in the plant dry matter yield and P uptake. After five harvests, the order of reduction in Pi fractions induced by cropping without added P was Ca10-P>Al-P>Ca2-P>Ca8-P>occluded-P>Fe-P for the vir-gin soils and Ca2-P>Al-P>Ca10-P>Ca8-P>Fe-P>occluded-P for the agricultural soils. The order of abundance of Pi fractions for P treated-soils was non-occluded Al and Fe phos-phate (Al-P+Fe-P)>secondary Ca-bound P (Ca2-P+Ca8-P)>acid-extractable P (Ca10-P)>occluded-P for both virgin and agricultural soils. Although a marked proportion of added P was transformed into less soluble Al and Fe phosphates, successive harvesting had depleted considerable percentages of these fractions. Highly significant (p<0.001) re-lationships were found for P uptake vs. Olsen-P, P uptake vs. Pi fractions (Ca2-P, Ca10-P, Al-P, Ca8-P, Fe-P) and Olsen-P vs. Pi fractions. NaHCO3-extractable P seems to be ade-quate for evaluating plant available P in calcareous soils. However, the closer relationship for the Fe-P fraction vs plant P uptake than for Olsen-P versus plant P uptake indicates that NaHCO3 may not provide the best estimate of plant available P for calcareous soils. Using stepwise regression analysis, it was found that the Ca2-P fraction was most predic-tive of P uptake (60%), total dry matter (68%), relative yield (74%) and Olsen-P (69%), followed by the Fe-P fraction.
Calcareous soils,Availability,Inorganic P fractions,NaHCO3-extractable P,Plant P uptake
77
89
http://jast.modares.ac.ir/browse.php?a_code=A-10-1000-1003&slc_lang=en&sid=23
A.
Samadi
A.
Samadi
100319475328460045496
100319475328460045496
Yes
Department of Soil Science, Urmia University, P. O. Box: 165, Urmia, 57134, Islamic Republic of Iran.
Department of Soil Science, Urmia University, P. O. Box: 165, Urmia, 57134, Islamic Republic of Iran.