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“The availability of calcium dihydrogen phosphate fertilization for lolium, soybean and lupine.”

Written report for the course “Radio-isotopes in plant nutrition” in 2007/08 by DürrN and WeberV

1    Abstract
Plants fertilized with different P-sources can have different ability to grow. It depends on the availiability of P from the fertilizer.
In a pot experiment we compared the growth of ray grass, soybean and white lupine fertilized with Ca(H2PO4)2 and without any fertilizer. The plants grew for 8 weeks and were then harvest for different measurements. We used two different methodes (L-Value and E-Value) to measure P availability.
With the isotope exchange kinetic experiment we measured the P exchangeability and with the Malachit green colorimetry method we determined P concentration.

2    Introduction
P is a very important macronutritent for the growth of plants. It usually is available for the plant as soluble phosphate anions. The amount of available P for a maximum plant growth in some soil types is limited and a P fertilizer often has to be added.
A possible P-source is Ca(H2PO4)2. For our experiment it was of interest how Ca(H2PO4)2 is available for ray grass, soybean and white lupine. White lupine has quite a different root system than the two other plants. It is caracterized as cluster roots which releases big amount of citrates (Keerthisinghe et al. 1998, Braum and Helmke 1995). This is quite beneficial for the plant as it enables to uptake P, which is unavailable for other plants.
To see the availability of P for the plants, we can use two methodes to measure the isotopically exchangeable P. The E-Value is the amount of ion that can arrive in the solution after any given time (Pyper et al., 2006). Another methode (L-Value) is to label the soil with 33P and measure the shoot activity in the plant (Bühler et. al., 2003). With those two methodes, which we used for our experiment, we could compare P uptake of the three different plants with and witout fertilizer.


Braum S.M and Helmke P.A., 1995, White lupin utilizes soil phosphorus that is unavailable to soybean, Plant and Soil, 176, 95-100

Bühler S., Oberson A., Sinaj S., Friesen D.K., Frossard E., 2003, Isotope methods for assessing plant available phosphorus in acid tropical soils, European Journal of Soil Science, September, 54, 605–616

Keerthisinghe G, Hocking P J, Ryan P R and Delhaize E, 1998, Effect of phosphorus supply on the formation and function of proteoid roots of white lupin (Lupinus albus L.). Plant Cell, Environ., 21, 467–478

Pieter Pypers, Liesbeth Van Loon, Jan Diels, Robert Abaidoo, Erik Smolders, Roel Merckx, 2006, Plant-available P for maize and cowpea in P-deficient soils from the Nigerian Northern Guinea savanna – Comparison of E- and L-values, Plant and Soil, 283, 251–264

February 3rd, 2008
Topic: Crop Science, Plant nutrition Tags: None

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