(Home) (Contact me) (How can I help?)
(Research) (Resume) (Teaching)


PROF. LUÍS I. PROCHNOW

SOIL FERTILITY AND FERTILIZER SPECIALIST



ABSTRACTS

 

Abstract 01
Abstract 02

 


 

Prochnow L I, Kiehl J C and Raij B van. 1998. Plant availability of phosphorus in the neutral ammonium citrate fraction of Brazilian acidulated phosphates. Nut. Cyc. Agr., 52:61-65.

Abstract

In Brazil, where the rock phosphates are high in impurities, no attempt has been made to evaluate the P supplying efficiency of the neutral ammonium citrate fraction (NAC) of P fertilizers, or to verify if the NAC + H2O extraction solution (AOAC) is satisfactory for estimating the P availability. To attain these objectives, a greenhouse experiment was carried out with samples of a Typic Hapludox soil. Four acidulated phosphates obtained from Brazilian raw materials were studied; monocalcium phosphate p.a. [Ca(H2PO4)2.H2O] was included as a standard source of P, as well as leached samples containing no water-soluble P. The fertilizers were thoroughly mixed with the whole soil in the pots or with only 1% of its volume, at the rate of 50 mg kg-1 of P, soluble in NAC + H2O. Corn plants (Zea mays , L.) were grown for 35 days and the amounts of dry-matter and P accumulated in plant tops were determined. Increasing the amount of cationic impurities in the raw materials decreased the concentration of water-soluble P, NAC + H2O soluble P and water-soluble P/NAC + H2O soluble P ratio of the fertilizers obtained. The P in the NAC fraction was not as much available to plants as in the NAC + H2O fraction or in pure MCP. The great variation found in dry matter (5.4 to 17.1 g pot-1) and in P uptake (6.3 to 22.2 mg pot-1) indicates that the AOAC method is not an adequate index for evaluating the P availability of fertilizers with high amounts of cationic impurities.

 


 

Prochnow L I, Pismel F S, Cantarella H, Vitti G C, Kiehl J C and Corrente J E. 1998. Use of ion-exchange resin to evaluate the bioavailability of sulfur in the soil. Comm. Soil Sci. Plant Anal., 29:1833-1841. (Greenhouse study with maize)

Abstract

Samples of 22 soils of the State of São Paulo, Brazil, were collected from the 0-20 cm layer, dried, sieved, and analyzed for sulfur (S) utilizing the following extracting solutions: (a) calcium phosphate [Ca(H2PO4)2, 500 mg P L-1 in 2.0 mol acetic acid (HOAc) L-1, (b) 1 mol ammonium chloride (NH4Cl) L-1, (c) 0.5 mol ammonium acetate (NH4OAc) in 0.25 mol HOAc L-1, (d) ion-exchange resin - Resin 1 - (2.5 cm3 of soil + 2.5 cm3 of resin in water and further extraction with 50 mL 0.8 mol NH4Cl L-1 in 0.2 mol hydrochloric acid (HCl) L-1, (e) ion-exchange resin - Resin 2 - (5.0 cm3 of soil + 5.0 cm3 of resin in water and further extraction with 25 mL 0.8 mol NH4Cl L-1 in 0.2 mol hydrochloric acid (HCl) L-1, (f) ion-exchange resin - Resin 3 - (5.0 cm3 of soil + 2.5 cm3 of resin in water and further extraction with 25 mL 0.8 mol NH4Cl L-1 in 0.2 mol hydrochloric acid (HCl) L-1. Amounts of 2 kg of each soil, in four replicates were limed in order to reach a base saturation of 70% of the cation exchange capacity (CEC). After a period of incubation of 30 days all nutrients, except S, were added to the soil and corn seeds were planted. Plant tops were removed after 70 days, dried at 50oC, weighed, and analyzed for S determination. The correlation between the bioavailable S in the soil and the yield of dry-matter or S uptake was best represented by the linear or the X1/2 models. The coefficient of determination varied from 0.56 (Resin 1) to 0.82 (NH4OAc). Resins 2 and 3 methods showed good efficiency (R2 from 0.63 to 0.79), and can be utilized in the evaluation of S bioavailability in soils.