Jean Diatta

Competitivity, selectivity, and heavy metals-induced alkaline cation displacement in soils

Abstract The simultaneous incorporation of heavy metals into the soil is still a matter of great concern. Interaction (competitive sorption) between these metals and the soil solid phase may result in a deterioration of soil quality which relies basically on amounts of alkaline cations saturating soils sorptive complex. Results of this study indicate that Pb, Cu, C d, and Zn have induced solution pH decreases which were more intensive at highest metal loading rates. Partition parameters (Kd)-based sequences showed that Pb and Cu were more competitive than Cd and Zn and the overall selectivity sequence followed: Pb > Cu > Cd > Zn. Metal loadings and their competitive sorption have led to a strengthened displacement of alkaline cations (i.e. Ca2+, Mg2+, K+, Na+), especially of Ca2+ as a factor “stabilizing” soil sorptive complex. Such metals impact jointly with soils acidification are of great environmental concern since tremendous amounts of alkaline cations (especially Ca2+) may be potentially leached out, irrespective of the degree of soil contamination, as evidenced in the current study. High and positive ΔG values implied that the studied soils were characterized by generally low concentrations of exchangeable potassium which required high energy to get displaced (desorbed). Further studies on heavy metal uncontaminated or contaminated areas should be undertaken to provide with data which should be used for predictions on changes related to soil buffering capacity as impacted by heavy metal inputs.

FERTILIZER CONSUMPTION PATTERNS IN CENTRAL EUROPEAN COUNTRIES – EFFECT ON ACTUAL YIELD DEVELOPMENT TRENDS IN 1986-2005 YEARS – A COMPARATIVE STUDY OF THE CZECH REPUBLIC AND POLAND

This study outlines the long-term trends of fertilizers consumption in the Czech Republic and Poland and their impact on actual yield development of main crops for the period 1986-2005. In both countries dynamics of N, P, K fertilizers use showed analogical trends. Based on amounts and nutrient ratio of consumed fertilizer, as expressed as P2O5:N and K2O:N ratios, there were distinguished three phases of fertilizers use: i) high ii) collapse and iii) restoration/stagnation. The stagnation phase was attributed for P and K in the Czech Republic. The observed yield depressions since the 1990s reflect changes in farmer’s long-term fertilization and has been termed a temporary yield gap (TYG). However, its long-term existence negatively affects crop production stability. The development of new, country specific strategies in the management of P and K, i.e. adopted to natural soil fertility conditions, is a main goal of present agriculture of both countries, compared in the presented study.

Constraints and Solutions to Maintain Soil Productivity: A Case Study from Central Europe

Yield improvement in old farming areas has been recently recognized as a practice that will further increase crop production. One of the most important old farming areas is Europe (EU 27), which accounts only for 4% of World agricultural area, but at the end of the 20th century produced 14% of total cereals and 20% of meat (Olesen & Bindi, 2002). At present, Europe has a very diversified level of agriculture development. European agriculture is currently divided into eight agricultural regions based on natural and socio-economic factors. Two of them, i.e., the North Eastern region comprising Czech Republic, Slovak Republic, Poland and the South Eastern region, including Bulgaria, Hungary, Romania, Bosnia & Herzegovina, Croatia, Macedonia, Slovenia, Serbia and Montenegro, are of special interest to this chapter. Due to the “planned economy” experiment, which took place from the end of the 1940s to the end of the 1980s, these two regions are generally classified as Central Europe (CE). This macro-region is considered nowadays as one of the most important future producers of cereals (Rosegrant et al., 2001; Kelch & Osborne, 2001).

Evaluation of fertilizers solubility and phosphate release in slightly acidic arable soil

ABSTRACT The geochemical reactivity of single superphosphate (SSP), triple superphosphate (TSP), phosphate rock (PR), partially acidulated phosphate rock (PAPR) and potassium dihydrogen phosphate (KH2PO4) was evaluated in an incubation trial. The soil was Anthrosols, Ap horizon (Sandy loam). Solubility equilibrium of phosphates was calculated by phosphate (PPot = logH2PO4 – pH) and calcium (CaPot = logCa + 2pH) potentials. Next, activity ratio (AR°) and Woodruff potential (ΔF) were considered for estimating phosphate dynamics in the soil. Data showed that phosphate potentials stressed on significant solubility process and varied accordingly to the rates of the fertilizers: −5.50, −4.81, −4.47 and −4.09 for 0, 50, 100 and 150 kg P ha−1. The values of the Woodruff potential (ΔF) varied widely from −1929 to 8573 cal mol−1, i.e., from marginal supplying power in the case of the control treatment to very high supplying power for the TSP (Triple superphosphate). These findings are of practical value for the following reasons: TSP and KH2PO4 are recommended for quick and high P supply to plants; SSP and PAPR for moderate supply and finally PR for slow and low supply. Phosphorus efficiency should be treated with priority particularly for areas with intensive cropping and susceptibility to runoffs.

Humus stock degradation and its impact on phosphorus forms in arable soils – a case of the Ukrainian Forest-Steppe Zone

Abstract Soil humus degradation strengthens nutrient mining, especially phosphorus. This study was carried out on the Ukrainian Forest-Steppe Zone (UFSZ). A total of 21 soil profiles have been investigated: 11 Phaeozems, 6 Luvisols, and 4 Chernozems. Soils were tested for particle size distribution, calcium carbonate (CC), pH, and organic carbon (Corg). The evaluation of humus degradation as a reason of P depletion was performed based on indicators such as Humus Stock Gap (HSG), Humus Stability Index (S), and Yield Gap/Gain (YG/G). In order to evaluate the degree of P depletion, total phosphorus (Ptot) and its five fractions: water soluble – PH2O, exchangeable – PEX, bound to Fe and Al – PFe/Al, bound to Ca – PCa, and residual P – Pres, have been determined. Data revealed that in 14 of 21 investigated soils, S indices were below the threshold its value of nine, considered as the balanced content of humus with respect to soil texture. Next, in 11 of 21 cases, the negative humus balance indicates the yield gap in Phaeozems and Chernozems. The first three P pools (PH2O, PEX and PAl/Fe) in Phaeozems were exhausted, constituting less than 10% of the Ptot. In Phaeozems, PAl/Fe, in Luvisols, PEX, and in Chernozems, PH2O fractions were basic indicators of available P status. Their pools were directly or indirectly controlled by PCa. Humus content in Phaeozems and Chernozems revealed as the key factor impacting both total P and/or its available resources. Amelioration of P depletion requires efforts oriented on restoration of soil humus stock, concomitant with P fertilization.