Acidic Agricultural Soil Research Articles

Subproducto industrial como enmienda cálcica al terreno

El hidróxido de calcio [Ca(OH)2], un subproducto de la producción de acetileno, tiene buen potencial como fuente de encalado para suelos agrícolas ácidos. Inicialmente este material contiene un 80% de humedad, la que disminuye a aproximadamente 50% una vez asentado en la charca de recolección. El Ca(OH)2 seco al aire (2.63% humedad), molido y pasado por un cedazo de 300 µm mostró una equivalencia a CaCO3 puro de 120%. El CaCO3 comercial (1.53% humedad) mostró una equivalencia a CaCO3 puro de 84%. Las fuentes de encalado se evaluaron en estudios de laboratorio utilizando cuatro suelos ácidos: Corozal (Ultisol), Mariana (Inceptisol), Bayamón (Oxisol) y Alonso (Ultisol). El residuo industrial Ca(OH)2 fue tan efectivo como el CaCO3 en neutralizar la acidez de estos suelos. La aplicación de 8.0 meq/100g de las fuentes de encalado aumentó el pH del suelo Mariana de 4.65 a 6.07, Corozal de 4.13 a 4.92 y Alonso de 4.74 a 6.48. En el caso del suelo Bayamón, la aplicación de 8.0 meq/100g de CaCO3 aumentó el pH de 4.39 a 6.65, mientras que la misma aplicación en forma de Ca(OH)2 aumentó el pH a 6.92. El aluminio intercambiable de los suelos Mariana, Bayamón y Alonso alcanzó valores cercanos a cero cuando los valores de pH estaban entre 6.0 y 6.3. En el suelo Corozal se observó una reducción en Al3+ intercambiable de 934.37 a 269.79 mg/kg con un aumento en pH de 4.13 a 4.92. En un experimento de incubación a corto plazo (5 días) el Ca(OH)2 neutralizó en menos tiempo la acidez de los suelos Mariana, Bayamón y Alonso que el CaCO3. Las muestras tratadas con 8.0 meq de Ca(OH)2 alcanzaron valores de pH cercanos a 6.00 al día siguiente de la aplicación. Sin embargo, con la aplicación de CaCO3 se observaron valores similares de pH al segundo y tercer día de incubación.

Dry Flue Gas Desulfurization Byproducts as Amendments for Acid Agricultural Soils

Dry Flue Gas Desulfurization Byproducts as Amendments for Acid Agricultural Soils

Sorption behavior of a new acidic herbicide in soils

The sorptive behavior of the experimental herbicide quinmerac (7-chloro-3-methyl-quinoline-8-carboxylic acid) was investigated in soils of different organic carbon content. Distribution coefficients are low (K d = 0.03 - 12 mL g −1) and are mainly determined by the soil organic carbon content. The adsorption mechanism operating in neutral to slightly acid agricultural soils is supposed to be cation bridging with the anionic form of quinmerac. Under acid conditions (pH 〈 5.2) the predominating sorption mechanism is hydrophobic interaction. Therefore soil pH and cationic composition are also major factors determining the sorptive capacity of soils for quinmerac. Adsorption kinetics, equilibrium adsorption and desorption isotherms were determined in batch experiments. Sorption kinetics were investigated at various times from 15 min to 96 hours. A two-step sorption behavior with time was found for the anionic form indicating two types of sorption mechanisms or sorption sites. Equilibrium for the first type was reached at a time-scale of minutes and for the second type after 24 hours. Adsorption isotherms were determined for two soil/solution ratios 1 5 and 1 3 . Alteration of the adsorbent concentration exerted a strong influence on the adsorption isotherms. An increase of sorption was found with increasing adsorbent concentration. Under natural soil conditions sorption is therefore expected to be higher compared to the batch experiments. Desorption isotherms were obtained using the consecutive desorption method. Desorption hysteresis was not observed which indicates weak interactions. Implications of the results for the movement of quinmerac under field conditions and for models describing transport are discussed.

Symbiotic nitrogen fixation of Rhizobium (Galega) in acid soils, and its survival in soil under acid and cold stress

Goat's rue (Galega orientalis) is a potential perennial forage legume for northern temperate acid soils. Greenhouse experiments were performed to compare symbiotically nitrogen fixing goat's rue with plants receiving mineral nitrogen in five different acid soils. Soil acidity had the same effect on yields of symbiotically grown plants as on plants receiving mineral nitrogen, suggesting that the acid sensitivity of the symbiosis was not limiting plant growth, even under very acidic conditions. The survival of an antibiotic resistant Rhizobium (Galega) strain in acid soil and freezing conditions was also studied. The survival of the bacteria was not affected at 15°C, when the pH of the soil (measured in 0.01M CaCl2) was 5.2 or 4.9. In pH 3.4, and after freezing to −5°C, the population density decreased from 3×108 to 1×105/g in a few weeks. It is concluded that goat's rue, its symbiotic nitrogen fixation and R. (Galega) are tolerant of moderately acid agricultural soils, but that harsh winters may reduce bacterial numbers in the soil.

Comparison of several lime requirement methods for agricultural soils in Pennsylvania

Abstract Two new double‐buffer methods have been proposed recently by Yuan and McLean, et al. to more accurately predict the lime requirement (L.R.) in sandy, low buffer capacity soils and in low L.R. soils respectively. The L.R. of 20 typical acid agricultural soils in Pennsylvania were determined by a 6 month incubation with a series of CaCO3 concentrations. These incubation L.R. values were then compared with the two double buffer methods as well as the more established SMP, Woodruff, Adams‐Evans, BaCl2 triethanol amine (BaCl2‐TEA) and Ca(OH)2 titration methods to determine which of these methods most accurately predicted the true, (CaCO3‐incubation), L.R. of these soils. All methods were very well correlated with the incubation L.R. (r = 0.919 to 0.987) but only the SMP single buffer was reasonably accurate in predicting the incubation L.R. for both low and high L.R. soils. A modification in recomnendation was proposed to eliminate the slight SMP underestimation of L.R. for low L.R. soils. The two double buffer methods, BaCl2‐TEA and the Adams‐Evans method overestimated the L.R. for low L.R. soils and underestimated lime needs for high L.R. soils. The Woodruff and Ca(OH)2 titration methods both underestimated the L.R. of high (>10 meq CaC03/100g soil) L.R. soils by more than 50%.