Rafael Espejo

Carbon Dioxide Emission Rates and β-Glucosidase Activity in Mediterranean Ultisols Under Different Soil Management

Abstract Soil respiration is the second-largest terrestrial carbon flux, and it has shown to be deeply affected by soil management. This article reports a field and laboratory study comparing CO2 emission rates from the soil surface and &bgr;-glucosidase activity in Mediterranean Ultisols from the Cañamero raña surface (continental detritic formations from southwest Spain) under different soil management conditions and vegetation cover: 1) soil in a cork oak grove, the climax vegetation of the studied raña surface; 2) soil in a Cistus scrubland with a 100% cover, uncultived for the past 45 years; 3) soil in a crop field that has been uncultivated for the past 35 years and with 55% of the shrub cover dominated by Cistus crispus L. and the rest covered by pasture; 4) soil in a degraded pastureland; and 5) soil in an olive grove that has been continuously cultivated for the past 65 years. We made a comparative assessment of aerobic activity in each of the soils at different times of the year. The level of degradation of natural vegetation, and therefore also the organic matter content, which decreased from Areas 1 to 5, affected the rate of CO2 emission from the soil surface. This rate was also affected by soil water content, soil temperature, and the predominance of Cistus ladanifer L. in the soil vegetation cover. In the case of the Olea europaea L. grove soil, the CO2 emission rate notably increased during autumn in years of high fruit production as a result of increased root respiration. &bgr;-Glucosidase activity was mostly, and positively, affected by organic matter content and also was negatively affected by the predominance of C. ladanifer in the vegetation soil cover.

No tillage and liming reduce greenhouse gas emissions from poorly drained agricultural soils in Mediterranean regions

No tillage (NT) has been associated to increased N2O emission from poorly drained agricultural soils. This is the case for soils with a low permeable Bt horizon, which generates a perched water layer after water addition (via rainfall or irrigation) over a long period of time. Moreover, these soils often have problems of acidity and require liming application to sustain crop productivity; changes in soil pH have large implications for the production and consumption of soil greenhouse gas (GHG) emissions. Here, we assessed in a split-plot design the individual and interactive effects of tillage practices (conventional tillage (CT) vs. NT) and liming (Ca-amendment vs. not-amendment) on N2O and CH4 emissions from poorly drained acidic soils, over a field experiment with a rainfed triticale crop. Soil mineral N concentrations, pH, temperature, moisture, water soluble organic carbon, GHG fluxes and denitrification capacity were measured during the experiment. Tillage increased N2O emissions by 68% compared to NT and generally led to higher CH4 emissions; both effects were due to the higher soil moisture content under CT plots. Under CT, liming reduced N2O emissions by 61% whereas no effect was observed under NT. Under both CT and NT, CH4 oxidation was enhanced after liming application due to decreased Al(3+) toxicity. Based on our results, NT should be promoted as a means to improve soil physical properties and concurrently reduce N2O and CH4 emissions. Raising the soil pH via liming has positive effects on crop yield; here we show that it may also serve to mitigate CH4 emissions and, under CT, abate N2O emissions.

Comparative Analysis of Corrective Action of Various Liming and Gypsum Amendments on a Palexerult

A Palexerult soil from the Pliocene raña formations in northern Spain was used to conduct acidity correction tests with limestone, gypsum rock and sugar foam waste under laboratory conditions. The soil was reconstructed in methacrylate columns that were studied over a five-month period. The pH and exchangeable bases in the leachates, obtained by applying an amount of water equivalent to the mean rainfall of the area from which the soil was collected, were measured under laboratory conditions along a five-month period. At the end of these tests, three different samples (one from the A horizon and two from as many different depths in the AB horizon) were used to determine the pH in water and KCl, as well as the exchangeable bases and aluminum (Al), effective cation-exchange-capacity (CECe) and available phosphorus (P), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn). Data were statistically analyzed by using a multivariate linear general (MLG) model with two factors (treatment type and sampled soil sub-horizon). The results revealed limestone and sugar foam waste to be more effective than gypsum in suppressing Al3+ toxicity in the A horizon; in fact, they provided the best VeAl values and Al/Ca ratios, and also the greatest pH increases. By contrast, gypsum rock proved more efficient in the sub-surface horizons. All treatments, but particularly that with gypsum, decreased the exchangeable potassium content. This amendment caused no magnesium losses as it contained large amounts of it in its composition; however, it resulted in substantial losses of Fe and Mn (particularly through leaching from the A horizon) as a result of the increased acidity produced. Sugar foam waste performed similarly to limestone as regards corrective capacity.

Aluminum, Fluorine, And Sulfate Species Dynamics In The Soil Solution Of A Palexerult Amended With Lime And Gypsum By-products

Changes in the activities of aluminum (Al), fluorine (F), and sulfate (SO42−) species in the soil solution of a plinthic Palexerult after amendment with various lime and gypsum by-products [viz. sugar foam waste (SF), phosphogypsum (PG), and red gypsum (RG)] were studied in successive extracts of the soil solution from the Ap and AB horizons, which were placed in leaching columns, over two leaching cycles equivalent to two precipitation cycles in the soils originating area. Although SF affected mainly the Ap horizon, the gypsum amendment effects were more complex. Thus, SF decreased the activity of Al3+ and Al(OH)2+ in the soil solution from the Ap horizon. In contrast, SF affected the AB horizon, where it reduced the activity of Al3+ and significantly increased that of Al(OH)2+-only by the end of the second leaching cycle, however. Similar to SF, PG was found to affect the activities of Al3+, Al(OH)2+, and Al(OH)2+ species (particularly the first) in the soil solution from Ap; this by-product increased the activity of AlFx(3−x) ion pairs but not that of Al-SO4 pairs. On the other hand, RG significantly increased the activity of Al3+ in the first water extract from Ap and AB and also that of the AlSO4+ pair in the first four water extracts but only that of AlF2+ among Al-F pairs. The two gypsum amendments had similar effects on the AB horizon. Thus, they increased the activity of AlSO4+ and Al(SO4)2−, which peaked in the second soil-water extraction, and that of AlFx(3−x) pairs. Sugar foam waste significantly increased the Ca-Al balance in the Ap horizon, as did PG, albeit only in the first three soil-water extracts. The gypsum amendments also increased Ca-Al balance in AB, and so did SF after the second soil-water extract.

SOIL SOLUTION DYNAMICS INTO PALEXERULT AMENDED WITH GYPSUM AND LIME BY-PRODUCTS: A LABORATORY TEST

A laboratory experiment involving the use of leaching columns reproducing the topmost part of a clayey-skeletal kaolinitic acid thermic plinthic Palexerult amended with lime and gypsum by-products was used to study changes in soil solution composition during two leaching cycles. The lime amendment mainly affected the composition of the soil solution of the Ap horizon, where it increased pH and Ca and decreased the F and Al concentrations. Gypsum by-products caused an initial pH decrease in the soil solution; however, as the gypsum was leached, the pH rose and eventually exceeded that of both Ap and AB in the controls. After the gypsum by-product application, Mg and Na strongly increased, but afterward decreased to levels lower than those in the controls; Al contents increased in the first water extracts from Ap and AB horizons and that of F in all extracts from Ap and most from AB. The variation of the Ca and SO42− concentrations in the AB horizon was influenced by surface sorption and precipitation.

Exchange Complex Composition in Mediterranean Ultisols Under Various Types of Vegetation and Soil Uses

We studied the dynamics of texture, bulk density, exchangeable bases, acidity, and aluminum in the uppermost surface 50 cm of Mediterranean Ultisols under natural vegetation at variable degradation stages and under different soil uses in the Cañameros raña formation (southwest Spain). The areas studied included a cork oak grove (the climax vegetation in the area), a field densely covered by Cistus ladaniferus L., a field with 55% covered by Cistus crispus L. and C. ladaniferus, a field with 10% covered by bushes of the same type as the previous one, and a field with grass and occasional Cistus bushes. All of these fields with bushes were extensively cultivated with rye (Secale cereale L.) and then abandoned 45, 35, 12, and 6 years, respectively, before the study. Finally, we selected an olive grove that had been under continuous tillage for the previous 65 years. The total organic matter content decreased, starting from the virgin soil, under cork oaks, to the most heavily degraded soil (that under olive trees), whereas the bulk density increased. The total contents of exchangeable Ca, Mg, Na, and K significantly decreased, in the same trend as organic matter. In contrast, the amount of aluminum extracted by 1N KCl, AlK, remained essentially constant or even increased with increasing soil degradation. This resulted in a markedly decreased Ca/AlK ratio in the topmost 5 cm of soil, which had a strong adverse effect on crop productivity and natural plant recovery after the soils were abandoned.

Agronomic Implications of the Application of Lime plus Gypsum By‐products to a Hyperdistric Acrisol from Western Spain

Abstract: A laboratory experiment involving the use of leaching columns reproducing the topmost portion of a Hyperdystric Acrisol (FAO 1998) or plinthic Palexerult (Soil Survey Staff 2003) treated in its Ap horizon with sugar foam wastes and phosphogypsum was conducted. The amendments increased the contents in exchangeable calcium (Ca) of the Ap horizon and, to a lesser extent, also that of the AB horizon. However, the contents in exchangeable magnesium (Mg) and sodium (Na) decreased as much in Ap as they did in AB; by contrast, the potassium (K) content exhibited a less marked decrease. The potassium chloride (KCl)–extractable aluminium (Al) of the Ap horizon was dramatically decreased much more than that of the AB horizon by the amendments. In the soil solution from Ap, the amendments raised the pH and decreased the Al concentration; in that from AB, however, they caused an initial pH decrease, a tendency that reversed as the gypsum was leached and eventually led to the pH exceeding that in the soil solution from control. The first few water extractions exhibited increased Mg concentration. This trend was reversed in the second leaching cycle, where the concentrations of Mg in the amended columns were lower than those in the controls. In the soil solution, the variation of the Ca and sulphate (SO4 2–) concentrations was influenced by the salt‐sorption effect. The total Al content in soil solution from AB increased during the first leaching cycle and then decreased during the second. The amendments decreased the activities of Al3+, AlOH+2, and Al(OH)2 + in the Ap horizon and increased those of Al3+, AlSO4 +, Al(SO4)2 −, and AlF+2 in the first leaching cycle in the AB horizon. The productivity of the Ap horizon after the treatments was assessed using a wheat crop (T. aestivum, var. ‘Jabato’) in a greenhouse.