Decrease In Base Saturation Research Articles

Comparative Characteristics of Mountain-Forest and Mountain-Meadow Soils of Dolgorukovskaya Yayla (the Crimean Mountains)

A comparative study of mountain-meadow and mountain-forest soils was performed within the entire Dolgorukovskaya Yayla—a plateau on the northern macroslope of the Main Ridge of the Crimean Mountains—in the altitudinal range from 560 to 975 m a.s.l. Soil morphology, texture, acidity, exchangeable cations, nonsilicate iron content, parameters of the humus status, and optical characteristics of soils were studied. Forest soils on the entire slope are assigned to acid and dark burozems (Cambisols, Luvisols); they are characterized by similar morphological properties and profile patterns of clay, humus, and nonsilicate iron. Mountain-meadow, mountain-meadow chernozem-like, and residual-carbonate soils (Phaeozems) are formed under meadow vegetation in the upper part of the plateau, and soils transitional to piedmont chernozems (Chernozems) are located in its lower part. Humus reserves in the 0- to 50-cm-thick soil layer varied from 16.6 to 42.2 kg/m2 under meadows and from 10.7 to 18.8 kg/m2 under forests. Soils under forest and meadow vegetation were characterized by an increase in acidity and a decrease in base saturation with the increase in the altitude. Acidity was generally higher in forest soils, while the difference in this parameter between forest and meadow soils in the upper part of the plateau was minimal. In soils under meadows, the content of oxalate-extractable iron also increased with the altitude, and its mean content in the A horizon (226 ± 67 mg/100) was higher than that in forest soils (183 ± 41 mg/100 g). More intense color of soils under grass vegetation as compared to soils under forests is mainly explained by the differences in the rate of organic matter humification and optical density of humic acids, the total humus content being similar in both groups of soils.

Transformation of physicochemical soil properties along a mountain slope due to land management and climate changes — A case study from the Karkonosze Mountains, SW Poland

The gradients of soil physicochemical properties along mountain slopes and across climate-elevation gradients were studied in the Karkonosze Mountains, focusing on the human-impacted zonality of the vegetation cover. The main focus of the study was the environmental consequences, both human-induced and spontaneous, of vegetation changes in the mountains which may occur due to climate change. In soils developed from granite, a clear altitude-related differentiation of soil properties was manifested by: (i) an increase in total organic carbon (TOC) with elevation; (ii) an increase in exchangeable acidity and aluminum (Alex); (iii) a decrease in pH, (iv) a decrease in base saturation; and (v) finer soil texture and higher content of base cations in the foothills and lower slopes. These altitude-dependent trends have a threshold-type distribution, i.e. the values stabilize at 750–1000ma.s.l. or are reversed in the subalpine zone. Grass vegetation decreased TOC and Alex, but increased soil pH and base saturation compared with forest vegetation at the same altitude zone. Soils under spruce had higher TOC but lower pH compared with beech stands.Present-day changes of mountain area management in Central Europe, i.e. the replacement of spruce monocultures with beech or mixed stands in the lower forest zone and reforestation (mainly with spruce or mountain pine) of abandoned meadows and pastures at and above the timberline significantly influence topsoil properties, but there is a contrasting direction of changes in the lower and upper altitude zones. Expected climate changes may shift the upper limits of the individual forest zones and reinforce the ongoing changes in forest management. The final regional result of changes is difficult to calculate and strongly dependent on the degree of anthropogenic transformation of vegetation cover. However, both the current changes in management practices and possible climate changes will reinforce the existing vertical gradients of mountain soil properties, including the elevation-related increase in TOC, exchangeable acidity and Alex, as well as the decrease in soil pH and base saturation.

Long-term changes in the chemical properties of Japanese cedar (Cryptomeria japonica) forest soils under high precipitation in southwest Japan

There is insufficient direct evidence of long-term changes in the chemical properties of forest soils to provide information for forestry management plans for sustainable site productivity. To understand changes in the chemical properties of forest soils in a specific high-precipitation climate in Japan, we re-investigated, in 1997, soil pits within a Japanese cedar (Cryptomeria japonica) forest in the Yanase region of Kochi Prefecture which had previously been surveyed in 1976. Comparison of the 1976 and 1997 results revealed significantly lower pH of surface and subsurface soils, and fewer exchangeable cations over time. In contrast, subsoil pH, concentrations of total carbon and nitrogen, and cation-exchange capacity (CEC) had not changed over the 21-year period. Estimation of proton and cation budgets in the forest ecosystem over 21 years, using data for the amounts in soil, biomass accumulation, and input through precipitation, revealed that biomass accumulation did not explain the cation depletion in soils. This suggests that cations were leached from the ecosystem. In contrast with previous reports, which showed Ca accumulation in Japanese cedar forest soils, our results indicated that high precipitation of more than 4,000 mm combined with acid deposition resulted in soil acidification and leaching of cations from soils, following the decrease in base saturation.

Diminished Soil Quality in an Old-Growth, Mixed Mesophytic Forest Following Chronic Acid Deposition

Human activities have increased acid deposition throughout the Ohio River Valley due to the large number of coal-fired power-generating facilities. The long-term effects of chronic acid deposition can include a decrease in soil pH, loss of soil fertility, and a decrease in base saturation—all of which can reduce forest productivity. Dysart Woods, a remnant old-growth, mixed mesophytic forest in eastern Ohio, has experienced a decrease in soil pH from 5.0 in 1971 to 4.6 in 1997, which may be due to chronic acid deposition. The objective of this study was to utilize a long-term study to evaluate how soil quality has changed due to chronic acid deposition. To meet the study objectives, a variety of soil chemical properties (pH, base saturation, C, N, P, etc.) were measured from surface soil within two stands of opposing aspect at Dysart Woods within the unglaciated Allegheny Plateau. Because soil pH correlates strongly with other soil chemical properties, we used pH data from 1971 to estimate how soil quality has changed over time. Mean soil pH from the south-facing stand was 5.0 in 1971, 4.6 in 1997, and 4.3 in 2007. While soil pH was not measured in the north-facing stand in 1971, pH was 4.6 in 1997 and 4.7 in 2007. Using changes in pH to estimate past soil properties, our results suggest that available base cations in the south-facing stand have been reduced from ≈12 to 6 (cmolc kg-1), with a 50% reduction in base saturation since 1971. Considering that both stands receive the same amount of acid deposition due to their close proximity to each other, results raise an interesting question: Are unglaciated Allegheny Plateau south-facing soils more susceptible to the effects of acid deposition than north-facing soils?

The sensitivity of Swiss forest soils to acidification and the risk of aluminum toxicity

AbstractIn the context of pollution‐control strategies to minimize the detrimental effects of soil acidification, there is a need to know how and to what extent soils respond to acidifying substances. The purposes of this study were to assess the sensitivity of soil to acidification, in particular to a decrease in pH and in base saturation (BS), and the risk of Al toxicity for vulnerable plants using chemical indicators. These indicators were derived from soil data (pH, exchangeable cations, amount of fine earth) measured in the mineral horizons of 257 soil profiles throughout Switzerland. Based on the analysis of the distribution of pH and BS values in the soil collective, we assessed the sensitivity of soils to a decrease in pH and in BS. Soils that were considered sensitive to a decrease in pH had pH values between 4.8 and 7.0. The degree of sensitivity was estimated with the proportion of fine earth in the critical pH range to a depth of 100 cm. Soils that were considered sensitive to a decrease in BS had pH values between 3.6 and 5.5 and a BS between 10% and 95%. Since the effective cation‐exchange capacity (CECeff) of the fine earth might dampen the decrease in BS when acidity is added, the disposition for a decrease in BS was related to the relative amount of fine earth in the sensitive BS and to the mean CECeff of this fine‐earth fraction. The risk of Al toxicity for vulnerable plants was estimated using the ratio of base cations to Al at the cation‐exchange sites (BC : Alexc). A BC : Alexc of 0.2 was taken as a threshold value below which the risk for sensitive plants increases. The degree of risk was based on the proportion of fine earth in the critical BC : Al range (≤0.2) in the soil profile. These indicators taking into account the various aspects of soil acidification are derived from usually available data and represent therefore a cost‐effective tool to assess the sensitivity of soils to an input of acidity.

The base saturation in acidified Swiss forest soils on calcareous and noncalcareous parent material. A pH–base saturation anomaly

AbstractLong‐term soil acidification leads to lower pH values and to a concomitant decrease in base saturation (BS). The relationship between pH and base saturation (BS) in acidified forest soils can be disturbed by processes such as nutrient cycling by vegetation, temporary saturation by ground water that comes into contact with calcareous material, or by upward diffusion of base cations from deeper horizons. This paper examines the relationship between pH and BS in Swiss forest soils developed from calcareous and noncalcareous parent material and identifies some of the factors that can affect the BS in the decalcified parts of soils derived from calcareous parent material. The decalcified zone in the latter soils has a higher BS on average compared to soils from noncalcareous parent material, but their pH values are identical. In the pH range 4.0–4.5, the difference in BS may vary by a factor of three. The mean BS in the decalcified zone tends to decrease with increasing depth of the calcareous layer. The water regime also affects the BS in soils on calcareous parent material. In soils temporarily saturated by groundwater (gleysols), the BS in the decalcified zone is always high (85%–100%) because of the continuous contact between the soil water and the calcareous parent material. In addition, the inhibited drainage impedes the depletion of base cations in these soils. In contrast, soils that are temporarily saturated by rainwater are depleted in base cations due to the alternating wetting‐and‐drying regime and the associated leaching of dissolved ions. In such soils, the depletion of base cations is strongly related to the extent of hydromorphy. Stagnogleyic soils, with the longest period of water saturation, have the highest depletion levels. We conclude that in such soils, the diffusion of base cations from deeper zones is strongly compensated by leaching from the very acidic soil horizons. The pH–base saturation anomaly has consequences for some of the methods used to calculate the critical loads of acidity for forest soils in Switzerland, with many soils being less sensitive than previously reported.

Acidification-induced chemical changes in coniferous forest soils in southern Sweden 1988–1999

Thirty-two Norway spruce [Picea abies (L.) Karst.] and Scots pine (Pinus sylvestris L.) stands in southern Sweden were studied for a period of 12 years to evaluate acidification-induced chemical changes in the soil. Soil, at 20–30 cm depth in the mineral layer, was sampled three times during this period (1988, 1993 and 1999). The results show that pH(BaCl2) in mineral soil decreased by, on average, 0.17 units between 1988 and 1999, accompanied by an increase in aluminium (Al) concentration and a decrease in base saturation in the soil. In 1999, the base saturation was below 5% in 58% of the 32 sites compared with 16% in 1988 and 7% in 1993. Concentrations of calcium (Ca), potassium (K) and magnesium (Mg) are low and decreasing. Based on C/N ratios in humus, 45% of the sites may be subjected to leaching of considerable amounts of nitrate. The results show that the acidification of coniferous forest soils in southern Sweden is continuing, and that the negative effects on the nutrient status in soil are extensive. The results are compared with reference values for productive, long-term sustainably managed boreal coniferous or mixed forest soils and implications for long-term sustainability are discussed.

A regional GIS-based model to predict long-term responses of soil and soil water chemistry to atmospheric deposition : Initial results

The aim of this study was to develop GISSMART, a GIS-based model, for estimating relative regional changes in soil andsoil water chemistry for given atmospheric deposition and nutrient uptake scenarios. The regional application was performed by dividing the study area into grid cells, the size and the form of the pixels being determined on the basisof the available GIS data bases of Finnish soil and vegetationtypes. GISSMART is the biogeochemical model SMART, extended forhandling GIS data in space and time. The Kangasvaara catchment(56 ha) in eastern Finland was used as the first test site. Data from four other nearby catchments were also used, togetherwith Multisource National Forest Inventory data (25 × 25 m2) from an area of 10 × 40 km2 for estimating soil chemistry. Multisource forest inventory datafrom the Finnish Forest Research Institute, including tree species, age and growth by tree species was based on LandsatTM-images and field measurements. The same satellite based estimation method was applied to obtain regional soil chemistry input data for GISSMART. Base saturation was the key state variable and nutrient uptake the key driving variablein this application of GISSMART. The results of the model testruns were reasonable. A slight decrease in base saturation waspredicted for the assumed deposition and nutrient uptake scenarios. In future work, the aim is to improve the description of hydrological processes and land use management in the model. This would also enable assessment of the effectsof climate change and land use management scenarios.

Recent Losses of Base Cations from Soils of Fagus sylvatica L. Stands in Northeastern France

Abstract In 1991, in order to assess changes in soil acidity, we resampled the mineral soil from 95 plots in beech forests distributed throughout northeastern France, ca. 20 years after a first sampling in 1970–1973. Changes between the two sampling dates were more conspicuous for acidic soils than for mesotrophic or calcareous soils. We observed a significant decrease in base saturation, exchangeable calcium, magnesium, and potassium in the whole profile of the acidic soils. Median cation losses calculated for these soils down to a depth of 80 cm were 18.7 kg ha−1 yr−1 for calcium, 2.7 kg ha−1 yr−1 for magnesium, and 2.4 kg ha−1 yr−1 for potassium. This loss was not reflected by changes in soil pH (measured in water extracts). The intensity of the cation losses and the analysis of the pollution climate over the last 20 years suggest that atmospheric deposition could have contributed to the observed changes.

Application of the forest–soil–water model (PnET-BGC/CHESS) to the Lysina catchment, Czech Republic

In this study a fully linked plant-soil-water model PnET-BGC/CHESS (Santore, R.C., 1996. PnET-BGC/CHESS model. Version P3NC115; Santore, R.C., 1999. Modeling forest soil response to chemical treatment at three sites in the Adirondack Mountains, New York) was evaluated and applied. Forest growth, hydrologic, and biogeochemical processes with emphasis on element cycling in forest and adjacent aquatic ecosystems were simulated for the Lysina catchment, Czech Republic. The PnET-BGC submodel expands calculations of forest productivity and water use of the earliest version of the PnET model to include decomposition processes and cycling of major nutrients and other elements. The CHESS submodel simulates abiotic soil chemical processes. The study catchment consists of Norway spruce ( Picea abies) plantations on Spodosols located in a granitic highland of western Bohemia. Forest growth, hydrology and biogeochemistry of the catchment were simulated for the period 1550–2050. Simulated concentrations of SO 4 2−, F −, Ca 2+, Mg 2+, Na +, K +, Fe T, Si, and monomeric Al were similar to streamwater concentrations measured in 1990–1994. The model moderately overpredicted H +, Cl − and DOC, and highly overpredicted NO 3 − and especially NH 4 +. A scenario of reductions of S inputs by 67% of 1991–1994 values in 1995–2050 showed a decrease in base saturation of soil of 2.5% between 1995 and 2050. Inputs of S reduced by 90% of current values showed an increase in soil base saturation after 2030. Scenarios of improved deposition of S showed desorption of previously stored S to drainage water which delayed recovery from inputs of acidic deposition.

Effects of long-term artificial acidification on the ground vegetation and soil in a 100 year-old stand of Scots pine (Pinus sylvestris)

A study on the effects of eight years application of artificial acid rain on the vegetation and soil in an old Scots pine forest is described. Artificial rain of pH 2.5 and 3.0 caused severe damage to mosses, especially Pleurozium schreberi and Dicranum polysetum. The presence of Melampyrum pratense decreased drastically in plots treated with ‘rain’ of pH 2.5 and 3.0. In Vaccinium myrtillus reduced leaf production was found in plots treated with ‘rain’ of pH 2.5. A considerable decrease in base saturation had taken place in plots treated with pH 2.5 and pH 3.0 ‘rain’. Exchangeable calcium and magnesium in particular had been reduced, and the content of mangnesium in tissue of Vaccinium myrtillus appeared also to be reduced in plots treated with water of pH 2.5. The study demonstrates the need for better methods in evaluating vegetation responses in field studies. The use of visual cover recording should be supplemented by frequency analysis and harvesting methods to get better estimates of changes in vegetation structure.

Simulation of the long-term soil response to acid deposition in various buffer ranges

A soil acidification model has been developed to estimate long-term chemical changes in soil and soil water in response to changes in atmospheric deposition. Its major outputs include base saturation, pH and the molar Al/BC ratio, where BC stands for divalent base cations. Apart from net uptake and net immobilization of N, the processes accounted for are restricted to geochemical interactions, including weathering of carbonates, silicates and Al oxides and hydroxides, cation exchange and CO2 equilibriums. First, the model's behavior in the different buffer ranges between pH 7 and pH 3 is evaluated by analyzing the response of an initially calcareous soil of 50 cm depth to a constant high acid load (5000 molc ha−1 yr−1) over a period of 500 yr. In calcareous soils weathering is fast and the pH remains high (near 7) until the carbonates are exhausted. Results indicate a time lag of about 100 yr for each percent CaCO3 before the pH starts to drop. In non-calcareous soils the response in the range between pH 7 and 4 mainly depends on the initial amount of exchangeable base cations. A decrease in base saturation by H/BC exchange and Al/BC exchange following dissolution of Al3+ leads to a strong increase in the Al/BC ratio near pH 4. A further decrease in pH to values near 3.0 does occur when the A1 oxides and/or hydroxides are exhausted. The analyses show that this could occur in acid soils within several decades. The buffer mechanisms in the various pH ranges are discussed in relation to Ulrich's concept of buffer ranges. Secondly, the impact of various deposition scenarios on non-calcareous soils is analyzed for a time period of 100 yr. The results indicate that the time lag between reductions in deposition and a decrease in the Al/BC ratio is short. However, substantial reductions up to a final deposition level of 1000 molc ha−1 yr−1 are needed to get Al/BC ratios below a critical value of 1.0.

Acidity Produced by Leguminous Plants through Symbiotic Dinitrogen Fixation

AbstractRed clover (Trifolium prateuse L.), sweet clover (Meliotus alba Medik.), alfalfa (Medicago sativa L.), and crown vetch (Vica villosa Roth) were grown in nitrogen‐free Hoagland's solution in a declining nutrient condition. Increases in acidity of the nutrient solutions were recorded over the experimental period. In general, the excess bases and the excess bases/nitrogen ratio varied considerably among harvests. Significant positive relationships between total N and proton efflux, excess bases and H+ excretion, and dry weight and H+ efflux were observed. The milligrams H+ produced per gram N fixed for the four legumes were 49 for red clover, 43 for crown vetch, 42 for alfalfa, and 37 for sweet clover. By extrapolating the protons produced per gram dry weight in this study to yields commonly observed in the field, annual hydrogen production per hectare would amount to 9.7 kg for red clover, 4.6 kg for sweet dover, 15.2 kg for alfalfa, and 4.5 kg for crown vetch. The amounts of acidity produced per hectare per year calculated from the values of N2 fixation were 5.2 to 14 kg by alfalfa, 4.2 to 9.4 kg by red clover, 3.2 to 7.1 kg by sweet clover, and 3.9 to 6.8 kg by crown vetch. The study demonstrates that production of H+ through symbiotic fixation by legumes is an important source of acidity in agricultural ecosystems. The acidifying effect of legumes could, in the long‐term, result in acidification of the bulk soil causing the downward leaching of exchangeable cations and a decrease in base saturation.

The effect of seasonal flooding on the clay mineralogy of a soil series in the Volta Lake drawdown area, Ghana

AbstractFour pedons of Arenic/Grossarenic Paleustalf (Denteso Series), in the Volta Lake drawdown area in Northern Ghana, were described and sampled just before seasonal floodings commenced in the area. After 5 years of periodic flooding the soils were re‐examined and sampled. Soil properties required for soil classification, including the clay mineralogy, of both the pre‐flooding and the post‐flooding samples were determined. One of the main objectives was to identify changes in soil properties which result from the periodic flooding.X‐ray diffraction (XRD) indicated that before flooding the main clay minerals of the Denteso were kaolinite and smectite, and there were also some mica and quartz in the total clay fraction. Comparison of the pre‐flooding with the post‐flooding data revealed that practically all the smectite disappeared from all the three sampled pedons that were flooded for 5 to 20 weeks during each flood cycle, while the smectite persisted in the non‐flooded pedon. With the disappearance of the 2 : 1 lattice clays there occurred a considerable decrease in cation exchange capacity (CEC) and in base saturation of the flooded pedons ranging from 0.04 to 3.63 cmol kg −1. Also, there was an increase in pH by 0.4 to 1 unit in most horizons of the flooded pedons in spite of the general decrease in base saturation. These changes in CEC, base saturation and pH support the XRD evidence that the seasonal floodings caused pedochemical weathering of the smectite in this loamy sand soil at a very fast rate during the 5 year period and this had resulted in the lowering of the buffering capacity and a general impoverishment of the soil series.

The long-term effect of eucalyptus plantations on tin-mine spoil and its implication for reclamation

As part of the reclamation strategy for tin-mine spoil on the Jos Plateau of Nigeria, eucalypt plantations comprising mainly Eucalyptus camaldulensis have been established on reclaimed sites. The intention of this practice, started in 1960, was that the eucalyptus would speed up the process of amelioration of the spoil soils so that agriculture could be re-established on these sites within 20–30 years. The demise of the Mine Lands Reclamation Unit which instituted this policy has meant that monitoring of the long-term effects of these eucalypts on the soil has also ceased. As part of a wider project involved with mineland reclamation, in 1983 an investigation was launched into the effects that eucalypt plantations have had on the spoil soils in the 15–20 years since their establishment. The results indicate that the plantations have had little impact on the morphology of the soils. Despite a high litter input, large areas of the ground surface beneath the eucalypts remains completely bare and ground vegetation is very limited in extent, tending to be concentrated in wetter hollows. This lack of ground cover is thought to be due to a combination of surface compaction caused during reclamation and the allelopathic properties of the eucalypt leaves. Although much of the soil beneath the eucalypts is devoid of any organic layer, the eucalypts have nevertheless significantly increased the amount of organic carbon and total nitrogen in the soils. This is accompanied by an associated increase in cation exchange capacity and a significant fall in both pH and base saturation. This decrease in base saturation and pH indicates that, under current management practices, the long-term effect of eucalypts is one of progressive degradation of already poor soils. This is exactly the opposite result to that which was envisaged by the Mine land Reclamation Unit when it adopted the policy of establishing eucalypt plantations. A change in management practices, whereby the slash produced during coppicing of the plantations is left to decompose in situ, may help to reduce the long-term deterioration of the soil. Such a policy would however require extremely detailed policing arrangements. If the aim of reclamation remains that of producing soil of agricultural quality from the mining spoil, then an alternative is required. A possible solution would involve the addition of large quantities of cheap organic fertilizer and the immediate use of the restored land for agriculture.

Metal uptake in plants from a birch forest area near a copper smelter in Norway

Uptake of Ca, Mg, K, Mn, Fe, Al, Rb, Ph, Cu, Zn, and Cd in vascular plants from a birch forest area near a Cu smelter in northern Norway was investigated. The primary objective was to study metal uptake in plants growing in a strong local acidification gradient. Decreased levels of Mn, Mg, and Ca found in Betula pubescens, Vaccinum myrtillus, and Deschampsia flexuosa near the smelter corresponded to a decrease in base saturation of the soil. This suggests that appreciable soil acidification has taken place. The level of Rb in Vaccinum myrtillus and Sorbus aucuparia increased significantly towards the smelter, probably due to the higher soil acidity. Elevated levels of Cu, Zn, Ph, and Cd in surface soil were found with values up to 2500 mg kg−1 Cu within 1 km from the smelter. These concentrations decreased significantly with distance, but metal contamination was detectable up to 27 km from the smelter along the prevailing wind direction. A corresponding decrease was detected for Cu in the four plant species analyzed. Elevated levels of Zn, Ph, Fe, and Al were found in some, but not all, species.

Effect of clear-felling and slash removal on the acidity of Northern coniferous soils

Measurements of pH were carried out at two experimental sites in Sweden before and after clear-felling. At eleven sites, pH, cation-exchange capacity, base saturation and exchangeable hydrogen ions were compared in clear-felled areas where slash was left and removed, respectively. It is shown that pH increases significantly after clear-felling. The increase is larger than can be explained by the release of basic cations in connection with decomposition of slash and humus. The increase in pH is less in a clear-felled area when the slash is removed than when it is left. There is a decrease in exchangeable Ca 2+, Mg 2+ and Mn 2+ and an increase in H + and Al 3+. There is a decrease in base saturation of about 80%.

Some observations on surface soil pH, base saturation and leaching of cations under three contrasting orchard soil management practices

Observations from a soil management trial conducted on a previously grassed down orchard showed that after 3 years the pH of the surface soil (0–10 cm) whether measured in distilled water or 1N KCl was significantly lowered in herbicided and cultivated treatments in comparison with plots under continued grass sod. The drop in pH was accompanied by a decrease in base saturation and a consequent increase in exchange acidity. This was attributed to the leaching of Ca and also Mg from the surface soil of the non-grassed plots. In a subsequent laboratory leaching study, cubic soil blocks (16 cm3) were leached with distilled water at two weekly intervals for 24 weeks. It was found that over the experimental period, the cumulative quantity of cations leached (in milli-equivalents) per soil block from the herbicided and cultivated treatments was approximately 3.5 times that leached from the grassed treatment.

Laboratory study of nutrient leaching from the surface of cultivated, grassed and herbicided orchard soil

The effects of continued grass cover versus the removal of a grass sod, either by cultivation or the use of a herbicide, on the leaching of nutrients, was studied in a 24 week laboratory leaching study utilizing cubic soil blocks (16 cm deep) which were dug from the surface soil of a commercial apple orchard. In percolates from grassed treatments significantly lower a 2+, Mg 2+, Na +, NO 3 − and SO 4 2− concentrations were observed than in percolates from non-grassed treatments. Consequently, the total ionic strength (Σ Cat + Σ An) was significantly lower than in non-grassed treatments. In comparison with non-grassed treatments, grass sod also resulted in a relative decrease in the contribution of Ca 2+, Mg 2+ and NO 3 − with a concomitant relative increase in the contribution of K +, HCO 3 −, SO 4 2− and Cl − to ΣCat and ΣAn, respectively. The major anion leached from the non-grassed treatments was NO 3 − while the major balancing cations were Ca 2+ and to a lesser extent Mg 2+. Over the 24 week period, from grassed, cultivated and herbicided treatments, NO 3 − accounted for 25, 70 and 70%, respectively of the mean ΣAn leached, while Ca 2+ accounted for 48, 62 and 63%, respectively of the mean ΣCat. The results are discussed in relation to the decrease in base saturation and pH which often occurs in the surface soils of non-grassed soil management practices.