Juliane Lilienfein

Chemical fractionation of phosphorus, sulphur, and molybdenum in Brazilian savannah Oxisols under different land use

In soils, P, S, and Mo occur organically bound or as oxyanions. In Oxisols, oxyanions may be strongly sorbed due to the high positive surface charge. The objective of this work was to compare chemical fractions of P, S, and Mo in differently used Oxisols with similar properties in an on-farm experiment. Soil samples (0–0.15 m) were taken from three replicate plots of each of conventional tillage (CT) and no-till (NT) maize–soybean and conventional tillage sugarcane (SC) cropping systems, degraded (DP) and productive pastures (PP), Eucalyptus (EU) and Pinus reforestations (PI), and native savannah (CE). The samples were sequentially extracted with (1) 0.5 M NaHCO3, (2) 0.1 M NaOH, (3) 1 M HCl, (4) hot concentrated HCl, and (5) concentrated HClO4/HNO3. In the extracts, inorganic (Pi) and total P, S, and Mo were determined. Organic P (Po) was calculated as total P−Pi. Total concentrations were 333–567 mg P kg−1, 231–284 mg S kg−1, and 3.2–3.9 mg Mo kg−1. The most important fractions in all studied systems were the NaOH fraction for P (38–49% of total P), the HClO4/HNO3 fraction for S (27–35% of total S) and the concentrated HCl fraction for Mo (86–90% of total Mo). The proportion of the more easily extracted NaHCO3+NaOH fractions decreased along the line S>P>Mo. Fertilisation increased plant-available P and S fractions in CT and NT whereas recalcitrant fraction (concentrated HCl and HClO4/HNO3) remained unchanged. The Pi/Po ratios in NT and CT were higher than in CE because fertiliser P mainly accumulated in inorganic P fractions. The pasture soil had lower P concentrations indicating export by grazing. Thus, 12–20 years of land use had marked effects on P, smaller ones on S, and almost none on Mo concentrations and chemical fractions.

Nutrient storage in soil and biomass of native Brazilian Cerrado

The removal or burning of the biomass which frequently includes main roots results in significant nutrient losses from the Brazilian savanna, the Cerrado. To estimate these losses, we quantified above- and belowground plant biomass and total nutrient storage in biomass and soil of a typical Cerrado. Dominant tree species in the layer > 2 m were Pouteria torta (MART.) RADLK., Ouratea spectabilis (MART.) ENGL., Roupala montana AUBL., Byrsonima coccolobifolia H.B. et K., Dalbergia miscolobium BENTH., Kielmeyera coriacea MART., and Caryocar brasiliense CAMBESS. which together represented 70 % of the biomass of the > 2 m layer. In the 0.5—2 m tree layer, many different species were found of which Ouratea hexasperma (ST.-HIL.) BAILL. representing 33 % of the biomass in the 0.5—2 m layer was most abundant. The dominant shrub species were Miconia holosericea DC., Hortia brasiliana VAND. ex DC., Myrcia rostrata DC., Parinari obtusifolia HOOK. f., and Campomanesia velutina BLUME, contributing 93 % to the total shrub biomass. Total aboveground plant biomass was 22.7 Mg ha—1, total belowground plant biomass was 30.4 Mg ha—1. The tree layer > 2 m comprised the largest proportion of the aboveground biomass (64.6 %) > grass/herb (13.0 %) > shrub layer (11.6 %) > tree layer 0.5—2 m (10.8 %). Three quarters of the fine root biomass (17.6 Mg ha—1) were located in the upper 0.3 m of the soil. The element storages (in kg ha—1) were C: 10900, N: 173 N, P: 20, K: 51, Ca: 66, Mg: 20, S: 25, Fe: 10, Mn: 4.2, Zn: 0.35, and Al: 27 in the aboveground biomass, C: 12900, N: 214 N, P: 14, K: 41, Ca: 52, Mg: 10, S: 33, Fe: 2060, Mn: 2.9, Zn: 0.60, and Al: 648 in the belowground biomass, and C: 55400, N: 3510 N, P: 631, K: 366, Ca: 86, Mg: 75, S: 529, Fe: 159000, Mn: 124, Zn: 49, and Al: 434000 in the soil (0—0.3 m). If the above- and belowground biomass was completely removed from the Cerrado ecosystem losses would range from 5 % of the total nutrient storage for P to 58 % for Ca referred to a lower ecosystem boundary at 0.3 m mineral soil depth. Nahrstoffvorrat in Boden und Biomasse eines naturbelassenen brasilianischen Cerrados Die Entfernung oder Verbrennung der Biomasse, haufig einschlieslich der Hauptwurzeln, fuhrt zu erheblichen Nahrstoffverlusten aus der brasilianischen Savanne, dem Cerrado. Um diese Verluste zu schatzen, haben wir die ober- und unterirdische Pflanzenbiomasse und den Nahrstoffvorrat in der Biomasse und im Boden eines typischen Cerrados bestimmt. Die dominierenden Baumarten in der > 2 m hohen Schicht waren Pouteria torta (MART.) RADLK., Ouratea spectabilis (MART.) ENGL., Roupala montana AUBL., Byrsonima coccolobifolia H.B. et K., Dalbergia miscolobium BENTH., Kielmeyera coriacea MART. und Caryocar brasiliense CAMBESS., die zusammen 70 % der Biomasse dieser Schicht umfassten. In der 0,5—2 m hohen Baumschicht wurden viele verschiedene Arten gefunden, unter denen Ouratea hexasperma (ST.-HIL.) BAILL., die 33 % der Biomasse dieser Schicht reprasentierte, die haufigste war. Die dominierenden Straucharten waren Miconia holosericea DC., Hortia brasiliana VAND. ex DC., Myrcia rostrata DC., Parinari obtusifolia HOOK. f. und Campomanesia velutina BLUME, die 93 % der gesamten Biomasse der Strauchschicht speicherten. Die gesamte oberirdische Pflanzenbiomasse betrug 22,7 Mg ha—1, die unterirdische 30,4 Mg ha—1. Die > 2 m hohe Baumschicht umfasste den grosten Teil der oberirdischen Biomasse (64,6 %) > Gras/Krautschicht (13,0 %) > Strauchschicht (11,6 %) > 0,5—2 m hohe Baumschicht (10,8 %). Drei Viertel der Feinwurzelbiomasse von 17,6 Mg ha—1 befanden sich in den oberen 0,3 m des Mineralbodens. Die Elementvorrate (in kg ha—1) waren C: 10900, N: 173 N, P: 20, K: 51, Ca: 66, Mg: 20, S: 25, Fe: 10, Mn: 4.2, Zn: 0.35 und Al: 27 in der oberirdischen Biomasse, C: 12900, N: 214 N, P: 14, K: 41, Ca: 52, Mg: 10, S: 33, Fe: 2060, Mn: 2.9, Zn: 0.60 und Al: 648 in der unterirdischen Biomasse und C: 55400, N: 3510 N, P: 631, K: 366, Ca: 86, Mg: 75, S: 529, Fe: 159000, Mn: 124, Zn: 49 und Al: 434000 im Boden (0—0,3 m). Wenn die gesamte ober- und unterirdischen Biomasse aus dem Cerrado-Okosystem entfernt wurde, gingen zwischen 5 % des gesamten Nahrstoffvorrates fur P und 58 % fur Ca, bezogen auf eine untere Grenze des Okosystems in 0,3 m Mineralbodentiefe, verloren.

Soil formation and organic matter accretion in a young andesitic chronosequence at Mt. Shasta, California

The objectives of this work were to study rates of increase in allophane concentration, specific surface area changes, and organic matter accretion in a young andesitic chronosequence. We sampled the 0–10-, 10–20-, 30–40-, 70–80-, and 140–150-cm depths of 77-, 255-, 616-, and approximately 1200+-year-old soils and analyzed them for allophane, ferrihydrite, specific surface area, cation exchange capacity, soil pH, and C and N concentrations. Allophane concentrations increased at rates up to a maximum of 0.14 g kg−1 year−1, and concentrations are up to 68 times higher in the oldest than in the youngest soil. During the same time ferrihydrite concentrations increased only by a factor of 2.3. The specific surface area that could be attributed to allophane was only 2–4% in the youngest soil but was 41–97% in the oldest soil. Carbon and N stocks increased linearly with soil age over the first ∼600 years with rates of 139 kg C ha−1 year−1 and 5.3 kg N ha−1 year−1, respectively. After about 600 years, accretion rates were lower. Increases in allophane concentrations lead to increased cation exchange capacity in the soil. Our results indicate that the ability of the soil to retain nutrients improved with soil development.

Contamination of highly weathered urban soils in Uberlândia, Brazil

We determined heavy metal, polycyclic aromatic hydrocarbon (PAH), and polychlorinated biphenyl (PCB) concentrations in 18 topsoils of Uberlândia (420,000 inhabitants, Brazil) and in 3 rural topsoils. Concentrations of Al (11—124 g kg—1) and Fe (13—109 g kg—1) are large because of desilification. Concentrations of Cd (0.1—0.5 mg kg—1), Cr (13—72), Cu (6—154), Mn (28—974), Ni (4—29), Pb (3—26), Zn (4—107), the sum of 20 PAHs (=Σ20PAHs:7—390 μg kg—1), and the sum of 14 PCBs (=Σ14PCBs:0.05—1.25) are comparable to or below background concentrations in temperate soils except for Cu at two sites. More than 67% of the metals are strongly bound in Fe oxides and silicates; metals are more bioavailable in the urban than in the rural soils. The most abundant PAHs in the urban soils, on average, are naphthalene (19.0 ± 13.4% of Σ20PAHs) and the benzo(b+j+k)fluoranthenes (11.4 ± 6.7%); the most abundant PCBs are nos. 138 (23.3 ± 11.0% of Σ14PCBs) and 153 (14.3 ± 6.4%). The rural soils contain larger percentages of low molecular PAHs and up to tetra‒chlorinated PCBs than the urban soils. The different pollutant concentrations and patterns in the studied tropical compared with many temperate soils indicate different sources and fate. Schadstoffbelastung stark verwitterter urbaner Boden in Uberlândia, Brasilien Wir bestimmten die Gehalte an Schwermetallen, polyzyklischen aromatischen Kohlenwasserstoffen (PAK) und polychlorierten Biphenylen (PCB) in 18 Oberboden Uberlândias (420.000 Einwohner, Brasilien) und in drei landlichen Oberboden. Die Al‒ (11—124 g kg—1) und Fe‒Gehalte (13—109 g kg—1) sind als Folge der Desilifizierung hoch. Die Cd‒ (0,1—0,5 mg kg—1), Cr‒ (13—72), Cu‒ (6—154), Mn‒ (28—974), Ni‒ (4—29), Pb‒ (3—26) und Zn‒Gehalte (4—107) und die Summengehalte von 20 PAK (=Σ20PAK: 7—390 μg kg—1) und 14 PCB (= Σ14PCB: 0,05—1,25) sind mit Ausnahme von Cu of 2 Standorten vergleichbar mit Hintergrundgehalten in Boden der gemasigten Breiten oder niedriger. Mehr als 67% der Metalle sind in Fe-Oxiden und Silikaten stark festgelegt; die Metalle sind in den urbanen Boden besser bioverfugbar als in den landlichen. Die haufigsten PAK in den Stadtboden sind im Mittel Naphthalin (19,0 ± 13,4% der Σ20PAK) und die Benzo(b+j+k)fluoranthene (11,4 ± 6,7%); die haufigsten PCB sind Nr. 138 (23,3 ± 11,0% der Σ14PCB) und 153 (14,3 ± 6,4%). Die landlichen Boden enthalten grosere Anteile an niedermolekularen PAK und bis zu vierfach chlorierten PCB als die Stadtboden. Die unterschiedlichen Schadstoffgehalte und ‒muster in den untersuchten tropischen Boden im Vergleich zu vielen Boden der gemasigten Breiten deuten auf unterschiedliche Quellen und Dynamik im Boden hin.

Effect of no-tillage and conventional tillage systems on the chemical composition of soil solid phase and soil solution of Brazilian savanna Oxisols

No-tillage (NT) cropping systems are becoming increasingly important in the Brazilian savanna. To evaluate their sustainability we compared soil chemical properties in 1- to 3-year-old NT systems following 9 to 11 years of conventional tillage (CT) with systems where CT was continuously in place for 12 years. In the rainy season 1997/98, NT was cropped with soybean and CT with corn while in the rainy season 1998/99 both systems were cropped with soybean. Soil solid phase samples were taken from the 0-0.15, 0.15-0.3, 0.3-0.8, 0.8-1.2, and 1.2-2 m layers on three spatially separated plots under each of NT and CT. Soil solution samples were collected weekly at 0.15, 0.3, 0.8, 1.2, and 2 m soil depth during two rainy seasons (14 October to 28 April 1997/98 and 1998/99). We determined soil moisture contents, pH, the concentrations of exchangeable cations, the electrical conductivity (EC) of the soil solution, and the concentrations of Al, C, Ca, Cl - , K, Mg, Mn, Na, NH 4 + , NO 3 - , P, S, and Zn in solid soil and soil solution samples. Differences in soil solid phase properties and moisture content between NT and CT were small, few were significant. Under NT, the average solution pH was significantly lower (5.5), Al (26 tag 1 -1 ), Mn (17 μg 1 -1 ) and total organic C concentrations (TOC, 6.5 mg 1 -1 ) were higher than under CT (pH: 6.0, Al: 14μg 1 -1 , Mn: 14μg 1 -1 , TOC: 5.5 mg 1 -1 ). Irrespective of the different crops in the first rainy season, under NT, the EC (205 μS cm -1 ), Ca (17 mg 1 -1 ), and Mg (2.9 mg 1 -1 ) concentrations at 0-0.3 m depth were lower than under CT (EC: 224 μS cm -1 , Ca: 25 mg 1 -1 , Mg: 5.6 mg 1 -1 ). At 1.2-2 m depth, the reverse order was observed (EC: 124 μS cm -1 under NT and 84 μS cm -1 under CT, Ca: 11 mg 1 -1 under NT and 7.5 mg 1 -1 under CT, Mg: 3.1 mg 1 -1 under NT and 1.8 mg 1 -1 under CT). Our results indicate that enhanced soil acidification because of higher rates of organic matter mineralization and a more pronounced nutrient leaching because of increased pore continuity may limit the sustainability of NT.

Element storage in native, agri-, and silvicultural ecosystems of the Brazilian savanna

The expanding agriculture in the Brazilian savanna, the Cerrado, changes C and nutrient storages of the savanna ecosystems thereby affecting the global C budget and the sustainability of the local land use. We examined the biomass and the C, N, P, and S storages in above- and belowground biomass, in the organic layer, and in the top 2 m of the mineral soil (Anionic Acrustoxes) of three replicate plots of each of native Cerrado, Pinus caribaea Morelet plantations, productive and degraded Bracchiaria decumbens Stapf. pastures, and of conventional and no-tillage soybean cultivation. Aboveground biomass – in the cropping systems shortly before harvest – decreased in the order, Pinus (15 kg m−2) > Cerrado (2.3) > conventional tillage (1.9) > no tillage (1.5) > productive pasture (0.64) > degraded pasture (0.37) and belowground biomass in the order, Pinus (9.1) > Cerrado (3.0) > productive pasture (2.2) > degraded pasture (1.5) > conventional tillage (0.60) > no tillage (0.41). The aboveground biomass contained 1.1 (degraded pasture) to 19% (Pinus) of the total C storage, 0.3 (productive pasture, degraded pasture) to 3.5% of the total N storage, 0.3 (degraded pasture) to 2.1% (no tillage, conventional tillage) of the total P storage, and 0.3 (degraded pasture) to 3.7% (Pinus) of the total S storage of the ecosystems. Total C storage in the ecosystems was significantly larger in the Pinus stands (36 kg m−2) than in all other systems; differences among Cerrado (20), degraded pasture (19), productive pasture (20), no tillage (19), and conventional tillage (19) were small and not significant. All land-use systems had larger N (Pinus, 1.5; degraded pasture, 1.3; productive pasture, 1.4; no tillage, 1.4; conventional tillage, 1.4 kg m−2) and S storage (PI, 28; degraded pasture, 33; productive pasture, 34; no tillage, 36; conventional tillage, 38 g m−2) than the Cerrado (N, 1.2 kg; S, 26 g m−2). The P storages varied between 17 and 29 g m−2 and were not significantly different among the studied ecosystems. The N and S accumulations in the 12–20-year-old land-use systems were larger than the cumulative known fertilizer inputs indicating that there were unknown inputs possibly including the exploration of the deeper subsoil by deep-reaching roots and transfer of nutrients to the topsoil. Our results indicate that afforestation with Pinus trees has the potential to sequester large amounts of C while pasture degradation, no tillage, and conventional tillage tended to result in small C losses. Land use resulted in a marked accumulation of N and S relative to the Cerrado.

Biogeochemical consequences of the transformation of native Cerrado into Pinus caribaea plantations in Brazil

Under the same climatic and edaphic conditions, native savanna vegetation in Brazil, the Cerrado, shows a lower stature and canopy cover than planted Pinus caribaea Morelet forests. To assess the differences in biogeochemical element cycling we compared the nutrient economy of Cerrado and Pinus on three replicate plots of each forest type. The mean nutrient storage in the soil organic layer under Pinus (N: 2630; P: 141; K: 103; Ca: 131; Mg: 20 kg ha−1) was substantially higher than under Cerrado (N: 23; P: 1.2; K: 0.83; Ca: 5.8; Mg: 1.0 kg ha−1) probably because the Pinus roots explored a larger soil volume. The Pinus trees had a higher nutrient-use efficiency as indicated by higher mean litter mass per unit nutrient in litter (N: 108; P: 2290; K: 729; Ca: 1360; Mg: 5420; S: 1190; Fe: 2960; Mn: 9990, Zn: 145000) than the Cerrado trees (N: 94; P: 1810; K: 619; Ca: 302; Mg: 938, S: 746; Fe: 1800; Mn: 7880; Zn: 63700). Mean annual small litterfall collected in 0.25-m2 samplers between May 1997 and April 1999 was 2.1 Mg ha−1 in Cerrado and 7.8 in Pinus. The litterfall rates of the 1–3 week collection intervals correlated negatively with the soil matric potential indicating that litterfall was partly related to water stress. The fluxes of N (73 kg ha−1 year−1), P (3.7), K (11), S (7.0), and Mn (0.83) to the soil with litterfall under Pinus were greater than the litterfall+turnover of the grass/herbs layer under Cerrado (N: 39, P: 2.8, K: 8.6, S: 5.4, Mn: 0.79 kg ha−1 year−1), those of Zn (0.06–0.07) were similar, and those of Ca (Pinus: 5.9/Cerrado: 10), Mg (1.5/4.4), and Fe (2.9/4.0) were smaller. Mean residence times of the organic matter and of all elements were longer in the soil organic layer under Pinus (3.7–26 years in the Oi horizon, 8.1–907 years in the whole organic layer) than under Cerrado (0.22–3.6 years in the Oi horizon, the only organic horizon under Cerrado). Our results demonstrate that the main differences in biogeochemical element cycling between the Pinus forest and the Cerrado consisted of a larger nutrient storage in the organic layer, a higher nutrient-use efficiency, and slower nutrient release rates from the organic layer in the Pinus forest than in the Cerrado. Nutrient cycling as assessed by the nutrient fluxes with litterfall was only partly faster in the Pinus forest than in the Cerrado.

Nutrient concentrations in soil solution of some Brazilian Oxisols under conventional and no-tillage systems in the early part of the rainy season

In the South American savanna, no-tillage (NT) is implemented to improve the sustainability of cropping systems. At the beginning of the rainy season, however, more plant nutrients may be leached under NT than under conventional tillage (CT) because of more pronounced organic matter mineralisation and increased pore continuity. To test this hypothesis, we analysed the chemical composition of the soil solution under conventional (CT) and no-tillage (NT) soybean (Glycine max (L.) Merr.) fields in the Brazilian savanna (Cerrados). We collected the soil solution at 0.15, 0.3, 0.8, 1.2, and 2 m depth and the precipitation in 1- to 3-day intervals from 28 October to 23 December 1998 on plots under CT and NT, replicated 3 times. We determined pH, electrical conductivity (EC), Ca, K, Mg, Na, NO3– , NH4+, Cl–, and total organic carbon (TOC) concentrations in soil solution and precipitation. Soil solution pH under NT was 0.3–0.8 units lower than under CT and was inversely related to TOC concentrations (average under NT, 1.02; CT, 0.70 mmol C/L) at all depths. Average Cl– , Ca, and Mg concentrations at 0.15–0.3 m depth were significantly higher under CT (1.09, 1.1, and 0.25 mmol/L) than under NT (0.50, 0.83, and 0.17 mmol/L), respectively. No difference was observed in average Na (0.09 mmol/L) and NO3– concentrations (2.2 mmol/L) between CT and NT. At 0.8–2 m, average NO3– (0.30 mmol/L), Cl– (0.18 mmol/L), Ca (0.19 mmol/L), Mg (0.05 mmol/L), and Na (0.04 mmol/L) concentrations under CT were significantly lower than under NT (NO3– , 0.38; Cl– , 0.40; Ca, 0.23; Mg, 0.09; Na, 0.06 mmol/L). In the monitored period, the Cl– which had accumulated during the dry season and which was applied with KCl fertiliser on 29 October reached a depth of 0.3 m under CT and of 1.2m under NT. The results suggest higher mineralisation rates and faster leaching in the NT than in the CT systems, being the combined result of different plowing practices and different cropping sequences.

Nutrient input from the atmosphere into Brazilian savanna oxisols under corn

Above-canopy precipitation (ACP) reaches the soil under corn (Zea mays L.) as throughfall (TF) and stemflow (SF). We hypothesized that this results in heterogeneous nutrient inputs to soil and that the corn canopy modifies the chemical composition of ACP because of dry deposition and crop leaching. Therefore, we examined the quantity and quality of ACP, TF, and SF in corn fields on Oxisols of the Brazilian savanna during two vegetation periods and estimated the dry deposition rates with a Na tracer technique. Throughfall accounted for 70 to 75% of the ACP. Evaporation losses of intercepted water were close to zero. In TF and SF, volume-weighted mean (VWM) concentrations in μg L−1 of Ca (TF: 581/SF: 565), Cl− (826/1330), Cu (2.4/1.9), K (2110/5710), Mg (199/403), Mn (1.3/1.2), N (1550/770), Na (493/586), S (376/184), and Zn (9.3/24) were generally higher than in ACP (Ca: 117, Cl−: 265, Cu: 1.0, K: 152, Mg: 44, Mn: 0.48, N: 199, Na: 246, S: 62, and Zn: 5.6 μg L−1). The average contributions of SF to the total nutrient input were similar to its contribution to the total water input (27%) for Ca (27%), Mn (28%), and Na (30%), higher for Cl− (37%), Mg (43%), Zn (50%), and K (51%), and lower for Cu (23%), N (16%), and S (15%). This indicated leaching of Cl−, Mg, Zn, and K from the stems and uptake of Cu, N, and S by the plants. Dry deposition contributed 50 to 55% to the average total deposition during the rainy season (October-April) of 3520 g Ca (Ca), 8050 g Cl−, 35 g Cu, 4690 g K, 1370 g Mg, 15 g Mn, 7460 g N, 7590 g Na, 2090 g S, and 199 g Zn ha−1. Leaching from the corn canopy was most pronounced for K (41 kg ha−1) > Ca (5.1) > S (2.6) > Mg (2.4). On average, 76% of the 12 kg N ha−1 that reached the soil was organic, indicating that N was also leached. In contrast, there was almost no leaching of Mn (3.5 g ha−1) and, on average, even net uptake of 1.3 g Cu and 0.1 g Zn ha−1. The total deposition, on average, accounted for 3.9% (K) to 46% (Zn) of the nutrient demand of the corn plants. However, it represented <6.5% of the nutrient input with fertilizers. Our results demonstrate that the spatial distribution of the nutrient input to soils under corn is element-specific and that deposition contributes to the micronutrient nutrition of corn grown on nutrient-poor Oxisols.