Soil Nutrient Stocks Research Articles

Land-use changes and slope positions impact on the degradation of soil functions in nutrient stock within the Kalikungkuk micro watershed, East Java, Indonesia

Degradation of soil functions in storing and cycling nutrients may be related to topography and land-use change. The research aimed to analyze the impact of land-use changes and slope positions on soil function in nutrient stock within Kalikungkuk micro watershed of East Java, Indonesia. Four different land-uses such as vegetable crops, agroforestry, shrub and forest were selected with three slope positions (e.g. ridge, slope, and valley), and three replications of each. Soil samples were collected at 0-10, 10-30, 30-50, and 50-100 cm depth of soil. Variables measured included soil properties (e.g. bulk density, soil texture, pH, CEC, soil nutrients). Slope positions impact on differences in soil physical (i.e. soil bulk density, soil texture) and chemical (i.e. total N, exchangeable K) properties. In addition, forest conversion to other land-uses (i.e. agroforestry, shrub, vegetable crops) decreased soil nutrient concentration (i.e. total C, total N, Ca, Mg, Na), and consequently resulted in degradation of soil nutrient stocks of especially C and N. The strong positive correlation between soil nutrient stock (e.g. C and N) and vegetation cover such as canopy cover, basal area, and litter (r = 0.63 – 0.78, r table 1% = 0.39) showed the benefit of biodiversity in maintaining soil function on the nutrient stock.

Market access and resource endowment define the soil fertility status of smallholder farming systems of South‐Kivu, DR Congo

AbstractThis study verified the inter‐related effect of ‘market distance’, defined as walking time, ‘farm typology’, defined as resource endowment, and ‘site’, defined as geographic location with contrasting agro‐ecologies, as well as farmers’ indigenous knowledge on soil fertility variability in smallholder farming systems in two distinct regions (Bushumba, Mushinga) of South‐Kivu, DR Congo. A total of 384 soil samples were selected from representative farmers’ fields and analysed for soil pH, soil organic carbon (SOC) content and quality, as well as nutrient contents, using midDRIFTS (mid‐infrared diffuse reflectance Fourier transform spectroscopy) and wet chemistry analyses. MidDRIFTS was also used to calculate SOC stability indexes as SOC quality proxies. ‘Market distance’ and ‘farm typology’ were key determinants of soil fertility variability, both with contrasting trends in Bushumba and Mushinga. Decreasing soil fertility with increasing market distance was noted across all farm typologies. ‘Farm typology’ was related to exchangeable calcium and magnesium, while ‘site’ resulted in a difference of plant available phosphorus. SOC quality indexes were related to ‘site’, interacting with ‘market distance’. A ‘market distance’ effect became obvious in the medium wealthy and poor farms of Mushinga, where a lower SOC quality in remote fields plots was noted with increasing market distance. In agreement with farmers’ indigenous knowledge, soil fertility levels were higher in deep than shallow soils, which were reflected in higher nutrient stocks in deep soils receiving organic amendments. Our results inferred that soil fertility variability across smallholder farms must consider various inter‐related determinants as basis for site‐specific fertility management interventions.

Nutrient stocks of Japanese blue oak (Quercus glauca Thunb.) stands on different soil parent materials

Soil parent materials originating from different geologic settings represented broad differences in the forest nutrient environment, but few studies have been conducted on the relationships between soil parent materials and nutrient stocks in forest stands. This study was performed to compare the nutrient stocks of Japanese blue oak (Quercus glauca Thunb.) stands grown on forest soils inherited from two different parent materials, basalt and sandstone, in southern Korea. A total of 29 Japanese blue oak trees were destructively sampled (15 trees on basalt and 14 trees on sandstone) to compare the nutrient content of the tree components (stem wood, stem bark, branches, and leaves). Samples of the forest floor and a soil depth of 0–30 cm were collected to measure the nutrient stocks of the two parent materials. The mean nutrient concentrations of the tree components varied significantly between the basalt and sandstone parent materials. The mean carbon and potassium concentrations of stem wood were significantly higher in sandstone than in basalt, whereas the nitrogen concentration of stem wood and stem bark were lower in sandstone than in basalt (p < .05). A significantly higher carbon, nitrogen, potassium, and magnesium stocks of the forest floor were found in sandstone than in basalt. However, the soil carbon, nitrogen, calcium, and magnesium stocks at a depth of 0–30 cm were significantly higher in basalt than in sandstone. The results demonstrate that the aboveground nutrient concentration and belowground nutrient stocks of Japanese blue oak stands can be altered greatly by different parent materials.

Acid rain mediated nitrogen and sulfur deposition alters soil nitrogen, phosphorus and carbon fractions in a subtropical paddy

Agricultural ecosystems are globally important sinks of carbon and other nutrient elements. In China, acid rain events affect about 0.62 million km2, representing about 6.4% of total land area; however, the impacts of acid rain mediated nitrogen (N) and sulfur (S) depositions on soil organic carbon (SOC) fractions and nutrient stocks in paddy soils and implications for yield production under climate change are unclear. We conducted a field experiment during two annual crop seasons to determine the effects of simulated acid rain on SOC fractions and nutrients in a subtropical paddy in China. Acid rain treatments comprised solutions of HNO3 + H2SO4 to simulate N and S deposition at pH levels of 4.5, 3.5, and 2.5. The results showed that content of soil C fractions varied with acid rain pH. Acid rain led to increased SOC concentrations and decreased the ratios of soil labile organic carbon (LOC): SOC and dissolved organic carbon (DOC): SOC concentrations, independently of crop season and growth stage. Soil salinity was positively associated with SOC suggesting that higher levels of salinity inhibit C decomposition favoring SOC accumulation. Treatment effects of acid rain on soil microbial C and N depended on crop growth stage. Concentration of Fe2+ was positively correlated with DOC in early and late paddy soils under acid rain, possibly as a result of Fe2+ retention by DOC, when Fe3+ is reduced to Fe2+. Acid rain led to increases in soil TN, TP, available N, NH4+ concentration, and SOC, and decreases in ratios of DOC: SOC, indicating decreases in soil biological activity and mineralization processes. Increases in dead rice plant biomass under acid rain were consistent with the increase in soil N and P concentrations, due to reduced nutrient uptake, and higher levels of total SOC.

Prescribed burn frequency, vegetation cover, and management legacies influence soil fertility: Implications for restoration of imperiled pine barrens habitat

In fire-dependent ecosystems, the absence of fire can contribute to a positive feedback in which increased vegetation cover leads to increased accumulation of soil organic matter and nutrient stocks. These changes in turn can influence competitive shifts among plant communities, resulting in increased woody plant establishment, canopy closure, and ultimately leading toward mesophication. Poor soil conditions may be especially important for maintaining the open structure characteristic of pine barrens ecosystems, which are imperiled due to loss of key ecosystem processes such as fire and land conversion to cropland or pine plantations. Our objectives were to determine how soil characteristics are related to recent prescribed fire management, and how soils vary along gradients of current and historic vegetation cover in a barrens-forest mosaic in northern Wisconsin, USA. We sought to understand whether management with prescribed fire shifts soils toward barrens-type soil conditions, and whether soil conditions typify barrens habitat relative to shrub and forest habitat We analyzed organic (i.e. forest floor) and mineral soil horizons collected along gradients of recent prescribed burn history and current (barrens, pine woodlands, brush, and closed-canopy forest) and historic vegetation cover types (barrens, pine plantations, deciduous forests) to investigate the influence of each on specific components of soil fertility. Using a model selection approach, we found forest floor soil properties were most frequently associated with differences in current vegetation cover; for instance, pine woodland sites had greater organic matter stocks than barrens sites, and cation stocks were generally greater at brush sites than barrens and pine woodland sites. Some soil properties, including pH, however, appeared to be driven by prescribed burn frequency. Using ordination techniques to characterize multidimensional characterizations of soils, we identified a soil legacy effect related to historic vegetation cover and land management; native barrens sites had soil characteristics intermediate to restored barrens of pine woodland and deciduous forest origin. Our findings suggest restoration of pine plantations to barrens could benefit from fire activities that enhance consumption of the forest floor, while restoration of deciduous forest and brush habitats will likely be more related to the effective control of hardwood regeneration, after which soil conditions may return to a more archetypical barrens state.

Effect of disturbance by plateau pika on soil nitrogen stocks in alpine meadows

The presence of small burrowing herbivores often cause extensive disturbance to the grassland soil nutrient stocks. This study investigated the effect of small burrowing herbivore presence, the plateau pika (Ochotona curzoniae), and variation in disturbance intensity on soil nitrogen stocks at five alpine meadow sites. Disturbed plots occupied by plateau pikas consist of burrows and their associated bare soil patches in a matrix of continuous alpine meadow. The percentage of the bare soil area in a disturbed plot was used as a proxy for disturbance intensity of plateau pikas. This study showed that the soil total nitrogen stock was lower of bare soil than vegetated soil within disturbed plots, while ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), inorganic nitrogen and ammonium nitrogen/nitrate nitrogen ratio (ANR) were higher in bare soil than vegetated soil within the disturbed plots. This study further showed that the NH4+-N, inorganic nitrogen and ANR of disturbed plots were higher than those of undisturbed plots, whereas soil total nitrogen and the NO3−-N stock was not different between disturbed plots and undisturbed plots. This study also showed that the soil total nitrogen, NH4+-N and inorganic nitrogen stocks of disturbed plots were higher at intermediate disturbance intensities of plateau pikas, whereas the NO3−-N stock and ANR were not related to disturbance intensities. These results suggest that the NH4+-N and inorganic nitrogen stocks were higher in the presence of plateau pikas, and intermediate disturbance intensity of plateau pikas was beneficial for soil quality due to higher soil total nitrogen, NH4+-N and inorganic nitrogen stocks. The findings of this study present a possible approach for estimating how the presence of a small burrowing herbivore influences grassland soil nitrogen stock.

Effect of harvest residue management on soil properties of Eucalyptus hybrid and Acacia mangium plantations planted on steep slopes in northern Vietnam

Burning harvest residues during site preparation can compromise the soil-nutrient stock in short-rotation plantations, but this practice remains common in northern Vietnam. This study compared the effect of two contrasting harvest-residue treatments (burning vs retention) on soil total carbon (TC), total nitrogen (TN), extractable P (ext-P), exchangeable K (exch-K) and bulk density (BD) of two adjacent randomised complete-block trials, one of Eucalyptus hybrid (Eucalyptus urophylla × E. pellita) and the other of Acacia mangium planted on steep slopes. Harvest-residue management had no effect on soil properties of either E. hybrid or A. mangium two years after planting. Soil pH in E. hybrid increased and exch-K in A. mangium decreased during the first year; ext-P decreased over time in both species though this was only significant in the residue-retention treatment in A. mangium. Slope significantly influenced pH and TC of E. hybrid and TC and TN of A. mangium. It appeared that slope position and correlative factors such as surface runoff and erosion had led to the observed distribution of some soil properties along the steep slope.

The Effects of Crop Tree Management on the Fine Root Traits of Pinus massoniana in Sichuan Province, China

Pinus massoniana is an important tree species for wind protection and timber forests in Southern China. In recent years, P. massoniana plantations have been developed on more than 11,300,000 hm2 in southern China, but numerous problems have been observed, such as soil degradation, biodiversity reduction, and ecological functional decline. Crop tree management impacts on fine root development, which can be explained by the variations in the root orders. In this study, a 36-year-old P. massoniana plantation located in Huaying, Sichuan Province, was selected as the research field. In 2015, crop tree management was initiated, with a crop tree intensity of 150 trees per hectare. After 3 years of growth, fine roots of crop and noncrop trees were collected by the sector method with an angle of 15 degrees and a radius of 2 meters. We analyzed the morphological characteristics and biomass in different root orders, and explored their carbon and nitrogen contents. The results were as follows: (1) The specific root length (SRL), root length density (RLD), and surface root area (SRA) of the crop trees were larger than those of the noncrop trees; the SRL increased significantly from 0–0.5 m to 1–1.5 m from the stem. (2) The fine root biomass of the crop trees was significantly larger than that of the noncrop trees. The fine root biomass of the crop and the noncrop trees increased with the horizontal distance from the stem from 0–0.5 m to 1–1.5 m. The morphological indexes of the noncrop trees at the distances of 1–1.5 m and 1.5–2 m were significantly different, while those of the crop trees at those distances were not. (3) The fine root C content of the crop trees was significantly higher than that of the noncrop trees and varied significantly along a vertical distribution. The fine root N content of the crop trees was significantly higher than that of the noncrop trees, and the N content of topsoil was higher than that of deeper soil. In conclusion, our results indicated that crop tree management increased the production of a large-diameter wood of P. massoniana, which might be attributed to the improvement of soil permeability and nutrient stock, and thus, the enhancement of fine root quantity and water/nutrient absorption ability.

Changes in Carbon Stocks and Chemical Attributes of an Oxisol as a Result of Adoption Period of No-tillage System in the Brazilian Eastern Amazon

The conversion of forest areas to grain cropping has promoted a decrease in soil organic matter stocks in the Amazon. This process is most striking when the conventional cultivation system is used. In order to evaluate the changes in soil carbon and nutrient stocks resulting from the time of adoption of the no tillage system in a dystrophic Yellow Oxisol of the Brazilian Amazon biome, a study was conducted in a grain producing area in the northeastern of Pará, Brazil. The treatments corresponded to the following systems: CT6- conventional tillage system with six years of implementation; No-tillage system with 3 (NT3), 4 (NT4) and 7 (NT7) years of implementation. All systems were always cultivated in corn / soybean rotation. Deformed and non-deformed soil samples were collected on a the 2013 crop year at 0-10, 10-20 and 20-40 cm depths. Stocks of carbon (SC) and phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) were calculated by using the equivalent soil mass methodology. Regardless of depth, the NT showed higher SC values than the CT. The adoption of NT showed a tendency of increasing SC of the soil over time. Such increases were up to 36% of the NT7 compared to the CT6. In NT7, the stocks of K, Ca and Mg were higher in relation to PC6. The EC correlated positively with the stocks of K, Ca and Mg in the areas under NT, regardless of the time of system adoption, up to 40 cm deep, indicating improvements in the soil fertility.

Variation in soil properties under different cropping and other land-use systems in Dura catchment, Northern Ethiopia.

There are limited reports about the impacts of long-term cropping and land-use systems (CLUS) on soil properties and nutrient stocks under smallholder farmers' conditions in developing countries. The objective of this research was to examine variation in soil properties and OC and TN stocks across the different CLUS in Dura sub-catchment, northern Ethiopia. Surveys and discussions on field history were used to identify nine CLUS, namely, tef (Eragrostis tef (Zucc) Trot)) mono-cropping (TM), maize (Zea mays L.) mono-cropping (MM), cauliflower (Brassica oleracea var. botrytis)-maize intercropping (IC1), red beet (Beta Vulgaris)-maize intercropping (IC2), cauliflower-tef-maize rotation (R1), onion (Allium cepa L.)-maize-onion rotation (R2), tr eated gully (TG), untreated gully (UTG), and natural forest system (NF). A total of 27 composite soil samples were randomly collected from the CLUS for soil analysis. Data were subjected to one-way analysis of variance and PCA. The lowest and highest bulk density was determined from NF (1.19 Mg m-3) and UTG (1.77 Mg m-3), respectively. Soil pH, EC and CEC varied significantly among the CLUS. The highest CEC (50.3 cmolc kg-1) was reported under TG followed by NF. The highest soil OC stock (175.3 Mg C ha-1) and TN stock (13.6 Mg C ha-1) were found from NF. The PCA chosen soil properties explained 87% of the soil quality variability among the CLUS. Such soil properties and nutrient stocks variability among the CLUS suggested that introduction of suitable management practices that sustain the soil system of the CLUS with poor soil properties and nutrient stocks are crucial for the study area conditions.

Persistent anthropogenic legacies structure depth dependence of regenerating rooting systems and their functions

Biotically-mediated weathering helps to shape Earth’s surface. For example, plants expend carbon (C) to mobilize nutrients in forms whose relative abundances vary with depth. It thus is likely that trees’ nutrient acquisition strategies—their investment in rooting systems and exudates—may function differently following disturbance-induced changes in depth of rooting zones and soil nutrient stocks. These changes may persist across centuries. We test the hypothesis that plant C allocation for nutrient acquisition is depth dependent as a function of rooting system development and relative abundances of organic vs. mineral nutrient stocks. We further posit that patterns of belowground C allocation to nutrient acquisition reveal anthropogenic signatures through many decades of forest regeneration. To test this idea, we examined fine root abundances and rooting system C in organic acid exudates and exo-enzymes in tandem with depth distributions of organically- and mineral-bound P stocks. Our design permitted us to estimate C tradeoffs between organic vs. mineral nutrient benefits in paired forests with many similar aboveground traits but different ages: post-agricultural mixed-pine forests and older reference hardwoods. Fine roots were more abundant throughout the upper 2 m in reference forest soils than in regenerating stands. Rooting systems in all forests exhibited depth-dependent C allocations to nutrient acquisition reflecting relative abundances of organic vs. mineral bound P stocks. Further, organic vs. mineral stocks underwent redistribution with historic land use, producing distinct ecosystem nutritional economies. In reference forests, rooting systems are allocating C to relatively deep fine roots and low-C exudation strategies that can increase mobility of mineral-bound P stocks. Regenerating forests exhibit relatively shallower fine root distributions and more diverse exudation strategies reflecting more variable nutrient stocks. We observed these disparities in rooting systems’ depth and nutritional mechanisms even though the regenerating forests have attained aboveground biomass stocks similar to those in reference hardwood forests. These distinctions offer plausible belowground mechanisms for observations of continued C sink strength in relatively old forests, and have implications for soil C fates and soil development on timescales relevant to human lifetimes. As such, depth-dependent nutrient returns on plant C investments represent a subtle but consequential signal of the Anthropocene.

Simulating long-term carbon nitrogen and phosphorus biogeochemical cycling in agricultural environments

Understanding how agricultural practices alter biogeochemical cycles is vital for maintaining land productivity, food security, and other ecosystem services such as carbon sequestration. However, these are complex, highly coupled long-term processes that are difficult to observe or explore through empirical science alone. Models are required that capture the main anthropogenic disturbances, whilst operating across regions and long timescales, simulating both natural and agricultural environments, and shifts among these. Many biogeochemical models neglect agriculture or interactions between carbon and nutrient cycles, which is surprising given the scale of intervention in nitrogen and phosphorus cycles introduced by agriculture. This gap is addressed here, using a plant-soil model that simulates integrated soil carbon, nitrogen and phosphorus (CNP) cycling across natural, semi-natural and agricultural environments. The model is rigorously tested both spatially and temporally using data from long-term agricultural experiments across temperate environments. The model proved capable of reproducing the magnitude of and trends in soil nutrient stocks, and yield responses to nutrient addition. The model has potential to simulate anthropogenic effects on biogeochemical cycles across northern Europe, for long timescales (centuries) without site-specific calibration, using easily accessible input data. The results demonstrate that weatherable P from parent material has a considerable effect on modern pools of soil C and N, despite significant perturbation of nutrient cycling from agricultural practices, highlighting the need to integrate both geological and agricultural processes to understand effects of land-use change on food security, C storage and nutrient sustainability. The results suggest that an important process or source of P is currently missing in our understanding of agricultural biogeochemical cycles. The model could not explain how yields were sustained in plots with low P fertiliser addition. We suggest that plant access to organic P is a key uncertainty warranting further research, particularly given sustainability concerns surrounding rock sources of P fertiliser.

Nutrient status of cattle grazing systems in the western brazilian amazon

Low-input cultivated pastures to feed cattle have dominated land use after forest clearing for decades in the western Brazilian Amazon. This study was undertaken to help understand the inherent nutrient supply dynamics underwriting cattle performance on three farms in the state of Acre. We assessed soil chemical and physical properties associated over time with different land uses following forest clearing. This information permitted specifying a conceptual model of nutrient stocks and flows under the observed grazing system, which produced insights about the dynamics of soil nutrient degradation. Above ground forage mass, topsoil nutrient concentrations and soil bulk density were measured. Land covers were Brachiaria spp. grasses, a grass-Pueraria phaseoloides mix, cropland and forest. Most soil nutrient parameters initially decreased after clearing, gradually recovering over time with grass-only pastures; however, 20 yr-old pastures had 20% less forage mass. Most pasture system nutrients on these farms resided in topsoil and roots, where large stocks of mature forage supported soil fertility with recycled nutrients from litter. Estimates of partial topsoil nutrient balances were negative. This suggested that corresponding nutrient stocks and the accumulation of forage mass were probably maintained primarily through the sum of inflows from cattle excreta, the subsoil, soil organic matter, and litter mineralization with scant input of commercial fertilizer. Therefore, herd management to increase animal system productivity via higher stocking rates on vegetatively younger forage requires monitoring of nutrient stocks and flows and fertilization that assures replenishment of the nutrients extracted. Otherwise, rapid depletion of soil nutrient stocks will lead to system degradation and failure.

Under temperate climate, the conversion of grassland to arable land affects soil nutrient stocks and bacteria in a short term

Projected population growth and climate change will make it inevitable to convert neglected and marginal land into productive arable land. We investigate the influence of agricultural management practices on nutrient stocks and soil functions during the conversion of former extensively used grassland to arable land. Effects of grassland removal, tillage, intercropping with faba bean (Vicia faba) and its later incorporation were studied with respect to soil properties and bacterial community structure. Therefore, composite samples were collected with a core sampler from the topsoil (0–20 cm) in (a) the initial grassland, (b) the transitional phase during the vegetation period of V. faba, (c) after ploughing the legume in, and (d) untreated controls. In all samples, nitrate-N, ammonium-N, dissolved organic carbon (DOC) and total nitrogen bound (TNb) were analyzed and comparisons of the bacterial community structure after 16S-amplicon sequencing were performed to assess soil functions. Mineralization after grassland conversion followed by the biological nitrogen fixation of broad beans enhanced the nitrate-N content in bulk soil from 4 to almost 50 μg N g−1dw. Bacterial community structure on phylum level in bulk soil was dominated by Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, and Bacteroidetes and remained almost stable. However, alpha and beta-diversity analysis revealed a change of the bacterial composition at the final state of the conversion. This change was primarily driven by increasing abundances of the genera Massilia and Lysobacter, both members of the Proteobacteria, after the decay of the leguminous plant residues. Furthermore, increasing abundances of the family Gaiellaceae and its genus Gaiella fostered this change and were related to the decreasing carbon to nitrogen ratio. In short, gentle management strategies could replace the input of mineral fertilizer with the aim to contribute to future sustainable and intensified production even on converted grassland.

Long-term conservation tillage and nitrogen fertilization effects on soil aggregate distribution, nutrient stocks and enzymatic activities in bulk soil and occluded microaggregates

Conservation agriculture is globally recommended for increasing soil C and reducing greenhouse gases emissions by modifying soil physical, chemical and biological properties and processes. We assessed the impact of long-term conservation tillage and N fertilization in wheat-soybean rotation on soil aggregate distribution, nutrients stocks and functions of soil microorganisms related to C, N, P and S cycles at different aggregation scales in the Mediterranean area. A long-term field experiment was set up in a silt loam soil comparing two tillage intensities to bread wheat (Triticum aestivum L.) - soybean (Glycine max L. Merr.) rotation: conventional tillage (CT) and minimum tillage (MT). Two N fertilization levels were applied on bread wheat: 0 and 200 kg N ha−1 (N0 and N200, respectively). Under CT, almost 100% of the crop residues were incorporated in the 0–25 cm soil layer, whereas under MT approximately 50% were incorporated at 0–15-cm depth. Tillage was the most discriminant factor explaining 72% and 60% of total variance of soil parameters at 0–15 cm and 15–30 cm soil depth, respectively, whereas N fertilization explained 22% and 29% of total variance, respectively. All enzyme activities were higher under MT, whereas the majority of soil chemical parameters were higher under N200. Under MT a higher proportion of free microaggregates (+51%) was recorded compared to CT suggesting that in a silt loam soil MT had a greater potential to form macroaggregates. The proportion of small macroaggregates was not changed by tillage, but when this fraction was fractionated a higher proportion of occluded microaggregates was found under MT at 15–30 cm (+21%). In the occluded microaggregates, interaction of tillage x N fertilization explained 52% of total variance of soil parameters at 0–15 cm. The most discriminant parameters were the biochemical ones and SOC. All those parameters were higher in MT-N200. Specifically, SOC in occluded microaggregates was increased by N fertilization under MT (+16% at 0–15 cm; +84% at 15–30 cm), whereas it was decreased under CT (-46% at 0–15 cm; -15% at 15–30 cm). In addition, the synthetic indexes for enzymatic activities and for those involved in C-cycle were reduced by N fertilization under MT up to 37% and increased up to 87% under CT. In the Mediterranean area, maintaining or even increasing SOC conservation may require both reduced tillage systems and N fertilization, shifting microbial community towards toward taxa more effective in contrasting soil degradation.

Determination of Primary Mineral Content and Calcium Sources in Forest Soils using Electron Probe Microanalysis Mapping and Cluster Analysis

Although mineral dissolution is a fundamental soil forming process, primary mineral content of soils is rarely inventoried or quantified. Concerns about maintenance of forest soil nutrient stocks require better mineralogic data. In particular, to understand recovery from Ca losses induced by acid deposition and sustainability of intensive forest harvest, better inventory of primary Ca minerals is needed. We developed a method based on electron probe micro‐analysis to quantify primary mineral concentrations in soil. Samples analyzed from three sites in the glaciated northeastern United States spanned a bulk Ca concentration of 0.03 to 0.94%. Plagioclase was the dominant Ca‐bearing mineral at two sites while apatite was the only Ca‐bearing mineral found in all three samples and was the dominant calcium source at one site. A variety of other Ca silicate minerals were found in trace amounts. Electron probe microanalysis (EPMA) proved more sensitive in detecting minor and trace Ca bearing minerals than standard XRD procedures. The Ca‐bearing minerals detected by EPMA matched those expected based on the lithologic composition of the glacial till and were consistent with measured bulk soil Ca content by lithium‐borate fusion. Taking into account the Ca concentration in each mineral and each mineral's abundance in the sample, this inventory provided a complete accounting of Ca sources.

Interactive effects of conservation tillage, residue management, and nitrogen fertilizer application on soil properties under maize-cotton rotation system on highly weathered soils of West Africa

Loss of topsoil, enriched with nutrients, reduces soil fertility, and is one of the major impediments to sustainable crop production in West Africa. Appropriate management practices can lead to a stable restoration of land’s capacity to provide adequate ecosystem services. Thus, our study aimed to investigate the impact of alternative management practices and their interactions on topsoil (0–20 cm) organic carbon (SOCd), nutrient stocks [total nitrogen (STNd), phosphorus (SPd) and potassium (SKd)] under a maize-cotton rotation system on highly weathered soils of West Africa. To this end, on-farm trials were set up on four sites in the sub-humid Savanna of West Africa (2 in Benin (St1 and St2), and 2 in Burkina-Faso (St3 and St4)) in a strip-split plot layout, where 2 levels of tillage (contour ridge tillage, Ct and reduced tillage, Rt) were considered as main plot factor, and sub-plot factors included 2 levels of crop residue management (removed, CRr and incorporated, CRi), and 2 levels of N fertilizer (control, N0 and recommended rate, Nr). In 2016, after 5 cycles of annual maize-cotton rotation (2012–2016), the largest pool of soil nutrients was recorded on St3 (Haplic Lixisol, footslope in Benin), while the lowest content was observed on St1 (Ferric Lixisol, footslope in Burkina). When comparing the treatments, we found that Ct combined with CRi improved soil nutrient stocks in upslope sites, St2 (Eutric Plinthosol, upslope in Burkina) and St4 (Plinthic Lixisol, upslope in Benin), which are more prone to erosion. At the same time, footslope sites (St1 and St3) benefited from Rt coupled with CRi. CRi promoted an increase in SPd and SKd on all sites except St1 (Haplic Lixisol on footslope). The application of recommended dose of N fertilizer improved STNd under the Ct system in upslope regions and under the Rt system in footslope regions. However, no significant difference was observed for soil pH among the treatments across all sites. In summary, the efficiency of practices for conservation of soil nutrient stocks was closely related to landscape position of the field, which was correlated with soil moisture, textural class, and gravel content. Consequently, site-adapted tillage practices combined with residue incorporation are crucial for sustainable soil fertility management and crop productivity under maize-cotton rotation in smallholder production systems in West Africa.

Land Use Systems, Soil Texture, Control Carbon and Nitrogen Storages in the Forest Soil of UB Forest, Indonesia

Differences in land use systems may resulted in different soil cover, litter input, and soil management practices, and consequently affect to soil nutrient stock. The study aimed to assess soil carbon (C) and nitrogen (N) storages on various soil depths from difference land use systems within UB forest. The research was conducted in UB forest, Malang – Indonesia, from April to November 2017. Soil sample was collected from four soil depths (0-0.1, 0.1-0.3, 0.3-0.5, and 0.5-1.0 m) within five land use systems, including (1) protected area; (2) pine + coffee; (3) pine + crops; (4) mahogany + coffee and (5) mahogany + crops, each with three replicate plots. Soil C and N concentrations, soil texture, and bulk density, were measured. The study showed significant difference in soil C and N storages among land use systems. In 0.5 m depth of soil, soil C and N storages was higher in protected area (64% and 53%, respectively) as compared to other land use systems. The result support clay content controls soil C and N stock, whereas vegetation determines soil N stocks. Therefore, proper management in vegetation and soil were needed to conserve soil C and N storages.

Changes in soil organic carbon and nutrient stocks in conventional selective logging versus reduced-impact logging in rainforests on highly weathered soils in Southern Cameroon

Although disturbances associated with selective logging can cause pronounced changes in soil characteristics and nutrient stocks, such information is very limited for highly weathered soils in Africa. We assessed the effects of reduced impact logging (RIL, with a 30-year rotation management plan) and conventional logging (CL, without a management plan) on physical and biochemical characteristics of Ferralsol soils that developed on pre-Cambrian rocks in rainforests of Cameroon. Five to seven months after the logging operations were completed, we mapped the CL and RIL sites and quantified the disturbed areas: felling gaps, skidding trails, logging decks and roads. We selected four replicate plots at each site that encompassed these four disturbed strata and an adjacent undisturbed area as the reference. At each disturbed stratum and reference area per plot, we took soil samples down to 50 cm, and quantified soil physical and biochemical characteristics. Nutrient exports with timber harvest were also quantified.The logging intensity was very low with removals of 0.2 and 0.3 tree per hectare, and the ground area disturbed accounted only 5.2% and 4.0% of the total area in CL and RIL, respectively. In terms of area disturbance for each harvested tree, CL had 753 m2 tree−1 more affected ground area than RIL. Roads and logging decks were the most affected by logging operations, where effective cation exchange capacity, soil organic carbon (SOC), total nitrogen (N), Bray-extractable phosphorus (P) and exchangeable aluminum decreased whereas pH, 15N natural abundance and exchangeable manganese increased compared to the undisturbed reference area (P < 0.01–0.04). The disturbed area showed overall reductions of 21–29% in SOC, N and P stocks relative to the reference areas (P = 0.02–0.07). The amounts of C, N, P and base cations exported with harvested timber were only 0.4–5.9% of the changes in stocks of these elements in the disturbed strata. Nutrient reductions in the soil and exports through timber harvest were comparable between CL and RIL, after one logging event in this very low intensity logging systems. Our results suggest that unplanned operations together with frequent re-logging inherent to CL can increase area damage and enhance changes in SOC and nutrients as opposed to RIL, which may affect the recovery of the succeeding vegetation.

Soil nutrient stocks are maintained over multiple rotations in Brazilian Eucalyptus plantations

Intensive management in tropical plantation forestry has increased global wood production per unit of time and land. Eucalyptus trees in southeastern Brazil grow exceptionally fast, even on the highly weathered and nutrient-poor soils of the Atlantic Forest and Cerrado biomes. By remeasuring plantation soils after twelve years and 1–2 rotations, we investigated how established plantations alter soil stocks of carbon, nitrogen, calcium, potassium, and phosphorus, and whether any changes might limit future plantation productivity. We hypothesized that each harvest cycle would deplete soil stocks of nitrogen, because less nitrogen is often added in fertilizer than is removed in wood, and that the balance between harvest and fertilizer would also dictate changes in stocks of other nutrients. In 2004 and 2016, we sampled soils to a depth of 100 cm in plantations and adjacent pastures and native vegetation reserves, and compared total nutrient stocks across time and vegetation type. We found that nutrients were not significantly depleted over time, and that soil stocks of carbon and nutrients in the plantations all tended to increase, with significant increases in the top 20 cm of 20% for potassium in the Atlantic Forest biome, and 23% for carbon and more than 500% for calcium in the Cerrado. Changes in soil nutrient stocks can be attributed in part to both fertilizer inputs and redistribution from changing stocks of biomass. We also observed changes over time and substantial spatial heterogeneity in nutrient stocks under non-plantation vegetation, highlighting the difficulties of using other vegetation types as static “controls” to assess the effects of plantations on soils. Overall, soil nutrient depletion does not appear to threaten sustainability in these intensive plantation forests over the time period studied.