Distribution Of Soil Nutrients Research Articles

Moldboard Plowing in Wheat–Fallow Systems of the Pacific Northwest: Effect on Yields, Organic Matter

A two‐year winter wheat–fallow system in the Pacific Northwest is practiced in areas with annual precipitation <16 inches. Wheat is planted in the fall and harvested in the summer, followed by 13 to 14 months of fallow. The summer fallowing often involves different types of tillage practices to facilitate water storage and weed control, which can influence vertical distribution of soil acidity and nutrients in the profile, possibly affecting crop yields. Long‐term studies could help us understand soil nutrients and yield responses across different tillage and N rate applications. Earn 0.5 CEUs in Soil & Water Management by reading the article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Nutrient foraging ability promotes intraspecific competitiveness in the clonal plant Hydrocotyle vulgaris

Many plant species forage for nutrients by accumulating more biomass or ramets where soil nutrient availability is high. Nutrient foraging ability differs between species and between genotypes within species, can increase plant performance when nutrients are patchy, and may lead to differences in competitive ability and have community-level effects. Effects of intraspecific variation in nutrient foraging ability could be particularly strong in clonal species, in which individual genotypes can form large clones and persist for long times. We tested the hypotheses that clones with greater foraging ability (1) have greater ability to compete with other clones of the same species but (2) experience greater competition within a clone. Sets of clonal fragments of five clones of the perennial, creeping herb Hydrocotyle vulgaris were grown alone, with a fragment of a different clone, or with a second fragment of the same clone in pots with a uniform or patchy distribution of soil nutrients. Consistent with the first hypothesis, foraging ability and between-clone competitiveness as measured by less negative competitive response were positively related when nutrients were patchy but not when they were uniform. Contrary to the second hypothesis, foraging and within-clone competitiveness were negatively related. Intraspecific competition both between and within clones could thus select for greater foraging ability. If this in turn increases ability to compete with other species, it may help explain the dominance of some clonal species.

Effect of Long-Term Fertilization on Aggregate Size Distribution and Nutrient Accumulation in Aeolian Sandy Soil.

Soil aggregates are the material basis of soil structure and important carriers of nutrients. Long-term application of organic and inorganic fertilizers can affect the composition of soil aggregates to varying degrees, which in turn affects the distribution and storage of soil nutrients. We report the results of a 15-year long-term field-based test of aeolian sandy soil and used the wet sieve method to analyze the stability of water-stable aggregates, as well as the distribution characteristics of nutrients in different particle size aggregates. Our results show that long-term application of organic fertilizer (M3) and combined organic–inorganic treatments (NPK1-M1, NPK1-M2, and NPK1-M3) help to increase the amount of organic carbon, inorganic carbon, and cation exchange in the macro-aggregates, and the improvement rates are 92–103%, 8–28%, and 74–85%, respectively. The organic content of the fertilizers also promotes the formation of macro-aggregates, and the stability of aggregates increase from 0.24 to 0.45. In contrast, the application of inorganic fertilizers (NPK1, NPK2, and NPK3) has no marked effect on the formation and stability of macro-aggregates; the application of inorganic fertilizers can merely maintain the organic carbon content of the soil. Correlation analysis shows that the application of organic fertilizers and chemical (inorganic) fertilizers containing phosphorus and potassium can markedly increase the content and reserves of available phosphorus and potassium across all aggregate sizes, and there is a significant positive correlation between these parameters and the amount of applied fertilizer (p < 0.05). Aggregates of various sizes in aeolian sandy soils in arid areas have the potential for greater nutrient storage. Therefore, organic fertilizers can be used in the agricultural production process to improve soil structure and fertility.

Freeze\u2013thaw cycle frequency affects root growth of alpine meadow through changing soil moisture and nutrients

Alpine meadows grow in alpine regions and play an important role in the production and life of alpine regions. As a unique feature of alpine regions, freeze–thaw cycles (FTCs) affect the growth of alpine meadows. However, with climate change, the change in the freeze–thaw cycle frequency (FTCF) has become obvious. These changes affect the content and distribution of soil moisture and nutrients, as well as the growth of roots in the alpine meadow. Therefore, based on the analysis of FTCF in the Nagqu River Basin, the characteristics of soil moisture, nutrients, and alpine meadow roots are analyzed, thus revealing the influence mechanism of FTCF on the root growth of alpine meadows. The results highlight three major findings. (1) Compared with the low-frequency mode (LFM), the moisture at 0–20, 20–40, and 40–60 cm in the high-frequency mode (HFM) has decreased by 30.74%, 52.89%, and 47.52%, respectively. Additionally, in HFM the contents of soil hydrolysable nitrogen (HN), available K (AK), and microbial biomass carbon (MBC) at the same depth are lower than those in LFM. (2) The original distribution of soil moisture at 0–60 cm has gradually increased from the surface to the bottom. However, with the increase in FTCF, the distribution of the soil moisture now means that the soil moisture at the surface (0–20 cm) and the deeper layers (40–60 cm) is higher than that in the middle (20–40 cm). (3) With the increase in FTCF, the growth mode of alpine meadow roots has changed from vertical extension to horizontal divergence; the distribution range of roots has changed from 0–40 cm to 0–20 cm; the length, surface area, and volume of 0–0.5 mm roots have increased by 20.95 cm, 1.90 cm2, and 0.014 cm3; and the corresponding specific gravity has increased by 9.09%, 13.50%, and 12.14%, respectively. This study provides a theoretical basis for predicting the growth mode of alpine meadow roots in the Nagqu River Basin under the influence of climate change and provides guidance for protecting the ecology of alpine regions and mitigating and solving global climate change.

Spatio-Temporal Variation in Soil Nutrients and Plant Recovery across a Fire-Severity Gradient in Old-Growth Araucaria-Nothofagus Forests of South-Central Chile

Forest fires can alter essential ecosystem processes, including soil nutrient cycling, potentially cascading into permanent vegetation changes. This is key to elucidate in ecosystems where fires are infrequent. We assessed the effects of fire severity on the spatio-temporal response of soil nutrients and plant diversity in old-growth forests of south-central Chile, 1, 2, and 3 years after a fire that occurred in 2015. Within ancient, old-growth Araucaria araucana (Mol.) K. Koch and Nothofagus pumilio (Poepp. and Endl.) Krasser forests, ranging from areas burned with fire of high severity to unburned forests, we evaluated nitrogen (N), phosphorus (P), potassium (K), and soil organic matter (SOM) content using spatial interpolation to predict their spatial distribution and assessed their availability over time. We also assessed plant species richness and abundance following the fire. The availability of N noticeably increased during the first year after fire but rapidly decreased in the following years, especially in areas of high fire severity. P, K, and SOM were less affected by the fire, remaining more constant over time. In the short term, plant species richness and diversity significantly decreased in severely burned areas, but over time, they became more similar to those of the unburned forests. The time since a fire and its severity determine a heterogeneous distribution of soil nutrients, with N shifting to a significantly lower availability after fire, which was more notable in areas of high fire severity. Here, vegetation exhibited a decrease in plant diversity and the establishment of exotic species, likely producing cascading effects at the community level.

Seasonal variations of some soil nutrients in a natural and an agricultural olive grove in Adana, Turkey.

The bioavailability and cycling of nutrients in soil are two of the most important factors for healthy plant growth and development in natural and agricultural ecosystems. Seasonal variations of some soil macronutrient (phosphorus and potassium) and micronutrient (copper, manganese, and zinc) contents were investigated in a natural olive (Olea europaea L.) grove (NO) and an agricultural olive gene garden (OGG) located in Adana, Turkey. Soils were sampled at 0-10cm and at 10-20cm depth in the months of November, February, May, and August between 2013 and 2015. Soil phosphorus, potassium, copper, manganese, and zinc contents were in the range between 0.37 and 8.65mgkg-1, 181.81 and 1030.67mgkg-1, 1.41 and 2.74mgkg-1, 13.88 and 51.06mgkg-1, and 0.39 and 2.27mgkg-1, respectively. All soil nutrients significantly decreased as soil depth increased in all sampling times (P < 0.05). In general, significant seasonal effects were observed in all soil nutrients at 0-10cm depth that was more variable than at 10-20cm depth. Soil phosphorus negatively and positively correlated with soil potassium in NO and in OGG at 0-10cm depth, respectively (P < 0.05). Soil zinc was negatively and positively correlated with soil phosphorus in NO and in OGG at 10-20cm depth, respectively (P < 0.05). In conclusion, soil depth might be a more important factor than seasonality on the vertical distribution of soil nutrients in olive groves. In addition, correlations between soil nutrients in this study should be taken into consideration for the optimum management of agricultural practices in biological olive groves.

Distribution and enrichment characteristics of soil nutrients in the nebkhas profile of Nitraria tangutorum in Gahai Lake Area, Qaidam Basin.

As a special bio-geomorphic landscape in the Qaidam desert area, Nitraria tangutorum nebkhas play a critical role in fixing quicksand, improving soil quality, and maintaining the stability of regional ecological environment. Taking the N. tangutorum nebkhas with coverage of approximately 15%, 25%, 45% and 60% in Gahai Lake area of Qaidam Basin as the research objects, we analyzed the vertical distribution and enrichment characteristics of soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP) and available potassium (AK). The results showed that the contents of SOM, TN, TP, TK, AN, AP and AK varied in the range of 1.67-10.22 g·kg-1, 0.05-0.42 g·kg-1, 0.31-0.54 g·kg-1, 15.87-18.84 g·kg-1, 2.26-11.68 mg·kg-1, 0.80-15.00 mg·kg-1 and 45-161 mg·kg-1, respectively. Vertically, soil nutrients in the N. tangutorum nebkhas with 15% coverage showed a decreasing trend first then increased, and then decreased again with the increase of soil depth, except for TP, which did not show any significant change. In the nebkhas with 25%, 45% and 60% coverage, SOM, TN, AN, TP and AP all showed a decreasing trend with increasing soil depth ,whereas TK and AK did not change significantly with soil layer. Above the nebkhas ground level of N. tangutorum, SOM, TN, TK, AN, AP and AK were all enriched, especially in the surface layer.Aamong all the nutrients, the enrichment rate of AN reached 5.19. In addition, below the nebkhas ground level of N. tangutorum, TN, AN, TK, AK and AP also showed enrichment. SOM, TN, AN, TP, AP, TK and AK were all significantly positively correlated with soil water content, and negatively correlated with altitude. All nutrients except TP were mainly affected by altitude. In conclusion, soil nutrient content of N. tangutorum nebkhas was the highest in the surface layer, the enrichment effect of which was not only reflected in the interior of the nebkhas, but also below the ground level of the nebkhas. Our results could provide reference for the scientific utilization of N. tangutorum nebkhas and ecological environment protection in Qaidam Basin area.

Analysis of Spatial Variability and Influencing Factors of Soil Nutrients in Western China: A Case Study of the Daliuta Mining Area

An understanding of the spatial variation and influence factors of soil nutrients in mining areas can provide a reference for land reclamation and ecological restoration. Daliuta was used as the study area. The spatial variability of soil nutrients was analyzed using traditional statistics and geostatistics. The effects of topography, mining history, and soil erosion were discussed. The results indicate that the soil pH of the Daliuta mining area is slightly acidic to slightly alkaline, and the soil organic matter, available nitrogen, available phosphorus, and available potassium belonged to the five levels (very low), six (extremely low), five (extremely low), and four (moderately low), respectively. The soil water and salt content indicated that the soil environment in the mining area is arid and has normal levels of salinity. The organic matter, available nitrogen, available phosphorus, available potassium, and soil salt varied moderately, and the pH did not change much, while the soil water varied strongly. The organic matter, pH, and soil salinity are moderately spatially autocorrelated, and the available nitrogen, available phosphorus, available potassium, and soil water are weakly spatially autocorrelated. Each nutrient index had a certain spatial trend effect. The slope, aspect, elevation, and topographic wetness index are the primary topographic factors that control the spatial distribution of soil nutrients. The organic matter, pH, and soil salinity are moderately spatially autocorrelated, and the available nitrogen, available phosphorus, available potassium, and soil water are weakly spatially autocorrelated. Each nutrient index had a certain spatial trend effect. The slope, aspect, elevation, and topographic wetness index are the primary topographic factors that control the spatial distribution of soil nutrients. Soil erosion and mining history are also important factors that lead to the spatial variation of soil nutrients.

Spatial changes of nutrients and metallic contaminants in topsoil with multi-geostatistical approaches in a large-size watershed

Appropriate assessment on concerned soil contaminants spatially is of importance for decision-makers and stakeholders to make efficient mitigation countermeasures. In this study, we applied multiple geostatistical approaches to explore soil nutrient and metallic contaminant distributions in a large river watershed in Thailand, and to compare their performances in predicting spatial distribution patterns of the concerned soil contaminants under suitable application scenarios. The total carbon, nitrogen and phosphorous in surface soils over the whole watershed were measured with their maximum concentrations up to 131.47, 9.24, 5.33 g·kg−1, respectively, while the concentrations of eight metallic elements (Cu, Zn, Pb, Cd, Hg, As, Cr, and Ni) were 933.00, 6862.50, 373.00, 6.22, 1.15, 178.53, 761.11, and 372.44 mg·kg−1, respectively. It was found that the conditional interpolation approaches such as land use stratified inverse distance weighted and land use stratified original kriging provided better boundary details than original interpolations, with substantially reduced root mean square errors (up to 28% for nutrients and 54% for specific metals) and mean relative errors (up to 38% for nutrients and specific metals respectively) in predicting the spatial patterns of soil nutrients and several land use specific metals (Cu, Zn, Cd, and Pb). The global accuracies were equivalent or higher than those of geographically weighted regression. Nonetheless, the prediction accuracy for Cr, Ni, As, and Hg could not be improved using the land use stratified interpolation because their sources and pathways were not significantly correlated with land use types in the watershed, as reflected by the results of analysis of variance with post hoc test (p ≤ 0.05) and principal component analysis.

Spatial heterogeneity of soil nutrients in black soil areas of Northeast China

AbstractExploring the distribution and evolution of soil nutrients, it is needed to maintain quality of land and ensure food production. Based on geostatistical theory, 1,054 soil sites were selected from the surface (0–20 cm) of the typical black soil area in Northeast China. The spatial structure of soil pH, alkali‐hydrolyzed N, effective P, and available K was investigated using Kriging and spatial statistics. The soils in the study area are acidic, alkali‐hydrolyzed N, effective P, and available K content at moderate to high levels. Coefficients of variation for various nutrients ranged from 5 to 80%, all showing moderate variation. The pH, alkali‐hydrolyzed N, effective P, and available K increased from South to North, the value of soil nutrients near the city were high. The results provide reference values for future work targeted at improving food security and reducing the effect on the environment.

基于EDEM的小麦分层施肥开沟器设计及参数优化

Applying different types of fertilizers to different depths of soil according to demand is advantageous in that it can optimize the distribution of nutrients in arable soil, adjust the nutrient supply of each growth stage of wheat, and increase grain yield. In the study, a layered fertilization opener that could realize the layered fertilization was developed. The interaction model between the opener, fertilizer and soil was established using EDEM simulation software. A response surface analysis was used to determine the optimal parameters of the opener. Specifically, the horizontal distance between the fertilizer drop openings was 140 mm, the machine speed was 1.05 m/s, and the angle of the opener was 37°. Furthermore, field experiments demonstrated that the average depth of upper layer was 8.39 cm, the average depth of middle layer was 16.465 cm, the average depth of lower layer was 24.025 cm, the average spacing of upper layer was 8.075 cm, and the average spacing of lower layer was 7.6 cm. The corresponding findings demonstrated that the layering effect of the opener met the requirements of the fertilization standard.

Soil water, nutrient distribution and use efficiencies under different water and fertilizer coupling in an apple–maize alley cropping system in the Loess Plateau, China

Soil water and nutrients are the main factors that restrict the stable development of alley cropping systems in the Loess Plateau of west Shanxi, China. Field experiments were conducted during 2014–2016 to investigate the effects of water and fertilizer coupling regulation on soil water, nutrient distribution and their use efficiencies in a typical apple–maize alley cropping system in the area. There were three upper limits for irrigation according to appropriate ranges of soil moisture for apple and maize, 50% (W1), 65% (W2) and 85% (W3) of field capacity (Fc) for the 0–60 cm soil layer, coupled with three nitrogen/phosphorus/potassium compound fertilizer levels of F1 (289.0/118.0/118.0 kg∙ha−1), F2 (421.4/168.8/168.8 kg∙ha−1), and F3 (537.0/219.0/219.0 kg∙ha−1) and a CK (rain fed, no irrigation or fertilizer) as a control, making a total of 10 treatments. The results indicated that the horizontal and vertical soil water content (SWC) increased with distance from the tree row and with soil depth, respectively. The SWC near the maize belts was greater than near the tree line, and this was reversed with the increase of intercropping years. In the horizontal direction, the soil nutrient content (SNC) for each indicator increased with distance from the tree row, with the maximum value occurring at 2.5 m. In the vertical direction, SNC decreased with soil depth, with the maximum value at 0–20 cm. The 85% Fc combined with 70% empirical fertilizer application amount resulted in the maximum grain yield and partial factor productivity (PFP). Irrigation water use efficiency (IWUE) was highest for the F1 level. Multivariate and spatial analyses showed that a range of 50–65% Fc combined with 70% empirical fertilizer application was suitable for optimal irrigation and fertilization management of this alley cropping system considering the integrated benefits of maize yield, IWUE and PFP.

Earthworms Modulate Impacts of Soil Heterogeneity on Plant Growth at Different Spatial Scales.

Soil heterogeneity (uneven distribution of soil nutrients and/or other properties) is ubiquitous in nature and can greatly affect plant growth. As earthworm activity can influence nutrient redistribution in the soil, we hypothesize that earthworms may alter the effect of soil heterogeneity on plant growth and this effect may depend on the scale of soil heterogeneity. To test these hypotheses, we grew the clonal grass Leymus chinensis in three soil treatments (heterogeneous large vs. heterogeneous small patch vs. homogeneous soil treatment) with or without earthworms [i.e., Eisenia fetida Savigny (Lumbricidae, epigeic redworm)]. In the heterogeneous treatments, the soil consisted of patches with and without 15N-labeled litter (referred to as high- and low-quality patches, respectively), and in the homogeneous treatment, the soil was an even mixture of the two types of soil patches. Biomass of L. chinensis was significantly higher in the high- than in the low-quality patches, showing the foraging response; this foraging response occurred at both scales and under both earthworm treatments. Compared to the homogeneous treatment, the heterogeneous large patch treatment increased biomass of L. chinensis without earthworms, but decreased it with earthworms. In contrast, biomass of L. chinensis in the heterogeneous small patch treatment did not differ from that in the homogeneous treatment, irrespective of earthworms. Belowground biomass was much greater in the heterogeneous small than in the heterogeneous large patch treatment without earthworms, but it did not differ between these two scale treatments with earthworms. In the heterogeneous treatments, soil 15N was greater in the high- than in the low-quality patches, but this effect became much weaker with than without earthworms, suggesting that earthworm activity homogenized the soil. We conclude that earthworms can change the impact of soil heterogeneity on plant growth via homogenizing the soil, and that this effect of earthworms varies with patch scale. Such scale-dependent interactive effects of soil heterogeneity and earthworms could be a potential mechanism modulating plant community structure and productivity.

Water depth rather than substrate heterogeneity affects the clonal performance of the stoloniferous submerged plant, Vallisneria spiralis L

Environmental heterogeneity profoundly influences the performance of clonal plants. To evaluate the effects of substrate patchiness and different water depths on clonal performance, we subjected the stoloniferous submerged plant Vallisneria spiralis L. to different patchy substrates and water depths. We measured several growth traits. We found that ramet number, leaf number, and stolon length decreased, and ramet height, spacer thickness, and biomass increased with increasing water depth. We saw no significant trait variations across different substrates. Furthermore, the trait allocation – the distribution of trait values in different patches of heterogeneous substrates – was consistent in most treatments. Clonal integration homogenized the effects of substrate patchiness via resource exchange through interconnected ramets. The ability to use water nutrients may enable submerged plants to alleviate the uneven distribution of soil nutrients in patchy substrates. Additionally, the simple root structure and weak root functions curtail submerged plants in obtaining sufficient nutrients from soil. Water depth rather than substrate heterogeneity determined the plant performance of V. spiralis.

Effects of compost tea on the spatial distribution of soil nutrients and growth of cotton under different fertilization strategies

Compost tea comes from a wide range of sources and can provide nutrients for crops and improve soil quality. In order to explore the effects of fertilization frequencies of compost tea on the spatial distribution of nutrients and the uptake by cotton, a trial comprised no fertilization treatment (CK) and three fertilizer treatments, that is, the application of a fixed amount of fertilizer at four (F3), two (F5), or one (F9) irrigation cycle, and each irrigation cycle was 10 days. The total amount of nutrients (N, P2O5, K2O) in fertilization treatment were all 18 g, and their amount of fertilization each time was 1/3, 1/5 and 1/9 of the total fertilizer, respectively. The results showed that in 0–10 cm soil layers, high-frequency fertilization (F9) reduced the soil pH by 5.6% compared with F3, the soil nutrient content of F3 treatment at seedling stage was significantly higher than that of the other two treatments by 71.9%–272.3%, however, the 20–40 cm soil layer was hardly affected by fertilization; The nutrient accumulation of cotton in F3 treatment was 17.1%–32.4% higher than that in the other two treatments, and the highest dry matter and recovery efficiency were also obtained under the F3 treatment. In conclusion, increasing the proportion of fertilization in seedling stage (F3) can increase the uptake and utilization of nutrients by cotton; While high-frequency fertilization (F9) can reduce the pH of calcareous soil. This study provides a basis for fertilizer optimization and soil quality improvement of composted tea.

Soil nutrient evolution under different vegetation types in semiarid loess area

The soil nutrient characteristics under three vegetation types of arbor ( I ), shrub ( II ) and herb ( III ) were studied by mathematical statistics method combined with field investigation and indoor detection analysis. The change characteristics of soil nutrients under different land use patterns were discussed. The results showed that the average contents of soil organic matter, total nitrogen, available phosphorus and available potassium were 21.30 and 0.65 g/kg, 3.67 and 67.61 mg/kg, respectively. Compared with grassland, woodland has better effect on fertilizer conservation in the Loess Plateau. In the process of soil nutrient improvement, the nutrient indexes such as organic matter, total nitrogen, available phosphorus and available potassium increased synchronously, and the soil alkaline environment that was not conducive to plant growth was also gradually improved. In the correlation between soil nutrients, available phosphorus and available potassium have good relative independence. In the future, organic fertilizer should be applied in this area, and nitrogen and phosphorus fertilizers should be supplemented to improve soil organic matter, nitrogen and phosphorus content, and to ensure soil nutrient balance by optimizing fertilization methods. In addition, in the case of uneven distribution of soil nutrients in the soil profile, it is recommended to take appropriate soil ploughing and reasonable human management measures to improve soil nutrient status, achieve high-quality sustainable development of soil, and promote the positive succession of vegetation communities. Bangladesh J. Bot. 50(3): 969-976, 2021 (September) Special

Prediction of Regional Forest Soil Nutrients Based on Gaofen-1 Remote Sensing Data

The study on the spatial distribution of forest soil nutrients is important not only as a reference for understanding the factors affecting soil variability, but also for the rational use of soil resources and the establishment of a virtuous cycle of forest ecosystems. The rapid development of remote sensing satellites provides an excellent opportunity to improve the accuracy of forest soil prediction models. This study aimed to explore the utility of the Gaofen-1 (GF-1) satellite in the forest soil mapping model in Luoding City, Yunfu City, Guangdong Province, Southeast China. We used 1000 m resolution coarse-resolution soil map to represent the overall regional soil nutrient status, 12.5 m resolution terrain-hydrology variables to reflect the detailed spatial distribution of soil nutrients, and 8 m resolution remote sensing variables to reflect the surface vegetation status to build terrain-hydrology artificial neural network (ANN) models and full variable ANNs, respectively. The prediction objects were alkali-hydro-nitrogen (AN), available phosphorus (AP), available potassium (AK), and organic matter (OM) at five soil depths (0–20, 20–40, 40–60, 60–80, and 80–100 cm). The results showed that the full-variable ANN accuracy at five soil depths was better than the terrain-hydrology ANNs, indicating that remote sensing variables reflecting vegetation status can improve the prediction of forest soil nutrients. The remote sensing variables had different effectiveness for different soil nutrients and different depths. In upper soil layers (0–20 and 20–40 cm), remote sensing variables were more useful for AN, AP, and OM, and were between 10%–14% (R2), and less effective for AK at only 8% and 6% (R2). In deep soil layers (40–60, 60–80, and 80–100 cm), the improvement of all soil nutrient models was not significant, between 3 and 6% (R2). RMSE and ROA ± 5% also decreased with the depth of soil. Remote sensing ANNs (coarse resolution soil maps + remote sensing variables) further demonstrated that the predictive power of remote sensing data decreases with soil depth. Compared to terrain-hydrological variables, remote sensing variables perform better at 0–20 cm, but the predictive power decreased rapidly with depth. In conclusion, the results of the study showed that the integration of remote sensing with coarse-resolution soil maps and terrain-hydrology variables could strongly improve upper forest soil (0–40 cm) nutrients prediction and NDVI, green band, and forest types were the best remote sensing predictors. In addition, the study area is rich in AN and OM, while AP and AK are scarce. Therefore, to improve forest health, attention should be paid to monitoring and managing AN, AP, AK, and OM levels.

Conservation tillage rotation enhanced soil structure and soil nutrients in long-term dryland agriculture

Conservation tillage has been proposed as an effective way to conserve soil water in dryland agriculture. However, long-term continuous mono-tillage including conservational and conventional tillage has been proved to have limited improvements or some defects on soil structure and nutrients enhancement. Combining different tillage practices in a rational rotation that adapts to the cropping system may optimize the advantages and improve the potentials of mono-tillage practices. Soil porosity, aggregates, water, organic carbon, nitrogen and crop yield were investigated in a ten-year (2007–2016) long-term conventional with conservation tillage rotation experiment which contained four tillage systems, NT (no-tillage), ST (subsoiling), CT (conventional tillage), and NCS rotation (no-tillage, conventional tillage and subsoiling rotated annually) in a dryland field to assess the soil pore system, aggregates, nutrients content and productivity. Compared with three mono-tillage systems (NT, ST and CT), the NCS rotation significantly decreased soil bulk density by 3.8–8.4 % and increased soil porosity by 3.2–6.7 % (P < 0.05) after ten years. NCS rotation increased soil capillary porosity by 9.7–36.3 %, reduced inactive porosity by 4–8.1 % when compared to continuous mono-tillage (NT, ST and CT), optimized soil porosity distribution at 0−60 cm soil depth till the tenth year. Meanwhile, compared with mono-tillage, NCS rotation improved soil macroaggregates content (0.25–5 mm) by 35.2–46.4 % and resulted in 40.3–113 % higher macroaggregates content than ten years before at 0−40 cm soil depth (P < 0.05). As the experiment continues, soil organic carbon (SOC) and nitrogen (TN) at different tillage systems accumulated at rates of 1.65−2.01 Mg ha−1 year−1 and 0.14−0.21 Mg ha−1 year−1, respectively, NCS rotation resulted in the highest soil nutrients accumulation (SOC: 57.98 Mg ha−1, TN: 6.40 Mg ha−1), better soil nutrients distribution and suitable C/N (9.01) for crop growth and soil enhancement. Additionally, NCS rotation conserved more soil water in fallow period (394 mm) and during crop growth season (winter wheat: 352 mm, spring maize: 384 mm), produced higher winter wheat (5169 kg ha−1) and spring maize yield (8251 kg ha−1). The long-term rotational research showed that NCS rotation optimized soil structure (soil porosity, soil aggregates) and enhanced soil nutrients (SOC, TN), provided better soil conditions for crop production in dryland rain-fed farming agriculture.

Roller dung beetles of dung piles suggest habitats are alike, but that of guarding pitfall traps suggest habitats are different

AbstractRoller dung beetles play a pivotal role in the nutrient distribution in soil and secondary dispersal of seeds. Dung beetles are sampled either using a dung-baited pitfall trap or an exposed dung pile on the ground. While the former method is useful for a rapid survey of dung beetles, information on the ecology and behaviour of dung beetles can be lost, which the latter method provides, but underestimates species diversity due to its inefficiency in trapping rollers. Efficiency of a new method for sampling rollers—installing guarding pitfall traps around dung piles—is assessed in three habitats—contiguous tropical rainforests, fragmented forests, and disturbed used home gardens—and two diel periods—day and night. Five guarding pitfall traps were installed at 50 cm radius around dung piles. About 98% of the total rollers were sampled in pitfall traps. The habitats were similar when the roller catches of only dung piles—conventional approach—were analyzed, but were different when the rollers of guarding pitfall traps were considered. The roller abundance was negatively affected by forest fragmentation and land-use change. About 98% of the rollers were collected at daytime. Using guarding pitfall traps around dung piles is highly recommended for dung beetle diversity studies.

Predicting soil nutrient contents using Landsat OLI satellite images in rain-fed agricultural lands, northwest of Iran

Soil nutrients are the key factors in soil fertility, which have important roles in plant growth. Determining soil nutrient contents, including macro and micronutrients, is of crucial importance in agricultural productions. Conventional laboratory techniques for determining soil nutrients are expensive and time-consuming. This research was aimed to develop linear regression (LR) models for remote sensing of total nitrogen (TN) (mg/kg), available phosphorous (AP) (mg/kg), available potassium (AK) (mg/kg), and micronutrients such as iron (Fe) (mg/kg), manganese (Mn) (mg/kg), zinc (Zn) (mg/kg), and copper (Cu) (mg/kg) extracted by DTPA in rain-fed agricultural lands in the northwest of Iran. First, 101 soil samples were collected from 0-30cm of these lands and analyzed for selected nutrient contents. Then a linear regression along with principal component analysis was conducted to correlate soil nutrient contents with reflectance data of different Landsat OLI bands. Finally, the spatial distributions of soil nutrients were drawn. The results showed that there were linear relationships between soil nutrient contents and standardized PC1 (ZPC1). The highest significant determination coefficient with an R2 value of 0.46 and the least relative error (%) value of 11.97% were observed between TN and ZPC1. The accuracy of the other LR's developed among other soil nutrient contents and remotely sensed data was relatively lower than that obtained for TN. According to the results obtained from this study, although remote sensing techniques may quickly assess soil nutrients, new techniques, technologies, and models may be needed to have a more accurate prediction of soil nutrients.