Soil Total Nitrogen Levels Research Articles

Construction of a hyperspectral estimation model for total nitrogen content in Shajiang black soil

AbstractBackgroundThe real‐time non‐destructive estimation of soil total nitrogen content via hyperspectral remote sensing is important for crop fertilization and precision agriculture development.AimsThe study aimed to use hyperspectral technology for the construction of an estimation model using different methods for assessing total nitrogen content in Shajiang black soil.MethodsIn our study, soil samples were obtained from Shangshui County, Henan Province, China. Using hyperspectral data of soil samples, the original spectral reflectance was transformed into logarithmic, reciprocal, and first derivative spectra. Hyperspectral estimation models for assessing the total nitrogen content were built with spectral indices, competitive adaptive reweighted sampling (CARS) algorithms, and a combination of machine learning methods, including the partial least square regression, support vector machine (SVM), and random forest methods.ResultsThe results showed that after the first derivative transformation, the performance of normalized indices constructed with a combination of two bands at 1401 and 776 nm was better. The coefficient of determination (R2), root mean square error (RMSE), ratio of performance to deviation (RPD), and ratio of performance to the inter‐quartile range (RPIQ) values of the model were 0.84, 0.10 g kg–1, 2.25, and 4.04, respectively. Validation was performed using data independent of the modeling samples, and validation R2, RMSE, RPD, and RPIQ values were 0.92, 0.07 g kg–1, 2.56, and 4.19, respectively. The same sample was analyzed using a CARS algorithm for screening feature bands, and the 61 reciprocal reflectance bands selected as the input for the SVM exhibited the best performance. A modeling R2 value of 0.92, RMSE of 0.07 g kg–1, RPD of 3.09, RPIQ of 5.97, and validation R2 of 0.96, RMSE of 0.06 g kg–1, RPD of 3.24, and RPIQ of 8.47 were observed.ConclusionsThe estimation models constructed using the two methods exhibited good ability to determine the total nitrogen content. The accuracy of the SVM model was slightly higher than that of the indices model, but both models could facilitate the rapid estimation of total nitrogen content in Shajiang black soil. The findings can provide a technical reference for the estimation of the levels of soil total nitrogen and other nutrients.

Optimization of Reclamation Measures in a Mining Area by Analysis of Variations in Soil Nutrient Grades under Different Types of Land Usage—A Case Study of Pingshuo Coal Mine, China

The development of reclaimed mine soils is normally spatially heterogeneous, making the fine management and utilization of reclaimed mined lands difficult. Soil nutrient grading can provide a scientific basis for the precise regulation of soil nutrients, but few related studies are available in reclaimed mined areas. This study aimed to quantify the spatiotemporal variations in soil nutrient grades under different land-use types in a reclaimed mined area on the Loess Plateau, China. The study area was graded by four soil nutrients (soil available potassium (SAK), soil available phosphorus (SAP), soil total nitrogen (STN), and soil organic matter (SOM)), and the variation features of soil nutrient grades in the initial stage of reclamation under four land-use types (i.e., cultivated land, grassland, forestland, and barren land) were systematically characterized by geostatistical analysis, pedodiversity analysis, and correspondence analysis. The results show that during the initial five years after reclamation, the soil nutrient grades of most reclaimed areas increased from Grade V and VI to Grade I–IV, while the improvements were significantly heterogeneous. Notably, the four land-use types had distinct variation characteristics. The barren land had the lowest SAP level, whereas it had the highest proportion, and medium–high grades of SAK, STN, and SOM (88.3, 100.0, and 100.0%, respectively). In terms of quantitative structure, it had the lowest richness index (S′, 2.5) and Shannon’s entropy index (H′, 0.7) and the highest evenness index (E′, 0.8). These results suggest that the barren land had relatively high and balanced nutrients, with the highest homogeneity among the four land-use types. The grassland had considerable improvement in all nutrients (especially SAP; 95.6% of the area had high SAP grades); however, its improvement was the most heterogeneous (S′ = 4.5, E′ = 0.7). As the second-most heterogeneous land-use type (S′ = 4.0, E′ = 0.8), the forestland had relatively low STN, SAP, and SAK levels due to high nutrient uptake and storage by tree species, but it had the highest proportion of area that reached high SOM grades (36.4%) and medium to high SOM grades (100.0%) due to its high community productivity. The cultivated land, which received fertilization for an additional three years, was the most imbalanced in terms of nutrients. It had the highest proportion of area that reached high SAP grades (98.0%); in contrast, its area proportions of low-grade SAK and SOM (69.0 and 32.9%, respectively) were the highest among the four land-use types. Based on the above comprehensive characterization of soil nutrient grade variation, guidance was given for fine management of reclaimed mined land and the optimization of reclamation measures.

Effects of landscape complexity and local management on bee pollinator diversity in apple orchards in Changping District, Beijing, China.

Pollinators provide important ecosystem services for crop production and food security. With the development of agricultural economy and the increasing intensity of land-use, a large number of natural or semi-natural habitats have been converted to croplands. Landscape homogenization and intensive management lead to the decline of wild bee diversity and threaten the sustainable agricultural production. In this study, we investigated the effects of landscape complexity (proportion of semi-natural habitats), local management practices (local flowering plant diversity and soil total nitrogen), and their interactions on diversity of bee pollinators in apple orchard in Changping District, Beijing. A total of 8642 bee individuals were captured, including 5125 honey bees and 3517 wild bees from 5 families, 14 genera, and 49 species. The optimal landscape scale for the response of bee diversity to landscape complexity and local management intensity was 500 m. Within 500 m radius of the site, the abundance of overall bees and wild bees significantly increased with increasing proportion of semi-natural habitats. The landscape complexity interacting with local flowering plant diversity significantly affected the richness of overall bee and wild bee. When the proportion of semi-natural habitats surrounding the apple orchards was low (≤29.9%), we found a positive effect of flowering plant diversity on the richness of overall bee and wild bee, whereas a reversed trend was found when the proportion of semi-natural habitats surrounding the apple orchards was high (>29.9%). In addition, the abundance of honey bees significantly increased with the increase of local flowering plant diversity and soil total nitrogen. The soil total nitrogen interacting with local flowering plant diversity significantly affected the honey bee abundance. At low levels of soil total nitrogen (≤1.9 g·kg-1), there was a positive effect of flowering plant diversity on honey bee abundance; whereas this trend was reversed at high levels of soil total nitrogen (>1.9 g·kg-1). Increasing the proportion of semi-natural habitats in agricultural landscape was beneficial to the increase of wild bee abundance, and flowering plant diversity could promote bee diversity but depending on landscape scale (proportion of semi-natural habitats) and local scale (nitrogen application). Therefore, multi-scale factors should be considered to develop conservation strategies to maintain the diversity of wild bees in agricultural landscape. Maintaining a higher proportion of cultivated land as much as possible is still a long-term requirement for production, while maintaining intermediate landscape complexity, increasing the diversity of flowering plants on the ground, and reducing the application of nitrogen fertilizer would be effective ways to promote the diversity of pollinating bees in apple orchards.

Effects of fire on soil organic carbon, soil total nitrogen, and soil properties under rotational shifting cultivation in northern Thailand

Fire has been used for land clearing under rotational shifting cultivation (RSC) in Northern Thailand for a long time. However, the effects of fire on soil organic carbon (SOC), soil total nitrogen (STN), and soil properties are not well understood. We determined SOC, STN, and soil properties of the topsoil layer (0–30 cm) along a fallow chronosequence under RSC and assessed how fire affects SOC, STN, and soil properties. Eight fields at Ban Mae Pok, Mae Chaem District, Chiang Mai Province, Northern Thailand, were investigated. The levels of SOC, STN, and soil properties were observed at three time points: pre-burning, post-burning (5 minutes after burning), and post-harvest (nine months after burning). The highest SOC and STN stocks, organic matter (OM), and clay content were observed for the longest fallow period (7 years fallow), whereas the shortest period (1 year fallow) resulted in the lowest SOC and STN stocks. Fire caused no significant changes in SOC, STN, and some soil properties (soil texture, available P, exchangeable K, exchangeable Ca, exchangeable Mg, bulk density, and OM) because of the low fire intensity and short fire duration. Only pH and electrical conductivity were significantly increased (p ≤ 0.05) after burning due to the demobilization of base cations in burnt vegetation and incorporation into the soil with ashes and wood charcoal. Although fire may still be necessary for RSC, maintaining the fire intensity below 380 °C to reduce SOC losses and appropriate post-fire management strategies to reduce STN losses are crucial.

Changes in soil carbon and nitrogen stocks following degradation of alpine grasslands on the Qinghai‐Tibetan Plateau: A meta‐analysis

AbstractUntil now, nearly 90% of alpine grasslands on the Qinghai‐Tibetan Plateau (QTP) have been degraded. However, there is currently no consensus on how soil organic carbon (SOC) and soil total nitrogen (STN) stocks vary with the degradation succession of alpine grasslands in this region. Here, a meta‐analysis was conducted to quantify the dynamics of SOC and STN stocks in topsoil (0–30 cm) at different degradation stages of alpine grasslands on the QTP. The results showed that grassland degradation led to average losses of 48 and 39% for SOC and STN stocks, respectively. The changes in SOC and STN stocks following grassland degradation did not differ significantly between grassland types, but were significantly affected by grassland degradation stage. The reductions in both SOC and STN stocks increased with the degradation stage, and the highest reductions were all found at extreme degradation stage. The results indicated that the depletion of SOC and STN pools were aggravated with the degradation succession of grassland. The tightly coupled SOC and STN implied that the depletion of SOC stock was closely related to that of STN stock during the process of grassland degradation. Positive relationships were detected between the dynamics of vegetation coverage and that of SOC or STN stock, indicating that vegetation coverage could not only reflect grassland degradation, but might also be a potential indicator of SOC and STN status. The findings suggest that preventing the degradation succession of alpine grasslands is vital to maintain or promote SOC and STN levels on the QTP.

Organic carbon and total nitrogen dynamics of reclaimed soils following intensive agricultural use in eastern China

In past decades, coastal tidal flats in China have experienced rapid and extensive agricultural reclamation due to the increasing pressure of population growth. With more coastal land likely reclaimed in the future, an increase in the understanding of the effects of the reclamation history and changes in land use on soil properties is essential. In this study, a total of 746 surface soil/sediment samples were collected from three study areas with different reclamation durations and land use patterns on the coasts of Dafeng, Rudong and Cixi in eastern China, covering a total area of 1926km2. The results showed that mean soil organic carbon (SOC) and soil total nitrogen (STN) in the three study areas differed slightly and ranged from 7.24 to 7.69gkg−1 and from 0.71 to 0.76gkg−1, respectively. SOC and STN increased significantly with an increase in reclamation duration in all of the study areas, except for the early stage of land conversion in Cixi and the late stage of conversion in Dafeng, which highlighted that the accumulation of SOC and STN was positively correlated with reclamation duration. In Dafeng and Rudong, land dominated by human uses had much higher levels of SOC and STN than those in the tidal flats. For the same duration of reclamation, paddy land had higher levels of SOC and STN than those in the upland, with the exception of the 10-year-old land in Cixi. Our results also indicated that reclaimed coastal soils can sequester considerable amount of OC through improved land management. The differences in the sequestration potential for OC and the dynamics of SOC and STN among the three chronosequences were attributed to specific land use patterns in each study area.

Vegetation response to logging residue removals in Great Lakes aspen forests: Long-term trends under operational management

Conservation of vegetation diversity has been integrated into forest management regimes as stands with high levels of diversity have been shown to possess enhanced ecological services and resilience to disturbance. Effects of intensified forest management and harvesting practices such as logging residue removals for bioenergy on vegetation diversity and community dynamics has been largely overlooked, however. We examined forest vegetation communities under residue removal treatments along a unique 40-yr chronosequence of commercial aspen (Populus spp.) in Upper Michigan to examine potential impacts on species abundance metrics, community structure, and heterogeneity. We hypothesized that residue removals would negatively impact species diversity of both the over- and understory communities, and that these patterns would occur in parallel with shifts in community structure of both strata. Our results show no effect of residue treatment on overstory tree communities; however we did observe an increase in understory species richness, diversity, and evenness in stands where residues were harvested. The understory community structure was correlated with soil total nitrogen levels, yet this pattern was independent of harvest residue treatment. In addition, we observed higher levels of variance in species representation of the understory community when residues were removed, but did not detect any difference in community organization. Overall, our results suggest that the removal of harvest residues can increase variability in vegetation community relationships. We believe that these patterns can be attributed to increased site disturbance and soil scarification through additional equipment trafficking and subsequent changes in micro environmental conditions when residues are harvested.

Assessment of nitrogen and phosphorus loads present in environments impacted by alternative poultry processing operations utilized in pasture-raised poultry production

AbstractPasture-raised poultry (PP) production systems allow chickens, turkeys or other poultry types to be raised entirely on pasture or in small, open-air moveable pens with access to fresh pasture daily. With an increase in consumer demand for poultry products produced using more humane and potentially environmentally sustainable practices, PP production systems are regaining popularity among farmers across the USA. The majority of research on PP is related to meat quality and forage conditions while the environmental effects have remained largely unstudied. The rotation of poultry on pasture is one of the primary best management practices (BMP) used to avoid over grazing and buildup of excess nutrients and pathogens; however, BMPs for handling and processing of the associated wastes (i.e., wastewater, feathers, offal) related to on-farm processing and mobile poultry processing units (MPPU) are not as well established. Therefore, a study with PP growers in the southern USA was initiated to provide important baseline information on the potential environmental impacts of processing methods used by PP production systems. Here, three farms utilizing on-farm processing were sampled over a 9-month period and two farms utilizing a MPPU pilot plant were sampled over a 3-month period. Soil, compost and wastewater samples were collected during each sampling date for on-farm processing while only wastewater was collected at the MPPU pilot plant. Soil samples (24-cm cores) were analyzed for total nitrogen (TN), Mehlich-3 extractable phosphorus (M3-P) and moisture content. Compost derived from processing wastes was analyzed for TN, total phosphorus (TP), water extractable P and moisture content. Wastewaters were analyzed for total Kjeldahl nitrogen (TKN) and TP. Soil TN levels (0.075–0.30%) reported here are comparable with TN levels reported for various soils in the Southeastern USA while M3-P was generally below levels found in agricultural soils subject to conventional poultry litter application based on previously published data. Conversely, TN and TP levels—0.3 to 1.3 and <0.4%, respectively—in compost were well below recommended values (i.e., approximately 2% each of N and P) for compost highlighting an opportunity for PP growers to create a more useful compost for land application. Last, wastewater collected from both, on-farm processing and the MPPU measure TKN and TP levels were much less than conventional processing. Overall, the present study provided baseline data on soil and compost nutrients related to on-farm poultry processing as well as wastewater composition for on-farm processing and MPPUs.

An Integrated Quantitative Method to Simultaneously Monitor Soil Erosion and Non-Point Source Pollution in an Intensive Agricultural Area

In China, some areas with intensive agricultural use are facing serious environmental problems caused by non-point source pollution (NPSP) as a consequence of soil erosion (SE). Until now, simultaneous monitoring of NPSP and SE is difficult due to the intertwined effects of crop type, topography and management in these areas. In this study, we developed a new integrated method to simultaneously monitor SE and NPSP in an intensive agricultural area (about 6 000 km2) of Nanjing in eastern China, based on meteorological data, a geographic information system database and soil and water samples, and identified the main factors contributing to NPSP and SE by calculating the NPSP and SE loads in different sub-areas. The levels of soil total nitrogen (TN), total phosphorus (TP), available nitrogen (AN) and available phosphorus (AP) could be used to assess and predict the extent of NPSP and SE status in the study area. The most SE and NPSP loads occurred between April to August. The most seriously affected area in terms of SE and NPSP was the Jiangning District, implying that the effective management of SE and NPSP in this area should be considered as a priority. The sub-regions with higher vegetation coverage contributed to less SE and NPSP, confirming the conclusions of previous studies, namely that vegetation is an effective factor controlling SE and NPSP. Our quantitative method has both high precision and reliability for the simultaneous monitoring of SE and NPSP occurring in intensive agricultural areas.

Total nitrogen and total phosphorous in urban soils used for different purposes in Beijing, China

The concentration and spatial distribution of total nitrogen (TN) and total phosphorus (TP), as well as variations in their levels, in land used for various activities were investigated, and the Kriging interpolation method was applied to describe the spatial distribution of TN and TP in urban soils in Beijing, China. The concentration of soil TP was higher in the middle of the city and lower in the outsides of the city. However, the levels of soil TN had no definite spatial distribution pattern. The contents of TN and TP were compared in land used for different purposes, and the spatial distribution of TN and TP, as well as the impact of human activities on TN and TP contents, in urban soils were also analyzed. Our results demonstrated that the TN levels depend on the coverage of natural vegetation at each type of site, and the TP content is affected by the usage and disposal of phosphorus-containing materials at each type of site.

Temporal-spatial variability and fractal characteristics of soil nitrogen and phosphorus in Xinji District, Hebei Province, China

Traditional statistics, geostatistics, fractal dimensions, and geographic information systems (GIS) were employed to study the temporal-spatial variability of soil total nitrogen (TN) and total phosphorus (TP) levels in Xinji District, Hebei Province area of the North China Plain from 1980 to 2007. The results indicate that nutrient levels follow normal or lognormal distributions. The TN content was 0.59 ± 0.155 g kg( -1) in 2007, an increase of 0.44 g kg( -1) compared with that of 1980. In 2007, the TP content was 1.21 ± 0.227 g kg( -1), an increase of 0.01 g kg( -1) from 1980. The geostatistical analysis showed that the distribution of these soil nutrients in the study area exhibits a trend and anisotropy. The range and [C (0)/(C (0) +C)] of TN and TP in 1980 were all less than in 2007. The ordinary kriging interpolation method was used to analyze the nutrient contents differences between 1980 and 2007. The results indicate that soil TN levels have increased over the 27-year period, and the area where the TN level had increased by at least 0.4 g kg( -1) was about 61.7% of the district. The area where the TP content increased covered about 58.4% of the district. The variance analysis indicated that land-use type had a clear influence on the distribution and change in TN and TP content. Using the 3-D box-counting dimension method combined with GIS, the fractal dimension of soil nutrient spatial distribution over the two periods showed that in 27 years, the fractal dimension of TN increased from 1.95 to 2.02, and the fractal dimension of TP increased from 1.89 to 2.01, indicating that the complexity of the spatial distribution of all nutrient contents had increased. This study can provide a basis for accurate fertilizing and to enhance the conversion of soil characteristics under different spatial scales.

The effect of increased soil nitrogen associated with medic ley on the performance of a standard and a semi-dwarf wheat cultivar

Two cropping rotations of fallow-wheat and four years of barrel medic (Medicago truncatula) pasture were used to obtain two levels of soil total nitrogen on a grey clay at Longerenong College, Dooen, Victoria. A semi-dwarf cultivar, Mexico 120, and a standard cultivar, Olympic, were then compared at the two levels of soil nitrogen over four years from 1964 to 1967. Mexico 120 outyielded Olympic by 1490 kg ha-1 in 1964 at the higher soil nitrogen level; however, it did not yield any better than Olympic at low soil nitrogen in that year nor at either soil nitrogen level in the other years. Mexico 120 had higher tiller survival, larger grain size, and shorter straw than Olympic in all years. In 1965 and 1966 its harvest index and the percentage of plant nitrogen in the grain responded more to higher soil nitrogen than that of Olympic.