Soil Nutrient Loss Research Articles

Comparative analysis of soil nutrients under different land-use types in the Mun River basin of Northeast Thailand

Land-use/cover management is one of the driven forces to induce soil erosion. Meanwhile, the loss of soil nutrients caused by soil erosion severely restricts soil fertility. However, the differences in soil nutrients under different land-use types in an erodible environment are complex and the factors are still unclear in tropical river basin. In the Mun River basin of Northeast Thailand, a total of six soil profiles were selected from the native forest, artificial forest, paddy land, and abandoned paddy lands with 1, 3, and 5-year abandoned history, respectively. The contents of soil nutrients, including soil organic carbon (SOC), soil organic nitrogen (SON), and inorganic minerals (Al2O3, CaO, Fe2O3, K2O, MgO, and MnO), in the soil profiles were analyzed to determine their distribution under different land-use types. Soil erodibility K factor was calculated by the erosion productivity impact calculator (EPIC) model to estimate the potential of soil erosion under different land-use types. Moreover, the relationships between soil nutrients and the K factor were determined by linear regression analysis and Spearman’s rank correlation analysis. The silty soils under artificial forest were significantly larger for the contents of SOC, SON, Al2O3, Fe2O3, and MnO than the sandy soils under native forest, which was mainly attributed to the abundant fine particles in the silty soils. Fine particles played a key role in being the main carriers of inorganic minerals and combining with organic matter. The contents of SOC, SON, and all inorganic minerals in the soils of the abandoned paddy lands were significantly lower than those in the paddy field, resulting from the severe loss of fine particles under intense soil erosion. The soils with abundant fine particles under the native forest land and paddy land had significantly higher K factors compared to the coarse-textured soils under other land-use types. The K factor was mainly controlled by the proportion of fine particles in the Mun River basin. The paddy field easily occurred severe soil erosion at the early stage (1 year) of paddy land abandonment due to the lack of protective management, which caused decreasing SOC, SON, and inorganic minerals with the loss of fine particles. However, the K2O, MgO, and CaO contents significantly increased after 3 ~ 5 years of paddy land abandonment through the supplement from high salinity groundwater. These results suggest that continual paddy cultivation can effectively maintain soil nutrients in the sandy soils of the tropical river basin.

Vineyards Assessed Under a Biophysical Approach: Findings From the Biohydrology and TERRAenVISION Meetings

During the Biohydrology 2019 (24-27 July 2019, Valencia, Spain) and TERRAenVISION 2019 (2-7 September 2019, Barcelona, Spain) meetings, the scientific sessions joined reputed scientists around the world. Innovative debates during these scientific sessions about vineyards focused on the use of new technologies to assess soil erosion and nutrient losses, benefits or damages generated by tillage, the use of cover crops, and the introduction of organic farming. Among all the high-quality posters and oral presentations in these 2 abovementioned conferences, 3 groups from different countries with an extended list of publications decided to publish their new findings on the special issue: Vineyards Assessed Under a Biophysical Approach.

The benefits of the no-till system on soil health and crop yields in dryland cropping systems

Context The no-till (NT) system is used to control soil erosion and nutrient losses, but extensive evaluation of NT on soil health and long-term crop yields compared to conventional till (CT) is needed to evaluate the overall benefit of NT. Aims The objective of this study was to compare NT and CT on soil health and long-term crop yields in two dryland farming sites in the northern Great Plains, USA. Methods Soil samples collected from two long-term (14- and 36-years-old) experiments of dryland farming under NT and CT continuous spring wheat (Triticum aestivum L.) and barley (Hordeum vulgaris L.)/spring wheat-fallow rotation were analysed for 66 soil physical, chemical, biological and biochemical properties and crop yields determined. Key results NT increased wet soil stability index, average slake aggregate and total shrinkage by 12–61%, but reduced saturated hydraulic conductivity by 24–31% compared to CT. Soil Al, Ba, Cu and S concentrations were 10–16% greater, but electrical conductivity, Co, Na and Zn concentrations, and Na-absorption ratio were 9–33% lower with NT than CT. Similarly, NH4-N concentration, CO2 evolution, phospholipid-derived fatty acid (PLFA), phosphomonoesterase and arysulfatase were 13–38% greater, but water extractable N, NO3-N concentration and potential N mineralisation were 16–31% lower with NT than CT. Mean crop yield across years were similar between NT than CT. Conclusions NT can enhance overall soil health and sustain dryland crop yields compared to CT in the northern Great Plains, USA. Implications Long-term sustainability of dryland cropping system can be maintained by using the NT system.

Agronomic and environmental performance of biochar amendment in alluvial soils under subtropical sugarcane production

AbstractThis study investigated the amendment of sugarcane bagasse biochar (SCBB) on soil fertility, crop yield, and nutrient loss in two different‐textured soils under sugarcane (Saccharum spp.) production. Eleven megagrams per hectare of freshly incorporated biochar increased yield of plant cane by 22% in light‐texture soil (LS) and 12% in heavy‐textured soil (HS). Although the overall yield of the ratoon crop was lower, the biochar treatment produced 20 and 14% higher yields than the control at the LS and HS sites, respectively. Biochar increased soil carbon (Csoil) across LS and HS sites by 15% and decreased the soil C/N ratio by 19%. Over the two growing seasons and sites, cumulative runoff volume, and loads of NO3––N, PO4–3–P, biological oxygen demand (BOD5), total organic C (TOC), and total suspended solids (TSS) were reduced by 33, 35, 39, 25, 24, and 54% with biochar. Calcium and K losses in runoff were also reduced by 43 and 24% with biochar. It reduced NH4+–N leaching in LS and HS soils over the two growing seasons by 33–167% and 66–81%, respectively, and reduced PO4–3–P leaching by 45–57% in HS over 2 yr. Although biochar is not considered a fertilizer, SCBB acted as a source of nutrients, increasing soil fertility and crop yield. It also reduced nutrient losses during heavy rain events typical of the subtropical climate of Louisiana.

Sugarcane planting patterns control ephemeral gully erosion and associated nutrient losses: Evidence from hillslope observation

Globally, the hillslope currently supporting sugarcane production is accelerating soil erosion and nutrient losses that degrade agroecosystem services and increase water pollution. However, sugarcane planting patterns (SPP), involving the arrangement of perennial (P) and newly planted (NP) sugarcane along hillslopes, may influence hillslope erosion and nutrient losses due to changes in root density and litter cover. Yet, no study to date has investigated the contribution of SPP to rill/and ephemeral gully (EG) erosion and associated nutrient losses. Thus, we investigated changes in EG erosion and losses of total nitrogen (TN), phosphorus (TP) and soil organic carbon (SOC) in response to SPP and the underlying mechanisms on hillslopes. Five hillslopes with different SPPs (P–P–P, NP–P–P, P–NP–P, NP–NP–P and P–NP) were identified in a sugarcane growing watershed. Annual EG erosion rates ranged from 56.6–96.1 Mg ha−1 yr−1 in the order of P–P–P < P–NP–P < P–NP < NP–P–P < NP–NP–P. The average EG erosion and associated TN, TP and SOC losses from the newly planted sugarcane fields were 2–3-fold of the perennial fields. The average annual yield of newly planted sugarcane was 10 % higher than the perennial sugarcane, but the increased yield benefit was dwarfed by significant increase in EG erosion and nutrient losses. Simple regression analyses indicated that EG erosion was inversely correlated with sugarcane litter cover and fine root density (root diam. < 1 and 1–2 mm), but positively correlated with slope-length factor. The principal component regression (PCR) showed that fine root density, litter cover, and slope-length were the main predictors for EG erosion. The results of this study revealed that appropriate SPP that replaces perennial sugarcane, at ≤30 % on different slope positions, with newly planted sugarcane, could minimize rill and EG erosion and nutrient losses as well as maintaining the annual yield.

Influence of rye cover cropping on denitrification potential and year-round field N2O emissions

Cover cropping is beneficial for reducing soil erosion and nutrient losses, but there are conflicting reports on how cover cropping affects emissions of nitrous oxide (N2O), a potent greenhouse gas. In this study, we measured N2O fluxes over a full year in Illinois corn plots with and without rye cover crop. We compared these year-round measurements to N2O emissions predicted by the Intergovernmental Panel on Climate Change (IPCC) Tier 1 equation and the Denitrification-Decomposition (DNDC) model. In addition, we measured potential denitrification and N2O production rates. The field measurements showed typical N2O peaks shortly after fertilizer application, as well as a significant late-winter peak. Cover cropping significantly reduced all peak N2O fluxes, with decreases ranging from 39 to 95%. Neither model was able to accurately predict annual N2O fluxes or the decrease in N2O emissions from cover-cropped fields. In contrast to field measurements, lab assays found that cover cropping significantly increased potential denitrification by 90–127% and potential N2O production by 54–106%. The rye cover-cropped plots had lower soil nitrate and higher soil carbon. When limiting nitrate and excess carbon were provided in lab assays, the proportion of N2O resulting from denitrification decreased. These results suggest that the discrepancy between the observed decrease in field N2O emissions and the increase in denitrification potential may be due to the difference in available nutrients between the field and laboratory measurements. Overall, these results suggest the importance of late-winter peaks in N2O emissions and the potential of rye cover cropping to reduce N2O emissions from agricultural fields.

Assessing spatial variability of soil organic carbon and total nitrogen in eroded hilly region of subtropical China.

The hilly red soil region of southern China suffers from severe soil erosion that has led to soil degradation and loss of soil nutrients. Estimating the content and spatial variability of soil organic carbon (SOC) and soil total nitrogen (STN) and assessing the influence of topography and land-use type on SOC and STN after years of soil erosion control are important for vegetation restoration and ecological reconstruction. A total of 375 topsoil samples were collected from Changting County, and their SOC and STN distributions were studied by using descriptive statistics and geostatistical methods. Elevation, slope, aspect and land-use type were selected to investigate the impacts of natural and human factors on the spatial heterogeneity of SOC and STN. The mean SOC and STN concentrations were 15.85 and 0.98 g kg-1 with moderate spatial variations, respectively. SOC and STN exhibited relatively uniform distributions that decreased gradually from the outside parts to the center of the study area. The SOC and STN contents in the study area were still at moderate and low levels after years of erosion control, which suggests that soil nutrient improvement is a slow process. The lowest SOC and STN values were at lower elevations in the center of Changting County. The results indicated that the SOC and STN contents increased most significantly with elevation and slope due to the influence of topography on the regional natural environment and soil erosion in the eroded hilly region. No significant variations were observed among different slope directions and land-use types.

Direct and indirect effects of rainfall and vegetation coverage on runoff, soil loss, and nutrient loss in a semi‐humid climate

AbstractSoil and nutrient loss play a vital role in eutrophication of water bodies. Several simulated rainfall experiments have been conducted to investigate the effects of a single controlling factor on soil and nutrient loss. However, the role of precipitation and vegetation coverage in quantifying soil and nutrient loss is still unclear. We monitored runoff, soil loss, and soil nutrient loss under natural rainfall conditions from 2004 to 2015 for 50–100 m2 runoff plots around Beijing. Results showed that soil erosion was significantly reduced when vegetation coverage reached 20% and 60%. At levels below 30%, nutrient loss did not differ among different vegetation cover levels. Minimum soil N and P losses were observed at cover levels above 60%. Irrespective of the management measure, soil nutrient losses were higher at high‐intensity rainfall (Imax30&gt;15 mm/h) events compared to low‐intensity events (p &lt; 0.05). We applied structural equation modelling (SEM) to systematically analyze the relative effects of rainfall characteristics and environmental factors on runoff, soil loss, and soil nutrient loss. At high‐intensity rainfall events, neither vegetation cover nor antecedent soil moisture content (ASMC) affected runoff and soil loss. After log‐transformation, soil nutrient loss was significantly linearly correlated with runoff and soil loss (p &lt; 0.01). In addition, we identified the direct and indirect relationships among the influencing factors of soil nutrient loss on runoff plots and constructed a structural diagram of these relationships. The factors positively impacting soil nutrient loss were runoff (44%–48%), maximum rainfall intensity over a 30‐min period (18%–29%), rainfall depth (20%–27%), and soil loss (10%–14%). Studying the effects of rainfall and vegetation coverage factors on runoff, soil loss, and nutrient loss can improve our understanding of the underlying mechanism of slope non‐point source pollution.

Quantifying the Effects of Vegetation Restorations on the Soil Erosion Export and Nutrient Loss on the Loess Plateau.

The transport of eroded soil to rivers changes the nutrient cycles of river ecosystems and has significant impacts on the regional eco-environment and human health. The Loess Plateau, a leading vegetation restoration region in China and the world, has experienced severe soil erosion and nutrient loss, however, the extent to which vegetation restoration prevents soil erosion export (to rivers) and it caused nutrient loss is unknown. To evaluate the effects of the first stage of the Grain for Green Project (GFGP) on the Loess Plateau (started in 1999 and ended in 2013), we analyzed the vegetation change trends and quantified the effects of GFGP on soil erosion export (to rivers) and it caused nutrient loss by considering soil erosion processes. The results were as follows: (1) in the first half of study period (from 1982 to 1998), the vegetation cover changed little, but after the implementation of the first stage of the GFGP (from 1999 to 2013), the vegetation cover of 75.0% of the study area showed a significant increase; (2) The proportion of eroded areas decreased from 41.8 to 26.7% as a result of the GFGP, and the erosion intensity lessened in most regions; the implementation significantly reduce the soil nutrient loss; (3) at the county level, soil erosion export could be avoided significantly by the increasing of vegetation greenness in the study area (R = −0.49). These results illustrate the relationships among changes in vegetation cover, soil erosion and nutrient export, which could provide a reference for local government for making ecology-relative policies.

The dynamics in rhizosphere microbial communities under bacterial wilt resistance by mulberry genotypes.

The contribution of crops and soil microbial community structure and functional diversity in soil-borne diseases control mulberry plant production is still inadequately understood. In this work, a comparative study was undertaken on the microbial abundance, community structure, and functional diversity in the soil rhizosphere between the resistant (Kangqing 10) and the susceptible (Guisang 12) mulberry genotypes. The study deployed the use of dilution plate method, micro-ecology technology, and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) techniques. The study aimed at developing better crop management methods for mulberry cultivation as well as preventing and controlling the occurrence and impacts of bacterial wilt on mulberry productivity. The results indicated that the soil rhizosphere microorganisms were more abundant in the normal resistant mulberry genotype than in the normal susceptible mulberry genotype. Carbon source utilization was better in the normal susceptible mulberry genotype. These properties were lower in the sickly resistant mulberry genotype than in the susceptible sickly mulberry genotype. Through the PCR-DGGE, it was shown that the bacterial and fungal community structures of the resistant genotypes were more stable than those of the susceptible genotypes. Through correlation regression analysis, it was shown that the mulberry bacterial wilt significantly contributes to the loss of soil nutrients, particularly organic matter and nitrogen, a possible cause to disrupted balance between the soil microbial community and the loss of soil organic matter. Resistant genotype plants displayed more resistance to bacterial wilt. Therefore, this study recommends the need to promote the cultivation of resistant genotype mulberry for increased yield.

Application of Organic Fertilizer Based on Marine Organism in Rice Planting

Yu, X.; Fan, X., and Zhang, B., 2020. Application of organic fertilizer based on marine organism in rice planting. In: Li, L. and Huang, X. (eds.), Sustainable Development in Coastal Regions: A Perspective of Environment, Economy, and Technology. Journal of Coastal Research, Special Issue No. 112, pp. 326-328. Coconut Creek (Florida), ISSN 0749-0208.The traditional way of rice fertilization in China is easy to lead to the loss of soil and water nutrients in rice fields, which leads to the decrease of fertilization efficiency and the pollution of surrounding water bodies. Based on this, this paper first designed the experiment of the influence of the organic fertilizer of the marine organism on the rice, then studied the influence of the organic fertilizer of the marine organism on the rice growth form, finally analyzed the influence of the organic fertilizer of the marine organism on the rice physiological index, thus verified the application value of the organic fertilizer of the marine organism on the rice.

Soil wind erosion evaluation and sustainable management of typical steppe in Inner Mongolia, China

Soil wind erosion is an important ecological environmental problem that is widespread in arid and semi-arid regions. Currently, related studies are mainly focused on spatiotemporal characteristics or analysis of effector mechanisms, and they do not facilitate direct servicing of management decisions. In this paper, we used the Xilingol typical steppe in Inner Mongolia, China, as a study site to develop a decision framework for a comprehensive understanding of soil wind erosion and to promote sustainable management of steppes. In this study, we used the Revised Wind Erosion Equation model to simulate soil wind erosion. We combined this model with linear trend analysis to evaluate the ecological effects of soil wind erosion and wind erosion intensity, and delineated the gravity center migration path. We used the constraint line method to reveal the mechanisms by which climatic factors affected soil wind erosion, achieved the spatial visualization of wind-breaking and sand-fixing service flow, and proposed decision-based regional sustainable development suggestions. The results showed that long-term soil wind erosion will lead to soil coarsening and loss of soil nutrients. Soil wind erosion in the study site showed worsening trends and risks, and as such, ecological environment conservation and management are urgently required. The study framework promotes a clear understanding of the complex relationship of human–earth systems. The study results will aid in the ecological remediation of steppe landscapes and the prevention of desertification and will provide a foundation for win–win management of ecological conservation and economic development in arid and semi-arid regions.

Driving force of soil microbial community structure in a burned area of Daxing\u2019anling, China

Fires are an important factor impacting forest ecosystems of Daxing’anling and have a significant effect on soil microbial community structure. In this study, high-throughput sequencing for 16S rDNA and ITS rDNA were applied to analyze the changing characteristics and driving factors of bacterial and fungal community structures in burned areas with different fire severity. PICRUSt2 software was used to predict the functional characteristics of burned areas with different fire severity. The purpose was to unveil the responsive relationships among the structure and function of bacterial and fungal communities, fire severity, and post-disturbance restoration times. After high severity fires, the destruction of surface vegetation and loss of soil nutrients reduced the diversity and abundance of soil bacteria and fungi. The soil bacteria community structure, which was dominated by Acidobacteria, Proteobacteria, and Actinobacteria, changed to be dominated by Proteobacteria and Chloroflexi. As well, soil fungal community changed from domination by Helotiales, Eurotiales and Russulales to domination by Archaeorhizomycetales and Helotiales. Over time, soil bacterial community was gradually restored to pre-fire levels 30 years after the fire. Soil fungal community changed and failed to restore to pre-fire levels after 30 years. After low/intermediate severity fires, environmental factors were relatively unchanged so that soil bacteria diversity and abundance increased, optimizing community composition. The diversity and abundance of soil fungi decreased and the community structure changed slightly. Over time, both bacterial and fungal communities were gradually restored to pre-fire levels 30 years after the fire. After fire disturbance, with increasing severity, soil carbon fixation, lignin degradation, mineralization of organic nitrogen and hydrolysis of organic phosphorus are enhanced. Denitrification is weakened. Therefore, forest fires have certain positive effects on carbon, nitrogen and phosphorus cycles where soil bacteria and fungi are involved.

Winter-forage crop grazing in the Gore-Mataura area of Southland: using time-series mapping to estimate location and frequency of cropping

Winter grazing of forage crops is a key land-use in southern New Zealand, providing important feed for livestock but has been identified as risky if not managed well, potentially resulting in soil degradation and nutrient losses. We hypothesised that analysing an existing time series of winter-forage maps, derived from satellite imagery could be used to identify how often paddocks are re-used for winter forage. A pilot study was undertaken to explore the practicality and utility of this new method by examining maps derived from satellite images of the Gore-Mataura area, Southland taken in 2013, 2014, 2017, and 2018. Within the study site (67,618 ha), 8925 ha was classed as winter forage in one or more of the source maps. Eighty-five percent of this area was used in only one of the four years, and just 1% in three or four years. High-certainty class pairs for 2013/14 and 2017/18 show two consecutive years of winter forage in the same paddock, 31% or 21% of the time, respectively. These winter-forage crops were generally grown on Brown soils (63%), followed by Pallic and Gley soils. Although, this study was limited by differences in the mapping methodologies of the source maps, it nonetheless demonstrated that potentially valuable data can be derived. It showed a low level of repeat use of paddocks for winter forage grazing over all the years studied, and that Brown soils are more commonly used for winter forage than previous studies suggested.

Soil Carbon, Nitrogen and Phosphorus Concentrations and Stoichiometries Across a Chronosequence of Restored Inland Soda Saline- Alkali Wetlands, Western Songnen Plain, Northeast China

Soil carbon (C), nitrogen (N) and phosphorus (P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) pools, for a chronosequence of three restored wetlands (7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C:N (RCN), C:P (RCP), and N:P (RNP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr (P > 0.05). Soil nutrients changes occurred mainly in the upper layers (≤ 30 cm), and no significant differences were found in deeper soils (> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RCN, RCP, and RNP in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC (r =.0.704, P < 0.01), TN (r =.0.722, P < 0.01), and TP (r =.0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

Soil Nitrogen in Response to Interseeded Cover Crops in Maize–Soybean Production Systems

Improved agronomic management strategies are needed to minimize the impact that current maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) production practices have on soil erosion and nutrient losses, especially nitrogen (N). Interseeded cover crops in standing maize and soybean scavenge excess soil N and thus reduce potential N leaching and runoff. The objectives were to determine the impact that pennycress (Thlaspi arvense L.) (PC), winter camelina (Camelina sativa (L.) Crantz) (WC), and winter rye (Secale cereale L.) (WR) cover crops have on soil N, and carbon (C) and N accumulation in cover-crop biomass. The cover crops were interseeded in maize at the R5 growth stage and in soybean at R7 in four replicates over two growing seasons at four locations. Soil and aboveground biomass samples were taken in autumn and spring. Data from the maize and soybean systems were analyzed separately. The results showed that cover crops had no effect on soil NH4+-N under both systems. However, winter rye decreased soil NO3−-N up to 76% compared with no-cover-crop treatment in the soybean system. Pennycress and WC scavenged less soil N than WR. Similarly, N and C accumulation in PC and WC biomass were less than in WR, in part because of their poor growth performance under the interseeding practice. Until PC and WC varieties with improved suitability for interseeding are developed, other agronomic practices may need to be explored for improving N scavenging in maize and soybean cropping systems to reduce nutrient leaching and enhance crop diversification.

Effects of Cunninghamia lanceolata stand types on the changes of aggregate-related organic carbon and nutrients in surface soil

Exploring the microscopic characterization of organic carbon and nutrients in surface soil of different Chinese fir stands at aggregate scale can lay a theoretical foundation for promoting the sustainable use of soil resources with implications for improving soil health and fertility. We mea-sured the concentrations of soil organic C (OC), total nitrogen (TN), alkali-hydrolyzed nitrogen (AN), Olsen-P (AP), and available K (AK) in aggregate fractions collected from 0-10 cm and 10-20 cm soil layers in three different stands, mixed plantation of Cunninghamia lanceolata and Michelia macclurei (Ⅰ), C. lanceolata and Mytilaria laosensis (Ⅱ) and pure plantation of C. lanceolata (Ⅲ) respectively. Soil aggregates were classified into >2, 0.25-2, and <0.25 mm fractions by a dry-sieving procedure. The organic carbon and nutrient contents of soil aggregates in different stands increased with the decreases of particle size while the contribution rate of aggregates with different particle sizes to soil organic carbon and nutrient storage in 0-10 cm soil layer mainly was (>2 mm)>(0.25-2 mm)>(<0.25 mm), which was (>2 mm)>(<0.25 mm)>(0.25-2 mm) in 10-20 cm soil layer. The average weight diameter (MWD), the contents and stocks of OC, TN, AN and AP in surface soil aggregates of different stands ranked as Ⅰ>Ⅱ>Ⅲ (except the AP in 10-20 cm soil layer), while the contents and stocks of AK ranked as Ⅲ>Ⅰ>Ⅱ. Compared with pure plantation, aggregate structure of surface soil of mixed plantations was more stable, and Ⅰ was better than Ⅱ, because Ⅰ was artificially disturbed but Ⅱwas not. Therefore, the mixed plantation of C. lanceolata and M. macclurei could effectively promote the formation and stability of soil aggregates, and alleviate decomposition of soil organic matter and nutrient loss in plantations.

Dependence of the Dust Emission on the Aggregate Sizes in Loess Soils

Dust emission resulted from soil erosion by wind with significant impacts of soil (nutrient) loss and air pollution of particulate matter (PM). The ejection of dust from soil aggregates due to saltation has been hypothesized to play a major role in dust emission. Yet empirical information on the role of different aggregate sizes in dust emission is still lacking. The main goal of this study was to explore the dust emission threshold in different aggregate sizes of a semiarid loess soil. To this end, we conducted targeted wind-tunnel experiment on dust emission. The results show that dust emission from aggregate at size of 63–250 µm, 250–500 µm, and 500–1000 µm is enabled only under the conditions of saltation. The dust-PM threshold at shear velocities of 0.24–0.52 m/s depends on the aggregates size. Aggregates at the size of saltators (125–500 µm) were the most productive in dust generation by the mechanism of aggregate disintegration. In our bulk sample, the aggregate group of 63–250 µm has the highest contribution to the total dust emission. The study aimed to advance our capability in soil resources management and for model parameterization in dust emission schemes.

Intercropping of small millets for agricultural sustainability in drylands : A review

The scope for enhancement of productivity under irrigated conditions is limited because of over-exploitation of available resources, but there is ample opportunity for boosting yield in drylands by adopting suitable crops and cropping systems. The agricultural sustainability in drylands is comparatively hard to achieve due to different constraints like poor soil fertility, lack of irrigation facilities and moisture stress, small holdings and less investment in agriculture. Choice of ecologically sound crops as millets and adoption of intercropping systems are two of suitable options for maximization of productivity in drylands. Millets are ancient nutri-cereals which can play a crucial role in food as well as nutritional security of the country and can assure agricultural sustainability in drylands under intercropping system. The combination of cereal and legume in intercropping is mostly preferred by the farmers in subsistence farming targeting livelihood security. Experiments carried out on intercropping of some small millets in India and abroad clearly indicated numerous benefits like enhancement of crops productivity, greater resource use efficiency, check in run-off of water and soil conservation in erosion prone areas, prevention of loss of soil nutrients, improvement of soil health, insurance against crop failure under aberrant weather conditions, higher monetary return and benefit-cost ratio. But the performance of all small millets is not tested under intercropping under different regions. There is still insufficiency in research on small millets based intercropping system which can create further scope for agricultural sustainability of drylands.

Combined Cultivation Pattern Reduces Soil Erosion and Nutrient Loss from Sloping Farmland on Red Soil in Southwestern China

Crops are usually planted on sloping land in mountainous areas due to limited suitable land area. This results in serious soil erosion and loss of nitrogen (N) and phosphorus (P) to land degradation and water eutrophication. It is important to adopt appropriate cultivation practices to change this situation. However, few long-term in situ measurements are available to assess the magnitude of effects of combined cultivation patterns on soil erosion and nutrient loss from sloping farmland with red soil, as well to quantify N and P losses through runoff and sediment transport. A field trial with the cash crop (CC) Nicotiana tabacum was carried out under natural rainfall conditions on sloping farmland with red soil in Yunnan, China during 2014–2017. Four cultivation patterns were applied. They included NVF (No fertilizer application + Vertical ridge + Film covered), OVF (Optimizing fertilizer application + Vertical ridge + Film covered), OHF (Optimizing fertilizer application + Horizontal ridge + Film covered), and OHFR (Optimizing fertilizer application + Horizontal ridge + Film removed). The first two treatments belonged to the vertical ridge (VR) group, and the remaining treatments belonged to the horizontal ridge (HR) group. Results indicated the HR group performed significantly better than the VR group, especially the OHFR treatment, in terms of the HR group producing average runoff (177.12–182.27 mm), sediment loss (2673.33–3309.17 kg·ha−1), and nutrient loss of total nitrogen (TN) (7.58–7.93 kg·ha−1), total phosphorus (TP) (1.00–1.09 kg·ha−1) through runoff, TN (3.53–4.72 kg·ha−1), TP (2.59–2.76 kg·ha−1) through sediment. TN was lost mainly through runoff transport, while TP was lost mainly through sediment transport. On average, the HR group decreased runoff, sediment, total N and P loss by 39% to 73% relative to the OVF treatment, whereas NVF treatment increased 3% to 30% of those (p &lt; 0.05). Under four cultivation patterns, total dissolved nitrogen (TDN) was the dominant form, which accounted for 71–77% of TN. The average percentage of NO3−-N/TN was about 45–52%, much higher than NH4+-N/TN of around 8–10% in runoff. Total dissolved phosphorus (TDP) made up about 48–59% of TP in runoff. Redundancy analysis (RDA) showed that sediment, runoff, and soil pH were the three key factors controlling nutrient loss. In conclusion, OHFR is recommended because it consistently outperformed other patterns in terms of reducing runoff, sediment, and nutrient losses.