Soil Nutrient Accumulation Research Articles

Increasing yields while reducing soil nutrient accumulation by straw strip mulching in the dryland wheat (Triticum aestivum L.) cropping system of Northwest China

Surface mulching is an effective strategy to increase yields in rainfed agroecosystems. The plastic film residue and overuse of chemical fertilizer cause a serious non-point source pollution and high production input cost. With mulching, farmers typically attempt to maintain the balance of soil nutrients and reduce fertilizer use while ensuring high yields. Straw strip mulching (SM) is a new mulching technique, but the effects on nutrient uptake have not been studied yet. Therefore, 19 field comparative experiments were conducted in four growth seasons of winter wheat with three mulching treatments: (1) straw strip mulch (SM), a partial ground mulching using whole corn stalks that alternate with planting strips without mulch; (2) full-field plastic film mulching (PM); and (3) no mulching with wheat sown in rows, as a control (CK). Compared with CK, on average over all experiments, SM increased grain yield by 11.5%, biomass by 19.0%, the total aboveground uptakes of nitrogen (N), phosphorus (P) and potassium (K) by 16.1%, 18.4% and 22.9%. There were no significant differences between SM and CK in N and P requirements, the N, P and K concentrations in grain. The increased total aboveground uptake of each nutrient was closely associated with higher biomass, grain yield and straw yield (r = 0.66 −0.84, P < 0.01). Relative to CK, SM significantly decreased the total accumulation of residual NO3-N in the top 100 cm at maturity stage by 32.3% (22.7 kg ha-1) in typical fertilization (N, 120 kg ha-1; P2O5, 90 kg ha-1) and by 33.8% (45.8 kg ha-1) in high fertilization (N, 150 kg ha-1; P2O5, 120 kg ha-1), and the leaching of NO3-N into the deep soil below 40 cm. When only grain nutrients exported from the field after harvest in typical fertilization, N balance in SM, PM and CK accounted for 43.8%, 38.5% and 48.6% of N input, while P balance for 74.8%, 74.0% and 78.4% of P input, respectively, indicating possible saving potentials in fertilizer costs for all treatment, but the saving potential of P is much greater than that of N. Relative to PM, SM had similar the total aboveground nutrients uptake, similar to or slightly less grain yields, and higher economic benefit. SM is suitable for popularizing in a semiarid rainfed agroecosystem.

Effects of Seven-Year Fertilization Reclamation on Bacterial Community in a Coal Mining Subsidence Area in Shanxi, China.

The restoration of soil fertility and microbial communities is the key to the soil reclamation and ecological reconstruction in coal mine subsidence areas. However, the response of soil bacterial communities to reclamation is still not well understood. Here, we studied the bacterial communities in fertilizer-reclaimed soil (CK, without fertilizer; CF, chemical fertilizer; M, manure) in the Lu’an reclamation mining region and compared them with those in adjacent subsidence soil (SU) and farmland soil (FA). We found that the compositions of dominant phyla in the reclaimed soil differed greatly from those in the subsidence soil and farmland soil (p < 0.05). The related sequences of Acidobacteria, Chloroflexi, and Nitrospirae were mainly from the subsided soil, whereas those of Alphaproteobacteria, Planctomycetes, and Deltaproteobacteria were mainly derived from the farmland soil. Fertilization affected the bacterial community composition in the reclaimed soil, and bacteria richness and diversity increased significantly with the accumulation of soil nutrients after 7 years of reclamation (p < 0.05). Moreover, soil properties, especially SOM and pH, were found to play a key role in the restoration of the bacterial community in the reclaimed soil. The results are helpful to the study of soil fertility improvement and ecological restoration in mining areas.

Wood production and nutritional and antioxidant status of field-grown Eucalyptus under a differential supply of lime and copper plus zinc

The Eucalyptus grandis L. plantations for industrial purposes (e.g., wood charcoal and pulp) are largely adopted worldwide, mainly in acidic and poorly fertile soils. The application of lime to soil is recommended for eucalyptus plantation, but lime reduces the availability of metallic micronutrients to plants. Therefore, the aim of this study was to investigate the performance of field-grown Eucalyptus grandis in Ferralsol amended with lime at different rates (0.0 and 1.6 and 3.7 Mg ha-1) and Cu plus Zn [0.0 and 0.0 kg ha-1 (-CuZn) and 0.5 and 1.5 kg ha-1 (+CuZn)]. The soil chemical attributes, shoot biomass, and nutrient accumulation were evaluated, while nutrient use efficiency, chlorophyll (Chl) and flavonoid (Flav) contents, and enzymatic antioxidant performance [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX), guaiacol peroxidase (GPOX), and glutathione peroxidase (GPX)] were assayed to assess the nutritional status of the plants. Despite the lime application rate increasing Ca and Mg soil availabilities, effective cation exchange capacity (eCEC), base saturation (BS), and pH values, the available Cu, Fe, and Zn concentrations decreased at 6 and 30 months after planting. Conversely, Mn soil availability increased with lime application rates. Liming augmented Cu-, Fe-, Mn-, and Zn-use efficiency, while +CuZn supply increased enzymatic antioxidant performance in 30-month-old plant. Overall, the combined application of lime and +CuZn enhanced shoot biomass relative to that of non-treated plants. However, there was no observed difference in shoot biomass in 30-month-old limed and non-limed eucalyptus trees that were supplied with +CuZn. This result can be partially explained by the improvement in soil chemical attributes, such as soil pH, eCEC, and BS. In conclusion, the use of integrative approaches and temporal evaluations provided new insights into wood yield, biochemical traits, antioxidant metabolism, and the nutritional status of field-grown eucalyptus under lime and +CuZn application rates.

Prokaryotic Community Succession in Bulk and Rhizosphere Soils Along a High-Elevation Glacier Retreat Chronosequence on the Tibetan Plateau.

Early colonization and succession of soil microbial communities are essential for soil development and nutrient accumulation. Herein we focused on the changes in pioneer prokaryotic communities in rhizosphere and bulk soils along the high-elevation glacier retreat chronosequence, the northern Himalayas, Tibetan Plateau. Rhizosphere soils showed substantially higher levels of total organic carbon, total nitrogen, ammonium, and nitrate than bulk soils. The dominant prokaryotes were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Crenarchaeota, Bacteroidetes, and Planctomycetes, which totally accounted for more than 75% in relative abundance. The dominant genus Candidatus Nitrososphaera occurred at each stage of the microbial succession. The richness and evenness of soil prokaryotes displayed mild succession along chronosequene. Linear discriminant analysis effect size (LEfSe) analysis demonstrated that Proteobacteria (especially Alphaproteobacteria) and Actinobacteria were significantly enriched in rhizosphere soils compared with bulk soils. Actinobacteria, SHA_109, and Thermoleophilia; Betaproteobacteria and OP1.MSBL6; and Planctomycetia and Verrucomicrobia were separately enriched at each of the three sample sites. The compositions of prokaryotic communities were substantially changed with bulk and rhizosphere soils and sampling sites, indicating that the communities were dominantly driven by plants and habitat-specific effects in the deglaciated soils. Additionally, the distance to the glacier terminus also played a significant role in driving the change of prokaryotic communities in both bulk and rhizosphere soils. Soil C/N ratio exhibited a greater effect on prokaryotic communities in bulk soils than rhizosphere soils. These results indicate that plants, habitat, and glacier retreat chronosequence collectively control prokaryotic community composition and succession.

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.

Effects of Fencing on Vegetation and Soil Nutrients of the Temperate Steppe Grasslands in Inner Mongolia

Grazing exclusion has been widely implemented in degraded grassland. However, the changes of plant communities and soil nutrients in response to fencing are still controversial. Thus, the effects of free grazing, 17 and 36 years of fencing on the plant biomass and litter biomass, carbon (C), nitrogen (N) and phosphorus (P) concentrations and stocks of plant, litter and soil were investigated in the temperate steppe grasslands of northern China. The results indicated that fencing increased the aboveground live biomass and litter biomass. In addition, fencing increased C, N and P stocks of aboveground live biomass, litter biomass and soil. Although root biomass and its nutrient stocks were also significantly increased by 17 years of fencing, they were decreased with fencing extending from 17 to 36 years. Moreover, there were no significant differences in aboveground live biomass and soil N and P stocks between 17 and 36 years of fencing. Litter biomass and its C, N and P stocks were positively correlated with soil C, N and P stocks. Our results demonstrated that 17 years of fencing is an effective way to restore vegetation and soil nutrients in the temperate steppe of Inner Mongolia, but a longer fencing duration has no further positive effects on biomass production and soil nutrients accumulation.

Dominant environmental factors influencing soil metal concentrations of Poyang Lake wetland, China: Soil property, topography, plant species and wetland type

Although an important sink for contaminants including metals, wetland soils can release metals and thus cause a secondary pollution when environmental condition changes. Metals in wetland soils are influenced by a variety of environmental factors, including soil property, topography, wetland type, and plant species. However, the degree of importance of these environmental factors to wetland soil metals has not yet been clearly explained. In this study, the effect of these environmental factors on soil metal concentrations (i.e., Cr, Ni, Cu, Zn, As, Cd, and Pb) was explored in Poyang Lake wetland. Correlation, redundancy, and variance decomposition analyses were employed. The results indicate that the concentrations of Cu, Pb, Cd, Cr, and Zn were higher than their background values. Statistical analysis showed that all environmental factors explained 55.90% of the total variance (either p < 0.01 or p < 0.05). Soil properties, mainly TN, TP, NO3−-N, PO43−-P, and TOC played a dominant role on soil metal concentrations, which explained 27.91% of the total variance, followed by wetland type and topography, which explained 5.55% and 3.19% of the total variance, respectively. Soil nutrients significantly promoted metal aggregation in soil (p < 0.01 or p < 0.05). Lower elevations were favorable for soil metal accumulation (p < 0.05). Wetland type indirectly influenced soil metal concentrations, where wetlands with low flat terrain promoted soil nutrients accumulation, thus enhancing metal accumulation by soils. Plant species explained 6.72% of the variance, and Artemisia and Phalaris were positively correlated with specific metals in soils. This study provides a theoretical basis for retaining healthy wetland ecosystems.

A beneficial relationship: associated trees facilitate termite colonies (Macrotermes michaelseni) in Namibia

AbstractIn many tropical ecosystems, termites are important ecosystem engineers. Mound‐building termite species often contribute to topographical landscape heterogeneity, and the associated accumulation of soil moisture and nutrients affects the spatial distribution of plant communities. Plants that grow next to the termite mound are known to benefit from the provided nutrients and water storage. The other way around, protection against erosion and cooling effects on the microclimate of the mounds imposed by associated trees have been described. However, little is known regarding the influence of tree parameters and the long‐term effects on colony development. In an interval of 12 yr, we studied all Macrotermes michaelseni mounds occurring within one square kilometer of Namibian thornbush savanna in terms of morphology, life history, and associated plants, with a focus on the role of associated trees which grow directly adjacent to the termite mounds. Here, we present the results of a combined analysis of the character states recorded at the termite mound and the associated trees. More than 50% of all 345 recorded termite mounds were associated with a tree. Mounds with associated trees showed increased activity, growth, and height. Mound growth within the study period was correlated positively with the canopy coverage by the associated tree, while total mound heights were correlated non‐linear with medium canopy coverage of about 40%. Mounds with a tree covering the sun's average zenith (north) were taller, grew most within 12 yr, and were more likely to be active than those with no northern canopy coverage. Mounds associated with the evergreen Boscia albitrunca attained highest average height (195.06 ± 11.76 cm). We conclude that vital parameters like growth, size, and activity of the termite colonies are facilitated by shading associated trees. These benefits were shown to take significant effect within the span of 12 yr. This indicates a proper long‐term mutualism, not a loose alliance and not an obligative eu‐symbiosis. Therefore, we propose to use the term “partner tree” for trees associated with M. michaelseni mounds.

Spatial variations in soil organic carbon, nitrogen, phosphorus contents and controlling factors across the “Three Rivers” regions of southwest China

Based on the data of China Geochemical Baselines project, geostatistical analysis was used to investigate the spatial variations in soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) contents across the “Three Rivers” regions of southwest China, and the factors affecting them were analyzed by the redundancy analysis (RDA) and Person's correlation. Results showed that, the average content of SOC, TN and TP in the study area were 7.20 g/kg, 0.84 g/kg and 0.55 g/kg, respectively. The SOC and TN contents showed an obvious enrichment characteristic with great spatial variability, while TP content was stable on regional scale. The SOC, TN and TP contents decreased with elevation increase in the northern frigid highland, but showed an opposite character in the southern tropical & subtropical, which actually reflected the control of temperature on them. Combined with that there were higher SOC, TN and TP contents in subalpine meadow soil and red earth–yellow earth of the middle latitude zone, these suggested that the suitable temperature was conducive to the accumulation of soil nutrients. The weak positive correlation between population density and soil nutrients, together with high level of soil nutrients in the vicinity of large cities, demonstrated that human activities had significantly increased the soil nutrients contents in the study area. The RDA results showed that soil nutrients in the northern frigid highland were mainly controlled by the environmental factors dominated by temperature and soil structural factors dominated by parent materials with the total explanatory power as high as 75.87%, while in the southern tropical & subtropical mainly by the environmental factors dominated by chemical and biological weathering and the biological factors dominated by vegetation with the total explanatory power as high as 88.53%. The above factors superimposing a certain degree of human activities converged to cause that the SOC and TP contents in the south were higher than that in the north while the TN content was lower than that in the north.

Biophysical evaluation of fertility islands in the Arid Chaco (Argentina)

Forests degradation in arid and semi-arid lands may conduct to the formation of “fertility islands” due to the accumulation of soil particles, water, nutrients and biomass under trees and shrubs. In the Arid Chaco fertility islands are characterised by the presence of Prosopis flexuosa and Larrea divaricata. The objective was to evaluate biophysical variables in soil, microclimate and the plant response under canopy and in intercanopy. Infiltrability, microtopography, soil bulk density, soil and air moisture and temperature, and light were measured under the canopy, at the limit of the canopy and in the intercanopy. These variables were correlated with the litter and plant frequencies associated with the fertility islands. P. flexuosa canopy and litter understorey tend to maintain more soil moisture compared with the intercanopy, by reducing soil and air temperature and by increasing air moisture. This increases the frequency of Dyksterhuis’ decreaser species. Under L. divaricata the canopy effect is not as effective as that of P. flexuosa and understorey plant response is not significative.

Effects of Rock Fragments on the Soil Physicochemical Properties and Vegetation on the Northeastern Tibetan Plateau

Stony soils are very widely distributed and contain abundant rock fragments (&amp;gt;2 mm), which impose major effects on soil properties and plant growth. However, the role of rock fragments is still often neglected, which can lead to an inadequate understanding of the interaction between plants and soil. Undisturbed soil columns were collected from three alpine grasslands on the Qilian Mountain, and the X-ray computed tomography method was applied to investigate the characteristics of rock fragments. The results showed there was significant difference in number density, volumetric content and surface area density of rock fragment among the three grasslands, and followed the order of alpine meadow &amp;gt; alpine steppe &amp;gt; alpine desert steppe. In addition, the soil organic carbon, total nitrogen, total phosphorus, available phosphorus, N-NH4+, and N-NO3− contents in fine earth all increased with increasing number density, volumetric content and surface area density but to different degrees. Furthermore, positive correlations were observed between the rock shape factor and belowground biomass (R2 = 0.531, p &amp;lt; 0.05), between the rock volumetric content and aboveground biomass (R2 = 0.527, p &amp;lt; 0.05), and between number density and Simpson’s index (R2 = 0.875, p &amp;lt; 0.05). Our findings suggest that within a certain range, the increase in rock fragment content is conducive to soil nutrient accumulation and soil water storage and circulation and changes plant features, which contributes to the growth of plants. In addition, rock fragments should be given more consideration when investigating the relationships between soil and vegetation and their response to climate change in future studies.

Sewage sludge as organic matrix in the manufacture of organomineral fertilizers: Physical forms, environmental risks, and nutrients recycling

The use of organomineral fertilizers (OMFs) has grown worldwide, mainly in tropical conditions, combining economics and environmental management. Our study used a sewage sludge (SS) rich in Zn as the organic matrix in the manufacture of OMFs, with the following objectives: i) to select the best OMF physical form; ii) to evaluate environmental risks associated with their application; iii) to recycle SS nutrients for soybean (Glycine max) production; iv) to verify their benefits to soil microbial activity and other soil functions. For each soil individually, a clay and a sandy clay loam, six treatments were tested: control (CT, without fertilization); mineral fertilization (MF); MF plus Zn and B (MFZn + B); and three distinct physical forms for the OMFs [powder (Pw), granule (G), and pellet (Pt)], all calculated to provide 100 kg of P2O5 and performed in four blocks. Amending SS-OMFs did not represent an environmental risk in terms of spreading pathogens and hazardous trace elements. In comparison with MFs, SS-OMFs enhanced nutrients accumulation, pod numbers, and nodulation, as well as soil microbial activity, but did not affect shoot and root dry masses and enzymatic activities at early stages of soybean development (60 d after planting). They were also capable to supply Zn and B to plants and their distinct physical forms did not affect microbiological indicators of soil quality or nutrients accumulation in plant tissues. Overall, SS-OMFs seems to be a promising alternative for sustainable use of SSs in soybeans avoiding their disposal in landfills, but field studies are still needed to ratify the findings under more realistic conditions.

Decreases in soil P availability are associated with soil organic P declines following forest conversion in subtropical China

The large-scale conversion of natural forests to plantations profoundly alters the accumulation and transformation of soil nutrients. However, our understanding of how soil P responds to forest conversion is far from complete. This study aims to explore the changes in various soil P fractions associated with forest conversion in subtropical forest soils, where P is known to be relatively scarce. Soil samples were collected from an evergreen broad-leaved forest, a secondary forest, and two plantation forests. The soil properties, P fractions, amino sugars, and phosphatase activities were determined. The replacement of natural forests by plantation forests was associated with reductions in soil labile inorganic P (Pi) and organic P (Po), moderately labile Po, and total P. Soil amino sugars, which are indicative of historical populations of soil microbes, consistently decreased following forest conversion. We also found significant positive relationships between most P fractions and amino sugars content. A structural equation model suggested that Po, especially labile and moderately labile Po, were the potential sources of labile Pi. The positive relationship between labile Pi and acid phosphatase activity indicates that microbes are involved in soil P transformations by regulating P-hydrolytic enzymes activity. Overall, our work suggests that forest conversion significantly decreased most soil P fractions, including labile Pi, labile Po, and moderately labile Po, partly due to the declines in microbial populations that play an important role in releasing P from litter and root necromass. Organic P may play a vital role in sustaining P availability through organic P decomposition facilitated by microbial phosphatases, resulting in the release of labile P in the forest soils. These findings provide a mechanistic understanding of soil P cycling following forest conversion in low available P subtropical forests.

Comparison of C:N:P Stoichiometry in the Plant–Litter–Soil System Between Poplar and Elm Plantations in the Horqin Sandy Land, China

Afforestation is among the most effective means of preventing and controlling desertification. Silver poplar (Populus alba) is commonly planted tree species for afforestation of the Horqin Sandy Land of China. However, this species has exhibited some drawbacks such as top shoot dieback, premature senescence and mortality, and soil and ecosystems degradation. In contrast, Siberian elm (Ulmus pumila) rarely experiences these problems in the same regions. Ecological stoichiometry plays a vital role in exploring ecological processes and nutrient cycle relationships in plant–litter–soil systems. To explore the differences in the carbon (C), nitrogen (N), and phosphorus (P) balance, the stoichiometry characteristics and stoichiometric homeostasis in elm and poplar plantations in the Horqin Sandy Land, we measured C, N, and P concentrations in leaves, branches, roots, litter, and soils and analyzed N and P resorption efficiencies in the two plantations. The results showed that soil C and N concentrations, C:P, and N:P were greater in the elm plantation than in the poplar plantation. The leaf and root C:P and N:P during summer and litter N and P concentrations were greater, whereas N and P resorption efficiencies were lower, in the elm plantation than in the poplar plantation. Generally, elm exhibited greater N:P homeostasis than poplar. N and N:P homeostasis were greater in roots than in leaves and branches in the elm plantation, but they varied with soil N concentration and N:P in the poplar plantation. These findings indicate that poplar exhibited more developed internal nutrient conservation and allocation strategies but poor nutrient accumulation in soil, which may contribute to degradation of poplar plantation. In contrast, elm tended to return more nutrients to the soil, showing an improved nutrient cycle in the plant–litter–soil system and increased soil C and N accumulation in the elm plantation. Therefore, compared with poplar, elm may be a more suitable afforestation tree species for the Horqin Sandy Land, in terms of promoting the accumulation of soil nutrients and enhancing nutrient cycling in the plant–litter–soil system.

Responses of Soil Abiotic Properties and Microbial Community Structure to 25-Year Cucumber Monoculture in Commercial Greenhouses

Cucumber monoculture could cause soil salinization and acidification, soilborne diseases, and eventually yield loss. However, after a 25-year monoculture in Wafangdian county, Liaoning province, China, cucumber yields have remained satisfactory. In the present study, we investigated how the soil abiotic and biotic properties, in addition to soil rhizosphere microbial community structure in the greenhouses, could still sustain plant growth after such long-term monoculture production. Soil organic carbon, total nitrogen, and available nitrogen were accumulated significantly after monoculture. Such increasing soil fertility was accompanied by increased soil microbial abundance, which reshaped soil microbial community structure. Both bacterial and fungal diversity, including observed and estimated richness, Heip evenness, and Shannon diversity, decreased significantly, while the monoculture period had a greater influence on fungal diversity than on bacterial diversity. Although the high accumulation of soil nutrients increased soil salinity and acidity, the abundance of potential plant pathogenic fungi did not show an obvious increase. These results indicated that maintaining soil abiotic and biotic properties using organic fertilizers and balanced chemical fertilizers, especially improving potassium fertilizer application, could be useful measurements for the sustainable development of greenhouse vegetable production. In addition, appropriate management strategies should be considered to reduce the potential risk of soil salinization.

Assessment of Potato Farmland Soil Nutrient Based on MDS-SQI Model in the Loess Plateau

Soil nutrients are essential nutrients provided by soil for plant growth. Most researchers focus on the coupling effect of nutrients with potato yield and quality. There are few studies on the evaluation of soil nutrients in potato fields. The purpose of this study is to investigate the soil nutrients of potato farmland and the soil vertical nutrient distributions, and then to provide a theoretical and experimental basis for the fertilizer management practices for potatoes in Loess Plateau. Eight physical and chemical soil indexes were selected in the study area, and 810 farmland soil samples from the potato agriculture product areas were analyzed in Northern Shaanxi. The paper established the minimum data set (MDS) for the quality diagnosis of the cultivated layer for farmland by principal component analysis (PCA), respectively, and furthermore, analyzed the soil nutrient characteristics of the cultivated layer adopted soil quality index (SQI). The results showed that the MDS on soil quality diagnosis of the cultivated layer for farmland soil included such indicators as the soil organic matter content, soil available potassium content, and soil available phosphorus content. The comprehensive index value of the soil quality was between 0.064 and 0.302. The SPSS average clustering process used to classify SQI was divided into three grades: class I (36.2%) was defined as suitable soil fertility (SQI &lt; 0.122), class II (55.6%) was defined as moderate soil fertility (0.122 &lt; SQI &lt; 0.18), and class III (8.2%) was defined as poor soil fertility (SQI &gt; 0.186). The comprehensive quality of the potato farmland soils was generally low. The proportion of soil nutrients in the SQI composition ranged from large to small as the soil available potassium content = soil available phosphorus content &gt; soil organic matter content, which became the limiting factor of the soil organic matter content in this area. This study revolves around the 0 to 60 cm soil layer; the soil fertility decreased gradually with the soil depth, and had significant differences between the respective soil layers. In order to improve the soil nutrient accumulation and potato yield in potato farmland in northern Shaanxi, it is suggested to increase the fertilization depth (20 to 40 cm) and further study the ratio of nitrogen, phosphorus, and potassium fertilizer.

Long-Term Growth of Alfalfa Increased Soil Organic Matter Accumulation and Nutrient Mineralization in a Semi-Arid Environment

Land use patterns and vegetation coverage in semi-arid areas of the Loess Plateau have undergone great changes due to the implementation of the “Grain for Green” project. The introduction of legume pasture species, such as alfalfa (Medicago sativa L.) and sweet clover (Melilotus officinalis L.), is one of the most efficient methods of vegetation restoration and reconstruction in this region. However, there is a need for an effective assessment of the root system distribution and its interaction with soil after long-term introduction. An experiment involving the introduction of alfalfa and sweet clover on abandoned farmlands was initiated in 2003 to assess the long-term effects. After 17 years, root and soil samples at depths of 0–20 and 20–60 cm were collected to characterize the root biomass, root carbon (C), nitrogen (N), and phosphorus (P), soil microbial biomass carbon (MBC) and nitrogen (MBN), soil organic carbon (SOC), and soil N and P. The results showed that the root biomass density of alfalfa in the 0–20 and 20–60 cm layers (63.72 and 12.27 kg m–3, respectively) were significantly higher than for sweet clover (37.43 and 8.97 kg m–3, respectively) and under natural abandonment (38.92 and 9.73 kg m–3, respectively). The SOC, total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), nitrate-nitrogen (NO3–-N), MBC and MBN in the 0–20 and 20–60 cm layers were higher after alfalfa introduction compared with sweet clover introduction and natural abandonment, although the ammonia-nitrogen (NH4+-N) concentration in the 0–20 cm layer was lower. There were significantly positive correlations between root biomass density and both soil nutrients and microbial biomass, while there was a negative correlation between the soil NH4+-N and root biomass density. These results indicate that alfalfa root growth improved soil organic matter accumulation and nutrient mineralization. The accumulation and mineralization of soil nutrients also guaranteed root and microorganism growth. Therefore, it was concluded that alfalfa introduction will promote soil nutrients immobilization and mineralization and may enable sustainable land use in the semi-arid region of the Loess Plateau, China.

Study on Suitable Water Resource Irrigation Rate of Tomato under Solar Greenhouse in Autumn

The shortage of water resources is increasing worldwide. For saving water resources, the study of horticultural plant water saving irrigation technology has greatly ecological and social significance. In this experiment, tomato was used as the test material with drip irrigation technology. Under same fertilizer rate, three levels of irrigation water were set: High irrigation Water (HW), Medium Irrigation Water (MW) and Low Irrigation Water (LW). The effects of different Irrigation levels on growth, yield, water use efficiency and soil nutrient content were investigated. The results show that the plant height and the accumulation of soil nutrients declined while the yield and water use efficiency increased with the decrease of irrigation rate. The average plant height of LW tomato was significantly lower than that of HW. Compared with HW, tomato yield and water use efficiency under LW increased by 6.6% and 65.4%, respectively, and the average irrigation rate decreased by 55.21%. The accumulation of N, P and K under LW in the 40∼60cm soil layer was significantly lower than HW by 37.3%, 78.5% and 60.9%, respectively. LW has a positive effect on the increase of tomato yield and the reduction of nutrient leaching and accumulation.

Associated soil aggregate nutrients and controlling factors on aggregate stability in semiarid grassland under different grazing prohibition timeframes

Grazing prohibition is an effective measure in improving soil stability and ecological quality. However, only a limited number of studies have been published on the dominant factors that impact soil aggregate stability and their associated effects on nutrient distribution for different size soil aggregates under long-term grazing prohibition management. In this study, we investigated variation in soil aggregate stability and nutrient distribution characteristics in semiarid grassland sites under different grazing prohibition timeframes (0years [GP0], 11years [GP11], 26years [GP26], and 36years [GP36]). Results showed that organic carbon (C) and total nitrogen (TN) concentrations in soil aggregates decreased at GP11 before progressively increasing and reaching its highest value at GP36, and the total phosphorus (TP) concentration did not change significantly. Most nutrients accumulated in macroaggregates (> 0.25mm) under grazing prohibition, and the nutrient stoichiometry in soil aggregates increased after 26years. Compared to the control (GP0), the mean weight diameter (MWD) value of the soil stability index increased at GP11 (21.7%) and decreased at GP26 (18.9%). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) also showed that the proportion of stable organic C-related functional groups (i.e., alkene-C and aromatic-C) in macroaggregates were higher at GP11 and GP36 than at GP26. Furthermore, principal component analysis (PCA), partial least squares path modeling (PLS-PM), and the relative importance of regressors all showed that glomalin-related soil proteins (GRSP) and nutrients indirectly improved aggregate stability in semiarid grassland through their influence on the GRSP accumulation potential and nutrient stoichiometry. Generally, after 26years grazing prohibition had a positive effect on soil aggregate stability and nutrient accumulation in the semiarid grassland sites investigated for this study. Results from this study provide a theoretical basis to select appropriate grazing prohibition timeframes under grassland management initiatives to optimize ecological quality measures in semiarid regions.

Evaluation of ecosystem service of straw return to soil in a wheat field of China

Crop straw is an important natural resource in China because it is rich in nutrients. When returned to fields after harvests, the straw can improve soil quality and the next crop’s yield. Evaluating the economic values of the main ecological services of a farmland ecosystem while implementing the straw return technique can be a more systematic and comprehensive approach to better understand the contribution of straw return to the development of ecological agriculture. Based on the data of a field experiment established in 2010 with varying numbers of years of straw return, four ecological services, i.e., agricultural product and industrial raw materials, atmospheric regulation and purification, soil nutrient accumulation, and water conservation, were selected to estimate a net ecosystem service value (ESV) of a wheat field’s ecosystem services. Agro-ecosystem service appraisal theories were applied to estimate the economic value of each service. Results showed that straw returning improved the total ESV in the wheat system. Compared to the no straw return treatment, 1 year, 3 years, 5 years or 7 years of straw returning altered the economic value of the agricultural product and industrial raw materials (EVAIM) by –5.93% to 7.84% and improved atmospheric regulation (EVAR) by 13.66%-30.80%, soil nutrient accumulation (EVSNA) by 59.87%-233.31% and water conservation (EVWC) by 2.60%-13.26%. The total ESV of wheat plots with 1-7 years of straw returning was 3.67%-27.41% higher than that with no straw return, and the total ESV increased with the increase in years of straw return. The proportion of EVAIM out of the total ESV in this wheat field system was highest (accounted for 47.09%-55.64%), followed by EVAR and EVWC. The value of EVSNA was the lowest. However, the proportion of EVSNA was higher than that of water conservation after the fifth year of straw return. In general, the adoption of continuous straw returning in a wheat field ecosystem is ecologically valuable. The results can inform the development and implementation of ecological compensation policies involving straw return. Keywords: ecosystem service value, rice-wheat rotation, straw returning, farmland ecosystem, economic value, ecological service function DOI: 10.25165/j.ijabe.20211401.5698 Citation: Cui S Y, Cao G Q, Zhu X K. Evaluation of the ecosystem service of straw return to soil in a wheat field of China. Int J Agric & Biol Eng, 2021; 14(1): 192–198.