Soil Phosphorus Status Research Articles

Impact of sewage sludge, nanoparticles, and clay minerals addition on cucumber growth, phosphorus uptake, soil phosphorus status, and potential risk of phosphorus loss

There is little information about the impact of sewage sludge, nanoparticles, and clay minerals on cucumber ( Cucumis sativus L.) growth and phosphorus content in different plant parts. In this study we treated a soil with different rates of sewage sludge (1%, 5%, and 10%), along with two nanoparticles (SiO 2 and nano-montmorillonite at 0 and 1%), and two clay minerals (zeolite and vermiculite at 0 and 3%). We aimed at investigating the impact of these amendments on cucumber growth, phosphorus content in root, shoot, and fruit, phosphorus content in rhizosphere and non-rhizosphere soils, and determining the impact of these amendments on the potential risk of phosphorus loss from soil. Plant growth in the soil treated with sewage sludge at 1% and 5% was higher than that at 10% sewage sludge, while the cucumber in the 10% sewage sludge plus 1% nano-montmorillonite-treated soil dried out. Phosphorus content in fruit was higher than in root and phosphorus in root was higher than that in shoot. Cucumber plant in the 10% sewage sludge treated soil had the highest amount of phosphorus compared to the other treatments, while plants in the nanoparticles and clay minerals treatments had lower content of phosphorus than the control. The highest phosphorus content was extracted from soil treated with 10% sewage sludge, while the lowest was extracted from the soil treated with nanoparticles and clay minerals. In average of all treatments, soil phosphorus extracted by water-extractable phosphorus in the rhizosphere soil was higher than phosphorus in the non-rhizosphere soil. The results indicated that calcium chloride-extractable phosphorus was more effective in predicting phosphorus uptake than water-extractable phosphorus and Olsen-extractable phosphorus. Also, the soil treated with sewage sludge at 5% and 10% would potentially increase the risk of phosphorus losses. We concluded that the soil treated with 1% sewage sludge, with or without nanoparticles or clay minerals, could provide the amount of phosphorus required for the growth of cucumber, while there was no obvious potential risk of phosphorus loss, making this treatment more beneficial for cucumber. • Cucumber growth increased in soil at 1% sewage sludge; no phosphorus loss occurred. • Highest plant phosphorus was observed in soil at 10% sewage sludge. • Correlation of root P and CaCl 2 -extracted P was highest.

Assessment of soil quality indicators and phosphorus status of the land resources on both sides of Sohag-Safaga highway, Eastern Desert, Egypt

Assessment of soil quality indicators and phosphorus status of the land resources on both sides of Sohag-Safaga highway, Eastern Desert, Egypt

Drying-rewetting changes soil phosphorus status and enzymatically hydrolysable organic phosphorus fractions in the water-level fluctuation zone of Three Gorges reservoir

The water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) in China has been frequently subjected to drying and rewetting (DRW) since the construction of the Three Gorges Dam. The increased soil labile phosphorus (P) after DRW potentially increases the risk of the release of soil P from the WLFZ to the reservoir water. Our study explored the effects of DRW on the P status of WLFZ soils. In June 2018, surface soil (0–2 cm) samples were taken in the WLFZ at two altitudes of in a tributary (Pengxi River) of the TGR. The labile P and the soil properties were determined in both field-moist and air-dried soils, and the organic P fractions in the bicarbonate extracts were determined through enzymatic hydrolysis. In addition, the contributions of various sources to the increase of soil labile P after DRW were quantified by using the improved organic P fractions tracing method. The results showed that the contents of TP, OP, Olsen-TP, Olsen-IP, Olsen-OP and the proportion of bioavailable P in the field-moist soils at 145 m were significantly lower than those at 165 m. Inorganic P was the main contributor to the increase in P in the bicarbonate extractants following DRW. Pmic, OM and Feox were found to be the main factors influencing the increase in soil labile P after DRW. The organic P fractions, such as diester P, phytate-like P and unknown P, also increased significantly after DRW. The transformation of slowly cycling P contributed 78% and 51% to the increase in Olsen-TP at 145 m and 165 m, respectively, and the death of microorganisms contributed 16% and 18%. The proposed method to quantify the source of increased soil labile P after DRW potentially contributes to reduce the release risk of P from the continent to the receiving aquatic systems.

Soil phosphorus fractions and their availability over natural succession from clear-cut of a mixed broadleaved and Korean pine forest in northeast China

To assess phosphorus (P) status of forest soil under naturally restored vegetation, P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Korean pine forest. Four communities of shrub, softwood broad-leaved forest, softwood and hardwood broad-leaved forest, and hardwood broad-leaved forest represented different successional stages. A soil sample from a primary broad-leaved and Korean pine stand was the control. A sequential P fractionation scheme extracted empirically defined pools of P and path analysis used to partition the direct and indirect contribution of soil P fractions to available P. The results show that available P increased significantly with long-term succession, while both sodium bicarbonate-extractable P (NaHCO3-P) and sodium hydroxide-extractable P (NaOH-P) fractions were reduced in early successional stages and increased in late stages. Compared to the primary forest, concentrations of P fractions in the four stages significantly decreased except for HCl-P, indicating that soil P supplements over the long-term did not return to primary forest levels. The results of related analysis also showed that NaHCO3-Pi levels were significantly related to available phosphorus. According to the path analysis coefficient, NaHCO3-Pi exhibited the highest effect on available P among eight P fractions; the indirect effects of other P fractions via NaHCO3-Pi were larger than those with other P fractions. Overall, this study suggests that soil P bioavailability gradually improved during natural vegetation restoration on clear-cut sites mainly through the increase of NaHCO3-P, where phosphorous is immediately available, and subsequently available phosphorus NaOH-P.

Phosphorus status and saturation in soils that drain into the Peel Inlet and Harvey Estuary of Western Australia

The Peel–Harvey estuarine system in Western Australia's south-west is affected by poor water quality, algal blooms, and fish kills. Phosphorus (P) discharge from agricultural activities is the main source of poor water quality. The catchment’s soils are naturally infertile, but P application has increased P fertility. This paper draws on and undertakes a meta-analysis of 20 200 surface (0–10 cm) and profile (to 100 cm depth) soil samples collected in the period 1983–2018. Soil P content was high, with 70% of samples with Colwell P content in excess of agronomic requirements; Production is more likely limited by low soil pH(CaCl2) and low K (92% and 67% of paddocks respectively). Strong P stratification in the soil is evident, particularly topsoil; sandy soils are saturated to depth; and clay soils show signs of P saturation in the topsoil. Management of P in sandy soil near the estuary is a high priority as is P stratification in highly P retentive soil. Soil P stocks increased since clearing compared with uncleared soils (1221 kg ha–1 m–1 and 285–694 kg ha–1 m–1, respectively). Thirteen percent of samples had P content in excess of agronomic requirements in 1983, rising slowly to 69% in 2018. Landholder practices need to be analysed in detail to confirm if this accumulation occurs everywhere or is only confined to actively farmed land.

Phosphorus Reduces Negative Effects of Nitrogen Addition on Soil Microbial Communities and Functions.

Increased soil nitrogen (N) from atmospheric N deposition could change microbial communities and functions. However, the underlying mechanisms and whether soil phosphorus (P) status are responsible for these changes still have not been well explained. Here, we investigated the effects of N and P additions on soil bacterial and fungal communities and predicted their functional compositions in a temperate forest. We found that N addition significantly decreased soil bacterial diversity in the organic (O) horizon, but tended to increase bacterial diversity in the mineral (A) horizon soil. P addition alone did not significantly change soil bacterial diversity but mitigated the negative effect of N addition on bacterial diversity in the O horizon. Neither N addition nor P addition significantly influenced soil fungal diversity. Changes in soil microbial community composition under N and P additions were mainly due to the shifts in soil pH and NO3− contents. N addition can affect bacterial functional potentials, such as ureolysis, N fixation, respiration, decomposition of organic matter processes, and fungal guilds, such as pathogen, saprotroph, and mycorrhizal fungi, by which more C probably was lost in O horizon soil under increased N deposition. However, P addition can alleviate or switch the effects of increased N deposition on the microbial functional potentials in O horizon soil and may even be a benefit for more C sequestration in A horizon soil. Our results highlight the different responses of microorganisms to N and P additions between O and A horizons and provides an important insight for predicting the changes in forest C storage status under increasing N deposition in the future.

Lower nodule biomass with increased nitrogenase efficiency in Robinia pseudoacacia seedlings when grown under low soil phosphorus conditions

Symbiotic nitrogen (N) fixation is the largest non-anthropogenic N input to many terrestrial ecosystems. The energetic expense of symbiotic N fixation suggests soil phosphorus (P) availability may regulate symbiotic nitrogen fixation directly through nodule development and function, and/or indirectly through plant growth. Since P availability is heterogenous in the landscape, we sought to understand if symbiotic nitrogen fixation responds to both P availability and heterogeneity. To test how P availability affects symbiotic nitrogen fixation, we grew Robinia pseudoacacia seedlings under high (8.1 g P m−2) and low (0.2 g P m−2) conditions. Soil P heterogeneity was simulated by splitting roots into soil patches receiving P or no-P fertilizer. At the whole plant level, P availability limited seedling and nodule biomass. However, the low P treatment had higher nitrogenase efficiency (acetylene reduced (AR) g−1 nodule; a nodule efficiency proxy). High P seedlings had significantly more root and nodule biomass in the patches directly receiving P fertilizer, but patch proliferation was absent in the low P treatment. AR g−1 seedling did not differ between P treatments, suggesting P indirectly limited symbiotic nitrogen fixation through plant growth, rather than directly limiting symbiotic nitrogen fixation. This relatively consistent AR g−1 seedling across treatments demonstrates the ability of seedlings to respond to low P conditions with increased nitrogenase efficiency.

The Effect of Indigenous Phosphate-Solubilizing Bacteria on Quercus Brantii Seedlings Under Water Stress

ABSTRACT In the Mediterranean climate, plants, e.g., Quercus brantii Lindl, have evolved and adapted to bear up low soil-water and soil-phosphorus conditions. Quercus brantii Lindl. is a dominant tree species thorough Zagros Mediterranean forests. Phosphate-solubilizing bacteria (PSB) play crucial role in the plant growth enhancement by solubilizing insoluble soil-phosphate. In the present study, the effects of two indigenous PSB strains, e.g., Microbacterium sp. (M.) and Streptomyces sp. (S.) were individually and combined evaluated on growth and physiological traits of Quercus brantii. seedlings under different water stress treatments. Results showed that maximum P- solubilization rate was observed by M. strain. Results also revealed that water stress increased electrolyte leakage and reduced relative water content in all plant compartments as well as growth parameters. Two PSB strains individually and in combination significantly enhanced growth and physiological traits of seedlings under both irrigation treatments compared with the non-inoculated seedlings. The M. strain showed higher potential for increasing of root length, weight and RWC compare to other PSB strain. Finally, the results suggested that application of isolated indigenous PSBs in reforestation could help to cope with the drought conditions in semi-arid Mediterranean Zagros forests by increasing of root and improving of oak seedlings growth.

Effects of Ageratina adenophora Invasion on the Understory Community and Soil Phosphorus Characteristics of Different Forest Types in Southwest China

Understanding the influence of invasive species on community composition and ecosystem properties is necessary to maintain ecosystem functions. However, little is known about how understory plant communities and soil nutrients respond to invasion under different land cover types. Here, we investigated the effects of the invasive species Ageratina adenophora on the species and functional diversity of understory communities and on soil phosphorus (P) status in three forest types: CF, coniferous forest; MF, coniferous and broadleaf mixed forest; and EBF, evergreen broadleaf forest. We found that the species and functional diversity indices of the understory community significantly varied by forest type. Among the invaded plots, the greatest decrease in functional diversity (functional richness, functional divergence, and functional dispersion) and biotic homogenization were found in the CF rather than the MF or EBF. In addition, the invasion by A. adenophora significantly increased the soil NaHCO3-extractable inorganic P and organic P in the MF and EBF, respectively, while obviously decreasing the soil maximum P sorption capacity and maximum buffering capacity in the CF. However, the changes in the species and functional attributes of the understory communities were weakly associated with changes in the soil P status, probably because of the different response times to invasion in different forest types. The implication of these changes for ecosystem structure and function must be separately considered when predicting and managing invasion at a landscape scale.

Soil phosphorus availability modifies the relationship between AM fungal diversity and mycorrhizal benefits to maize in an agricultural soil

Arbuscular mycorrhizal (AM) fungi are very abundant in many agricultural soils and are important in increasing and maintaining the sustainability of agricultural systems. However, high soil fertility, especially high available soil phosphorus (P) status, often limits AM fungal development in intensively managed agricultural systems and results in the C-costs to the host plant outweighing any benefits from AM colonization. Some promising approaches can minimize negative effects on soil biota while providing the desired agricultural benefits (e.g. reduced soil tillage and organic amendments). However, the influence of these agricultural practices on the benefits of root mutualistic associations remains poorly understood. Here, we collected indigenous AM fungi from a long-term field experiment with different application rates of cow manure and conducted a pot experiment with different soil P levels. Using high throughput sequencing we demonstrate that increasing cow manure application changed the community composition of AM fungi and reduced community diversity in the field. Phosphorus addition in a bioassay experiment produced a mycorrhizal growth response (MGR) and the mycorrhizal P response (MPR) shifted from positive to negative, regardless of the origin of the inoculum. An increase in intraradical and extraradical AM fungal structures enhanced maize shoot biomass and P uptake under low (no P added) and moderate (20 mg P added kg−1 soil) P levels but the opposite occurred at a high P level (250 mg P added kg−1 soil). The MGR was higher in the treatment with higher community diversity at the moderate P level but there was no significant correlation at the other two P levels examined. We conclude that available soil P may regulate the abundance and diversity of AM fungi and their symbiotic function in intensive cropping systems. Our results indicate that managing the soil phosphorus level to favor a rich and diverse AM fungal community can enhance crop production and result in a more sustainable agricultural system.

Nitrogen and phosphorus influence Acacia saligna invasiveness in the fynbos biome

This study attempts to understand how invasive legumes such as Acacia saligna may compete with indigenous legumes such as Virgilia divaricata. The two species are trees with similar growth forms. We studied the competitive ability of invasive and indigenous seedlings under variations in soil phosphorus availability. South African fynbos vegetation is threatened by invasive Acacia. The indigenous tree legume, Virgilia, grows in similar phosphorus soil conditions as Acacia although there is a gap in the knowledge of their physiology. We investigated the utilization of different inorganic P sources by the invasive A. saligna and the native V. divaricata in the presence and absence of root nodules in each species. Plant performance in terms of photosynthesis and biomass production was also analysed. Plants were cultivated in silica sand supplied with Long Ashton nutrient solution, modified to contain either 50 μM P or 500 μM P applied as NaH2PO4·2H2O. Rate of growth was estimated as the increase in mass in plants harvested after 4 and 8 weeks of growth. After 4 weeks of growth, the seedlings of Virgilia grew quicker and produced more biomass than Acacia, under both phosphorus conditions. However, this was reversed after 8 weeks of growth, with Acacia out-competing Virgilia. Increased growth of the invasive legumes was achieved by relying on soil nitrogen under high phosphorus conditions and shifting to atmospheric sources under lower phosphorus levels. The strategies of altering photosynthetic carbon balance and nitrogen acquisition under varying soil phosphorus conditions potentially underpin the invasive potential of Acacia in fynbos soils.

Soil quality and phosphorus status after nine years of organic and conventional farming at two input levels in the Central Highlands of Kenya

Under temperate climate conditions, organic farming systems show improved soil quality compared to non-organic systems, whereas little long-term research on the impact of organic farming on soil quality has been conducted in sub-Saharan Africa. Within the system comparison (SysCom) project, two long-term field experiments were set up in 2007 in the sub-humid Central Highlands of Kenya to compare organic and conventional farming at two input levels (high input systems with recommended rates of nitrogen (N), phosphorus (P) and pesticides and with irrigation vs. rain-fed low input systems with low N, P and pesticides), with a similar design at both sites. The two sites differ mainly in their inherent soil properties and in the amount and distribution of rainfall. At the end of each three-year crop rotation period, we analyzed a set of chemical, biological and physical soil quality parameters in 0–20 cm soil depth. After nine years, microbial parameters seemed to have reached a steady state, whereas chemical parameters were still changing. Most soil quality parameters were highest under the high input organic farming system. The high input conventional system performed well in preserving several soil quality indicators, but a trend for acidification and the lack of soil carbon build-up raise concerns about the long-term sustainability of the system. Low input organic and conventional farming systems did not improve soil quality and even showed decreasing trends in several chemical parameters. Total and available P accumulated over time, especially in both high input systems, suggesting increasing risks of losses to the environment. Pronounced site effects revealed strong interactions with pedo-climatic conditions, with soil quality under high input organic farming improving to a greater extent at the site with more favorable conditions. Besides effects on soil quality, important criteria for sustainable input levels are thus the general availability of inputs, resulting nutrient input–output budgets as well as interactions of inputs with inherent soil properties.

Phosphorus Forms and Associated Properties along an Urban–Rural Gradient in Southern China

Urbanization is widely assumed to degrade soil ecosystem services, but the changes in the urban soil phosphorus (P) status due to urbanization and the associated environmental implications have rarely been studied. The objective of this study was to investigate the P forms and associated soil properties in urban soils. Thirty sites were selected along an urban–rural gradient in Nanchang, China, to examine the effects of urbanization on soil P fractions. Residual P and NaOH-extractable P (NaOH-Pi and NaOHPo) were the major P forms in the 0–30 cm of urban soils, comprising on average 37% and 43% of the total P pool, respectively, similar to the suburban and rural soils. Compared with non-urban soils, urban soil had higher contents of total P and P fractions (i.e., PH2O, PKCl, NaOH-Pi, PHCl, and residual P), as well as higher contents of related soil P-retentive properties, especially soil pH and Mehlich 3-extractable Ca and Mg. Phosphorus enrichment in the urban soils may become a source of aquatic pollution because the soil labile P content (the sum of PH2O and PKCl) was positively related to total P, PHCl, NaOH-Pi, and residual P, which implied that the labile P can be replenished by these P pools. This study increased the understanding of P stabilization characteristics (e.g., the specific P forms) of urban soils and has further implications for urban environmental management.

Phosphorus fractions and speciation in rural and urban calcareous soils in the semiarid region of Sulaimani city, Kurdistan, Iraq

The phosphorus (P) status of soils depends, among other influencing factors such as soil properties, on P content and availability. These vary with the P distribution among species of different mobility and chemical behavior. The P distribution, in turn, depends on the parent rock material and pedoclimate, and may differ between land uses. This study assesses the impact of urbanization on P contents, fractions and speciation in rural versus urban soils in the region of Sulaimani city, Iraq. Topsoil samples from calcareous soils experiencing different human impact intensity were taken in and around Sulaimani city, spanning rural soils from near-natural grassland, riverbanks and arable land, and urban soils from city parks, roadsides and industrial areas. Changes in P status and speciation were determined by combining P fractionation through sequential chemical extraction and P K-edge XANES spectroscopy. The sequence of P contents in the different fractions was (percentage of total P extracted): citrate bicarbonate-P (0.9%) < NaOH-P (1.7%) < NaHCO3-P (2.6%) ≤ citrate bicarbonate dithionate-P (3.8%) < residual P (36.2%) < HCl-P (54.8%). The dominance of stable Ca-phosphates (HCl-P) in all samples is typical for calcareous soils. The P distribution among fractions differed considerably in rural versus urban soils. Poor correlations of P fractions in urban soils with other soil parameters indicated that the P forms and contents were severely altered by human impact. P XANES analyses revealed that P speciation was dominated by P associated with Ca, especially in the urban area, and that irrigated arable land use increased the portions of P associated with pedogenic oxides. Soils of the semiarid regions in and around Sulaimani city exhibit a pattern of P fractions and species typical for calcareous soils. This pattern is clearly altered by human impacts such as agricultural land use and especially urban activities. It is concluded that the P inputs and turnover in urban soils are substantially decoupled from natural processes.

Soil physicochemical and biological controls on soil phosphorus status, availability and dynamics along a European continental transect

Soil physicochemical and biological controls on soil phosphorus status, availability and dynamics along a European continental transect

Using diffuse reflectance spectroscopy for assessing soil phosphorus status of an intensively cropped region

Phosphorus (P) is an essential plant nutrient and plays a vital role in achieving potential yields in rice-wheat sequence. conventional analytical techniques for assessing plant available P in soil are time consuming, relatively expensive and are not environment friendly. Diffuse reflectance spectroscopy particularly visible-near infrared (VIS-NIR) reflectance spectroscopy is an effective alternative means for rapid, nondestructive and eco-friendly assessment of available phosphorus and other soil properties. Geo-referenced surface soil (0–15 cm) samples (170) were collected from a rice-wheat field in Ludhiana district of Punjab state for performing both chemical (using Olsen method) and hyper-spectral analysis (350–2500 nm). A multivariate modeling technique, namely partial least square regression (PLSR) was employed to develop spectral model. Statistical diagnostics of coefficient of determination (R2), root mean square of error of prediction (RMSEP) and ratio of performance deviation (RPD) were used to evaluate the predictive performance of the developed spectral model. the R2, RMseP and RPd values were 0.42, 1.15 and 1.40, respectively for separate validation dataset of the PLsR model. however, the R2 and RMseP were better when the same set was used as validation set by using one-leave-out method. the RPd value suggested acceptable prediction accuracy of the spectral model. however, low R2 value and somewhat higher RMseP suggested exploring new modelling or data preprocessing techniques to enhance prediction accuracy.

Relationship between the 0.01 M CaCl2- and AL-soluble soil phosphorus contents

The traditional Hungarian method for determining soil phosphorus (P) status is ammonium-lactate acetic acid (AL) extraction. AL is an acidic solution (buffered at pH 3.75), which is also able to dissolve P reserves, so there is a need for extraction methods that also characterize the mobile P pool. 0.01 M CaCl2-P is considered to directly describe available P forms, because the dilute salt solution has more or less the same ionic strength as the average salt concentration in many soil solutions. The amount of AL-P may be two orders of magnitude greater than that of CaCl2-P. Previous studies suggested that the relationship between AL-P and CaCl2-P was influenced by soil parameters. Regression analysis between AL-P and CaCl2-P showed medium or strong correlations when using soils with homogeneous soil properties, while there was a weak correlation between them for soils with heterogeneous properties. The objective of this study was to increase the accuracy of the conversion between AL-P and CaCl2-P, by constructing universal equations that also take soil properties into consideration. The AL-P and CaCl2-P contents were measured in arable soils (n=622) originating from the Hungarian Soil Information and Monitoring System (SIMS). These soils covered a wide range of soil properties. A weak correlation was found between AL-P and CaCl2-P in SIMS soils. The amounts and ratio of AL-P and CaCl2-P depended on soil properties such as CaCO3 content and texture. The ratio of AL-P to CaCl2-P changed from 37 in noncalcareous soils to 141 on highly calcareous soils. CaCl2-P decreased as a function of KA (plasticity index according to Arany), which is related to the clay content, while the highest AL-P content was found on loam soils, probably due to the fact that a high proportion of them were calcareous. The relationships between AL-P, CaCl2-P and soil properties in the SIMS dataset were evaluated using multiple linear regression analysis. In order to select the best model the Akaike Information Criterion (AIC) was used to compare different models. The soil factors included in the models were pHKCl, humus and CaCO3 content to describe AL-P, and KA, CaCO3 content and pHKCl to describe CaCl2-P. AL-P was directly proportional to pHKCl, humus and CaCO3 content, while CaCl2-P was inversely proportional to KA, CaCO3 content and pHKCl. The explanatory power of the models increased when soil properties were included. The percentage of the explained variance in the AL-P and CaCl2-P regression models was 56 and 51%, so the accuracy of the conversion between the two extraction methods was still not satisfactory and it does not seem to be possible to prepare a universally applicable equation. Further research is needed to obtain different regression equations for soils with different soil properties, and CaCl2-P should also be calibrated in long-term P fertilization trials.

Mechanisms by which organic fertilizer and effective microbes mitigate peanut continuous cropping yield constraints in a red soil of south China

Red soils are acid soils which occupy about one fifth of the total area of tropical and subtropical soils in China. Peanut (Arachis hypogaea L.) is regarded as the main oil and cash crop in the red soil region. However, yields of peanut have gradually but significantly declined under continuous cropping. We conducted a field experiment in Jiangxi province, south China from 1996 to investigate the mitigation of the peanut continuous cropping constraint. Three types of fertilizer (chemical, organic, and organic fertilizer with effective microbes) were applied in the field. After 20 years of cropping the continuous cropping constraint was found to be more severe where chemical fertilizers were applied and was mitigated where the fields were amended with organic fertilizer or organic fertilizer with effective microbes. Soil properties and the rhizosphere bacterial community structure were determined in 2016. Long-term application (20 years) of organic fertilizer increased the plant available phosphorus in the rhizosphere soil. Phosphorus is known to be one of the most limiting factors for peanut growth in red soils and peanut yield was promoted as the soil phosphorus status increased. Organic fertilizer and effective microbes also optimized the rhizobacteria of peanut to mitigate the continuous cropping obstacle. The bacterial wilt pathogen (Ralstonia) decreased in abundance in the rhizosphere and bacterial wilt disease of peanut declined significantly. Moreover, beneficial bacteria in the rhizosphere capable of promoting peanut growth increased in abundance.

Non-structural carbon, nitrogen, and phosphorus between black locust and chinese pine plantations along a precipitation gradient on the Loess Plateau, China

No soil nutrient differences between two plantations. In contrast to NSC, N and P concentrations were greater in black locust than in Chinese pine. NSC negatively, N and P positively related to precipitation for both plantations. Precipitation is a key environmental factor affecting carbon (C), nitrogen (N), and phosphorus (P) status of plants and soils, especially in water-limited regions. However, there are potential differences among species in their sensitivity to C, N, and P in relation to variation in precipitation. We presented paired measurements of non-structural carbon (NSC), N, and P concentrations in plantations of N-fixing black locust (Robinia pseudoacacia L.) and coniferous Chinese pine (Pinus tabulaeformis Carriere) along a mean annual precipitation gradient on the Loess Plateau, China. The results showed that soil nutrients positively related to precipitation, but their differences between two plantations were not clearly visible. NSC concentrations of tree tissues were significantly greater in Chinese pine than in black locust. In contrast, the N and P concentrations and the N:P ratios were significantly greater in black locust than in Chinese pine. Leaves contained the highest N and P concentrations, whereas coarse roots contained the highest NSC concentrations. The lowest concentrations of NSC were in the stem wood. NSC concentrations were negatively related to precipitation, while N and P concentrations were positively related to precipitation for both tree plantations. The constant leaf N:P ratios indicated that the growth of Chinese pine was limited by the soil N supply, whereas black locust was limited by P. These results indicate that inherent physiological and biological processes differ with tree species, and when coupled with environmental conditions, influence the variations of C, N, and P in plant tissues to adaptation and resilience under drought stress.

Response of regional agricultural soil phosphorus status to net anthropogenic phosphorus input (NAPI) determined by soil pH value and organic matter content in subtropical China

Exploring the relationship between net anthropogenic phosphorus input (NAPI) and soil available P (SAP) content could inform applied issues related to environmental quality and agronomic productivity and increase our knowledge of element biogeochemical cycles. Here, the NAPI was estimated and the SAP content determined in eight counties in subtropical China from 1980 to 2010. It is suggested that the NAPI ranging 318-924 km−2 yr−1 in 1980 had increased substantially to 865–3601 km−2 yr−1 in 2010 across the eight counties, in which the P fertilizer application was estimated to represent the largest individual source of NAPI, accounting for an average of 36.1–74.6% of the NAPI. The NAPI in agricultural land (NAPIa) was the largest component of the NAPI, and 60.7–77.1% of the NAPIa accumulated in the upper 20 cm layer of agricultural soils, which significantly increased soil total–P (TP) and SAP contents. The increases in SAP, resulting from 10,000 kg P km−2 of the NAPIa (IOPNAPI), were estimated to be 1.61–4.36 mg P kg−1 in the counties. Both the correlation and variation partitioning analyses (VPAs) suggested that the soil pH and organic matter content (SOM) were the most important factors influencing the variations of IOPNAPI (determination coefficient: 72.5%). Therefore, the contribution of soil pH and SOM should be considered in enriching soil SAP levels and implementing optimal P management strategies to improving the agronomic effectiveness of P fertilization and further reduce the environmental risk of P loss in subtropical region.