Effect of N and P addition on soil organic C potential mineralization in forest soils in South China

Atmospheric nitrogen deposition is at a high level in some forests of South China. The effects of addition of exogenous N and P on soil organic carbon mineralization were studied to address: (1) if the atmospheric N deposition promotes soil C storage through decreasing mineralization; (2) if the soil available P is a limitation to organic carbon mineralization. Soils (0–10 cm) was sampled from monsoon evergreen broad-leaved forest (MEBF), coniferous and broad-leaved mixed forest (CBMF), and Pinus massoniana...

Positive effects of biochar application and Rhizophagus irregularis inoculation on mycorrhizal colonization,rice seedlings and phosphorus cycling in paddy soils

Phosphorus(P)is an essential element for plant growth but is often limiting in ecosystems;therefore,improving the P fertilizer use efficiency is important.Biochar and arbuscular mycorrhizal fungi(AMF)may enhance P cycling in paddy soils that contain high content of total P but low content of available P(AP).In this study,the effects of biochar addition and Rhizophagus irregularis inoculation on the organic and inorganic P contents and phosphatase activities in paddy soils,rice seedling growth,and AMF colonization were investigated.Compared with no biochar addition,biochar addition enhanced the percentage of spore germination at day 7,hyphal length,most probable number,and mycorrhizal colonization rate of R.irregularis by 32%,662%,70%,and 28%on average,respectively.Biochar and R.irregularis altered soil P cycling and availability.Biochar and R.irregularis,either individually or in combination,increased soil AP content by 2%–48%.Rice seedlings treated with biochar and R.irregularis produced greater biomass,improved root morphology,and increased nutrient uptake compared with those of the control without biochar and R.irregularis.The results suggest that combined application of biochar and R.irregularis is beneficial to rice cultivation in paddy soils with high content of total P but low content of AP.

Soil and microbial C:N:P stoichiometries play vital roles in regulating P transformation in agricultural ecosystems:A review

Stoichiometry plays a crucial role in biogeochemical cycles and can modulate soil nutrient availability and functions. In agricultural ecosystems,phosphorus(P) fertilizers(organic or chemical) are often applied to achieve high crop yields. However, P is readily fixed by soil particles, leading to low P use efficiency. Therefore, understanding the role of carbon:nitrogen:P stoichiometries of soil and microorganisms in soil P transformation is of great significance for P management in agriculture. This paper provides a comprehensive review of the recent research on stoichiometry effect on soil P transformation in agricultural ecosystems. Soil microorganisms play an important role in the transformation of soil non-labile inorganic P to microbial biomass P by regulating microbial biomass stoichiometry. They also mobilize soil unavailable organic P into available P by changing ecoenzyme stoichiometry. Organic materials, such as manure and straw, play an important role in promoting the transformation of insoluble P into available P as well. Additionally, periphytic biofilms can reduce P loss from rice field ecosystems. Agricultural stoichiometries are different from those of natural ecosystems and thereby should receive more attention due to the influences of anthropogenic factors. Therefore, it is necessary to conduct further stoichiometry research on the soil biochemical mechanisms underlying P transformation in agricultural ecosystems. In conclusion, understanding stoichiometry impact on soil P transformation is crucial for P management in agricultural ecosystems.

Increased phosphorus availability to corn resulting from the simultaneous applications of phosphate rock, calcareous rock, and biochar to an acid sandy soil

Phosphorus(P)deficiency is one of the main constraints on crop production in Arenosols(acid sandy soil).The high cost of P fertilizers may represent an insurmountable obstacle in many poor countries,leaving the exploitation of their own calcareous and phosphate rocks as the only low-cost and long-term alternative.Biochar is suggested to have positive effects on soil properties;however,there is no published research on the synergistic effects of biochar and rocky materials in modifying soil properties.The aim of this study was to investigate the chemical and biochemical responses of an acid Arenosol treated with phosphate rock(PR),calcareous rock(CR),and biochar(BC),and the implications for corn yield.A soil from Marracuene District,Mozambique was used,where corn was grown for 90 d with the soil treated with:no addition(control),water-soluble zinc phosphite fertilizer(WSP),PR,WSP+CR,WSP+BC,WSP+CR+BC,PR+BC,and PR+CR+BC.Biochar was produced by pyrolysis of babycorn peels for 4 h at 450?C and applied at 11 g kg-1.The soil pHH2 Oincreased from about 4.54 in the control to 7.38 in the PR+CR+BC treatment.Easily oxidizable organic carbon,cation exchange capacity,and available P were higher in the treatments containing BC than in the control.The treatments containing CR and/or BC led to the highest activities of alkaline phosphomonoesterase,phosphodiesterase,andα-glucosidase,which increased P availability and gave the greatest biomass and yields.We suggest that biochar provides additional soluble P and supplies adsorption sites for phosphate,preventing its evolution to unavailable forms.Thus,PR applied together with BC contributed to an 840%yield increase compared to the control.The treatments containing WSP and BC facilitated phosphite oxidation to phosphate and increased crop yield.

Biochar and soil properties limit the phytoavailability of lead and cadmium by Brassica chinensis L.in contaminated soils

The current study investigated the effect of biochars derived from cinnamomum woodchip,garden waste and mulberry woodchip on soil phytoavailable lead(Pb),cadmium(Cd)pools,and their uptake by Chinese cabbage(Brassica chinensis L.).The biochars were produced at 450℃of pyrolysis temperature.The contaminated soils were collected from Yunfu(clas-sified as Udept),Jiyuan(Ustalf)and Shaoguan(Udult)cities in China at the depth of 0-20 cm and amended with biochars at the rate of 3%w/w.After mixing the soil with biochar for 14 days,the Chinese cabbage was planted in the amended soils.Then,it was harvested on the 48th day after sowing period.In Udult soil,Chinese cabbage died 18 days after sowing period in control and soils amended with cinnamomum and mulberry biochars.Although only plants grown with the garden waste biochar treatment survived in Udult soil,amendment of garden waste or mulberry biochars at 3%w/w(450℃)to Udult soil significantly increased(4.95-6.25)soil pH compared to other biochar treatments.In Udept and Ustalf soils,the application of garden waste and mulberry biochars significantly improved plant biomass compared to control,albeit it was dependent on both biochar and soil properties.Garden waste biochar significantly decreased soil Cd phytoavailable concentration by 26%in the Udult soil,while a decrease of soil Cd phytoavailable concentration by 16%and 9%was observed in Ustalf and Udept soils,respectively.The available phosphorus in biochar and soil pH were important factors controlling toxic metal phytouptake by the plant.Thus,the amendment of soil with biochar at 3%can effectively reduce the mobility of Cd and Pb in soil and plant uptake.However,biochar and soil properties should be well-known before being used for soil toxic metal immobilization.

Nitrogen addition mediates the response of foliar stoichiometry to phosphorus addition: a meta-analysis

Background:Changes in foliar nitrogen(N)and phosphorus(P)stoichiometry play important roles in predicting the efects of global change on ecosystem structure and function.However,there is substantial debate on the efects of P addition on foliar N and P stoichiometry,particularly under diferent levels of N addition.Thus,we conducted a global meta-analysis to investigate how N addition alters the efects of P addition on foliar N and P stoichiometry across different rates and durations of P addition and plant growth types based on more than 1150 observations.Results:We found that P addition without N addition increased foliar N concentrations,whereas P addition with N addition had no efect.The positive efects of P addition on foliar P concentrations were greater without N addition than with N addition.Additionally,the efects of P addition on foliar N,P and N:P ratios varied with the rate and duration of P addition.In particular,short-term or low-dose P addition with and without N addition increased foliar N concentration,and the positive efects of short-term or low-dose P addition on foliar P concentrations were greater without N addition than with N addition.The responses of foliar N and P stoichiometry of evergreen plants to P addition were greater without N addition than with N addition.Moreover,regardless of N addition,soil P availability was more efective than P resorption efciency in predicting the changes in foliar N and P stoichiometry in response to P addition.Conclusions:Our results highlight that increasing N deposition might alter the response of foliar N and P stoichiometry to P addition and demonstrate the important efect of the experimental environment on the results.These results advance our understanding of the response of plant nutrient use efciency to P addition with increasing N deposition.