The co-utilization of green manure (GM) and rice straw (RS) in paddy fields has been widely applied as an effective practice in southern China.However,its effects on soil aggregate and soil organic carbon (SOC) stabil...The co-utilization of green manure (GM) and rice straw (RS) in paddy fields has been widely applied as an effective practice in southern China.However,its effects on soil aggregate and soil organic carbon (SOC) stability remain unclear.In the present study,the effect of GM,RS,and co-utilization of GM and RS on particle size distribution of soil aggregates and SOC density fractions were measured in a field experiment.The experiment included six treatments,i.e.,winter fallow (WF) without RS return (Ctrl),WF with 50%RS return (1/2RS),WF with 100%RS return (RS),GM without RS return (GM),GM with 50%RS return (GM1/2RS) and GM with 100%RS return (GMRS).The results showed that the proportion of small macro-aggregates (0.25–2 mm) and the mean weight diameter (MWD) of aggregates in the GMRS treatment was greater (by 18.9 and 3.41%,respectively) than in the RS treatment,while the proportion of silt+clay particles (<0.053 mm) was lower (by 14.4%).The concentration of SOC in microaggregates (0.053–0.25 mm)and silt+clay particles was higher in the GMRS treatment than in GM and RS treatments individually.The concentration and proportion of free light organic carbon (fLOC) in aggregates of various particle sizes and bulk soil was greater in the GMRS treatment than the RS treatment,whereas the concentration and proportion of mineral-associated organic carbon in small macroaggregates,microaggregates,and bulk was lower in the GMRS treatment than in the RS treatment.The proportion of intra-aggregate particulate organic carbon (iPOC) was greater in the GMRS treatment than in GM treatment.The GMRS treatment had strong positive effects on iPOC in small macroaggregates,suggesting that SOC was transferred from fLOC to iPOC.In conclusion,co-utilizing green manure and rice straw cultivated the SOC pool by increasing the concentration of fLOC and improved soil carbon stability by promoting the sequestration of organic carbon in iPOC as a form of physical protection.展开更多
Increasing K+ adsorption can be an effective alternative in building an available K pool in soils to optimize crop recovery and minimize losses into the environment. We hypothesized that long-term fertilization might ...Increasing K+ adsorption can be an effective alternative in building an available K pool in soils to optimize crop recovery and minimize losses into the environment. We hypothesized that long-term fertilization might change K+ adsorption because of changes in the chemical and mineralogical properties of a rice (Oryza sativa L.). The aims of this study were (i) to determine clay minerals in paddy soil clay size fractions using X-ray diffraction methods and a numerical diagram-decomposition method; (ii) to measure K+ adsorption isotherms before and after H 2 O 2 oxidation of organic matter, and (iii) to investigate whether K+ adsorption is correlated with changes in soil chemical and mineral properties. The 30-yr long-term fertilization treatments caused little change in soil organic C (SOC) but a large variation in soil mineral composition. The whole-clay fraction (<5 μm) corresponded more to the fertilization treatment than the fine-clay fraction (<1 μm) in terms of percentage of illite peak area. The total percentage of vermiculite-chlorite peak area was significantly negatively correlated with the total percentage of illite peak area in the <5 μm soil particles (R=-0.946, P<0.0006). Different fertilization treatments gave significantly different results in K+ adsorption. The SOC oxidation test showed positive effects of SOC on K+ adsorption at lower K+ concentration ( 120 mg L-1) and negative effects at higher K+ concentration (240 mg L-1). The K+ adsorption by soil clay minerals after SOC oxidization accounted for 60-158% of that by unoxidized soils, suggesting a more important role of soil minerals than SOC on K+ adsorption. The K+ adsorption potential was significantly correlated to the amount of poorly crystallized illite present (R=0.879, P=0.012). The availability of adsorbed K+ for plant growth needs further study.展开更多
The double-rice cropping system is a very important intensive cropping system for food security in China. There have been few studies of the sustainability of yield and accumulation of soil organic carbon (SOC) in the...The double-rice cropping system is a very important intensive cropping system for food security in China. There have been few studies of the sustainability of yield and accumulation of soil organic carbon (SOC) in the double-rice cropping system following a partial substitution of chemical fertilizer by Chinese milk vetch (Mv). We conducted a 10-year (2008–2017) field experiment in Nan County, South-Central China, to examine the double-rice productivity and SOC accumulation in a paddy soil in response to different fertilization levels and Mv application (22.5 Mg ha^–1). Fertilizer and Mv were applied both individually and in combination (sole chemical fertilizers, Mv plus 100, 80, 60, 40, and 0% of the recommended dose of chemical fertilizers, labeled as F100, MF100, MF80, MF60, MF40, and MF0, respectively). It was found that the grain yields of double-rice crop in treatments receiving Mv were reduced when the dose of chemical fertilizer was reduced, while the change in SOC stock displayed a double peak curve. The MF100 produced the highest double-rice yield and SOC stock, with the value higher by 13.5 and 26.8% than that in the F100. However, the grain yields increased in the MF80 (by 8.4% compared to the F100), while the SOC stock only increased by 8.4%. Analogous to the change of grain yield, the sustainable yield index (SYI) of double rice were improved significantly in the MF100 and MF80 compared to the F100, while there was a slight increase in the MF60 and MF40. After a certain amount of Mv input (22.5 Mg ha^–1), the carbon sequestration rate was affected by the nutrient input due to the stimulation of microbial biomass. Compared with the MF0, the MF100 and MF40 resulted in a dramatically higher carbon sequestration rate (with the value higher by 71.6 and 70.1%), whereas the MF80 induced a lower carbon sequestration rate with the value lower by 70.1% compared to the MF0. Based on the above results we suggested that Mv could partially replace chemical fertilizers (e.g., 40–60%) to improve or maintain the productivity and sustainability of the double-rice cropping system in South-Central China.展开更多
In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrie...In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregateassociated carbon(C) and nitrogen(N). The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay(classified as Fe-Accumuli-Stagnic Anthrosols) with continuous early and late rice. In 2009, soil samples were collected(0-15 cm depth) from the field treatment plots and separated into water-stable aggregates of different sizes(i.e., >5, 2-5, 1-2, 0.5-1, 0.25-0.5 and <0.25 mm) by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.展开更多
A field experiment of organic manure,passivator and their complex was conducted to study the soil Cd bioavailability in the Cd polluted paddy soil. The results showed that the rice yield increased with the application...A field experiment of organic manure,passivator and their complex was conducted to study the soil Cd bioavailability in the Cd polluted paddy soil. The results showed that the rice yield increased with the applications of organic manure,passivator and their complex,especially,the rice yields of applying 3 000 and 6 000 kg / hm2 of organic manure increased significantly by 18. 6%( P < 0. 05) and 20. 9%( P < 0. 05) because of the increase of rice economic coefficient. There had no significant change of the soil p H values and the soil available Cd contents,but the Cd distribution ratios in rice were lowered by applying organic manure,and the Cd contents of rice applying 3 000 and 6 000 kg / hm2 of organic manure dropped by 14. 3%( P > 0. 05) and 21. 4%( P > 0. 05) compared with chemical fertilizer treatment,respectively. But applying with passivator and passivator fertilized with 3 000 and 6 000 kg / hm2 of organic manure,the soil p H values increased and the soil available Cd contents decreased significantly,so that to restrain the rice's Cd absorption and accumulation. The rice Cd contents lowered by 28. 6%( P < 0. 05),28. 6%( P < 0. 05)and 42.9%( P<0.05),the stem Cd contents lowered by 8. 9%( P > 0. 05),29. 7%( P < 0. 05) and 43. 6%( P < 0. 05),and the leaf Cd contents decreased by 18. 8%( P < 0. 05),25. 0%( P < 0. 05) and 25. 0%( P < 0. 05),respectively. It enhanced the inactivate effect of passivator significantly when fertilized with organic manure.展开更多
A pot experiment combined with15N isotope techniques was conducted to evaluate effects of the varying rates of urea-N fertilizer application on yields,quality,and nitrogen use efficiency (NUE) of pakchoi cabbage (Bras...A pot experiment combined with15N isotope techniques was conducted to evaluate effects of the varying rates of urea-N fertilizer application on yields,quality,and nitrogen use efficiency (NUE) of pakchoi cabbage (Brassica chinensis L.) and asparagus lettuce (Lactuca saiva L.).15N-labbled urea (5.3515N atom %) was added to pots with 6.5 kg soil of 0.14,0.18,0.21,0.25,and 0.29 g N/kg soil,and applied in two splits:60 percent as basal dressing in the mixture and 40 percent as topdressing.The fresh yields of two vegetable species increased with the increasing input of urea-N,but there was a significant quadratic relationship between the dose of urea-N fertilizer application and the fresh yields.When the dosage of urea-N fertilizer reached a certain value,nitrate readily accumulated in the two kinds of plants due to the decrease in NR activity; furthermore,there was a linear negative correlation between nitrate content and NR activity.With the increasing input of urea-N,ascorbic acid and soluble sugar initially increased,declined after a while,and crude fiber rapidly decreased too.Total absorbed N (TAN),N derived from fertilizer (Ndff),and N derived from soil (Ndfs) increased,and the ratio of Ndff and TAN also increased,but the ratio of Ndfs and TAN as well as NUE of urea-N fertilizer decreased with the increasing input of urea-N.These results suggested that the increasing application of labeled N fertilizer led to the increase in unlabeled N (namely,Ndfs) presumably due to "added nitrogen interaction" (ANI),the decease in NUE of urea-N fertilizer may be due to excess fertilization beyond the levels of plant requirements and the ANI,and the decrease in the two vegetable yields with the increasing addition of urea-N possibly because the excess accumulation of nitrate reached a toxic level.展开更多
Soil physical properties are important indicators of the potential for agricultural production.Our objective was to evaluate the effects of long-term inputs of green manures on physical properties of a reddish paddy s...Soil physical properties are important indicators of the potential for agricultural production.Our objective was to evaluate the effects of long-term inputs of green manures on physical properties of a reddish paddy soil(Fe-Typic Hapli-Stagnic Anthrosols) under a double cropping system.The common cropping pattern before the study was early-late rice-fallow(winter).The field treatments included rice-rice-fallow(R-R-WF),rice-rice-rape(R-R-RP),rice-rice-Chinese milk vetch(RR-MV),and rice-rice-ryegrass(R-R-RG).The rape,Chinese milk vetch and ryegrass were all incorporated as green manures 15 d before early rice transplanting during the following year.The soil bulk density in all green manure treatments was significantly reduced compared with the winter fallow treatment.Soil porosity with green manure applications was significantly higher than that under the winter fallow.The green manure treatments had higher 0.25-5 mm water stable aggregates and aggregates stabilities in the plow layer(0-15 cm depth) compared with the fallow treatment.The mean weight diameter(MWD) and normalized mean weight diameter(NMWD) of aggregates in the green manure treatment were larger than that with the winter fallow.Soil given green manure retained both a higher water holding capacity in the plow layer soil,and a larger volume of moisture at all matric potentials(-10,-33 and-100 kPa).We conclude that the management of double-rice fields in southern central China should be encouraged to use green manures along with chemical fertilizers to increase SOC content,improve soil physical properties and soil fertility.展开更多
Improved utilization of rice(Oryza sativa L.)straw and Chinese milk vetch(Astragalus sinicus L.,vetch)has positive effects on rice production.So far,few studies have investigated the productivity of vetch under differ...Improved utilization of rice(Oryza sativa L.)straw and Chinese milk vetch(Astragalus sinicus L.,vetch)has positive effects on rice production.So far,few studies have investigated the productivity of vetch under different residue management practices in double-rice cropping system.The effects of rice straw on the growth and nutrient accumulation of vetch across seven years(2011–2017)and the subsequent effects of rice straw and vetch on two succeeding rice crops in a vetch–rice–rice cropping system,with the vetch established by relay cropping,were examined.The seven-year double-rice experiment consisted of the following treatments:(1)100%chemical fertilizer(F-F100);(2)only vetch without chemical fertilizer(M-Con);(3)80%chemical fertilizer plus vetch plus a low-cutting height(low-retained stubble)with the removal of straw(M-F80);(4)80%chemical fertilizer plus vetch plus a low-cutting height with the retention of straw(M-F80-LR);(5)80%chemical fertilizer plus vetch plus a high-cutting height(high-retained stubble)with the retention of straw(M-F80-HR);and(6)no fertilizer(F-Con).The yields of the two rice crops after vetch were not affected by either the cutting height of stubble with retention of straw or by the management of straw(retention vs.removal)with low-cutting height of stubble.The yields of the two rice crops after vetch were significantly higher for M-F80-HR than for M-F80-LR,but the relative contributions of the high-cutting height and straw retention to the higher rice yield could not be determined in this study.The yield stability of the double-rice grain in M-F80-HR was also increased,as determined by a sustainable yield index.Significant increases in vetch biomass and nutrient uptake were observed in the fertilized treatments during the rice season compared with the unfertilized treatments.In M-F80-HR plots,improvements in the growing environment of the vetch by conserving soil water content were associated with the highest vetch biomass,nutrient uptake,and yield stability of vetch biomass.These increased nutrient inputs partially replaced the demand for chemical fertilizer and stimulated the rice yields.It can be concluded that retaining higher-cutting stubble residues with straw retention could be the best straw management practice for increasing the vetch biomass and nutrient use efficiency,thereby allowing utilization of high-cutting height with retention of straw and vetch to improve the stability of rice productivity in a double-rice cropping system.展开更多
A two-year lysimeter study was conducted to study the effects of different fertilizers and soils on nitrogen leaching loss in a double rice cropping system by considering three major types of paddy soils from the Dong...A two-year lysimeter study was conducted to study the effects of different fertilizers and soils on nitrogen leaching loss in a double rice cropping system by considering three major types of paddy soils from the Dongting Lake area. The results showed that N concentration in the leachate did not differ significantly among the treatments of urea, controlled release N fertilizer and pig manure and that all these fertilizers produced higher total nitrogen (TN) concentrations in the leachate compared to the case where no fertilizer was applied. The TN leaching loss following urea treatment accounted for 2.28%, 0.66%, and 1.50% of the amount of N applied in the alluvial sandy loamy paddy soil (ASL), purple calcareous clayey paddy soil (PCC), and reddish-yellow loamy paddy soil (RYL), respectively. Higher TN loss was found to be correlated with the increased leachate volume in ASL compared with RYL, and the lowest TN loss was observed in the PCC, in which the lowest leachate volume and TN concentration were observed. Organic N and NH4+ -N were the major forms of N depleted through leachate, accounting for 56.8% and 39.7% of TN losses, respectively. Accordingly, soil-specific fertilization regimens are recommended; in particular, the maximum amount of fertilizer should be optimized for sandy soils with a high infiltration rate. To avoid a high N leaching loss from rice fields, organic N fertilizers such as urea or coated urea should primarily be used for surface topdressing or shallow-layer application and not for deep-layer application.展开更多
In China’s major rice(Oryza sativa L.)production regions,the traditional fertilization modes are challenged by the continued decrease in manure and increase in mineral fertilizer.However,limited information exists on...In China’s major rice(Oryza sativa L.)production regions,the traditional fertilization modes are challenged by the continued decrease in manure and increase in mineral fertilizer.However,limited information exists on the influences of long-term fertilizer management on soil organic carbon(SOC)and soil physical properties under the intensive rice production system in southern China.The objective of this study was to characterize the changes of soil physical properties as related to mineral fertilizer,crop residues,and manure application based on a long-term field experiment.The experiment,initiated in 1986,has five treatments:unfertilized,mineral fertilizer alone,rice residues plus mineral fertilizer,low manure rate plus mineral fertilizer,and high manure rate plus mineral fertilizer.The cropping system consists of barley(Hordaum vulgare L.),early rice,and late rice,three crops in a year.In May 2006,after barley harvest,soil samples were collected from the 0~10 cm and 10~20 cm layers to determine SOC concentration,aggregate size distribution,bulk density(rb),saturated hydraulic conductivity(Ks),and soil water characteristic curves(SWCC).The results indicated that manure significantly reducedrb,increased SOC concentration,soil aggregation,Ks,transmission and storage porosity,as well as water retention capacity.Combined application of crop residue and mineral fertilizer also improved soil physical properties,but the improvement by mineral fertilizer alone was limited.Correlation analysis demonstrated that S,the slope of the SWCC at its inflection point,was closely associated with the selected physical parameters,suggesting S was an effective parameter for soil physical quality evaluation.Nevertheless,in applying the S-theory,a unified approach to define the residual water content should be considered.展开更多
Returning crop straw into the soil is an important practice to balance biogenic and bioavailable silicon(Si)pool in paddy,which is crucial for the healthy growth of rice.However,owing to little knowledge about soil mi...Returning crop straw into the soil is an important practice to balance biogenic and bioavailable silicon(Si)pool in paddy,which is crucial for the healthy growth of rice.However,owing to little knowledge about soil microbial communities responsible for straw degradation,how straw return affects Si bioavailability,its uptake,and rice yield remains elusive.Herein,we investigate the change of soil Si fractions and microbial community in a 39-year-old paddy field amended by a long-term straw return.Results show that rice straw return significantly increased soil bioavailable Si and rice yield from 29.9%to 61.6%and from 14.5%to 23.6%,respectively,when compared to NPK fertilization alone.Straw return significantly altered soil microbial community abundance.Acidobacteria was positively and significantly related to amorphous Si,while Rokubacteria at phylum level,Deltaproteobacteria,and Holophagae at class level was negatively and significantly related to organic matter adsorbed and Fe/Mn-oxide-combined Si in soils.Redundancy analysis of their correlations further demonstrated that Si status significantly explained 12%of soil bacterial community variation.These findings suggest that soil bacteria community and diversity interact with Si mobility by altering its transformation,thus resulting in the balance of various nutrient sources to drive biological Si cycle in agroecosystem.展开更多
Tillage practices can potentially afect soil organic carbon (SOC) accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-c...Tillage practices can potentially afect soil organic carbon (SOC) accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-cropped rice (Oryza sativa L.) field in Hunan Province of China. Three tillage treatments, no-till (NT), conventional plow tillage(PT), and rotary tillage(RT), were laid in a randomized complete block design. Concentrations of SOC and bulk density(BD) of the 0-80 cm soil layer were measured, and SOC stocks of the 0-20 and 0-80 cm soil layers were calculated on an equivalent soil mass(ESM) basis and fixed depth (FD) basis.Soil carbon budget(SCB) under diferent tillage systems were assessed on the basis of emissions of methane(CH4) and CO2 and the amount of carbon (C) removed by the rice harvest. After four years of experiment, the NT treatment sequestrated more SOC than the other treatments. The SOC stocks in the 0-80 cm layer under NT (on an ESM basis) was as high as 129.32 Mg C ha 1,significantly higher than those under PT and RT (P < 0.05). The order of SOC stocks in the 0-80 cm soil layer was NT > PT > RT,and the same order was observed for SCB; however, in the 0-20 cm soil layer, the RT treatment had a higher SOC stock than the PT treatment. Therefore, when comparing SOC stocks, only considering the top 20 cm of soil would lead to an incomplete evaluation for the tillage-induced efects on SOC stocks and SOC sequestrated in the subsoil layers should also be taken into consideration. The estimation of SOC stocks using the ESM instead of FD method would better reflect the actual changes in SOC stocks in the paddy filed, as the FD method amplified the tillage efects on SOC stocks. This study also indicated that NT plus straw retention on the soil surface was a viable option to increase SOC stocks in paddy soils.展开更多
As an aliphatic amino acid,cysteine(CYS)is diffuse in the living cells of plants and animals.However,little is known of its role in the reactivity of nano-sized zero-valent iron(NZVI)in the degradation of pollutants.T...As an aliphatic amino acid,cysteine(CYS)is diffuse in the living cells of plants and animals.However,little is known of its role in the reactivity of nano-sized zero-valent iron(NZVI)in the degradation of pollutants.This study shows that the introduction of CYS to the NZVI system can help improve the efficiency of reduction,with 30%more efficient degradation and a reaction rate constant nine times higher when nitrobenzene(NB)is used as probe compound.The rates of degradation of NB were positively correlated with the range of concentrations of CYS from 0 to 10 mmol/L.The introduction of CYS increased the maximum concentration of Fe(Ⅲ)by 12 times and that of Fe(II)by four times in this system.A comparison of systems featuring only CYS or Fe(Ⅱ)showed that the direct reduction of NB was not the main factor influencing its CYS-stimulated removal.The reduction in the concentration of CYS was accompanied by the generation of cystine(CY,the oxidized form of cysteine),and both eventually became stable.The introduction of CY also enhanced NB degradation due to NZVI,accompanied by the regeneration of CYS.This supports the claim that CYS can accelerate electron transfer from NZVI to NB,thus enhancing the efficiency of degradation of NB.展开更多
基金funded by the National Key Research and Development Program of China (2021YFD1700200)the earmarked fund for China Agriculture Reserch System(CARS-22)the Natural Science Foundation of Jiangsu Province,China (BK20200112)。
文摘The co-utilization of green manure (GM) and rice straw (RS) in paddy fields has been widely applied as an effective practice in southern China.However,its effects on soil aggregate and soil organic carbon (SOC) stability remain unclear.In the present study,the effect of GM,RS,and co-utilization of GM and RS on particle size distribution of soil aggregates and SOC density fractions were measured in a field experiment.The experiment included six treatments,i.e.,winter fallow (WF) without RS return (Ctrl),WF with 50%RS return (1/2RS),WF with 100%RS return (RS),GM without RS return (GM),GM with 50%RS return (GM1/2RS) and GM with 100%RS return (GMRS).The results showed that the proportion of small macro-aggregates (0.25–2 mm) and the mean weight diameter (MWD) of aggregates in the GMRS treatment was greater (by 18.9 and 3.41%,respectively) than in the RS treatment,while the proportion of silt+clay particles (<0.053 mm) was lower (by 14.4%).The concentration of SOC in microaggregates (0.053–0.25 mm)and silt+clay particles was higher in the GMRS treatment than in GM and RS treatments individually.The concentration and proportion of free light organic carbon (fLOC) in aggregates of various particle sizes and bulk soil was greater in the GMRS treatment than the RS treatment,whereas the concentration and proportion of mineral-associated organic carbon in small macroaggregates,microaggregates,and bulk was lower in the GMRS treatment than in the RS treatment.The proportion of intra-aggregate particulate organic carbon (iPOC) was greater in the GMRS treatment than in GM treatment.The GMRS treatment had strong positive effects on iPOC in small macroaggregates,suggesting that SOC was transferred from fLOC to iPOC.In conclusion,co-utilizing green manure and rice straw cultivated the SOC pool by increasing the concentration of fLOC and improved soil carbon stability by promoting the sequestration of organic carbon in iPOC as a form of physical protection.
基金funded by the the Public Service Sectors (Agriculture) Research Special Funds, China(201203013-06)supported in partial by the International Plant Nutrition Institute (IPNI ChinaProgram: Hunan-16)the Key Technologies R&D Program of China during the 12th Five-Year-Plan period(2012BAD05B05-3)
文摘Increasing K+ adsorption can be an effective alternative in building an available K pool in soils to optimize crop recovery and minimize losses into the environment. We hypothesized that long-term fertilization might change K+ adsorption because of changes in the chemical and mineralogical properties of a rice (Oryza sativa L.). The aims of this study were (i) to determine clay minerals in paddy soil clay size fractions using X-ray diffraction methods and a numerical diagram-decomposition method; (ii) to measure K+ adsorption isotherms before and after H 2 O 2 oxidation of organic matter, and (iii) to investigate whether K+ adsorption is correlated with changes in soil chemical and mineral properties. The 30-yr long-term fertilization treatments caused little change in soil organic C (SOC) but a large variation in soil mineral composition. The whole-clay fraction (<5 μm) corresponded more to the fertilization treatment than the fine-clay fraction (<1 μm) in terms of percentage of illite peak area. The total percentage of vermiculite-chlorite peak area was significantly negatively correlated with the total percentage of illite peak area in the <5 μm soil particles (R=-0.946, P<0.0006). Different fertilization treatments gave significantly different results in K+ adsorption. The SOC oxidation test showed positive effects of SOC on K+ adsorption at lower K+ concentration ( 120 mg L-1) and negative effects at higher K+ concentration (240 mg L-1). The K+ adsorption by soil clay minerals after SOC oxidization accounted for 60-158% of that by unoxidized soils, suggesting a more important role of soil minerals than SOC on K+ adsorption. The K+ adsorption potential was significantly correlated to the amount of poorly crystallized illite present (R=0.879, P=0.012). The availability of adsorbed K+ for plant growth needs further study.
基金supported by the earmarked fund for China Agriculture Research System (CARS-22)the Key Special Projects in National Key Research and Development Plan of China (2017YFD0301504 and 2016YFD0300900)+1 种基金the Scientific and Technological Innovation Project in Hunan Academy of Agricultural Sciences, China (2017JC47)the International Plant Nutrition Institute, Canada (IPNI China Program: Hunan-18)
文摘The double-rice cropping system is a very important intensive cropping system for food security in China. There have been few studies of the sustainability of yield and accumulation of soil organic carbon (SOC) in the double-rice cropping system following a partial substitution of chemical fertilizer by Chinese milk vetch (Mv). We conducted a 10-year (2008–2017) field experiment in Nan County, South-Central China, to examine the double-rice productivity and SOC accumulation in a paddy soil in response to different fertilization levels and Mv application (22.5 Mg ha^–1). Fertilizer and Mv were applied both individually and in combination (sole chemical fertilizers, Mv plus 100, 80, 60, 40, and 0% of the recommended dose of chemical fertilizers, labeled as F100, MF100, MF80, MF60, MF40, and MF0, respectively). It was found that the grain yields of double-rice crop in treatments receiving Mv were reduced when the dose of chemical fertilizer was reduced, while the change in SOC stock displayed a double peak curve. The MF100 produced the highest double-rice yield and SOC stock, with the value higher by 13.5 and 26.8% than that in the F100. However, the grain yields increased in the MF80 (by 8.4% compared to the F100), while the SOC stock only increased by 8.4%. Analogous to the change of grain yield, the sustainable yield index (SYI) of double rice were improved significantly in the MF100 and MF80 compared to the F100, while there was a slight increase in the MF60 and MF40. After a certain amount of Mv input (22.5 Mg ha^–1), the carbon sequestration rate was affected by the nutrient input due to the stimulation of microbial biomass. Compared with the MF0, the MF100 and MF40 resulted in a dramatically higher carbon sequestration rate (with the value higher by 71.6 and 70.1%), whereas the MF80 induced a lower carbon sequestration rate with the value lower by 70.1% compared to the MF0. Based on the above results we suggested that Mv could partially replace chemical fertilizers (e.g., 40–60%) to improve or maintain the productivity and sustainability of the double-rice cropping system in South-Central China.
基金funded by the Special Fund for AgroScientific Research in the Public Interest of China (20110300508, 201203030)supported in partial by the Key Technologies R&D Program of China during the 12th Five-Year Plan period (2012BAD05B05-3, 2013BAD07B11)the International Plant Nutrition Institute, Canada (IPNI China Program: Hunan-17)
文摘In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregateassociated carbon(C) and nitrogen(N). The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay(classified as Fe-Accumuli-Stagnic Anthrosols) with continuous early and late rice. In 2009, soil samples were collected(0-15 cm depth) from the field treatment plots and separated into water-stable aggregates of different sizes(i.e., >5, 2-5, 1-2, 0.5-1, 0.25-0.5 and <0.25 mm) by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.
基金Supported by National Science and Technology Support Plan Project,China(2012BAD14B17-1)Key and Special Project of Hunan Province Science and Technology,China(2011FJ1002-3)
文摘A field experiment of organic manure,passivator and their complex was conducted to study the soil Cd bioavailability in the Cd polluted paddy soil. The results showed that the rice yield increased with the applications of organic manure,passivator and their complex,especially,the rice yields of applying 3 000 and 6 000 kg / hm2 of organic manure increased significantly by 18. 6%( P < 0. 05) and 20. 9%( P < 0. 05) because of the increase of rice economic coefficient. There had no significant change of the soil p H values and the soil available Cd contents,but the Cd distribution ratios in rice were lowered by applying organic manure,and the Cd contents of rice applying 3 000 and 6 000 kg / hm2 of organic manure dropped by 14. 3%( P > 0. 05) and 21. 4%( P > 0. 05) compared with chemical fertilizer treatment,respectively. But applying with passivator and passivator fertilized with 3 000 and 6 000 kg / hm2 of organic manure,the soil p H values increased and the soil available Cd contents decreased significantly,so that to restrain the rice's Cd absorption and accumulation. The rice Cd contents lowered by 28. 6%( P < 0. 05),28. 6%( P < 0. 05)and 42.9%( P<0.05),the stem Cd contents lowered by 8. 9%( P > 0. 05),29. 7%( P < 0. 05) and 43. 6%( P < 0. 05),and the leaf Cd contents decreased by 18. 8%( P < 0. 05),25. 0%( P < 0. 05) and 25. 0%( P < 0. 05),respectively. It enhanced the inactivate effect of passivator significantly when fertilized with organic manure.
基金Supported by International Plant Nutrition Institute (IPNI China Program: Hunan-11 )Hunan Provincial Key Subject ( Grant No.04NK2006)
文摘A pot experiment combined with15N isotope techniques was conducted to evaluate effects of the varying rates of urea-N fertilizer application on yields,quality,and nitrogen use efficiency (NUE) of pakchoi cabbage (Brassica chinensis L.) and asparagus lettuce (Lactuca saiva L.).15N-labbled urea (5.3515N atom %) was added to pots with 6.5 kg soil of 0.14,0.18,0.21,0.25,and 0.29 g N/kg soil,and applied in two splits:60 percent as basal dressing in the mixture and 40 percent as topdressing.The fresh yields of two vegetable species increased with the increasing input of urea-N,but there was a significant quadratic relationship between the dose of urea-N fertilizer application and the fresh yields.When the dosage of urea-N fertilizer reached a certain value,nitrate readily accumulated in the two kinds of plants due to the decrease in NR activity; furthermore,there was a linear negative correlation between nitrate content and NR activity.With the increasing input of urea-N,ascorbic acid and soluble sugar initially increased,declined after a while,and crude fiber rapidly decreased too.Total absorbed N (TAN),N derived from fertilizer (Ndff),and N derived from soil (Ndfs) increased,and the ratio of Ndff and TAN also increased,but the ratio of Ndfs and TAN as well as NUE of urea-N fertilizer decreased with the increasing input of urea-N.These results suggested that the increasing application of labeled N fertilizer led to the increase in unlabeled N (namely,Ndfs) presumably due to "added nitrogen interaction" (ANI),the decease in NUE of urea-N fertilizer may be due to excess fertilization beyond the levels of plant requirements and the ANI,and the decrease in the two vegetable yields with the increasing addition of urea-N possibly because the excess accumulation of nitrate reached a toxic level.
基金Acknowledgements： The work was supported by National Natural Science Foundation （No. 40771200） and by Intemational Plant Nutrition Institute with China Scheme （Canada-Sino Cooperation Project： HN-13）.
基金supported by Special Fund for Agro-scientific Research in the Public Interest(201103005)Ministry of Agriculture,China and the International Plant Nutrition Institute(IPNI,Hunan-14)
文摘Soil physical properties are important indicators of the potential for agricultural production.Our objective was to evaluate the effects of long-term inputs of green manures on physical properties of a reddish paddy soil(Fe-Typic Hapli-Stagnic Anthrosols) under a double cropping system.The common cropping pattern before the study was early-late rice-fallow(winter).The field treatments included rice-rice-fallow(R-R-WF),rice-rice-rape(R-R-RP),rice-rice-Chinese milk vetch(RR-MV),and rice-rice-ryegrass(R-R-RG).The rape,Chinese milk vetch and ryegrass were all incorporated as green manures 15 d before early rice transplanting during the following year.The soil bulk density in all green manure treatments was significantly reduced compared with the winter fallow treatment.Soil porosity with green manure applications was significantly higher than that under the winter fallow.The green manure treatments had higher 0.25-5 mm water stable aggregates and aggregates stabilities in the plow layer(0-15 cm depth) compared with the fallow treatment.The mean weight diameter(MWD) and normalized mean weight diameter(NMWD) of aggregates in the green manure treatment were larger than that with the winter fallow.Soil given green manure retained both a higher water holding capacity in the plow layer soil,and a larger volume of moisture at all matric potentials(-10,-33 and-100 kPa).We conclude that the management of double-rice fields in southern central China should be encouraged to use green manures along with chemical fertilizers to increase SOC content,improve soil physical properties and soil fertility.
基金supported by the earmarked fund of China Agriculture Research System(CARS-22)the Key R&D Projects in Hunan Province,China(2017NK2051)+1 种基金the National Key R&D Program of China(2017YFD0301504 and 2018YFD03006)the Hunan Agricultural Science and Technology Innovation Fund Project,China(2018zd06)。
文摘Improved utilization of rice(Oryza sativa L.)straw and Chinese milk vetch(Astragalus sinicus L.,vetch)has positive effects on rice production.So far,few studies have investigated the productivity of vetch under different residue management practices in double-rice cropping system.The effects of rice straw on the growth and nutrient accumulation of vetch across seven years(2011–2017)and the subsequent effects of rice straw and vetch on two succeeding rice crops in a vetch–rice–rice cropping system,with the vetch established by relay cropping,were examined.The seven-year double-rice experiment consisted of the following treatments:(1)100%chemical fertilizer(F-F100);(2)only vetch without chemical fertilizer(M-Con);(3)80%chemical fertilizer plus vetch plus a low-cutting height(low-retained stubble)with the removal of straw(M-F80);(4)80%chemical fertilizer plus vetch plus a low-cutting height with the retention of straw(M-F80-LR);(5)80%chemical fertilizer plus vetch plus a high-cutting height(high-retained stubble)with the retention of straw(M-F80-HR);and(6)no fertilizer(F-Con).The yields of the two rice crops after vetch were not affected by either the cutting height of stubble with retention of straw or by the management of straw(retention vs.removal)with low-cutting height of stubble.The yields of the two rice crops after vetch were significantly higher for M-F80-HR than for M-F80-LR,but the relative contributions of the high-cutting height and straw retention to the higher rice yield could not be determined in this study.The yield stability of the double-rice grain in M-F80-HR was also increased,as determined by a sustainable yield index.Significant increases in vetch biomass and nutrient uptake were observed in the fertilized treatments during the rice season compared with the unfertilized treatments.In M-F80-HR plots,improvements in the growing environment of the vetch by conserving soil water content were associated with the highest vetch biomass,nutrient uptake,and yield stability of vetch biomass.These increased nutrient inputs partially replaced the demand for chemical fertilizer and stimulated the rice yields.It can be concluded that retaining higher-cutting stubble residues with straw retention could be the best straw management practice for increasing the vetch biomass and nutrient use efficiency,thereby allowing utilization of high-cutting height with retention of straw and vetch to improve the stability of rice productivity in a double-rice cropping system.
基金Supported by the National Natural Science Foundation of China (No.40771120)the National Key Technologies Research and Development Program of China during the 11th Five-Year Plan Period (No.2007BAD87B11)
文摘A two-year lysimeter study was conducted to study the effects of different fertilizers and soils on nitrogen leaching loss in a double rice cropping system by considering three major types of paddy soils from the Dongting Lake area. The results showed that N concentration in the leachate did not differ significantly among the treatments of urea, controlled release N fertilizer and pig manure and that all these fertilizers produced higher total nitrogen (TN) concentrations in the leachate compared to the case where no fertilizer was applied. The TN leaching loss following urea treatment accounted for 2.28%, 0.66%, and 1.50% of the amount of N applied in the alluvial sandy loamy paddy soil (ASL), purple calcareous clayey paddy soil (PCC), and reddish-yellow loamy paddy soil (RYL), respectively. Higher TN loss was found to be correlated with the increased leachate volume in ASL compared with RYL, and the lowest TN loss was observed in the PCC, in which the lowest leachate volume and TN concentration were observed. Organic N and NH4+ -N were the major forms of N depleted through leachate, accounting for 56.8% and 39.7% of TN losses, respectively. Accordingly, soil-specific fertilization regimens are recommended; in particular, the maximum amount of fertilizer should be optimized for sandy soils with a high infiltration rate. To avoid a high N leaching loss from rice fields, organic N fertilizers such as urea or coated urea should primarily be used for surface topdressing or shallow-layer application and not for deep-layer application.
基金the National Science and Technology Supporting Programs of China under Grants No 2006BAD02A15 and 2006BAD15B02.
文摘In China’s major rice(Oryza sativa L.)production regions,the traditional fertilization modes are challenged by the continued decrease in manure and increase in mineral fertilizer.However,limited information exists on the influences of long-term fertilizer management on soil organic carbon(SOC)and soil physical properties under the intensive rice production system in southern China.The objective of this study was to characterize the changes of soil physical properties as related to mineral fertilizer,crop residues,and manure application based on a long-term field experiment.The experiment,initiated in 1986,has five treatments:unfertilized,mineral fertilizer alone,rice residues plus mineral fertilizer,low manure rate plus mineral fertilizer,and high manure rate plus mineral fertilizer.The cropping system consists of barley(Hordaum vulgare L.),early rice,and late rice,three crops in a year.In May 2006,after barley harvest,soil samples were collected from the 0~10 cm and 10~20 cm layers to determine SOC concentration,aggregate size distribution,bulk density(rb),saturated hydraulic conductivity(Ks),and soil water characteristic curves(SWCC).The results indicated that manure significantly reducedrb,increased SOC concentration,soil aggregation,Ks,transmission and storage porosity,as well as water retention capacity.Combined application of crop residue and mineral fertilizer also improved soil physical properties,but the improvement by mineral fertilizer alone was limited.Correlation analysis demonstrated that S,the slope of the SWCC at its inflection point,was closely associated with the selected physical parameters,suggesting S was an effective parameter for soil physical quality evaluation.Nevertheless,in applying the S-theory,a unified approach to define the residual water content should be considered.
基金Fundamental Research Funds for Central Non-profit Scientific Institution(Nos.1610132019011,1610132020012)the National Key Research and Development Program of China(Nos.2016YFD0800707,2016YFD0200109).
文摘Returning crop straw into the soil is an important practice to balance biogenic and bioavailable silicon(Si)pool in paddy,which is crucial for the healthy growth of rice.However,owing to little knowledge about soil microbial communities responsible for straw degradation,how straw return affects Si bioavailability,its uptake,and rice yield remains elusive.Herein,we investigate the change of soil Si fractions and microbial community in a 39-year-old paddy field amended by a long-term straw return.Results show that rice straw return significantly increased soil bioavailable Si and rice yield from 29.9%to 61.6%and from 14.5%to 23.6%,respectively,when compared to NPK fertilization alone.Straw return significantly altered soil microbial community abundance.Acidobacteria was positively and significantly related to amorphous Si,while Rokubacteria at phylum level,Deltaproteobacteria,and Holophagae at class level was negatively and significantly related to organic matter adsorbed and Fe/Mn-oxide-combined Si in soils.Redundancy analysis of their correlations further demonstrated that Si status significantly explained 12%of soil bacterial community variation.These findings suggest that soil bacteria community and diversity interact with Si mobility by altering its transformation,thus resulting in the balance of various nutrient sources to drive biological Si cycle in agroecosystem.
基金Supported by the Special Fund for Agro-Scientific Research in the Public Interest of China(Nos.200903003 and 201103001)
文摘Tillage practices can potentially afect soil organic carbon (SOC) accumulation in agricultural soils. A 4-year experiment was conducted to identify the influence of tillage practices on SOC sequestration in a double-cropped rice (Oryza sativa L.) field in Hunan Province of China. Three tillage treatments, no-till (NT), conventional plow tillage(PT), and rotary tillage(RT), were laid in a randomized complete block design. Concentrations of SOC and bulk density(BD) of the 0-80 cm soil layer were measured, and SOC stocks of the 0-20 and 0-80 cm soil layers were calculated on an equivalent soil mass(ESM) basis and fixed depth (FD) basis.Soil carbon budget(SCB) under diferent tillage systems were assessed on the basis of emissions of methane(CH4) and CO2 and the amount of carbon (C) removed by the rice harvest. After four years of experiment, the NT treatment sequestrated more SOC than the other treatments. The SOC stocks in the 0-80 cm layer under NT (on an ESM basis) was as high as 129.32 Mg C ha 1,significantly higher than those under PT and RT (P < 0.05). The order of SOC stocks in the 0-80 cm soil layer was NT > PT > RT,and the same order was observed for SCB; however, in the 0-20 cm soil layer, the RT treatment had a higher SOC stock than the PT treatment. Therefore, when comparing SOC stocks, only considering the top 20 cm of soil would lead to an incomplete evaluation for the tillage-induced efects on SOC stocks and SOC sequestrated in the subsoil layers should also be taken into consideration. The estimation of SOC stocks using the ESM instead of FD method would better reflect the actual changes in SOC stocks in the paddy filed, as the FD method amplified the tillage efects on SOC stocks. This study also indicated that NT plus straw retention on the soil surface was a viable option to increase SOC stocks in paddy soils.
基金the National Natural Science Foundation of China(No.41771353)the Science and Technology Planning Project of Hunan Province(No.2019RS2036)+1 种基金Changsha Plan Project of Science and Technology(under Grant No.kq1801025)the Hunan Engineering&Technology Research Centre for Irrigation Water Purification。
文摘As an aliphatic amino acid,cysteine(CYS)is diffuse in the living cells of plants and animals.However,little is known of its role in the reactivity of nano-sized zero-valent iron(NZVI)in the degradation of pollutants.This study shows that the introduction of CYS to the NZVI system can help improve the efficiency of reduction,with 30%more efficient degradation and a reaction rate constant nine times higher when nitrobenzene(NB)is used as probe compound.The rates of degradation of NB were positively correlated with the range of concentrations of CYS from 0 to 10 mmol/L.The introduction of CYS increased the maximum concentration of Fe(Ⅲ)by 12 times and that of Fe(II)by four times in this system.A comparison of systems featuring only CYS or Fe(Ⅱ)showed that the direct reduction of NB was not the main factor influencing its CYS-stimulated removal.The reduction in the concentration of CYS was accompanied by the generation of cystine(CY,the oxidized form of cysteine),and both eventually became stable.The introduction of CY also enhanced NB degradation due to NZVI,accompanied by the regeneration of CYS.This supports the claim that CYS can accelerate electron transfer from NZVI to NB,thus enhancing the efficiency of degradation of NB.
