The microbial community,nutrient supply and crop yields differ along a potassium fertilizer gradient under wheat-maize double-cropping systems

Soil microorganisms play critical roles in ecosystem function.However,the relative impact of the potassium(K)fertilizer gradient on the microbial community in wheat-maize double-cropping systems remains unclear.In this long-term field experiment(2008-2019),we researched bacterial and fungal diversity,composition,and community assemblage in the soil along a K fertilizer gradient in the wheat season(K0,no K fertilizer;K1,45 kg ha^(-1) K_(2)O;K_(2),90 kg ha^(-1)K_(2)O;K3,135 kg ha^(-1)K_(2)O)and in the maize season(K0,no K fertilizer;K_(1),150 kg ha^(-1) K_(2)O;K_(2),300 kg ha^(-1)K_(2)O;K_(3),450 kg ha^(-1)K_(2)O)using bacterial 16S rRNA and fungal internally transcribed spacer(ITS)data.We observed that environmental variables,such as mean annual soil temperature(MAT)and precipitation,available K,ammonium,nitrate,and organic matter,impacted the soil bacterial and fungal communities,and their impacts varied with fertilizer treatments and crop species.Furthermore,the relative abundance of bacteria involved in soil nutrient transformation(phylum Actinobacteria and class Alphaproteobacteria)in the wheat season was significantly increased compared to the maize season,and the optimal K fertilizer dosage(K2 treatment)boosted the relative bacterial abundance of soil nutrient transformation(genus Lactobacillus)and soil denitrification(phylum Proteobacteria)bacteria in the wheat season.The abundance of the soil bacterial community promoting root growth and nutrient absorption(genus Herbaspirillum)in the maize season was improved compared to the wheat season,and the K2 treatment enhanced the bacterial abundance of soil nutrient transformation(genus MND1)and soil nitrogen cycling(genus Nitrospira)genera in the maize season.The results indicated that the bacterial and fungal communities in the double-cropping system exhibited variable sensitivities and assembly mechanisms along a K fertilizer gradient,and microhabitats explained the largest amount of the variation in crop yields,and improved wheat?maize yields by 11.2-22.6 and 9.2-23.8%with K addition,respectively.These modes are shaped contemporaneously by the different meteorological factors and soil nutrient changes in the K fertilizer gradients.

Integrated Monitor System of Water and Fertilizer of Greenhouse Intelligent Irrigatio

The integration of water and fertilizer is a comprehensive technology combined irrigation and fertilizer, which has outstanding advantages of saving fertilizer, saving water, saving labor, protecting environment, high yield and high efficiency. Currently, most of the water and fertilizer integrated irrigation and fertilization and irrigation operation in the production-based greenhouse is achieved relying on artificial experience, which is hard to achieve timely, scientific and intelligent irrigation. In this study, the application of STM32 embedded system realized the real-time collection of the data from the humidity sensors buried in top, middle and low depth of soil, and water and fertilizer integrated irrigation work was completed in the greenhouse through automatic control according to the predetermined fertilization and irrigation strategies for different crops. Moreover, the system had remote monitoring function, which used the global system for mobile （GSM） module to provide users with remote short message services, and therefore, the users could not only achieve the remote intelligent monitoring on the irrigation, light, ventilation of the greenhouse through short messages, but also could start and stop the remote control system operation, so as to realize the automatic management of the greenhouse environment, achieving the purpose of remote fertilization and water-saving irrigation.

Effect of Continuous Application of Controlled Release Nitrogen Fertilizer in Various Types of Soil in Dong-Ting Lake Region under Double Rice Cropping System

[Objective] This study aimed to explore the effects of continuous application of controlled release nitrogen fertilizer under double rice cropping system. [Method] By modeling three types of paddy soils in Dong-Ting Lake area, four treatments as no fertilizer （CK）, urea, controlled release nitrogen fertilizer （CRNF） and 70% controlled release nitrogen fertilizer （70% CRNF） were designed in the micro-plot trials from 2005 to 2008. [Result] The rice yield in treatment CRNF at N 150 kg/hm2 was increased by 10.3%, 8.0% and 2.4% compared with treatment of urea, in alluvial sandy loamy paddy soil （ALS）, purple calcareous clayey paddy soil （PCS）, and reddish yellow loamy paddy soil （RYS）, respectively; and the yield in treatment of 70% CRNF was increased by 6.1%, 2.6% and -0.8%, respectively. The ranking order of nitrogen uptake amount by plant in early rice and late rice was CRNF 70% CRNF urea CK in all three types of soil. Nitrogen utilization efficiency of CRNF in above three types of soil was 60.7%, 59.6% and 56.3%, increased by 23.8%, 19.4% and 16.3% compared with that in treatment of urea, respectively. Nitrogen utilization efficiency of CRNF in early rice was increased year by year, and was higher than that of 70% CRNF during the whole experiment stage, while that in late rice was increased first and then decreased from the 3rd year. [Conclusion] Continuous application CRNF could alleviate the decreasing of soil nitrogen fertility and organic carbon especially in ALS, increase rice yield and nitrogen utilization efficiency in double-rice cropping system.

Responses of Nematode Communities to Inorganic Fertilizer Disturbance in a Farmland Ecosystem

Nematode communities were monitored in a field study at depths of 0～10 cmand 10～20 cm throughout a corn (Zea mays L.) growing season in the black soil region of NortheastChina. Plots were cropped corn with (IF) and without (NF) nitrogen fertilization. Fifteen familiesand 16 genera were observed in the nematode suspensions. Cephalobidae, Rhabditidae, Aphelenchus,Filenchus, and Helicotylenchus were found to be dominant genera/families in both plots at bothdepths. Significant differences were found between treatments and corn growing stages in the totalnumbers of nematodes during the study period. The total numbers of nematodes at the 0～10 cm depthwere higher in the inorganic fertilizer plot than in the control plot (no fertilizer applications)across jointing, filling, and mature stages. Bacterivores were the most abundant trophic groupsunder two treatments and at both depths, and the relative abundance averaged 42.8%.Omuivores-predators at both depths were lower in the inorganic fertilizer plot than in the controlplot during the study period, excluding corn jointing stage. Maturity index (MI) and plant parasiteindex (PPI) were used to detect the differences between the two treatments, MI and PPI wereeffective in distinguishing differences in nematode communities during corn growing season. The roleof nematode communities as bioindicators of ecosystem disturbance due to fertilization is noted.

Substitution of chemical fertilizer by Chinese milk vetch improves the sustainability of yield and accumulation of soil organic carbon in a double-rice cropping system

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.

Effect of Long-Term Application of K Fertilizer and Wheat Straw to Soil on Crop Yield and Soil K Under Different Planting Systems

Effect of application of K fertilizer and wheat straw to soil on crop yield and status of soil K in the plough layer under different planting systems was studied. The experiments on long-term application of K fertilizer and wheat straw to soil in Hebei fluvo aquic soil and Shanxi brown soil in northern China were begun in 1992. The results showed that K fertilizer and straw could improve the yields of wheat and maize with the order of NPK ＋ St 〉 NPK 〉 NP ＋ St 〉 NP, and treatment of K fertilizer made a significant difference to NP, and the efficiency of K fertilizer in maize was higher than in wheat under rotation system of Hebei. In contrast with Shanxi, the wastage of soil potassium was a more serious issue in the rotation system in Hebei, only treatment of NPK ＋ St showed a surplus of potassium and the others showed a wane. K fertilizer and straw could improve the content of water-soluble K, nonspecifically adsorbed K, non-exchangeable K, mineral K, and total K in contrast to NP; however, K fertilizer and straw reduce the proportion of mineral K and improve proportion of other forms of potassium in the two locating sites. Compared with the beginning of orientation, temporal variability character of soil K content and proportion showed a difference between the two soil types; furthermore, there was a decrease in the content of mineral K and total K simultaneously in the two locating sites. As a whole, the effect of K fertilizer applied to soil directly excelled to wheat straw to soil. Wheat straw to soil was an effective measure to complement potassium to increase crop yield and retard the decrease of soil K.

Carbon sequestration rate,nitrogen use efficiency and rice yield responses to long-term substitution of chemical fertilizer by organic manure in a rice–rice cropping system

Combined application of chemical fertilizers with organic amendments was recommended as a strategy for improving yield,soil carbon storage,and nutrient use efficiency.However,how the long-term substitution of chemical fertilizer with organic manure affects rice yield,carbon sequestration rate(CSR),and nitrogen use efficiency(NUE)while ensuring environmental safety remains unclear.This study assessed the long-term effect of substituting chemical fertilizer with organic manure on rice yield,CSR,and NUE.It also determined the optimum substitution ratio in the acidic soil of southern China.The treatments were:(i)NPK0,unfertilized control;(ii)NPK1,100%chemical nitrogen,phosphorus,and potassium fertilizer;(iii)NPKM1,70%chemical NPK fertilizer and 30%organic manure;(iv)NPKM2,50%chemical NPK fertilizer and 50%organic manure;and(v)NPKM3,30%chemical NPK fertilizer and 70%organic manure.Milk vetch and pig manure were sources of manure for early and late rice seasons,respectively.The result showed that SOC content was higher in NPKM1,NPKM2,and NPKM3 treatments than in NPK0 and NPK1 treatments.The carbon sequestration rate increased by 140,160,and 280%under NPKM1,NPKM2,and NPKM3 treatments,respectively,compared to NPK1 treatment.Grain yield was 86.1,93.1,93.6,and 96.5%higher under NPK1,NPKM1,NPKM2,and NPKM3 treatments,respectively,compared to NPK0 treatment.The NUE in NPKM1,NPKM2,and NPKM3 treatments was higher as compared to NPK1 treatment for both rice seasons.Redundancy analysis revealed close positive relationships of CSR with C input,total N,soil C:N ratio,catalase,and humic acids,whereas NUE was closely related to grain yield,grain N content,and phenol oxidase.Furthermore,CSR and NUE negatively correlated with humin acid and soil C:P and N:P ratios.The technique for order of preference by similarity to ideal solution(TOPSIS)showed that NPKM3 treatment was the optimum strategy for improving CSR and NUE.Therefore,substituting 70%of chemical fertilizer with organic manure could be the best management option for increasing CSR and NUE in the paddy fields of southern China.

Estimation of Nitrogen Fertilizer Use Efficiency in Dryland Agroecosystem

A field trial was carried out to study the nitrogen fertilizer recovery by four crops in succession in manurial loess soil in Yangling. The results showed that the nitrogen fertilizer not only had the significant effects on the first crop , but also had longer residual effects, even on the fourth crop. The average apparent nitrogen fertilizer recovery by the first crop was 31.7%, and the accumulative nitrogen recovery by the 4 crops was high as 62.3%, and the latter was double as the former. It is quite clear that the nitrogen fertilizer recovery by the first crop was not reliable for estimating the nitrogen fertilizer unless the residual effect of nitrogen fertilizer was included.

Low N apparent surplus with higher rice yield under long-term fertilizer postponing in the rice-wheat cropping system

Nitrogen(N)fertilization increases rice yield,but inappropriate N fertilizer application increases N loss and the risk of environmental pollution.Short-term fertilizer postponing(FP)generally reduces N apparent surplus and increases rice yields,but the effects of long-term FP on N surplus and rice yields remain unknown.Our study was the first to investigate the impacts of long-term FP(11 years)on N apparent surplus and rice yields.FP effects in the short term(≤6 years)did not affect rice yields,whereas FP effects in the long term(>6 years)increased rice yields by 13.9%compared with conventional fertilization(CF).FP did not affect panicles per unit area,1000-kernel weight,and filled-kernel rate,but spikelets per panicle increased over time due to spikelet formation stimulation.FP also reduced the N apparent surplus over time more strongly than CF owing to higher N accumulation and N utilization efficiency.FP effects in the long term also significantly increased soil organic matter,total N,and NH4_(+)^(-)N content.Our results were supported by a pot experiment,showing that rice yields in soils with a history of FP were significantly higher than those for soils without a history of FP,indicating that FP increased rice yields more strongly in later years mainly because of soil quality improvement.Our findings suggest that longterm FP can reduce N loss while increasing rice yields by improving soil quality.

Effect of Integrated Use of Inorganic Fertilizer and Organic Manures on Bacterial Wilt Incidence (BWI) and Tuber Yield in Potato Production Systems on Hill Slopes of Central Kenya

Bacterial wilt (BW) caused by Ralstonia solanacearum is one of the most damaging diseases of potato (Solanum tuberosum L.) in Kenya and worldwide. In Kenya, potato tuber yield losses due to BW infection are estimated at 50 ~ 100%. Low soil fertility is also one of the most important constraints limiting potato production in central Kenya highlands. Farmers tackle this problem through use of inorganic fertilisers and organic manures, both of which amend the soil environment to influence bacterial wilt development. Undecomposed organic manures can also introduce the pathogen into a clean field. Between short rains 1999 and 2000, 10 on-farm extension-researcher- farmer-designed and farmer-managed trials were done at Kianjuki catchment in Embu District. The objective was to use farmers?participatory research approach and select the most suitable organic and inorganic fertiliser combination(s) with lowest BWI and acceptable usable tuber yields, and also to demonstrate use of some components of integrated disease management methods in reduction of disease incidence and spread. Seven treatments were proposed, presented to the farmers for discussion and the most relevant four were selected for evaluation. A newly released potato variety 慉sante?was planted during the short rains 1999 and long rains 2000. BWI didn抰 result in significant differences between treatments but the tuber yields were significantly different in short rains of 1999 and 2000. During short rains 2000, both BWI and tuber yields and unusable tubers differed significantly between treatments. The results confirmed that well- decomposed manures or manures from pathogen-free areas can be used in combination with inorganic fertilisers to improve soil fertility and potato tuber yields in smallholder farms without influencing BWI. Use of certified seed tubers in pathogen free field and following recommended field sanitation measures resulted in apparently bacterial wilt free crop. Considering the high cost of inorganic fertiliser and its negative effects on the environment, reduced usage at half the recommended rates combined with half rates of FYM is feasible option friendly to the farmer, soil and environment. The interviewed farmers also ranked the option as the most appropriate combination for soil fertility improvement for potato production in smallholder farms.

Effects on Agronomic Traits,Yield and Benefit of One-year Triple Cropping "Maize-soybean" Strip Intercropping System Under Reduced Fertilizer Application

[Objectives] This study was conducted to investigate the effects on agronomic traits,yield and benefit of one-year triple cropping " maize-soybean" strip intercropping system under reduced fertilizer application. [Methods]A single factor randomized block design was used,and wide and narrow strip intercropping was adopted. Three different fertilization treatments,namely fertilizers for conventional field fertilization( A1),80% A1( A2) and 60% A1( A3) were applied to the field production. The fertilizing sites were about 25 cm away from maize and repeated three times. [Results]Compared with A1,the change laws of the agronomic traits and yield in the A2 and A3 intercropping systems were described as below. Agronomic traits: The plant height became shorter gradually for the spring soybean,but increased gradually for the summer soybean,the bottom pod height gradually reduced,and the node number,pods per plant and seeds per plant increased;and the plant height,ear length,rows per ear,seeds per row and 1 000-seed weight of the spring maize decreased. Yield: The yield of maize as the main crop decreased but not significant,by 3. 20% and 3. 99%,respectively in A2 and A3,both smaller than 5. 00%;the yield of the spring soybean significantly increased by 9. 70% and 11. 84%,respectively;the yield of the summer soybean increased by 5. 18% and 8. 98%,respectively;and the total yield increased by 0. 20% and 0. 92%,respectively. Benefit: The total output value increased by 2. 97 % and 4. 91 %,respectively,and the total benefit increased by 6. 39% and 11. 22%,respectively. [Conclusions] Under a 40% reduction in fertilizer applied in the field,the one-year triple cropping " maize-soybean" strip intercropping system still met the multi-target requirements of increasing grain production and economic benefits,and thus can be promoted and applied in Guangxi.

Production of Potash and N-Mg Compound Fertilizer via Mineral Shoenite from Kunteyi Salt Lake:Phase Diagrams of Quaternary System(NH_(4))_(2)SO_(4)-MgSO_(4)-K_(2)SO_(4)-H_(2)O in the Isothermal Evaporation and Crystallization Process

Based on the requirement of the new technology for producing potassium sulfate and N-Mg compound fertilizer,boussingaultite,by the reaction of the mineral shoenite from Kunteyi Salt Lake,Qinghai province,and the industrial by-product ammonium sulfate,the solubilities of the quaternary system(NH_(4))_(2)SO_(4)-MgSO_(4)-K_(2)SO_(4)-H_(2)O at 25.0℃in the isothermal evaporation and crystallization process were measured using the isothermal evaporation method,and the corresponding phase diagrams were plotted.According to the diagram,this system contains six saturation points and six solid phase fields of crystallization,which correspond to(K1-m,(NH_(4))m)_(2)SO_(4),(NH_(4))_(2)SO_(4)·MgSO_(4)·6H_(2)O,K_(2)SO_(4)·MgSO_(4)·6H_(2)O,MgSO_(4)·6H_(2)O,(K1-n,(NH_(4))n)_(2)SO_(4)·MgSO_(4)·6H_(2)O and MgSO_(4)·7H_(2)O,respectively.By analyzing and calculating the isothermal evaporation and dissolution phase diagram of this quaternary system at 25.0℃,K_(2)SO_(4)and(NH_(4))_(2)SO_(4)·MgSO_(4)·6H_(2)O can be separated via K_(2)SO_(4)·MgSO_(4)·6H_(2)O and(NH_(4))_(2)SO_(4)as raw materials.Theoretical calculations about the proposed process were carried out and verified by experiment,which indicated that the yield of potassium sulfate was improved and the magnesium resources were fully utilized.

External Costs and Optimum Use of Nitrogen Fertilizer Based on the Balance of Economic and Ecological Benefits in the Paddy Field System of the Dongting Lake Area, China

The external costs and the optimum use of nitrogen fertilizer based on the balance of economic and ecological benefits was studied with the paddy field system of Dongting Lake area, one of the main food production regions in China. The environmental impact was economically evaluated using methods of the environmental impact economical evaluation. The optimum use of nitrogen fertilizer was calculated based on the exterior diseconomy theory and by using the production function model. Both ecological benefits and farmers＇ economic benefits were considered. It was calculated on the data from 2002 that the losses caused by inappropriate utilization of nitrogen fertilizer in the process of food production were fishery, 0.1 × 10^7 RMB yuan; water treatment, 1.02 × 10^8 RMB yuan; tour business, 0.11 ×10^8 RMB yuan, and habitation environment, 0.3 × 10^7 RMB yuan, totally equivalent to 0.41 RMB yuan kg^-1 N. The economically satisfactory and the ecological agronomic nitrogen fertilizer dose for current production was 138 and 137 kg ha^-1, respectively. The research showed that the actual nitrogen fertilizer application amount in the paddy field system of the Dongting Lake area already reached or exceeded the farmers＇ economic satisfaction and the ecological agronomic nitrogen fertilizer dose for current production. An environmental tax is suggested to impose on over-use of nitrogen fertilizer.

Coupling of reduced inorganic fertilizer with plant-based organic fertilizer as a promising fertilizer management strategy for colored rice in tropical regions

Colored rice is a type of high-quality,high-added-value rice that has attracted increasing attention in recent years.The use of large amounts of inorganic nitrogen fertilizer in rice fields results in low fertilizer use efficiency and high environmental pollution.Organic fertilizer is a promising way to improve soil quality and sustain high yields.However,most studies focus on the effect of animal-based organic fertilizers.The effects of different ratios of plantbased organic fertilizer and inorganic fertilizer on the grain yield and quality of colored rice have rarely been reported.Therefore,a two-year field experiment was conducted in 2020 and 2021 to study the effects of replacing inorganic N fertilizers with plant-based organic fertilizers on the yield,nitrogen use efficiency(NUE),and anthocyanin content of two colored rice varieties in a tropical region in China.The experimental treatments included no nitrogen fertilization(T1),100% inorganic nitrogen fertilizer(T2),30%inorganic nitrogen fertilizer substitution with plant-based organic fertilizer(T3),60%inorganic nitrogen fertilizer substitution with plant-based organic fertilizer(T4),and 100% plantbased organic fertilizer(T5).The total nitrogen provided to all the treatments except T1 was the same at 120 kg ha-1.Our results showed that the T3 treatment enhanced the grain yield and anthocyanin content of colored rice by increasing nitrogen use efficiency compared with T2.On average,grain yields were increased by 9 and 8%,while the anthocyanin content increased by 16 and 10% in the two colored rice varieties under T3 across the two years,respectively,as compared with T2.Further study of the residual effect of partial substitution of inorganic fertilizers showed that the substitution of inorganic fertilizer with plant-based organic fertilizer improved the soil physiochemical properties,and thus increased the rice grain yield,in the subsequent seasons.The highest grain yield of the subsequent rice crop was observed under the T5 treatment.Our results suggested that the application of plantbased organic fertilizers can sustain the production of colored rice with high anthocyanin content in tropical regions,which is beneficial in reconciling the relationship between rice production and environmental protection.

Fertilizer Placement Affects Weed Growth and Grain Yield in Dry-Seeded Rice(Oryza sativa L.)Systems

A study was conducted in a split-plot design to evaluate the effect of fertilizer placement method on weed growth and grain yield in a dry-seeded rice (DSR) system. Main-plot treatments were four fertilizer placement methods: between narrow rows (between 15-cm-wide rows of the pattern 25-15-25 cm), between uniform rows (between 20-cm-wide rows), within uniform rows, and surface broadcast. Subplot treatments were three weed control methods: herbicide-treated, nontreated, and weed-free. Weed biomass was greater in the nontreated plots than in the herbicide-treated plots. Herbicide application reduced weed biomass by 89% to 99% compared with the nontreated control. Fertilizer placement did not influence weed biomass in the herbicide-treated plots;however, it greatly influenced biomass in the nontreated plots. Fertilizer placement on the surface increased weed biomass (69 -71 g·m–2) compared with the placement of fertilizer below the soil surface (37 -57 g·m–2). Fertilizer placement did not influence weed density and biomass at 60 days after planting. Nontreated plots yielded 700 to 2080 kg·ha–1. Grain yield was similar between the herbicide-treated (2660-3250 kg·ha–1) and weed-free (2620-3430 kg·ha–1) plots. Grain yield was not influenced when basal fertilizer was banded within (2390-2500 kg·ha–1) or between rows (2530-2650 kg·ha–1). However, grain yield decreased when basal fertilizer was broadcast on the soil surface (2200 kg·ha–1). The results of our study demonstrated that rice yield was usually lower with surface broadcast of fertilizer than with subsurface fertilizer treatments. In conclusion, surface broadcast of basal fertilizer may result in high weed pressure in DSR systems.

Mitigation of N_(2)O emissions in water-saving paddy fields:Evaluating organic fertilizer substitution and microbial mechanisms

Water-saving irrigation strategies can successfully alleviate methane emissions from rice fields,but significantly stimulate nitrous oxide(N_(2)O)emissions because of variations in soil oxygen level and redox potential.However,the relationship linking soil N_(2)O emissions to nitrogen functional genes during various fertilization treatments in water-saving paddy fields has rarely been investigated.Furthermore,the mitigation potential of organic fertilizer substitution on N_(2)O emissions and the microbial mechanism in rice fields must be further elucidated.Our study examined how soil N_(2)O emissions were affected by related functional microorganisms(ammonia-oxidizing archaea(AOA),ammonia-oxidizing bacteria(AOB),nirS,nirK and nosZ)to various fertilization treatments in a rice field in southeast China over two years.In this study,three fertilization regimes were applied to rice cultivation:a no nitrogen(N)(Control),an inorganic N(Ni),and an inorganic N with partial N substitution with organic manure(N_(i)+N_(o)).Over two rice-growing seasons,cumulative N_(2)O emissions averaged 0.47,4.62 and 4.08 kg ha^(−1)for the Control,Ni and N_(i)+N_(o)treatments,respectively.In comparison to the Ni treatment,the N_(i)+N_(o)fertilization regime considerably reduced soil N_(2)O emissions by 11.6%while maintaining rice yield,with a lower N_(2)O emission factor(EF)from fertilizer N of 0.95%.Nitrogen fertilization considerably raised the AOB,nirS,nirK and nosZ gene abundances,in comparison to the Control treatment.Moreover,the substitution of organic manure for inorganic N fertilizer significantly decreased AOB and nirS gene abundances and increased nosZ gene abundance.The AOB responded to N fertilization more sensitively than the AOA.Total N_(2)O emissions significantly correlated positively with AOB and nirS gene abundances while having a negative correlation with nosZ gene abundance and the nosZ/nirS ratio across N-fertilized plots.In summary,we conclude that organic manure substitution for inorganic N fertilizer decreased soil N_(2)O emissions primarily by changing the soil NO_(3)^(−)-N,pH and DOC levels,thus inhibiting the activities of ammonia oxidation in nitrification and nitrite reduction in denitrification,and strengthening N_(2)O reduction in denitrification from water-saving rice paddies.

Repositioning fertilizer manufacturing subsidies for improving food security and reducing greenhouse gas emissions in China

China removed fertilizer manufacturing subsidies from 2015 to 2018 to bolster market-oriented reforms and foster environmentally sustainable practices.However,the impact of this policy reform on food security and the environment remains inadequately evaluated.Moreover,although green and low-carbon technologies offer environmental advantages,their widespread adoption is hindered by prohibitively high costs.This study analyzes the impact of removing fertilizer manufacturing subsidies and explores the potential feasibility of redirecting fertilizer manufacturing subsidies to invest in the diffusion of these technologies.Utilizing the China Agricultural University Agri-food Systems model,we analyzed the potential for achieving mutually beneficial outcomes regarding food security and environmental sustainability.The findings indicate that removing fertilizer manufacturing subsidies has reduced greenhouse gas(GHG)emissions from agricultural activities by 3.88 million metric tons,with minimal impact on food production.Redirecting fertilizer manufacturing subsidies to invest in green and low-carbon technologies,including slow and controlled-release fertilizer,organic-inorganic compound fertilizers,and machine deep placement of fertilizer,emerges as a strategy to concurrently curtail GHG emissions,ensure food security,and secure robust economic returns.Finally,we propose a comprehensive set of government interventions,including subsidies,field guidance,and improved extension systems,to promote the widespread adoption of these technologies.

Liquid Organic Fertilizer and Planting Space Influencing the Growth and Yield of Rice （Oryza sativa L.） in System of Rice Intensification （SRI） Methods

This research aimed to know the influence of liquid organic fertilizer and planting space to the growth and yield of rice in System of Rice Intensification （SRI） methods. The research was conducted in Palur, Sukoharjo, laid on 98 m above sea level from December 2008 to April 2009. Experimental design used was Randomized Completely Block Design with two factors of treatment. The first factor was liquid organic fertilizer; consist of control, cebreng leaf, rumen of goat, banana tree hump, and maja fruit. The second factor was planting space; consisting of 25 cm × 25 cm, 30 cm ×30 cm and 35 cm× 35 cm. There were 15 combinations of treatment and each repeated three times. Data analyzed with F test at 5% and DMRT at 5%. Research result showed that liquid organic fertilizer of maja fruit serves the best on variable of stalk length. Planting space of 35 cm × 35 cm serves the best on variable of plant height, number of total sapling, number of productive sapling, weight of dry plant, weight of rice per clump, and weight of 1,000 rice grains. There is no interaction between liquid organic fertilizer and planting space on all variables.

Simulation of the Ecosystem Productivity Responses to Aerosol Diffuse Radiation Fertilization Effects over the Pan-Arctic during 2001–19

The pan-Arctic is confronted with air pollution transported from lower latitudes.Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects(DRFEs).While such DRFEs have been explored at low to middle latitudes,the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified.Here,we perform regional simulations at 0.2o×0.2ousing a well-validated vegetation model(Yale Interactive terrestrial Biosphere,YIBs)in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity(NPP)in the pan-Arctic during 2001-19.Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C(12.8%)yr^(-1)under clear-sky conditions,in which natural and anthropogenic sources contribute to 8.9% and 3.9%,respectively.Under all-sky conditions,such DRFEs are largely dampened by cloud to only 0.26 Pg C(1.24%)yr^(-1),with contributions of 0.65% by natural and 0.59% by anthropogenic species.Natural aerosols cause a positive NPP trend of 0.022% yr^(-1)following the increased fire activities in the pan-Arctic.In contrast,anthropogenic aerosols induce a negative trend of-0.01% yr^(-1)due to reduced emissions from the middle latitudes.Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter.Though affected by modeling uncertainties,this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming.

Denitrification Losses and N_(2)O Emissions from Different Nitrogen Fertilizers Applied to the Maize-Fluvo-Aquic Soil System

A field experiment was conducted to investigate the variations in denitrification losses and N2O emissions from 4 different types of nitrogen fertilizers (urea, ammonium nitrate, ammonium bicarbonate, and calcium nitrate) applied to the maize- fluvo-aquic soil system in the North China Plain by the method of intact soil core incubation and acetylene inhibition, and the responses of nitrogen fertilizers to maize grain yields. Results show that the denitrification loss from different nitrogen fertilizers ranged from 0.38-1.20 kg N ha-1, with no significant differences among different fertilizer treatments, and the N2O emission from 0.05-0.95 kg N ha-1, with a significant difference (P<0.05) among the treatments. The highest emission was from the treatment of ammonium nitrate, while the lowest from calcium nitrate. The nitrogen fertilizers increased the maize grain yield by 9.7-19.8% compared to control. But there were no significant differences in yield increase among the 4 types of nitrogen fertilizers. In comparison, urea had the best effect, whereas calcium nitrate had the least effect on increasing maize yield. The maize yield was 5.7% higher when urea was separately applied at 2 times than when it was applied at a time. In this case, however, the denitrification loss and the N2O emission were also increased by 4.05 and 1.84 kg N ha-1, respectively.