Soil Inorganic Nitrogen Content Research Articles

Circular economy fertilization: Testing micro and macro algal species as soil improvers and nutrient sources for crop production in greenhouse and field conditions

Nutrient losses from agricultural land to freshwater and marine environments contribute to eutrophication and often to the growth of algal blooms. However, the potential benefits of recycling this algal biomass back to agricultural land for soil quality and crop nutrition in a “circular-economy” has received little attention. We tested the effects of algal additions to arable soil in greenhouse-grown garden peas, and field plots of spring wheat, on plant growth and nutrition and physical and chemical properties of the soil. Representatives of five algal species, which contrasted in elemental composition, were applied at 0.2, 2 and 4 g kg−1 in the greenhouse and at 24 g m2 in the field. These included the cyanobacteria Arthrospira platensis (Spirulina), the unicellular green algae Chlorella sp., the red seaweed Palmaria palmata, and the brown seaweeds Laminaria digitata and Ascophyllum nodosum. In the greenhouse at the highest application rates (4 g kg−1), Chlorella sp., and Spirulina increased soil total nitrogen and available phosphorus, and Spirulina also increased soil nitrate concentrations. P. palmata and L. digitata significantly increased soil inorganic (NH4+ and NO3−) concentrations under all three application rates. Chlorella sp. significantly increased soil total P, N and C, available P, NH4+-N, and pea yield. Soil water-stable aggregates were unchanged by the algal additions in both the greenhouse and field study. In the field, 4 species (Chlorella sp. Spirulina, P. palmata and L. digitata) increased soil inorganic nitrogen concentrations, confirming their potential to recycle mineralizable nitrogen to agricultural soils, but no significant effects were found on wheat yields under the application rates tested.

Soil Nitrogen Responses to Soil Core Transplanting Along an Altitudinal Gradient in an Eastern Tibetan Forest

To understand the differential effects of altitudinal gradient on soil inorganic nitrogen concentration and associated ammonia-oxidizingbacteria (AOB) and archaea (AOA), intact soil cores from a primary coniferous forest were in situ incubated in an alpine forest at a 3582-m altitude (A1) and transplanted to subalpine forests at a 3298-m altitude (A2) and 3023-m altitude (A3) on the eastern Tibetan Plateau. Transplant cooled the soil temperature of A2 but warmed the A3 soil temperature. Both AOA and AOB were found at the three altitudes. Compared to A1, A2 had greater AOA and AOB abundance, but A3 showed lower AOA abundance in organic soil. The AOA abundance was negatively correlated with ammonium concentration at all three altitudes, but AOB showed the reverse trend. Our results suggested that the soil nitrogen process responded differentially to soil core transplanting at different altitudes.

Urban soils as hot spots of anthropogenic carbon accumulation: Review of stocks, mechanisms and driving factors

AbstractUrban soils and cultural layers may accumulate C over centuries and consequently large C stocks may be sequestered beneath cities. Processes and mechanisms leading to high C accumulation in urban soils remain unknown. Data on soil organic carbon (SOC), soil inorganic carbon (SIC), black (pyrogenic) carbon (BC), and nitrogen contents and stocks in urban soils were collected from 100 peer‐reviewed papers. The database (770 data points for SOC, SIC, and BC stocks from 116 cities worldwide) was analysed considering the effects of climate and urban‐specific factors (city size, age, and functional zoning) on C stocks. The processes of C accumulation specific for urban soils were analysed, and C sequestration rates were assessed. For the wide range of climatic conditions, total C content in urban soils was 1.5–3 times higher, and C accumulation was much deeper compared with natural soils, resulting in 3–5 times larger total C stocks. Urban SOC stocks increased with latitude, whereas SIC stocks were less affected by climate. City size and age were the main factors explaining intercity differences in C stocks. The intracity variability of C and N stocks was dominated by functional zoning: Large SOC and N stocks in residential areas and large SIC and BC stocks in industrial zones and roadsides were consistent across all climates and for cities of various sizes and ages. Substantial amounts of SOC, SIC, and N are sequestered in the subsoils, cultural layers, and sealed soils, underlining the importance of these hidden stocks for C assessments. Long‐term С input from outside the cities and associated C accumulation coincided with upward soil growth of ~50 cm per century, and continuous accumulation of 15–30 kg C/m2 per century in urban soils and cultural layers. We conclude that, despite the relatively small area of cities, urban soils are hot spots of long‐term soil C sequestration worldwide, and the importance of urban soils will increase in future with global urbanization.

Litter amendment rather than phosphorus can dramatically change inorganic nitrogen pools in a degraded grassland soil by affecting nitrogen-cycling microbes

Phosphorus fertilisation and increasing litter input are widely employed to restore the degraded grasslands. Despite the key roles of nitrogen-cycling microbes in determining the soil nitrogen dynamics and development of grassland degradation, little is known about their responses to these restoration efforts. Here, a microcosm experiment, with soils collected from a degraded Tibetan alpine meadow, was conducted to investigate the responses of nitrogen-cycling microbes to litter and phosphorus amendments, and their links with the changes in soil properties. Copies of the corresponding nitrogen-cycling genes (nifH, amoA, narG, nirK, and nirS genes) and their mRNAs were determined using real-time PCR. The results showed that the litter amendment significantly stimulated the transcription of nifH and nirS genes, but reduced the copies of amoA gene and bacterial amoA mRNA. It also significantly increased soil dissolved organic carbon, available phosphorus, ammonium nitrogen, and microbial biomass concentrations, but decreased soil inorganic and nitrate nitrogen concentrations. The phosphorus amendment exerted little effects on soil properties and nitrogen-cycling microbes, while the litter-phosphorus interactions significantly offset the individual negative effects of the litter and phosphorus amendments on the denitrifier abundance. The soil nitrate and inorganic nitrogen concentrations were positively correlated with the amoA genes and bacterial amoA mRNA copies, but negatively correlated with nirS mRNA copies. These results indicate that litter addition may decrease soil nitrate and inorganic nitrogen concentrations by suppressing nitrifiers and stimulating nirS gene expression, highlighting the vital roles of nitrogen-cycling microbes in determining the soil nitrogen dynamics during the restoration of degraded grasslands.

Potential inhibition of urine patch nitrous oxide emissions by Plantago lanceolata and its metabolite aucubin

ABSTRACTPlantain (Plantago lanceolata L.), a forage used in grazed pastures, contains active secondary metabolites that could potentially inhibit nitrification, a key step in nitrous oxide (N2O) production from grazing ruminant livestock urine patches. A field study was performed to determine the effects of aucubin, a secondary metabolite in plantain, on nitrification and soil N2O emissions under a ruminant urine patch. Soils were treated with bovine urine (700 kg ha−1) and either a plantain leaf extract (PLE), which contained all extractable compounds in plantain including aucubin, or an aucubin solution (AS). PLE and AS were applied at the same rate of aucubin (47 kg ha−1). N2O emissions were reduced by 50% and 70% in the PLE and AS treatments, respectively; however, there were no significant differences in soil inorganic nitrogen concentrations when urine was applied with PLE or AS.

Net primary productivity and its partitioning in response to precipitation gradient in an alpine meadow

The dynamics of net primary productivity (NPP) and its partitioning to the aboveground versus belowground are of fundamental importance to understand carbon cycling and its feedback to climate change. However, the responses of NPP and its partitioning to precipitation gradient are poorly understood. We conducted a manipulative field experiment with six precipitation treatments (1/12 P, 1/4 P, 1/2 P, 3/4 P, P, and 5/4 P, P is annual precipitation) in an alpine meadow to examine aboveground and belowground NPP (ANPP and BNPP) in response to precipitation gradient in 2015 and 2016. We found that changes in precipitation had no significant impact on ANPP or belowground biomass in 2015. Compared with control, only the extremely drought treatment (1/12 P) significantly reduced ANPP by 37.68% and increased BNPP at the depth of 20–40 cm by 80.59% in 2016. Across the gradient, ANPP showed a nonlinear response to precipitation amount in 2016. Neither BNPP nor NPP had significant relationship with precipitation changes. The variance in ANPP were mostly due to forbs production, which was ultimately caused by altering soil water content and soil inorganic nitrogen concentration. The nonlinear precipitation-ANPP relationship indicates that future precipitation changes especially extreme drought will dramatically decrease ANPP and push this ecosystem beyond threshold.

Economic and Soil Environmental Benefits of Using Controlled‐Release Bulk Blending Urea in the North China Plain

AbstractCrop production must be increased in order to ensure a sustainable food supply for the growing world population. Controlled‐release urea (CRU) improves nutrient use efficiency and saves labor, but its use in crop production is limited due to its high cost. Bulk blending urea (BBU) consists of both CRU and conventional urea and could be an excellent substitute or replacement for CRU. Nevertheless, its economic benefits and soil environment impact are unknown. A 3‐year field experiment was conducted to investigate the effects of two different nitrogen management practices in terms of economic benefits, soil mineral nitrogen availability, aggregate stability, and soil microbial communities. Split applications of conventional urea (UREA) and a single application of BBU were tested on winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) in the North China Plain between 2010 and 2013. Crop yields were measured after each harvest, and soil environmental parameters were determined after the 3‐year crop sequence. Relative to UREA, BBU significantly increased net revenue, soil inorganic nitrogen concentration, and the functional diversity of the soil microbial community without adverse effects on the soil bacterial community composition. On the other hand, BBU reduced the amount of soil macro‐aggregates and the mean weight diameter value of soil water‐stable aggregates. Although BBU showed great potential for improving wheat–maize cropping systems in the North China Plain, future studies should focus on optimizing the nitrogen dosage and the CRU ratio in BBU to decrease nitrogen leaching, avoid soil aggregate deterioration, and maintain crop yield. Copyright © 2017 John Wiley & Sons, Ltd.

Straw return and appropriate tillage method improve grain yield and nitrogen efficiency of winter wheat

AbstractStraw return is an important management tool for tackling and promoting soil nutrient conservation and improving crop yield in Huang-Huai-Hai Plain, China. Although the incorporation of maize straw with deep plowing and rotary tillage practices are widespread in the region, only few studies have focused on rotation tillage. To determine the effects of maize straw return on the nitrogen (N) efficiency and grain yield of winter wheat (Triticum aestivum L.), we conducted experiments in this region for 3 years. Five treatments were tested: (i) rotary tillage without straw return (RT); (ii) deep plowing tillage without straw return (DT); (iii) rotary tillage with total straw return (RS); (iv) deep plowing tillage with total straw return (DS); (v) rotary tillage of 2 years and deep plowing tillage in the 3rd year with total straw return (TS). Treatments with straw return increased kernels no. ear−1, thousand-kernel weight (TKW), grain yields, ratio of dry matter accumulation post-anthesis, and nitrogen (N) efficiency whereas reduced the ears no. ha−1 in the 2011–2012 and 2012–2013 growing seasons. Compared with the rotary tillage, deep plowing tillage significantly increased the grain yield, yield components, total dry matter accumulation, and N efficiency in 2013–2014. RS had significantly higher straw N distribution, soil inorganic nitrogen content, and soil enzymes activities in the 0–10 cm soil layer compared with the DS and TS. However, significantly lower values were observed in the 10–20 and 20–30 cm soil layers. TS obtained approximately equal grain yield as DS, and it also reduced the resource costs. Therefore, we conclude that TS is the most economical method for increasing grain yield and N efficiency of winter wheat in Huang-Huai-Hai Plain.

Effects of controlled release blend bulk urea on soil nitrogen and soil enzyme activity in wheat and rice fields

A field experiment was conducted to investigate the effect of controlled-release fertilizer (CRF) combined with urea (UR) on the soil fertility and environment in wheat-rice rotation system. Changes in four forms of nitrogen (total nitrogen, ammonium nitrogen, nitrate nitrogen, and microbial biomass nitrogen) and in activities of three soil enzymes participating in nitrogen transformation (urease, protease, and nitrate reductase) were measured in seven fertilization treatments (no fertilization, routine fertilization, 10%CRF+90%UR, 20%CRF+80%UR, 40%CRF+60%UR, 80%CRF+20%UR, and 100%CRF). The results showed that soil total nitrogen was stable in the whole growth period of wheat and rice. There was no significant difference among the treatments of over 20% CRF in soil total nitrogen content of wheat and rice. The soil inorganic nitrogen content was increased dramatically in treatments of 40% or above CRF during the mid-late growing stages of wheat and rice. With the advance of the growth period, conventional fertilization significantly decreased soil microbial biomass nitrogen, but the treatments of 40% and above CRF increased the soil microbial biomass nitrogen significantly. The soil enzyme activities were increased with over 40% of CRF in the mid-late growing stage of wheat and rice. By increasing the CRF ratio, the soil protease activity and nitrate reductase activity were improved gradually, and peaked in 100% CRF. The treatments of above 20% CRF could decrease the urease activity in tillering stage of rice and delay the peak of ammonium nitrogen, which would benefit nitrogen loss reduction. The treatments of 40% and above CRF were beneficial to improving soil nitrogen supply and enhancing soil urease and protease activities, which could promote the effectiveness of nitrogen during the later growth stages of wheat and rice. The 100% CRF treatment improved the nitrate reductase activity significantly during the later stage of wheat and rice. Compared with the treatments of 40%-80% CRF, 100% CRF reduced the soil nitrate content of 20-40 cm soil layer in wheat significantly suggesting it could reduce the loss of nitrogen.

Characteristics of Biochar-mediated N2O Emissions from Soils of Different Surface Conditions

It was aimed to investigate the response to biochar addition on N2O gas production and emission in different surface conditions. To study the dynamic changes of soil N2O release, soil nitrate(NO3--N) and ammonium(NH4+-N), a field trials experiment was conducted from 2014 to 2015 in wheat and corn season, which contained three treatments[the blank control group (CK), biochar applied at 5 t·(hm2·a)-1(BC5) and 45 t·(hm2·a)-1(BC45), respectively] under crop cultivation(+) and non-cultivation(-) condition. The results indicated that:1 During the season of wheat growth, the soil N2O emissions of CK+, BC5+, BC45+ were 21.70-88.91, 21.42-130.09, 64.44-179.58 μg·(m2·h)-1 respectively, and that of BC45+ possessed a higher value than those of the other treatments(P<0.05). Compared with wheat winter period, the soil N2O emissions of the three treatments decreased evidently in wheat peak stage(returning green and jointing stage, booting and heading stage) (P<0.05), and the amplification of BC45+ reduced by 18.43% and 14.62% in comparison with CK+ and BC5+ in wheat booting and heading stages. In the early stage of maize growth, the soil N2O emissions of BC45+ were significantly increased compared with CK+ and BC5+(P<0.05). However, there were no significant differences among treatments of maize heading stage and mature stage. It showed that the biochar-mediated promotion effect of soil N2O emissions was effectively inhibited by crop growth and the increase of surface mulch. Besides, the result of soil N2O release in the same treatment had also confirmed this conclusion in bare land. 2 Under the conditions of wheat cultivation and homochronous non-cultivation, the soil NO3--N and NH4+-N contents of BC5+ and BC45+ treatments were raised with respect to CK+, but the values dropped significantly in wheat peak stage, especially for BC45+ treatment, with 96.44% and 69.40% decrease respectively. The soil inorganic nitrogen content of maize growth season had a similar trend in wheat season. Parallel to this result of the apparently falling soil NO3--N and NH4+-N concentrations, the soil N2O emissions of BC45+ also declined remarkably in peak stage. The decline in respiratory substrate caused by the increase of nitrogen uptake by crop growth, may be one of the reasons for the decrease of N2O emission. 3 In wheat growth season, the soil pH values of the biochar treatments were improved from 4.62 to 5.18. In maize season, the soil pH values ranged from 4.42 to 5.02. When the soil pH value was relatively low, the soil N2O emission was high, and vice versa. The soil N2O emission was partly influenced by the soil pH value.

Intraspecific variation in morphological traits of root branch orders in Chamaecyparis obtusa

We aimed to clarify the intraspecific variation in the morphological traits of branch orders under different soil conditions in Chamaecyparis obtusa (Siebold & Zucc.) Endl. We investigated the morphological traits of branch orders, based on 16,351 individual roots that were dissected from 12 intact fine root systems, up to a diameter of 2 mm at three C. obtusa stands. We also measured the concentrations of soil carbon, nitrogen, and inorganic nitrogen. The intact fine root systems up to the diameter of 2 mm had branched into between five and seven orders. The diameter of first- to fourth-order roots and the lengths of second- and third-order roots were significantly different among the three stands. The morphological traits of lower order (first to third) roots correlated with soil inorganic nitrogen concentrations, but higher order (fourth to sixth) roots correlated with soil carbon concentrations. We clarified the possible ranges of intraspecific variation in the morphological traits of root branch orders within C. obtusa. Both the lower and higher orders of the intact fine root systems were tightly related to the surrounding soil conditions.

Experimental Manipulation of Precipitation Affects Soil Nitrogen Availability in Semiarid Mongolian Pine (Pinus sylvestris var. mongolica) Plantation

Expected changes in precipitation over large regions of the world under global climate change will have profound effects on terrestrial ecosystems in arid and semiarid regions. To explore how changes in the amount of precipitation in the growing season would affect soil nitrogen (N) availability in a semiarid ecosystem, we established rainout shelters and irrigation systems by simulating 30% reduced (DRY) and 30% increased precipitation (WET) relative to natural precipitation (Control) to measure some key soil process properties for two growing seasons in a nutrient-poor Mongolian pine (P. sylvestris var. mongolica) plantation. Both WET and DRY treatments significantly affected monthly soil inorganic nitrogen concentrations, which showed a higher inorganic N under DRY than Control in each month and lower in WET than Control. Monthly soil microbial biomass N content was reduced by DRY and raised by WET treatments. The results indicated the asynchrony of the availability of soil moisture and soil nutrients in Mongolian pine plantations at the Horqin Sandy Lands in Northeast China. Water limited plant growth in Mongolian pine plantations when precipitation decreased, and nitrogen limitation became increasingly important when precipitation increased. Accumulation of N in microbial biomass is an important mechanism for N cycling in this ecosystem. To effectively manage Mongolian pine plantations, it is advised that evapotranspiration is minimized when precipitation decreases and that there is an increase in soil N availability by protecting litterfall when precipitation increases.

Inhibition effect of zinc in wastewater on the N2O emission from coastal loam soils

The effects of zinc (Zn) on nitrous oxide (N2O) fluxes from coastal loam soil and the abundances of soil nitrifier and denitrifier were studied in a tidal microcosm receiving livestock wastewater with different Zn levels. Soil N2O emission significantly increased due to discharge of wastewater rich in ammonia (NH4+-N) while the continuous measurements of gas flux showed a durative reduction in N2O flux by high Zn input (40mgL−1) during the low tide period. Soil inorganic nitrogen concentrations increased at the end of the experiment and even more soil NH4+-N was measured in the high-Zn-level treatment, indicating an inhibition of ammonia oxidation by Zn input. Quantitative PCR of soil amoA, narG and nirK genes encoding ammonia monooxygenase, nitrate reductase and nitrite reductase, respectively, showed that the microbial abundances involved in these metabolisms were neither affected by wastewater discharge nor Zn contamination.

Effects of tillage and nitrogen application rate on soil nitrogen transformation and yield in a winter wheat/summer maize multiple cropping system

In the winter-wheat and summer-maize multiple cropping system in lime concretion black soil of Huanghuaihai Plain, the effects of three tilling methods (conventional tillage, rotary tillage, subsoiling tillage) in wheat season coupling with three nitrogen treatments (120 kg·hm-2, 225 kg·hm-2, 330 kg·hm-2) before maize sowing on the activities of microorganisms and enzymes re-lated nitrogen transformation, and inorganic nitrogen content in the rhizosphere soil during the main growth stages of maize, as well as the yield were investigated. The results showed that the rotary tillage had the highest ammonification intensity, and the more nitrogen was put in, the higher were the activities of microorganisms and enzymes related to soil nitrogen transformation. The activities of nitrification, denitrification and urease of subsoiling tillage was significantly higher than those of conventional and rotary tillage. Furthermore, in subsoiling tillage treatment, increasing nitrogen fertili-zer could promote soil nitrogen transformation while excessive nitrogen input inhibited soil nitrogen transformation, though the latter had higher yield and soil inorganic nitrogen content. The treatment of subsoiling tillage coupling with 225 kg·hm-2 nitrogen, was best for soil nitrogen transformation while the treatment of subsoiling tillage coupling with 330 kg·hm-2 nitrogen, had the highest corn yield.

Cumulative release characteristics of controlled-release nitrogen and potassium fertilizers and their effects on soil fertility, and cotton growth.

To investigate the interacting effects of polymer coated urea (PCU) and polymer coated potassium chloride (PCPC) on cotton growth, an experiment was conducted with containerized plants in 2014 and 2015. There were two kinds of nitrogen fertilizer, PCU and urea, which were combined with PCPC at three application rates (40, 80 and 120 kg ha−1). The kinds of nitrogen fertilizer formed the main plot, while individual rates of PCPC were the subplots. The results suggested N and K release patterns for PCU and PCPC in the soil were closely matched to the N and K requirements by cotton. Soil inorganic nitrogen contents significantly increased by using PCU instead of urea, and the same trend was observed with soil available potassium contents, which also had increased rates. Meanwhile, the number of bolls and lint yields of cotton in the PCU treatments were 4.9–35.3% and 2.9–40.7% higher than from urea treatments. Lint yields also increased by 9.1–12.7% with PCPC80 and PCPC120 treatments compared with PCPC40 treatment at the same nitrogen type. Hence, application of PCU combined with 80 kg ha−1 of PCPC fertilizer on cotton increased the yields and fertilizer use efficiencies in addition to improving fiber quality and delaying leaf senescence.

The effects of different intensities of long-term grazing on the direction and strength of plant–soil feedback in a semiarid grassland of Northwest China

Plant–soil feedbacks (PSFs) and grazing drive community dynamics in grasslands. We examined how the intensity of grazing and PSF interact to affect plant growth and explored what drives the observed feedback effects. Three dominant perennial plant species; Artemisia capillaris, Lespedeza davurica, and Stipa bungeana were grown in field-conditioned soil (sterilized or unsterilized) collected from four grazing intensities in a semiarid grassland of northwest China. Soil nutrient concentrations and root fungal communities were determined. Plant biomass increased with grazing intensity for the three plant species. Within each grazing intensity, plant growth in sterilized soil relative to unsterilized soil differed markedly among species. Soil inorganic nitrogen (N) concentration tended to increase with increasing grazing intensity. Arbuscular mycorrhizal fungi (AMF) colonization was high for all grazing intensities for L. davurica. Fusarium tricinctum, the most common pathogenic Fusarium species, had the highest frequency from the control for A. capillaris and tended to increase with increasing grazing intensity for S. bungeana. Our results suggest that in grasslands plant growth can be modified by the intensity of grazing via grazing-induced changes in soil nutrient availability and fungal communities. Additional studies are needed to determine how grazing intensity affects species co-existence through PSFs to mixed communities.

Effects of non-native Asian earthworm invasion on temperate forest and prairie soils in the Midwestern US

Effects of invasive European earthworms in North America have been well documented, but less is known about ecological consequences of exotic Asian earthworm invasion, in particular Asian jumping worms (Amynthas) that are increasingly reported. Most earthworm invasion research has focused on forests; some Amynthas spp. are native to Asian grasslands and may thrive in prairies with unknown effects. We conducted an earthworm-addition mesocosm experiment with before–after control-impact (BACI) design and a complementary field study in southern Wisconsin, USA, in 2014 to investigate effects of a newly discovered invasion of two Asian jumping worms (Amynthas agrestis and Amynthas tokioensis) on forest and prairie litter and soil nutrient pools. In both studies, A. agrestis and A. tokioensis substantially reduced surface litter (84–95 % decline in foliage litter mass) and increased total carbon, total nitrogen, and available phosphorus in the upper 0–5 cm of soils over the 4-month period from July through October. Soil inorganic nitrogen (ammonium– and nitrate–N) concentration increased across soil depths of 0–25 cm, with greater effects on nitrate–N. Dissolved organic carbon concentration also increased, e.g., 71–108 % increase in the mesocosm experiment. Effects were observed in both forest and prairie soils, with stronger effects in forests. Effects were most pronounced late in the growing season when earthworm biomass likely peaked. Depletion of the litter layer and rapid mineralization of nutrients by non-native Asian jumping worms may make ecosystems more susceptible to nutrient losses, and effects may cascade to understory herbs and other soil biota.

Improving Winter Wheat Yields In Organic Farming Systems Through Innovations In Green Manure Management

The paper presents effect of perennial grasses (Trifolium pratense L., Medicago sativa L., xFestulolium) and their aboveground mass management methods (removed from the field, mixed, mulching) as preceding crops on Ninorg in the soil as well as on yield of winter wheat under conditions of ecological farming. Field experiments were carried out at the Joniškėlis Research Station of the Lithuanian Institute of Agriculture (LIA) on an Gleyic Cambisol. Experimental evidence indicated that content of symbiotically fixed nitrogen in the biomass of legumes accounted for the largest share (61–84 %) of the total nitrogen content (208.0–298.0 kg ha- 1), accumulated in the biomass. Winter wheat grain yield significantly (r = 0.783; P &amp;lt; 0.05) correlated with soil inorganic nitrogen content in spring. Grain yield productivity increased by 0.01 t ha-1 after incorporation of 1 kg ha-1 nitrogen of legume crops biomass.

Studies on Changes of Soil Carbon and Nitrogen Dynamics under Long-Term Fertilizer in the Black Soil Based on DSSAT Model

Long-term experiment of Gongzhuling base for the study through three treatments(1)NPK: NPK fertilizer; (2)N165M: Manure and NPK fertilizer; (3)1.5M+NPK: 1.5Manure and NPK fertilizer, used DSSAT-Century soil model to study the long-term effects of different fertilizer treatments on soil organic carbon, total nitrogen content and the laws of growth and decline. The results show that: long-term application of nitrogen fertilizer can significantly improve crop yields compare with NPK.. Corn production is also affected by climatic conditions, especially in drought years with less precipitation. Larger impact of organic manure on soil organic carbon (SOC)and total nitrogen, SOC content obtained in descending order of 1.5M + N165&gt; N165&gt; N0 by Century model simulation. Soil organic carbon content and nitrogen content has a certain relevance, and the trend is consistent. Organic manure and inorganic fertilizer can significantly reduce soil inorganic nitrogen content and reduce the risk of nitrogen leaching. Through model simulations C / N ratio could be explained: C / N increases indicated an increase of organic carbon faster than organic nitrogen in soil, and changes of soil chronic library SOM2 determined organic carbon content. Therefore we should pay attention to organic manure carbon return level, vigorously promote the use of farmyard manure to improve soil nutrient content.

NO, N2O and CO2 soil emissions from Venezuelan corn fields under tillage and no-tillage agriculture

The largest share of Latin American and Caribbean (LAC) anthropogenic greenhouse gases is derived from land use changes as well as forestry and agriculture, representing up to 67 % of the relative contribution from all sources. However, in spite of the rapid expansion of LAC tropical agriculture, little is known about its impact on atmospheric trace gases emissions, such as nitrogen oxides (NO x ), nitrous oxide (N2O) and carbon dioxide (CO2), which are produced in soils by microbial processes and also accelerated in tropical climates. This information is crucial for assessing mitigation strategies linked to agricultural practices to satisfy food demands for the region’s future. We measured NO, N2O and CO2 soil emissions along with soil variables from corn fields under tillage (T) and no-tillage (NT) agriculture at two of the largest cereal-producing regions in Venezuela during the crop-growing season. We found statistically significant positive correlations between the logarithms of nitrogen gas emissions and soil inorganic nitrogen concentrations, soil water and clay contents. Average emissions of NO and CO2 were larger in T than NT sites, while N2O fluxes showed the opposite. CO2 emissions from T were 1.6 as much as those found in NT, whereas N2O was 0.5 of that found in NT. These results imply that NT practices more effectively mitigate climate change from these monoculture systems mainly because of CO2 emission reduction. We suggest then that agricultural mitigation actions for tropical monoculture systems should aim for the enhancement of NT management practices along with N fertilization rate reduction to compensate for the larger N2O emissions.