Inorganic Nitrogen Fertilizer Research Articles

Influence of Organic and Inorganic Nitrogen on the Growth and Yield of Wheat

To assess the effects of organic and inorganic N fertilizers regarding wheat yield and growth a field experiment was carried out from November 2019 to March 2020 at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh. There were three replications of the experiment, which was set up using a randomized full block design. The experiment comprises four varieties viz. BARI Gom-28, BARI Gom-30, BARI Gom-31, BARI Gom-32 and five levels of N viz. Control, 90 kg N ha-1 from prilled urea (PU), 57 kg N ha-1 from prilled urea (PU) + 3 t ha-1 poultry manure (PM) as organic N source, 62 kg N ha-1 from PU + 5 t ha-1 cowdung as organic N source, 29 Kg N ha-1 from PU + 4 t ha-1 vermicompost as organic N source. The outcome of the experiment revealed that there were substantial differences in the growth and yield of wheat due to different varietal effects and application of organic and inorganic nitrogen fertilizers, although some of the attributes were not found significant. At growth, BARI Gom-32 produced the highest number of total tillers hill-1 and leaf area index, while the highest number of total tillers hill-1 and leaf area index were obtained from 57 kg N ha-1 from PU and 3 t ha-1 PM at 20, 40, 60 and 80 DAS. At harvest, the highest number of effective tillers plant-1 (2.82), filled grain spike-1 (32.06), 1000-grain weight (61.07 g), grain yield (3.94 t ha-1), straw yield (5.85 t ha-1) and harvest index (40.11%) were obtained from BARI Gom-32. While, application of 57 kg N ha-1 from PU and 3 t ha-1 PM produced the tallest plant (95.49 cm), number of total tillers plant-1 (3.96), number of effective tillers plant-1 (3.20), filled grain spike-1 (36.61), 1000-grain weight (60.18 g from T5), grain yield (4.34 t ha-1), straw yield (6.23 t ha-1) and harvest index (41.07%). Again, the maximum number of total tillers plant-1 (4.06), number of effective tillers plant-1 (3.46), filled grain spike-1 (39.13), 1000-grain weight (64.62 g), grain yield (4.38 t ha-1), straw yield (6.27 t ha-1 ) and harvest index (41.16%) were found from BARI Gom-32 in combination with 57 kg N ha-1 from prilled urea and 3 t ha-1 poultry manure. Therefore, it can be concluded that BARI Gom-32 in combination with 57 kg N ha-1 from prilled urea and 3 t ha-1 poultry manure was more potential in terms of yield and would be suggested for the cultivation of wheat.

Improving rice grain yield and reducing lodging risk simultaneously: A meta-analysis

Smart agronomic management practices (e.g., employing lodging-resistant cultivars, appropriate fertilization, and applying plant growth regulators (PGRs)) can reduce crop lodging risk. However, their integrated effects on grain yield and lodging risk in rice paddies remain poorly defined. Here, we conducted a meta-analysis to examine the effects of agronomic practices on rice yield and lodging risk, synthesizing data from 68 published studies with 475 observations. Our results showed that compared with inbred varieties, hybrid rice increased grain yield by an average of 8.9%, and enhanced lodging index (LI) (increasing lodging risk with a higher LI) at the 1st (+23%) and 3rd (+17%) internodes with no significant effect at the 2nd internode. Inorganic nitrogen (N) fertilization increased both rice yield (+42%) and LI at the 2nd (+31%) and 3rd (+23%) internodes, but did not significantly affect LI at the 1st internode. The application of silicon (Si) and potassium (K) fertilizers increased rice yield by 7.2% and 18%, respectively, while simultaneously reducing LI by 14% and 19% at the 1st internode, by 15% and 21% at the 2nd internode, and by 4.5% and 18% at the 3rd internode. Prohexadione calcium and uniconazole increased rice yield by 6.7% and 8.3%, respectively, while paclobutrazol had no significant effect on rice yield. Prohexadione calcium and uniconazole reduced LI by 14% and 21% at the 1st internode, by 26% and 31% at the 2nd internode, and by 16% and 54% at the 3rd internode, respectively, whereas paclobutrazol only reduced LI at the 3rd internode by 12%. In conclusion, the application of Si, K, prohexadione calcium, and uniconazole is a promising strategy for improving rice yield and reducing lodging risk. In addition, we suggest that high-yielding practices (e.g., hybrid rice and inorganic N fertilization) and lodging-resistant practices (e.g., the application of Si, K, and PGRs) should be combined to increase grain yield and simultaneously reduce lodging risk in rice paddies.

The addition of biochar and nitrogen alters the microbial community and their cooccurrence network by affecting soil properties

Biochar plays an important role in reducing the harmful environmental effects of inorganic nitrogen (N) fertilizers on agroecosystems, but the the impact mechanisms of biochar combined with N fertilizers on soil microorganisms are not clear enough. In this study, high-throughput sequencing was used to study the influences of three N fertilizer levels (0 (N0), 90 (N90) and 120 (N120) kg ha−1) and two biochar levels (0 (B0) and 20 (B20) t ha−1) on the soil microbial community and symbiotic network among microbial taxa in wheat fields. Compared to the control (B0N0), N fertilizer alone or combined with biochar significantly increased soil total N, available N, and organic matter in topsoil (0–20 cm), and the same results were found only in B20N120 treatment in subsoil (20–40 cm). In addition, bacterial and fungal diversity in topsoil were significantly increased and decreased by all N and biochar treatments, respectively. Moreover, soil bacterial and fungal community compositions also were also changed by N and biochar. Furthermore, biochar weakened the competition and cooperation among microorganisms in topsoil and subsoil, and the keystone species of networks were also changed by biochar. Redundancy analysis showed that soil total N, available N, available P, available K and pH were the main environmental factors driving the changes in bacterial and fungal community structures. These data indicated that the addition of N fertilizer and biochar could improve soil fertility by maintaining the stability of microbial community structures, which can provide reasonable guidance for the sustainable development of agriculture, such as maintaining dryland production.

The Effect of Inorganic Nitrogen and Phosphorus Fertilizers, Chicken Manure and Their Combinations on Growth and Development of Common Bean (Phaseolus vulgaris L.)

The Effect of Inorganic Nitrogen and Phosphorus Fertilizers, Chicken Manure and Their Combinations on Growth and Development of Common Bean (Phaseolus vulgaris L.)

Rendered materials partly substitute inorganic nitrogen fertilizers and improve nitrogen recovery in maize production system

Rendered materials partly substitute inorganic nitrogen fertilizers and improve nitrogen recovery in maize production system

Long-term experimental data and crop modelling to inform the ecological intensification of irrigated wheat production in South Africa

Wheat (Triticum aestivum L.) production is threatened by climate change and the decline in agricultural land available due to urbanisation, farmers switching to other crops, and environmental degradation. The aim of this study was to investigate the ecological intensification (EI) of irrigated wheat production in South Africa. Data from the long-term wheat trial at the University of Pretoria and an intensive growth analysis conducted in 2019 were used to calibrate and evaluate the APSIM model. Following adequate model performance, improved management scenarios including crop rotation, manure application, optimised inorganic nitrogen (N) fertiliser application rate, objectively scheduled irrigation, and a combination of all these improved management practices together, were tested. The adoption of all management practices simultaneously was shown to be the best practice, achieving an increase of 18% in yield and reducing deep drainage and N leaching by 31%. Whereas measured data indicated a decrease in soil organic matter (SOM) from 1.20% in 1950 to 0.58% in 2019, adopting EI measures could reduce the loss of SOM to only 0.68%. Farmers are encouraged to adopt one or more of these EI management practices as their site-specific situations allow.

Reduced nitrogen fertilization under flooded conditions cut down soil N2O and CO2 efflux: An incubation experiment

Unreasonable water (W) and inorganic nitrogen (N) fertilization cause an intensification of soil greenhouse gas (GHGs) emissions. W–N interactions (W × N) patterns can maximise the regulation of soil GHGs efflux through the rational matching of W and N fertilization factors. However, the effects of W × N patterns on soil GHGs efflux and the underlying mechanism remain unclear. In this study, urea fertilizers were applied to paddy soils in a gradient of 100 (N100), 80 (N80), and 60 mg kg−1 (N60) concentrations. Flooding (W1) and 60% field holding capacity (W2) was set for each N fertilizer application to observe the effects of W × N patterns on soil properties and GHGs efflux through incubation experiments. The results showed that W significantly affected soil electrical conductivity and different N forms (i.e., alkali hydrolyzed N, ammonium N, nitrate N and microbial biomass N) contents. Soil organic carbon (C) content was reduced by 14.40% in W1N60 relative to W1N100, whereas microbial biomass C content was increased by 26.87%. Moreover, soil methane (CH4) fluxes were low in all treatments, with a range of 1.60–1.65 μg CH4 kg−1. Soil nitrous oxide (N2O) and carbon dioxide (CO2) fluxes were significantly influenced by W, N and W × N. Global warming potential was maintained at the lowest level in W1N60 treatment at 0.67 g CO2-eq kg−1, suggesting W1N60 as the preferred W × N pattern with high environmental impact. Our findings demonstrate that reduced N fertilization contributes to the effective mitigation of soil N2O and CO2 efflux by lowering the soil total N and organic C contents and regulating soil microbial biomass C and N.

Impact of Compost Tea and Spirulina platensis Algae on Sugar Beet Grown under Different Levels of Inorganic Nitrogen Fertilizer.

<b>Background and Objective:</b> Nitrogen is an essential macronutrient for plant growth, improving the absorption and utilization of some other nutrients and controlling total plant development. Compost tea (CT) is an aqueous extract of compost that contains high organic matter levels necessary for plants and aerobic soil microorganisms. <i>Spirulina platensis</i> is a multi-cellular blue-green micro-alga that contains green pigments, high levels of nutrients and plant growth regulators. This work was designed to study the possibility of using CT and <i>S. platensis</i> algae culture filtrate (ACF) in improving plant growth, yield and quality of sugar beet grown under different nitrogen fertilizer levels. <b>Materials and Methods:</b> Two field experiments were conducted at Ismailia Research Station, Ismailia Province, Egypt, during the 2019/2020 and 2020/2021 seasons. The study involved two N levels (90 and 120 kg/fed), three CT rates (without, 30 and 60 l/fed) and three ACF levels (without, 1 and 2 l/fed) three times. A split-plot design was used. <b>Results:</b> Adding 120 kg N/fed increased crop growth rate (CGR), root yield/fed (RY) and sugar yield/fed (SY), while, sucrose (%) and quality index (QI) decreased. Soil drench with 60 l CT/fed incremented leaf area index (LAI), CGR, sucrose (%), RY and SY. Increasing ACF level up to 2 l/fed increased LAI, sucrose (%), QI, RY and SY. Root yield was positively correlated with SY and negatively with QI. <b>Conclusion:</b> Applying 90 kg N/fed combined with a soil drench of 60 l CT/fed and foliar spraying with 2 l ACF/fed thrice can be recommended to attain economical root and sugar yields.

Effects of Nitrogen Source and Rate on Soybean Yield and Quality

ABSTRACT The poultry industry in North Carolina (NC) has increased substantially over the past few decades, which has led to widespread availability of poultry litter. While many grain producers in NC utilize litter in their fertilization programs, it is typically applied to the corn or wheat crops that are in the rotation with soybean, instead of directly prior to soybeans. However, there is interest in application to soybean. Therefore, three field sites were established across NC in both 2019 and 2020, with four replicates of 11 treatments: four litter rates (22.4, 44.8, 89.7 and 134.5 Mg/hectare), six inorganic nitrogen (N) fertilizer rates (16.8, 33.6, 67.3, 134.5, 201.8, and 269.0 kg N/hectare), and a control. The impact of these treatments on biomass production, tissue N, plant population, yield, and grain quality were investigated. There was no significant effect on yield in 2019; however, there was a significant effect on yield in 2020, showing a negative correlation with inorganic N fertilizer in Plymouth and a 22% reduction in yield over the range of inorganic N treatments. It is possible there was an increased salt effect in these plots, as there was a negative response in plant population at five of six site years. While there was a positive correlation between grain protein and increasing inorganic N rate, growers are not paid based on grain quality. The results of this study suggest N application at planting is not beneficial for growers, but litter could be applied to meet soybean phosphorus or potassium demands.

Nitrate contamination in water resources, human health risks and its remediation through adsorption: a focused review.

The level of nitrate in water has been increasing considerably all around the world due to vast application of inorganic nitrogen fertiliser and animal manure. Because of nitrate's high solubility in water, human beings are getting exposed to it mainly through various routes including water, food etc. Various regulations have been set for nitrate (45-50 mgNO3-/L) in drinking water to protect health of the infants from the methemoglobinemia, birth defects, thyroid disease, risk of specific cancers, i.e. colorectal, breast and bladder cancer caused due to nitrate poisoning. Different methods like ion exchange, adsorption, biological denitrification etc. have the ability to eliminate the nitrate from the aqueous medium. However, adsorption process got preference over the other approaches because of its simple design and satisfactory results especially with surface modified adsorbents or with mineral-based adsorbents. Different types of adsorbents have been used for this purpose; however, adsorbents derived from the biomass wastes have great adsorption capacities for nitrate such as tea waste-based adsorbents (136.43mg/g), carbon nanotube (142.86mg/g), chitosan beads (104mg/g) and cetyltrimethylammonium bromide modified rice husk (278mg/g). Therefore, a thorough literature survey has been carried out to formulate this review paper to understand various sources of nitrate pollution, route of exposure to the human beings, ill effects along with discussing the key developments as well as the new advancements reported in procuring low-cost efficient adsorbents for water purification.

Genetic modification of flavone biosynthesis in rice enhances biofilm formation of soil diazotrophic bacteria and biological nitrogen fixation.

Improving biological nitrogen fixation (BNF) in cereal crops is a long-sought objective; however, no successful modification of cereal crops showing increased BNF has been reported. Here, we described a novel approach in which rice plants were modified to increase the production of compounds that stimulated biofilm formation in soil diazotrophic bacteria, promoted bacterial colonization of plant tissues and improved BNF with increased grain yield at limiting soil nitrogen contents. We first used a chemical screening to identify plant-produced compounds that induced biofilm formation in nitrogen-fixing bacteria and demonstrated that apigenin and other flavones induced BNF. We then used CRISPR-based gene editing targeting apigenin breakdown in rice, increasing plant apigenin contents and apigenin root exudation. When grown at limiting soil nitrogen conditions, modified rice plants displayed increased grain yield. Biofilm production also modified the root microbiome structure, favouring the enrichment of diazotrophic bacteria recruitment. Our results support the manipulation of the flavone biosynthetic pathway as a feasible strategy for the induction of biological nitrogen fixation in cereals and a reduction in the use of inorganic nitrogen fertilizers.

Impact of NPK Enriched Bio-Compost on Rice Yield and Sustainability of Nutrients in Sandy Loam Soils of India

ABSTRACT To feed the burgeoning population, the cultivation of rice is exploited on low fertility soils, which are otherwise not fit for its cultivation. To enhance the fertility status of such soils, the nutrient-enriched bio-compost play vital role in maintaining the soil productivity and yield sustainability. Field experiments were conducted on sandy loam soil for two years (2016–2017 and 2017–2018) to evaluate the impact of different combinations of N (nitrogen)-, P (phosphorus)-, and K (potassium)-enriched bio-compost with inorganic nitrogen, phosphorus and potassium fertilizers (NPK) on crop productivity, nutrient uptake, and soil fertility by rice under rice-wheat system. The results reported that growth parameters, yield attributing characters, grain and straw yield of rice improved significantly by different NPK-enriched bio-compost treatments. Rice grain yield increased significantly, that is, 4350 kg ha−1 with the application of 150% NPK over recommended fertilizer (3360 kg ha−1). Also, plant growth parameters and yield attributing characters improved with application of bio-compost applied @ 4 t ha−1. The NPK content in grains and their buildup in soil were significantly higher in treatments where 25% NPK were substituted through NPK-enriched bio-compost and 75% NPK through inorganic fertilizers. Overall, it is concluded that integrated use of 25% nutrients through NPK-enriched bio-compost and 75% nutrients through NPK inorganic fertilizers is the best option for the maintenance of soil health and sustainable rice yield.

Effect of inorganic and organic nitrogenous fertilizers on soil nutrient status, plant growth and yield of apricot (Prunus armeniaca L.)

The work is aimed to find out the most suitable substitute of CAN fertilizer to assess its effect on fertility, growth and yield of apricot. The experiment constituted 11 treatments replicated thrice in RBD design at the Research Farm of Department of Soil Science and Water Management, Nauni, Solan, India during 2015 and 2016. The highest organic carbon (1.34, 1.21%) was recorded with treatment T11 [100% urea enriched compost + 0% Ca (NO3)2] at 0–15 and 15–30 cm depths. There were significant variations and maximum available N and P contents were recorded under treatment T7 (urea 100% + lime 708 g/tree) while, maximum K was in T1 which indicated that available N, P and K increased by 16.95% and 16.58%; 34.83% and 32.36%; 19.98% and 12.76% over the initial values recorded, respectively at 0–15 and 15–30 cm depths. The highest available Ca (4.46 and 4.11[cmol (p+) kg−1]) was recorded under T1, Mg (2.11 and 1.95 [cmol (p+) kg−1]) under T6 and available S contents (56.46 kg ha−1and 51.67 kg ha−1) under T9 at surface and subsurface depths, respectively. Available Zn, Cu, Fe and Mn were highest under treatment T6 (urea100%+ 0%Ca (NO3)2). Maximum increase in tree height (0.40 m) and trunk girth (0.50 cm) was observed under T7 (urea 100% + lime 708 g/tree). Similarly, maximum fruit yield (30.03 kg/tree) was recorded with T7. From the present investigation, it is concluded that application of urea 100%+ lime 708 g/tree improved soil fertility, plant growth and yield during the study.

Co-Application of Biochar Compost and Inorganic Nitrogen Fertilizer Affects the Growth and Nitrogen Uptake by Lowland Rice in Northern Ghana

Inherent low soil fertility status limits productivity of rice in the lowland ecologies in Northern Ghana. Combining organic and inorganic nitrogen fertilizers could help to maintain the fertility of lowland soils for rice production. A screen house pot experiment was carried out to investigate the combined effect of biochar compost and inorganic nitrogen fertilizer on the nitrogen uptake and agronomic performance of rice plants grown on an eutric gleysol lowland soil. Inorganic nitrogen fertilizer alone and its combinations with different types of biochar compost (based on the proportions of biochar and compost) were used as treatment. A control (unamended soil) was also included. The incorporation of biochar compost and inorganic nitrogen fertilizer improved the growth parameters and yield components of rice plants. The combination of biochar compost and inorganic nitrogen fertilizer was also found to improve nitrogen uptake in rice plants. This practice could be the most likely viable option for alleviating lowland soil fertility issues and increasing rice productivity in Northern Ghana.

Investigating Farmer Perspectives and Compost Application for Soil Management in Urban Agriculture in Mwanza, Tanzania

African countries are urbanizing at a rapid rate. Research on urban agriculture may be key to ensuring urban food and soil security. This study aimed to evaluate pathways for integrated soil fertility management using a mixed methods approach to consider both social perspectives and soil quality in the city of Mwanza, Tanzania. The social component of urban agriculture was explored using semi-structured interviews with urban farmers (n=34), through judgement and snowball sampling. Qualitative analyses showed that urban farmers range in age and gender, as well as in experiences and cultivation practices, though all use hand tools. Farmers reported reliance on rainy seasons for cultivating. However, farmers also raised concerns about a changing climate and unpredictability of rain, which impacts crop productivity. Most interviewed farmers (82%) would like to improve their soils, and many use manure as an amendment stating that animal manure is the best way to improve soil. Additionally, most urban farmers (62%) have not tried any form of food waste compost but responded positively to try it if they had access and were taught how to use it. For the second aspect of this study a field trial was conducted to evaluate and compare the effects of organic and inorganic amendments on soil quality and crop productivity over the short-term. The results from the field trial determined that organic amendments (poultry manure and food waste compost) improved soil water holding capacity by 14 to 19% and enhanced microbial biomass 1.7 to 4 times compared to treatments with inorganic nitrogen fertilizer. Crop productivity with organic amendments was comparable to that in treatments with nitrogen fertilizer. We conclude that urban agriculture is an integral aspect of Mwanza City, and the application of organic amendments improves urban soil quality compared to the application of inorganic fertilizer, which has implications for urban soil security, land use planning, and food sovereignty in developing countries.

Effect of Combined Application of Chicken Manure and Inorganic Nitrogen Fertilizer on Yield and Quality of Cherry Tomato

Unreasonable application of inorganic nitrogen (N) fertilizer on cherry tomatoes (Solanum lycopersicum var. cerasiforme) has resulted in serious environmental threats. The advantages of application of organic manure combined with inorganic N fertilizer for vegetable production systems have been reported widely, but there are still few studies on cherry tomato production. Therefore, this study aims to determine the impact of a combined application of organic manure (in form of chicken manure at different application rate of 0 and 40 t ha−1) with inorganic N fertilizer (in form of urea at various N application rates of 0, 160 and 320 kg N ha−1) on the fruit yield and quality of cherry tomato across two seasons. Results showed that inorganic N application exhibited positive effects on fruit yield and its associated components of cherry tomato. However, there was no significant difference in terms of fruit yield and its associated components between the two N rates of inorganic N (160 and 320 kg N ha−1), indicating that fruit yield is not improved significantly when the N application rate exceeds some threshold. Under chicken manure application treatments, however, an increased N rate did not show a positive effect on fruit yield. Importantly, chicken manure application has greatly increased fruit yield and fruit quality (represented by membership function indicator) by 43% and 23%, respectively in comparison with zero manure application. In particular, the soluble protein and titratable acid were increased by 124% and 118%, respectively. Overall, these results suggested that chemical N fertilizers could be largely replaced with chicken manure. Furthermore, the combined application of organic with inorganic N fertilizers seems to be a promising management practice for reducing the reliance on use of inorganic N fertilizer, while mitigating the environmental burden for cherry tomato production.

Straw residue incorporation and potassium fertilization enhances soil aggregate stability by altering soil content of iron oxide and organic carbon in a rice–rape cropping system

AbstractBoth iron (Fe) oxide and soil organic carbon (SOC) content, among other factors, drive the development and subsequent stability of soil aggregates. However, the mechanism of these drivers in paddy‐upland rotation systems with straw residue incorporation is not well understood. In this multiyear (2011–2017) trial, we sought to study the factors which drive the stability of soil aggregates in such a rice‐rape (RR) agronomic system. In order to examine the effect of straw residue incorporation and potassium fertilization on soil aggregation dynamics, we divided our trial into four treatments: inorganic phosphorus (P) and nitrogen (N) fertilizer; inorganic NPK fertilizer; inorganic NP fertilizer plus straw residue; and inorganic NPK fertilizer plus straw residue. Treatments which incorporated straw residue significantly increased both the geometric mean diameter (GMD) and the mean weight diameter (MWD) of soil aggregates. Soil aggregate stability was greater after rape harvest than after rice harvest, while SOC shows the opposite trend. Straw residue incorporation increased the SOC and, specifically, concentrations of aliphatic‐C and aromatic‐C, particularly in aggregates greater than 0.25 mm. Straw residue addition significantly increased both the amorphous (Feo) and complex iron oxide (Fep) contents of soil. In both bulk soil and in aggregates greater than 5 mm, SOC and Fep were positively correlated with MWD, while in aggregates less than 5 mm, Feo was positively correlated with MWD. Overall, we suggest that the increased concentrations of SOC, alkane‐C, Feo, and Fep in soils after incorporation of straw residue were responsible for increasing soil aggregate stability.

Impact of long-term application of manure and inorganic fertilizers on common soil bacteria in different soil types

Understanding the impact of long-term fertilization in different soil types and its effect on soil bacteria and crop production is critical for designing sustainable agricultural practices across diverse landscapes. Here, we investigated the impact of 25–37 years of continuous fertilizer treatments in three parent materials (Phaeozem, Cambisol, and Acrisol) on crop yield, soil properties, and soil bacteria (i.e., the total 16 S rRNA gene abundance, community structure, and its relationship with soil nutrient) across diverse Chinese agriculture areas. Four consistent treatments were included: unfertilized control (CK), inorganic nitrogen fertilizer (N), manure (M), and manure plus nitrogen (MN). The crop yields were significantly increased under MN treatments at the rates of 147 kg/ rotation (3 years) in Phaeozem and 90.6 kg/ rotation (1 year) in Acrisol, while the crop yields remained constant or decreased for CK and N treatments. The relative abundance of Acidobacteria_Gp6 and Planctomycete were significantly higher in manure treatments than in chemical fertilizer treatment. Through the structural equation model (SEM) analysis, species in module 1 were directly correlated with crop yield, and both module 2 and module 3 species were indirectly correlated with crop yield via SOM and NO3- contents. Proteobacteria, Acidobacteria, and Firmicutes were dominant bacterial groups in the three modules, respectively. This study reveals the complex role of keystone ecological clusters of soil bacteria on crop yields and identifies the common bacterial taxa that respond to long-term fertilization and thereby, as potential targets for improving soil fertility across soil types.

Inorganic nitrogen fertilizer, biochar particle size and rate of application on lettuce (Lactuca sativa L.) nitrogen use and yield

Lettuce (Lactuca sativa L.) efficient use of nitrogen (NUE) determines its growth and yield. We assessed the interaction effect of N fertilizer and biochar of different particle sizes and rates on NUE, growth and yield of lettuce. A factorial design arranged in Randomized Complete Block Design with four replications was used to conduct a field experiment at the FRNR farm, Kwame Nkrumah University of Science and Technology, Ghana. The treatment consisted of biochar at 8.33 t and 16.67 t ha−1 with different particle sizes (<2, 5 and 10 mm) and five rates (0, 31.3, 62.5, 93.83 and 125 kg ha−1) of inorganic N fertilizer. Our result showed that integrating 8.33 t ha−1 of <2 mm and 5 mm biochar with 62.5 and 93.8 kgN ha−1, respectively improved lettuce growth, NUE by 30% and yield. The yield (19.3 t ha−1) obtained with these applications is comparable to the achievable yield (20 t ha−1) of lettuce under the sole N recommended rate (125 kgN ha−1). In conclusion, with 8.33 t ha−1 of <2 mm biochar, farmers can reduce the recommended inorganic N rate of lettuce by half (62.5 kg ha−1) and still attain good yield with improved post-harvest soil fertility. This has implications for farmers’ production costs, agriculture waste management and climate change mitigation strategies.

Replacing urea-N with Chinese milk vetch (Astragalus sinicus L.) mitigates CH4 and N2O emissions in rice paddy

Chinese milk vetch (Astragalus sinicus L) is a widely used leguminous green manure in paddy rice culture and has potential to replace or partly replace inorganic nitrogen (N) fertilizer. However, there is little quantitative information regarding replacing inorganic N with milk vetch on CH4 and N2O emissions. This study investigated the relationship between greenhouse gas production and carbon (C) and N release under 0%, 25%, 50%, 75% and 100% substitution of urea-N with milk vetch aboveground litter in a paddy soil. CH4 and N2O emission fluxes were measured using a static chamber method and milk vetch decomposition rates were tested by mesh bag method. After incorporation, C and N release from milk vetch followed a single exponential decay model, with 82.3–89.1% and 98.8–98.9% of the original C and N released during 125 days. CH4 flux was positively correlated with milk vetch substitution ratio, while it was negative correlated with N2O flux. Compared with 0% substitution, 25% substitution decreased global warming potential (GWP) and greenhouse gas intensity (GWP per unit of grain yield) by 12.1% and 10.3%, respectively, while 100% substitution increased GWP and greenhouse gas intensity by 38.4% and 65.2%, respectively. The results showed that soil pH, NH4+-N and redox state were significantly correlated with CH4 emission, while C and N remaining in the incorporated milk vetch residue and NH4+-N were key factors regulating N2O emission. It could be concluded that replacing 25% of urea-N with milk vetch was most effective in greenhouse gas mitigation while maintaining rice yield.