Sole Chemical Fertilizer Research Articles

Long-Term Impact of Crop Diversification and Nutrient Management on Soil Phosphorus Pools in Indo-Gangetic Plain

ABSTRACT Understanding the dynamics of soil phosphorus (P) over extended periods of soil and crop management practices is essential for sustainable P management. This study assessed the impact of four crop rotations [maize-wheat (M-W), maize-wheat-mungbean (M-W-Mb), maize-wheat-maize-chickpea (M-W-M-C), and pigeonpea-wheat (P-W)] each with three levels of nutrient management [control (CT), integrated nutrient management (suboptimal fertilizer+ farmyard manure + crop residue + bio-fertilizers; INM), and sole-chemical fertilizers (CF)] on soil inorganic and organic P (Pi and Po) pools and crop–soil relationships at the end of 15-year cropping. Legume-inclusive rotations resulted in higher labile-P pools, being higher with M-W-M-C and P-W. M-W-M-C rotation had higher moderately labile organic P (Po) in both surface (+23%) and subsurface (+18%) depths over M-W. Di-calcium P (Ca2-P) (+6%) and microbial biomass P (MBP) (+46%) increased in M-W-Mb over M-W, while iron-P (Fe-P) was reduced (−12%) in subsurface soil. INM enhanced bioavailable-P [soluble-P (+17%), labile-Pi (+15%) labile-Po (+12%), MBP (+96%), moderately labile-Po (+22%)] over CF in surface soil, while CF had a higher Fe-P (+16%). Legumes in rotation caused notable changes in the surface-to-subsurface ratio (SSBR) of Ca2-P (1.18–1.50) and occluded-P (1.64–2.78). INM had a higher SSBR of labile-P pools but had a lower SSBR of occluded-P facilitating mobilization of the later in the surface. Hence, in tropical soils, legume-inclusive diversification (particularly with chickpea) and INM involving crop residue recycling could be a sustainable option to improve P use efficiency, crop productivity, and save fertilizer resources.

Effect of Mild Organic Substitution on Soil Quality and Microbial Community

Mild organic substitution is advantageous for sustainable agricultural development. In order to determine the proper fertilization strategy, it is essential to investigate the impact of substituting chemical fertilizers with varying levels of organic manure on soil nutrients, microbial communities, and crop productivity. Four treatments were implemented: no fertilizer, sole chemical fertilizer, 20% organic manure substitution, and 40% organic manure substitution. Bacterial and fungal communities were characterized through high-throughput sequencing of the 16S rRNA gene V3–V4 region and the V4 region, respectively. The 20% and 40% organic manure substitutions increased soil organic matter (SOM) content, total nitrogen (TN) content, and reduced soil pH compared to the control (CK). The 20% organic manure substitution showed the most significant improvements in soil alkaline phosphatase, urease, and invertase activities. Soil nutrient enhancement increased bacterial alpha diversity, with a milder impact on fungal alpha diversity compared to bacteria. Different fertilization treatments elevated the relative abundance of bacterial Bacteroidetes (8.11%, 21.25%, and 1.88%), Actinomycetes (12.65%, 26.36%, and 15.33%), and fungal Ascomycota (16.19%, 10.44%, and 12.69%), known for degrading recalcitrant organic matter. The sole chemical fertilizer treatment increased the pathogenic Cheatotryiales. Shared species, primarily from bacterial Actinomycetes, Firmicutes, Proteobacteria, and fungal Ascomycota phyla, were found at 20% and 40% organic manure substitution levels. Specifically, the 20% organic manure substitution level promoted the relative abundance of beneficial plant growth-promoting taxa, Oxalobacteraceae and Massilia, and suppressed pathogens, with an increase in the relative abundance of the Purpureocillium genus and Mortierellomycota. These findings suggest that a 20% OF substitution can maintain crop yield, enhance soil nutrients and enzyme activities by fostering beneficial soil bacteria, inhibiting soil-borne pathogens, and refining microbial community structure.

Biomass ash as soil fertilizers: Supercharging biomass accumulation by shifting auxin distribution

Growing quantities of biomass ashes (phyto-ashs) are currently produced worldwide due to the increasing biomass consumption in energy applications. Utilization of phyto-ash in agriculture is environmentally friendly solution. However, mechanisms involving the coordination of carbon metabolism and distribution in plants and soil amendment are not well known. In the present study, tobacco plants were chemically-fertilized with or without 2‰ phyto-ash addition. The control had sole chemical fertilizer; for two phyto-ash treatments, the one (T1) received comparable levels of nitrogen, phophorus, and potassium from phyto-ash and fertilizers as the control and another (T2) had 2‰ of phyto-ash and the same rates of fertilizers as the control. Compared with the control, phyto-ash addition improved the soil pH from 5.94 to about 6.35; T2 treatment enhanced soil available potassium by 30% but no difference of other elements was recorded among three treatments. Importantly, bacterial (but not fungal) communities were significantly enriched by phyto-ash addition, with the rank of richness as: T2 > T1 > control. Consistent with amelioration of soil properties, phyto-ash promoted plant growth through enlarged leaf area and photosynthesis and induced outgrowth of lateral roots (LRs). Interestingly, increased auxin content was recorded in 2nd and 3rd leaves and roots under phyto-ash application, also with the rank level as T2 > T1 > control, paralleling with higher transcripts of auxin synthetic genes in the topmost leaf and stronger [3H]IAA activity under phyto-ash addition. Furthermore, exogenous application of analog exogenous auxin (NAA) restored leaf area, photosynthesis and LR outgrowth to the similar level as T2 treatment; conversely, application of auxin transport inhibitor (NPA) under T2 treatment retarded leaf and root development. We demonstrated that phyto-ash addition improved soil properties and thus facilitated carbon balance within plants and biomass accumulation in which shifting auxin distribution plays an important role.

Improving Pea Growth and Nutrient Efficiency in Calcareous Soils through the Synergy of Organic Amendments and Chemical Fertilizers

Introduction Soil fertility in Pakistan is hindered by insufficient and unstable organic matter, leading to stagnation and a decline in overall agricultural productivity. Methodology A pot study was conducted in 2018-19 comprised of four treatments including T1 = Recommended NPK fertilizer, T2 = NPK+FYM, T3 = NPK + Poultry manure, and T4 = NPK + Plant residue based on Complete Randomized Design (CRD) and was replicated thrice. Result The results exhibited significant differences in peas’ growth, yield, and nutrient use efficiency across the organic amendments. Among them, the higher plant height (70.63 cm), pod length (9.37 cm), and pod yield (158.63 g pot-1) was observed in T3 followed by T2. Regarding nutrient concentration and uptake, both T2 and T3 treatments elevated leaf tissue levels of N (4.76% and 5.03%), P (1.01% and 0.98%), and K (2.27% and 2.31%). These values were statistically comparable, accompanied by higher but non-significant P uptake (0.61 and 0.67 g pot-1) and K uptake (1.13 and 1.21 g pot-1) for the respective treatments. Further, higher nitrogen, phosphorus, and potassium use efficiency (49.4, 5.20, and 42.0%) were recorded in T3 followed by T2. Together with that significantly positive correlation between soil properties and pod yield was found which reflects the nutrient-supplying power of soil under organic amendments. Conclusion Consequently, it is suggested that the joint utilization of organic additives of any source and chemical fertilizer is necessary for increasing yield and nutrient use efficiency over sole chemical fertilizer application in calcareous soils.

Long-term impact of legume-inclusive diversification and nutrient management practices on phosphorus dynamics in alkaline Fluvisol

An insight into the dynamics of soil phosphorus (P) pools with long-term cropping/management practices would help in designing efficient and sustainable management module(s). The study aimed to investigate the long-term impact of diversified rice-based rotations and variable nutrient management practices on the dynamic composition of P pools and their influence on systems’ base-crop productivity in an alkaline soil of Indo-Gangetic plain (Fluvisol). Treatments consisted of four rotations [rice–wheat (R–W), rice–wheat–mungbean (R–W–Mb), rice–wheat–rice–chickpea (R–W–R–C), rice–chickpea (R–C)] each with three nutrient treatments [control (CT), integrated nutrient management (INM), sole-chemical fertilizers (CF)]. Notably, R–C exhibited higher levels of bioavailable-P (soluble-P, Ca2-P, labile-Po), particularly in subsurface soil depth (0.2–0.4 m) compared to other rotations. Likewise, the inclusion of chickpea every alternate year (R–W–R–C) resulted in higher Ca2-P (40%), labile-Pi (15%), labile-Po (11%), and moderately labile Po (8%) compared to R–W rotation demonstrating an increased significance of chickpea in maintaining a favorable soil P regime in alkaline soil. Both R–C and R–W–R–C reduced the surface-to-subsurface depth ratio (SSBR) of soluble-P and Ca2-P while increasing the ratio for microbial biomass P. Even with a suboptimal fertilizer-P rate, INM significantly increased soluble-P (4–33%), labile-Po (13–17%), microbial biomass P (10–26%), moderately labile-Po (4–17%) compared to CF and exhibited higher SSBR values. Correlation analysis demonstrated the substantial influence of very-labile carbon, microbial and phosphatase activities on P availability. The treatment-induced changes in labile-P pools significantly influenced rice (base-crop) yields. In conclusion, chickpea-inclusive diversification and INM could be a sustainable approach to enhance P bioavailability and crop productivity in tropical rice soils.

Enhancing Soil Fertility and Elevating Pecan Fruit Quality through Combined Chemical and Organic Fertilization Practices

This study focused on 6-year-old ‘Pawnee’ pecan trees to elucidate the differential responses of physicochemical properties of orchard soil and pecan fruit quality when combining chemical and organic fertilizers. The aim was to unveil the mechanisms that underlie the effects of different fertilization treatments on soil fertility, soil enzyme activities, and pecan fruit quality. Four treatments were established: sole chemical fertilizer (CF; N:P2O5:K2O is 15:15:15), chemical fertilizer combined with cake fertilizer (CF+CC), chemical fertilizer combined with manure fertilizer (CF+M), and chemical fertilizer combined with cake and manure fertilizer (CF+CC+M). Measurements were taken to assess the soil nutrient content, soil enzyme activities, and fruit growth quality in some orchards under different fertilization treatments. The results revealed that the combined application could increase yield and enhance pecan quality. Among these, the CF+M+CC treatment demonstrated the most favorable outcomes, with the pecan kernel oil and unsaturated fatty acid contents reaching 72.33% and 97.54%, respectively. The combined fertilization treatments had no significant impacts on soil trace elements such as Mg, Cu, and Mn; however, it significantly increased the Available Phosphorus (AP), Total Nitrogen (TN), Soil Organic Matter (SOM) and S-ACP (soil acid phosphatase) activities. In summary, the combined application of chemical and organic fertilizers can significantly increase the soil nutrient content and enzyme activities in pecan orchards, to promote the enhancement of fruit quality and economic aspects.

Effect of Co-application of Different Biochars and Inorganic Fertilizers on the Growth and Yield of Okra (Abelmoschus esculentus L.)

To manage necessary amount of food for the growing world population, it is very important to maintain fertility of usual arable land as well as to bring problem soils including sandy soil under coverage of regular crop cultivation. In this context, biochar is a very promising option as soil conditioner and therefore, a plant growth trial in pot was operated at the net house of the Department of Agroforestry and Environmental Science, Sylhet Agricultural University, Sylhet to evaluate the influence of tea waste and sugarcane bagasse biochar on the morphology, yield and yield contributing traits of okra (Abelmoschus esculentus) in sandy soil. The experimental set-up was arranged following randomized complete block design with three replications under eight treatments. The treatments were: T0 (CK, Control, no amendment), T1 (CF, Chemical fertilizers), T2 (2.5 % TWB (tea waste biochar) + CF), T3 (5% TWB + CF), T4 (10% TWB + CF), T5 (2.5% SBB (sugarcane Bagasse biochar) + CF), T6 (5% SBB + CF); and T7 (10% SBB + CF). The results revealed that the different morphological characteristics like plant height (PH), number of leaf plant-1 (NLP), leaf length (LL), plant fresh weight (PFW), and stem diameter (SD) showed no significant difference among the treatments. The highest PH (107.33 cm) and RL (70.67 cm) were found in T0 (CK) whereas the maximum LL (27.33 cm), SD (10.38 mm), and fresh root weight (FRW) (19.67g) were noted in T3. The maximum number of leaves plant-1 (NLP) (20) and PFW (110.67 gm) of okra were observed in T2 and T6, respectively. In case of total leaf chlorophyll content (TLCC), the maximum value was determined in T4 (47 µmol m-2), but the treatments were not significantly different from each other. The number of pod plant-1 (NPP) (23.7), pod length (PL) (18 cm), individual pod weight (IPW) (18 g), number of seed pod-1 (NSP) (45) and pod weight per plant-1 (PWP)(425 g) of okra were found to be highest in T7, followed by T4 and T6. The yield and yield contributing characters of okra showed significantly higher value for biochar treatments (T2 - T7) over to the control (T0) and sole chemical fertilizer treatment (T1). After the cultivation of okra, the highest pH value (7.2) was found in T7, followed by T6. The results of this study might contribute to enlarge the prospects of biochar application in the production of okra and other crops in both normal and less fertile soils.

Effects of biochar produced from distiller grains on agronomic performances of sorghum (Sorghum bicolor L.) and greenhouse gas emissions from soil

Aromatic liquor breweries produce massive distiller grains containing a high percentage of rice husks that necessitate harmless treatment and resource utilization. These husk-rich distiller grains can be pyrolyzed in the Ni-based catalyst system at a relatively low temperature (480 °C) into combustible gas, which is used in liquor distillation, and biochar (BDG) with high mineral nutrients and good surface properties. A 3-year field experiment (2018–2020) was established to understand the effects of BDG on sorghum agronomic performances and greenhouse gas emissions from the soil. The results showed that BDG had higher mineral nutrient (N, P, K, and S) contents, larger cation exchange capacity, and better surface structure than those prepared using the traditional method at 400 and 600 °C. Compared with sole chemical fertilizer (CF), the combination of CF and BDG (CF+BDG) increased sorghum nutrient (N, P, and K) uptake, yield, fertilizer use efficiency, and economic benefit. Cumulative CO2 emission from the soil changed little between with and without BDG, indicating the microbial stability of BDG. The effective adsorption of NH3 or NH4+ by BDG upon N application may reduce N loss through NH3 and N2O emissions and increase the efficiency of fertilizer N use. Cumulative CH4 emission ranged from 32.45 to 44.86 g ha-1, which could be overlooked as a greenhouse gas in the sorghum field. Moreover, CF+BDG significantly decreased NH3 and N2O emissions for the production of each unit of sorghum grains and the CO2 emission from the land for the production of a certain amount of sorghum grains. Therefore, CF+BDG exhibited better agronomic and environmental performances in sorghum cultivation.

Investigating the effects of organic amendments on soil microbial composition and its linkage to soil organic carbon: A global meta-analysis

Understanding the dynamics of soil microbial communities responsible for soil element cycling is vital to understanding organic amendments' mechanisms in agricultural soil. However, several studies show inconsistencies in whether and how organic amendments affect the taxonomic composition of soil microbial communities compared to the application of sole chemical fertilizers. This first global meta-analysis demonstrated that organic amendments increased the bacterial diversity indices (Shannon and Chao1) but had no significant effect on fungal diversity indices. When considering both bulk and rhizosphere soils, only copiotrophic strategies such as Proteobacteria, Bacteroidetes, and Zygomycota phylum demonstrated a significant increase in response to organic amendments, mainly because the environment with a significant increase in nutrients content preferentially supports the growth of copiotrophic species after the use of organic amendments. Additionally, the factors influencing the response of different dominant microbial phyla to organic amendments varied. Besides soil pH, the effect of organic amendments on different microbial phyla was significantly influenced by soil texture, organic fertilizer type, crop type, and climate type, providing insights into the diverse responses of microbial communities to organic amendments under varying conditions. Organic amendments significantly increased soil organic carbon (SOC) content and enzyme activities related to nitrogen (N) and phosphorus (P) decomposition but had no significant effect on enzymes related to carbon (C) decomposition. Notably, the effect of organic amendments on the relative abundance of three dominant phyla (Mortierellomycota, Nitrospirae, and Firmicutes) was related to the effect on SOC, where the increase in the relative abundance of Firmicutes was significantly positively associated with the increase in SOC. This result has implications for understanding the relationship between the dynamics of microbial community composition and C turnover in agroecosystems.

Optimally combined application of organic and chemical fertilizers increases grain yield and improves rhizosphere microecological properties in rice ratooning

AbstractField tests were conducted at experimental station of Chongluo, Nanping city, Fujian province, China in 2018–2019 to explore the action and physiological mechanism of organic nitrogen in rice ratooning under the configurations with different proportions of organic and inorganic nitrogen. The results showed that sole chemical fertilizer (CF) led to a significant decrease in soil nutrient availability, especially at late growth stage, and reduced grain yield of the main and ratooning crops compared with the optimal fertilizer configuration (GM2) in 30% organic nitrogen with 70% chemical nitrogen fertilizer in the premise of total application rate at 225 kg N/ha. Further studies have revealed that GM2 relative to CF treatment promoted to produce more productive panicles of the main crop and had carryover effect on the regeneration rate of ratooning rice due to national C13‐assimilates partitioning in rice–rhizosphere systems, which resulted in increased soil microbial diversity and soil fertility, thereby enhanced yields of the main and ratooning rice crops. These findings help to better understand the action and mechanism of the proper combined application of organic and inorganic nitrogen fertilizer via improving remobilization of 13C assimilates in rice–rhizosphere system, and ultimately increasing grain yield in rice ratooning.

Effect of sterile rice spikelets derived biochar amendment on nutrient leaching and availability in paddy soil under continuous standing water

ABSTRACT Undisturbed soil columns were used to study the effect of sterile rice spikelets-derived biochar (SRSB) on NH4 +-N, available P, and available K leaching and nutrients availability in a paddy soil under continuous standing water (CSW) condition. The experiment was conducted for two crop cycles and comprised of three treatments: recommended dose of sole chemical fertilizers (CF), CF+SRSB (2 t ha−1), and control. In both crop cycles, incorporation of SRSB reduced the leachate NH4 +-N and available K concentrations, while increased the available P concentration compared to sole CF. The SRSB amendment reduced the cumulative losses of NH4 +-N by 35–38% and available K by 23–25% than CF only. However, there was no significant variation in cumulative available P loss between SRSB and CF only. The reduced leaching loss of NH4 +-N and available K could be attributed to the better nutrient adsorption capacity of SRSB. After completion of two crop cycles, the soil pH, soil organic carbon, soil total N, available P, and available K increased with SRSB amended soils than sole CF. This study showed positive effects of SRSB on retaining nutrients and increasing their availability in the soil which could benefit efficient fertilizer management in paddy soil under CSW.

Effect of bioslurry and chemical fertilizer on the agronomic performances of maize

The objective of this study was to determine the effects of bioslurry (BS) and chemical fertilizer (CF), as a sole BS and CF and their mixed application, on the agronomic performances of maize (Zea mays var. BH- 546). Field experiment was conducted at Hawassa University Research Farm, in the Sidama Region in Ethiopia. The experiment consisted of six treatments, arranged in a randomized complete block design with three replications. Relevant agronomic characteristics were recorded for each plot, from planting to harvest. Results show yield and yield characteristics of maize increased by both sole and combined application of fertilizers compared to no fertilizer application. The combined BS and CF application at the dose of 25% BS +75% CF gave the highest plant height (251.3 cm), grain yield (7.09 t ha−1), biomass yield (24.4 t ha−1) and stover yield (11.5 t ha−1). The agronomic performances generally increased with increasing proportion of chemical fertilizer in the combined application until the proportion of bio-slurry reaches 75%. Moreover, the combined application generally tended to increase the agronomic performance better than the sole application of both BS and CF. In addition to improving the agronomic performances; both sole BS and its combination with CF reduce the cost of chemical fertilizers. In conclusion, the combined BS and CF application at the dose of 25% BS +75% CF appears an optimal combination and rate for the production of maize in the study area. Yet, as this finding is only one season, further studies determining the optimum dose of sole BS, sole CF, and combined CF and BS for improved maize agronomic performance is commendable in future research.

Effects of organic manure and chemical fertilizers on growth and yield of garden pea

An experiment was conducted at Agronomy Farm of Bangladesh Agricultural University, Mymensingh (BAU) during rabi season of 2018−19 to see the response of garden pea to manure and fertilizers. The treatments were T1: Control (no fertilizer or manure), T2: Cowdung + Poultry manure + Mustard oilcake, T3: Vermicompost + Poultry manure + Mustard oilcake, T4: Urea + TSP + MoP + Gypsum and T5: Cowdung + Urea + TSP + MoP + Gypsum. The experiment was designed in a factorial Randomized Complete Block Design (RCBD) with 4 replications. Urea, TSP, MoP and gypsum @ 45, 90, 40 and 50 kg ha−1 were used as sources of nitrogen, phosphorous, potassium and sulphur, respectively. Cow dung, poultry manure, vermicompost and mustard oilcake were applied @ 30, 25, 2.5 and 0.025 t ha−1, respectively. The results showed that the treatment T5 significantly gave the highest values of vegetative growth and yield attributing characters’ i.e., plant height, number of branches per plant, number of pods per plant, pod length, pod breadth, number of seeds per pod, 100-seed weight, pod weight, pod yield and seed yield per hectare. The lowest values of growth and yield attributing characters were recorded with T1. Sole chemical fertilizers (T4) showed better performances than T2 and T3. Treatment T5 gave higher result than T4. So, for obtaining the highest growth and pod yield of pea (cv. BARI Motor3), treatment T5 (Cowdung + Urea + TSP + MoP + Gypsum @ 30 t ha−1, 45-90-40-50 kg ha−1) could be the best combination. Bangladesh J. Agri. 2022, 47(1): 121-129

Role of Integrated Nutrient Management on Oat: A Review

Food security and environmental safety are the two important areas receiving major setback with the use of chemical fertilizers. Sustainable food supply in response to population demand urges for a paradigm shift from chemical-based agriculture to some eco-friendly approaches. Integrated nutrient management or combined approach of using different sources of nutrients is relevant in this context as it optimisez profitable crop production and improves soil health without deteriorating environment further. Food supply not only comes from agriculture but also from livestock sector. Therefore, cultivation of dual purpose (food and fodder) crop like oat is gaining importance day by day. Adequate nutrition to oat directly reflects on livestock and human nutrition. Researches around the globe indicate that integrated nutrient management in oat is now gaining momentum as it holds good promise as a successful replacement of sole chemical fertilizer. However, poor extension service and lack of policies make this technology to remain as a dormant. Therefore, further research works regarding integrated nutrient management on oat and its true transfusion to farming community are the needs of the hour to protect livestock and human food security and to free the environment from clutches of chemical hazards in coming days.

Different Combinations Of Biochar And Urea As A Nitrogen Source: Effect On Growth, Tuber Quality, And Yield Of Potato

Field research was carried out to examine the biochar effect on growth, tuber quality, and yield of the potato crop. Treatments were laid out in a randomized complete block design with 7 treatments of different combinations of biochar and urea (BC100%, BC80%+Urea20%, BC60%+Urea40%, BC40%+Urea60%, BC20%+Urea80%, Urea100%, BCC) as nitrogen source with 4 replications, where all treatments supply recommended dose of fertilizer except control treatment (BCC). The tested variety of potato was Janakdev. The recorded observations showed that biochar mixed with chemical fertilizer had a significantly superior effect on growth (height, branches number, canopy), marketable tuber weight and number, tuber size, yield, and dry matter % as compared to sole biochar (BC100%), sole chemical fertilizer (Urea100%), and control (BCC) treatments. Among the treatments, BC40%+Urea60% (Biochar applied @ 10 t/ha) had resulted significantly higher marketable tuber weight and number, tuber size, yield, and dry matter %. Our results thus demonstrate that the application of chemical fertilizer in combination with biochar could effectively enhance the plant growth, tuber quality, and yield of the potato crop.

Periodic changes in carbon and nitrogen in Vertisols under organic, inorganic, and integrated nutrient management

An experiment with seven treatments and three replications was established in a completely randomized design to assess the effect of gliricidia green leaf manuring on the mineralization of nitrogen and carbon in the soil during kharif 2014-15 in Dr. Panjabrao Deshmukh Krishi Vidyapeeth’s Department of Soil Science and Agricultural Chemistry, Akola. The seven treatments comprised absolute control, two treatments of sole chemical fertilizers, two treatments of sole organics, and two treatments of integrated application of chemical fertilizers and gliricidia green leaves. The periodical (15 days interval) mineralization of nitrogen in the form of ammoniacal and nitrate nitrogen and carbon in the form of organic carbon and permanganate oxidizable carbon in soil were studied. The results indicate that the higher mineralization of nitrogen and carbon was recorded up to 45 days of incubation and it declined at subsequent (60 and 75 days) intervals, indicating that more than 60% of mineralization took place up to 45 days of incubation. Further, the higher mineralization of nitrogen and carbon was observed with the application of 50% RDN(Gl) + 50% N(Inorg) + 100% P + 25 kg K ha-1 (T7), followed by 50% RDN(Gl) + 50% N(Inorg) + 100% P (T6) and 100% NPK(T3).

Nutrient management may reduce global warming potential of rice cultivation in subtropical India

Agricultural practices contribute to greenhouse gas (GHG) emissions; therefore, it is essential to modify the production technologies. We analyzed decadal variation in CO2 and CH4 over a major rice cultivating area in subtropical India using GOSAT satellite data, which shows a sturdy increase. Furthermore, we carried out long-term field experiments with different nutrients management in the research farm to validate CERES–Rice (Crop Environment Resource Synthesis) and DNDC (De-nitrification and Decomposition model) models. The variations in Global warming potential per kg rice grain production over 90 years (2005–2095) are also projected. This study used a simulation technique to predict the rice yield using CERES–Rice and GWP using the DNDC model for three varied nutrient management treatments: chemical fertilizer (CF) at full (100%) recommended level (CF100), organic fertilizer using vermicompost at full recommendation (VC100), and integration of organic and chemical fertilizer (VC50 + CF50). The CF100 treatment showed the highest rate of increase in GWP as 0.014 and 0.021 kg CO2eq kg-grain season−1 in RCP 4.5 and 8.5 scenarios, respectively. Integrating organic fertilizers with chemical fertilizers may give a nearly similar yield in later decades of the century in both RCP 4.5 and 8.5 climate scenarios with substantial reductions (77% in RCP 4.5 and 66% in RCP 8.5) in the rate of change in GWP as compared to sole chemical fertilizer application. This study recommends integrated nutrient management using organic fertilizers as a feasible way to limit the GHG emission from rice fields and minimize global warming in future climate scenarios.

Deciphering microbial mechanisms underlying soil organic carbon storage in a wheat-maize rotation system

A link between microbial life history strategies and soil organic carbon storage in agroecosystems is presumed, but largely unexplored at the gene level. We aimed to elucidate whether and how differential organic material amendments (manure versus peat-vermiculite) affect, relative to sole chemical fertilizer application, the link between microbial life history strategies and soil organic carbon storage in a wheat-maize rotation field experiment. To achieve this goal, we combined bacterial 16S rRNA gene and fungal ITS amplicon sequencing, metagenomics and the assembly of genomes. Fertilizer treatments had a significantly greater effect on microbial community composition than aggregate size, with soil available phosphorus and potassium being the most important community-shaping factors. Limitation in labile carbon was linked to a K-selected oligotrophic life history strategy (Gemmatimonadetes, Acidobacteria) under sole chemical fertilizer application; defined by a significant enrichment of genes involved in resource acquisition, polymer hydrolysis, and competition. By contrast, excess of labile carbon promoted an r-selected copiotrophic life history strategy (Cytophagales, Bacillales, Mortierellomycota) under manure treatment; defined by a significant enrichment of genes involved in cellular growth. A distinct life history strategy was not observed under peat-vermiculite treatment, but rather a mix of both K-selected (Acidobacteria) and r-selected (Actinobacteria, Mortierellomycota) microorganisms. Compared to sole chemical fertilizer application, soil organic carbon storage efficiency was significantly increased by 26.5% and 50.0% under manure and peat-vermiculite treatments, respectively. Taken together, our results highlight the importance of organic material amendments, but in particular a one-time peat-vermiculite application, to promote soil organic carbon storage as a potential management strategy for sustainable agriculture.

Water management and soil amendment for reducing emission factor and global warming potential but improving rice yield

Alternate wetting and drying (AWD) for growing rice improves water productivity (WP), minimize methane emission and net ecosystem carbon balance (CO2), but might be responsible for increased nitrous oxide emissions. The combined effects of water management and different organic manure application on methane emission, carbon dioxide and nitrous oxide fluxes, emission factor (EF) and WP are not well documented, which has been evaluated during dry seasons of 2018 and 2019. AWD and continuous flooding (CF) were imposed in NPKSZn, cowdung (CD), poultry manure (PM) and vermicompost (VC) treated plots. Closed chamber techniques were used for determining emissions of greenhouse gases. In comparison with CF, the AWD significantly reduced total GWP by 15–44% depending on soil amendments and 2–29% net ecosystem carbon balance (CO2); but additional N2O contribution to GWP was about 0.61–1.18% compared to sole chemical fertilizer treatments. Depending on soil amendments, the AWD reduced EF of CH4 (22–36%) but increased WP by 25–27% compared to CF system along with 14–43% reduction in GHG intensity (GHGI). Vermicompost treatment had the lowest GHG emission, GWP, EF and GHGI than cowdung, poultry manure under both irrigation methods. Rice yield varied because of soil amendments but not with irrigation methods. Use of vermicompost improved soil organic carbon (SOC) storage significantly than cowdung and poultry manure. In conclusion, AWD practice and amendment of rice soil with vermicompost could be an effective strategy for reducing GHG emission, GWP, EF and GHGI without sacrificing rice yield.

Tillage-mulch-nutrient interaction effect on N, P and K balance in soil and plant uptake in maize-black gram cropping system in an acid soil of North Bengal

Field experiments were conducted to evaluate tillage-mulch-nutrient (partial replacement of inorganic with organic) interaction through soil conservation techniques in maize-black gram rotation. The nutrient balance was positive for nitrogen (N) and potassium (K), but was negative for phosphorus (P). Larger negative P balances were recorded in all the treatments with vermicompost over sole chemical fertilizer treatments. Net negative balance diminished over years in organic manure treatments, but increased with sole chemical fertilizers, indicating that with the passage of time, P may slowly became available in acid soils of north Bengal.