Application Of Organic Amendments Research Articles

Organic amendments improved soil properties and native plants’ performance in an Australian degraded land

Context Land degradation poses a substantial threat to both the sustainable environment and human health. Efforts towards rehabilitation and remediation often require addition of soil amendments and careful selection of plant species. Aims We assessed the effect of recycled organic amendments on improvement of soil physicochemical properties and performance of native plant species in an Australian degraded soil. Methods A glasshouse pot experiment investigated the effects of compost (CO), biochar (BC), and compost-biochar (COBC) mixture on performance of three native Australian plant species (Eucalyptus tereticornis (EU), Acacia leiocalyx (AC), and Banksia integrifolia (BA)) in a degraded soil. Key results Application of CO, BC, and COBC organic amendments increased soil dissolved organic carbon and microbial biomass carbon contents compared to the control treatment. COBC amendment increased nutrient retention and reduced CO2 emissions compared to CO amendment. BC amendment also resulted in low CO2 emissions similar to the control treatment, where no significant differences were observed. AC outperformed the EU and BA species in biomass production due to its leguminous nature, with amendment application had an insignificant effect on AC performance. Within the EU treatments, the COBC:EU demonstrated the highest biomass production, followed by CO:EU, BC:EU, and CK:EU, respectively. Conclusion All amendments exhibited overall improvements in soil and plant parameters, with more significant outcomes observed with COBC application. However, the observed improvements from biochar application were minimal in this short-term experiment, which may not have allowed for the manifestation of long-term benefits. Implications Further research is warranted to investigate the effects of compost and biochar amendments on diverse soil types and native plant species.

A Comprehensive Perception of Biological Control Potential of Endophytes and Quality Refinement of Lagenaria siceraria.

Agriculture and livestock management practices known as organic farming rely more on internal processes than external inputs. Natural environments depend heavily on diversity, and organic farming incorporates both the stated purpose of fostering diversity as well as the use of diversity as a management tool. A more complete understanding of agriculture in terms of agro-ecology has begun to be questioned by the traditional reductionist approach to the study of agriculture. Therefore it is necessary to be aware more about the significance of microbes in processes including soil growth, plant nourishment, and the eradication of plant disease, pest, and weeds. In this study, fluorescent Pseudomonas strain (EFP56) and Trichoderma harzianum were studied for antifungal and antibacterial activity against four common root rot fungi and four common laboratory bacteria in vitro experiments. Furthermore, soil-borne disease surveillance and nutritional quality of Lagenaria siceraria, fluorescent Pseudomonas strain (EFP56) and Trichoderma harzianum were combined with neem cake and cotton cake to check their efficacy. Through the application of organic soil amendments in combination with biocontrol agents improved the quality of vegetables and their nutritional value by raising their polyphenol, carbohydrate, and protein content as well as enhancing antioxidant scavenging status. The experiments were conducted in pots and in fields to confirm their efficacy rate. The final outcomes also revealed greater induction of defense system, disease lessening and enriched fruit quality. Consortium of neem cake and cotton cake with bio-stimulants can regulate biotic as well as abiotic stress.

Organic Phosphorus Fractions in Relation to Soil Aggregate Fractions of Black Soil

Knowledge of long-term phosphorus behavior is essential to improve soil structure, nutrient supply potential, and the sustainability of cropping systems. A 45-year long-term experimental trial was used to observe organic phosphorus fractionation and its effects on soil aggregation and nutrient distribution at three depths (0–20, 20–40, and 40–60 cm) in Vojvodina Province, Serbia, under maize monoculture and maize/barley rotation. Five fertilizing systems were studied, including Control, NPK, NPK + maize remains, NPK + manure, and NPK + manure in rotation. Soil aggregates were fractionated into four size categories (>2000, 2000–250, 250–53, and <53 μm) using a wet sieving method. The samples were analyzed for main indicators, including different forms of phosphorus, total and available (PT and PA), as well as its organic forms (Labile Po, Biomass Po, Mod. Labile Po, Fulvic acid Po, Humic acid Po, and Resistant Po), and other fertility parameters. Significant differences in total and available phosphorus as well as all observed organic phosphorus fractions were evident between treatments with and without organic amendments, particularly in the 0–20 and 20–40 cm soil layers. Moderately labile P forms were dominant across all treatments, while labile forms constituted a smaller proportion. The most notable differences between treatments were observed in the labile and moderately labile forms, as well as in the resistant form of organic phosphorus. Manure application led to increased nutrient content in macroaggregates (>250 μm) compared to microaggregates. Microaggregates (<250 μm) were predominant across all depths, while stable structural aggregates did not show a significant increase after manure application. PCA highlighted significant correlations between soil characteristics, including total and available P, total organic carbon, clay content, and enzyme activity, across different aggregate sizes and organic P fractions. Overall, long-term mineral fertilization combined with organic amendment application induced variations in phosphorus fractions and the content of carbon, nitrogen, and phosphorus associated with aggregates in the first two soil layers, except for aggregate size classes.

Degradation Rate/Vulnerability Potential and Fertility Status of Luvisols in the Mandara Mountains (Far-North Cameroon).

Soil degradation emerges as one of the major problems in the locality of Sir in the Mandara Mountains, Far-North Cameroon. Inappropriate agricultural techniques resulting in land use change affect soil functions and seriously harm forest ecosystems. This study was conducted to analyse the current character of soils and access their degradation and their level of fertility. Twenty soil samples were taken at 15 cm depth. This includes ten in the plot under forest reserve and ten others in the plot under cultivation. Cultivation is responsible for the increase in bulk density (BD) (1.59 to 2.23 g/cm3), Mg (4.76 to 6.40 cmol·kg-1), Ca (10.44 to 11.26 cmol·kg-1), P (7.93 to 9.93 g/kg), and Mg/K (2.28 to 5.84) and decrease in CEC (38 0.15 to 31.46 cmol·kg-1), OM (2.76 to 1.08%), OC (1.66 to 0.62%), total nitrogen (0.08 to 0.05%), K (4.59 to 1.15 cmol·kg-1), Na (1.32 to 0.91 cmol·kg-1), C/N (25.69 to 13.86), and Ca/Mg (2.32 to 1.89). This variability in physicochemical properties reflects progressive soil degradation. Cultivated soils are subject to severe degradation or potential vulnerability (SDR/Vp = 4/2) due to texture, organic carbon, soil aggregate stability, sealing index, and total nitrogen. On the other hand, soils under forest reserve are subject to severe degradation or vulnerability due to the total nitrogen and sodium absorption ratio. The soils of the study area are subject to severe and extreme potential degradation or vulnerability due to BD, respectively, under forest reserve and cultivation. Two classes of fertility were identified: class II (plots under forest reserve) having a good level of fertility, characterized by good physical properties and severe limitations in nitrogen and phosphorus and class IV (cultivated plots) with a low level of fertility due to severe limitations in organic matter, phosphorus, and poor physical characteristics. The best indicator of the good quality of the luvisols of Sir is the pH, while the bulk density is an indicator of severe to very extreme degradation or high to very high vulnerability. The application of organic and mineral amendments is essential for raising the organic matter and nitrogen and phosphorus contents in these soils.

Straw application improved soil biological properties and the growth of rice plant under low water irrigation

The application of organic amendments is one way to manage low water irrigation in paddy soils. In this 60-day greenhouse pot experiment involving paddy soil undergoing drying-rewetting cycles, we examined the effects of two organic amendments: azo-compost with a low carbon to phosphorus ratio (C:P) of 40 and rice straw with a high C:P ratio of 202. Both were applied at rates of 1.5% of soil weight (w/w). The investigation focused on changes in certain soil biochemical characteristics related to C and P in the rice rhizosphere, as well as rice plant characteristics. The irrigation regimes applied in this study included constant soil moisture in a waterlogged state (130% water holding capacity (WHC)), mild drying–rewetting (from 130 to 100% WHC), and severe drying–rewetting (from 130 to 70% WHC). The results indicated that the application of amendments was effective in severe drying–rewetting irrigation regimes on soil characteristics. Drying–rewetting decreased soil respiration rate (by 60%), microbial biomass carbon (by 70%), C:P ratio (by 12%), soil organic P (by 16%), shoot P concentration (by 7%), and rice shoot biomass (by 30%). However, organic amendments increased soil respiration rate (by 8 times), soil microbial biomass C (51%), total C (TC) (53%), dissolved organic carbon (3 times), soil available P (AP) (100%), soil organic P (63%), microbial biomass P (4.5 times), and shoot P concentration (21%). The highest significant correlation was observed between dissolved organic carbon and total C (r= 0.89**). Organic amendments also increased P uptake by the rice plant in the order: azo-compost > rice straw > control treatments, respectively, and eliminated the undesirable effect of mild drying–rewetting irrigation regime on rice plant biomass. Overall, using suitable organic amendments proves promising for enhancing soil properties and rice growth under drying–rewetting conditions, highlighting the interdependence of P and C biochemical changes in the rhizosphere during the rice vegetative stage.

Inorganic carbon accumulation in saline soils via modification effects of organic amendments on dissolved ions and enzymes activities

Organic amendments are effective in promoting salt leaching, improving availability of nutrients and increasing crop yield in saline soils. However, the effects of the combined application of organic amendments on soil inorganic carbon (SIC) content and its driving mechanisms are unknown. We examined how changes in soil biochemical properties including moisture content, pH value, dissolved ions, soil organic C (SOC), dissolved organic C (DOC), microbial biomass C (MBC), and activities of C- and N-related enzyme due to applying (i) only mineral fertilizers (control; Ctrl) or mineral fertilization in combination with (ii) manure (M); (iii) biofertilizer plus manure (B+M); and (iv) humic acid plus manure (HA+M) modify SIC pool over three years. Organic amendments increased the content of Ca2+ and HCO3– ions, but significantly decreased Na+, Cl−, and SO42− at 0–60 cm soil layers compared to Ctrl. Furthermore, the activities of β-glucosidase (BG), Xylanase (BX), Cellobiosidase (CE), and β-1,4-N-Acetyl-glucosaminidase (NAG) increased at 0–40 cm soil. Partial least squares path model manifested that organic amendment directly accumulated SIC content by increasing Ca2+ content and the activities of BX and NAG. Additionally, the decrease of Cl− contents under organic amendments favored the increase of MBC and SOC content, which further increased SIC content. Generally, the effects of HA+M were greater than other fertilization managements, which increased the stocks of SIC and total C at 0–60 cm soils by 27 Mg ha−1 and 47 Mg ha−1, respectively. Furthermore, the effect of organic amendments on SIC content is more pronounced below the first 20 cm. Thus, the application of organic amendments is recommended as an appropriate measure to not only improve soil condition for plant growth and SOC accumulation but also to store C as SIC at deeper depths.

Sulfur dynamics in saline sodic soils: The role of paddy cultivation and organic amendments

The phenomenon of sulfur (S) deficiency in Chinese soil is becoming increasingly severe, especially in the northeastern saline-sodic wasteland (WL). To determine the bioavailability of S in long-term cultivated paddy soil with or without organic amendment addition, the long-term field experiment site was established and incubation experiments were conducted. Compared to WL, soil properties have been continuously improved during the 15-year paddy field (PF) cultivation, ultimately enhancing the content of soil organic carbon (by 242.62 %), total nitrogen (by 126.49 %) and alkali-hydrolyzed nitrogen (by 28.07 %). Additionally, soil salinization has been decreasing, and the stock of total sulfur (TS) and available sulfur (AS) in the 0–60 cm soil layer have increased by 32.09 % and 293.52 % respectively. In contrast, organically-amended soil (OA) manifested superior TS and AS levels vs. PF. Additionally, water-soluble sulfur (WSS) was markedly elevated, registering post-annual increments of 227.31 % and 268.36 % in PF and OA, respectively, relative to WL. The key mechanistic impetus for the application of organic amendments was the enhancement of the soil's adsorptive and mineralization capabilities. As observed in our soil culture experiment, the maximum adsorption of sulfate ions and the cumulative mineralization of sulfur in the soil follow the pattern of OA > PF > WL. The Partial Least Squares Path Model (PLSPM) corroborated that both organic amendments and years of cultivation indirectly influenced total inorganic sulfur fractions. This influence is primarily mediated via structural soil enhancements and salinization amelioration, thereby elevating available quantities of sulfur in saline-sodic soil environments. In conclusion, from the perspective of soil sulfur biogeochemical cycling, we have confirmed that reclaiming saline-sodic wasteland for paddy field could be a beneficial and sustainable approach for soil management. These findings of this study can also provide an in-depth understanding of the bioavailability and influencing mechanism of sulfur in long-term saline-sodic paddy fields.

Enhancing crop productivity and resilience by promoting soil organic carbon and moisture in wheat and maize rotation

Soils with high organic carbon (SOC) have been shown to enhance crop yields while minimizing climate-induced losses. However, the resilience impacts and mechanisms by which high SOC enhances crop performance have not been fully explored. Here, eight-year rotations of winter wheat and summer maize managed with chemical fertilizer input alone (CF) or with cattle manure (OM) or with peat and vermiculite (PV) were conducted, and various soil properties were measured alongside crop growth, nitrogen (N) uptake, and grain yield, with seasons categorized as dry or normal based on precipitation amounts. The OM and PV treatments increased SOC by 57% and 78% relative to the CF, respectively, and improved soil nutrient availability and the soil quality index. Soil moisture content in the 0–30 cm layer increased by 3.5–26.6%, but was less influenced in the 30–90 cm soil layers. Annual yield of wheat plus maize increased by 13% and 12% in OM and PV compared to the CF, and the yield sustainability index increased by 29% and 17%. Yield gains were more pronounced in dry compared to normal seasons, ranging from 19% to 28% and 12–15% for wheat. At least in part, the relative advantages of OM and PV treatments under drying conditions were associated with accelerated growth and N uptake rate from sowing to stem elongation for wheat and maize. Among the factors influencing yield in the present study, soil moisture exerted the greatest positive total effect on yield. Overall, the results highlight that enhanced SOC resulting from combined application of organic amendments and mineral fertilizer was positively associated with yield by promoting soil quality and water availability, with a more pronounced benefit under water-limited conditions.

Comparison of the Effects of Different Organic Amendments on the Immobilization and Phytoavailability of Lead

Organic materials, such as straw, animal manure, and their processed product biochar, are known to exhibit agronomic effects and the ability to remediate heavy metal contamination. However, knowledge regarding the relative effects of different organic amendments in soils on heavy metal immobilization and phytoavailability remain limited. Consequently, the effects of maize straw (MS), chicken manure (CM), mushroom cultivation waste (MW), and sawdust biochar (SB) on the immobilization and phytoavailability of lead (Pb) in wheat plants were investigated in this study using pot experiments. The results showed that the artificial application of Pb reduced soil pH, while increasing the total organic carbon (TOC) and cation exchange capacity (CEC) to various extents. Furthermore, the Pb treatment increased the adsorption of Pb by wheat grains (0.83 mg∙kg−1), resulting in decreased above-ground dry biomass (43.16 g∙pot−1) during the maturity growth period when compared with the control check (CK) treatment. The MS + Pb and CM + Pb treatments increased the exchangeable Pb fractions in the soil, but had a limited effect on Pb accumulation in wheat grains compared with the Pb treatment. In contrast, the SB + Pb treatment effectively increased soil pH and TOC, while decreasing the fraction of exchangeable Pb forms and increasing the oxidizable and residual Pb fractions, compared with the Pb treatment. Moreover, the MW + Pb treatment also increased the soil pH and CEC, displaying the potential to increase soil TOC, in addition to substantially modifying the portioning of Pb from exchangeable forms to less bioavailable fractions. Both the MW and SB amendments significantly reduced Pb concentrations in wheat grains (0.49 and 0.70 mg∙kg−1,∙respectively), resulting in increased above-ground dry biomass (51.59 and 54.12 g∙pot−1, respectively). In summary, the application of organic amendments, especially MW, could be an effective measure for enhancing Pb immobilization in polluted soils, thereby reducing its uptake and translocation to crops.

Greenhouse gas emissions, carbon stocks and wheat productivity following biochar, compost and vermicompost amendments: comparison of non-saline and salt-affected soils

Understanding the impact of greenhouse gas (GHG) emissions and carbon stock is crucial for effective climate change assessment and agroecosystem management. However, little is known about the effects of organic amendments on GHG emissions and dynamic changes in carbon stocks in salt-affected soils. We conducted a pot experiment with four treatments including control (only fertilizers addition), biochar, vermicompost, and compost on non-saline and salt-affected soils, with the application on a carbon equivalent basis under wheat crop production. Our results revealed that the addition of vermicompost significantly increased soil organic carbon content by 18% in non-saline soil and 52% in salt-affected soil compared to the control leading to improvements in crop productivity i.e., plant dry biomass production by 57% in non-saline soil with vermicompost, while 56% with the same treatment in salt-affected soil. The grain yield was also noted 44 and 50% more with vermicompost treatment in non-saline and salt-affected soil, respectively. Chlorophyll contents were observed maximum with vermicompost in non-saline (24%), and salt-affected soils (22%) with same treatments. Photosynthetic rate (47% and 53%), stomatal conductance (60% and 12%), and relative water contents (38% and 27%) were also noted maximum with the same treatment in non-saline and salt-affected soils, respectively. However, the highest carbon dioxide emissions were observed in vermicompost- and compost-treated soils, leading to an increase in emissions of 46% in non-saline soil and 74% in salt-affected soil compared to the control. The compost treatment resulted in the highest nitrous oxide emissions, with an increase of 57% in non-saline soil and 62% in salt-affected soil compared to the control. In saline and non-saline soils treated with vermicompost, the global warming potential was recorded as 267% and 81% more than the control, respectively. All treatments, except biochar in non-saline soil, showed increased net GHG emissions due to organic amendment application. However, biochar reduced net emissions by 12% in non-saline soil. The application of organic amendments increased soil organic carbon content and crop yield in both non-saline and salt-affected soils. In conclusion, biochar is most effective among all tested organic amendments at increasing soil organic carbon content in both non-saline and salt-affected soils, which could have potential benefits for soil health and crop production.

Carbon Sequestration in Sugarcane Plant-soil System as Influenced by Nutrient Integration Practices under Indo-Gangetic Plains of India

Sugarcane is a multi-purpose crop. The capability of sugarcane crop to sequestrate carbon into soil and plant is of great importance. Under this study the carbon sequestration in planted sugarcane and their rhizospheric soil under different nutrient management practices was assessed. As IPCC reported, that the rising temperature of earth surface resulted of GHGs emission which causes global warming. In order to stabilize the global temperature, the anthropogenic CO2 has to be mitigated to a significant level and the surplus atmospheric CO2 in plants and soil has to be sunk, under this circumstance, sugarcane cultivation plays pivotal role in utilising CO2 since it is a C4 plant having high efficiency of utilising CO2 during photosynthesis. There is another intervention might be enhancing the CO2 capture by changing the nutrient management practices which enhances chlorophyll synthesis by the way of increasing nitrogen efficiency in sugarcane. The different treatment composition enhances photosynthesis where more CO2 has been captured. Thus the sugarcane crop and rhizospheric soils act as important carbon sinks in decarbonisation of atmosphere that ultimately reduces carbon level and causes the global cooling. Soil Properties and Carbon Storage: The results showed that soil physical properties and chemical properties were significantly differed among treatments due to application of different organic amendments over control. Soil organic carbon (SOC) was analysed which ranges from 0.47 to 0.67%. The different organic amendments treatments had a considerable effect on soil bulk density and porosity with significant improvement in soil carbon storage. Plant Carbon Storage: The carbon stocks in different sugarcane plant parts, including roots, shoots and leaves were significantly different. The highest amount of carbon stock was found in leaves (877.08 kg ha-1) under T6 followed by roots (668.74 kg ha-1) in T2 and carbon stock in shoots (422.77 kg ha-1) in T5 showing that 30.41% and 107.58% more carbons were stored in the leaves as compared to the roots and shoots while in roots 58.18% more carbon stored in comparison to shoots. The total carbon storage in sugarcane biomass including aboveground parts and belowground part i.e. roots, in different treatment was significantly different. The mean value of carbon stored in the aboveground parts (leaves and stalks) was significantly higher (1239.65 kg ha-1) than that of underground plant part (621.73 kg ha-1) (roots). The results showed that the sugarcane farming practices have promising effect for carbon sequestration and consequently enhancing the mitigation of climate change impacts.

A statistical model predicts N mineralization of various organic amendments for paddy fields

ABSTRACT To predict the mineralization of nitrogen(N) in organic amendments in paddy fields, we applied data obtained from incubation experiments under waterlogged conditions by a hierarchical Bayesian model using acid-detergent-soluble organic N (ADSON) as a model input. Each of 20 organic amendments (6 cattle manure composts, 3 swine manure composts, 3 poultry manure composts, 2 oil cakes, 2 rice brans, 1 fish meal, 1 sludge fertilizer, and 2 mixed commercial organic fertilizers) was mixed with paddy soil, and the N mineralization curves obtained after 1, 2, 4, 8, and 12 weeks of waterlogging were incorporated into the model to obtain values of the model parameters k i , α1, and Q 10. All model parameters converged with a mean absolute error (MAE) of 0.044 g N kg−1, a root mean square error (RMSE) of 0.060 g N kg−1, and a model efficiency (EF) of 0.96. These values were comparable to or slightly better than those of a previous model for upland soil conditions. Most of the observed values were within the 95% Bayesian prediction interval, indicating that the model performed well with the observed data. Although it is generally believed that livestock manure composts decompose more slowly than organic fertilizers such as oil cake, the livestock manure composts had a large value of the rate constant k i , presumably because of the initial rapid decomposition of the small amounts of organic N present in them. In paddy fields, the soil conditions are aerobic between the application of organic amendments and water entry. In such a case, we propose the use of the upland field model to predict the mineralization of organic N during the period of aerobic soil conditions and of this study’s model during the period of waterlogging, subtracting the amount of already mineralized N from the parameters N in and ADSON. The model devised here is expected to be useful for fertilization design in organic agriculture and in the reduction of the use of inorganic fertilizer.

Effects of long-term application of inorganic fertilizers and organic amendments on the turnover rates of fractionated soil organic carbon and their determining factors in paddy fields

ABSTRACT To investigate how the long-term application of inorganic fertilizer and organic amendments affects the turnover rates of organic matter in physico-chemically fractionated components in paddy soils and how their rates are related to their amounts, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the ∆14C values of accumulated soil organic carbon (SOC) in fractionated components of 5 soil samples from three paddy fields. SOC was fractionated into four components based on their physico-chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. The ∆14C values were determined by accelerator mass spectrometry using graphitized samples. The ∆14C values of SOC in NOxF (from −305‰ to − 90.5‰) were much lower than those of HF (from −123‰ to − 3.7‰) and OxF (from −215‰ to 21.0‰). Lowest values for NOxF suggested slowest turnover rates as expected, and higher and comparable values for OxF and HF implied much faster turnover rates of SOC in OxF compared with upland soils. This could be one of the characteristics of SOC dynamics in paddy soils, probably reflecting repeated puddling of plow layer soils. ∆14C values in all the fractions increased in response to the application of inorganic fertilizer and organic amendments, suggesting faster turnover rate. Soils with clayey and weathered characteristics had the lowest ∆14C values, or slowest turnover rates among the study fields. The relationship between the ∆14C value and the amount of accumulated C for HF, OxF and NOxF indicated that the more the SOC accumulated, the faster the turnover rate of the SOC was, regardless of the fractions, and the relationship of the HF was considerably different from those of OxF and NOxF. In conclusion, these results can be the basis for understanding the C dynamics and for improving soil fertility status and soil C sequestration in paddy soils.

Effects of long-term application of inorganic fertilizer and organic amendments on the amounts of fractionated soil organic carbon and their determining factors in paddy fields

ABSTRACT To investigate how the long-term application of inorganic fertilizer and organic amendments affects the accumulation of organic matter in physico-chemically fractionated components in paddy soils and how the accumulation is determined by soil properties and anthropogenic carbon input, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the amounts of accumulated soil organic carbon (SOC) in fractionated components in three paddy fields. SOC was fractionated into four components based on their physical and chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. On average, the amount and percentage of accumulated C in the four fractions were as follows: OxF (6.63 gC kg−1 soil, 46%) > NOxF (5.32, 35) > LF (1.68, 12) > HF (1.12, 7.2), suggesting about 80% of SOC was in fine, stable fractions. The amount of accumulated C in all fractions increased slightly with the application of inorganic fertilizer, while it increased considerably with the use of organic amendments. In addition, the application of fertilizers and amendments raised the proportion of C content in LF and HF, which are labile and related to soil fertility. Stepwise multiple regression analysis using two principal component analysis scores of soil properties and anthropogenic C input further revealed that the labile fractions (LF and HF) were more strongly determined by the management of fertilizers and amendments, while the stable fractions (OxF and NOxF) were more strongly determined by soil-specific properties, mainly the amorphous nature of the soil. These results indicate that the use of certain amounts of organic amendments would be recommended to carry out rational management to improve soil fertility and C sequestration in paddy fields, with the application of amorphous minerals as an additional option.

Response of maize yield to changes in soil organic matter in a Swedish long‐term experiment

AbstractAgricultural practices that lead to soil carbon sequestration may be a win–win strategy for mitigating global warming and improving soil fertility and resource use efficiency. The mechanisms through which soil organic carbon (SOC) concentration affects crop yields are numerous but difficult to separate. The objective of this study was to disentangle these processes and estimate to what extent the yield response to SOC is mainly driven by changes in physical or biochemical properties and processes. This was achieved by analysing the response of yields in continuous maize to SOC concentrations during 20 years (2000–2019), which had evolved in 14 experimental treatments in a Swedish long‐term field experiment at Ultuna since 1956, ranging from 0.94% to 3.65% in the topsoil (0–20 cm). Average maize yields during this period varied between 1.9 and 8.4 Mg dry mass per hectare in the different treatments. The treatments comprise applications of different mineral nitrogen (N) fertilizers and organic amendments and combinations thereof. Our analysis showed that maize yield in the treatments that were not severely limited by nitrogen supply or soil acidity increased by 16% for each percentage unit increase in SOC. We applied the widely used concept of critical N concentration in plant biomass to diagnose the N status in maize in the different treatments (N nutrition index [NNI]) and parameterized a response function between yield and pH (RpH). Dry soil bulk density (BD) was used as a proxy for soil physical properties. These three variables NNI, RpH and BD explained 95% of the variation in maize yields among treatments. Further analysis of the relationship between BD, SOC and plant available water capacity revealed that about two thirds of the yield increases in response to SOC change could be ascribed to associated changes in soil physical properties. Our analysis suggests that the extra storage capacity of water, which increased by up to 15 mm in the topsoil for each unit percentage increase in SOC, was the main driver for the observed yield responses. We conclude that measures for increasing SOC in soils most likely are an effective adaptation strategy for reducing the risk of crop damage during dry spells, which probably are becoming more frequent in the future due to climate change, even in relatively humid climates as in Sweden.

Organic Amendments: Enhancing Plant Tolerance to Salinity and Metal Stress for Improved Agricultural Productivity

Salinity and metal stress are significant abiotic factors that negatively influence plant growth and development. These factors lead to diminished agricultural yields on a global scale. Organic amendments have emerged as a potential solution for mitigating the adverse effects of salinity and metal stress on plants. When plants experience these stresses, they produce reactive oxygen species, which can impair protein synthesis and damage cellular membranes. Organic amendments, including biochar, vermicompost, green manure, and farmyard manure, have been shown to facilitate soil nitrogen uptake, an essential component for protein synthesis, and enhance various plant processes such as metabolism, protein accumulation, and antioxidant activities. Researchers have observed that the application of organic amendments improves plant stress tolerance, plant growth, and yield. They achieve this by altering the plant’s ionic balance, enhancing the photosynthetic machinery, boosting antioxidant systems, and reducing oxidative damage. The potential of organic amendments to deal effectively with high salinity and metal concentrations in the soil is gaining increased attention and is becoming an increasingly popular practice in the field of agriculture. This review aims to provide insights into methods for treating soils contaminated with salinity and heavy metals by manipulating their bioavailability through the use of various soil amendments.

Ethnobotanical, ecological and health risk assessment of some selected wild medicinal plants collected along mafic and Ultra Mafic rocks of Northwest Pakistan.

The current study investigated wild plant resources and health risk assessment along with northern Pakistan's mafic and ultramafic regions. Ethnobotanical data was collected through field visits and semi-structured questionnaire surveys conducted from local inhabitants and healers. Six potentially toxic elements (PTEs) such as lead (Pb), cadmium (Cd), nickel (Ni), chromium (Cr), manganese (Mn), and zinc (Zn) were extracted with acids and analyzed using atomic absorption spectrophotometer (AAS, Perkin Elmer-7000) in nine selected wild medicinal plants. Contamination factor (CF), pollution load index (PLI), estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) were used to determine the health risk assessment of the studied medicinal plants. The results showed that the selected medicinal plants were used for the treatments of cough, joint swelling, cardiovascular disorders, toothaches, diabetes, and skin pimples by the local inhabitants due to their low-cost and easy accessibility. The concentrations of Pb (3.4-53mgkg-1), Cd (0.03-0.39mgkg-1), Ni (17.5-82mgkg-1), Cr (29-315mgkg-1), Mn (20-142mgkg-1), and Zn (7.4-64mgkg-1) in the studied medicinal plants were found above the safe limits (except Zn) set by WHO/FAO/USEPA (1984/2010). The Pb contamination factor was significantly (p < 0.05) higher in A. modesta (7.84) and D. viscosa (6.81), and Cd contamination factor was significantly higher in C. officinalis (26.67),followed by A. modesta (8.0) mg kg-1. Based on PTE concentrations, the studied plants are considered not suitable for human consumption purposes. Pollution load index values for A. modesta, A. barbadensis, A. caudatus, A. indica, C. procera (2.93), D. viscosa (2.79), and C. officinalis (2.83), R. hastatus (3.12), and Z. armatum were observed as 1.00, 2.80, 2.29, 2.29, 2.93, 2.79, 2.83, 3.12 and 2.19, respectively. Hazard index values were in order of R. hastatus (1.32 × 10-1) ˃ C. procera (1.21 × 10-1) ˃ D. viscosa (1.10 × 10-1) ˃ A. caudatus (9.11 × 10-2) ˃ A. barbadensis (8.66 × 10-2) ˃ Z. armatum (7.99 × 10-2) ˃ A. indica (6.87 × 10-2) ˃ A. modesta (5.6 × 10-2) ˃ C. officinalis (5.42 × 10-2). The health risk index values suggested that consumption of these plants individually or in combination would cause severe health problems in the consumers. Pearson's correlation results showed a significant correlation (p ≤ 0.001) between Zn and Mn in the studied medicinal plants. The current study suggests that wild medicinal plants should be adequately addressed for PTEs and other carcinogenic pollutants before their uses in the study area. Open dumping of mining waste should be banned and eco-friendly technology like organic amendments application should be used to mitigate PTEs in the study area.

Soil aggregate stability governs field greenhouse gas fluxes in agricultural soils

Agriculture is responsible for 30–50% of the yearly CO2, CH4, and N2O emissions. Soils have an important role in the production and consumption of these greenhouse gases (GHGs), with soil aggregates and the inhabiting microbes proposed to function as biogeochemical reactors, processing these gases. Here we studied, for the first time, the relationship between GHG fluxes and aggregate stability as determined via laser diffraction analysis (LDA) of agricultural soils, as well as the effect of sustainable agricultural management strategies thereon. Using the static chamber method, all soils were found to be sinks for CH4 and sources for CO2 and N2O. The application of organic amendments did not have a conclusive effect on soil GHG fluxes, but tilled soils emitted more CO2. LDA was a useful and improved method for assessing soil aggregate stability, as it allows for the determination of multiple classes of aggregates and their structural composition, thereby overcoming limitations of traditional wet sieving. Organic matter content was the main steering factor of aggregate stability. The presence of persistent stable aggregates and the disintegration coefficient of stable aggregates were improved in organic-amended and no-tilled soils. Predictive modelling showed that, especially in these soils, aggregate stability was a governing factor of GHG fluxes. Higher soil CH4 uptake rates were associated with higher aggregate stability, while CO2 and N2O emissions increased with higher aggregate stability. Altogether, it was shown that sustainable agricultural management strategies can be used to steer the soil's aggregate stability and, both consequently and outright, the soil GHG fluxes, thereby creating a potential to contribute to the mitigation of agricultural GHG emissions.

INTEGRATED USE OF PSB AND ORGANIC FERTILIZERS TO IMPROVE YIELD AND QUALITY OF BELL PEPPER (Capsicum Annum L.) CV. GREEN WONDER

Bell pepper is an important Solanaceous crop that is cultivated all around the globe for its economical and nutritional value. In Pakistan, it is cultivated mainly in Sindh and Punjab province of Pakistan. However, average yield ha-1 is quite low as compared to the rest of the world. One of the main reasons for this low yield is poor phosphorous status. The current study was conducted to estimate the effects of organic application combined with PSB biofertilizers (Phosphorus Solubilizing Bacteria) on growth and yield of bell pepper. Organic amendments included leaf compost (LC), farmyard manure (FYM) and poultry manure (PM). Bell pepper cultivar “Green Wonder” was used as test crop. FYM and PM showed better results as compared to LC in most of the measured parameters. Plant height in FYM and PM was 59.79 and 59.07 cm while PSB application produced 67.84 cm high plants. Maximum leaf area was 176.98 cm2 that for FYM and was further increased up to 204.43 cm2 when supplemented with PSB. Bell pepper yield was also maximum in FYM i.e. 1211.7 g while PM showed a value of 1077.6. g. However, when PSB was applied in combination with these treatments, yield plant-1 was further increased up to 1393.4 and 1227.6 g, respectively. Total soluble solids were statistically at par among all the organic amendments but higher than control. Ascorbic acid was maximum in PM (58 mg 100 g-1) and followed by FYM (55.53 mg 100 g-1). PSB application showed a value of 72.46 mg 100 g-1. It is recommended from these results that application of organic amendments and PSB should be practiced enhancing that yield and quality of bell pepper.

Sodium accumulation vs. nitrate leaching under different fertigation regimes in greenhouse soils in South Uruguay

In greenhouse conditions, soil salinity and N leaching depend on the provision of irrigation, the irrigation water quality and the application of fertilizers and organic amendments. The objective of this study was to quantify and analyze the accumulation and/or leaching process of NO3- and Na+ in greenhouse tomato production in the south region of Uruguay in fine-textured soil under different fertigation regimes. The study was conducted in four tomato crops during 2019/20/21 seasons. Three fertigation regimes were applied. Irrigation volume was the same for all treatments. Drainage was determined by using free drainage lysimeters. Concentration in soil solution and leaching of NO3- and Na+ was measured by monitoring soil solution and drainage solution. Yield, N uptake and N utilization efficiency were determined for each treatment. Soil total drainage was the main factor explaining N and Na+ leaching. The leaching of N ranges from 0 to 23.4 kg N ha-1 per tomato crop with total drainage between 0 and 46.2 % of total irrigation. Drainage necessary to avoid Na+ accumulation was 13 % of total irrigation. This drainage produced 8.4 kg of N leaching per ha-1 during tomato cropping period. Optimizing irrigation is the key factor to the salinity-nitrogen leaching paradox. Irrigation amount and timing should attempt: (1) to avoid excessive irrigation when NO3- concentration in soil solution is high, and (2) to apply leaching irrigation when Na+ concentration in soil solution is high. Soil solution monitoring with suction probes and rapid chemical analysis systems could be a useful tool to identify periods of high risk of N leaching and the right time for leaching irrigation.