Soil Nutrient Bioavailability Research Articles

Sustainable strategy for rehabilitating phosphate mining sites and valorisation of phosphate industry by-products and sludge using pistachio tree (Pistacia atlantica), false pepper (Schinus molle), and eucalyptus (Eucalyptus globulus) trees

The development of anthroposols has been proposed as a new environmentally friendly approach to ensuring the successful revegetation of phosphate mining sites. The phosphate industry's by-products, including phosphogypsum (PG), phosphate sludge (PS), and sewage sludge (SS), can be valuable resources in restoring the ecological balance of mined soil areas. The aim of this study was to safely and sustainably restore the ecological integrity of the phosphate mining site through the evaluation of nutrients and heavy metals dynamics in soil and plant tissues of three tree species and treated by-products containing 65 % PG, 30 % PS, and 5 % SS. The tree species used were Pistacia atlantica, Schinus molle, and Eucalyptus globulus. The experimental layout was a randomised complete block design with six replicates and three treatments. Growth diameter, height, nutrient uptakes and heavy metal dynamic were evaluated from the rhizosphere soils and plant tissues over two years. Hierarchical head maps of correlations between the measured growth parameters, soil and nutrient uptakes of the tree species were analysed using a phylogenetic generalised linear mixed model. S. molle and E. globulus had higher average diameter and height than P. atlantica plants. P. atlantica and S. molle showed greater nitrogen, phosphorus, potassium, calcium, and magnesium concentrations than E. globulus trees. Tree growth parameters were closely linked to soil nutrient bioavailability. The heavy metal accumulation ratio was higher in the E. globulus and S. molle leaves than in stems. Using by-products could be valorised for rehabilitating mine sites together with E. globulus and S. molle species.

Biochar derived from invasive plants improved the pH, macronutrient availability and biological properties better than liming for acid rain-affected soil

Rapid development in industrialization and urbanization causes serious environmental issues, of which acid rain is one of the quintessential hazards, negatively affecting soil ecology. Liming has been investigated for a long time as the most effective amendment to alter the adverse effects of soil acidity resulting from acid rain. Herein, this study tested the biochar produced from invasive plants as an alternative amendment and hypothesized that biochar can maintain better availability of macronutrients under acid rain than liming by improving soil chemical and biological properties. Therefore, a pot experiment was conducted to compare the effects of lime and biochar at two rates (1% and 3%) on soil available nitrogen (N), phosphorous (P) and potassium (K) under simulated acid rain of two pH levels (4.5: pH4.5 and 2.5: pH2.5) as compared with tap water (pH7.1) as a control treatment. Biochar was produced using different invasive plants, including Blackjack (Biden Pilosa), Wedelia (Wedelia trilobata) and Bitter Vine (Mikania micrantha Kunth). Liming decreased the availability of soil N, P, and K by 36.3% as compared with the control due to the great increment in soil pH and exchangeable calcium (Ca2+) by 59% and 16-fold, respectively. Moreover, liming reduced the alpha diversity of soil bacteria and fungi by 27% and 11%, respectively. In contrast, biochar at different types and rates resulted in a fourfold increment in the available N, P, and K as an average under acid rain (pH4.5 and pH2.5) owing to maintaining a neutral pH (6.5–7), which is the most favorable level for soil microbial and enzymatic activites, and the bioavailability of soil nutrients. Furthermore, biochar caused balanced increments in Ca2+ by threefold, cation exchange capacity by 45%, urease activity by 16%, and fungal diversity by 10%, while having a slight reduction in bacterial diversity by 2.5%. Based on the path, correlation, and principal component analyses, the exchangeable aluminum was a moderator for the reductions in macronutrients’ availability under acid rain, which decreased by 40% and 35% under liming and biochar, respectively. This study strongly recommended the use of biochar from invasive plants instead of lime for sustainable improvements in soil properties under acid rain.Graphical

Combined effects of dry-wet irrigation, redox changes and microbial diversity on soil nutrient bioavailability in the rice field

Sustainable development goals (SDGs) by United Nations are some of the high-priority areas of research and this article established the sustainable agronomic practices converging soil chemistry, crop productivity and soil microbial involvement in nutrient modulation. Alternate wetting-drying (AWD) cultivation with implications on soil microbiome, nutritional dynamics and rice yield during pre-monsoon (boro) and monsoon (aman) season are not well studied. In the present 4-year field study, the impact of AWD irrigation in pre-monsoon and flooded irrigation in monsoon on soil microbiota and the nutrient pool has been studied. Nutrient-less pond water has been used to avoid any external nutrient input from irrigation water to ensure the sole elemental flux within the soil itself. The release of soil nutrients into the soil-aqueous system, influencing microbial populations and modulating the redox status was explored. Results indicated an increase in total concentration as well as bioavailability of selected nutritional elements (N, P, K, Fe, Ca, Mg, Cu and Zn) by 16–54% in the pre-monsoon cultivation relative to monsoon cultivation. Three plant growth phases (developing, milking and harvest) were considered to check the nutrient modulations in soil and plant tissues along with the plant growth and elemental uptake continuum. Crop plant measurements were improved and grain yields were found to be 5.2–6.46% increased under AWD and microbial activity. Krona charts, relative abundance, rarefaction curve and multivariate analysis of metagenomics data showed that the pre-monsoon soil was more enriched and maintained a balance between soil pH and microbial biomass than the monsoon soil. Microbial community diversity associated with plant growth phases was also found to be different depending on the seasonal alterations. Bacillus sp., Acidothiobacillus sp., Pseudomonas sp., Rhizobium sp., Burkholderia sp. were predominant in pre-monsoon soil releasing pulses of N, P, K, Ca and Mg whereas Verrucomicrobia was found to be dominant in monsoon soil where Fe was released. This study is a first of its kind that showed the combined effect of season and some specific groups of soil microbes on macro-micro nutritional availability in soil and enhanced plant quality.

Encephalartos natalensis, Their Nutrient-Cycling Microbes and Enzymes: A Story of Successful Trade-Offs.

Encephalartos spp. establish symbioses with nitrogen (N)-fixing bacteria that contribute to soil nutrition and improve plant growth. Despite the Encephalartos mutualistic symbioses with N-fixing bacteria, the identity of other bacteria and their contribution to soil fertility and ecosystem functioning is not well understood. Due to Encephalartos spp. being threatened in the wild, this limited information presents a challenge in developing comprehensive conservation and management strategies for these cycad species. Therefore, this study identified the nutrient-cycling bacteria in Encephalartos natalensis coralloid roots, rhizosphere, and non-rhizosphere soils. Additionally, the soil characteristics and soil enzyme activities of the rhizosphere and non-rhizosphere soils were assayed. The coralloid roots, rhizosphere, and non-rhizosphere soils of E. natalensis were collected from a population of >500 E. natalensis in a disturbed savanna woodland at Edendale in KwaZulu-Natal (South Africa) for nutrient analysis, bacterial identification, and enzyme activity assays. Nutrient-cycling bacteria such as Lysinibacillus xylanilyticus; Paraburkholderia sabiae, and Novosphingobium barchaimii were identified in the coralloid roots, rhizosphere, and non-rhizosphere soils of E. natalensis. Phosphorus (P) cycling (alkaline and acid phosphatase) and N cycling (β-(D)-Glucosaminidase and nitrate reductase) enzyme activities showed a positive correlation with soil extractable P and total N concentrations in the rhizosphere and non-rhizosphere soils of E. natalensis. The positive correlation between soil enzymes and soil nutrients demonstrates that the identified nutrient-cycling bacteria in E. natalensis coralloid roots, rhizosphere, and non-rhizosphere soils and associated enzymes assayed may contribute to soil nutrient bioavailability of E. natalensis plants growing in acidic and nutrient-poor savanna woodland ecosystems.

Modified Ion Exchange Resin Method for Extraction of Micronutrient Cations from Soils

ABSTRACT Different chemical extractants and ion exchange resins are used to assess the bioavailability of soil nutrients for crop plants. The major problems associated with the use of IER in soil testing are their reusability and the difficulties encountered in their separation from the soil being extracted. We addressed these difficulties by encapsulating a weakly acidic cation exchange resin and weakly basic anion exchange resin in separate dialysis membrane pouches and suspending them together in a cellulose extraction thimble during extraction. The suitability of this method has been evaluated for diverse types of soils widely varying in physicochemical properties. The standardization of protocol revealed that the ideal conditions for extraction of micronutrients were: 20:40 soil water ratio and 4 h extraction at 25°C in a shaker incubator at 120 rpm. This simple modified ion exchange resin method can be used multiple times for routine soil tests in laboratories for extraction of cationic micronutrients. The soil extracts can be analyzed for cationic micronutrients. The coefficients of determination (R2) between resin extractable- and diethylene triamine pentaacetic acid extractable- nutrients were 0.31, 0.59, 0.67, and 0.88 for Zn, Cu, Fe, and Mn, respectively.

A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress.

Root exudates are thought to play an important role in plant-microbial interactions. In return for nutrition, soil bacteria can increase the bioavailability of soil nutrients. However, root exudates typically decrease in situations such as drought, calling into question the efficacy of solvation and bacteria-dependent mineral uptake in such stress. Here, we tested the hypothesis of exudate-driven microbial priming on Cupressus saplings grown in forest soil in custom-made rhizotron boxes. A 1-month imposed drought and concomitant inoculations with a mix of Bacillus subtilis and Pseudomonas stutzeri, bacteria species isolated from the forest soil, were applied using factorial design. Direct bacteria counts and visualization by confocal microscopy showed that both bacteria associated with Cupressus roots. Interestingly, root exudation rates increased 2.3-fold with bacteria under drought, as well as irrigation. Forty-four metabolites in exudates were significantly different in concentration between irrigated and drought trees, including phenolic acid compounds and quinate. When adding these metabolites as carbon and nitrogen sources to bacterial cultures of both bacterial species, eight of nine metabolites stimulated bacterial growth. Importantly, soil phosphorous bioavailability was maintained only in inoculated trees, mitigating drought-induced decrease in leaf phosphorus and iron. Our observations of increased root exudation rate when drought and inoculation regimes were combined support the idea of root recruitment of beneficial bacteria, especially under water stress.

Green Synthesis of Nanoparticles by Mushrooms: A Crucial Dimension for Sustainable Soil Management

Soil is the main component in the agroecosystem besides water, microbial communities, and cultivated plants. Several problems face soil, including soil pollution, erosion, salinization, and degradation on a global level. Many approaches have been applied to overcome these issues, such as phyto-, bio-, and nanoremediation through different soil management tools. Mushrooms can play a vital role in the soil through bio-nanoremediation, especially under the biological synthesis of nanoparticles, which could be used in the bioremediation process. This review focuses on the green synthesis of nanoparticles using mushrooms and the potential of bio-nanoremediation for polluted soils. The distinguished roles of mushrooms of soil improvement are considered a crucial dimension for sustainable soil management, which may include controlling soil erosion, improving soil aggregates, increasing soil organic matter content, enhancing the bioavailability of soil nutrients, and resorting to damaged and/or polluted soils. The field of bio-nanoremediation using mushrooms still requires further investigation, particularly regarding the sustainable management of soils.

Bioorganic and silicon amendments alleviate early defoliation of pear trees by improving the soil nutrient bioavailability, microbial activity, and reshaping the soil microbiome network

Pear trees with severe early defoliation usually suffer from weakened aboveground growth and a serious decrease of fruit quality and yield. Soil fertility and its microbial community and functional activity are significant factors impacting plant growth and yield, which also might be the very factors that influence the early defoliation of pear trees. To address the problems caused by chemical fertilizers, bioorganic fertilizer (BIO) and silicon amendment (SOA) are increasingly used as amendments to improve soil microbial activity and increase soil nutrient availability. However, how effective BIO and SOA are at improving the health of soils and reducing early defoliation remains unclear. Here, we conducted a 4-year field experiment (2016–2019) in a 25-year-old ‘Cuiguan’ pear orchard in Jianning county, Fujian province, comparing local custom fertilization (CK), local custom fertilization supplemented with SOA (CK-SOA), BIO, and BIO supplemented with SOA (BIO-SOA). At the end of the 4-year study we found that BIO and BIO-SOA treatments resulted in reduced leaf nitrogen content and increased leaf potassium (K), calcium (Ca), silicon (Si), and manganese (Mn) content. BIO and BIO-SOA treatments also resulted in a 50% reduction of the early deciduous rate and a 47% increase in pear yield. Compared with CK treated soil, BIO and BIO-SOA treated soils had higher nitrate nitrogen content (NO3−-N), available Si, Fe, Mn, and Zn content, and significantly improved microbial biomass nitrogen content (MBN), geometric mean enzyme activity (GMEA) and ecosystem multifunctionality (EMF). Network analysis revealed that BIO and BIO-SOA treatments had significantly altered the bacterial and fungal community composition in the orchard soil. Redundancy analysis (RDA) and the Mantel test indicated that soil available K, exchangeable Ca and Mg, and available Si, Fe, Mn and Zn content were the main factors influencing bacterial and fungal communities. The increased nutrient availability (e.g., NO3−-N and microelement contents), MBN, GMEA and EMF had negative effects on the early defoliation rate. Random Forest model identified soil available Si content, microbial biomass nitrogen content, EMF, and GMEA as the main predictors of early defoliation rate. Overall, this study demonstrates that application of BIO or BIO mixed with SOA can alleviate the early defoliation rate of pear trees by increasing the availability of microelements, microbial functional activity, and changing the soil microbial community composition.

Veterinary antibiotics can reduce crop yields by modifying soil bacterial community and earthworm population in agro-ecosystems

Veterinary antibiotics are intensively and widely used in animal farming to treat or prevent diseases, as well as improve growth rate and feed efficiency. Animal manure is an important reservoir of veterinary antibiotics due to their high excretion rates, and thus manure application has been a critical source of veterinary antibiotics in agro-ecosystems. However, how veterinary antibiotics affect agroecosystem functions is still unclearly understood. In this study, we evaluated the effects of veterinary antibiotics on soil bacteria and earthworms in agricultural land with long-term manure application. The potential mechanisms of antibiotic-induced changes in crop yields were also revealed. The results showed that the increasing prevalence of veterinary antibiotics in agro-ecosystems inhibited earthworm abundance and bacterial diversity, and then decreased the bioavailability of soil nutrients. Furthermore, high-dose exposure to veterinary antibiotics improved the abundance of plant pathogenic bacteria. Analysis indicated that veterinary antibiotics played an important underlying role in driving the negative effects on peanut grain yields via disturbing microbe- and earthworm-mediated soil available nutrient contents. The direct toxicity effects of antibiotics on peanut relative yields were stronger than their indirect mediating effects. Additionally, the tradeoffs between antibiotics and agroecosystem functions increased at low exposure levels and then decreased at high exposure levels, which indicated the effects of antibiotics on agroecosystem functions were dose-dependent, except for earthworm biomass. Antibiotic contamination which will impose threats to agricultural sustainability was highlighted and should be paid more attention.

Can precrops uplift subsoil nutrients to topsoil?

Precrops exhibit vigorous deep root growth, especially when grown perennially. However, their contribution to accumulate essential nutrients derived from deeper soil layers in the topsoil has not been quantified. We determined the vertical distribution of phosphorous (P) and potassium (K) affected by contrasting root systems of 3 precrops and their effects on subsequently grown spring wheat. Three precrops (lucerne, chicory and tall fescue) were grown for 1, 2 and 3 years prior to spring wheat cultivation. We measured plant available soil P and K from 0 to 30 cm to 75–105 cm of soil depth after precropping. Root growth and crop performance of spring wheat as affected by precropping were measured in two repeated trials. We observed maximum 22-fold higher root-length density (RLD; cm cm− 3) of taprooted chicory compared with fibrous-rooted tall fescue in the subsoil. There were significant increases in plant available K in the topsoil by 27 mg kg− 1 over the precrop duration between 1 and 3 years. Grain yield of subsequently grown spring wheat was significantly increased by 10 % and 14 % from 1 year to 3 year-treatments of lucerne and chicory, respectively. Similarly, significant increases in P uptake (7 % and 19 %) and K uptake (21 and 14 %) of spring wheat was noted for the same treatments. Our data suggest that there is potential for the yield of short-season cereals to be improved by increased soil nutrient bioavailability in the topsoil derived from deeper soil layers by the deep roots of perennial precrops.

Long-term phytoremediation using the symbiotic Pongamia pinnata reshaped soil micro-ecological environment

Understanding the effects of phytoremediation on ecological environments is a core issue in soil bioremediation. However, the response of soil micro-ecological environment to long-term phytoremediation of symbiotic legume is still unknown. To address this issue, we focused on the changes of soil physicochemical properties, microbial communities, ecological functions, and correlation relationships of microbial populations in the VTi magnetite mine tailings subsoil and the natural topsoil after three years' in-situ phytoremediation using the symbiotic Pongamia pinnata. The results showed that the bioavailability of soil nutrients and metals had undergone different degrees of significant changes in the two different metallic soil types after phytoremediation. It was revealed by changes in alpha-diversity indices, relative microbial abundance, LEfSe scores, and the number of significant OTUs that long-term phytoremediation using P. pinnata significantly altered soil microbial communities. This shift further caused a significant change in soil ecological functions and microbial community correlations. All changes in ecological functions caused by P. pinnata were in different degrees in the two different soil types. The Bray-Curtis based redundancy analysis (bcRDA) indicated that the shift of microbial communities was driven by several bioavailable nutrients and metals. Therefore, this study proved that long-term phytoremediation of symbiotic legumes could reshape soil microbial communities, and implied that a dramatic change in soil micro-ecological environment and an improvement of soil quality were the results of following long-term phytoremediation using the symbiotic legume.

Humic acids derived from Leonardite to improve enzymatic activities and bioavailability of nutrients in a calcareous soil

Understanding the role of humic substances in soils is important for developing and utilizing organic fertilizers or soil amendments for sustainable agriculture. The objective of this study was to determine the effects of different fractions of humic acids derived from Leonardite on enzymatic activities and bioavailability of nutrients in a soil. The experiment was carried out by mixing different factions of humic acids with a soil and incubated for 70 d. The treatments included five factions of humic acids (HS1 (low molecular weight), HS2 (medium molecular weight), HS3 (large molecular weight, SED (sediment of fractions), HS (mixture of HS1, HS2, and HS3)), raw Leonardite (IM) and a control (no addition of humic acid). Experimental results showed that application of humic acids significantly improved acid and alkaline phosphatase activities, especially with HS1. Humic substances with high molecular weights significantly inhibit urease activity, and the optimal application rate was 600 kg/hm2 of humic substances with the high molecular weights. Concentrations of NH4+-N were decreased with increasing humus applications. All treatments (HSmix, HS1, HS2, HS3, IM, SED) did not affect the soil contents of Ca, although soil concentrations of K, P, Cu, Zn were increase significantly when small molecular weight humus (HS1) was applied. Keywords: humic acid, molecular weight, Leonardite, enzyme, nutrient content DOI: 10.25165/j.ijabe.20201303. Citation: Sun Q, Liu J L, Huo L F, Li Y C, Li X, Xia L R, et al. Humic acids derived from Leonardite to improve enzymatic activities and bioavailability of nutrients in a calcareous soil. Int J Agric & Biol Eng, 2020; 13(3): 200–205.

Humic acids derived from Leonardite to improve enzymatic activities and bioavailability of nutrients in a calcareous soil

Understanding the role of humic substances in soils is important for developing and utilizing organic fertilizers or soil amendments for sustainable agriculture. The objective of this study was to determine the effects of different fractions of humic acids derived from Leonardite on enzymatic activities and bioavailability of nutrients in a soil. The experiment was carried out by mixing different factions of humic acids with a soil and incubated for 70 d. The treatments included five factions of humic acids (HS1 (low molecular weight), HS2 (medium molecular weight), HS3 (large molecular weight, SED (sediment of fractions), HS (mixture of HS1, HS2, and HS3)), raw Leonardite (IM) and a control (no addition of humic acid). Experimental results showed that application of humic acids significantly improved acid and alkaline phosphatase activities, especially with HS1. Humic substances with high molecular weights significantly inhibit urease activity, and the optimal application rate was 600 kg/hm2 of humic substances with the high molecular weights. Concentrations of NH4+-N were decreased with increasing humus applications. All treatments (HSmix, HS1, HS2, HS3, IM, SED) did not affect the soil contents of Ca, although soil concentrations of K, P, Cu, Zn were increase significantly when small molecular weight humus (HS1) was applied. Keywords: humic acid, molecular weight, Leonardite, enzyme, nutrient content DOI: 10.25165/j.ijabe.20201303. Citation: Sun Q, Liu J L, Huo L F, Li Y C, Li X, Xia L R, et al. Humic acids derived from Leonardite to improve enzymatic activities and bioavailability of nutrients in a calcareous soil. Int J Agric & Biol Eng, 2020; 13(3): 200–205.

Changes in nutrient contents in peel, pulp, and seed of cherimoya (Annona cherimola Mill.) in relation to organic mulching on the Andalusian tropical coast (Spain)

Cherimoya, a tropical fruit from South America whose commercial demand is increasing for both its exceptional flavor and high nutritional content, is expanding in cultivation to subtropical areas such as the Mediterranean coast of Andalusia (Spain). In this paper, we analyze cherimoyas (peel, pulp, and seed) grown in Almuñécar (Granada, Spain) during the years 2013, 2015, and 2016 from trees applied with different pruning wastes (avocado, cherimoya, mango, and garden). The cherimoya fruits had high contents in most of the macronutrients, especially K, Ca, and micronutrients such as Fe and Zn. The Na, P, K and Ca concentrations were related to the plant mulch that released nutrients to the soil and led to a variation in soil-nutrient bioavailability by decreasing the soil pH. The seed was the part of the cherimoya that registered the least nutritional change due to annual weather differences and the highest positive effects of mulching in terms of increased nutrient availability after mulching.

Effects of repeated applications of sewage sludge and municipal compost on bio availability of soil nutrients in onion (Allium cepa L) cultivation

سابقه و هدف: روند رو به افزایش تخریب منابع آب، خاک و محیط‌زیست در اثر کاربرد بی‌رویه مواد شیمیایی موجب ترغیب پژوهشگران به کشاورزی ارگانیک در سال­های اخیر شده است. باوجود همه اثرات مثبتی که در ارتباط با مصرف کمپوست زباله شهری و لجن فاضلاب بر روی ویژگی­های فیزیکی و شیمیایی خاک مطرح است، هنوز در این رابطه نگرانی­های زیادی ازنظر مسائل زیست­محیطی و سلامت وجود دارد. لذا هدف از این پژوهش بررسی تأثیر مقادیر مختلف کودهای آلی کمپوست زباله شهری و لجن فاضلاب در خاک و گیاه درکشت پیاز پس از 5 سال در کرت‌های ثابت به لحاظ تجمع عناصر سنگین در خاک و گیاه می‌باشد. مواد و روش‌ها: این تحقیق در کرت­های ثابت (ابعاد هر کرت 40 مترمربع)، در ایستگاه تحقیقاتی آبیاری و زهکشی رودشت اصفهان با چهار تیمار کود آلی کمپوست زباله‌ شهری و کود لجن فاضلاب به همراه تیمار شاهد در قالب یک طرح بلوک‌های کامل تصادفی در سه تکرار و پنج سال متوالی انجام شد. تیمارها عبارت بودند از: الف- بدون کاربرد هیچ‌گونه کود آلی در طول دوره‌های آزمایش (شاهد). ب- تیمار 25 تن در هر هکتار کود کمپوست زباله شهری. ج- تیمار 50 تن در هکتار کود کمپوست زباله شهری. د- تیمار 15 تن در هکتار لجن فاضلاب. ه- تیمار 30 تن در هکتار لجن فاضلاب. نتایج و بحث: کاربرد کمپوست زباله شهری و لجن فاضلاب در خاک سبب افزایش ماده آلی خاک شد. از سوی دیگر مصرف این تیمارهای کودی به­ویژه در سطوح بالاتر، غلظت عناصر غذایی موردنیاز گیاه در خاک ازجمله فسفر، پتاسیم، روی، مس، منگنز و آهن قابل‌استفاده، را افزایش داد. مصرف این مواد آلی در مرحله اول تأثیری برافزایش میزان عناصر سنگین سرب و کادمیوم در خاک نداشت؛ اما مصرف چندین سال متوالی کمپوست زباله (تیمار50 تن در هکتار) در مرحله دوم، باعث افزایش سرب قابل‌جذب در خاک شد. هم‌چنین مصرف سطوح مختلف کودهای آلی باعث افزایش معنی‌دار در عناصر غذایی موجود در اندام هوایی گیاه پیاز شامل نیتروژن، فسفر و پتاسیم و همچنین عناصر ریزمغذی آهن، روی، مس و منگنز شد. بیشترین میزان عناصر غذایی اندازه‌گیری‌شده در اندام هوایی گیاه ذرت در تیمار 50 تن در هکتار کمپوست زباله شهری مشاهده شد که در اغلب موارد تفاوت معنی‌داری با تیمار 30 تن در هکتار لجن فاضلاب نداشت. غلظت اغلب عناصر غذایی اندازه‌گیری‌شده در اندام هوایی گیاه پیاز پس از پنج سال مصرف متوالی کودهای آلی به‌صورت معنی‌داری نسبت به مرحله اول پژوهش (پس از یک سال مصرف کودهای آلی) افزایش پیدا کرد. در مورد عنصر مس این روند معکوس بود و میزان جذب این عنصر در مرحله دوم نسبت به مرحله اول، به دلیل افزایش غلظت عناصر دیگر مانند فسفر و وجود رقابت بین عناصر مختلف در جذب به‌وسیله گیاه، کاهش یافت. مصرف تیمارهای مختلف کود آلی در مرحله اول تنها میزان عنصر روی را در غده پیاز افزایش داد اما در مرحله دوم و درنتیجه مصرف چندین ساله کمپوست زباله و لجن فاضلاب، غلظت عناصر غذایی نیتروژن، پتاسیم، مس، آهن و روی در غده پیاز افزایش یافت. غلظت سرب و کادمیم در گیاه، در تیمارهای مختلف به حدی کم بود که با دستگاه جذب اتمی قابل‌اندازه‌گیری نبود. نتیجه‌گیری: در کل کمپوست زباله شهری و لجن فاضلاب در سطوح مذکور ضمن افزایش ماده آلی در خاک ، باعث افزایش غلظت عناصر غذایی در گیاه به‌ویژه ازلحاظ عناصر ریزمغذی ازجمله روی و آهن شد.

Biochar properties and soil type drive the uptake of macro‐ and micronutrients in maize (Zea mays L.)

AbstractThe use of biochar in agriculture is a promising management tool to mitigate soil degradation and anthropogenic climate change. However, biochar effects on soil nutrient bioavailability are complex and several concurrent processes affecting nutrient bioavailability can occur in biochar‐amended soils. In a short‐term pot experiment, the concentration of N, P, K, S, Ca, Mg, Cu, Zn, Mn, B, Fe, and Na in the shoots of maize grown in three different soil types [sandy soil (S1), sandy loam (S2), and sandy clay loam (S3)] was investigated. The soils were either unamended or amended with two different biochars [wheat straw biochar (SBC) or pine wood biochar (WBC)] at two P fertilizer regimes (–/+ P). We used three‐way ANOVA and Principal Component Analyses (PCA) of transformed ionomic data to identify the effects of biochar, soil, and P fertilizer on the shoot nutrient concentrations. Three distinct effects of biochar on the shoot ionome were detected: (1) both biochars added excess K to all three soils causing an antagonistic effect on the uptake of Ca and Mg in maize shoots. (2) Mn uptake was affected by biochar with varying effects depending on the combined effect of biochar and soil properties. (3) WBC increased maize uptake of B, despite the fact that WBC increased soil pH and added additional calcite to the soil, which would be expected to reduce B bioavailability. The results of this study highlight the fact that the bioavailability of several macro and micronutrients is affected by biochar application to soil and that these effects depend on the combined effect of biochar and soils with different properties.

Novel value-added phosphorus-potassium-activator fertilizers improve phosphorus use efficiency and crop yields

ABSTRACTIt is thus essential and critical to enhance phosphorus (P) fertilizer use efficiency of crops to improve agricultural and environmental sustainability. A pot experiment was conducted to examine the impact of different kinds of value-added P-potassium (K)-activator fertilizers (VPAFs) on soil nutrient bioavailability, growth and yield of wheat-maize crops. Compared with that of the control (NPK) treatment, the wheat yields of VPAF treatments increased from 6.59% to 18.61%, and the maize yields increased from −0.22% to 15.58%. In addition, the P fertilizer utilization rate of VPAF treatments increased by an average of 10.87% and 5.75% for wheat and maize, respectively. Therefore, VPAF application in agriculture can introduce multiple benefits including increasing crop yield, improving fertilizer utilization efficiency, enhancing nutrient bioavailability, and reducing pollution.

Soil microalgae modulate grain arsenic accumulation by reducing dimethylarsinic acid and enhancing nutrient uptake in rice (Oryza sativa L.)

Microalgae are ubiquitous in paddy soils. However, their roles in arsenic (As) accumulation and transport in rice plants remains unknown. Two green algae and five cyanobacteria were used in pot experiments under continuously flooded conditions to ascertain whether a microalgal inoculation could influence rice growth and rice grain As accumulation in plants grown in As-contaminated soils. The microalgal inoculation greatly enhanced nutrient uptake and rice growth. The presence of representative microalga Anabaena azotica did not significantly differ the grain inorganic As concentrations but remarkably decreased the rice root and grain DMA concentrations. The translocation of As from roots to grains was also markedly decreased by rice inoculated with A. azotica. This subsequently led to a decrease in the total As concentration in rice grains. The results of the study indicate that the microalgal inoculation had a strong influence on soil pH, soil As speciation, and soil nutrient bioavailability, which significantly affected the rice growth, nutrient uptake, and As accumulation and translocation in rice plants. The results suggest that algae inoculation can be an effective strategy for improving nutrient uptake and reducing As translocation from roots to grains by rice grown in As-contaminated paddy soils.

Machine learning for the prediction of L. chinensis carbon, nitrogen and phosphorus contents and understanding of mechanisms underlying grassland degradation

The grasslands of Western Jilin Province in China have experienced severe degradation during the last 50 years. Radial basis function neural networks (RBFNN) and support vector machines (SVM) were used to predict the carbon, nitrogen, and phosphorus contents of Leymus chinensis (L. chinensis) and explore the degree of grassland degradation using the matter-element extension model. Both RBFNN and SVM demonstrated good prediction accuracy. The results indicated that there was severe degradation, as samples were mainly concentrated in the 3rd and 4th levels. The growth of L. chinensis was shown to be limited by either nitrogen, phosphorus, or both during different stages of degradation. The soil chemistry changed noticeably as degradation aggravated, which represents a destabilization of L. chinensis community homeostasis. Soil salinization aggravates soil nutrient loss and decreases the bioavailability of soil nutrients. This, along with the destabilization of C/N, C/P and N/P ratios, weakens the photosynthetic ability and productivity of L. chinensis. This conclusion was supported by observations that L. chinensis is gradually being replaced by a Chloris virgata, Puccinellia tenuiflora and Suaeda acuminate mixed community.

Accumulated Impacts of Sulfur Spraying on Soil Nutrient Availability and Microbial Biomass in Rubber Plantations

Sulfur spraying is a conventional prevention and control measure for rubber leaf diseases in the northern margin of tropical Southeast Asia. The aim of this study was to determine the long‐term (48 years) accumulated effects of sulfur spraying on some major soil microbial and nutrient properties in the area of rubber plantation. The results indicate a significant decrease in pH along the rubber chronosequence with yearly sulfur application. A negative effect of sulfur spraying on soil total sulfur content was also observed. Apart from that, soil microbial characteristics increased significantly, except for microbial biomass carbon. Soil nutrient bioavailability‐related characteristics showed a complex pattern of response to sulfur spraying, among which bio‐available ammonium nitrogen increased linearly, bio‐available nitrate nitrogen showed a trend resembling a large resting capital letter “S”, bio‐available phosphorus showed a contrary trend to nitrogen, a capital letter “S” resting the other direction, whereas bio‐available potassium had no response to sulfur spraying. Based on the comprehensive response indexes, soil microbial characteristics had a pulsing response to sulfur spraying accumulation and two critical turning points were sometime between the 23rd and 32nd year and between the 40th and 48th year. Soil nutrient bioavailability showed a volatile comprehensive pattern, but there was no significant difference during the chronosequence. There is need for control sulfur deposition frequency and dosage under the soil and environmental safety threshold in the diseases prevention and control in monoculture rubber plantation.