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Sustainable agricultural practices based on the development of native arbuscular mycorrhizal fungi (AMF) can improve crop growth and stress tolerance in acidic soils with manganese toxicity. The beneficial effects are stronger when crops are colonized early in development by an intact extraradical mycelium (ERM), but are dependent on AMF assemblage. In wheat colonized by AMF associated to Lolium rigidum L. (LOL) or Ornithopus compressus (ORN), growth and stress tolerance are differently influenced. In the present study, this functional diversity was studied by evaluating the activity of ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), guaiacol peroxidase (GPX), superoxide dismutase (SOD) and Mn-SOD. ORN treatment promoted higher wheat shoot and root dry weights, a higher root protein content, decreased root APX, GR and SOD activities but a higher proportion of MnSOD activity. ORN associated microbiota differently manage antioxidant enzyme activity of succeeding wheat to improve growth. [ABSTRACT FROM AUTHOR]

High concentration of aluminum (Al) ion solubilized in acid soils restrict plant growth. The mechanisms of plant adaptation to Al stress can be separated into Al exclusion and internal Al inactivation. In general, plant species that have developed mechanisms of the former type are called “Al excluders”, and those that have developed mechanisms of the latter type are called “Al accumulators”. Aluminium accumulators are widely distributed in acid soils, particularly in humid tropics. In addition to their geographical distribution, Al accumulators show a wide phylogenetic distribution in plant. Here I discussed physiological characteristics of Al accumulation among different Al accumulator species within various vascular plant taxa. Results from the literature suggested that variation of the Al detoxification and accumulation mechanisms in the tissue of Al accumulators seemed to be small in vascular plant. [ABSTRACT FROM AUTHOR]

The study evaluated the effects of lime and dolomite application (2 and 4 t ha−1) in combination with NPK fertilizer (1 t ha−1) or borax (50 kg ha−1) on micronutrient concentrations in the raspberry leaves and fruits grown in the soil with a strongly acid reaction. Changes in the content of micronutrients (Fe, Mn, Cu, Zn, and B) and Al in the soil and raspberry leaves and fruits were monitored during a two-year period. Calcification reduced the content of micronutrients and Al in the soil, as well as their content in the plant. Applied doses of lime or dolomite of 4 t ha−1 almost completely neutralized the high to toxic content of mobile Al in the soil, but the values in the leaves although reduced were still high. In all applied treatments, high and very high concentrations of available forms of Fe and Mn in the soil and/or leaves and fruits were significantly reduced. However, the Mn concentrations in the soil, leaves, and raspberry fruits were very high. Calcification did not reduce the available Cu in the soil, while this effect was observed in raspberry leaves and fruits where the Cu concentrations were within optimal values. After calcification, the Zn and B concentrations decreased in the soil and plant, but they mostly remained within the optimal values. The results indicate that due to the very high concentrations of Al and Mn in the soil and plant after lime application, additional doses of lime materials in more than one season are required. [ABSTRACT FROM AUTHOR]

Dephosphorization slag is primarily composed of CaO–SiO2–FeO–P2O5 slag system. As it contains abundant valuable components, dephosphorization slag is considered a potential material to restore the degraded acid soil. To efficiently supply Ca, Si, Fe, and P elements for acid soil, the dissolution behavior of dephosphorization slag with high P2O5 content in the weakly acidic solution was investigated. It was found that the existence of citric acid could significantly promote the dissolution of slag in the aqueous solution. Most of the Ca, Si, and P was dissolved from slag at pH 5, and the Fe dissolution ratio reached 36.9%. In this case, the precipitation of Fe3(PO4)2∙8H2O was suppressed, and the majority of C2S–C3P solid phase and matrix phase was dissolved while wustite remained in the residue. The dissolution ratios of main elements from slag decreased dramatically as the pH increased. Only in the weakly acidic solution, it could make full use of dephosphorization slag, and large amounts of nutrient elements were simultaneously supplied. The dissolution ratios of nutrient elements decreased with the increase in particle size. The dissolution kinetics of slag in the citric acid solution followed the shrinking core model. [ABSTRACT FROM AUTHOR]

In the current context of the increase in the amount of municipal solid waste as a result of the development of urbanization, in this paper we have analyzed the impact of the use of fly ash obtained from the incineration of municipal solid waste in agriculture on the development of plants as an improver of acidic soils due to the nutrients it contains. We presented ash treatment methods to reduce the content of heavy metals and salts. Based on the studies in the literature, it was found that by adding certain concentrations of fly ash to degraded soils, the quality, porosity, and texture of the soil are improved; the yield of certain crops increases; the water retention capacity of the soil and soil aeration are improved; the density of the soil bulk; the compactness of the soil is reduced; the pH value is optimized; the electrical conductivity of the soil is increased; the crust formation is reduced; and it provides micronutrients to the soil. In the context of the circular economy, by using fly ash as an organic fertilizer in agriculture, the amount of chemical fertilizers harmful to agricultural crops is reduced, the problem of ash storage is solved, and thus it no longer pollutes the environment.

In our study, we analyzed 30years of climatological data revealing the bean production risks for Western Amazonia. Climatological profiling showed high daytime and nighttime temperatures combined with high relative humidity and low vapor pressure deficit. Our understanding of the target environment allows us to select trait combinations for reaching higher yields in Amazonian acid soils. Our research was conducted using 64 bean lines with different genetic backgrounds. In high temperatures, we identified three water use efficiency typologies in beans based on detailed data analysis on gasometric exchange. Profligate water spenders and not water conservative accessions showed leaf cooling, and effective photosynthate partitioning to seeds, and these attributes were found to be related to higher photosynthetic efficiency. Thus, water spenders and not savers were recognized as heat resistant in acid soil conditions in Western Amazonia. Genotypes such as BFS 10, SEN 52, SER 323, different SEFs (SEF 73, SEF 10, SEF 40, SEF 70), SCR 56, SMR 173, and SMN 99 presented less negative effects of heat stress on yield. These genotypes could be suitable as parental lines for improving dry seed production. The improved knowledge on water-use efficiency typologies can be used for bean crop improvement efforts as well as further studies aimed at a better understanding of the intrinsic mechanisms of heat resistance in legumes.

Strong and healthy saplings are a prerequisite to establish a successful forest. Therefore, an attempt has been made to develop the best package for nutrient supplementation to raise healthy Acacia mangium saplings, especially in acidic soil. The seeds were sown in pots, receiving different combinations of Arbuscular mycorrhizal (AM), Rhizobium inoculation with application of lime, and mustard oil cake (MOC). The highest spore count and infection percentage (3220 kg−1 soil and 69) were recorded in the AM + MOC + R treated pot, whereas the lowest (2553 kg−1 soil and 37) were recorded in the AM + L treated pot. Nitrogen concentration and uptake in the sapling were higher in the Rhizobium-inoculated treatments than the uninoculated ones. The sulfur concentration and uptake were higher in the MOC-supplemented treatment. Similarly, the P, K, Ca, and Mg concentrations and uptakes were higher in the limed treatments than the unlimed ones. The micronutrient concentration and uptake were higher in the unlimed treatments compared to the lime practice. The concentration of N in Rhizobium-treated pots, P and K in lime-treated pots, and S in MOC-treated pots were increased, whereas the soil pH decreased in all treatments except in the integrated package (AM + MOC + R + L) after 120 days. The Ca and Mg were reduced in all treatments, whereas micronutrients were reduced in all packages except the control. Under different nutrient management practices, plant height and stem girth continuously increased by 9.5 to 12 cm and 3 to 4 times, respectively. The production of robust saplings required integrated application of lime, MOC, AM, and Rhizobium in an acid soil that facilitated better root growth with availability of adequate nutrients for saplings. [ABSTRACT FROM AUTHOR]

In our study, we analyzed 30years of climatological data revealing the bean production risks for Western Amazonia. Climatological profiling showed high daytime and nighttime temperatures combined with high relative humidity and low vapor pressure deficit. Our understanding of the target environment allows us to select trait combinations for reaching higher yields in Amazonian acid soils. Our research was conducted using 64 bean lines with different genetic backgrounds. In high temperatures, we identified three water use efficiency typologies in beans based on detailed data analysis on gasometric exchange. Profligate water spenders and not water conservative accessions showed leaf cooling, and effective photosynthate partitioning to seeds, and these attributes were found to be related to higher photosynthetic efficiency. Thus, water spenders and not savers were recognized as heat resistant in acid soil conditions in Western Amazonia. Genotypes such as BFS 10, SEN 52, SER 323, different SEFs (SEF 73, SEF 10, SEF 40, SEF 70), SCR 56, SMR 173, and SMN 99 presented less negative effects of heat stress on yield. These genotypes could be suitable as parental lines for improving dry seed production. The improved knowledge on water-use efficiency typologies can be used for bean crop improvement efforts as well as further studies aimed at a better understanding of the intrinsic mechanisms of heat resistance in legumes. [ABSTRACT FROM AUTHOR]

This study evaluated metal availability under acidic soil conditions and identified the solid phases that govern their solubility using Baker soil test. Free metal ion activity (Mn+) expressed as negative logarithm value (pMn+ = -log10 Mn+) of iron (pFe3+), manganese (pMn2+), copper (pCu2+), zinc (pZn2+), nickel (pNi2+), cadmium (pCd2+), and lead (pPb2+) ranged from 17.5 to 21.3, 5.2 to 8.4, 12.2 to 15.3, 9.3 to 11.9, 11.5 to 14.8, 11.8 to 15.1, and 10.9 to 13.4, respectively. The activities of Fe, Cu, Zn, Ni, Cd, and Pb in the soil solution are likely to be buffered by exchange reactions rather than precipitation-dissolution reactions. However, bixybite and manganite oxides are likely to govern the free Mn2+ activity in the soils. Based on intensity and quantity parameters, the soils were found to have sufficient supply power for plant essential elements (i.e. Fe, Mn, Cu, Zn, and Ni) except in the coarse-textured soils of Kosi. Nevertheless, the toxicity of iron in Someshwar and cadmium in Dhaili soils is expected under the prevailing soil conditions. The generated information on the solubility vis-à-vis availability of metals under acidic soil conditions will contribute to enlarge a field of research which is crucial for land management and deserves more attention, particularly in the fragile mountainous ecosystem. [ABSTRACT FROM AUTHOR]

The long-term impact of integrated nutrient management (INM) experiment under cereal- vegetables- legume was undertaken to investigate the effect of organic and inorganic sources of nutrients with inclusion of microbial inoculants/biofertilizer and lime on different inorganic fractions of phosphorus (P) in acidic soil. The test crop maize was 17th crop in the sequence. The INM practices include i) soil test dose (STD) as pure inorganic source ii) Combination of inorganic with organic in the form of either farm yard manure (FYM)@5 t ha−1 or vermicompost @2.5 t ha−1 iii) inclusion of microbial inoculant/biofertilizer (Azotobacter, Azospirillum and PSB (1:1:1) and soil amendment in the form lime @ 0.2lime requirement (LR) compared with iv) absolute control, i.e., without any fertilization. The results showed that integration of organics with STD increased the grain yield by 52% over STD but only 8% yield increment was observed in INM practices compared to organics and inorganics only. Cultivation without any fertilizer caused a decrease in available -P, saloid P(Sal-P), aluminum phosphorus (Al–P), calcium phosphorus (Ca–P) and total P but there is accumulation of iron phosphorous (Fe-P), reductant Phosphorous (Red-P) and occluded Phosphorous (Occ-P).All the fractions of inorganic P were relatively higher in the treatments receiving full INM package of practices. Integration of organic manure, biofertilizers, lime as soil ameliorant with inorganic fertilizers is a sustainable approach for P mobilization and solubilization from non-labile pool to labile pool of P in soil. [ABSTRACT FROM AUTHOR]

The main constraint in the extensification of maize on the dry land of acid soil is the low availability of P in soil. This study aimed to determine the effect and the optimal dose of humic acid on the growth and yield of maize on acid soil. This research was conducted from February to May 2017 at Tri Dharma Field Laboratory, Faculty of Agriculture, Gadjah Mada University. Acid soil with low P availability used was from sub-district Cigudeg and Jasinga, West Java. The research was arranged in Randomized Complete Block Design (RCBD) with 2 factors. The first factor was maize cultivar, namely Bisi 2 and Pioneer 35. The second factor was the rate of humic acid and NPK fertilizer, consisting of 0 kg.ha-1 (without) NPK and 0% (without) humic acid, NPK + 0% (without) humic acid, NPK + 5% humic acid, NPK + 10% humic acid, and NPK + 15% humic acid. NPK fertilizer applied was NPK 16:16:16 at a dose of 350 kg.ha-1. The results showed that humic acid application on acid soil increased C-humic content in the soil, soil P availability, total dry weight of the plant, and kernel dry weight at harvest (15 weeks after planting). The increase in soil P availability did not improve the plant growth but increased the accumulation of plant biomass. The application of humic acid at 15% (52.5 kg.ha-1) combined with NPK fertilizer on acid soil significantly increased total dry weight of plant and kernel dry weight up to 13.14% and 21.81%, respectively, thus, it is recommended for maize cultivation on acid soil.

Soil samples were collected during 2018 from a long-term field experiment on soybean [Glycine max (L.) Merr.]- wheat (Triticum aestivum L.) system continuing since 1972 at Birsa Agriculture University, Jharkhand. The samples were analysed for available major and micro nutrient and biological properties at IARI, New Delhi. The treatments consisted of control, 100% N, 100% NP, 50% NPK, 100% NPK, 150% NPK, 100% NPK + FYM and 100% NPK + Lime. Highest grain yield of wheat was obtained with 100% NPK + FYM followed by 100% NPK + Lime. Whereas, in soybean, 100% NPK + Lime treatment recorded the highest yield, followed by 100% NPK + FYM. The highest available N (218 kg/ha) was found under 150% NPK, which was statistically similar to 100% NPK + FYM. Moreover, highest Bray-P (169 kg/ha) and available K (161 kg/ha) was observed in 100% NPK + FYM and 150% NPK treatment respectively. The DTPA extractable Fe, Mn, Zn and Cu were recorded in the range of 13.9-41.8 mg/kg, 31.1-60.6 mg/ kg, 0.64-1.94 mg/kg and 0.71-1.28 mg/kg, respectively under different nutrient management practices. Treatment 100% NPK + FYM recorded the maximum contents of available micronutrients. Acid phospho-monoesterase (AMP) activity and microbial pools such as microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP) were also found to be highest in 100% NPK + FYM treatment.

A microcosm study was established using three arable soils differing in both physicochemical properties and AOB or AOA dominance of ammonia oxidization. Nitrification and N2O emissions were quantified under 10 Pa C2H2, 1-octyne, or 3,4-dimethylpyrazole phosphate (DMPP), and the community composition and abundance of AOA and AOB were assessed. Amendment of soil with DMPP had a comparable effect to 1-octyne on AOB activities, composition, and N2O emissions across soils. By blocking AOB activity, both DMPP and 1-octyne supported higher rates of AOA growth in both the acid and alkaline soils. Approximately, 50% of ammonia-oxidizing activity in the acid soil was attributed to AOB activity by phylotypes affiliated with Nitrosomonas communis. When AOB were blocked by DMPP or 1-octyne across all soils, recovery of AOA communities was associated with the increased abundance of Nitrososphaera viennesis. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to explore the effects of manganese stress on acid soil nitrogen conversion, enzyme activity and sugarcane nitrogen absorption and utilization, and provide a reference for the rational fertilization of sugarcane on acid soil. [Method JSimula- ted acidic soil manganese stress cultivation experiment in the indoor, and the sugarcane pot experiment in the glasshouse were carried out, and the difference of soil nitrogen component content, pH and soil enzyme activity under manganese stress and its relationship with sugarcane nitrogen absorption and accumulation relationship were measyured and analyed. [Result] Manganese stress significantly increased soil ammonium nitrogen content and net ammonification rate(P < 0. 05,the same as below), significantly reduced soil nitrate nitrogen content and net nitrification rate, and significantly increased soil net mineralization rate. At the same time, manganese stress significantly reduced soil urease activity and significantly increased soil invertase activity, but had no significant effect on soil protease activity (P >0. 05). The results of correlation analysis showed that soil urease activity was significantly and extremely (P < 0. 01, the same as below) positively correlated with soil ammonium nitrogen content and pH, soil protease activity was significantly positively correlated with soil ammonium nitrogen content, and extremely and significantly negatively correlated with soil nitrate nitrogen content and net nitrification rate respectively. Under manganese stress, sugarcane plant height, biomass, plant nitrogen accumulation and nitrogen absorption efficiency were significantly reduced. [Conclusion] Manganese stress can inhibit the nitrification of acid soils, reduce the conversion of ammonium nitrogen to nitrate nitrogen, and at the same time reduce the activity of soil urease and increase the activity of soil invertase, thereby reducing the available nitrogen content of sugar- cane in acid soil, reducing the absorption and utilization of nitrogen by sugarcane. [ABSTRACT FROM AUTHOR]

Aluminium (Al) is solubilized into a phytotoxic form [Al(H2O)6 3+] in acid soil, which is known as Al3+. Al toxicity is the primary growth-limiting factor for plants in acid soils. Breeding of rice for enhanced Al tolerance considered to be an important approach for increasing grain yield in acid soils. In the present endeavour, we studied the effects of toxic levels of Al on vigour of rice seedlings under hydroponics and finally grouped the genotypes with varied degree of tolerance to Al toxicity based on vigour index. Good seed germination (%), high speed of germination and high vigour index indicate uniform crop stand. Germination ranged from 72-99.50%. It was significantly high for almost all genotypes (-80%) except three. The speed of germination ranged from 9.75 to 29.99 in control. Most of the genotypes showed high speed of germination (-15.00) except a few. Remarkable reduction in seedling vigour has been reported earlier under stressed environments. Low seedling vigour has been identified as the key factor responsible for poor germination and uneven seedling establishment. Based on the vigour index, nine genotypes were classified as tolerant, 19 as moderately tolerant and 12 as susceptible. Among the tolerant genotypes, UBKVR-3 showed maximum value for vigour index followed by UBKVR 19, UBKVR 9, UBKVR 8, Parijat, MTU 1075 and Radhunipagal. Most susceptible genotypes based on seedling vigour were found to be Pusa Basmati, Aiswarya and Pratikha. It is to be mentioned that till now there is no clear and distinct divisions of vigour index for classification into different levels of tolerance towards Al toxicity. In our study, we have identified distinct classes for grouping of genotypes endowed with different levels of tolerance. The values of the vigour index depend upon root length, shoot length or some other characters used for calculation of vigour index. The magnitude of the vigour index may not be useful for classification uniformly across the crops as well as genotypes within the crop. Hence, the procedure used in this work may overcome the above mentioned constraints. [ABSTRACT FROM AUTHOR]

The morphological traits of alfalfa under acid soil conditions with different mobile aluminium (Al) concentrations were investigated. The study site was Vėžaičiai Branch of the Lithuanian Research Centre for Agriculture and Forestry, 55°70 N, 21°49 E. The experiment featuring the 30 most Al-tolerant alfalfa accessions (populations and cultivars), determined from laboratory trials was established on a Bathygleyic Dystric Retisol in 2018. In 2019 and 2020, the biological and morphological traits were evaluated: plant regrowth, plant height before flowering, wintering, leafiness, stem thickness, plant vigour, stem density, seed yield and resistance to spring black stem leaf spot. The resistance of alfalfa to mobile Al toxicity was determined using a filter-based screening method of selection cycles C1 and C2. The accessions grown in the soil with mobile Al (20.6–23.4 mg/kg) showed better tolerance to Al toxicity in the cycle C2. The hypocotyl tolerance index of these accessions was better at 8, 16, 32 and 64 mm AlCl3 concentrations in the cycle C2. The correlation analysis showed strong significant positive and negative relationships between the morphological traits. A cluster analysis showed that the accessions, grown in the soil with mobile Al (20.6–23.4 mg/kg) were the most resistant to Al toxicity in the cycle C2. These accessions produced a better seed yield and demonstrated lower values of morphological traits compared to cluster 2. Also, these accessions are considered as tolerant to mobile Al toxicity and might be used as donors in breeding for Al toxicity tolerance. [ABSTRACT FROM AUTHOR]

Background Sugarcane is a crop of global importance and has been expanding to areas with soils containing high levels of exchangeable aluminum (Al), which is a limiting factor for crop development in acidic soils. The study of the sugarcane physiological and nutritional behavior together with patterns of gene expression in response to Al stress may provide a basis for effective strategies to increase crop productivity in acidic soils. Methods Sugarcane cultivars were evaluated for physiological parameters (photosynthesis, stomatal conductance, and transpiration), nutrient (N, P, K, Ca, Mg, and S) and Al contents in leaves and roots and gene expression, of the genes MDH, SDH by qPCR, both related to the production of organic acids, and SOD, related to oxidative stress. Results Brazilian sugarcane RB867515, RB928064, and RB935744 cultivars exhibited very different responses to induced stress by Al. Exposure to Al caused up-regulation (SOD and MDH) or down-regulation (SDH, MDH, and SOD), depending on the cultivar, Al level, and plant tissue. The RB867515 cultivar was the most Al-tolerant, showing no decline of nutrient content in plant tissue, photosynthesis, transpiration, and stomatal conductance after exposure to Al; it exhibited the highest Al content in the roots, and showed important MDH and SOD gene expression in the roots. RB928064 only showed low expression of SOD in roots and leaves, while RB935744 showed important expression of the SOD gene only in the leaves. Sugarcane cultivars were classified in the following descending Al-tolerance order: RB867515 > RB928064 = RB935744. These results may contribute to the obtention of Al-tolerant cultivars that can play their genetic potential in soils of low fertility and with low demand for agricultural inputs; the selection of potential plants for breeding programs; the elucidation of Al detoxification mechanisms employed by sugarcane cultivars.

Background: Sugarcane is a crop of global importance and has been expanding to areas with soils containing high levels of exchangeable aluminum (Al), which is a limiting factor for crop development in acidic soils. The study of the sugarcane physiological and nutritional behavior together with patterns of gene expression in response to Al stress may provide a basis for effective strategies to increase crop productivity in acidic soils. Methods: Sugarcane cultivars were evaluated for physiological parameters (photosynthesis, stomatal conductance, and transpiration), nutrient (N, P, K, Ca, Mg, and S) and Al contents in leaves and roots and gene expression, of the genes MDH, SDH by qPCR, both related to the production of organic acids, and SOD, related to oxidative stress. Results: Brazilian sugarcane RB867515, RB928064, and RB935744 cultivars exhibited very different responses to induced stress by Al. Exposure to Al caused up-regulation (SOD and MDH) or down-regulation (SDH, MDH, and SOD), depending on the cultivar, Al level, and plant tissue. The RB867515 cultivar was the most Al-tolerant, showing no decline of nutrient content in plant tissue, photosynthesis, transpiration, and stomatal conductance after exposure to Al; it exhibited the highest Al content in the roots, and showed important MDH and SOD gene expression in the roots. RB928064 only showed low expression of SOD in roots and leaves, while RB935744 showed important expression of the SOD gene only in the leaves. Sugarcane cultivars were classified in the following descending Al-tolerance order: RB867515 > RB928064 = RB935744. These results may contribute to the obtention of Al-tolerant cultivars that can play their genetic potential in soils of low fertility and with low demand for agricultural inputs; the selection of potential plants for breeding programs; the elucidation of Al detoxification mechanisms employed by sugarcane cultivars. [ABSTRACT FROM AUTHOR]

Organic carbon content in acid soils of Northeastern India is high; however, productivity is limited due to several biotic and abiotic stresses. Several studies in this region elucidated the effect of nutrient management on soil organic carbon, soil fertility and productivity in isolation. Relatively limited information is available on changes in soil biochemical properties and processes owing to nutrient management, which may be a guide in adopting appropriate techniques to maintain soil quality. To achieve the objectives, surface and subsurface soil samples were collected from a long-term experiment (5 years) and soil biochemical properties viz. soil organic carbon (SOC), total organic carbon (TOC), soil microbial biomass carbon (SMBC), microbial biomass nitrogen (SMBN), microbial biomass phosphorus (SMBP), glomalin and soil enzymes were analyzed. It was found that nutrient managements can lead to a significant positive impact on organic carbon fractions (SOC, TOC), microbial biomass fractions (SMBC, SMBN, SMBP), and enzyme activities. As microbial properties and enzymes activities are sensitive to management practices, they can be better indicators to assess soil quality changes. [ABSTRACT FROM AUTHOR]

The root phosphorus (P) uptake efficiency (RE), defined as plant P uptake per unit root mass or root area, may contribute to the P efficiency of upland rice grown in acid, P-deficient soils. The identification of root traits conferring RE of rice has been compromised by the lack of attention given to P speciation when evaluating P-mining mechanisms. Here we disentangled the effect of soluble organic P (PO) from that of total soluble P (PT) on the RE in rice seedlings in acid soil. Six rice genotypes were grown for 21 days in P-deficient substrates, i.e. a sample of an acid mineral soil, an acid peat and a mixture thereof. Each of the three substrates were amended with different P doses, partially limed and incubated, yielding substrates with significant differences in total soluble P (0.005–0.41 mg P/L) and in the percentage of organic P in that pool (PO/PT, 0–55%). Plants showed a large growth response to the P addition. There was a significant genotypic variation in P uptake (0.9–1.5mg P/plant) and RE (4.4–8.3 mg P/g root mass) under moderate P deficiency but these traits were unaffected by the PO/PT in the soluble fraction of the substrates. Along the same lines, phosphatase activity in the rhizosphere soil was unaffected by genotypes and did not explain the RE among all data (R2 = 0.17, ns). A multiple regression model showed that the RE of rice seedlings was mainly affected by the inherent genotypic effects, the PO/PT and the total soluble P concentration in soil (R2 = 0.73), while the genotype-PO/PT interaction only marginally improved the RE model (R2 = 0.78). This suggests limited genotypic effects due to the better use of organic P. A root elongation test in the acid mineral soil that was either or not limed suggests that the differences in acid soil tolerance may play a larger role in the genotypic performance of RE than organic P utilization potential. [ABSTRACT FROM AUTHOR]

Acidic soils constrain plant growth and development in natural and agricultural ecosystems because of the combination of multiple stress factors including high levels of Fe3+, toxic levels of Al3+, low phosphate (Pi) availability and proton rhizotoxicity. The transcription factor SENSITIVE TO PROTON RHIZOTOXICITY (STOP1) has been reported to underlie root adaptation to low pH, Al3+ toxicity and low Pi availability by activating the expression of genes involved in organic acid exudation, regulation of pH homeostasis, Al3+ detoxification and root architecture remodeling in Arabidopsis thaliana. However, the mechanisms by which STOP1 integrates these environmental signals to trigger adaptive responses to variable conditions in acidic soils remain to be unraveled. It is unknown whether STOP1 activates the expression of a single set of genes that enables root adaptation to acidic soils or multiple gene sets depending on the combination of different types of stress present in acidic soils. Previous transcriptomic studies of stop1 mutants and wild-type plants analyzed the effect of individual types of stress prevalent in acidic soils. An integrative study of the transcriptional regulation pathways that are activated by STOP1 under the combination of major stresses common in acidic soils is lacking. Using RNA-seq, we performed a transcriptional dissection of wild-type and stop1 root responses, individually or in combination, to toxic levels of Al3+, low Pi availability, low pH and Fe excess. We show that the level of STOP1 is post-transcriptionally and coordinately upregulated in the roots of seedlings exposed to single or combined stress factors. The accumulation of STOP1 correlates with the transcriptional activation of stress-specific and common gene sets that are activated in the roots of wild-type seedlings but not in stop1. Our data indicate that perception of low Pi availability, low pH, Fe excess and Al toxicity converges at two levels via STOP1 signaling: post-translationally through the regulation of STOP1 turnover, and transcriptionally, via the activation of STOP1-dependent gene expression that enables the root to better adapt to abiotic stress factors present in acidic soils.

Globally, there has been an increase in the frequency of landslides which is the result of slope failures. The combination of high intensity rainfall and high temperature resulted in the formation of acidic soil which is detrimental to the healthy growth of plants. Proper plant coverage on slopes is a prerequisite to mitigate and rehabilitate the soil. However, not all plant species are able to grow in marginal land. Thus, this study was undertaken to find a suitable slope plant species. We aimed to evaluate the effect of different soil pH on root profiles and growth of three different potential slope plant species namely, Melastoma malabathricum, Hibiscus rosa-sinensis and Syzygium campanulatum. M. malabathricum showed the highest tolerance to acidic soil as it recorded the highest plant height and photosynthetic rate. The root systems of M. malabathricum, H. rosa-sinensis and S. campanulatum were identified as M, VH- and R-types, respectively. The study proposed M. malabathricum which possessed dense and shallow roots to be planted at the toe or top of the slope while H. rosa-sinensis and S. campanulatum to be planted in the middle of a slope. S. campanulatum consistently recorded high root length and root length density across all three types of soil pH while M. malabathricum showed progressive increase in length as the soil pH increased. The root average diameter and root volume of M. malabathricum outperformed the other two plant species irrespective of soil pH. In terms of biomass, M. malabathricum exhibited the highest root and shoot dry weights followed by S. campanulatum. Thus, we propose M. malabathricum to be planted on slopes as a form of soil rehabilitation. The plant species displayed denser rooting, hence a stronger root anchorage that can hold the soil particles together which will be beneficial for slope stabilization.

Russia contains the largest areas of soil with excessive acidity in the world. According to the results of agrochemical surveys of arable lands, the area of acidic soils (pH less than 5.5) is currently about 65 million hectares. The losses in agricultural products calculated in grain per year amount to 15-20 million tons. The negative effect of acid soil on plants is explained by the low content of exchangeable bases and the presence of large quantities of mobile forms of aluminum (2-20% from the weight of the soil). Absorption and assimilation of aluminum by plants depends on the forms by which it is represented in acidic soils. The importance of aluminum in plant life is ambiguous, as the reports on the toxic effect of aluminum ions are more numerous. High concentrations of aluminum directly or indirectly affect the processes of vital activity of plants: water regime, nitrogen metabolism, mineral nutrition, photosynthesis, oxidation-reduction reactions. Phytotoxic metal ions also affect various physiological and biochemical processes in plants, stimulate numerous anatomical and morphological changes. Excess aluminum ions in soil disrupt the mineral nutrition of plants. Various agrochemical methods are used to reduce the harmful toxic effect of aluminum ions on plants. Most plants are sensitive to high concentrations of aluminum. The resistance to toxic concentrations of metal ions in plants is due to the action of several mechanisms that are characteristic of each species. Some species of plants have protective mechanisms by which the adverse effects of toxic ions are reduced or completely eliminated. It has been established that root growth is the better indicator of resistance than the growth of the above-ground plant parts. The methods of diagnosing sensitivity to aluminum in the early stages of plant development are based on the change in root length after exposure to a stress factor. Knowledge of the genetic and physiological foundations of plant resistance to high concentrations of ions of heavy metals and aluminum is necessary for the search for tolerant genotypes of cultivated plants.

The evaluation of disease resistance is considered an important aspect of phenotyping for crop improvement. Identification of advanced lines of the common bean with disease resistance contributes to improved grain yields. This study aimed to determine the response of the photosynthetic apparatus to natural pathogen infection by using chlorophyll (Chla) fluorescence parameters and their relationship to the agronomic performance of 59 common bean lines and comparing the photosynthetic responses of naturally infected vs. healthy leaves. The study was conducted over two seasons under acid soil and high temperature conditions in the western Amazon region of Colombia. A disease susceptibility index (DSI) was developed and validated using chlorophyll a (Chla) fluorescence as a tool to identify Mesoamerican and Andean lines of common bean (Phaseolus vulgaris L.) that are resistant to pathogens. A negative effect on the functional status of the photosynthetic apparatus was found with the presence of pathogen infection, a situation that allowed the identification of four typologies based on the DSI values ((i) moderately resistant; (ii) moderately susceptible; (iii) susceptible; and (iv) highly susceptible). Moderately resistant lines, five of them from the Mesoamerican gene pool (ALB 350, SMC 200, BFS 10, SER 16, SMN 27) and one from the Andean gene pool (DAB 295), allocated a higher proportion of energy to photochemical processes, which increased the rate of electron transfer resulting in a lower sensitivity to disease stress. This photosynthetic response was associated with lower values of DSI, which translated into an increase in the accumulation of dry matter accumulation in different plant organs (leaves, stem, pods and roots). Thus, DSI values based on chlorophyll fluorescence response to pathogen infection could serve as a phenotyping tool for evaluating advanced common bean lines. Six common bean lines (ALB 350, BFS 10, DAB 295, SER 16, SMC 200 and SMN 27) were identified as less sensitive to disease stress under field conditions in the western Amazon region of Colombia, and these could serve as useful parents for improving the common bean for multiple stress resistance.

Malate efflux from roots, which is regulated by the transcription factor STOP1 (SENSITIVE-TO-PROTON-RHIZOTOXICITY1) and mediates aluminum-induced expression of ALUMINUM-ACTIVATED-MALATE-TRANSPORTER1 (AtALMT1), is critical for aluminum resistance in Arabidopsis thaliana. Several studies showed that AtALMT1 expression in roots is rapidly observed in response to aluminum; this early induction is an important mechanism to immediately protect roots from aluminum toxicity. Identifying the molecular mechanisms that underlie rapid aluminum resistance responses should lead to a better understanding of plant aluminum sensing and signal transduction mechanisms. In this study, we observed that GFP-tagged STOP1 proteins accumulated in the nucleus soon after aluminum treatment. The rapid aluminum-induced STOP1-nuclear localization and AtALMT1 induction were detected in the presence of a protein synthesis inhibitor, suggesting that post-translational regulation is involved in these events. STOP1 also regulated rapid aluminum-induced expression for other genes that carry a functional/high-affinity STOP1-binding site in their promoter, including STOP2 , GLUTAMATE-DEHYDROGENASE1 and 2 (GDH1 and 2). However STOP1 did not regulate Al resistance genes which have no functional STOP1-binding site such as ALUMINUM-SENSITIVE3 , suggesting that the binding of STOP1 in the promoter is essential for early induction. Finally, we report that GDH1 and 2 which are targets of STOP1, are novel aluminum-resistance genes in Arabidopsis. [ABSTRACT FROM AUTHOR]

Reducing greenhouse gas emissions and increasing agronomic productivity by sustaining soil organic matter and refining soil fertility have become the main concerns for agricultural scientists. There is a new approach to decrease greenhouse gas emissions, soil C sinks, and improve soil quality using biochar. Soil acidification is improved by applying lime or other acid-neutralizing materials. Additionally, Ca and Mg can increase by applying lime. The availability of Ca, Mg, and K in the soil is significantly affected by the application rate of biochar spread separately or combined with chemical fertilizers. Soil nutrients and maize (Zea mays L.) yield are highly influenced by the use of lime and biochar. Biochar can improve the ecosystem by reducing soil CO2 emissions from agricultural practices. The inconsistent results and clarifications from various studies highlight the importance of relating the impact of different biochar rates on CO2 emissions and maize yield. This review summarizes the properties of biochar, provides the scientific reference for its application to achieve high and good quality maize and reduce CO2 emissions. [ABSTRACT FROM AUTHOR]

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This paper is aimed to evaluate the behaviour of 25 winter barley genotypes, tested on the acid soils at ARDS Livada, during the 2016-2018 period, in two ways of sowing: one at a distance of 12.5 cm between the rows and the other one at the distance of 25cm. The variance analysis led to the fact that the sowing distance (D), as a variation source, does not significantly influence the yield. On the other hand, the variety (S) and the interaction of distance and years between the barley varieties, had a significant influence on the yield. The regression analysis and the variation coefficient led to the identification of the most productive, stable and adaptable genotypes, specific to this area (Ametist, Cardinal, Artemis, Smarald). The larger sowing distance positively influenced the thousand grain weight, the hectolitre mass and the number and weight of the barley grains/ears. The attacks of the pathogen agents have been reduced (with 3-6%) and the resistance to lodging has been increased (with over 30%). [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity is the primary limiting factor of crop production on acid soils. Tibetan wild barley germplasm is a valuable source of potential genes for breeding barley with acid and Al tolerance. We performed microRNA and RNA sequencing using wild (XZ16, Al-tolerant; XZ61, Al-sensitive) and cultivated (Dayton, Al-tolerant) barley. A novel homeobox-leucine zipper transcription factor, HvHOX9 , was identified as a target gene of miR166b and functionally characterized. HvHOX9 was up-regulated by Al stress in XZ16 (but unchanged in XZ61 and Dayton) and was significantly induced only in root tip. Phylogenetic analysis showed that HvHOX9 is most closely related to wheat TaHOX9 and orthologues of HvHOX9 are present in the closest algal relatives of Zygnematophyceae. Barley stripe mosaic virus-induced gene silencing of HvHOX9 in XZ16 led to significantly increased Al sensitivity but did not affect its sensitivity to other metals and low pH. Disruption of HvHOX9 did not change Al concentration in the root cell sap, but led to more Al accumulation in root cell wall after Al exposure. Silencing of HvHOX 9 decreased H+ influx after Al exposure. Our findings suggest that miR166b /HvHOX9 play a critical role in Al tolerance by decreasing root cell wall Al binding and increasing apoplastic pH for Al detoxification in the root. [ABSTRACT FROM AUTHOR]

Acidic soils constrain plant growth and development in natural and agricultural ecosystems because of the combination of multiple stress factors including high levels of Fe3+, toxic levels of Al3+, low phosphate (Pi) availability and proton rhizotoxicity. The transcription factor SENSITIVE TO PROTON RHIZOTOXICITY (STOP1) has been reported to underlie root adaptation to low pH, Al3+ toxicity and low Pi availability by activating the expression of genes involved in organic acid exudation, regulation of pH homeostasis, Al3+ detoxification and root architecture remodeling in Arabidopsis thaliana. However, the mechanisms by which STOP1 integrates these environmental signals to trigger adaptive responses to variable conditions in acidic soils remain to be unraveled. It is unknown whether STOP1 activates the expression of a single set of genes that enables root adaptation to acidic soils or multiple gene sets depending on the combination of different types of stress present in acidic soils. Previous transcriptomic studies of stop1 mutants and wild-type plants analyzed the effect of individual types of stress prevalent in acidic soils. An integrative study of the transcriptional regulation pathways that are activated by STOP1 under the combination of major stresses common in acidic soils is lacking. Using RNA-seq, we performed a transcriptional dissection of wild-type and stop1 root responses, individually or in combination, to toxic levels of Al3+, low Pi availability, low pH and Fe excess. We show that the level of STOP1 is post-transcriptionally and coordinately upregulated in the roots of seedlings exposed to single or combined stress factors. The accumulation of STOP1 correlates with the transcriptional activation of stress-specific and common gene sets that are activated in the roots of wild-type seedlings but not in stop1. Our data indicate that perception of low Pi availability, low pH, Fe excess and Al toxicity converges at two levels via STOP1 signaling: post-translationally through the regulation of STOP1 turnover, and transcriptionally, via the activation of STOP1-dependent gene expression that enables the root to better adapt to abiotic stress factors present in acidic soils. [ABSTRACT FROM AUTHOR]

Purpose : The use of phosphorhizobacteria and organic fertilizers can increase the P uptake and solubility as well as promote the growth and yield of maize in acid soil. The objective of the study was to evaluate of P fertilization efficiency by adding phosphorhizobacteria and organic fertilizers and to investigate its influence in the growth and yield of maize. Research Method : The experiment was conducted at the experimental field of Center for Horticulture Seed and Plant Variety Development, West Java and Soil Biology Laboratory at the Department of Soil Science, Faculty of Agriculture, Universitas Padjadjaran. The factors of the experiment were: phosphorhizobacteria and organic fertilizers (control, phosphorhizobacteria 107 cfu/ mL, organic fertilizers 5 ton ha-1, combinations of phosphorhizobacteria 107 cfu/ mL + organic fertilizers 5 ton ha-1) and the level of inorganic P fertilization (0, 200, 180, 160, and 140 kg P ha-1) arranged as randomized block design factorial, consisting of 20 treatments and 3 replications. Findings : The results showed that application of phosphorhizobacteria 107 cfu/ mL can increase P solubility up to 21.13 ppm. The interactions between phosphorhizobacteria 107 cfu/mL and organic fertilizers 5 ton ha-1 with 180 kg inorganic P ha-1 were capable to increase maize plant height by 183.07 cm which were measured at 14 weeks after planting. Applications of organic fertilizers 5 ton ha-1 and dosage of inorganic P fertilizers 160 kg ha-1 can escalate agronomic effectiveness up to 29.20%. Limitations : Limited availability of historical data was a constraint during the study and that was avoided using data for a base year. Originality / Value : It is better to conduct a study on nitrogen and potassium rhizobacteria and organic fertilizer in order to find out nitrogen and potassium fertilization efficiency for maize in acid soil because these evidence are useful to the farmer, trader and planners. [ABSTRACT FROM AUTHOR]

Changes in root exudates and rhizospheric microbial functional capacities involved in carbon (C) decomposition and nitrogen (N) transformation of aluminum (Al)-tolerant and Al-sensitive soybean genotypes were investigated under Al stress. Rhizosphere soils were collected from rhizobox systems with two soybean genotypes. A wide range of microbial functional capacities were determined by functional gene arrays. Microbial functional capacities of rhizospheres were distinct between Al-tolerant and Al-sensitive genotypes, which were related to exchangeable Al concentrations. Functional capacities associated with decomposition of chemically recalcitrant C were lower in Al-tolerant than Al-sensitive genotypes, which was negatively correlated with the secretion rate of succinic acid. Microbial functional capacities were higher for nitrification but lower for denitrification in the rhizosphere of Al-tolerant than Al-sensitive genotype, which coincided with higher succinic acid secretion and lower abundance of microbial oxygen stress genes. Soybean biomass increased logarithmically with nitrification capacities. We concluded that exchangeable Al concentrations, root exudation, and microbial C and N cycling capacities were intrinsically linked, which served as a key mechanism for legume genotypes toward enhancing tolerance to Al stress occurring in acid soils. [ABSTRACT FROM AUTHOR]

Globally, there has been an increase in the frequency of landslides which is the result of slope failures. The combination of high intensity rainfall and high temperature resulted in the formation of acidic soil which is detrimental to the healthy growth of plants. Proper plant coverage on slopes is a prerequisite to mitigate and rehabilitate the soil. However, not all plant species are able to grow in marginal land. Thus, this study was undertaken to find a suitable slope plant species. We aimed to evaluate the effect of different soil pH on root profiles and growth of three different potential slope plant species namely, Melastoma malabathricum, Hibiscus rosa-sinensis and Syzygium campanulatum. M. malabathricum showed the highest tolerance to acidic soil as it recorded the highest plant height and photosynthetic rate. The root systems of M. malabathricum, H. rosa-sinensis and S. campanulatum were identified as M, VH- and R-types, respectively. The study proposed M. malabathricum which possessed dense and shallow roots to be planted at the toe or top of the slope while H. rosa-sinensis and S. campanulatum to be planted in the middle of a slope. S. campanulatum consistently recorded high root length and root length density across all three types of soil pH while M. malabathricum showed progressive increase in length as the soil pH increased. The root average diameter and root volume of M. malabathricum outperformed the other two plant species irrespective of soil pH. In terms of biomass, M. malabathricum exhibited the highest root and shoot dry weights followed by S. campanulatum. Thus, we propose M. malabathricum to be planted on slopes as a form of soil rehabilitation. The plant species displayed denser rooting, hence a stronger root anchorage that can hold the soil particles together which will be beneficial for slope stabilization. [ABSTRACT FROM AUTHOR]

Although cherry-tomato is becoming more popular in the last years, there are no specific recommendations for P and K fertilization or liming strategies for this specific variety. Our aim was to assess rates of P and K and liming strategies in order to improve the yield of cherry-tomato grown on an Oxisol with a limited P-availability. Two pot experiments were developed. In the first-one, a two-factor factorial design was developed with 4 P (first-factor) and 4 K rates (second-factor), being these rates the 0%, 50%, 100%, and 200% of the recommended fertilization for tomato in South-Brazil. In the second experiment, the soil pH (4.3) was adjusted to 5.5, 6.0, and 6.5 with limestone. Soil P-availability, plant growth, diameter, number of fruits and cherry tomato yields were increased with the P addition, while a non-significant effect was observed after adding K. The highest yield was produced with 50% of the suggested amount of P for tomato in comparison with the non-fertilized plants (yield increase of 674%), while higher P rates (100% and 200%) produced a lower yield increase. The significant effect of soil liming was observed on increase of the flower bunches number when the soil pH was amended to 6.5. Cherry-tomato requirements seem to be different from the recommended for other varieties. Our results indicate that higher yields were achieved with a lower amount of chemical inputs than the recommended for tomato in general, stressing the importance of P for tomato cherry production over the other factors assessed here. [ABSTRACT FROM AUTHOR]

High nitrogen use efficiency (NUE) is important for improving crop yield. There are many nitrogen (N) fractions in soil and their uptake by crops varies. Most of the N that is taken up by plants is not native to the soil but usually from fertilizer added to the soil. However, the unbalanced use of fertilizers is currently an important issue that needs to be addressed. The objectives of this work were to determine the effects of using the recommended chemical fertilizers together with inorganic and organic amendments on (i) soil organic and inorganic N fractions, (ii) N uptake and use efficiency, and (iii) maize (Zea mays L.) dry matter production and ear yield. A randomized complete block design field trial, using maize as a test crop, was done with seven fertilizer treatments, each replicated thrice for two crop cycles. The treatments included different combinations of urea N, clinoptilolite zeolite (CZ), rice straw compost, and paddy husk compost. The variables of the study were soil N fractions, ear yield, and N use efficiency. Generally, the combined use of the recommended chemical fertilizers with CZ and organic amendments resulted in significantly higher soil N fractions, N use efficiency, and ear yield of maize for both crops. The two treatments with a 50% reduction in recommended chemical fertilizers, CZ, and rice straw compost or paddy husk compost (treatments four and six) are recommended instead of the 100% recommended chemical fertilizer treatment (treatment one). The organic materials used for these two treatments are abundantly available and will reduce the economic and environmental costs of applying large quantities of chemical fertilizers alone. [ABSTRACT FROM AUTHOR]

Soluble phosphorus (P) applied through phosphatic fertilizers is quickly converted into low soluble P compounds in soil. For evaluating fixation ability of P fertilizers laboratory incubation experiments were conducted with saline, sodic and acid soils. Phosphatic fertilizers selected were single super phosphate (SSP), diammonium phosphate (DAP), monoammonium phosphate (MAP), monopotassium phosphate (MPP) and 19:19:19 N, P2O5, K2O % (All-19). Fixation of P was computed based on the amount of P recovered after addition of P in the soil in increasing levels. At a typical P addition at 16 kg ha-1 the results were compared in all soils. In saline soil, high fixation of P occurred when DAP (12.18 kg ha-1) and MPP (11.28 kg ha-1) were applied. In sodic soil, high fixation of P resulted when SSP (7.10 kg ha-1) was applied. In acid soil, high fixation of P occurred when All -19 (12.64 kg ha-1), MAP (12.40 kg ha-1), SSP (12.22 kg ha-1), and DAP (11.74 kg ha-1) were applied. With all forms of phosphatic fertilizers fixation of added P occurred to the extent of 57.9 to 79.0 per cent in acid soil, 55.0 to 70.5 per cent in saline soil and 25.5 to 44.4 per cent in sodic soil. In saline soil availability of P might be higher for SSP and All-19 compared to ammonium/potassium phosphate fertilizers. On the other hand, MPP, MAP and All-19 may be preferably applied in sodic/acid soils alternative to SSP or DAP for realizing higher P release in soils from added fertilizers for the benefit of crop utilization. [ABSTRACT FROM AUTHOR]

The tea plant [Camellia sinensis (L.) O. Kuntz] is a well-known hyper-accumulator of aluminum (Al3+) that can grow in acidic soils contaminated with excess levels of Al3+. In this work, we used various assays for ascorbate–glutathione cycle components and other antioxidant enzymes to show that the alterations in the redox status after Al3+ treatment on tea cultivars, TV23 (tolerant) and S3A1 (sensitive), is responsible for their differential tolerance to Al3+ stress. A lower dose of Al3+ stress hastened the growth rate as suggested by an increase in biomass with respect to the control in both roots and leaves, but on further increasing the dose, the reverse occurred. Organic acid exudation has a major role in Al3+ detoxification. This study also reports the involvement of oxalate as a major exudate, since the activity of glycolate oxidase (GO) was found to drastically increase under the Al3+ stress condition. The increment in reactive oxygen species production and accumulation was quantitated in terms of malondialdehyde (MDA), super oxide anion (O2−), and hydrogen peroxide (H2O2), which was followed by a rapid increase in the activity of many stress-responsive antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX). The results indicated that differential tolerance to Al3+ toxicity in tea varieties is linked to their oxidative stress response; and, antioxidant enzymes, as a crucial constituent of the defense response, appear to function differentially in the two cultivars. This is the first report showing differential tolerance of two contrasting varieties of 'Assam Tea' to Al3+ stress. [ABSTRACT FROM AUTHOR]

Soil acidity is one of the main limitations for optimal use of land resources for better crop production. And, long-term fertilization experiments found to be helpful in increasing the nutrient supply in these acidic soils. Keeping this in view, a field experiment on rice was carried out by applying biofertilizers and enriched compost in an acidic Inceptisol of Assam over 10 successive years (2006–15) to examine its effects on nutrient availability and soil enzymatic activity. This experiment had five treatments viz. absolute control (T1), 100% recommended doses (RD) of inorganic NPK (T2), 50% RD of inorganic NP + 100% K +biofertilizers (T3), 50% RD of inorganic NP + 100% K +1 tonne enriched compost ha−1 (T4) and 25% RD of inorganic NP + 100% K +2 tonnes enriched compost ha−1 (T5) under randomized block design with four replications. After completing 10 years of experiment, it was observed that integrated use of enriched compost and biofertilizers with reduced doses of inorganic fertilizers enhanced the soil enzymatic activity as well as nutrient availability in rice grown in acidic clay loam soils of Assam. Application of biofertilizers and enriched compost had positive impact on plant accessible nitrogen, phosphorus and potassium in soil as compared to inorganic fertilizers. Also soil organic matter content increased considerably by these treatment. Integrated nutrient management practice in rice had also significantly enhanced the dehydrogenase, fluorescein diacetate and phospho-monoesterase activity in soil. [ABSTRACT FROM AUTHOR]

The quantities of slag obtained world wide are increasing, which can lead to the removal of agricultural lands from the agricultural use and even to their pollution with various heavy metals. In accordance to statistical data, over 400 million tonnes of iron and steel slag are produced every year. Over the past 20 years, the recovery rate of these by-products from the steel industry has increased significantly. Innovative technological developments and the cooperation with other industries have brought the steel industry closer to reaching its Zero Waste goal. The slag obtained from the steel industry is a mixture of silica, calcium oxide, magnesium oxide and aluminium and iron oxides. Due to the characteristics of these secondary materials, respectively due to the high content of calcium oxide, they can be used on agricultural lands in order to neutralize the soil acidity and implicitly, for a better valorization of nutrients by the crop plants. Currently, the forecast given for the evolution of soils, both internationally and in our country, shows a continuous tendency of degradation of agricultural soils, agriculture being both a factor of degradation and a victim of the degradation caused by other socioeconomic activities and also by agriculture itsel. In the last period, as a result of the application of agricultural technologies and due to the long-term fertilization with mineral Nitrogen fertilizers, a decrease in the soil's reaction has been recorded. The efficient use of these by-products of the steel industry as an amendment in agriculture in order to neutralize the soil's acidity, for improving crop productivity, for mitigating greenhouse gas emissions and for stabilizing heavy metals from contaminated soils, turns them into a value-added product in sustainable agriculture. This paper aims to present the influence of these materials resulted from the steel industry in improving the reaction of acidic soils, the influence they have on the main chemical properties of the soils and the influence on the production and quality of agricultural crops. [ABSTRACT FROM AUTHOR]

Aluminum ion (Al) is one of the most critical factors that inhibit plant growth in acid soils. Al triggers the rapid inhibition of root elongation at the root apex, although there are great differences in the susceptibility among plant species and cultivars. A number of highly Al-tolerant woody plants can withstand high Al concentrations that exceed the thresholds for most of annual plants. To understand high Al tolerance mechanisms in woody plants, we investigated long-term root elongation and Al accumulation in seedlings of Cinnamomum camphora, a broad-leaved multipurpose tree used in camphor production. Root elongation in C. camphora was only reduced to 70% of the control even at 500 micro M Al for a 60-day pulse exposure period. This Al stress level was tenfold higher when compared with the same Al condition that caused 70% of root elongation inhibition to an Al-resistant wheat cultivar for 48 h. Al accumulation pattern in each organ revealed that the discharge of accumulated Al from the root apex may be partly accounted for the rapid removal of Al in C. camphora. These results suggest that the maintenance of low Al accumulation in the root apex may be an important factor for the long-term Al-resistant root elongation of C. camphora.

Acacia mangium Willd. is a highly Al-resistant leguminous tree with modest organic anion exudation from roots. We have recently found the root apices of A. mangium to be surrounded by detached tissues with a unique structure under hydroponic conditions. To understand high Al tolerance mechanisms, we examined the roles of a cap-like structure on the Al-resistant root growth in A. mangium. The structures were autonomously sloughed off the root, and redeveloped within a week. Al only slightly inhibited the elongation of roots both with or without a cap-like structure. However, the removal of a root caplike structure facilitated Al-inducible root bending that only occurs immediately after the exposure. This facilitated root curving appears to be a major factor in slight enhancement in Al-induced root elongation inhibition in roots without a cap-like structure. The anchor position of a whole root cap-like structure to the root was limited to the columella cap region, where their connection became more rigid with longer Al-exposure periods. These results suggest that cap-like structures around the root may play a role in protecting root cap cells from the immediate impact of Al.

Observational trials at the UC Kearney Research and Extension Center indicate that new southern highbush blueberry cultivars, which require fewer “chill hours” to produce fruit, are well adapted to the San Joaquin Valley climate. In a replicated cultivar evaluation, we quantified yields and identified several productive and flavorful varieties. These initial trials and ongoing studies on irrigation, plant spacing, mulches and pruning will improve the likelihood of establishing this promising new crop in the semiarid valley. Because blueberries are acid-loving, the soil must be extensively treated before planting, at considerable expense. Growers considering planting or expanding blueberry acreage should develop sound business plans, accounting for lower future prices and improved growing, harvesting and packing efficiencies.

Kedelai (Glycine max) merupakan salah satu tanaman pangan yang dibudidayakan. Kebutuhan kedelai yang selalu meningkat setiap tahun mendorong usaha peningkatan terhadap produksi kedelai. Upaya peningkatan produksi dapat dilakukan dengan menggunakan pupuk hayati dan memanfaatkan lahan yang kurang produktif di Indonesia. Pupuk hayati yang digunakan mengandung isolat Bradyrhizobium japonicum sebagai penambat nitrogen dan Aeromonas salmonicida sebagai pelarut fosfat. Isolat yang terdapat dalam pupuk hayati diharapkan dapat membantu pertumbuhan kedelai di tanah asam dengan menyediakan unsur nitrogen dan fosfat. Penelitian ini bertujuan untuk mengetahui pengaruh pemberian pupuk hayati yang terdiri atas B. japonicum (BJ 11 wt) dan A. salmonicida pada penanaman kedelai di tanah asam. Tanaman percobaan dibuat dalam empat kelompok, yaitu dengan inokulasi Isolat BJ 11 (wt), PP, BJ 11 ditambah dengan PP, dan tanpa inokulasi (kontrol). Hasil penelitian menunjukkan bahwa aplikasi B. japonicum dan A. salmonicida cenderung dapat meningkatkan laju pertumbuhan tanaman, jumlah daun, dan bobot kering akar. Kata Kunci: Bradyrhizobium japonicum, Aeromonas salmonicid, Tanah Masam dan Kedelai Soybean (Glycine max) is one of cultivated food crops. Since the need of soybean is always increased every year, it needs some efforts to improve soybean production. One of the steps can be done is by using biofertilizer in a less productive land such as acid soil. Biofertilizer that used in this study consist of Bradyrhizobium japonicum as nitrogen fixation and Aeromonas salmonicida as phosphate solubilizer bacteria (PP). Isolates contained in the biological fertilizer is expected to help the growth of soybean in acid soils by providing elements of nitrogen and phosphate. The aim of this research was to know the effect of using biofertilizer consisted of B. japonicum (BJ 11 wt) and A. salmonicida (PP) to soybean growth in acid soils. The experiment was arranged with four group treatments that were inoculation with BJ 11 (wt), PP, BJ 11 plus PP, and without inoculation (as control). The results showed that the application of B. japonicum and A. salmonicida as inoculant mixture tend to increase plant growth, leaf number, and dry root weight. Keywords: Bradyrhizobium japonicum, Aeromonas salmonicid, Acid Soil and Soybean