“ No other single chemical soil characteristic is more important in determining the chemical environment of higher plants and soil microbes than the pH There are few reactions involving any component of the soil or of its biological inhabitants that are not sensitive to soil pH This sensitivity must be recognized in any soil-management system” “ Lime is truly a foundation for much of modern humid-region agriculture Knowing how pH is controlled, how it influences the supply and availability of essential plant nutrients as well as toxic elements, how it affects higher plants and human beings, and how it can be ameliorated is essential for the conservation and sustainable management of soils throughout the world” (Brady and Weil, 1999) Under areas where rainfall exceeds evapotranspiration, soil acidification is an ongoing natural process, which can either be accelerated by the activity of plants, animals and humans or can be impeded by careful management practices In areas affected by industrial activities, soil acidification is caused by acid drainage from pyrite oxidation and also from acid precipitation In areas that remain unaffected by industrial pollution, soil acidification in managed ecosystems is mainly caused by the release of protons (H + ) during the transformation and cycling of carbon (C), nitrogen (N) and sulfur (S) Just like in managed ecosystems, soil acidification in natural ecosystems caused by acid drainage and acid precipitation can have adverse impacts where soils have low pH buffering capacity Liming is the most common management practice aimed at neutralizing the acid produced, thereby overcoming the adverse impacts of soil acidification This review brings together fundamental aspects of soil acidification and recent developments on the implications of liming in relation to soil processes, particularly nutrient and heavy metal transformation and bioavailability in soils The article first outlines the various soil, plant and microbial processes that generate acid (protons; H + ions) both under natural and managed ecosystems It then discusses the effects of soil acidity on soil chemical and biological properties The effect of liming to overcome the problems associated with soil acidity is examined in relation to the transformation of nutrient ions and heavy metals The practical implications of liming to overcome heavy metal toxicity have been discussed in relation to the adsorption, leaching and phytoavailability of these metal ions Future research should aim to focus on the development of methods to quantify lime-enhanced (im)mobilization of nutrient ions and heavy metals in soils and to explore further the role of liming in remediating contaminated soils

Soil acidification and liming interactions with nutrientand heavy metal transformationand bioavailability

In areas that remain unaffected by industrial pollution soil acidification is mainly caused by the release of protons (H+) during the oxidation of carbon (C), sulphur (S) and nitrogen (N) compounds in soils. In this review the processes of H+ ions release during N cycling and its effect on soil acidification are examined. The major processes leading to acidification during N cycling in soils are: (i) the imbalance of cation over anion uptake in the rhizosphere of plants either actively fixing N2 gas or taking up NH 4 + ions as the major source of N, (ii) the net nitrification of N derived from fixation or from NH 4 + and R-NH2 based fertilizers, and (iii) the removal of plant and animal products containing N derived from the process described in (i) and losses of NO3-N by leaching when the N input form is N2,NH 4 + or R-NH2. The uptake of excess cations over anions by plants results in the acidification of the rhizosphere which is a “localized” effect and can be balanced by the release of hydroxyl (OH−) ions during subsequent plant decomposition. Nitrification of fixed N2 or NH 4 + and R-NH2 based fertilizers, and loss of N from the soil either by removal of products or by leaching of NO3-N with a companion basic cation, lead to ‘permanent’ acidification.

Processes of soil acidification during nitrogen cycling with emphasis on legume based pastures

The dynamics and transformations of micronutrients (Zn, Cu, Fe, Mn, B and Mo) in soils, are governed by various factors like pH, EC, soil organic matter etc. Soil organic matter (SOM) is known to modify different physiochemical reactions that influence the available component of micronutrients. Soil organic matter favors reduced (lower redox potential) environment and enhances the accessibility of micronutrient cations in the soil. Also, SOM has direct and indirect impacts on nutrient transformations. Soil organic matter (SOM) also serves as source of soil organic carbon (SOC) comprising about 60% on a mass basis. Under reduced environment the addition of SOM increased complexed forms of micronutrients. Build-up of SOM in soil converts adsorbed fractions to more plant-accessible forms of micronutrients. Soil organic matter addition increases the water soluble and exchangeable forms of micronutrients in soil which further increase the uptake of micronutrients. High amount of SOM in soils assists the various reactions of micronutrients resulting in formation of more stable complexes of micronutrient. Soil organic matter binds more Zn, Cu, B and Mo compared to Fe and Mn because the former are less sensitive to redox changes. The accretion of organic matter near the soil surface increases transformations (towards adsorbed fractions) of Mn and Fe and possibly decreases the availability of Zn, Cu, B and Mo by causing their redistribution among other complex fractions.

Dynamics and transformations of micronutrients in agricultural soils as influenced by organic matter build-up: A review

Role of plant cation/anion uptake ratio in soil acidification

Under areas where rainfall exceeds evapotranspiration, soil acidification is an ongoing process that can be either accelerated by the activity of plants, animals, and
humans or slowed down by careful management practices [1,2]. In areas that remain unaffected by industrial pollution, soil acidification is mainly caused by the
release of protons (H) during the transformation and cycling of carbon (C), nitrogen (N), and sulfur (S) in the soil-plant-animal system [3,4]. Under managed
systems much of the accelerated soil acidification is caused by increasing N and
S inputs into the farming system (Table 1). For example, in areas of Australia
where legumes have been grown continuously for more than 30 years, the soil pH
has decreased by about one unit [5-10]. Similarly, in New Zealand, intensively
managed legume-based dairy pastures require applications of approximately 2.5
tons of lime per ha every 6 years [11,12] to neutralize acidity mostly generated
through loss of N from an accelerated N cycle.

Role of carbon, nitrogen, and sulfur cycles in soil acidification.

Red clover (Trifolium prateuse L.), sweet clover (Meliotus alba Medik.). alfalfa (Medicago sativa L.), and crown vetch (Vica villosa Roth) were grown in nitrogen-free Hoagland's solution in a declining nutrient condition. Increases in acidity of the nutrient solutions were recorded over the experimental period. In general, the excess bases and the excess bases/nitrogen ratio varied considerably among harvests. Significant positive relationships between total N and proton efflux excess bases and H+ excretion, and dry weight and H+ efflux were observed (...)

Acidity Produced by Leguminous Plants through Symbiotic Dinitrogen Fixation

In vitro propagation of olive (Olea euorpea L.) always remained a challenging task due to its woody nature and oxidation of culture. The current study intended to optimize shoot induction and proliferation protocol for different cultivars (“Leccino”, “Gemlik”, “Moraiolo” and “Arbosana”) of olive-on-olive media (OM) provided with different concentrations (0, 0.5, 1.5, and 2.5 mgL−1) of 6-benzylaminopurine (BAP) by pre-exposing their explants (nodal segments) with different regimes (0, 24, and 48 h) of cooling. The impacts of treatments were evaluated on morphological (shoot induction percentage, primary shoot length, number of leaves shoot−1, and number of shoots per explant−1), physiological (total chlorophyll, carotenoids, CO2 assimilation, and proline), biochemical (primary and secondary metabolites) attributes of cultivars after 50 to 60 days of culture. Data recorded were subjected to statistical analysis. All traits depicted significant increases in all genotypes with increasing pre-cooling treatments and increasing supplementations of 6-benzylaminopurine (BAP). This increase was the highest for the interaction of 48 h pre-cooling and 2.5 mgL−1 BAP concentration. Moreover, correlation analysis of all traits revealed significant paired association among them in a positive direction, while principal component analysis (PCA) revealed the extent of association varied with types of treatments and the nature of genotypes. Among cultivars, Arbosana depicted more dramatic changes in morphological traits, physiological attributes, and biochemical contents due to varying interactions of pre-cooling and BAP treatments as compared to Moraiolo, Gemlik, and Leccino with in vitro systems.

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In Vitro Evaluation of the Effects of BAP Concentration and Pre-Cooling Treatments on Morphological, Physiological, and Biochemical Traits of Different Olive (Olea euorpea L.) Cultivars

Establishment of a Tridimensional Teaching Mode for Organic Chemistry Course in Agricultural Universities: A Case Study of Jilin Agricultural University

Wen-Cheh Liu

Papers

Acidity Produced by Leguminous Plants through Symbiotic Dinitrogen Fixation

In Vitro Evaluation of the Effects of BAP Concentration and Pre-Cooling Treatments on Morphological, Physiological, and Biochemical Traits of Different Olive (Olea euorpea L.) Cultivars

Establishment of a Tridimensional Teaching Mode for Organic Chemistry Course in Agricultural Universities: A Case Study of Jilin Agricultural University