Influence of organic and inorganic soil amendments on corn root growth and soil chemical properties

One of the main constraints to corn production on a highly weathered acid soil is aluminum (Al) toxicity. High Al concentration in acid soils restricts root growth by inhibiting cell elongation and cell division. The objective of this study was to determine the effects of inorganic arid organic soil amendments on corn root growth and soil chemical properties A laboratory experiment was conducted using Bungor series soil (Typic Paleudult) surface sampled (0 - 20 cm) from Puchong farm. Aliquot of the soil (600 g) was treated with legume residues (1% w/w), chicken manure (1% w/w), GML (4 t had), gypsum (4 t ha-1) and control The treated soils were moistened at field capacity (0 25 kg H20 kg-1 soil) and allowed to react for 7 days. Corn seeds (Zea mays L.) were sown and after 5 days root length was measured The results showed that soils amended with GML or chicken manure gave relatively high root length compared to other treatments. The GML and chicken manure treatments increased soil pH and decreased both the soil exchangeable Al and Al-saturation Chicken manure had an additional ameliorative effect over lime in that it increased soil exchangeable Ca, Mg and K

An evaluation of cation exchange capacity methods for acid tropical soils

The cation exchange capacity (GEC) of soil is an important criteria for assessing soil fertility beside its use in soil classification. Seven methods, namely, (1) BaCl2 - triethanolamine of BaCl2 - TEA (PH 8.2), (2) NH40Ac (PH 7.0) - leaching, (3) NH40Ac (PH 7.0) - shaking, (4) compulsive exchange method of Gillman (1979) (GECcd, (5) modified compulsive exchange method of Gillman (1986) (CEC3, (6) Summation of Ca from method 5 with 1 M NH4 NO3 exchangeable Al (CECtotal and (7) summation of NH40Ac (PH 7.0) exchangeable bases with 1 M KCl exchangeable Al (CECsum) were used to determine and compare the CEC values of five acid tropical soils. All methods gave different CEC values which followed the order BaCl2 - TEA> NH40Ac shaking = NH40Ac leaching> CECsum = CECto tal > CECCE = CECB• Methods with pH conditions close to field situations gave much lower CEC values than the buffered methods. The buffered methods generate charge on the variable-charge colloids, thus resulting in inflated CEC values, while the unbuffered methods do not. There is a high correlation between BaCl2 - TEA and NH40Ac (PH 7. 0) leaching method; CECCE and CECsum; and, CECB and CECtotal Amongst the methods evaluated, the NH40Ac (PH 7.0) leaching is recommended in routine soil analyses for classification purposes while CECsum is recommended for agronomic evaluation

Increasing the organic matter content of an Oxisol using rice husk compost : changes in decomposition and its chemistry.

About 116 million Mg of rice husk, a byproduct of rice milling, are produced worldwide annually. Rice husk could be used as a soil amendment, but little attention has been given to the effect of its application and dynamic properties in soils. A study was, therefore, conducted to determine: (i) the effect of rice husk compost applications on soil organic C content; and (ii) the changes in organic C functional groups with time and under different environments using solid-state cross polarization magic angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectroscopy. Experiments were performed under different environments (laboratory, greenhouse, and field) for 15 to 24 mo, using an Oxisol treated with various rates of rice husk compost (RHC) and the soils were periodically sampled and analyzed. Results showed that RHC significantly increased the organic C of the Oxisol and changes in its chemistry occurred after 24 mo ( laboratory) and 12 mo (greenhouse and field). Solid-state CP/MAS 13C NMR showed C types derived from RHC were dominated by cellulose, with specific characteristics of well-ordered structure (very sharp and well-resolved peaks at O-alkyl and di-O-alkyl C regions), thereby signifying stabilized organic C. The RHC decomposition was faster in the order field > greenhouse > laboratory conditions as revealed by the high values of decomposition indices (hydrophobicity/hydrophilicity ratio, alkyl/O-alkyl C ratio, and aromaticity) and the high magnitude of normalized cumulative C loss for conditions with a high decomposition rate. The cumulative C loss was 71 to 80% (depending on the application rates) in the field, 71 to 74% in the greenhouse, and 48 to 62% in the laboratory after 12 mo. Under all conditions, the remaining RHC-derived C was still significantly higher than the control treatment at the end of the experiments, implying that RHC can be used to increase organic matter in soils

Changes in properties of composting rice husk and their effects on soils and cocoa growth

The worldwide production of rice husk, a by‐product and agrowaste that causes serious environmental problems, may reach 116 million t y−1. The objectives of this study were (i) to determine the physicochemical changes of rice husk and its structural chemistry during composting using 13carbon nuclear magnetic resonance (13C NMR) and (ii) to determine the effect of the composted rice husk (CRH) on the properties of Oxisol and cocoa (Theobroma cacao L.) growth under glasshouse conditions. Results showed an active composting phase occurred at the first 53 days as revealed by high carbon dioxide (CO2)‐C (40–71 µg g−1 h−1) production, followed by a matured composting phase occurring at 54–116 days as revealed by decreasing in CO2‐C production (10 µg g−1 h−1). The active composting was accompanied by increases in electrical conductivity (EC), pH, ammonium (NH4 +), and nitrate (NO3), whereas during the matured composting phase, the EC and cation exchange capacity increased but pH, NH4 +, and NO3 −1 decreased. The ash of the produced compost contains mainly calcium (Ca), potassium (K), sulfur (S), magnesium (Mg), and phosphorus (P) as essential nutrients. The CP/MAS 13C NMR spectra before and after various composting times indicated the dominance of sharp and well‐resolved signal peaks at O‐alkyl C and di‐O‐alkyl C regions (67–73%), which are characteristic of cellulose. The percentage of N‐alky/methoxyl was 23–26% whereas phenolic, carboxyl, and alkyl C types were less than 3% each. The application of the CRH to an Oxisol significantly increased soil pH and Ca, Mg, K, sodium (Na), and silicon (Si) ions of in situ soil solution but decreased the amounts of toxic ions [aluminum (Al), manganese (Mn), and iron (Fe)]. The CRH was found to increase cocoa growth up to 37%

Pore space and specific surface area of heavy clay Oxisols as affected by their mineralogy and organic matter

Pores and specific surface area (SSA) play a major role in controlling transport systems and potential reactivity of soils, but they have received little attention for heavy clay Oxisols. The objectives of this study were: (i) to study the pore sizes and SSA of heavy clay Oxisols as affected by their mineralogy and soil organic matter (SOM); and (ii) to determine the mechanism of SOM stabilization in a dark-colored Oxisol (Kuantan soil). The mineralogy of the clay fraction was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy, whereas soil organic C was determined by combustion technique. Pores and SSA were measured by N2 adsorption-desorption technique. Results showed that the clay fraction of the three Oxisols studied varied from 73% to 82%. The minerals in this soil fraction were kaolinite, goethite, hematite, and gibbsite in varying amounts. Under natural conditions (SOM was not removed by hydrogen peroxide), the pores were dominated by mesopores (2-50 nm). Partitioning the mesopores into various sizes showed that the cumulative small mesopore (2-20 nm) volume was considerably higher for Kuantan (63%-73%) than the S. Mas or Segamat (25%-35%) soils. This is caused by the lower crystallinity and smaller size of minerals in the former. The values of SSA were compatible with those of the soil pores as exhibited by the SSA with and without SOM, which were 1.6 to 1.9 and 2.0 to 2.2 times higher, respectively, in Kuantan than in S. Mas or Segamat soils. Stabilization of SOM in Kuantan soil occurred through physical protection in the mesopores and cation bridging, as revealed by the increase in mesopore volume (from 58% to 92%) after SOM removal and the high Fep and Alp contents, respectively. The less crystalline and smaller clay size particles present in the heavy clay Oxisols have a positive impact on soil carbon sequestration and stabilization

Mineralogy and factors controlling charge development of three Oxisols developed from different parent materials.

Three Oxisols, developed from serpentinite (Sungai Mas Series), basalt (Kuantan Series) and andesite (Segamat Series), selected to represent the most common Oxisols in Malaysia were sampled and studied. The objectives of this study were: (i) to determine mineralogical composition and factors responsible for changes in point of zero charge (pH0) of the variable charge component of three Oxisols; (ii) to use pH0 values to assess degree of chemical weathering; and (iii) to determine the magnitude of variable charge using corrected back-titration technique. The mineralogical composition was determined by X-ray diffraction analysis (XRD). The pH0 was determined by potentiometric titration in different electrolyte strengths. The magnitude of variable charge generation as a function of soil pH was measured using corrected back-titration to allow elimination of charge overestimation caused by solid dissolution and hydrolysis reactions. The results showed that the mineralogical composition were similar (kaolinite, goethite, hematite and gibbsite) between profiles but different in proportion, except for gibbsite which was absent in the andesite-derived soil. The sequential removal of soil organic matter (SOM), iron oxides and SOM together with iron oxides resulted in the changes of pH0 from 3.9–5.7 to 5.3–6.7, 2.6–3.7 and 3.3–4.5, respectively. These pH0 changes indicate SOM and sesquioxides are masking mineral surfaces and are factors responsible for lowering and increasing pH0 values, respectively. Regression correlation (R2 = 0.87⁎⁎) showed that for every 1% organic C may decrease 1.0 unit of pH0 value. The pH0 values, after SOM removal, are in the order of Sungai Mas ∼ Segamat > Kuantan Series. This suggests that the serpentinite and andesite-derived soils have achieved a relatively similar degree of chemical weathering and they are more weathered than the basalt-derived soil. The charge measured by corrected back-titration is 1.5–3.8 cmolc kg− 1 at pH 4.5 and increases to 4.2–10.8 cmolc kg− 1 at pH 6.5, indicating that the three Oxisols mainly bear variable charge. Charge overestimation resulted from dissolution and hydrolysis reactions during potentiometric titration ranges from 36 to 160%, depending on pH values (the lower the pH the higher is the overestimation). Hence, back-titration is a reliable technique to correct charge overestimation when using the traditional potentiometric titration for highly weathered tropical soils

Dissolution of ground basalt and its effect on oxisol chemical properties and cocoa growth

Obtaining suitable and environmentally sound materials for restoring properties of highly weathered soils (e.g., Oxisols) presents a great challenge. A study was carried out to: (i) determine the ability of ground basalt to increase the negative charge of an Oxisol, increase plant nutrients (Ca, Mg, K, and Na), and suppress Al toxicity; and (ii) assess the effects of basalt application on cocoa growth. Pots containing 20 kg pot of Oxisol were treated with various rates of finely ground basalt (<250 μm) and planted with cocoa (Theobroma cacao L.) in a greenhouse for 15 months. The soils and in situ soil solutions were sampled and analyzed periodically. The ground basalt continuously increased soil pH with increasing application rates. The cation exchange capacity occupied by base cations increased with increasing ΔpH value (soil pH - pH0), confirming that the type of charge generation depends mainly on variable charge. The cation exchange capacity occupied by base cations value for different basalt rates at any given similar equilibrium pH value always increased with increasing basalt rates, suggesting that every increment of basalt rates generated "new negative sites" to retain cations in the soil. Basalt application continuously released base cations, as revealed by the significant increases in Ca, Mg, K, and Na both in the forms of exchangeable cations and soluble cations (in situ solution), with concomitant suppression of toxic elements (Al and Mn). Basalt application significantly improved cocoa growth, suggesting that basalt is a promising material to be used for restoring the chemical properties of highly weathered tropical soils

Analysis of heavy metals during composting of the tannery sludge using physicochemical and spectroscopic techniques

The major limitation of direct application of tannery sludge compost in agriculture is the total heavy metal contents and their bioavailability to the soil–plant system. This study focused on the heavy metal characterization and the influence of changing the physicochemical properties of the medium throughout the composting on the concentrations, bioavailability or chemical forms of Cr, Cu, Zn, Pb and Cd in tannery sludge. The study shows that throughout the 60 days of composting, physicochemical analysis and Fourier-transformed infrared (FTIR) spectroscopic characterization show that all parameters elaborated and reached relatively stable levels reflecting the stability and maturity of the final product, and revealed the biodegradation of components that can be easily assimilated by microorganism. The C/N ratio reaches the optimal range of stable compost; inorganic nitrogen is transformed into stable organic forms. The total concentration of Cr, Zn, Cu, Pb and Cd is very low rendering final compost acceptable for agricultural use. The germination index for both Chinese cabbage and lettuce was 97% after 60 days of composting, showing that the final compost was not phytotoxic. Furthermore, in using a sequential extraction method in sludge compost at different phases of treatment, a less than 2% of metals bound to bioavailable fractions X–(KNO3 + H2O). A large proportion of the heavy metals were associated to the residual fraction (75–85%) and more resistant fractions to extraction X–NaOH, X–EDTA, X–HNO3 (15–25%). Mobile fractions of metals are poorly predictable from the total content. Bioavailability of all fractions of elements tends to decrease