The interactive effects of biochar and cow manure on rice growth and selected properties of salt-affected soil

Salt-affected soil induces detrimental influences on paddy rice (Oryza sativa L.) growth and ameliorating the influences could be done with organic amendments, such as animal manure and biochar. The aims of the current study are: (1) to examine the interactive effects of biochar and cow manure on rice growth and on selected properties of salt-affected soil, and (2) to identify potential mechanisms related to the amendments. Saline-sodic soil was used for a net house experiment with two experimental factors: biochar (no-biochar, rice-husk, and -straw biochar) and cow manure (with and without cow manure). Without the manure, addition of both rice-hush and – straw biochar significantly increased rice growth, whereas a combination of individual biochar with manure did not show a positive synergistic effect. The interactive effect of two factors was not significant on available P and exchangeable K concentrations, but the main effects of the two factors were significant. Biochar addition resulted in higher soil cation exchange capacity (CEC) (28.8 to 29.0 cmol_c kg^?1) than the control (25.6 cmol_c kg^?1), but manure addition did not. Improved nutrient availabilities such as P and K, as well as CEC are among the potential mechanisms accounting for the enhanced rice growth with biochar.     

Statistical and geostatistical techniques for geospatial modeling of soil cation exchange capacity

Soil cation exchange capacity (CEC) is a main criterion of soil quality and pollutant sequestration capacity. This research was carried out to evaluate cokriging prediction map of soil CEC spatial variability with the principal components derived from soil physical and chemical properties. Two hundred and forty-seven soil samples were collected that 75% of them were used for training soil CEC and 25% for testing of prediction. The first principal component (PC1) was highly correlated with soil CEC (r = 0.81, P < 0.01), whiles there was no significant correlation between CEC and PC2 (r = -0.19). Then, the PC1 was used as an auxiliary variable for the prediction of soil CEC in cokriging method. The determination coefficient (R²) of cross-validation for the test dataset was 0.47 for kriging and 0.71 for cokriging. Therefore, according to the results, principal components that have the highest positive and significant correlation with the dependent variable have the most potential for cokriging prediction.     

镧的累积对红壤阳离子交换量及土壤溶液组成的影响

Pot and adsorption-exchange experiments were carried out by collecting the soil samples from the surface layer(0-15cm) of red soil at the Ecological Experiment Station of Red Soil,the Chinese Academy of Sciences,in Jiangxi Province of CHina.When concentration of the exogenous La^3 exceeded 400mg kg^-1,there was less non-exchangeable La^3 than exchangeable La^3 in the soil.Cation exchagne capacity of the soil changed slightly with increasing concentration of the exogenous La^3 in both experiments.However,in the adsorption-exchange experiment,when concentration of the exogenous La^3 was higher than 300mg kg^-1,exchangeable basic cations decreased significantly,while exchangeable hydrogen and exchangeable aluminum increased significantly compared with the control treatments.The amounts of base cations(Ca^2 ,Mg^2 ,k^ and Na^ )exchanged by La^3 in the supernatant solution increased with the concentration of the exogenous La^3 ,especially when concentration of the exogenous La^3 was higher than 50mg kg^-1.     

不同调理剂对猪粪堆肥腐殖质特性及元素含量变化的影响

分别以木屑、泥炭及水葫芦作为猪粪堆肥的调理剂，制作有机堆肥，研究了3种堆肥体系在堆肥进程中腐殖酸（HA＋FA）及其组成、腐殖化指数（HI=HA／FA）、pH的变化过程，以及堆制前后1mol／L NH4Ac-0．05mol／L EDTA浸提态金属离子含量的变化。在此基础上讨论了HI、pH和阳离子交换量（CEC）之间的关系。结果表明，在整个堆肥制作中，HA＋FA和HA均呈现先下降后上升再稳中有降的趋现势，总体表现为增加；HI则上升明显，这些是堆肥腐熟和品质提高的重要表；pH变化因调理剂的不同而有较大的差异；除重金属Cr外，1mol／L NH4Ac-0．05mol／L EDTA浸提的绝大部分金属离子含量堆制后均有增加，3种堆肥增加幅度的顺序为：猪粪＋水葫芦〉猪粪＋木屑〉猪粪＋泥炭；堆制前后pH和HI的变化与堆制前后CEC变化分别呈较好的正相关和负相关，它们可以作为堆制前后交换态金属元素含量变化的指示指标。     

Spatial Variability of Soil Cation Exchange Capacity in Hilly Tea Plantation Soils Under Different Sampling Scales

Studies on the spatial variability of the soil cation exchange capacity （CEC） were made to provide a theoretical basis for an ecological tea plantation and management of soil fertilizer in the tea plantation. Geostatistics were used to analyze the spatial variability of soil CEC in the tea plantation site on Mengding Mountain in Sichuan Province of China on two sampling scales. It was found that, （1） on the small scale, the soil CEC was intensively spatially correlative, the rate of nugget to sill was 18.84% and the spatially dependent range was 1 818 m, and structural factors were the main factors that affected the spatial variability of the soil CEC; （2） on the microscale, the soil CEC was also consumingly spatially dependent, and the rate of nugget to sill was 16.52%, the spatially dependent range was 311 m, and the main factors affecting the spatial variability were just the same as mentioned earlier. On the small scale, soil CEC had a stronger anisotropic structure on the slope aspect, and a weaker one on the lateral side. According to the ordinary Kriging method, the equivalence of soil CEC distributed along the lateral aspect of the slope from northeast to southwest, and the soil CEC reduced as the elevation went down. On the microscale, the anisotropic structure was different from that measured on the small scale. It had a stronger anisotropic structure on the aspect that was near the aspect of the slope, and a weaker one near the lateral aspect of the slope. The soil CEC distributed along the lateral aspect of the slope and some distributed in the form of plots. From the top to the bottom of the slope, the soil CEC increased initially, and then reduced, and finally increased.     

The fate of ammonium nitrogen applied to flooded rice as affected by zeolite addition

High rice (Oryza sativa L.) yields are closely related to plant absorption of a large amount of nitrogen (N). However, there is little information on the fate of N applied at the middle growth stages of rice. Labeled ¹⁵N ammonium sulfate was applied at the panicle formation stage in Experiment I, and 10 d after heading in Experiment II. Zeolite was also added at the concentration of 0, 0.01, and 0.1 kg kg^-1 to increase the cation exchange capacity (CEC) of the soil. The amount of ¹⁵N fertilizer in the soil surface water decreased exponentially and the fertilizer disappeared within 2 d after application. The soil that received zeolite at 0.1 kg kg^-1 exhibited significantly less ¹⁵NH₄ ⁺-N in the surface water and in the soil solution than the soil without the zeolite amendment. A significantly larger amount of exchangeable ¹⁵NH₄ ⁺-N was observed in the high zeolite-treatment of soil compared to the low zeolite-treatment of soil. The amount of exchangeable ¹⁵NH₄ ⁺-N increased initially, and thereafter decreased to traces 4 d after application in Experiment I, while 6 or 9 d after application in Experiment II. The disappearance of exchangeable ¹⁵NH₄ ⁺-N could be attributed mainly to the uptake by plants. The zeolite amendment or the time of N application did not significantly affect the amount of immobilized N. The rate of N adsorption was inhibited with increasing zeolite application. Moreover, zeolite application did not increase the recovery percentage of ammonium sulfate by rice plants. The total recovery of applied N ranged from 65 to 75%, irrespective of the zeolite treatments or the time of N application.     

pH effects of the addition of three biochars to acidic Indonesian mineral soils

Abstract

Soil acidity may severely reduce crop production. Biochar (BC) may increase soil pH and cation exchange capacity (CEC) but reported effects differ substantially. In a systematic approach, using a standardized protocol on a uniquely large number set of 31 acidic soils, we quantified the effect of increasing amounts (0–30%; weight:weight) of three types of field-produced BCs (from cacao (Theobroma cacao. L.) shell, oil palm (Elaeis guineensis. Jacq.) shell and rice (Oryza sativa. L.) husk) on soil pH and CEC. Soils were sampled from croplands at Java, Sumatra and Kalimantan, Indonesia. All BCs caused a significant increase in mean soil pH with a stronger response and a greater maximum increase for the cacao shell BC addition, due to a greater acid neutralizing capacity (ANC) and larger amounts of extractable base cations. At 1% BC addition, corresponding to about 30 tons ha^?1, the estimated increase in soil pH from the initial mean pH of 4.7 was about 0.5 units for the cacao shell BC, whereas this was only 0.05 and 0.04 units for the oil palm shell and rice husk BC, respectively. Besides depending on BC type, the increase in soil pH upon the addition of each of the three BCs was mainly dependent on soil CEC (low CEC resulting in stronger pH increase), and to a lesser extent on initial soil pH (higher initial pH resulting in stronger pH increase). Addition of BC also increased the amount of exchangeable base cations (cacao shell ? oil palm and rice husk) and CEC. Through this systematic screening of the effect of BC on pH and CEC of acidic soils, we show that a small addition of BC, in particular if made of cacao shell, to acidic agricultural soils increases soil pH and CEC. However, the response is highly dependent on the type, quality and amount of the added BC as well as on intrinsic soil properties, mainly CEC.     

Measurement of Cation Exchange Capacity of Organic‐Matter Fractions from Soils using a Modified Compulsive Exchange Method

Abstract

This article describes a modified compulsive exchange method suitable for the determination of cation exchange capacity (CEC) over a pH range on solid, separated organic‐matter fractions. The method is demonstrated to be a reproducible and relatively simple means of measuring CEC on fractions separated by physical means in conjunction with hydrofluoric acid (HF) treatment. By including a modification for measuring the residual magnesium (Mg²⁺) content by dilution and conductivity, the method is simplified to measure CEC versus pH using a single sample; the only laboratory instruments required are pH and conductivity meters and a balance. The lack of agreement between this method and the silver thiourea (AgTU) method for some fractions at low pH is attributed to the uncontrolled variation in solution ionic strength when acid is introduced to effect solution pH changes in the AgTU method.     

Effect of ionic strength on the cation exchange capacity of some forest soils

Abstract

Cation exchange capacity (CEC) of the 0–5 cm depth of forest soils increased with the square root of solution ionic strength over the experimental range of 6 to 96 mM. Percentage increases in CEC were positively correlated with percentage organic carbon; for mixed hardwood forest soils, increases were 38% for soils with 3.3% carbon, and 105% for soils with 7.4% carbon when ionic strength was varied over the full experimental range. When analyzing soils with constant‐potential surfaces, both pH and ionic strength must be controlled, preferably at or near levels found in the field, in order to provide interpretable measures of CEC.     

A comparison of methods used for determination of cation exchange capacity

Abstract

Cation exchange capacity of ten non‐calcareous and non‐saline soils from Queensland, Australia, has been determined by the ammonium acetate method using different procedures, by an ammonium chloride method at pH8.5, and by three methods which attempt to approximate field conditions. Procedural differences in the ammonium acetate method produced variation in results, and methods using approximate field conditions gave much lower values for those soils considered to have variable charge properties.