茶树叶和刺槐叶对茶园土壤酸度的改良效果

通过培养实验,比较研究了茶树老叶和刺槐叶对2种酸化茶园土壤的改良效果.结果表明,在酸性茶园土壤中分别加入5、10和20g·kg-1茶树老叶和刺槐叶培养35 d后,相对于对照,土壤pH值有不同程度的提高,土壤交换性酸减小,土壤交换性钙和镁等交换性盐基离子数量有所提高,土壤毒性铝离子的数量减少.2种树叶对土壤酸度的改良效果随其加入量的增加而增加,刺槐叶的改良效果好于茶树老叶,2种树叶对红壤的改良效果优于其对黄棕壤的改良效果.植物物料所含的灰化碱及豆科植物所含大量有机氮的矿化是导致土壤酸度下降的主要原因.     

Changes in soil chemistry associated with the establishment of forest gardens on eroded,acidified grassland soils in Sri Lanka

Topsoil properties were determined in forest gardens established about 20 years ago on eroded grassland soils (abandoned tea lands) in the wet zone of the Sri Lankan highlands. They were compared with adjacent, eroded grasslands (abandoned tea lands) on strongly weathered soils vs soils at earlier stages of pedogenic development in a two-way analysis of variance. Soil pH in forest gardens was, on average, 6.1, nearly one unit higher than in the adjacent grasslands. In the garden soils, the cation exchange capacity (CEC measured at pH 4.8) was nearly double, exchangeable calcium concentrations five times and exchangeable magnesium three times as high as in the grasslands soils. Total soil N content was found to be nearly 40% higher in the gardens. Topsoil gravel contents in the gardens were less than half as high as in the grasslands. The increases in exchangeable bases and N in gardens, relative to grasslands, were attributed to increased nutrient retention and acquisition. Higher retention was partly due to the higher CEC_pH4.8, and probably to reduced erosion and increased, continuous fine root density in the garden topsoils. Higher field CEC in gardens was likely to result from generally higher C contents and from the reversal of acidification, presumably caused by base accumulation and decomposition processes. Our results suggest that forest garden establishment on degraded grasslands can lead to accumulation of mobile nutrients in the topsoil, probably due to increased nutrient retention, subsoil uptake and litter input exceeding nutrient uptake by the standing biomass.     

Effect of soil acidity on the entomophilic nematode Steinernema kraussei Steiner

Summary The free-living stages of Steinernema kraussei (Rhabditida), an endoparasite of Cephalcia abietis L. (Hymenoptera), are exposed to different soil conditions when searching for host nymphs. Field studies and laboratory experiments showed that soil acidity plays a major role in the nematode's ability to parasitize Cephalcia nymphs. Under field conditions in Picea abies forests positive correlations between soil pH and both nematode density and insects parasitized were found. Acidic soil with pH levels below 4.0 may limit the nematode's host-finding. Controlled experiments in the laboratory under different pH conditions confirmed these correlations.Dedicated to the late Prof. Dr. W. Kühnelt     

Population densities of clover rhizobia in Texas pastures and response to liming

Summary Clovers are widely used forage legumes on acidic soils in Texas and need inoculation with appropriate rhizobia when first introduced. Acidic soils are not conducive to survival of clover rhizobia. A survey of pastures was undertaken to determine the number of rhizobia present. The effect of liming acidic soils on the survival of clover rhizobia was also evaluated in the laboratory. The number of clover rhizobia was more than 100 cells g^-1 soil in 70% of the pastures surveyed but populations within pastures varied by more than two orders of magnitude. The number of years of clover production beyond 1 year did not affect the rhizobial population density. The soil pH of twelve samples was below 5.0 and six samples had populations of rhizobial lower than 100 g^-1 soil. Eleven out of sixteen samples from fields that had grown clover and had pH values above 6.0 had populations exceeding 1000 g^-1 soil and only three samples had populations lower than 100 g^-1 soil. Incubating indigenous or inoculated rhizobia in well-mixed soils having pH values of 5.1 or below resulted in populations declining to below 10 g^-1 soil in 6 weeks. Mixing of soils with pH values of up to 5.4 induced reduction of rhizobial numbers, possibly by destroying microsites. Liming of soils to increase pH values above 5.5 improved survival of native or inoculated rhizobia in most cases.     

土壤有机质对交换性酸测定结果的影响

为探讨土壤有机质对两种常用的土壤交换性酸测定方法(BaCl_2-TEA提取法和KCl淋溶法)结果的影响,选取了85个不同有机质质量分数的酸性土壤并采用BaCl_2-TEA提取法和KCl淋溶法测定其交换性酸含量.结果表明,BaCl_2-TEA提取法测得的土壤交换性酸含量远大于KCl淋溶法的测定结果.KCl淋溶法测得的土壤交换性酸含量与土壤pH值间的负相关性极有统计学意义(r=-0.79**),而BaCl_2-TEA提取法测得的土壤交换性酸含量与土壤pH值间的相关性无统计学意义(r=-0.08).但BaCl_2-TEA提取法测得的土壤交换性酸含量却与土壤有机质质量分数间的正相关性极有统计学意义(r=0.94**).此外,由KCl淋溶法测得的土壤交换性酸进一步计算得到的盐基饱和度与土壤pH值间的相关性(r=0.69**)也大于BaCl_2-TEA提取法(r=0.25*).通常土壤酸化越严重,土壤pH值越低,交换性酸含量越高,盐基饱和度越低.可以得出,土壤有机质会使BaCl_2-TEA提取法的测定结果产生较大的正误差,而对KCl淋溶法的影响较小.由于土壤有机质中的腐殖酸会与BaCl_2-TEA提取法中的有机弱碱TEA发生反应,增加TEA用量,从而使计算得到的土壤交换性酸的结果偏高.因此,对于高有机质质量分数的酸性土壤,不宜采用BaCl_2-TEA提取法测定其交换性酸含量.但在KCl淋溶法中,由于K~+对Al~(3+)的交换能力较弱,使得该方法测得的土壤交换性酸含量偏低.因此,可乘以1.5左右的校正系数,以便能真实地反映出土壤交换性酸含量.     

Evaluation of relationship between dispersibility of soils and charge characteristics using a modified ion adsorption method; An example of soils from Wakayama Prefecture,Japan

The relationship between the charge characteristics and the dispersibility of soils from reclaimed land (highly dispersive) and adjacent forest area (physically stable) was investigated.

To evaluate the amount of soil charges quantitatively, the measurement based on cation and anion adsorption (ion adsorption method) was attempted in two ways, where special attention was paid to the solution concentration. In the conventional ion adsorption method, the treatments with concentrated solutions (1 mol L^-1) were included in the process. In the modified method, soils were treated with dilute solutions (5 mmol L^-1), in taking account of the soil solution concentration in humid temperate regions. The amount of charges derived from the modified method was smaller than that from the conventional one, especially in the high pH zone. In a preliminary experiment, the extraction of polyvalent cations from soils was found to be significantly affected by the salt concentration. Thus, the use of solutions with an excessively high concentration was considered to result in an error in the estimation of the active charges in soils which would contribute to the dispersion behavior in the field.

The applicability of the modified method for analyzing the dispersion behavior of soils was evaluated by relating the dispersibility of silts and clays at different pHs with the charge characteristics determined under the same ionic strength. The dispersion ratio of silts of the reclaimed land reached maximum values at pH 5.5, above which the ratio decreased, whereas the ratio of clays began to increase in the pH range above 6. The dispersion ratio of silts of the forest area increased in the pH range above 6, whereas that of clays remained constant at a low level in all the pH ranges below 7. The changes in the dispersibility of silt plus clay fractions corresponded to total charge characteristics determined by the modified method. Thus, the evaluation of soil charges by the modified ion adsorption method was considered to be effective to predict soil dispersibility under field conditions, indicating that it could replace electrokinetic analyses such as electrophoresis in studies on the dispersion/flocculation behavior of soils.     

The effect of lime levels on the growth of beans and maize and nodulation of beans in three tropical acid soils

Abstract

A study to investigate the effect of lime on dry matter yield of maize (Zea mays) and beans (Phaseolus vulgaris) and nodulation of beans grown in three tropical acid soils (two humic Nitosols and one humic Andosol) was carried out in a greenhouse. The soils ranged from 4.2 to 5.0 in pH; 1.74 to 4.56 in %C; 21.0 to 32.0 meq/100g in CEC; 5.10 to 8.10 meq/100g in exchange acidity; 0.60 to 3.20 meq/100g in exchangeable (exch.) Al and 0.13 to 0.67 meq/ 100g in exch. Mn.

Exchange acidity and exch. Al decreased with increasing levels of lime in the three soils. Exchangeable Al was reduced to virtually zero at pH 5.5 even in the soils which had appreciable initial amounts. Exchangeable Mn also decreased with increasing levels of lime in the two Nitolsos. Exceptional results, however, were obtained with the Andosol where exch. Mn increased ten‐fold with the first level of lime and then decreased with subsequent levels.

In all the soils, mean dry matter yield of beans and maize, and mean nodule dry weight of beans generally increased significantly with increasing lime levels up to pH value of 6.0. The dry matter yield of beans and maize, and nodule weight of beans, however, decreased progressively with increasing lime levels beyond pH 6.0 value. pH range of 5.5 to 6.0 was considered optimum for the growth of maize and beans, and nodulation of beans in these soils.     

Effect of crop residue biochar on soil acidity amelioration in strongly acidic tea garden soils

Strongly acidic soil (e.g. pH < 5.0) is detrimental to tea productivity and quality. Wheat, rice and peanut biochar produced at low temperature (max 300 °C) and differing in alkalinity content were incorporated into Xuan‐cheng (Ultisol; initial pH_{soil/water = 1/2.5} 4.12) and Ying‐tan soil (Ultisol; initial pH _{soil/water = 1/2.5} 4.75) at 10 and 20 g/kg (w/w) to quantify their liming effect and evaluate their effectiveness for acidity amelioration of tea garden soils. After a 65‐day incubation at 25 °C, biochar application significantly (P < 0.05) increased soil pH and exchangeable cations and reduced Al saturation of both tea soils. Association of H⁺ ions with biochar and decarboxylation processes was likely to be the main factor neutralizing soil acidity. Further, biochar application reduced acidity production from the N cycle. Significant (P < 0.05) increases in exchangeable cations and reductions in exchangeable acidity and Al saturation were observed as the rate of biochar increased, but there were no further effects on soil pH. The lack of change in soil pH at the higher biochar rate may be due to the displacement of exchangeable acidity and the high buffering capacity of biochar, thereby retarding a further liming effect. Hence, a significant linear correlation between reduced exchangeable acidity and alkalinity balance was found in biochar‐amended soils (P < 0.05). Low‐temperature biochar of crop residues is suggested as a potential amendment to ameliorate acidic tea garden soils.     

不同切割酸度对奶豆腐品质影响研究

研究不同切割酸度对奶豆腐品质的影响,以确定其最佳切割酸度。采用单因素试验设计,切割酸度分别为45°T～50°T、55°T～60°T、65°T～70°T、75°T～80°T、85°T～90°T。在其他工艺条件相同的情况下,分别加工一批奶豆腐,然后测定奶豆腐的性能指标。结果表明,随着切割酸度的增加,奶豆腐的感官评定值先增加,然后逐渐降低;奶豆腐的pH4.6可溶性氮含量、质量分数12%TCA可溶性氮和游离氨基酸总量都逐渐增加;而pH值和水分含量逐渐降低。以感官评定值为主指标,结合其他性能指标,确定切割酸度为65°T～70°T。     

Fifteen-year fallow altered the dynamics of soil phosphorus and cationic balance of a savannah Alfisol

This study was designed to evaluate changes in the dynamics of soil phosphorus and cationic balances of a savannah soil subjected to 45 years of continuous cultivation under different fertilizer management and later left fallow for 15 years. It was conducted on the experimental plots at the Institute for Agricultural Research, Ahmadu Bello University, Nigeria. Treatments consisted of nitrogen (N), phosphorus (P), potassium (K), cow dung manure (D) and their combination (DNPK). Results of P fractionation and cationic distribution were compared with previous studies on the same plot 15 years ago. Organic carbon increased from a range of 3–5 g kg^?1 in 1997 to 10.9 g kg^?1 in 2012. Similarly, the cation exchange capacity (CEC) of the soil increased from 6.40 cmol_c kg^?1 in 1997 to 16.4 cmol_c kg¹ in the present study. The degree of saturation of the CEC by Ca²⁺ was 68–79% and 10–20% for Mg²⁺, while that of K⁺ was 1.5–2%. Although there was an uneven trend in depletion and enrichment of the various P pools, however, the fallow period substantially improved the CEC and the plant available P pools of the soil by more than 200% and 6–259%, respectively.