Fixed ammonium and potassium release from two soils

Abstract

Release of native and added K⁺ and NH⁺ ₄ from two soils was monitored during a 166 day incubation/leaching experiment. One soil (Brookston) represented a major soil series In Ontario whereas the other (Harriston) was suspected having a relatively large fixation capacity. Treatments were imposed involving addition of 50 μM g^‐1 soil of K⁺(KCl) or NH⁺ ₄ (NH₄Cl) only or one added after the other on successive days. The addition of either K⁺ or NH⁺ ₄ on day 2 tended to inhibit the release of the other added on day I. Also the addition of either K⁺ or NH⁺ ₄ on day 1 tended to inhibit the sorption or fixation of the other on day 2. The release rate of K⁺ during the 10 to 166 day period was almost constant and not affected by the addition of NH⁺ ₄. Alternatively, the addition of K⁺ on day 2 slowed the release rate of NH⁺ ₄ measured by NO^? ₃ appearance from day 10 to 40 but had no effect thereafter. At the end of the experiment considerably more K⁺ than NH⁺ ₄ was retained suggesting that K⁺ was more firmly fixed. However, the continuing nitrification of NH⁺ ₄ must be contrasted with periodic removal of K⁺ by leaching with 0.01 M CaCl₂ solution since the equilibrium between exchangeable and fixed ions was affected. There were no notable differences between the two soils inspite of a considerable difference in clay content.     

Effect of potassium on uptake and translocation of sodium and potassium in Chinese cabbage under NaCl stress

To investigate the influence of potassium (K⁺) on the salinity tolerance of Chinese cabbage (Brassica pekinensis Rupr.) seedlings, the plants were cultured at three K⁺ levels (0, 5, or 10?mM), under normal (0?mM NaCl) and high-salt (100?mM NaCl) conditions. The results indicated that the dry weight of Chinese cabbage increased with the application of K⁺ under salt stress. Addition of K⁺ increased K⁺ concentrations and suppressed sodium (Na⁺) concentration, which eventually increased the K⁺/Na⁺ ratios in roots or shoots. Application of K⁺ enhanced the uptake of K⁺ and suppressed the uptake of Na⁺. Moreover, the ratios of shoot-K⁺/root-K⁺ increased considerably, but the ratios of shoot-Na⁺/root-Na⁺ decreased in response to K⁺ application. It was concluded that the application of K⁺ could enhance the salt stress tolerance in Chinese cabbage because more K⁺ than Na⁺ was absorbed and translocated from roots to shoots.     

Oxalic Acid Effect on Potassium Release from Typical Rice Soils of Kashmir

Batch experiments were employed to examine the influence of oxalic acid on release kinetics of potassium (K) from soils along with adsorption and desorption of soil K⁺. The soils used were three rice soils from high-, mid-, and low-altitude zones. The results showed that soil K extracted using 0.2 mol L^–1 oxalic acid was similar to that of 1 mol L^–1 boiling nitric acid (HNO₃). The relation between K release (y) and concentrations of oxalic acid (c) could be best described as y = a + b log c, whereas the best-fit kinetic equation of K release was y = a + b √t. The K release for soils was in the order Bonbagh > Ganasthan > Kreeri. An oxalic acid solution with low pH was able to release more K. Oxalic acid decreased soil K⁺ adsorption and increased desorption, the effect of which tended to be greater at lower pH.     

自生固氮菌对土壤钾的活化作用

以土壤为钾源,通过液培试验研究了5株自生固氮菌(Azotobacter sp.)对土壤钾的活化作用。结果表明,自生固氮菌能分泌大量的氢离子,大幅度降低培养液p H,使氢离子浓度提高40倍以上。自生固氮菌分泌有机酸的种类与数量因菌株不同而异,这些有机酸包括甲酸、乙酸、草酸、丁二酸、柠檬酸、苹果酸和乳酸等。其中,全部供试菌株均能分泌草酸和苹果酸。在自生固氮菌的培养液中,钾浓度显著高于未接种的培养液,但土壤矿物结构钾则显著降低。由于土壤是培养液钾的唯一来源,说明自生固氮菌可促进土壤矿物钾溶解。相关分析表明,土壤矿物结构钾与自生固氮菌的有机酸分泌总量呈显著负相关(r=-0.845*,n=6),与培养液p H呈显著正相关(r=0.702*,n=6),说明自生固氮菌分泌的有机酸和氢离子可能溶解土壤矿物钾。考虑到自生固氮菌的草酸分泌量最大,络合钙、镁、铁、铝的能力最强,且与有机酸分泌总量呈极显著正相关(r=0.990**,n=6),推测草酸的分泌在活化土壤无效钾的过程中起重要作用。接种自生固氮菌显著降低土壤无效钾,活化能力因菌株不同而异,其原因可能与有机酸分泌的数量和种类有关。     

Evaluation of Chemical Extraction Methods for Determining Plant-Available Potassium in Some Soils of West Bengal,India

The effectiveness of eight chemical extraction methods was evaluated on 15 Indian soils for the prediction of plant-available potassium (K⁺) to Sudan grass (Sorghum vulgare var. sudanensis) grown in modified Neubauer technique. Average amounts of soil K⁺ extracted were in descending order: Morgan’s reagent > 0.5 M sodium bicarbonate (NaHCO₃) > neutral 1N ammonium acetate (NH₄OAc) > 1N nitric acid (HNO₃) > 0.02 M calcium chloride (CaCl₂) > 0.1N HNO₃ > Bray and Kurtz No.1> distilled water. The highest simple correlation with plant K⁺ uptake was obtained with NH₄OAc-K⁺ (r = 0.866**) and the lowest with CaCl₂-K⁺ (r = 0.45*). To develop the predictive models using stepwise regression, plant K⁺ uptake was used as the dependent variable and the extractable soil K⁺, pH, sand, silt and organic carbon (C) contents as the independent variables. Based on the final R², the NH₄OAc model was found to be the best predictor of plant-available K⁺ in the soils when used along with sand and organic C.     

日光温室栽培土壤供钾状况及K-Ca吸附交换特性研究

研究了陕西关中地区不同日光温室栽培土壤钾素供应状况及土壤K+、Ca2+离子吸附交换特性。结果表明,日光温室栽培的土壤钾素Q/I曲线及参数与大田栽培土壤明显不同。温室栽培（土娄）土和潮土钾素活度比（AR0）较相应大田土壤分别提高了14.8和6.9倍,土壤对外源钾的缓冲能力下降;从K+和Ca2++Mg2+的交换自由能看,温室栽培土壤存在钾素过多,K+和Ca2++Mg2+离子比例失调问题。不同K+/Ca2+摩尔比下,随着K+、Ca2+总浓度的提高,大田及温室栽培土壤对K+、Ca2+的吸附量均呈线性增加趋势,温室栽培土壤K+吸附率及两种土壤Ca2+吸附率均呈对数增加趋势。K+/Ca2+为2:1时,K+吸附量远大于K+/Ca2+为1:2.5时的吸附量;K+/Ca2+为2:1时,温室栽培土壤Ca2+均呈解吸状态。土壤对K+、Ca2+离子吸附的相对选择性随K+/Ca2+比例及溶液离子总浓度的变化而变化。K+/Ca2+为2:1时,土壤对K+的相对吸附选择性大,K+/Ca2+为1:2.5时,温室栽培土壤对Ca2+的相对吸附选择性显著增加。加入土壤K+的比例和数量过高,非但未提高K+离子的活度,还造成胶体上Ca2+离子的大量解吸,由此可能带来的日光温室土壤胶体稳定性降低及养分不平衡的问题值得关注。     

固定态铵的含量及中国某些耕地土壤NH4+的固定能力

Fixed ammonium contents and NH4^ fixation capacities of some representative cultivated solis collected from 16 provinces of China were studied.Results showed that the contents of fixed ammonium in soils ranged from 35 to 573 mg N kg^-1,with an average of 198mg Nkg^-1.The content of fixed ammonium correlated very significantly with mica content for tropical and subtropical soils,whereas this was not the case for soils in the temperate zone.At the end of K-exhausting experiment the fixed ammonium content increased in most soils studied.However,it decreased in smom temperate soils.Generally,fixation of added NH4^ could not be found either before or after K-exhausting experiment for highly weathered soils,including tropical soils and soils derived from granite-gneiss or Quaternary red clays in the subtropic zone,while for most soils in the Yangtze River dalta the NH4^ fixation capacity was rather high and increased significantly in the K-exhausted soils.     

红壤交换性钙、镁和钾的分布及施肥对其影响

A leaching experiment was Carried out with repacked soil columns in laboratory to study the leaching process of a red soil derived from sandstone as affected by various fertilization practices.The treatments were CK(as a control),CaCO3,CaSO4,MgCO3,Ca(H2PO4)2,Urea,KCl,Multiple(a mixture of the above mentioned fertilizers) and KNO3,The fertilizers were added to the bare surface of the soil columns,and then the columns were leached with 120 mL deionized water daily through perstaltic pumps over a period of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles ,i.o.,of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles,I.e.0-5cm,5-10cm,10-20cm,20-40cm,and 40-60cm,The results showed when applying Ca,Mg,and K to the bare surface of the soil columns,exchangeable Ca^2 ,Mg^2 ,and K^ in the upper layer of the soil profile increased correspondingly,with an extent depending mainly on the application rates of Ca,Mg,and K and showing a downward trend,CaCO3,CaSO4,MgCO3,and Ca(H2PO4)2 treatments had scarcely and effect on movement of exchangeable K^ ,while CaCO3,and CaSO4 treatments singnificantly promoted the downward movement of exchangealble Mg^2 although these two treatments had no obvious effect on leaching losses of Mg,The fact that under Urea treatment,exchangeable Ca^2 and Mg^2 ,were higher as compared to CK treatment showed urea could prevent leaching of exchangeable Ca^2 and Mg^2 ,the obvious downward movement of exchangeable Ca^2 and Mg^2 was noticed in KCl treatment ,In Multiple treatment,the downward movement of exchangeable Ca^2 and Mg^2 was evident,while that of K^ was less evident,Application of KNO3 strongly promoted the downward movement of exchangeable Ca^2 and Mg^2 in the soil profile.     

Variation in the relationship between nitrification and acidification of subtropical soils as affected by the addition of urea or ammonium sulfate

The effects on nitrification and acidification in three subtropical soils to which (NH₄)₂SO₄ or urea had been added at rate of 250 mg N kg⁻¹ was studied using laboratory-based incubations. The results indicated that NH₄⁺ input did not stimulate nitrification in a red forest soil, nor was there any soil acidification. Unlike red forest soil, (NH₄)₂SO₄ enhanced nitrification of an upland soil, whilst urea was more effective in stimulating nitrification, and here the soil was slightly acidified. For another upland soil, NH₄⁺ input greatly enhanced nitrification and as a result, this soil was significantly acidified. We conclude that the effects of NH₄⁺ addition on nitrification and acidification in cultivated soils would be quite different from in forest soils. During the incubation, N isotope fractionation was closely related to the nitrifying capacity of the soils.     

Aluminum concentrations in sclerotia from a buried humic horizon of volcanic ash soils in Mt. Myoko,Central Japan

The morphology and chemical composition of fungal sclerotium-like grains collected from the buried humic horizon of volcanic ash soil in Mt. Myoko were examined using a scanning electron microscope (SEM), energy dispersion xray micro-analyzer (EDX), and electron probe micro-analyzer (EPMA). A high C content, low level of Si and high concentration of Al characterized the grains considered to correspond to the sclerotia of Cenoccocum graniforme. The ²⁷Al MAS NMR spectrum of the sclerotia showed the existence of 6- and 4-coordinated Al. X-ray diffraction analyses supported the presence of amorphous Al (ex. Al-humus complex) in the sclerotia.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance

K⁺/Na⁺ and Cl^‐ effects on activity of amylases as well as on their isoenzyme pattern in leaves of bushbeans and sugarbeets at the beginning of salinity stress were investigated, in plants grown in water culture under controlled environmental conditions. Alpha‐ and beta‐amylase activity in beans increased, particularly due to K⁺ and Cl^‐ supplied. In sugarbeets amylase activity remained unchanged as a result of K/Na treatment in combination with Cl and decreased using SO₄ ^2‐ as counterion. A direct correlation of amylase activity to the starch content of both species was not detctable. Particularly α‐but also ß‐amylase was most strongly inhibited by KCl “in vitro”. Independent on their origin, amylases from bushbeans and sugarbeets did not show any differences in ionic inhibition “in vitro”. The isoenzyme pattern of the species was different, but no clear ionic effect was detectable. Amylolytic activity is evidently not a causative factor for restricted starch mobilization in leaves under an early salinity stress. It is suggested that amylases are indirectly involved in starch formation via degradation due to a lack of a carbohydrate sink under salinity stress. Differences in salt tolerance of the investigated crops are obviously not related to different “in vitro” properties of amylases.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance

The relation between activity of soluble acid invertase and sucrose content in leaves of young bushbeans (salt sensitive) and sugarbeets (salt tolerant) and ion‐specific effects of salinity environment were investigated. For comparison the response of isolated invertase from both plant species to ion combination and ion concentration was investigated. The plants were grown in water culture under controlled conditions.

In busbean leaves invertase activity decreased while sucrose increased. K⁺ with Cl^‐ as counterion was most effective “in vivo”;. However, there was little change in invertase activity or sucrose content in sugarbeet leaves. Independent of the origin of the enzyme, invertase activity was not affected by either ion concentration or ion combination “in vitro”;. Acid invertase might be a key enzyme in the utilization of carbohydrates. The ionic effect on acid invertase activity and carbohydrate content in intact plant tissue could be a possible indicator of salt tolerance of crops.     

Evaluating soil sodium indices in soils of volcanic nature conducive or suppressive to Fusarium wilt of banana

The ability of three soil Na indices to predict soil conduciveness or suppressiveness to disease caused by the soil fungus Fusarium oxysporum f. sp. cubense was evaluated in seven banana plantations from the Canary Islands (Spain). These indices were exchangeable sodium percentage (ESP), soluble Na (SS₀) and sodium adsorption ratio (SAR₀) in 1:2.5 soil-water extracts (SAR_w and total cationic concentration (TCC_w)=0. Sodium selectivity coefficients (K_G0,K₀) and TCC₀ were calculated from soil exchange and solution data. The effects of ESP, SAR₀, SS₀, TCC₀, K_G0 and K₀ on soil available iron (Fe extracted from soil by DTPA) and aggregate stability in water (water-stable aggregates (WSA), 200-2000 μm) were also studied. Our results showed that SAR₀ calculated using cationic concentrations in 1:2.5 extracts might be a good indication of a relationship between SS₀ and soluble divalent cations in conducive and suppressive volcanic soils to Fusarium. Both TCC₀ and dispersion-flocculation concentrations seem to be not linked to soil suppressiveness or conduciveness to Fusarium wilt. These results suggested that soil physical properties seem to be not controlled by Na behaviour in these type of soils and, therefore, sodicity and salinity should not be a problem from a physical point of view. Moreover, SS₀ and SAR₀ were always greater in suppressive areas than in conducive areas. SAR₀ was significantly correlated with SS₀ but correlations between ESP against SS₀ and SAR₀ were weak. For SAR₀ values above 2.5 (mmol_c l⁻¹)^1/2 and ESP values below 15%, the exchangeable Na did not seem to be related to the capacity of suppressive areas to release more Na to soil solution. Larger values of SS₀ were observed in suppressive areas for these values of SAR₀ and ESP. It implies a lower quantity of soluble Na salts in conducive samples. A high Na salt content in soil can produce an increase of soil pH, which exerts a negative influence on available Fe release to soil solution. A clear separation between conducive and suppressive samples from relations between SS₀ and SAR₀ against WSA and Fe-DTPA showed that SS₀ and SAR₀ can be satisfactory indices to study the influence of Na concentrations on the incidence of Fusarium wilt. The mass of WSA increase in conducive areas might be favoured by the smaller amounts of soil solution Na found in these samples. In conclusion, our data provide evidence that release of Na to soil solution could favour soil suppressiveness to Fusarium wilt limiting soil aggregation and the availability of Fe, at least in soils of volcanic nature that are not affected by salinity or sodicity processes.     

Carbon mineralization in soils of different textures as affected by water-soluble organic carbon extracted from composted dairy manure

The water-soluble organic C in composted manure contains a portion of labile C which can stimulate soil microbial activity. The objective of this experiment was to evaluate the effects of water-soluble organic C extracted from composted dairy manure on C mineralization in soil with different textures. Three soils with textures varying from 3 to 54% clay were amended with 0 to 80 mg water-soluble organic C kg^–1 soil extracted from a composted dairy manure and incubated for 16 weeks at 23°C. The total amount of C mineralized was greater than the amount of C added in the three soils. Differences in mineralizable C with and without added water-soluble organic C were approximately 13–16 times, 4.8–8 times, and 7.5–8 times greater than the amount of C added to clay, loam, and sand soils, respectively. The results of this experiment suggest that immediately following composted manure applications, C mineralization rates increase, and that most of the C mineralized comes mainly from the indigenous soil organic C pool.CLBRR contribution No. 94-71     

Correction of iron chlorosis in peanut (arachis hypogea shulamit) by ammonium sulfate and nitrification inhibitor

Peanut (Arachis hypogea cv. Shulamit) grown on very high calcium carbonate (CaCO₃) content soils is showing iron (Fe) chlorosis symptoms. Supplying the plant with ammonium sulphate ((NH₄)₂SO₄) in the presence of nitrapyrin (N‐Serv) for preventing nitrification reduced Fe chlorosis. Nitrate (NO^‐ ₃) developed in the soil with time, even with nitrapyrin present. When ammonium (NH⁺ ₄) was even less than 20% of the total mineral N in the soil, no Fe‐stress could be observed, suggesting that the NH⁺ ₄ uptake by the plant and the consequence of hydrogen (H⁺) efflux occurs from the root to the rhizosphere, resulting in a decrease of redox potential near the root, and solubilizing enough Fe near the root to overcome the chlorosis.     

Gross N transformation rates and net N mineralisation rates related to the C and N contents of soil organic matter fractions in grassland soils of different age

We investigated the relationship between soil organic matter (SOM) content and N dynamics in three grassland soils (0-10 and 10-20 cm depth) of different age (6, 14 and 50 y-old) with sandy loam textures. To study the distribution of the total C and N content the SOM was fractionated into light, intermediate and heavy density fractions of particulate macro-organic matter (150-2000 μm) and the 50-150 μm and <50 μm size fractions. The potential gross N transformation rates (mineralisation, nitrification, NH₄⁺ and NO₃⁻ immobilization) were determined by means of short-term, fully mirrored ¹⁵N isotope dilution experiments (7-d incubations). The long-term potential net N mineralisation and gross N immobilization rates were measured in 70-d incubations. The total C and N contents mainly tended to increase in the 0-10 cm layer with increasing age of the grassland soils. Significant differences in total SOM storage were detected for the long-term (50 y-old) conversion from arable land to permanent grassland. The largest relative increase in C and N contents had occurred in the heavy density fraction of the macro-organic matter, followed by the 50-150 and <50 μm fractions. Our results suggest that the heavy density fraction of the macro-organic matter could serve as a good indicator of early SOM accumulation, induced by converting arable land to permanent grassland. Gross N mineralisation, nitrification, and (long-term) gross N immobilization rates tended to increase with increasing age of the grasslands, and showed strong, positive correlations with the total C and N contents. The calculated gross N mineralisation rates (7-d incubations) and net N mineralisation rates (70-d incubations) corresponded with a gross N mineralisation of 643, 982 and 1876 kg N ha⁻¹ y⁻¹, and a net N mineralisation of 195, 208 and 274 kg N ha⁻¹ y⁻¹ in the upper 20 cm of the 6, 14 and 50 y-old grassland soils, respectively. Linear regression analysis showed that 93% of the variability of the gross N mineralisation rates could be explained by variation in the total N contents, whereas total N contents together with the C-to-N ratios of the <50 μm fraction explained 84% of the variability of the net N mineralisation rates. The relationship between long-term net N mineralisation rates and gross N mineralisation rates could be fitted by means of a logarithmic equation (net m=0.24Ln(gross m)+0.23, R²=0.69, P<0.05), which reflects that the ratio of gross N immobilization-to-gross N mineralisation tended to increase with increasing SOM contents. Microbial demand for N tended to increase with increasing SOM content in the grassland soils, indicating that potential N retention in soils through microbial N immobilization tends to be limited by C availability.     

Savanna-derived organic matter remaining in arable soils of the South African Highveld long-term mixed cropping: Evidence from C and N natural abundance

Sustainable agriculture requires the formation of new humus from the crops. We utilized ¹³C and ¹⁵N signatures of soil organic matter to assess how rapidly wheat/maize cropping contributed to the humus formation in coarse-textured savanna soils of the South African Highveld. Composite samples were taken from the top 20 cm of soils (Plinthustalfs) cropped for lengths of time varying from 0 to 98 years, after conversion from native grassland savanna (C4). We performed natural ¹³C and ¹⁵N abundance measurements on bulk and particle-size fractions. The bulk soil δ¹³C values steadily decreased from −14.6 in (C4 dominated) grassland to −16.5‰ after 90 years of arable cropping. This δ¹³C shift was attributable to increasing replacement of savanna-derived C by wheat crop (C3) C which dominated over maize (C4) inputs. After calculating the annual C input from the crop yields and the output from literature data, by using a stepwise C replacement model, we were able to correct the soil δ¹³C data for the irregular maize inputs for a period of about one century. Within 90 years of cropping 41-89% of the remaining soil organic matter was crop-derived in the three studied agroecosystems. The surface soil C stocks after 90 years of the wheat/maize crop rotation could accurately be described with the Rothamsted Carbon Model, but modelled C inputs to the soil were very low. The coarse sand fraction reflected temporal fluctuations in ¹³C of the last C₃ or C₄ cropping and the silt fraction evidenced selective erosion loss of old savanna-derived C. Bulk soil ¹⁵N did not change with increasing cropping length. Decreasing δ¹⁵N values caused by fertilizer N inputs with prolonged arable cropping were only detected for the coarse sand fraction. This indicated that the present N fertilization was not retained in stable soil C pool. Clearly, conventional cropping practices on the South African highlands neither contribute to the preservation of old savanna C and N, nor the effective humus reformation by the crops.     

Microscopic observation of charred plant fragments isolated from several Ando soil samples by the specific gravity method

Abstract

Charred plant fragments were isolated from 5 Ando soil samples, containing Type A humic acids, by the specific gravity (s.g.) method using a sodium polytungstate solution as heavy solution. Microscopic observation indicated that the charred plant fragments, which are black or blackish brown, were the main components in both fractions of less than s.g. 1.6 Mg m^?3 that had been isolated before and after HCl-HF treatment of the soil samples. Furthermore, it was suggested that most of the fragments in the < 1.6 fractions isolated before the treatment originated from woody plants. On the other hand, the fragments in the < 1.6 fractions isolated after the treatment were mainly amorphous, although the shape of several fragments was similar to that of vascular tissues of woody and herbaceous plants. The sum of the organic-C contents of both < 1.6 fractions ranged from 4.08 to 47.8 g kg^? whole soil, and 3.8–32.7% of total organic-C of the whole soil originated from these fractions. No constant relationship was observed between the organic-C contents of both fractions and the morphological characteristics of the charred plant fragments.