Response of interspecific and sativa upland rices to Mali phosphate rock and soluble phosphate fertilizer

In West Africa, two-thirds of upland rice is grown on acidic phosphorus (P)-deficient soils. Phosphorus is one of the most limiting-nutrients affecting crop productivity. A three-year field experiment was conducted on a Ferralsol in Côte d'Ivoire to study the response of four interspecific rice cultivars and a sativa (control cultivar) to Tilemsi phosphate rock (PR) and soluble triple superphosphate (TSP) fertilizer. PR was applied at 0, 150, 300, and 450 kg ha^?1 P once in the first year and residual effects were measured in the following years. TSP (0, 50, 100 and 150 kg ha^?1 P) was applied yearly. More significant yield increasing (38%) was observed in the second year. Annual application of 50 kg P ha^?1 as TSP or a one-time application of 150 kg P ha^?1 as PR was the optimum rate for the production of all cultivars. Higher rates of P from TSP (100 and 150 kg P ha^?1) gave 2–3 times greater residual P in soil than the optimum rate, inducing no further response of rice. Two interspecific cultivars were identified as the most acid- and low P-tolerant cultivars for improving rice production in West Africa humid forest zone.     

Factors influencing nitrogen inputs and outputs in two Scottish upland catchments

Abstract. The factors influencing inorganic nitrogen inputs in wet deposition in two upland catchments in northeast Scotland are discussed. Seasonal trends in nitrate-nitrogen concentrations in water draining from the catchments, and in monthly nitrate-nitrogen outputs, are reported and explained. The inputs in rain exceeded the output in the rivers in the two catchments by 3.9–9.4 kg ha⁻¹a⁻¹. Retention by vegetation probably plays a crucial role in nitrogen cycling in the uplands.     

Organic matter retention in an upland humic podzol; the effects of pH and solute type

This paper discusses the effects of different horizons and soil solution compositions on dissolved organic matter retention in a moorland podzol and compares the results with previous studies of forest podzols. Adsorption isotherms were constructed for each of the major horizons of a freely draining, upland, moorland, humic podzol from north-east Scotland, to investigate processes of retention and release of dissolved organic matter (DOM). Carbon retention of a range of solute types was studied, and phthalate was chosen as a model compound to measure carbon retention at three different pH values (3, 4.5 and 6). Retention and release of DOM was related to chemical, physical and mineralogical characteristics of the different soil horizons. All the mineral horizons retained DOM, with the Bs horizon most retentive. Solution pH did not significantly affect DOM retention in the O and A horizons. At pH 3 and 4.5 organic matter was weakly retained in the Bhs horizon, but strongly retained in the Bs and the Cx horizons. At pH 6 reversal of surface charge occurred in the Bs and Cx horizons resulting in the release of similar amounts of organic matter to that released from the O horizon at the same pH. The results demonstrate how podzols act as a ‘valve’ in controlling the input of dissolved organic compounds into surface and ground water, and how sensitive the controlling mechanisms are to pH change.     

Importance of plasmalemma ATPase in the retention and exclusion of inorganic ions

The experiments were focused on the question whether the plasmalemma ATPase activity (proton pump) has an influence on the efflux of major inorganic ion species. Efflux from roots of intact Trifolium pratense, Hordeum vulgare, Glycine max, and Zea mays was examined into a solution containing 100 μM CaCl₂ and 500 μM NH₄⁺ as sulfate in the control solution and 100 μM CaCl₂ and 500 μM NH₄⁺ as vanadate in the test solution. Vanadate being an inhibitor of the plasmalemma ATPase depressed significantly the H⁺ secretion of roots into the outer solution but had no major impact on the efflux of cation species. In the presence of vanadate significantly higher amounts of sulfate, phosphate, and nitrate were released into the outer solution by roots of soya and maize as compared with the control treatment (no vanadate). In the absence of vanadate, virtually no nitrate was released by all species examined whereas in the vanadate treatment significant amounts of NO₃^? were released. Vanadate inhibited the uptake of Cl^? in barley and maize and increased the uptake of Ca²⁺ in soya. It is concluded that the plasmalemma ATPase activity plays a major rule in the “ionic stat” of cells in providing protons to the apoplast for the reabsorption of sulfate, phosphate, and particularly nitrate which have leaked out of the cytosol.     

Role of phosphate and carboxylate ions in maillard browning

The Maillard reaction of carbohydrates and amino acids is the underlying chemical basis for flavor and color formation in many processed foods. Phosphate and other polyatomic anions will accelerate the rate of Maillard browning, and this effect has been explained by invoking enhanced proton abstraction from intermediate Amadori compounds. In this work, the effect of phosphate and carboxylate ions on browning was measured for a series of reducing sugars with and without the presence of beta-alanine. Significant browning was observed for sugars alone suggesting that polyatomic anions contribute to Maillard browning by providing reactive intermediates directly from sugars. A mechanism is proposed for decomposition of sugars by polyatomic anions and efforts to trap reactive species using o-phenylenediamine (OPD) are described. The results of this study suggest how complications may arise from the popular usage of phosphate buffers in the study of Maillard reaction kinetics. In addition, the results imply how phosphates may be useful for enhancing browning during food processing.     

Estimating the oxidative ratio of UK peats and agricultural soils

Organic matter in the terrestrial biosphere has a fundamental role in moderating the exchange of CO₂ between the atmosphere and the biosphere. One important property of organic matter is its oxidative ratio (OR); that is, the ratio of moles O₂ released per mole CO₂ sequestered through photosynthesis, that is, the lower the OR, less O₂ is released per mole of CO₂ fixed. In global assessments of CO₂ partitioning, the failure to account for changes in OR could lead to an underestimate of terrestrial carbon sequestration. It is known that OR can vary between environments and management, but what other factors could be playing a role in controlling OR? This study measured the OR of a range of peat (Histosols) and mineral soils (Inceptisols) under similar management from across the United Kingdom to investigate how OR varies within and between material types. The study shows that OR values varied significantly between material types (median peat OR = 1.10, median vegetation OR = 1.03 and median mineral soil OR = 1.14), and they also varied between study sites. Furthermore, there were no significant differences in OR with peat depth. Given the results from this study, we can suggest that future sampling strategies should include sampling of the major carbon pools (i.e. vegetation, litter and soil) and that, as a first approximation, OR can be examined on the basis of these carbon pools alone. The values measured in the study give a new residence time‐weighted global OR estimate for the terrestrial biosphere () of 1.056 ± 0.02.     

紫色土丘陵区保护性耕作下旱地土壤呼吸及影响因素

为了探讨保护性耕作对旱作农田土壤呼吸的影响,采用LI6400XT便携式光合作用测量系统自带的土壤呼吸室(6400-09)在重庆北碚西南大学试验农场对传统耕作(T,traditional farming)、垄作(R,ridge planting)、传统耕作+秸秆覆盖(TS,traditional farming+straw mulching)、垄作+秸秆覆盖(RS,ridge planting+straw mulching)、传统耕作+秸秆覆盖+秸秆速腐剂(TSD,traditional farming+straw mulching+decomposing agent)、垄作+秸秆覆盖+秸秆速腐剂(RSD,ridge planting+straw mulching+decomposing agent)6种处理下的西南紫色土丘陵区小麦/玉米/大豆套作体系中作物生长季节的土壤呼吸及其水热因子进行了测定和分析。结果表明,6种处理中土壤呼吸速率的季节变化明显,各处理日均土壤呼吸速率差异显著。其中在小麦-大豆条带,小麦土壤呼吸速率均值为1.53μmol m-2s-1,大豆土壤呼吸速率日均值为4.10μmol m-2s-1,各处理日平均土壤呼吸速率大小排序为TRTSTSDRSRSD。在空地-玉米-空地条带,玉米土壤呼吸日均值为2.56μmol m-2s-1,介于小麦和大豆土壤呼吸速率之间,各处理日平均土壤呼吸大小排序为RTRSTSRSDTSD。整个套作体系土壤呼吸总量C为1 543~2 134 g m-2,表现为TRRSTSTSDRSD。研究结果还显示土壤温度和土壤水分是影响旱地农田土壤呼吸的主要因素,二者分别解释了土壤呼吸季节变化的28.9%~53.7%和13.7%~42.0%。水热因子与土壤呼吸速率的回归分析表明,指数方程较好地模拟了土壤呼吸与10 cm土温的关系,土壤呼吸的温度敏感性指标Q10值在2.25~2.69之间;而土壤呼吸与5 cm土壤水分的关系以抛物线型函数模拟最优。土壤呼吸对土壤水分的响应阈值为14.94%。该研究为明确农田生态系统土壤呼吸变化规律及影响因素的控制机理提高参考,对估算全球碳平衡、评估区域碳源汇具有重要意义。     

钠和其他离子对钾离子替代作用的研究进展

为缓解钾素资源紧张的问题,不少学者提出了利用Na+等离子对K+的替代作用来解决。围绕K+、Na+在植物体内的生理功能、钾钠替代的生理效应以及存在的问题,着重阐述了钠对钾的替代作用;另外,还综述了K+与NH4+、Ca2+、Mg2+间的互作关系等。     

Mechanisms of phosphate retention by calcite: effects of magnesium and pH

Purpose

Sorption and precipitation of phosphate are important processes in controlling fate of phosphorus (P) in P-fertilized soils, especially those affected by magnesium (Mg) ions.

Materials and methods

The interaction between Mg(II) (0.42 and 8.33 mM) ions and phosphate (0.32 and 6.45 mM) at the calcite–water interface were investigated with various pH values from 6.0 to 12.0, using a combination of sorption envelopes, Fourier transform infrared spectroscopy, and X-ray diffraction.

Results and discussion

Amorphous calcium phosphate, dibasic calcium phosphate dihydrate, and hydroxyapatite are formed at high phosphate concentration (6.45 mM) and high pH (>8.0). The presence of low Mg(II) ion level (0.42 mM) had little effect on phosphate sorption. When Mg(II) ions increased to 8.33 mM, phosphate retention was inhibited in the weak acid condition since incorporation of Mg(II) ions kinetically hinders precipitation resulting in greater solubility of calcium phosphate while high pH favors Mg adsorption to provide more =Mg sites and OH functional groups on the surface of calcite, which enhanced the formation of Mg–P phases. The likely mechanism is attributed to the different surface terminations of calcite sorbed by phosphate at pH?<?8.0 and pH?>?8.0 in the presence of Mg(II) ions.

Conclusions

Our experimental results suggested that soil pH, initial concentration of phosphate, and the presence of Mg(II) ions and calcite play an important role to affect the fate of phosphate in P-fertilized soils.     

A critical evaluation of the factors influencing the dissolution of Gafsa phosphate rock

A carbonate-substituted phosphate rock (Gafsa, GPR) was allowed to dissolve in the presence of one or more of the following: an acid pH buffer (a source of protons), hydrous ferric oxide gel (Fe gel, a sink for P), and a cation exchange membrane (CEM, a sink for calcium). This allowed a quantitative evaluation of the individual and combined influences of three of the most important soil-related factors (pH, P sink, and Ca sink) which control phosphate rock (PR) dissolution in soils. At 44 d, pH alone (pH 6.1 compared to 4.5) had little effect on the extent of dissolution (1.5 and 6.0% dissolution of P, respectively), probably because of the Ca common-ion effect resulting from the preferential dissolution of the more-soluble CaCO, accessory phase. The inclusion of a P sink at pH 6.2 resulted in only a 3.2% dissolution of P after 44 d, whereas at pH 4.5 it increased dissolution from 6.0% to 9.8%. This suggests that pH and P sorption have an interactive effect in influencing GPR dissolution. Inclusion of a Ca sink had the largest influence on GPR dissolution. This was due to the ability of the Ca sink to remove accessory CaCO₂. At pH 6.2 the dissolution of P was 10 times larger in the presence of a Ca sink than it was in the presence of a P sink. Despite the smaller ratio of Ca sink size to GPR-Ca content relative to that of the P sink size to GPR-P content, the Ca sink was more effective in promoting GPR dissolution. The presence of the Ca sink resulted in twice as much dissolution of P at pH 4.5 than at pH 6.5. At pH 4.5, and in the presence of both the Ca sink and the P sink, 95% dissolution of GPR occurred over the 44-d experimental period.     

闽东南旱地土壤镁肥肥效与钾镁平衡施肥技术研究

闽东南旱地土壤的24个代表性土样测定结果表明,缺镁土样占71%;花生增施镁肥增产幅度为3.7%～25.8%,大豆和柑桔则为7.5%～15.7%;在钾肥最佳用量基础上配施镁肥,镁肥的增产作用最大,钾镁平衡施肥才能大幅度提高花生、大豆和柑桔产量.     

Distribution of nitrifying and heterotrophic microorganisms in cutover peats

The distribution of chemoautotrophic nitrifiers, heterotrophic bacteria, actinomycetes and fungi was studied in raised peats and compared with a mineral garden soil. Nitrosomonas was not detectable but a few Nitrobacter were counted 350 cm below the surface of undrained peat, in the surface areas of drained non-cutover peat and in an area cutover before sampling. After only 3 y cultivation and cropping the average numbers, over 12 monthly samplings, of Nitrosomonas and Nitrobacter had risen to 1.25 × 10⁶ and 32.7 × 10⁶, respectively.The possible reasons for the anomalously high proportion of Nitrobacter are discussed, including the effect of media composition. A NaHCO₃ medium gave lower numbers of Nitrosomonas and higher numbers of Nitrobacter than a CaCO₃ medium.The proportional increase in the heterotrophs was lower than that of the autotrophs. This suggested that low availability of organic substrate and not the physical environment was the limiting factor. Only fungi showed a definite seasonal variation.     

Chemisorption of phosphate ions and destruction of organomineral sorbents in acid soils

The chemisorption mechanisms of phosphate anions by iron (aluminum) containing sorbents in a soil under high phosphate loads were studied. The role of the metal-phosphate anions in the destruction of the sorbents was discussed. It was shown that the chemisorption of phosphate anions and the destruction of phosphated organomineral sorbents are interrelated processes. A significant part of the chemisorbed phosphates in association with sorbent metals and carbon passes into the liquid phase of soil systems.     

长期施肥下红壤旱地磷素有效性影响因子的冗余分析

以长期施肥(1988～2014年)的红壤旱地为研究对象,以全磷(TP)、有效磷(Bray-P)为响应变量,土壤pH值、大小粒级团聚体组成比例(PSAi)、铁铝氧化物、阳离子交换量(CEC)、分形维数(D)等指标为解释变量,借助于冗余分析(RDA)方法探讨各指标变量与红壤旱地TP和Bray-P含量变化的相关关系.研究结果...     

Availability of phosphate and potassium as the result of interactions between root and soil in the rhizosphere

A number of findings are summarized in order to show the significance of individual plant properties and soil factors on the availability of phosphate and potassium to plants growing in soil. The flux of a nutrient into a given plant root depends directly on the concentration of the nutrient in the adjacent solution. In nutrient solution, P and K influx follows Michaelis-Menten kinetics. Almost maximum rates of influx have been observed in the range of soil solution concentrations usually found in German arable soils. Roots exhaust P and K from solutions to about 0.2 μmol P and 1 μmol K 1^?1 if not replenished. At the root surface P and K concentrations in soil decrease rapidly within one day; small changes occur after this period. Initially, the extent of the depletion zone is very small but it extends radially with time. After the initial phase therefore, P and K supply to the plant depends on transport from more remote parts of the soil and also on release from undissolved sources. The degree of depletion and the extent of the depletion zone are related to the diffusion coefficient; they decrease with increasing clay content of soil. Root hairs penetrate the soil and extend the volume of soil supplying nutrients to a unit of root. P and K influx therefore increase with the length of root hairs. Proton release of roots mobilize P and K in soil. This is clearly detected by the HCl-soluble P and K fractions within 2 mm of the root surface. The activity of acid and alkaline phosphatases strongly increase in the soil in the vicinity of the root surface of several plant species. It is supposed that organic P compounds can therefore be utilized by plants. P and K influx per unit of root length and root length per unit of shoot weight differed widely between species. The product of these two parameters however was closely related to the P and K concentration of the shoots. Calculations from a mathematical model were in good agreement with measured K depletion profiles and K uptake by plants. It is therefore concluded that the main factors influencing the P and K availability of plants growing in soil have been accounted for in the mathematical model and that the parameters have been accurately measured.     

Chemical and mineralogical weathering rates and processes in an upland granitic till catchment in Scotland

Weathering in an upland granitic till catchment receiving an intermediate level of acidic deposition has been studied by chemical and mineralogical analyses of soil profiles and chemical analysis of precipitation and streamwater. Long-term weathering rates for base cations calculated from analyses of soil profile horizons using Zr as an internal, immobile, index element are similar for alpine podzols and peaty podzols and are 2–3 meq.m^–2.a^–1 for Ca and Mg, and 10–11 meq.m^–2.a^–1 for K and Na. The high loss of Na is associated with the weathering of oligoclase, particularly in the coarse sand fraction. Loss of K is related to weathering of K-feldspar and micas. Current weathering rates for base cations calculated from input-output budgets are higher than long-term rates by factors of 12, 8 and 3 for Ca, Mg and Na, but lower by a factor of 7 for K probably due to biomass uptake. The higher current overall loss of base cations may be due to increased rates of weathering in recent times but this is not conclusive as there are large uncertainties inherent in both methods of estimation.     

施用碱稳定污泥污水土壤经γ-辐照后土壤溶液中Cu和Zn

Soil samples collected from several acid soils in Guangdong, Fujian, Zhejiang and Anhui provinces of the southern China were employed to characterize the chemical species of aluminumions in the soils. The proportion of monomeric inorganic Al to total Al in soil solution was in the range of 19% to 70%, that of monomeric organic Al (Al-OM) to total Al ranged from 7.7% to 69%, and that of the acid-soluble Al to total Al was generally smaller and was lower than 20% in most of the acid soils studied. The Al-OM concentration in soil solution was positively correlated with the content of dissolved organic carbon (DOC) and also affected by the concentration of Al³⁺. The complexes of aluminum with fluoride (Al-F) were the predominant forms of inorganic Al, and the proportion of Al-F complexes to total inorganic Al increased with pH. Under strongly acid condition, Al³⁺ was also a major form of inorganic Al, and the proportion of Al³⁺ to total inorganic Al decreased with increasing pH. The proportions of Al-OH and Al-SO₄ complexes to total inorganic Al were small and were not larger than 10% in the most acid soils. The concentration of inorganic Al in solution depended largely on pH and the concentration of total F in soil solution. The concentrat ions of Al-OM, Al³⁺, Al-F and Al-OH complexes in topsoil were higher than those in subsoil and decreased with the increase in soil depth. The chemical species of aluminumions were influenced by pH. The concentrations of Al-OM, Al³⁺, Al-F complexes and Al-OH complexes decreased with the increase in pH.     

Influence of phosphate and hydroxyl ions on aluminum toxicity in soybeans and wheat

Aluminum (Al) toxicity to plants in complete nutrient solutions is difficult to relate to Al activity in solution because of precipitation and complexation. Aluminum toxicity was studied for two seedling crops, sorghum (Sorghum bicolor L. Moench) and wheat (Triticum aestivum L. em Thell), at low levels (≤10 μM) in two incomplete nutrient solutions to study plant response to Al alone, Al+PO₄ ^3‐, Al+OH^‐, and Al+PO₄ ³‐+OH^‐. Relative root length was the bioassay for Al toxicity. ‘Monomeric’ Al was measured using Aluminon and both root length and measured Al were compared to the theoretical Al in solution predicted by the MINTEQA2 equilibrium model.

Low levels of Al were toxic to plant roots with sorghum showing a decrease in relative root length from 1 to 10 μM Al, and wheat showing a decrease from 4 to 10 μM. A mono‐salt background solution (400 μM CaCl₂) and a more complex base solution (CaCl₂, KNO₃, and MgCl₂) gave similar root lengths and measured Al values. Phosphate and hydroxyl ameliorated Al toxicity and lowered measured Al in solution, but not to the extent predicted by the model. Adding phosphate (PO₄ ^3‐) or hydroxyl (OH^‐) raised the pH, but again not as high as the model predicted. The difference in toxicity and measured Al were most likely the result of polymers (Al⁺³) which are toxic, but not measured by the procedure used, or included in the model which showed the Al as being removed from solution by precipitation.     

Applicability of thermal methods for characterization of peats and plants

Differential thermogravimetric (DTG) and differential thermal analysis (DTA) curves were obtained for some peat materials and peat-forming plants. Four peats were selected on the basis of botanical composition and degree of decomposition. Granulometric fractions and holocellulose preparations from the peats were also analyzed.

The DTG curves showed three main regions of weight loss: the first at 275°–325°C the second at 360°–460°C and the third at 500°–560°C. The first region with a peak at 300°C was by far the most important. It was associated with cellulosic materials which may reflect the degree of decomposition. The size of the 300°C peak could be used for measuring holocellulose in peats, and this might be a valid substitute for chemical means for that measurement, specially in more decomposed peats.

The nature of the 300°C peak did not change significantly with changes in particle size, although the position of the 420°C peak was shisfted toward lower temperatures as particle size decreased. The original features of the peats were generally retained in the separates. Even though the predominance of residues from one species of plants in a particular peat did not greatly influence the shape of the DTG curves, some generalizations concerning the botanical sources of peats were obtained.

In a comparison of DTG and DTA methods, the former appears to provide more useful information on the chemical make-up and on the degree of decomposition of peats.