Effect of soil pH on phosphorus-soil reactions determining phosphorus availability in acid soils

Soil pH has been reported to affect the behavior of phosphorus (P) in soils and phosphate uptake by plants. Research is needed to verify the Barber-Cushman mechanistic nutrient uptake model under varying soil pH\u27s. Conflicting views are held regarding the effect of soil pH on P availability. The effect may vary with soils and the reasons for the differences are not well understood. A pot experiment (Part I) was conducted to evaluate the accuracy of the Barber-Cushman nutrient uptake model for predicting P and K uptake at six levels of soil pH in an acid Chalmers silt loam. This study showed that the Barber-Cushman nutrient uptake model accurately predicted the effect of soil pH on P (Y = 1.7 + 0.97 X, r\sp2 = 0.97) and K (Y = 67 + 0.94 X, r\sp2 = 0.995) uptake by maize. Three different acid soils varying in their chemical properties were used to evaluate the effect of type of soil with regard to soil pH and P rates on soil supply parameters, P\sb{\rm li}, P concentration in soil solution, P\sb{\rm si}, P concentration on solid phase, and b, buffer power of soil, and predicted P uptake using the Barber-Cushman nutrient uptake model (Part II). In addition, two different incubation times of pH adjustment, and four different reaction times after P addition were studied to evaluate the effect of aging on pH adjustment and P addition on P\sb{\rm li}, P\sb{\rm si}, b, and predicted P uptake (Part III). The results of this research show that the Barber-Cushman nutrient uptake model can (i) satisfactorily predict the effect of soil pH on P and K uptake by maize, (ii) show that the reason for the difference among soils in their ability to provide P for absorption by plants as affected by soil pH is mainly due to the effect of soil pH on P\sb{\rm li}, and (iii) estimate the effectiveness of added P with reaction time after P addition

Studies on the gene expression in different aluminum-resistance pineapples

Pineapple (Ananas comosus (L) Merrill) is one of an economically cultured crops in Taiwan. It is normally cultivated in soils containing strong acidity where aluminum (Al) often inhibits the growth of crop roots. This research was carried out with the objective of identifying the main genes that directly influence aluminum tolerance by resistant and non-resistant pineapples (Cayenne and Tainung No. 17, respectively). For this reason, both cultivars were grown in hydroponic nutrient solution, each containing 0 and 300 μM AlCl3, in a growth chamber for four weeks. Samples of root apices were taken, followed by extraction of RNA, selection of primers, sequencing and processing of PCR. Finally, after examination of genes, the relative expressions of them for both cultivars were determined by quantitative PCR. The results obtained from polymerase chain reaction experiments proved the Al-resistance characteristics of pineapples are mainly regulated by two genes, namely GAPDH (glyceraldehyde-3- phosphate-dehydrogenase) and FBA (fructose biphosphate adenosine). This result may provide important indications for the study of advancing genetic mechanisms on Al-resistance in pineapplesLa piña (Anonas comosus (L) Merrill) es uno de los cultivos económicamente importantes en Taiwán. Normalmente se cultiva en suelos que contienen una acidez fuerte donde el aluminio (Al) a menudo inhibe el crecimiento de las raíces. Esta investigación se realizó con el objetivo de identificar los principales genes que influyen directamente en la tolerancia al aluminio por piñas resistentes y no resistentes (Cayenne y Tainung No. 17, respectivamente). Para ello, las plantas se cultivaron en una solución hidropónica nutritiva que contenía AlCl3 en concentraciones de 0 y 300 μM en una cámara de crecimiento durante cuatro semanas. Se tomaron muestras de ápices de raíces, lo cual fue seguido por un protocolo metodológico que incluyó extracción de ARN, selección de cebadores, secuenciación y procesamiento de PCR. Finalmente, después del examen de los genes, las expresiones relativas de los mismos para ambos cultivares se determinaron por PCR cuantitativo. Los resultados obtenidos mediante las pruebas de la reacción en cadena de la polimerasa mostraron que las características de resistencia al aluminio de las plantas de piña están regulados principalmente por los genes GAPDH (gliceraldehído-3-fosfato-deshidrogenasa) y FBA (fructosa bifosfato adenosina). Estos resultados pueden proporcionar indicaciones importantes para el estudio del avance de los mecanismos genéticos sobre la resistencia al aluminio en el cultivo de la piña

Evaluation of the Suitability of Three Analysis Methods for Determining Organic Matter Contents in Fertilizers

土壤有機質含量一般被視為土壤肥力的指標，且可籍此評古土壤生產力的高低。有機質肥料的適當施用是最直接且可顯著提高土壤有機貿含量的方法。有機質肥料中有機質含量的測定方法甚多，惟各有其缺點而影響其正確性。本研究之目的在比較並評估三種有機質含量測定法（乾灰化法、濕氧化怯和元素分析法）在測定不同種類的值物性、動物性和腐植酸類肥料的有機質或有機碳含量之適宜性，並比較三種方法之測值間的關係，以建立最適宜的有機質含量瀾定法。結果顯示，雖然乾灰化法的取樣量比濕氧化法和元素分析法多，且由於取樣不均所造成的試驗誤差相對較小，但本試驗以乾灰化法測定非有機質之碳酸鹽肥料時，亦司測得有機質含量(LOI)，是故將乾灰化法所損失之重量視為有機質含量的作汰並不十分正確。試驗結果亦顯示，若在濕氧化法之操作過程中，將液溫維持150℃，繼續加熱五分鐘所測得之可氧化有機碳(OXC (heating))值與由元素分析法所得之全有機碳(TOC)測值極為相近，且可由OXC (heating)值代入TOC=0.995 OXC (heating) + 0.42 (R2=0.97**) 方程式而估算有機質肥料之全有機碳量。本試驗結果亦顯示，值物類、動物類和腐值酸類有機質肥料的LOI/TOC及LOI/OXC (hcating)比並非定值，故以傳統上將Walkey-Black濕氧化法測得之OXC或OXC (hcating)測值乘以定值來估算有機質含量的方式，並無法正確的反映有機質的實際含量。利用元素分析法雖可測得有機質肥料之全有機碳含量，但該法使用的樣品量極少，且因樣品均質性較差，因此，測值變異值較大，且必需有昂貴之元素分析儀的配置，故綜合本試驗的結果，目前國家標準(CNS)所使用的乾灰化法的測值，並不能反映實際有機質肥料的有機質含量，而加熱濕氧化法之OXC (heating)測值與有機質肥料之全有機碳含量極為接近，故以有機碳含量作為有機質肥料之品目標準將比有機質含量有意義。 The content of organic matter in soil can be rearded as an index of soil fertility and also can be used to evaluate the productivity of soil. Therefore, organic fertilizer addition is the most direct and useful practice for increasing soil organic matter contert. Several methods have been used to measure the contents of organic matter in organic fertilizers, but all of them have disadvantages in terms of measurement. The objectives of this study were to compare and evaluate the suitability of three commonly used methods (the dry ash method, wet oxidation method, and elemental analysis method) for determining the contents of organic matter or organic carbon in organic fertilizers, and for developing the most suitable analysis method. Results showed that although the variance of measurement was less for the dry ash method than for the other two methods due to ist larger sample size, the LOI values were also dertermined from fertilizers containing carbonate. Therefore, the assumed loss of weight in organic fertilizers as the dry ash method was used to measure the organic matter content was on correct. Results also showed that the OXC (heating) values, which were determined as the liquid temperature was kept at 150℃ for five minutes, were close to the values of TOC obtained using the elemental analysis method. Therefore, the OXC (heating) values could be converted into TOC values using the equation TOC=0.995 OCX (heating) + 0.42 (R2=0.97**). No constant values of LOI/TOC or LOI/OXC (heating) were found for plant-type, animal-type, or humic acid-type organic fertilizers, so it was critical for common mean that using the values of OXC or OXC (heating) time a constant value to get the conterts of organic matter in organic fertilizers. Although the TOC content could be determined using the elemental analysis method, the variance of measurement tended to be higher because of the sample size is small as well as samples usually are heterogeneous, and expensive equipment was needed in this method. It was concluded that the Loi value measured using the dry ash method, which is suggesded to be the official method by CNS (Chinese National Standards), Could not be regarded as the true content of organic matter in an organic fertilizer, and that the OXC (heating) value determined using the wet oxidation method was close to the content of total organic carbon in organic fertilizer. Therefore, it is better to use the content of total organic carbon as the standard item for organic fertilizers rather than the assumed content of organic matter determined using the dry ash method

Removal of 2,4,6-trichlorophenol from a solution by humic acids repeatedly extracted from a peat soil

Humic acid (HA) is one of the major components of soil organic matter. It strongly affects the sorption behavior of organic and inorganic contaminants in soils. To obtain a better understanding of the interactions of contaminants with HA, a repeated extraction technique has been applied to a peat soil to obtain HA fractions with varying aliphaticity and aromaticity, which were subsequently correlated to the sorption properties of 2,4,6-trichlorophenol (TCP). HA fractions were extracted repeatedly using an alkaline solution and each HA fraction was separated into two portions with an air-drying or re-suspending (denoted as RSHAs) process. Solid-state 13C NMR and elemental analysis demonstrated that the aromaticity and polarity of HAs decreased with extractions. Kinetic results indicated that air-dried HAs exhibited two-step first order sorption behavior with a rapid stage followed by a slower stage. The slower sorption is attributed to the diffusion of 2,4,6-TCP in the condensed aromatic domains of HAs. Conversely, sorption of 2,4,6-TCP on RSHAs was extremely rapid and could not be fitted with any kinetic model. For air-dried HAs the sorption capacity (Koc) was weakly correlated with the chemical compositions of HAs. However, a positive trend between Koc and aromaticity was observed for RSHAs. Compared with the results of air-dried HAs with their counterparts of RSHAs, it is therefore concluded that air-drying may alter the structure of HAs through artificially creating a more condensed domain in HAs. The structural alternation may result in an incorrect interpretation of the relationship between sorption capacity and chemical composition of HAs and a misjudgment of the transport behavior of 2,4,6-TCP in soils and sediments