Estimation of the Effect of Soil Texture on Nitrate-Nitrogen Content in Groundwater Using Optical Remote Sensing

The use of chemical fertilizers in Thailand increased exponentially by more than 100-fold from 1961 to 2004. Intensification of agricultural production causes several potential risks to water supplies, especially nitrate-nitrogen (NO3−-N) pollution. Nitrate is considered a potential pollutant because its excess application can move into streams by runoff and into groundwater by leaching. The nitrate concentration in groundwater increases more than 3-fold times after fertilization and it contaminates groundwater as a result of the application of excess fertilizers for a long time. Soil texture refers to the relative proportion of particles of various sizes in a given soil and it affects the water permeability or percolation rate of a soil. Coarser soils have less retention than finer soils, which in the case of NO3−-N allows it to leach into groundwater faster, so there is positive relationship between the percentage of sands and NO3−-N concentration in groundwater wells. This study aimed to estimate the effect of soil texture on NO3−-N content in groundwater. Optical reflectance data obtained by remote sensing was used in this study. Our hypothesis was that the quantity of nitrogen leached into groundwater through loam was higher than through clay. Nakhon Pathom province, Thailand, was selected as a study area where the terrain is mostly represented by a flat topography. It was found that classified LANDSAT images delineated paddy fields as covering 29.4% of the study area, while sugarcane covered 10.4%, and 60.2% was represented by “others”. The reason for this classified landuse was to determine additional factors, such as vegetation, which might directly affect the quantity of NO3−-N in soil. Ideally, bare soil would be used as a test site, but in fact, no such places were available in Thailand. This led to an indirect method to estimate NO3−-N on various soil textures. Through experimentation, it was found that NO3−-N measured through the loam in sugarcane (I = 0.0054, p < 0.05) was lower than clay represented by paddies (I = 0.0305, p < 0.05). This had a significant negative impact on the assumption. According to the research and local statistical data, farmers have always applied an excess quantity of fertilizer on paddy fields. This is the main reason for the higher quantity of NO3−-N found in clay than loam in this study. This case might be an exceptional study in terms of quantity of fertilizers applied to agricultural fields

Assessment of Influence and Inter-Relationships of Soil Properties in Irrigated Rice Fields of Bangladesh by GIS and Factor Analysis

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 9 (2007): Assessment of Influence and Inter-Relationships of Soil Properties in Irrigated Rice Fields of Bangladesh by GIS and Factor Analysis. Manuscript LW 07 022. Vol. IX. November, 2007

Toxic Metals (Pb and Cd) and Their Respective Antagonists (Ca and Zn) in Infant Formulas and Milk Marketed in Brasilia, Brazil

In non-ideal scenarios involving partial or non-breastfeeding, cow’s milk-based dairy products are mainstream in infant feeding. Therefore, it is important to study the concentrations of potentially neurotoxic contaminants (Pb and Cd) and their respective counteracting elements (Ca and Zn) in infant dairy products. Fifty-five brands of infant formulas and milk sold in Brasilia, Brazil were analyzed. The dairy products came from areas in the central-west (26%), southeast (29%) and south of Brazil (36%) extending as far as Argentina (7%) and the Netherlands (2%). For toxic Pb and Cd, median concentrations in powdered samples were 0.109 mg/kg and 0.033 mg/kg, respectively; in fluid samples median Pb concentration was 0.084 mg/kg, but median Cd concentration was below the limit of detection and overall values were below reference safety levels. However, 62% of these samples presented higher Pb concentration values than those established by FAO/WHO. Although the inverse correlation between Cd and Zn (Spearman r = −0.116; P = 0.590) was not statistically significant, the positive correlation between Ca and Pb was (Spearman r = 0.619; P < 0.0001). Additionally, there was a significant correlation between Pb and Cd. Furthermore, the study also revealed that provision of the essential trace element Zn in infant formulas can provide adequate amounts of the recommended daily requirements. Infant formulas and milk sold for consumption by infants and children can be an efficient tool to monitor neurotoxic metal risk exposure among young children

The potential of an Fe waste by-product as an Fe fertilizer in alkaline soil

Typescript (photocopy).An Fe dust waste accumulates as a by-product from the steel industry and poses a disposal problem. Since the waste contains approximately 43% Fe, 5.4% Zn, and 1.9% Mn, it shows potential for recycling as a plant food. Therefore, laboratory and greenhouse experiments were conducted to evaluate this Fe waste material as a possible source of agricultural Fe fertilizer. In a laboratory experiment, selective dissolution and fractionation were used to determine Fe dust solubility and to partition total Fe into solubility classes. The release of Fe was in the following order: water < DTPA < 0.25 M HCl < 0.25 M H(,2)SO(,4) < dithionite-citrate-bicarbonate < < acid NH(,4)-oxalate. The x-ray diffraction patterns and transmission electron micrographs of Fe dust and residue remaining after each extraction revealed the presence of magnetite as a major component of the material. This water insoluble material was treated with H(,2)SO(,4) to increase Fe solubility and enhance its value as a fertilizer. Water soluble and DTPA extractable Fe were directly proportional to the amount of acid used. The effect of particle size on Fe solubility indicated that the smaller particles within the Fe dust size range did not increase Fe solubility. An incubation study of Fe waste (with and without H(,2)SO(,4)) in a calcareous Fe deficient soil indicated that available soil Fe decreased sharply with soil reaction time. In a greenhouse experiment, Fe waste material was evaluated to alleviate Fe chlorosis of sorghum (Fe efficient and inefficient cultivars) grown in Fe deficient calcareous soil. The Fe waste (dust and pellet) with and without acid at a ratio of 1:2 (Fe/H(,2)SO(,4)), was mixed with the soil at 3 rates before planting. Vegetative growth and dry matter yields clearly showed superior performance of acidified Fe materials over nonacidified Fe dust or pellet. Extractable soil Fe increased linearly with rate of acidified Fe materials. Likewise, Fe concentration in plants increased proportionally to available soil Fe.A comparison of a Fe waste material with other Fe sources (FeSO(,4) and Fe EDDHA) at various rates to prevent Fe chlorosis was studied. Similar alleviation resulted from Fe dust 1000 ppm, FeSO(,4) 100 ppm, and Fe EDDHA 10 ppm. Iron pellet failed to correct Fe chlorosis. Soil incorporation of plant residue (chopped sorghum stover) as a carrier for Fe sources produced greater dry matter yield in all treatments. Available soil Fe increased with added plant residue and also with rate of Fe applied

The potential of an Fe waste by-product as an Fe fertilizer in alkaline soil

Typescript (photocopy).An Fe dust waste accumulates as a by-product from the steel industry and poses a disposal problem. Since the waste contains approximately 43% Fe, 5.4% Zn, and 1.9% Mn, it shows potential for recycling as a plant food. Therefore, laboratory and greenhouse experiments were conducted to evaluate this Fe waste material as a possible source of agricultural Fe fertilizer. In a laboratory experiment, selective dissolution and fractionation were used to determine Fe dust solubility and to partition total Fe into solubility classes. The release of Fe was in the following order: water < DTPA < 0.25 M HCl < 0.25 M H(,2)SO(,4) < dithionite-citrate-bicarbonate < < acid NH(,4)-oxalate. The x-ray diffraction patterns and transmission electron micrographs of Fe dust and residue remaining after each extraction revealed the presence of magnetite as a major component of the material. This water insoluble material was treated with H(,2)SO(,4) to increase Fe solubility and enhance its value as a fertilizer. Water soluble and DTPA extractable Fe were directly proportional to the amount of acid used. The effect of particle size on Fe solubility indicated that the smaller particles within the Fe dust size range did not increase Fe solubility. An incubation study of Fe waste (with and without H(,2)SO(,4)) in a calcareous Fe deficient soil indicated that available soil Fe decreased sharply with soil reaction time. In a greenhouse experiment, Fe waste material was evaluated to alleviate Fe chlorosis of sorghum (Fe efficient and inefficient cultivars) grown in Fe deficient calcareous soil. The Fe waste (dust and pellet) with and without acid at a ratio of 1:2 (Fe/H(,2)SO(,4)), was mixed with the soil at 3 rates before planting. Vegetative growth and dry matter yields clearly showed superior performance of acidified Fe materials over nonacidified Fe dust or pellet. Extractable soil Fe increased linearly with rate of acidified Fe materials. Likewise, Fe concentration in plants increased proportionally to available soil Fe.A comparison of a Fe waste material with other Fe sources (FeSO(,4) and Fe EDDHA) at various rates to prevent Fe chlorosis was studied. Similar alleviation resulted from Fe dust 1000 ppm, FeSO(,4) 100 ppm, and Fe EDDHA 10 ppm. Iron pellet failed to correct Fe chlorosis. Soil incorporation of plant residue (chopped sorghum stover) as a carrier for Fe sources produced greater dry matter yield in all treatments. Available soil Fe increased with added plant residue and also with rate of Fe applied

Iron deficiency in peanut on black calcareous soils

Black calcareous soils of Thailand (Rendzinas or Calciustolls) occupy 500 000 ha and are located mostly on the highlands of central and northern areas of the country. These soils are considered quite fertile, but leaf chlorosis resembling iron deficiency occurs quite commonly in peanuts, although patchy in distribution

Toxicity of Mercury to Growth and Survival of Seabass Larvae, Lates calcarifer and the Modifying Effects of Salinity

ABSTRACT: Short-term chronic toxicity tests were conducted to investigate the adverse effects of mercury (Hg) on growth (measured as dry weight) and survival of seabass larvae, Lates calcarifer, and the modifying effects of salinity. Seven-day static-renewal tests were conducted at four salinities: 2, 10, 20 and 30 psu. The experiments were repeated three times for each salinity. Results indicated that seabass larvae were very sensitive to low concentrations of Hg. Based on the actual measured Hg concentrations, the mean NOEC, LOEC and LC 50 values for survival were 30.8, 52.5 and 46.2 µg L -1 , respectively, while the mean NOEC, LOEC, IC 25 and IC 50 values for growth were 5.2, 12.6, 8.5 and 19.2 µg L -1 , respectively. Salinity did not have any significant effects on the toxicity of Hg on survival and growth of seabass larvae. One possible explanation is that Hg preferentially forms very strong complexes with sulfhydryl groups (-SH) in proteins rather than with chloride

Iron-deficiency specifically limits nodule development in peanut inoculated with Bradyrhizobium sp

Severely iron‐deficient peanuts (Arachis hypogaaea L.) grown on calcareous soils in central Thailand failed to nodulate until given foliar iron applications. Glasshouse experiments were conducted on two cultivars (Tainan 9 and Robut 33–1) to identify which stage of the nodule symbiosis was most sensitive to iron‐deficiency. Iron‐deficiency did not limit growth of soil or rhizosphere populations of peanut liradyrhizobium. Similar numbers of root nodule initials formed in the roots of both control and iron‐sprayed plants, showing that iron‐deficiency did not directly affect root infection and nodule initiation. Plants sprayed with iron produced greater numbers of excisable nodules and carried a greater nodule mass than untreated plants. Five days after iron application, nodules on sprayed plants of CV. Tainan 9 contained 200–fold higher bacteroid numbers per unit weight and 14–fold higher concentrations of leghaemoglobain. The onset of nitrogenase activity was also delayed by iron deficiency in both cultivars. Tainan 9 appeared more sensitive to iron‐deficiency than Robut 33‐1 in terms of nodule mass produced, but both cultivars showed the same effect of iron‐deficiency on nitrogenase activity per plant. It is concluded that the failure of the infecting rhizobia to obtain adequate amounts of iron from the plant results in arrested nodule development and a failure of nitrogen fixation