Inactivation of Escherichia coli in soil by solarization

Contamination of agricultural soil by fecal pathogenic bacteria poses a potential risk of infection to humans. For the biosafety control of field soil, soil solarization in an upland field was examined to determine the efficiency of solarization on the inactivation of Escherichia coli inoculated into soil as a model microorganism for human pathogenic bacteria. Soil solarization, carried out by sprinkling water and covering the soil surface with thin plastic sheets, greatly increased the soil temperature. The daily average temperature of the solarized soil was 4–10°C higher than that of the non-solarized soil and fluctuated between 31 and 38°C. The daily highest temperature reached more than 40°C for 8 days in total in the solarized soil during the second and third weeks of the experiment. Escherichia coli in the solarized soil became undetectable (< 0.08 c.f.u. g⁻¹ dry soil) within 4 weeks as a result, whereas E. coli survived for more than 6 weeks in the non-solarized soil. Soil solarization, however, had little influence on the total direct count and total viable count of bacteria in the soil. These results indicate that soil solarization would be useful for the biosafety control of soil contaminated by human pathogens via immature compost or animal feces.     

Deficiency of N,P, K,Ca, Mg,or Fe Mineral Nutrients in Narcissus cv. “Garden Giant”

Narcissus cv. “Garden Giant” bulbs were grown in N, P, K, Ca, Mg, or Fe-deficient solutions and compared with bulbs grown in the control solution containing all these nutrients. Plants were sampled at 4 stages: (I) at planting, (II) at sprouting, (III) after flower senescence and/or after visible deficiency symptoms developed, and (IV) at lifting. Observation of visible deficiency symptoms showed that leaves of narcissus displayed chlorosis in the —N, —Mg, and —Fe treatments, while roots were most susceptible to Ca-deficient conditions. Root tips in the —Ca treatment showed brown in followed by root rot. In the —N treatment, shoot growth was markedly retarded and leaves were small and yellow. On the other hand, visible deficiency symptoms were not evident in the —P treatment except for early senescence. K deficiency symptoms were also not evident. Narcissus flowers were not affected by the mineral deficiencies and mineral contents in full-bloom flowers were not different between samples.

In the control plants, there was a large accumulation of N in the roots at sprouting and the content decreased thereafter. Large amounts of K accumulated in roots more than in any other organs. On the other hand the Ca content was high in the tunic and Ca in the scales was hardly mobilized thoughout the growth period. A large proportion of each element eventually accumulated in new inner scales whereas only a small fraction in the old outer scales. The -N, -Ca, and -Mg treatments severely depressed dry matter accumulation, unlike the -P, -K, and -Fe treatments. The -N treatment did not affect the concentration of other minerals, but the -P treatment tended to decrease N, K, Ca, and Mg concentrations. On the other hand, the -K treatment increased Ca and Mg concentrations. -Ca caused an increase in Mg concentration and -Mg raised Ca concentration. These results may be due to compensation effects of cation absorption for the maintenance of the cation/anion balance.     

Improvement of application method of liquid fertilizer with irrigation water for uniform topdressing and change in nitrogen concentration of flooded water after application

(pp. 811–816)
The application method of liquid fertilizer with irrigation water was tested in large scale paddy fields using a newly developed fertilizer supplier which can make a supplying rate of liquid fertilizer constant. Uniformity of fertilization, change in the nitrogen concentration of flooded water and absorption of applied nitrogen by paddy rice were examined. High uniformity of fertilization was achieved with this method as compared with a conventional broadcast application of granular fertilizer, or an inflow fertilization of granule-like fertilizer with irrigation water.
When urea was applied as liquid fertilizer, the fertilizer-N disappeared quickly from ponding water under shallow conditions of ponding water depth. In the case of the same depth of ponding water, the rate of reduction was large under conditions of large permeability of water.
The nitrogen utilization rates of urea and ammonium sulfate labeled with ¹⁵N were not related to the depth of ponding water at the time of fertilization. When ammonium sulfate was supplied the nitrogen utilization rate was around 50% regardless of fertilization conditions however, the urea-N utilization rate fell to 40% or less at a permeability of ponding water of 0.8 cm day⁻¹ or less, while it increased to 50% equivalent to ammonium sulfate, at 0.8 cm day⁻¹ or more permeability.     

Properties of Microbial Biomass in Acid Soils and Their Turnover

The soil microbial biomass is important such as pool of plant nutrients and is also driving force of the cycling of C, N, P and S in soil. However, the microbial biomass in acid soil has not been fully investigated due to the limitation of methods, i.e. chloroform-fumigation incubation or substrate-induced respiration because of decreased basal mineralization in chloroform-fumigated soil under acid conditions. This paper reviews improvement and application of these methods and vertical distribution of microbial biomass in two kinds of acid soils; namely, Andisols as dominant upland soils in Japan and tropical peat soils as potentially important lowland soils for agriculture, and also discuss on C and N turnover of microbial biomass in Andisols. Microbial succession in acid soil has also not been investigated so much, but, some studies in another important acid soil, i.e. acid sulfate soil, were also reviewed briefly.     

Mineral composition in the holdfast of three brown algae of the genus Laminaria

SUMMARY: The mineral (Na, K, Ca, Mg, Fe, Mn and Zn) contents in the holdfast of three brown algae of the genus Laminaria were determined to compare with those in frond and stipe. The wild and cultivated kelps of Laminaria japonica , L. ochotensis , and L. diabolica were used as samples. The K content was markedly high (11.76–14.91 g/100 g dry weight) in the holdfast of cultivated L. japonica; the K/Na ratio (3.88–5.18) of the holdfast was greater than those of frond and stipe as well as the reported values of frond (1.0–2.2). The content of Ca in the holdfasts of these three species was also higher than those in frond and stipe. The content of Mn showed the same tendency. This is the first report showing that the holdfast of L. japonica and L. diabolica is rich in minerals, especially K.     

Effect of growth and parturition on hair cortisol in Holstein cattle

The effect of growth and parturition on hair cortisol concentrations of cattle was investigated. Plasma, saliva, and hair (black and white from the shoulders and hip) samples were collected from calves at 6 and 24 weeks old and from dairy cattle at the dry (1 and 2 months prepartum) and lactation (10, 50, 150, and 250 days postpartum) periods. Plasma and saliva cortisol concentrations were lower in 24-week-old calves than those of 6-week-old calves, and hair cortisol concentrations decreased regardless of color and position. In 6-week-old calves, hair cortisol concentrations differed between sampling positions, but this difference was not observed in 24-week-old calves. Plasma and saliva cortisol concentrations increased before parturition until 10 days postpartum then decreased until 50 days postpartum. The same trend was observed in the cortisol concentrations of white hair. Contrarily, cortisol concentrations in black hair remained unchanged and was lower than that in white hair. Hair cortisol concentration can vary greatly depending on the location on the body, hair color, cattle age, or parturition. When this method is used, all of the above factors must be considered.     

The production economics of freshwater prawn (Macrobrachium rosenbergii) farming in Hawaii

Detailed cost-return of freshwater prawn farming in Hawaii is estimated for farms ranging in size from a minimum of 1 acre to a maximum of 100 acres. Major factors affecting cost and revenue are discussed. Freshwater prawn farming in Hawaii is profitable at the existing average annual production of 3 000 pounds/acre and at the existing average farm price of $3.00/pound for farms that are 10 acres or larger. Smaller farms are profitable only when operated as a family venture.