Gaseous diffusion through peat

Relative gas diffusivity (D/D₀) was measured in peat cores equilibrated to set moisture tensions between zero and - l0 kPa, using the radioactive gas ⁸⁵Kr. A relationship between relative diffusivity and the air filled porosity was obtained, which showed lower values of D/D₀ at air-filled porosities above about 0.13m³m⁻³, and higher values at porosities below about 0.10m³m⁻³ than some of those found in the literature for mineral soils. The likely effects of shrinkage behaviour on drying in the field, on the relationship between D/D₀ and air-filled porosity, are discussed.     

DEGRADATION OF BROMOXYNIL IN REGINA HEAVY CLAY*

A spectrophotometric method was developed to detect bromoxynil in Regina heavy clay, and the breakdown under different temperature and moisture conditions was studied. At rates equivalent to 14 kg/ha, over 50% of the applied bromoxynil was degraded in 2 weeks at 25°C and at moisture levels in excess of the wilting point. Losses at 18°C were slightly slower. Little breakdown occurred in sterile soil, indicating that microbial degradation could be an important factor contributing to bromoxynil breakdown under field conditions. Paper and thin-layer chromatographic techniques were used to isolate and identify soil degradation products. In addition to the parent compound small amounts of 3,5-dibromo-4-hydroxybenzamide and 3,5-dibromo-4-hydroxybenzoic acid were detected.     

The estimation of mineralization, immobilization and nitrification in nitrogen-15 field experiments using computer simulation

A combination of mathematical analysis and computer simulation, using parameters readily measured in a nitrogen-15 field experiment, is employed to determine rates of mineralization, immobilization and nitrification under a growing crop. The procedure also yields the proportion of crop nitrogen uptake occurring as ammonium and nitrate.
When applied to -results from grass lysimeters receiving 250 or 900 kg N ha^–1 a^–1 as ammonium nitrate, the analysis suggested that at 250 kgN ha^–1 a^–1 64–66% of crop nitrogen uptake was as ammonium; at 900 kg N ha^–1 a^–1 the figure was 43–49%. Nitrification at 250kgNha^–1 was only 13–19kgN ha^–1 over 160d while at 900 kg N ha^–1 between 191 and 232 kg N ha^–1 were nitrified.
The results suggested that the apparent inhibition of nitrification in grassland soils may simply reflect poor substrate competition by nitrifying bacteria. Finally, there was a suggestion that mineralization/immobilization was lower at the high fertilizer rate.     

Carbon and water footprints of major crop production in India

Scarcity of water and emission of greenhouse gases (GHGs) are the two key environmental issues affecting crop production in India.Reducing the carbon footprint (CF) and water footprint (WF) of crop production can help to mitigate the environmental hazards that stem from GHG emissions and water scarcity.The CFs and WFs of three major cereal crops,rice,wheat,and maize,were estimated for the year 2014 under the environmental conditions in India,based on national statistics and other data sources.To...     

Analytical models of weed biocontrol with sterilizing fungi: the consequences of differences in weed and pathogen life-histories

A model of the population dynamics of healthy weed plants, weed seeds in the soil, pathogen-infected weed plants and pathogen spores in the soil, was devised to investigate interactions that are important for the success of biocontrol with pathogens that prevent seed set. Three particular features of the host-pathogen interaction were examined in detail: the form of the density dependent relationship which determined seed and spore production, the host life stage at which infection could occur, and the relative competitive abilities of healthy and infected host plants. It was found that, when both weed and pathogen coexist, the equilibrium abundance of the weed in the presence of the pathogen was independent of the form of the relationship between plant density and seed or spore production. However, the form of this relationship did affect estimated equilibrium densities in the absence of biocontrol, and also affected the parametrizations under which both host and pathogen could coexist. Parameters derived from experiments with isolated host plants may therefore be sufficient to assess the biocontrol potential of new pathogens along with knowledge of densities achievable when the weed is uncontrolled. The form of the relationship used to control seed and spore production also had a marked influence on the range of parameter values over which the pathogen could persist. Other control measures were represented by changes to appropriate parameter values, e.g. weeding was represented by a change in weed death rate. With one exception, the use of additional control measures was not antagonistic to biocontrol. Often, however, the combined effect was less than additive, and the existence of synergy (where the combined effects are more than additive) was critically dependent on the form of the relationship of the rate of seed production per plant with density and the efficiency of the other control measures.     

Changes in psychological test performances of brain-operated schizophrenics after 8 years

Long-term effects of topectomy showed statistically significant losses not present shortly after psychosurgery in eight of 14 psychological test measures. Site of operation, length of postoperative interval, age, and nature of the measure were factors determining the effects of brain damage.     

Effects of organic and inorganic calcium compounds on soil-solution pH and aluminium concentration

The reactions of two organic (citrate and fulvate) and two inorganic (chloride and phosphogypsum) calcium compounds were studied during leaching of columns of unsaturated acidic soil. The potential of these compounds to decrease the aluminium concentration in the soil solution and remove exchangeable aluminium, and their effects on soil acidity are described. The calcium citrate solution increased the soil solution pH from 5 to a maximum value of 7 in the upper portion of the column. In contrast, the fulvate, calcium chloride and phosphogypsum solutions had little effect on soil-solution pH. Treatment with calcium citrate, or fulvate solution that contained 51 mm Na, removed most of the exchangeable aluminium from the column. The cation exchange sites in the upper portion of the column were saturated with calcium, and the cation exchange capacity of the soil was increased from 35 to c. 80 mmol_c kg^?1 in the calcium citrate treatment. Leachate from this treatment contained low (< 2 mm ) calcium concentrations and high aluminium concentrations. In contrast, the above changes were not shown by the calcium chloride and phosphogypsum treatments. In these treatments the calcium concentration in the leachate was equal to that in the inflowing solution, which indicated that calcium was transported through the entire column. These results suggest that calcium alone was ineffective in displacing aluminium from the cation exchange sites and a strong complexing agent such as citrate or fulvate is needed to mobilize the exchangeable aluminium.     

An approach to quantifying various types of spontaneous activity

The output of an activity-measuring device is fed into low- and high-gain cumulative recorder channels which are reset to zero after different time periods. The records, inscribed at various paper speeds, are easily quantified. The tracing patterns can be identified with specific activities of undisturbed animals. The activities are monitored by means of closed-circuit television.