Effect of liming on extractable Zn, Cu, Fe and Mn in selected Scottish soils

Ten naturally acidic Scottish soils have been limed with CaCO₃ at 0,0.25, 0.50, 0.75, 1.00 and 1.25 times the recommended lime requirement, and then subjected to three cycles of alternate wetting to field capacity at 20°C for 1 month and drying for 1 month. The Zn, Cu, Fe and Mn extracted by DTPA solution, both at pH 7.3 and also after adjustment to match the final soil pH, were measured by flame AAS. The same elements were determined in ammonium acetate extracts, for extractants buffered at pH 4.8, pH 7.0 or at the final soil pH. The effect of extractant pH upon the amounts of trace elements removed is discussed for the two extractants, with particular reference to Zn. The influence of soil pH upon the amounts of trace elements extracted is also considered. There appears to be a distinct relationship between rate of decrease of DTPA-extractable Fe with increasing soil pH and the effect of pH upon DTPA-extractable Zn, high rates of decrease of extractable Fe being associated with a more continuous decline in extractable Zn with increasing soil pH. Possible reasons for this relationship are discussed, in the light of an experiment conducted to examine the effect of Fe and A1 on loss of Zn from solution at high pH. DTPA-extractable Cu varied little with increasing soil pH.     

Combination and rotation of bacterial antagonists to control powdery mildew on pumpkin

Journal of Plant Diseases and Protection - Mixtures of micro-organisms may lead to more effective control of plant pathogens than biocontrol with single species, but little data exists on the...     

Sodium bicarbonate as an extractant for soil phosphate III. Effects of the buffering capacity of a soil for phosphate

An index of the buffering capacity for phosphate of a group of soils was obtained by measuring adsorption of phosphate from dilute solutions of calcium chloride. The effect of buffering capacity on the amount of phosphate initially displaced by solutions of sodium bicarbonate and on the amount of secondary adsorption from bicarbonate was then studied. These two effects were separated using a regression procedure in which the soil: solution ratio was the independent variable.As buffering capacity increased the amount of phosphorus initially displaced decreased and the amount of secondary adsorption increased. Both these changes resulted in a decrease in the amount of phosphate in the extract. The effect of buffering capacity was greater with the Olsen method (soil : solution ratio 1 : 20; 30 min) than with the Colwell method (soil : solution ratio 1 : 100; 16 h). The relation between phosphorus extracted and buffering capacity was of a similar shape to that between effectiveness of fertilizer and buffering capacity. However, the first relation depends on the conditions of extraction and the second on the kind of plant grown and on the conditions of growth. Hence the two relations do not necessarily coincide.The effect of buffering capacity on the proportion of added phosphate initially displaced from the soil became more marked as the period of incubation prior to extraction was increased. Bicarbonate soil tests would therefore indicate that, on soils of low buffering capacity, the decrease with time in availability of applied phosphate would be smaller than on soils of high buffering capacity. This effect differs from that observed with plants.     

A metalloprotease disintegrin that controls cell migration in Caenorhabditis elegans

In Caenorhabditis elegans, the gonad acquires two U-shaped arms by the directed migration of its distal tip cells (DTCs) along the body wall basement membranes. Correct migration of DTCs requires the mig-17 gene, which encodes a member of the metalloprotease-disintegrin protein family. The MIG-17 protein is secreted from muscle cells of the body wall and localizes in the basement membranes of gonad. This localization is dependent on the disintegrin-like domain of MIG-17 and its catalytic activity. These results suggest that the MIG-17 metalloprotease directs migration of DTCs by remodeling the basement membrane.     

Dietary zinc concentration and lipopolysaccharide injection affect circulating trace minerals,acute phase protein response,and behavior as evaluated by an ear-tag–based accelerometer in beef steers

To assess plasma trace mineral (TM) concentrations, the acute phase protein response, and behavior in response to a lipopolysaccharide (LPS) challenge, 96 Angus cross steers (average initial body weight [BW]: 285 ± 14.4 kg) were sorted into two groups by BW (heavy and light; n = 48/group), fitted with an ear-tag–based accelerometer (CowManager SensOor; Agis, Harmelen, Netherlands), and stagger started 14 d apart. Consecutive day BW was recorded to start the 24-d trial (days −1 and 0). Dietary treatments began on day 0: common diet with either 30 (Zn30) or 100 (Zn100) mg supplemental Zn/kg DM (ZnSO₄). On day 17, steers received one of the following injection treatments intravenously to complete the 2 × 3 factorial: 1) SALINE (~2–3 mL of physiological saline), 2) LOWLPS: 0.25 µg LPS/kg BW, or 3) HIGHLPS: 0.375 µg LPS/kg BW. Blood, rectal temperature (RT), and BW were recorded on day 16 (−24 h relative to injection), and BW was used to assign injection treatment. Approximately 6, 24 (day 18), and 48 (day 19) h after treatment, BW, RT, and blood were collected, and final BW recorded on day 24. Data were analyzed in Proc Mixed of SAS with fixed effects of diet, injection, diet × injection; for BW, RT, dry matter intake (DMI), plasma TM, and haptoglobin-repeated measures analysis were used to evaluate effects over time. Area under the curve analysis determined by GraphPad Prism was used for analysis of accelerometer data. Body weight was unaffected by diet or injection (P ≥ 0.16), but there was an injection × time effect for DMI and RT (P < 0.05), where DMI decreased in both LPS treatments on day 16, but recovered by day 17, and RT was increased in LPS treatments 6 h post-injection. Steers receiving LPS spent less time highly active and eating than SALINE (P < 0.01). Steers in HIGHLPS spent lesser time ruminating, followed by LOWLPS and then SALINE (P < 0.001). An injection × time effect (P < 0.001) for plasma Zn showed decreased concentrations within 6 h of injection and remained decreased through 24 h before recovering by 48 h. A tendency for a diet × time effect (P = 0.06) on plasma Zn suggests plasma Zn repletion occurred at a greater rate in Zn100 compared to Zn30. These results suggest that increased supplemental Zn may alter the rate of recovery of Zn status from an acute inflammatory event. Additionally, ear-tag–based accelerometers used in this study were effective at detecting sickness behavior in feedlot steers, and rumination may be more sensitive than other variables.     

The performance of a thermometer screen on an automatic weather station

The performance of a Didcot-type thermometer screen on an Automatic Weather Station and a conventional Stevenson screen were compared, both with each other and against an aspirated Assmann psychrometer. Maximum temperature in the Didcot screen exceeded the conventional screen maximum by up to 1 K on calm, sunny days, and Didcot minimum temperatures were as much as 1.5 K less than the screen minima on still, clear nights; mean temperature discrepancies between screens were + 0.3 and − 0.4 K for maxima and minima, respectively. The apparent psychrometric constant for the Didcot screen was 1.0 mbar K⁻¹ which increased to 1.2 mbar K⁻¹ when u < 2 m s⁻¹ in contrast to the value of 0.799 mbar K⁻¹ frequently used for the Stevenson screen.     

Use of dihaploid potatoes in breeding for ground frost resistance

Ground frost resistance is important for the growing of early potatoes and of othervarieties on soils which are prone to suffer from ground frosts. Resistance has beenfound, among others, in the primitive diploid cultivated potato species S. ajanhuiri.The clones of this species which are included in the Wageningen Potato Collection(WAC) were not crossable to ordinary varieties of the species S. tuberosum. However,it was shown to be possible to cross S. ajanhuiri with a dihaploid form of S. tuberosum.Amphidiploid plants were obtained after colchicine treatment. These plants werefertile when crossed with ordinary varieties. Some of the hybrids possess a certainfrost resistance. Backcrosses will be necessary to obtain varieties with good consump-tion qualities.