Influence of barley variety mixtures on severity of scald and net blotch and on yield *

Two susceptible barley cultivars and two moderately resistant advanced breeding lines were grown as pure stands and as the 11 possible equi-proportional mixtures over three field seasons, in the presence of scald and net blotch. Plots were either inoculated with infested straw, or non-inoculated and sprayed with fungicide. On average, the variety mixtures restricted leaf disease development by 12%. However, mixtures of either or both susceptible cultivar/s with the moderately resistant line 1861018 restricted disease severity by 20-32%. Generally, the mixtures did not increase yield relative to the mean of the pure stands. However, in the year of highest disease severity, yield was increased by 7% owing to mixing in the inoculated plots. In addition, one mixture consistently increased yield (mean of 4%) and one mixture had consistently lower yields (mean of 6%)) over years and inoculation treatments. Thus, careful evaluation is required in this environment and with these genotypes in order to identify mixtures with positive effects on disease control and yield.     

The interaction of hydrazine hydrate with humic acid preparations at pH 4

Sorption isotherms were obtained by a continuous-flow method for the interaction of hydrazine hydrate with freeze-dried hydrogen-, aluminium- and calcium-exchanged humic acid preparations in aqueous suspensions at pH 4. The application of the continuous-flow method is outlined and the fit of the isotherms to three sorption equations is examined. Microcalorimetry was used to measure directly the differential enthalpies of reaction as functions of sorptive concentrations. Exchange by hydrazinium ions of the exchangeable cations on the humates, chemisorption by interaction of hydrazine with humate carbonyl groups, and non-specific sorption involving weakly- and strongly-held hydrazinium ions and hydrazine molecules are shown to be the major sorption processes in these systems. The relative importance of each of these processes for the different hydrazine/humate systems is discussed, and the influence of the exchangeable cation on humate reactivity is considered.     

Attacks of Neodiprion sertifer on Pinus contorta1

Neodiprion sertifer, the European pine sawfly, has in the past attacked mainly Pinus sylvestris. Afforestation of areas in northern Scotland with P. contorta in the early 1960s and subsequently has led to widespread outbreaks of N. sertifer on this species, attacks being most severe on trees 5 to 12 years old. The most serious damage is removal of the 1-year and older needles. Complete loss of this foliage often occurs at the peak of an outbreak. Also, at high population densities, larvae may consume patches of bark, leading to weakening and stem breakage in high winds. Field studies comparing protected (undefoliated) randomized plots of P. contorta with defoliated plots in Shin Forest (Sutherland) were carried out over the 1982–1983 growing seasons. Comparison of leaf/sapwood basal areas in undefoliated and defoliated plots indicated losses of up to 27% of total leaf area, both removal of old foliage by larvae and a reduction in current-year foliage being involved. Further, there were significant reductions in sapwood basal area and height increment between control plots and some of the defoliated plots. The impact of such defoliation is to prolong the rotation by approximately 2 years.     

Some effect fluid-sowing, pre-germination, irrigation and soil covering on the establishment and growth of seedlings of white clover slot-seeded into permanent pasture

Seeds of white clover ( Trifolium repens ) were sown alone or in fluid, or pre-germinated in fluid on to the soil surface of slots cut in an old Agrostis/Festuca sward. Seeds were left uncovered or covered with a thin layer of soil and irrigated from the outset or after 14 days delay.
With irrigation from the outset, seedlings established soonest from pre-germinated seeds but final percentage establishment ranged only from 50 to 63% for the three states of seed. With delayed Irrigation, however, few pre-germinated s1 survived and although germination of dry seed was delayed, final percentage establishment was unaffected. Soil covering increased establishment slightly. The number of leaves per seedling was greatest with pre-germination and early irrigation and least with pre-germination and delayed irrigation. Delayed irrigation also decreased the number of leaves per seedling for seedlings grown from dry seed.
The effects of early irrigation persisted so that at 84 days it significantly increased total yield of clover from all three states of seed, on average threefold, but much more from pre-germinated than from dry seed. Soil covering greatly increased yield, especially where irrigation had been applied from the outset. The interaction of early irrigation and soil covering was even more pronounced for stolon weights, and stolon growth of Individual seedlings appeared to benefit more from soil covering than from early irrigation.
The results showed the importance of early seedling emergence, but no advantages of fluid sowing per se. They also indicated large overall beneficial effects of early irrigation and its additive interaction with soil covering.     

The Mode of Infection of Lodgepole Pine by Crumenula sororia Karst. and the Susceptibility of Different Provenances to Attack

Experimental inoculations of C. sororia on un-wounded Lodgepolepine produced successful infections after 9 months in 25 percent of cases, compared with 40–60 per cent where woundswere inoculated. After 16 months, however, these differencesdisappeared. The virulence of different isolates of C. sororiadiffered. Current year's shoots were more resistant to infectionthan 1-year-old shoots. Resistance was generally not a functionof broad geographical origin, save in the southern coastal types.Some provenances were highly significantly more susceptiblethan other closely adjacent ones: Burns Lake and Salmon Armwere highly susceptible, whereas Fort St. James and Mount Idaprovenances were respectively resistant. These observationsagree closely with field survey data, thus validating the useof young plants to indicate resistance of older crops to infection.     

SOME PHYSICO-CHEMICAL INTERACTIONS OF PARAQUAT WITH SOIL ORGANIC MATERIALS AND MODEL COMPOUNDS I. EFFECTS OF TEMPERATURE, TIME AND ADSORBATE DEGRADATION ON ARAQUAT ADSORPTION

Summary. Some investigations were carried out on the adsorption of paraquat by a range of organic materials which included an organic soil, various humic fractions from that soil, model polymers prepared by the oxidative coupling of benzoquinone, the ion exchange resins Zeo-Karb 216 and 226, and Amberlite XAD-2. The time required for the adsorption process to reach equilibrium ranged from about 3 h (for the soil and humic preparations) to about 48 h (for the more highly cross-linked materials). Adsorption by Amberlite XAD-2, a cross-linked polystyrene resin, was very small, presumably because it lacked ion-exchange sites.
The results suggested that particle diffusion control was operating and the different equilibrium times reflected different degrees of molecular complexity within the adsorbents.
Temperature, within the 20°–70°C range, did not affect the adsorption equilibrium, and this is indirect evidence for ion exchange as the primary adsorption mechanism. No evidence was found for decomposition of paraquat in the adsorption systems studied.
Quelques interactions physico-chimiques du paraquat avec des inatéaux de sol organique et des composes modéles I. Effets de la température, du temps et de la dégradation sur I'adsorption du paraquat