Establishing leys

Newly established leys, containing almost 100% of improved grass and legume varieties, constitute the most produchve form of grassland and so it is appropriate to commence this chapter with a section on their estabhshment. 

The following refer to the various prachces associated with sowing grass 

Leys are normally sown at this time of year and provided satisfactory establishment is achieved it ensures top yields in the following full harvest year. There is usually some rain at this time, heavy dews have started again, and the soil is warm. When clovers are included in the seed mixture, sowing in August is preferred before the onset of frosts. Whether earlier sowing is possible depends on when the preceding crop in the field is harvested. Winter barley is the ideal crop to follow. Sowing later than September is not advised and can lead to poor establishment. 

Reference has already been made (Section 8.6.2) to the cultivation necessary for preparing the right type of seedbed for grass seeds. It must be re-emphasised that grass and clover seeds are small, and should be sown shallow, and that a fine, firm seedbed is necessary. With ample moisture the seed can be broadcast. This should be on to a ribbed-rolled surface, so that the seeds fall into the small furrows made by the roller. Most fertiliser distributors can be used for broadcasting seeds, and seeds and fertihser are sometimes sown together. Seeds may then be covered with a light harrow or chain harrow or simply rolled in. 

Another useful teehnique is to take the cover erop of cereals for wholectop cereal silage several weeks before the crop is ripe for eombining. An alternative whieh has been used in recent years is undersowing in peas (grain or forage varieties are both suitable) which may also be taken for silage. Weed control in 

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Weed, pest and disease control in establishing leys... 

A milestone in the routine employment of perruthenate in the oxidation of alcohols was established with the publication by Griffith, Ley et al. in 1987 on the catalytic use of tetra- -propylammonium perruthenate (TPAP).11 The presence of the tetra- -propylammonium cation renders this compound soluble in apolar media and allows the existence of a high concentration of perruthenate ion in organic solvents. The tetra- -propylammonium perruthenate is easily prepared and can be employed catalytically in CH2CI2 solution in the oxidation of alcohols to ketones and aldehydes, using /V-methyl morpholine A-oxide (NMO) as the secondary oxidant. 

The mechanism of the Ley oxidation is complex and the exact nature of the species involved in the catalytic cycle is unknown. The difficulty in establishing an exact mechanism arises from the fact that the complexes of Ru ", Ru ", Ru , Ru and Ru are all capable of stoichiometrically oxidizing alcohols to carbonyl compounds. The TRAP reagent can oxidize alcohols stoichiometrically as a three-electron oxidant and can also be used as a catalyst when a co-oxidant is present (e.g., NMO, TMAO, or hydroperoxides). Data suggests that the oxidation proceeds via the formation of a complex between the alcohol and TRAP (ruthenate ester). It was also found that the stoichiometric oxidation of isopropyl alcohol with TRAP is autocatalytic and the catalyst is suspected to be colloidal RUO2. Small amounts of water decrease the degree of autocatalysis. This observation is supported by the finding that the addition of molecular sieves improves the efficiency of the reaction. 

Having established principles for one-pot coupling reactions using torsional effects, these ideas were extended by Ley s group by merging this approach with the use of different leaving groups at the anomeric position. 

Qin J, Li R, Raes J, et al. A human gut microbial gene catalogue established by metagenomic sequencing. Nature. 2010 464(7285) 59—65. Backhed F, Ley RE, Soimenburg JL, Peterson DA, Gordon Jl. Host—bacterial mutualism in the human intestine. Science. 2005 307 (5717) 1915-1920. 

Having thus established the main stereochemical features, the Claisen rearrangement of glycal esters could be further utilized to provide key intermediates for a number of natural product syntheses Carbohydrates served as starting materials in the total synthesis of the ionophore antibiotics lasalocid A 43 by Ireland et al. [15] and indanomycin 46 by Ley et al. [16] (Scheme 8), as well as the 3-acyl tetramic acid antibiotics tirandamycic acid 49 [17] and (+)-streptolic acid 52 [18] (Ireland et al.. Scheme 9). Several further examples have been reported in the literature [19-21]. 

Small-leaved white clovers. These are used in the long ley and are particularly favoured for sheep grazing. They are rather slow to establish but can become dominant. Kent wild white, AberAce and SI84 are the most popular varieties in this category. 

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