A field experiment was made in rabi seasons (November–April) of 1981–2 and 1982–3 to study the relative efficency of urea and urea supergranules (USG) for spring wheat. USG showed no advantage over prilled urea for spring wheat.

Experiments comprising various ratios of wheat and lentil in a mixed cropping system under two irrigation regimes and three levels of N application are described and the results discussed. In all experiments the highest yield of grain was obtained by growing wheat alone and the highest yield of lentil grain by growing lentil alone. No mixture could equal the yield obtained by wheat alone.

Sheep are commonly used to graze dairy pastures in the late autumn and early winter, to make use of grass that cows have rejected and to utilize any late growth with a minimum of poaching damage. From late December onwards sheep are less welcome to farmers because of the possible harmful effect on the regrowth of grass in the spring. But if the alternative to grazing from January to March is to bring the sheep indoors and feed them hay or silage, then this cost may be greater than that of the grass lost in the spring. Wilman & Griffiths (1978) concluded that the reduction of yield in spring was directly related to date of last grazing but emphasized that they had made no measurement of herbage remaining at this time. Furthermore, their measurements of subsequent yield were in dry matter to a cutting height of 4 cm with no estimate of the amount of ash or green and dead material.

Interception of rain by the plant canopy and stemflow resulting in non-uniform distribution of soil water beneath the canopy has long been recognized in forest trees (Eschner, 1967). Rutter (1975) stated that stemflow may vary from quite small quantities to as much as 20% of the net rainfall and Geiger (1965) had earlier quoted data both from Ovington (1954), who found stemflow to be 0·1–0·3% of rainfall in seven forest canopies, and from Eidmann (1959) showing that a fir and a beech canopy gave 0·7 and 16·6% respectively of the average rainfall as stemflow. However, there have been few studies of the distribution of rain beneath the canopies of agricultural crops despite the implications which non-uniform distribution might have for studies of crop water and nutrients.

Measurements were taken of the draught force, speed and power of three pairs of oxen performing a variety of tasks for long (30 sec) or short (5 sec) periods. True draught force was measured by integrating the force exerted with respect to distance (DADF) and apparent draught force by integrating with respect to time (TADF). The latter type of measurement is that normally obtained from commercially available dynamometers.

In the first experiment short TADF measurements were found to be greater and more variable than long DADF measurements by up to 38% for a variety of jobs. In the second and third experiments in which TADF and DADF were measured completely simultaneously, TADF was nearly always larger than DADF, and the difference tended to be greater with large or jerky loads and smaller, less experienced oxen.

For any given task, the observed variability in replicate measurements of draught force or power was substantially reduced by using long rather than short measurements. However, this effect was not observed in the case of speed of travel.

Potassium occurs in soils in four different forms, namely water-soluble, exchangeable, nonexchangeable and mineral (Reitemeir, 1951; Munson & Nelson, 1963). Water-soluble and exchangeable forms are considered to be directly available to plants. Under continuous cropping one may therefore expect depletion of these two forms, but in fact not much discernible difference in the amounts of available K was observed even after a few crops had been grown. Hence several people have stated that there exists an equilibrium among the following forms of K

This equilibrium implies that a change in magnitude of a form is compensated by the movement from, to and among other forms (Reitemeir, 1951; Garman, 1957; Munson & Nelson, 1963; Chevalier, 1971). If water-soluble and exchangeable forms of K are removed by crops more potassium would become exchangeable from non-exchangeable forms (Maurya & Ghosh, 1972). Whether soils when cropped can maintain the level of exchangeable K depends upon the type of soil, nature and intensity of cropping, the relative rate of removal and release from non-exchangeable form. Continuous cropping therefore alters the existing equilibrium of soil potassium in the profile as crop roots penetrate as deep as 2 m. Since all the potassium fertilizer for a crop is applied at sowing, the temporary overloading of the system may cause leaching losses of K in light soils. This may result in the enrichment of deeper layers.

Two groups of pregnant ewes were given either 1 (control) or 31 (treatment) mg fluoride/1 drinking water. Weekly blood samples were tested for serum fluoride, haematocrit, T3, T4, cortisol, calcium and magnesium. At parturition, serum fluoride was measured in both ewes and lambs. Later, parallel blood and milk samples were taken from ewes and measured for fluoride. Weekly blood samples from the lambs were measured for the same variables, as well as serum phosphate, body weight, bone fluoride and wool production. Serum fluoride in control ewes ranged from 0·6 to 1·9 μmol/1 and in treatment ewes from 8·7 to 35·4/ μmol/1. At birth, serum fluoride of control lambs averaged 0·50 ± 0·042 μmol/1 and of treatment lambs 1·72 ± 0·167 μmol/1. In milk from the control group mean fluoride concentration was 7·11 ± 0·403 μmol/1, and from the treatment group 22·0 ± 1·48 μmol/1. No differences in haematocrit T3, T4, cortisol, calcium or magnesium of ewes were apparent during pregnancy. At birth, body weight of the treatment group lambs was reduced, and T3, calcium and magnesium increased. At 3–4 weeks mean bone fluoride of lambs was higher in the treatment group (580 ± 117 mg/kg) than the control group (105 ± 26·9 mg/kg). After 7 weeks there was an upward trend in serum phosphate of treated lambs, and their wool production (clean fleece weight) at 17 weeks was reduced by 18%, primarily because of decreased staple length.

Much of the recent increase in crisp lettuce production in the U.K. has been marketed as heavily trimmed solid ‘Iceberg’ heads, wrapped in plastic film. Supermarkets want ‘Iceberg’ lettuce with a minimum trimmed weight of 450 g (Anon. 1983) and consistency of product, but the mean head weight of crisp lettuce at maturity can vary considerably from one sowing to another as a result of environmental conditions earlier in growth (Pew, Gardner & Bessey, 1984; Wurr & Fellows, 1984). In midsummer, some sowings of the most popular variety Saladin can produce larger and heavier heads thanc supermarkets require and the cause of this variation needs to be understood in order to increase the proportion of crops meeting supermarket needs.

Biomass production in barley is determined by the amount of solar radiation absorbed by the foliage (Gallagher & Biscoe, 1978). As incident irradiance per unit area varies little between neighbouring sites and seasons in the cereal growing areas of the U.K. (Monteith, 1978), biomass production will largely be governed by the size of the canopy, the orientation of canopy constituents and the efficiency of conversion of absorbed radiation into dry matter (Green, 1984). Reviewing the literature, Monteith & Elston (1983) have highlighted the constancy of mean seasonal efficiency, concluding that growth is limited by the ability of the stand to absorb radiation.

Research conducted on sowing dates has shown a trend towards increased yield as sowing is advanced for winter wheat (Darwinkel, Hay & Kuizenga, 1977; Walker, 1980) and winter barley (Selman, 1980; White, 1981). Green & Ivins (1985) have quantified the rate of yield decline for winter wheat as sowing is delayed after mid-September, giving a mean value of 0–35% per day. For a similar study on winter barley (Green, Furmston & Ivins, 1985) a yield decline of 0–43% per day delay in sowing was attributed to reductions in the number of ears per unit area as planting was delayed.

Biomass accumulation in cereals is an important determinant of grain yield (Green, 1984). However, when attempting to maximize dry-matter production a taller crop more prone to lodging may result (Boothroyd & Clare, 1984). While many contemporary triticale cultivars contain a dwarfing gene, most are very tall relative to wheat and barley (McDonald, 1984) and lodging is a particularly important factor in growing triticale crops.