An experiment with two blocks containing phased sequences of continuous spring barley after beans or fallow was located on sandy soil over Lower Greensand on a gentle north to south (N–S) slope at Woburn Farm. Season had the greatest effect on yield with a 135% difference between the worst (1975, 1·73 t/ha) and the best (1974, 4·06 t/ha). years. N–S position was the next most important factor with average differences of 65 and 52% between the plots at the top and bottom of the site in blocks I and II respectively. The third most important factor was E–W position which gave a maximum difference of 35% in 1975.

A fertility trend with a strong linear component, which was most conspicuous in drier years, followed the main slope of the experiment and was attributed to erosion (fieldwash). After 1972 as different cropping sequences were progressively introduced, yield variation due to crop sequence differences was confounded with this positional effect.

Crops in the eastern block were taller by l·5–12·3% and, after adjustment for the linear trend, yield was on average 15·6% greater than in the western block. The site is astride a N–S soil boundary with Stackyard series to the east and Cottenham series to the west. The Stackyard soil has a greater available water capacity, and is subject to drought less frequently than the Cottenham soil. Using Penman's (1971) data for the Cottenham series at Woburn and estimates of profile available water for the two series elsewhere on the farm, theoretical yields were derived, which were generally greater than actual yields adjusted for the N–S linear trend (block means 1·47–4·32 t/ha), but which showed similar trends in the between-block differences. Explanations for discrepancies between theoretical and actual yields are discussed. The incidence and severity of take-all disease and differences in soil pH were always small and unlikely to have caused significant yield variations.

An experiment has been made to study the effect of the pattern of distribution of a fixed amount of production compound on milk yield, milk composition and live-weight change in the first 20 weeks of lactation and any carry-over effects on performance in the remaining part. Adult British Friesian cows of predicted high yield potential were randomly allocated to a graded (G) or flat-rate (F) system of feeding.

There was no significant effect of treatment on milk yield, milk composition or yield of milk constituents in the experimental period or in the whole lactation.

Live-weight changes were not significantly different between treatments at any stage of lactation. Calculated energy balances showed losses until the 4th week of lactation. Thereafter positive balances occurred but it was not until the 9th week for treatment G and the 15th week for treatment F that the original zero balance was restored. The total balance was in good agreement with live-weight gain for treatment F but not for treatment G.

Calculated efficiencies of utilization of metabolizable energy for milk production (Klo) were variable throughout lactation and lower than the currently accepted standards.

Information is assembled on how much wheat yields vary from place to place, from year to year and between years in England and Wales. Some indication of the practical importance of this variation is given by comparisons with the yield differences caused by individual management decisions as measured in comparative experiments, and with plot-to-plot variation in such experiments.

Four bruchid-resistant and four susceptible cow-pea cultivars and their F2 crosses were evaluated for oviposition, egg hatching and emergence scores of cow-pea weevils, Callosobruchus maculatus Fabr.

Whereas oviposition and number of eggs hatched were normally distributed, percentage of eggs hatched was not. For percentage weevil emergence, the F2 progenies with susceptible parents as females had a different distribution from that of their reciprocals with resistant parents as females.

Preferential oviposition was not observed among the parents and their F2 progenies. Resistance was observed at the egg hatching and weevil emergence stages. Percentage of eggs hatched was significantly and positively associated with percentage weevil emergence.

For many horticultural crops the distribution of weight over size grades is of more importance than the total weight. This paper shows how simply determined features of interrelationships of the weight, size and shape of an individual in the crop can be combined to provide estimates of various aspects of the distribution of crop weight over size grades. The two relationships required are (i) the probability density function of the grading variable for the crop; (ii) a function relating the weight of an individual to the corresponding value of the grading variable.

The paper shows how each of these can be determined either from published data or by simple experiment. Examples using data on onions and carrots are given to illustrate this and also to show some of the more important practical applications of the methods. For example, they allow the results of grading with one set of size grades to be extrapolated to a different set of grades without recourse to further measurement or experimentation and this is illustrated using published data on carrots. Other possible uses are also discussed and outlined.

Chlorophyll contents per unit leaf area and unit dry weight, chlorophyll a:b ratio, visual colour rating, specific leaf area, and leaf fresh weight: dry weight ratios were estimated for 12 couch (bermudagrass) varieties (Cynodon spp. L.) in winter (July) and spring (October). Net photosynthetic and dark respiration rates were estimated in winter only.

The chlorophyll contents per unit leaf area were higher in all varieties in spring than in winter, but per unit weight were more variable. The varieties differed substantially in the net photosynthetic and dark respiration rates. The specific leaf areas were greater in winter than in spring in five varieties: in others it changed little. The fresh: dry weight ratios of the leaves were almost constant between varieties in the spring but varied greatly during the winter. Visual colour ratings were well correlated with chlorophyll contents per unit area but not with weight. The net photosynthetic rate was closely correlated with chlorophyll content (per unit area) but not so closely with colour rating.

Herbage intake by grazing dairy cows can be estimated by measurements on the pasture ('t Mannetje, 1978) or by measurements on the animal (Raymond, 1969; Corbett, 1978). Of the sward sampling techniques, the difference method, based on pre- and post-grazing sampling, has the greatest potential for providing valid estimates of herbage intake, but only when grazing periods are short and stocking densities are relatively high (Pigden & Minson, 1969). Estimates of intake by measurements on the animal are made by the faecal output-indigestibility ratio technique (Raymond, 1969; Corbett, 1978). The most widely used marker for the determination of faecal output is chromic oxide (Cr2O3).

The factorial approach to the determination of the dietary requirements of macroelements is a two-stage process; in the first the net requirements are estimated and in the second, the fractional absorption of the dietary mineral is used to convert net to dietary requirements (Agricultural Research Council, 1965). At the first stage the maintenance component is allotted a fixed value, so that estimated dietary requirements are directly proportional to absorbability of the element.

Barley (Hordeum vulgare L.), an important cereal crop in India, is grown mostly under rainfed conditions on about 3 million hectares. Vigorous and rapid development of roots of cereals contribute considerably to drought resistance (Genkel, 1961; May, Milthorpe & Milthorpe, 1962; Abdel Rahman, Batanouny & Ezzat, 1967; Bhan, Singh & Singh, 1973; Chang & De Datta, 1975). Many workers (e.g. Abdou & El-Kobbia, 1976; Basu & Gupta, 1974; May et al. 1962; Bozhenko, 1965; Woodruff, 1969; Salim & Todd, 1968; Hussain, May & Aspinall, 1968; Shkolnik & Bozhenko, 1974) have reported that pre-sowing seed treatments increase plant vigour and grain production. The production of barley under rainfed conditions in winter (November–February) depends greatly on the extent to which it can exploit the stored soil moisture after the harvest of the previous crop grown with monsoon rains in India during June–October. The main objective of the study was to dermine to what extent the increase in seedling vigour caused by pre-sowing treatments of seeds can be exploited for increasing the production of barley which has to depend mainly on the continuously depleting soil moisture, after the cessation of monsoon rains, and to investigate the possible reasons for such variations.

Since Monteith (1977) proposed that growth can be analysed in terms of the amount of energy intercepted by the leaf surface and the efficiency of its use, there has been much interest in the measurement of light interception in potato crops (Scott & Wilcockson, 1978; Milford et al. 1980; Allen & Scott, 1980). This can be measured directly using tube solarimeters placed horizontally above and below the canopy. However, this method suffers from three major drawbacks: (a) in an experiment with many plots it becomes expensive in terms of equipment, (b) a single solarimeter samples only a very small part of the plot canopy, and (c) the solarimeter cannot distinguish between living leaves and other material. Thus, when the crop lodges and/or starts to senesce, visual observations suggest that the area over the solarimeter may not be representative of the plot as a whole.

Nutritional problems for cultivated plants related to phosphorus (P) and zinc (Zn), among other elements, are common in recent alluvial calcareous soils of Greece. The negative interaction which exists between these two elements aggravates these problems.

During the last decade, a calcium (Ca) deficiency syndrome, nutritional secondary hyperparathyroidism (NSH), has caused lameness and bone lesions in horses grazing certain tropical grasses in Australia. These grasses contain over 0·5% total oxalate (Walthall & McKenzie, 1976; Blaney, Gartner & McKenzie, 1981a). Blaney et al. (1981a) and McKenzie, Blaney & Gartner (1981) carried out mineral balance experiments with horses fed tropical grass hays or diets with added soluble potassium oxalate. Their results suggested that NSH was caused by the oxalate in the grasses preventing the absorption of Ca. They also suggested that the Ca in the grasses may already be in the form of the insoluble calcium oxalate (Ca(COO)2) salt and thus unavailable to grazing horses. Blaney, Gartner & McKenzie (1981b) subsequently demonstrated that horses could not absorb significant amounts of Ca from Ca(COO)2 crystals added to their diet.

Coriander is an important aromatic plant of India. On steam distillation, the seeds yield a colourless or pale yellow volatile essential oil, which is used for flavouring food products, liqueurs, alcoholic beverages and perfumes. Coriander is also used in the synthesis of vitamin A (Bedoukian, 1967). The Central Institute of Medicinal and Aromatic Plants introduced several Bulgarian selections of coriander and evolved a superior variety, CIMPO S-33. This variety contains more essential oil (about 1·5%) than the local varieties available in India (0·2–0·3%) (Dimri, Khan & Narayana, 1976). Earlier work on coriander has shown that application of N (Bhupinder Singh et al. 1979) and N, P and K (Vagujfalvi, 1964) increases seed and oil yields of coriander. Information on nutrient uptake by coriander and on the effect of fertilizers on coriander oil quality is not available in India. The present experiment was designed to study the effect of different rates of nitrogen, phosphorus and potassium application on seed yield, yield and quality of essential oil and N, P and K uptake by coriander (cv. CIMPO S-33).

Rape (Brassica campestris L.) is well adapted to the Bangladesh climate and is an important oil crop of the northern part of Bangladesh. It requires a shorter growing season than any other crop of this kind but is less resistant to drought, which causes considerable damage to the crop by reducing total green area during late December and January and results in a poor yield. Considerable increase of rape-seed production will be possible through the elimination of drought by irrigation, the right supply of nutrients and application of proper cultural practices. We report here on studies of the effect of fertilizer under irrigated and non-irrigated conditions on the seed yield, oil content and some seed yield associated characters of rape and the importance of irrigation in rape cultivation in Bangladesh.