Results are reported from experiments carried out in three seasons in an environment with mild winters and early springs in which the date of sowing of winter oil-seed rape was varied from early September to early December. Consistently high seed yields were achieved in the late sowings and, in two of the three seasons, delaying sowing beyond early September resulted in significant yield increases. The pattern of dry-matter accumulation and changes in leaf area index were affected to a large extent by sowing date, but no significant effect on total dry-matter production at final harvest was found. Numbers of axillary inflorescences per plant and, in two of the experiments, numbers of fertile pods/m2, were reduced by late sowing, but large increases in numbers of seed per pod were found in each experiment. Mean weight per seed was reduced when sowing was delayed but there was no consistent effect on oil content. Differences were found between cultivars in the extent to which delayed sowing produced increased yields. It is suggested that early spring growth, delayed flowering and reduced reflexion of radiation during flowering were important factors leading to the high yields achieved by late sowings. No interactions were found between sowing date and plant population density for any yield component in one experiment.

The effects of nitrogen applications, ranging from 0 to 25 g N/m2, on the nitrogen uptake and growth of the potato crop was studied in an experiment in both 1983 and 1984. Nitrogen uptake was substantially increased by fertilizer application. At high rates of nitrogen application, the crops took up more than was needed to satisfy their immediate requirements for growth. Initially, this extra nitrogen appeared predominantly in the form of soluble protein in the leaves and nitrate in the stem, with reduced-nitrogen in the tubers becoming a large component during tuber bulking. Application of 25 g N/m2 increased the partitioning of nitrogen to the foliage compared with the tubers.

Tuber yield was considered to be a product of four processes: radiation interception, conversion of intercepted radiation to dry matter, partitioning of dry matter between tubers and the rest of the plant and regulation of tuber dry-matter contents. Maximum tuber yields at final harvest were achieved with 15 g N/m2 in both years. Yield increases were due to increased radiation interception, while the photosynthetic efficiency of the canopy and the dry-matter contents of the tubers were little affected. Increases in light interception, in response to nitrogen, were partially offset by a concomitant decrease in the proportion of the dry weight partitioned to the tubers, particularly during the initial period of tuber bulking. The effect of nitrogen application on tuber yield was, therefore, dependent on the date of harvest.

In field investigations in a sandy-loam soil, probit percentage seedling emergence of commercial and aged seed lots of spring wheat (Triticum aestivum L., cv. Timmo) was a positive linear function of probit percentage laboratory germination and mean soil temperature and a negative linear function of percentage soil moisture content over the ranges 12·1–15·5% moisture content and 7·0–11·0 °C. In a laboratory investigation using the same soil a similar form of relationship was observed in six lots over a range of constant soil moisture contents between 10 and 18% and at constant soil temperatures of 8 and 20 °C. In all cases there was no interaction between any of these determinants of seedling emergence.

Linear relationships between the mean rate of seedling emergence in the field (i.e. reciprocal of mean emergence time) and probit percentage laboratory germination and mean soil temperature were shown, but there was no obvious effect of mean scil moisture content between 12·1 and 15·5% on rate of field emergence. Seed lots of different percentage laboratory germination had the same base tsmperature for emergence (1·9 °C): differences between seed lots in mean emergence rate were due to different thermal time (day-degree) requirements for emergence; the thermal times required were a function of probit percentage germination in a standard laboratory test. The implications of these results in providing better advice on sowing rates are discussed.

Samples of pig feed, infested to various known amounts with Acarus siro L., were scanned using an NIR analyser. Visual inspection of the spectra of infested feed did not indicate the presence of mites, but principal components derived from these spectra were correlated with the number of mites. Examination of the spectrum of Ringer solution, and of principal components for both infested feed samples and for mites scanned in isolation, indicated that in infested samples mite haemolymph caused the absorbance maximum for water to be shifted towards the visible end of the spectrum. Simpler calibration models, of the type used by current commercial NIR analysers, were developed which were able to detect and quantify economically significant levels of mites in infested pig feed.

A field experiment comprising four rates of application of atrazine (0·25, 0·50, 0·75 and 1·0 kg/ha), three times of application (pre-emergence, 10 days after emergence and 20 days after emergence) and two additional treatments of unweeded and weedfree-crop was conducted at the National Dairy Research Institute, Karnal during the rainy seasons of 1979 and 1981. Application of atrazine at 0·25 and 0·5 kg/ha preemergence and 10 days after emergence gave effective control of weeds and resulted in green and dry fodder yields of sorghum similar to weed-free conditions. It was noted that pre-emergence application of the atrazine at 1·0 kg/ha showed a phytotoxic effect on sorghum and resulted in significant reduction in green and dry fodder yields compared with 0·5 kg atrazine/ha.

An experiment with 36 high-yielding spring-calving cows studied the effect of 1 or 6 kg/day of concentrates offered to cows on either continuously stocked grazing or rotational strip grazing. A 4 × 4 latin-square design with periods of 3 weeks duration was adopted.

Mean yield was 29 kg/day of fat corrected milk (FCM). The continuously stocked cows had higher milk yields, consumed more herbage organic matter, grazed longer, with bites of smaller size and responded less in total intake to the higher level of concentrates than the strip-grazed cows. The higher concentrate treatment increased milk yields but reduced fat contents so that the average response was 0·26 kg FCM/kg concentrate. There was no difference in response to concentrate allowance between grazing treatments.

The differences recorded between grazing systems were attributable mainly to differences in green herbage allowance, which was greater with continuous grazing.

Nitrogen fixing, free-living, organisms like Azotobacter and Azospirillum are known to increase the nodulation and efficiency oiRhizobium (Krasilinikov & Korenyakov, 1944). The beneficial effect of incorporation of Azotobacter with Rhizobium may be due to the production of auxins (Vancura & Macura, 1960) and prolonged survival of Rhizobium in the presence of a large amount of polysaccharide gums (Krasilinikov & Korenyakov, 1944). In green gram (Vigna radiata L. Wilczek), because of high temperature and unavoidable soil moisture stress during hot and dry summer months (April-June), survival of the seed-inoculated Rhizobium is very poor (Lai, Dubey & Chandra, 1983). In the present study attempts were made to improve the efficiency cf Rhizobium as an inoculant by the use of Azotobacter chroococcum and Azospirillum brasilense.

Callosobruchus maculatus (F.) is a very serious pest of cow pea in storage in Nigeria and many other oountries (Singh, 1977; Tindall, 1983). Damaged seeds are riddled with emergence holes, defaced with egg covers and have reduced viability. Heavy attack causes severe powdering and weight loss. In Nigeria, about 30–60% loss in cow pea is attributed to infestation and damage by bruchid beetles over a 3- to 6-month storage period, of which over 90% is caused by C. maculatus alone (Caswell, 1981).

Rapeseed and mustard cultivars aro morphologically determinate but the growth of the raceme, which is a corymbose type, is indeterminate. On the raceme flower opening proceeds acropetally in a sequential manner with one or two flowers opening each day. Thus there is a considerable time lag between first and last flower opening within the same raceme. In these oil-seed crops, besides leaves both pod wall and stems are photosynthetically active and the share of assimilates contributed by these three organs to the growing seeds has been estimated to be 37, 32 and 31%, respectively (Brar & Thies, 1977). A rapid decline in leaf area during pod filling in rapeseed and mustard (Chauhan & Bhargava, 1984) and rape (Allen & Morgan, 1972) cultivars has been observed. The assimilate supply to the pods developing at different periods may, therefore, differ owing to a decline in the leaf source as well as increasing intornal competition between pods. In winter oil-seed rape (Brassica napus), both mutual competition for assimilates and shading resulting from excessive pod production have been reported to cause heavy seed and pod losses (Mendham, Shipway & Scott, 1981). No information is available for rapeseed and mustard cultivars on how different components of the pod, such as its weight, seed weight, number of seeds and seed oil percentage, change according to their position on the terminal raceme. This information may be useful in deciding the appropriate number of pods on a raceme for optimum yield.

Hagberg falling number (HFN) is used to estimate alpha-amylase activity in wheat grain (Perten, 1964) and it is utilized by flour millers and the Intervention Agencies of the European Economic Community as a grain quality measurement for breadmaking (Anon. 1983). High nitrogen fertilizer application can lead to lodging and can decrease HFN (Brun, 1982). This may result from damp conditions around the ear encouraging germination, and therefore increasing alpha-amylase activity (Stewart, 1984). However, since nitrogen application can also delay maturity, it has been suggested that this influence could maintain high falling number (Anon. 1985). Pushman & Bingham (1976) found that increased nitrogen application decreased alpha-amylase activity, lending support to the previous suggestion, but contrasting with the results of Brun (1982).

The efficient use of fertilizers is important because fertilizers are one of the costliest inputs in crop production. Compared with N fertilizers, P and K fertilizers are subject to less leaching and leave sufficient residues in the soil, which are utilized by the succeeding crop. Thus a knowledge of the residual effects of P and K fertilizers is essential when formulating a fertilizer programme. In order to test the 1st year residual as well as longer-term effects of P, K and farmyard manure (FYM) on tuber yield and soil properties, a manurial experiment was started in 1970 on an acid hill soil at Fagu, Shimla representing the North Western Himalayan hills of India, at an elevation of 2500 m above sea level. The results of the experiment from 1970 to 1975 have been reported by Sharma, Grewal & Singh (1980) and the results from 1976 to 1979 are reported in this paper.