Several introduced high-yielding varieties of grain sorghum were screened for natural infestation of shootfly Atherigona yorki Deeming, and stem borers, Sesamia cretica Led. and Chilo partellus (Swinhoe), at different sowing dates in 1980–1 and 1981–2 sowing seasons in People's Democratic Republic of Yemen (PDR Yemen).

The recently introduced high-yielding variety Dwarf White Milo (DWM) was found to be more prone to infestation by shootfly and stem borers than the local variety ‘Baini’ although it gave higher yield. All varieties tested gave higher yields when sown in March, August, September than when sown in April, May, October or November; 26 August and 16 September sowings gave the highest yields. B815, W823 and 8454 gave higher yields than the recently recommended high-yielding variety DWM, in response to lower infestation with the shootfly and stem borers; B815 and 8454 gave higher yields when sown on 26 August than when sown on 16 September. On the contrary, W823 gave higher yield when sown on 16 September than when sown on 26 August. This information could be used in formulating insect pest management programmes for sorghum pests in PDR Yemen.

Upward flux of water and deep-placed (8–10 cm) P was studied in columns of sandyloam and silty clay loam, with water tables of 60 and 90 cm, each subjected to potential evaporation rates of 2–2 and 7–5 mm/day, for 15 days. An amount of 300 mg P/kg soil, labelled with 20 /tCi 32P/g P, was applied as diammonium hydrogen orthophosphate.

Evaporation losses increased with increase in potential evaporation (PE) and decrease in depth to water table in both soils, but the ratio of actual to potential evaporation (AE/PE) decreased with increasing PE, indicating that the evaporative losses in both the soils were mainly controlled by their hydraulic conductive properties. Under no circumstances did AE equal PE. Evaporation, in general, was higher from sandy loam than from silty clay loam.

Corresponding to water flux, total upward P flux increased with increasing PE and decreasing depth to water. In the sandy loam, with 2–2 mm PE/day, 21 % of the deepplaced P moved to the soil surface with the 60 cm water table, against 5 % with the 90 cm water table. Under 7–5 mm PE/day, 39% P migrated to the surface with the 60 cm water table, but no 3aP was detected at the surface with the 90 cm water table. In the silty clay loam, however, P movement was much restricted.

In this study two field experiments were conducted on a heavy to medium heavy, calcareous, recent alluvial soil of Central Greece. The main aim of these experiments was to study the effect of the most common nitrogen sources, applied in one or two doses, on maize growth and fertilizer utilization. Foliar application of urea was also a treatment included in these experiments.

Phosphorus alone had no significant effect on maize yield. Nitrogen (various forms), alone or in combination with phosphorus, increased the yield and nitrogen content of maize. Maize yield was not significantly affected by the form of nitrogen or by dividing the application of nitrogen. Foliar applications of urea were as effective as soil applications in increasing maize grain yields.

The percentage of fertilizer nitrogen taken up (utilization coefficient) ranged between ca. 58% for sodium nitrate and ammonium nitrate, and ca. 39% for ammonium sulphate and urea, when the fertilizers were applied about 10 weeks after sowing. Foliar urea was nearly as efficiently utilized as urea applied as a sidedressing. Application of the tested fertilizers before sowing was nearly as efficient as or more efficient than application of the fertilizers as a sidedressing at 70 cm plant height (38 days after sowing). Finally, addition of 120 kg N/ha enhanced the amount of soil nitrogen taken up in the maize crop by 33%.

A field experiment was conducted for 2 years during the crop seasons of 1980–2 to study the effect of diverse plant spacings and rates of nitrogen application on the yields of herb and essential oil of palmarosa (Cymbopogon martini Stapf. var. motia). The results indicated that at closer plant spacings of 30 × 30 cm (110 000 plants/ha) and 45 × 30 cm (74000 plants/ha), palmarosa responded to higher amounts of N fertilizer (240 kg N/ha/year). It was suggested that a plant spacing of 30 × 30 and 45 × 30 cm and application of 240 kg N/ha/year result in high essential oil yield of palmarosa.

Seventy-six first-calf cows (heifers), 32 second·calf cows and 39 adult cows participated in a trial in which three diets composed of 60:40, 75:25, 90:10 proportions of compound to hay (hay dry-matter digestibility 0·6) were given for the first 36 weeks of lactation in amounts to provide daily an estimated 125, 156 MJ and ad libitum digestible energy (DE) for heifers, and 156, 187 MJ and ad libitum DE for the other parities. The ad libitum intakes were 150 and 200 MJ DE daily for heifers and for older cows respectively. Greater compound content of the diet and larger daily allowance of DE were associated with increased occurrence of mastitis and lameness but not digestive upsets. Dry·matter (D.M.) digestibility was increased with a greater proportion of compound in the diet but was not affected by the amount consumed or stage of lactation. Milk yield and live·weight change were increased linearly and additively by a greater intake of digestible dry matter and by a greater proportion of compound in the diet, throughout the lactation save for no effect of diet composition on live·weight change in early lactation. On equal feed intakes older cows gave more milk and lost more live weight than heifers in early lactation but not thereafter; responses to additional feed were equal for all parities studied. Milk fat concentration was reduced both by increased allowance and by the high compound diet. Milk solids·not·fat (SNF) concentration was not affected by the treatments. Yield of milk fat was not affected by amount eaten and was reduced by the 90:10 diet. Yields of SNF and milk energy were increased by amount eaten and by increased compound in the diet. Thirty-two primiparous cows continued on their experimental treatments without interruption to the end of the second lactation. In the second lactation the effects on yields of milk, milk energy, and SNF were magnified indicating a cumulative effect from lactation to lactation. Little cumulative effect was observed on either milk fat yield, or concentrations of fat and SNF in milk. More generous feeding was associated with reduced milk output/unit D.M. consumed in the first but not the second lactation. More generous feeding improved live·weight change less in the second than in the first lactation. No cumulative effects over two lactations were observed consequent upon variation in diet composition.

Twenty-nine bunch groundnut genotypes were grown in the Kharifseason 1980 and the summer season 1981 at Bangalore. Growth and yield analysis showed that the total dry-matter accumulation was low up to 30 days after sowing and increased linearly up to the 86th day in the Kharifand up to harvest in the summer season. There were significant differences between genotypes in leaf area indices (LAI), the leaf area duration (LAD) and LAD between pod initiation and harvest (LADP) in both the seasons. The mean LAI of genotypes did not vary much between the Kharifand the summer seasons up to the 66th day. However, during the later stages of growth the LAD was higher in the summer. The higher biological yield and productivity in the summer was attributed to the high LAD and LADP during the later stages of crop growth. LAD and total dry-matter accumulation at harvest were significantly correlated both in the Kharif(r = 0–75) and the summer (r= 0–81). The mean total number of flowers over all 29 genotypes did not vary, but total number of pegs formed per plant differed significantly between genotypes in both the Kharifand summer seasons. The percentage of flowers which produced pegs was 72–2 in summer as against 51–2 in Kharif. The primary branches contributed 86'7 and 90–1 %to the total number of pods per plant in the Kharifand summer seasons respectively. The contribution of the first four nodes of primary branches was 85 %in both seasons. The number of fruiting points (nodes having mature pods) per plant, found to be the most important yield-determining component, showed significant variation amongst the genotypes in both the Kharifand summer seasons. In summer, length of mature-pod-bearing zone (MPBZ), number of nodes in MPBZ and number of kernels per plant were higher than in the Kharifseason. It is suggested that selection and breeding should concentrate on improving LAD and LADP, total dry matter per plant, more primary branches per plant, more pods in the distal nodes of primary branches and more fruiting points (nodes in MPBZ) per plant.

The accurate prediction of the performance of individual lots of sugar-beet seed in the field is critical when constituting blends of seed for commercial use. Previous studies indicated a need for ‘vigour tests’ to supplement the standard germination test. In many of the studies emphasis was placed on evaluation of tests in the laboratory, whereas in this study equal emphasis was placed on the determination of the values to be predicted. The performance of 20 seed lots with a range of germination between 75 and 95% was assessed in field and laboratory studies in 1981. Further investigations of ten seed lots were made in 1982 and in 1983.

The results in 1981 showed little evidence of agronomically important differences in the relative performance of seed lots with respect to establishment in the field at different sites. Similarly, most seed lots showed consistent differences over a range of tests under controlled conditions. However, use of the experiment mean as a measure of stress revealed marked differences in the range of performance between the best and poorest lota in both the field and laboratory. There were clear indications that performance in the field could be modified by non-random factors that tended to reduce the magnitude of differences among seed lots. In 1982 grazing of seedlings by birds was identified as a factor that could cause greater reduction in the establishment of seed lots with high viability relative to those with low viability. Thus, under some circumstances, a single count of seedlings in non-protected field experiments can give misleading estimates of the differences among seed lots (and probably among other treatments which affect the rate of emergence). Correlation coefficients (γ) were about 0·88 for relationships between establishment from pelleted seed in plots protected from birds and germination or emergence under controlled conditions. These results reduced the need for additional vigour tests. However, the studies emphasized that small differences in germination percentage are important as they can be associated with much larger differences in establishment, particularly under adverse seed-bed conditions. The average standard error for the mean viability of individual seed lots was ±1·89 in germination tests with four replicates of 100 seeds at each of six centres. Although inincreased accuracy may not be possible without much greater replication, we found that the distinction between normal and abnormal seedlings was an important source of experimental error. A less subjective measurement, based on hypocotyl height, warrants further study.

Two experiments were conducted to provide information on the precision of herbage sampling, the degree of replication and the logistics of managing rotational and continuous grazing experiments. In a third experiment the possibility of estimating herbage growth, during the rotational grazing of paddocks for 4 days, by linear extrapolation of measured growth estimates made during the interval between grazings was investigated. A fourth experiment was then conducted to investigate animal and herbage production responses to nitrogen applied at five levels over the range 80–900 kg N/ha with three replicates per treatment.

Results from Expts 1 and 2 showed that similar precision could be obtained under both rotational and continuous systems of grazing with the same number of replicates and samples of herbage. There was little advantage in having more than three replicates and four samples per paddock or two replicates and eight samples per paddock. Under continuous grazing a 3-weekly sampling and movement of exclosure cages was indicated. It was also found, from Expt 3 that, under rotational grazing, linear extrapolation of growth from 0–24 days did not reflect growth to 28 days in a consistent manner. Six animals per treatment, permanently in the paddocks, proved adequate for the estimation of live-weight gain.

Experiment 4 confirmed that response curves could be fitted with an acceptable degree of precision if there was one low, one very high, and two intermediate levels of nitrogen. Adjustment of the number of animals to maintain sward height at between 5 and 7 cm ensured similar sward conditions and rates of live-weight gain across all treatments.

The problems associated with the measurement of herbage production under grazing are discussed.

In a series of field experiments over four seasons, in the north-west region of Tasmania, poppy (Papaver somniferum L.) capsules were harvested at various intervals after dry maturity (12% moisture in capsules). Reductions in the relative morphine concentration of capsules were closely associated with rainfall after dry maturity. These values ranged from a reduction of 0·92 to 0·82% over 5 weeks with 13 mm of rain to a reduction of 0·95 to 0·31% over 6 weeks with 79 mm of rain.

In a simulated leaching experiment ground capsules were leached with 50 mm of water. Morphine was detected in the leachate and after being held for 10 days the morphine concentration of the ground capsules had decreased from 0·56 to 0·22%.

Intact capsules from glasshouse grown plants were harvested at 2 weeks (T1, 4 weeks (T2), and 6 weeks (dry maturity T3) after full bloom. At each time of harvest they were immersed in distilled water for four different lengths of immersion time: zero (L0), 6·7 min (L1, 44·8 min (L2), and 300 min (L3). After immersion both the immersion water and the capsules were analysed for morphine. Morphine was readily detected in the immersion water with more at T3 than T2 and the amount of morphine increased as the length of immersion time increased. This latter process was greater at T3 than T2. At both T2 and T3 here was a trend for capsule morphine to decrease as immersion time increased.

Predictions of nitrogen, oil and glucosinolate concentration in rapeseed samples were made by near infrared reflectance analysis after various grinding treatments. Also examined were the effects of normalizing reflectance data and the possible advantage of using all combinations of two and three wavelengths in the calibration regression analysis over forward stepwise regression. The main conclusion was that drying the samples prior to a controlled grinding treatment gave the best results, although acceptable results for selection purposes could be obtained using whole seeds to predict nitrogen and oil. None of the treatments of the seed or reflectance data allowed acceptable prediction of glucosinolate content.

Plants of Cucurbita pepoL. cvs Cinderella, Cobham Bush Green and Goldrush were inoculated with cucumber mosaic virus (CMV) and some grown at each of three temperatures (15, 20 and 25 °C) and three light intensities (13, 40 and 120 W/ma). Symptom severity in all three cultivars decreased with increased temperature but only for ovs Cinderella and Cobham Bush Green when the light intensity was raised. In general ov. Cinderella was most resistant and cv. Goldrush most susceptible, except at 25 °C, when most plants were symptomless.

In a 2-year study, sunflower oultivar EC 69874 produced greater leaf area than EC 68415, but gave similar grain yields. The former was superior in leaf area, head size and yield per plant but was inferior in 100-seed weight. The leaf area was greater at lower plant density (5·5 plants/m2), which resulted in higher 100-seed weight, number of seeds per plant and yield per plant than higher plant density (11·1 plants/m2). Plant density had no influence on the percentage of filled seeds or oil content. Application of nitrogen improved the leaf area, flowerhead size, percentage of filled seeds, 100-seed weight, yield per plant and grain yield up to 60 kg/ha but decreased the oil content.

Twenty-seven sesame varieties from Sudan and U. S. A. were grown in replicated trials in the Sudan central rainlands from 1979 to 1982. Regression coefficients were calculated giving response to environmental indices based on location and year mean yields. Entries with high mean yields generally had regression coefficients exceeding unity and were equal to or better than entries having smaller response even in poor environments. Few lines were identified as desirable varieties which combined relatively high yield and stability of performance, thereby deserving a place in both commercial production and future breeding programmes.

Alachlor, butachlor and carbaryl were highly toxic to the N2-fixing cyanobacterium Nostoc muscorum, when grown on solid minimal (nitrogen-free) medium. At pesticides doses allowing about 20, 50 and 60% survival of the organism, various mutations were obtained in N. muscorum, reverse mutation from het+nif– and het–nif+ auxotrophy to het+nif+ prototrophy, forward mutation for resistance to 0·37 mM L-methionine-DL-sulfoximine, and auxotrophic mutation for the achievement of carbon-auxotrophy through 5 mM methylamine-resistance. The toxic and mutagenic effects of the three pesticides were similar to those of the well known mutagen MNNG.

Field investigations conducted at Ludhiana (India) showed that the foliar application of 2-chloroethyltrimethyl-ammonium chloride (CCC) (50% a.i.) at 300,600 and 900 ml/ha about 5 weeks after planting did not depress plant height. The dose of 600 ml CCC/ha was most effective and increased seed yield by 1·31 and 0·74 t/ha over the control (water spray) in 1978–9 and 1979–80, respectively. The corresponding increases in total yield were 1·37 and 0·86 t/ha. However, in 1980–1 when CCC was applied 3 weeks after planting even the lower dose of 300 ml/ha depressed the plant height. Then the treatment of CCC increased significantly the number of tubers of seed size and seed yield by decreasing the ‘ware’ yield but did not influence the total yield. The yields of potatoes were not affected signifioantly by the application of N-dimethyl amino succinamic acid (B 9) and succinic acid (SA).

In an experiment where the interaction of nitrogen and CCC was studied both factors not only increased the seed yield but also increased the total yield. However, there was no interaction between nitrogen and CCC.

A total of 15 rumen-cannulated sheep and four rumen-cannulated goats (Expt 3) were used in five latin square experiments designed to investigate the effects of carbohydrate supplements on ruminal ammonia concentration in animals given grass silage diets. In Expt 1 barley supplements were given at the same time, 1 h before or 2 h before a meal of silage. The treatments were designed to alter the synchronization between energy release from fermentation of barley and ammonia release from the degradation of silage N compounds. As compared with the unsupplemented control diet, barley supplements reduced (P < 0–05) rumen ammonia concentration and increased (P < 0–01) the number of total protozoa, but the time at which barley was given was without effect. In Expt 2 animals receiving silage or silage-barley diets were defaunated chemically. This treatment led to a 20–25 % reduction in rumen ammonia concentration. In Expt 3 supplements of maize starch, glucose and sucrose were compared. Mean ammonia concentrations were 231 mg/1 for the control unsupplemented diet and 205, 155 and 160 mg/1 (S.E. 21) for the starch, glucose and sucrose treatments. Corresponding numbers of protozoa were 7–7, 15–1, 6–1 and 6–3 x 10s/ml (S.E. 1–8). In Expt 4 the diets were unsupplemented silage or the same diet plus supplements of sucrose or xylose. Xylose reduced ammonia concentration more than sucrose, the values (mg/1) being 236 (control), 206 (sucrose) and 125 (xylose) (S.E. 19). There was no difference between the supplements in numbers of protozoa. Xylose induced a smaller reduction in pH, a higher (P < 0–05) proportion of acetate and a lower (P < 0–05) proportion of butyrate in rumen fluid than did sucrose. Effects of rumen pH were examined in Expt 5 where supplements of sucrose were given alone or together with NaHCO3. Rumen pH values were 6–38 for the control unsupplemented diet and 5–99, 6–28 and 6–55 (S.E. 0–06) for the diets supplemented with sucrose, sucrose plus 50 g NaHC03 and sucrose plus 100 g NaHCO3. Corresponding values for ruminal ammonia were 193, 151, 93 and 41 mg/1 (S.E. 10). Differences in VFA proportions between sucrose treatments were small and significant (P < 0–05) only for butyrate. It is concluded that there are important differences between carbohydrate sources in their effects on nitrogen metabolism in the rumen. Differences between starch and sugars appear to relate to the influence of the carbohydrates on the microbial population of the rumen, as was indicated by the differential effects of the carbohydrate sources on the number of total protozoa; differences between sugars appear to depend in part on the rates of sugar fermentation and the associated reduction in rumen pH.

Chick pea Rhizobiumstrain RG 4 was treated with 30 /tg/ml of N-nitrosoguanidine and four mutants isolated were resistant to 400 /tg carbendazim/ml. Only two of the mutants (M 1 and M 4) retained the capacity to form nodules. On the basis of number of nodules, their dry weight, nitrogenase activity, triphenyl tetrazolium chloride reductase activity and active iron content of nodules, mutant strains M 1 and M 4 were found to be equally effective for nitrogen fixation both with and without carbendazim (bavistine) and resulted in significantly greater grain yield than the corresponding uninoculated treatments.

The quantity–intensity relationships between gains and losses of exchangeable K of the soil, and the K-intensity in the equilibrium solution, were determined for two soils incubated at 25 ± 1 °C for 0, 2, 4, 6 and 8 weeks under submerged conditions. The Kintensity modified to include the factor (F) by which Mg differs from Ca in its behaviour on the exchange complex, i. e. aK/(a½Ca + F.a½Mg), gave significantly lower values of equilibrium activity ratio, , and higher values of linear buffering capacity (LBCK), than when measured by the simple ratio, aK/(aCa + aMg)½. The mean value of the factor, F, was 0·46 for Conlubang sandy loam and 0–49 for Luisiana clay. Submergence up to 2 weeks resulted in an increase in the equilibrium activity ratio, , by 43–3% in Conlubang sandy loam. In Luisiana clay, , increased slightly after an initial decrease. In both soils, the readily exchangeable K, , increased with submergence, more so in Conlubang sandy loam than in Luisiana clay. Linear buffering capacity, LBCk, which is a measure of the rate of release of K to the soil solution, increased markedly with soil submergence.

Local soil erosion has long been a problem on very fine sandy and silty soils in south Somerset. Some 40 fields in arable use were chosen randomly and monitored monthly for erosion in the winter of 1982–3. Erosion was measured along fixed traverses and then compared with soil attributes, site factors and cultivation practices. Winter cereals were worst affected with a third of the fields having soil losses in excess of 4 m3/ha. There was least erosion on bare ploughed ground and moderate losses on cash root crops. Soil type, organic-carbon content, clay content, drill direction, wheeling density and slope all affected soil loss in winter cereal fields.

Erosion did not assume serious proportions until a combination of soil surface conditions and soil wetness allowed run-off to form rills. Only moderate falls of rain were then needed for widespread removal of soil. Preventative measures include grassing slope convexities, more grass in the rotation to improve soil organic matter and structure, avoiding wheelings, drilling across the slope and keeping headland widths to a minimum.

Statistics are presented to illustrate the influence of growing season and location on the accuracy of NIR testing of hard red spring wheat for protein. The influence of season was greater than that of growing location, and highly significant errors are likely to occur if protein is predicted in samples from one growing season using a calibration based on samples from another season. The same was true to a lesser extent if samples from one growing location were analysed using calibrations based on samples drawn from different areas. There was evidence that some growing areas were less susceptible than others to the seasonal influence, whereas certain seasons (e.g. 1976) exerted more influence than others. Errors in predicting protein were considerably greater than errors in predicting moisture. The development and use of universal constants incorporating samples from a wide range of location and several seasons effectively counteracted the influences of both season and location, and universal constants have been developed for use in the NIR instruments of leading manufacturers, for hard red spring and durum wheats, and barley. The concept and principle of 2·point calibration using normalized mathematical treatment of the log 1/R signal is discussed and its efficiency in providing a stable calibration for the prediction of protein in hard red spring wheat has been demonstrated.