Field experiments were carried out in the early and late growing seasons in the rainforest zone of Nigeria to determine the responses of yield, components of yield and nutrient contents of cow pea to magnesium fertilizer. Yield and components of yield studied were not significantly increased by Mg application but N, P and Zn concentrations were significantly increased, while Mn concentration decreased significantly with applied Mg.

Yield was positively correlated with the micronutrient (Zn, Fe, Cu, Mn) concentrations of cow pea. A level of 0·43 m-equiv/100 g of exchangeable Mg or 15% Mg saturation appears adequate for successful cow-pea production in a typical forest zone within the humid tropics.

Spring-barley straw or maize silage were the major components in mixed diets of compound and forage fed to yearling dairy heifers. With straw, rolled barley was fed either alone or with fishmeal, soya-bean meal, protected soya-bean meal, whey + urea or Ewoplua (a product made from whey and rich in lactosyl urea). With maize silage the rolled barley was fed either alone or with fishmeal, whey + urea or Ewoplus.

When straw was included in the diet fishmeal and protected soya-bean meal increased live-weight gain, and all the supplements increased nitrogen retention. When maize silage was fed, only fishmeal increased live-weight gain although all the supplements increased digestibility. Concentrations of rumen NH3-N were increased by all the supplements, when fed with straw, and also by maize silage when fed without an N supplement or with fishmeal. Small changes were noted in total and molar proportions of VFA.

Calculated ME intakes suggested a more efficient use of energy for growth from maize silage than from straw, except when the straw diet was supplemented with fishmeal.

From the progeny of a cross between the winter wheat varieties Norman and Talent early and late F5 lines were selected in the field. These selections and the two parental varieties were grown in controlled environment cabinets to assess their sensitivity to photoperiod and vernalization.

The F5 selections and Norman and Talent were also grown in field trials, at the Plant Breeding Institute in Trumpington, and at The Murrays Experimental Farm of the Scottish Crop Research Institute, near Edinburgh.

Norman was more sensitive to photoperiod and vernalization than Talent. The early F5 lines were relatively insensitive to photoperiod and/or vernalization. The late lines were sensitive to both photoperiod and vernalization. Differences in date of ear emergence among the selections were found which were independent of photoperiod and vernalization sensitivity. This variation in ear emergence, described as earliness per se, was similar under controlled environment conditions and in the field, and was also shown to be similar in magnitude to that due to differences in sensitivity to photoperiod and vernalization. Both sources of variation can be exploited to modify time of ear emergence under field conditions in Great Britain.

Disks of hard wheat (Triticum durum Desf.) leaves subjected to rapid desiccation over 4 h showed noticeable changes in the shape of the in vivo chlorophyll fluorescence induction curves. In drought-sensitive varieties (such as Claridoc), water stress resulted in a strong inhibition of the slow fluorescence induction transients. In particular, the fluorescence quenching rate was markedly decreased in water-stressed leaf disks. In contrast, leaves of drought-resistant varieties (such as Aouedj) showed only minor changes in chlorophyll fluorescence. The results of this investigation suggest that the slow transient of the in vivo chlorophyll fluorescence induction phenomenon may provide a simple method for selecting drought-tolerant wheats.

A model of reproductive performance in dairy herds is described. The model relies upon no empirical relationships but is constructed from a series of simple stochastic processes involving only three principal parameters: ovulation detection rate, pregnancy rate and embryo loss rate. The model shows how the complex interactions between these parameters and management policy concerning the definition of the service period are generated.

Involvement of plant genotype, stage of development of plant and seed, fertilizer and irrigation in frost tolerance of oil-seed Brassica spp. were examined. The number of apparently frost-killed or undeveloped seeds has been used to assess tolerance. Three B. campestris L. genotypes namely Span, Torch and Bell showed considerable tolerance of frost. Very young and also nearly mature seeds were less affected by freezing than seeds at an intermediate stage of development. The amount of nitrogen fertilizer applied had no effect, but the unirrigated orop was injured by frost more than the irrigated one.

The influence of physiological state (pregnant, lactating, dry) on body composition and fat partitioning in Friesian cows has been examined. A total of 20 cows, four per physiological state, were slaughtered and their left half carcasses dissected into individual muscles, bones and fat depots. All body parts, including the internal organs and fat depots, were weighed at slaughter.

Muscle tissue and the internal organs showed some weight changes, consistent with a redistribution of tissue towards the udder and gut, and mobilization of muscle, but the major changes in weight associated with changing physiological state occurred in total body fat.

Intermuscular fat made the greatest absolute contribution to changing fat weight, but subcutaneous fat showed the greatest proportional change with changing physiological state. The order of depletion of fat depots during fat loss was approximately the reverse of the order of development found during developmental growth.

The distribution of subcutaneous fat between seven defined regions of the carcass was not affected by differences in total fatness in different physiological states. This, and the high correlation found between fat depth and total body fatness, confirms the view that measures of subcutaneous fat depth, e.g. by ultrasonics, should be useful predictors of the energy status of cows in varying physiological states.

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%.

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.

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.

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.

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.

Field experiments were conducted on four barley cultivars (two hulled and two hullless) grown under unirrigated conditions in Varanasi, India, to observe the effect of rate of application of nitrogen on copper concentration and uptake in plants and soils. The copper concentration in both plants and soil decreased with age of crop because of the dilution effect of more vegetative growth. Varieties did not differ in copper concentration of plants but increasing application of nitrogen decreased copper concentration in the plants. Since the hulled varieties yielded more than the hull-less ones, they removed more copper from the soil. Similarly yield was increased linearly by the application of N fertilizer and this led to a linear increase in depletion of available copper.

Pigeon pea (variety Cita-1) was sown on ridges at two plantings in the early and late seasons of 1983 at the University of Ibadan, Two to three weeks after the plants reached maturity and the pods had been harvested by hand-picking, the plants were either ratooned by cutting off the tops at a height of 30 and 60 cm or left intact.

At the end of the first and second regrowths, the plants ratooned at 30 and 60 cm had performed better than those left intact in terms of growth and yield characters as well as seed yield. However, the plants ratooned at 30 cm performed best followed by those ratooned at 60 cm. The total seed yield from the planting was 3–6 times higher than if the crop had been harvested once.

It would seem that ratooning at 30 cm would give the highest returns from a single planting under the prevailing lowland tropical conditions.

Effects of seven levels of N application and three seeds mixtures were studied on two sites for 4 years. One seeds mixture comprised perennial ryegrass (Lolium perenne L.) and two comprised perennial ryegrass with white olover (Trifolium repens L.). One site (Trefloyne) was 24 m above sea level on deep soil and the other (Pwllpeiran) was 328 m above sea level on relatively shallow soil. The plots were cut seven times per year.

The application of N to swards without clover considerably increased the number of ryegrass tillers as well as increasing ryegrass leaf blade length and width and sheath length. At Trefloyne the presence of clover greatly reduced the number of ryegrass tillers, had a greater positive effect on grass sheath length, relative to its effect on blade length and width, than that obtained by applying fertilizer N to a sward without clover, and tended to reduce grass leaf length during the winter. At Pwllpeiran the clover was less competitive, but it still tended to have a greater effect on sheath length and a less positive effect on numbers of tillers, relative to its effect on blade length and width, than that obtained by applying fertilizer N to a sward without clover. The application of N to grassolover swards increased the size of grass leaves and the number of tillers, but did not increase clover leaflet size. The number of olover leaves in the sward was greatly reduced by fertilizer N at Pwllpeiran, but was not affected by fertilizer N at Trefloyne. Blanca white clover had larger leaves than Aberystwyth S.100, but S.100 appeared to compensate for this by producing rather more leaves. In respect of number of leaves, leaf dimensions and rate of leaf emergence, clover appeared more sensitive than ryegrass to the differences between the sites. The leaf dimensions of the clover varied more from one time of year to another, but not from one year to another, than those of the ryegrass. The number of leaves per unit area of ground varied more in clover than in grass from year to year and from one time of year to another. The rate of emergence of leaves was faster in clover (per marked stolon tip) than in grass (per tiller).

The results on the influence of various crops in five different fixed rotations on the ohanges in nitrate and total N content of soils are reported. Groundnut contributed largely to the accumulation of nitrate nitrogen in the soil profile (to a depth of 120 cm). Bajra fodder exhausted the soil nitrogen reserve to a great extent. Wheat and maize, in a rotation, reduced nitrate leaching to deeper soil layers. Summer moong also left a large amount of unabsorbed nitrate in the profile. Total nitrogen content of the soil decreased after the harvest of cereals. Maximum depletion occurred after the harvest of bajra crop. Potato (a crop which received a heavy dressing of N fertilizer) and legumes contributed to the soil N reserve. A balance sheet of N indicated net gains of total soil N in four of the five cropping sequences. A net loss of 75 kg N/ha was observed in bajra fodder-potato-wheat rotation.

Three experiments examined the effects of sowing rate and between-row spacing on the plant density and yield of red beet.

The proportion of seeds which produced mature plants decreased when the mean distance to the nearest neighbour was less than 5 cm. In these experiments, this distance was governed by within-row spacing. Thus, plots with narrow-spaced rows achieved a higher plant density than those with wide-spaced rows, when sown with the same weight of seed.

Total yield of beet per unit area decreased with increasing plant density. Maximum yields per unit area of small beet were achieved at high plant densities, whereas maximum yields of large beet were achieved at low plant densities. The effect of between-row spacing on yield was much smaller than that of density, and was important only for crops harvested early. Shoot yield per unit area was measured in two experiments and was not affected by row spacing in either. Shoot yield was not affected by plant density in one experiment, but, in the other, tended to a maximum value with increasing plant density.

Growth rates were compared of pigeonpea (Cajanus cajan), moth bean (Vigna aconitifolia), mung bean (Vigna radiata) and sorghum seedlings aged 2–5 weeks. The seedling growth rates were analysed in relation to leaf area development, net photosynthetic rate, nitrogen accumulation, nitrate reductase activity, and soluble protein content. Growth rates were highest in sorghum and lowest in C. cajan. Leaf area development was very fast in sorghum and very slow in C. cajan. Net photosynthetic rate of sorghum leaves was double that observed for the legume leaves. No significant difference was observed in nitrate reductase activity, nitrogen percentage or soluble protein content between sorghum and the legumes. In sorghum, early investment of assimilates into leaf development ensured a higher assimilation of carbon and nitrogen per plant. In the legumes, slow development of leaf area coupled with low photosynthetic rates probably resulted in slow growth of the seedlings. In the legume seedlings, vigour was related to the rates of leaf area expansion. Leaf area expansion rates were not related to the nitrogen status of the leaf in the species examined.

The effects on emergence and growth of crisp lettuce seedlings as a result of sowing seeds at different depths and pressing them into the furrow bottom with a weighted seed press wheel were examined in three similar experiments in 1982, 1983 and 1984. Sowing depth had a considerable effect on percentage seedling emergence and the spread of emergence times but the pattern of response varied from year to year and appeared to be related to differences in soil moisture content. The most uniform emergence and the highest level of emergence were achieved by sowing shallowly (< 10 mm) with rainfall almost immediately after sowing then keeping the soil moisture content close to field capacity for 2 days. When rainfall or irrigation were delayed, drilling 15–20 mm deep gave more consistent results. Effects on seedling weight and variability of weight were associated with the time and uniformity of seedling emergence. Later emerging seedlings were lighter and a wide spread of emergence times gave seedlings of variable weight. There was virtually no effect on emergence of using additional weights on a seed press wheel.