A survey of soil and root samples collected beneath some pioneering plants colonizing reclaimed mine spoil at an opencast coal mine site at Chandrapur, Maharashtra State, India, was conducted in October 1994 to examine the possible host and edaphic influence on the occurrence of arbuscular mycorrhizal (AM) fungi. Thirteen plant species were sampled to determine the mycorrhizal root colonization and the number of spores of individual AM fungal species in the rhizosphere.

Typical AM fungal infection was observed in roots of all the plant species examined. Mycorrhizal infection ranged from 20 to 95%. Sampled soils contained six spore-forming species of AM fungi (Acaulospora scrobiculata, Entrophospora colombiana, Glomus aggregatum, Glomus ambisporum, Scutellospora calospora and a previously undescribed species of Glomus). Fungal spore densities were not related to the mycorrhizal infection levels. E. colombiana and G. ambisporum were the leading species in terms of spore densities and frequencies. Phenotypic variations in spores of AM fungi were possibly related to the physical and chemical properties of the mine spoil.

It is concluded that the pioneering plant species on mine spoils can cause the development of different populations of AM fungi. The study also indicates that certain species of AM fungi have broad environmental requirements.

The effect of seedbed conditions at the time of sowing on the grain yield and quality ex-farm of spring-sown malting barley was examined in three experiments in the south-east of Ireland in 1993–95. Blenheim malting barley sown in good seedbed conditions gave significantly (P<0·05) greater yields (3·1–9·6% more) than the identically treated crop, sown several days earlier, in less suitable seedbed conditions in all three experiments, but there was no effect on grain nitrogen content or the amount of screenings. The better soil conditions gave significantly (P<0·05) better plant emergence, a greater number of fertile tillers and more grains per ear.

The available world collection consisting of 257 accessions of the tropical pasture legume Centrosema brasilianum (L.) Benth. was assessed between 1993 and 1995 in northern Nigeria to complement existing knowledge on the genetic diversity of this species and to identify accessions with high agronomic potential for subhumid west Africa. The excellent nutritive value and good dry matter productivity of C. brasilianum and its outstanding ability to remain green over extended dry periods confirmed its potential as an important forage resource, especially for the dry season, and indicated its possible role in soil conservation. Two distinct groups, comprising 10 and 11 accessions, were identified for further evaluation in short fallow and pasture systems, respectively. Accessions in the first group had a fast establishment, very high yields in the establishment year and good drought tolerance but yields were low to average in subsequent years. Accessions in the second group had sustained high yields under grazing, a high competitive ability and good drought tolerance.

The poor viability of the perennial aromatic grass, palmarosa (Cymbopogon martinii Stapf. var. motia), in the first year of planting, restricts its popularity among farmers in India. Two pigeonpea cultivars, Bahar (late maturing), and UPAS–120 (early maturing) were intercropped at different row spacings with palmarosa at a row spacing of 60 cm, in the subtropical climate of Lucknow, north India in 1988/89 and 1989/90. Intercropping with the late maturing cv. Bahar at 300 cm row spacing produced 1·26 t/ha grain (2-year mean) without affecting the growth and yield of the palmarosa. Intercropping improved land-use efficiency by 47%, relative net return by 58% and net economic return by Rs. 12500/ha over a sole palmarosa crop. The grain, stalk and total dry matter yield per plant of pigeonpea was considerably improved when grown at the wider row spacing in the intercropped system than when grown as a sole crop. This indicates that the competition between pigeonpea plants was not reduced when palmarosa was present. Palmarosa tiller production and herb and oil yield were significantly reduced when the distance between rows of pigeonpea was narrowed, demonstrating both the greater susceptibility of palmarosa to lack of light, and also that in palmarosa–pigeonpea intercropping systems, competition exists mainly for light rather than for nutrients and moisture, possibly because the two crop components acquire their nutrients and moisture from different soil layers.

Intercropping with the high yielding, late maturing pigeonpea cultivar, Bahar, at 300 cm row distance is recommended to make palmarosa cultivation economically viable in the first year of planting. The selection of high yielding, late maturing pigeonpea cultivars with an upright growth habit is suggested as a further way of improving the economic benefits of a palmarosa–pigeonpea intercropping system.

Laboratory studies on the biology of oilseed rape (Brassica napus L.) showed that the induction of secondary dormancy is influenced by light environment, time of exposure to light and darkness, temperature regime and genotype. Seeds did not become dormant while exposed to light but were increasingly likely to become dormant the longer they were exposed to water stress and darkness. Dormancy was broken by alternating warm and cold temperatures.

Conclusions from results obtained in Petri dishes have been tested in the field and hypotheses regarding the effects of post-harvest cultivation have been proposed. In July 1995, field experiments were initiated on a flinty silty clay loam and a sand to test the implications of post-harvest cultivation on the development of a persistent seedbank. The results largely confirmed assumptions made on the basis of laboratory findings. Seeds that had been exposed to water stress and darkness for longest, by cultivating the soil at the beginning of the experiment, immediately after seed distribution, exhibited the highest persistence rates. Seeds that were exposed to light for 4 weeks and then incorporated into the soil built up a much smaller seedbank. The seedbank was very small or nonexistent in plots that had not been cultivated at all.

In NW Europe, autumn-grown oilseed rape normally receives nitrogen (N) in autumn as seedbed N and in the spring as a split application at the beginning of growth and at stem elongation. In the growing seasons 1990/91 to 1992/93, the effects of slurry and mineral N fertilization on yield, N uptake by the seed and apparent N-use efficiency (NUE) by oilseed rape (Brassica napus) were investigated in a factorial field experiment at Hohenschulen Experimental Station near Kiel, NW Germany. The crop rotation was oilseed rape–winter wheat–winter barley, and soil tillage (conservation tillage without ploughing, conventional tillage), application of pig slurry (none, autumn, spring, autumn+spring) and mineral N fertilization (0 to 200 kg N ha−1) were all varied. Each year, the treatments were applied to all three crops of the rotation and were located on the same plots.

Between the years, average seed yield ranged from 3·04 to 3·78 t ha−1, while the corresponding N uptake by the seed varied from 107 to 131 kg N ha−1. Slurry application in spring increased the seed yield and N uptake by the seed in all years, whereas the effect of autumn slurry alone or in combination with spring slurry was negligible. Mineral N fertilizer increased seed yield and N uptake by the seeds except in 1991/92, when N amounts exceeded 160 kg N ha−1. No significant slurry×mineral N interaction occurred. Apparent NUE of mineral N was larger than that of slurry N, but decreased with increasing mineral fertilizer N rates. Only 5% of the autumn slurry N was apparently utilized by the seeds, compared with 24% of the spring slurry N.

Despite its ability to take up substantial quantities of N before the winter, oilseed rape utilized very little autumn slurry N for seed production. To minimize environmental impacts, slurry should be applied in the spring, when plants are more able to use N for yield formation, even if NUE of slurry N is lower than that of mineral N. However, since NUE changes with the amount of applied N, it is difficult to find the best combination of slurry and mineral N fertilization to avoid negative environmental effects.

The occurrence of vesicular–arbuscular mycorrhizae (VAM) root colonization and spore number in soil was assessed for 18 fields under intensive lettuce (Lactuca sativa L.) production in California during July and August of 1995. Data on management practices and soil characteristics were compiled for each field, and included a wide range of conditions. The relationship between these factors and the occurrence of VAM in these fields was explored with multivariate statistical analysis. VAM colonization of lettuce tended to decrease with the use of chemical inputs, such as pesticides and high amounts of P and N fertilizers. Addition of soil organic matter amendments, the occurrence of other host crops in the rotation, and soil carbon[ratio ]phosphorus and carbon[ratio ]nitrogen ratios, were positively associated with VAM colonization of lettuce roots. The number of VAM spores in soil was strongly correlated with the number of other host crops in the rotation, the occurrence of weed hosts and sampling date, but was more affected by general soil conditions than by management inputs. Higher total soil N, C and P, as well as CEC, were inversely related to soil spore number. A glasshouse study of the two primary lettuce types sampled in the field showed no significant differences in the extent of root colonization under similar growing conditions. The results of this study are compared with other studies on the effects of management and soil conditions on mycorrhizal occurrence in agriculture.

Slurry was collected from two groups of finishing pigs fed either a standard commercial diet (containing 205 g/kg crude protein (CP)) or a specially formulated lower CP content diet (140 g/kg CP). The slurries were surface applied to grass/clover plots on a freely draining soil in SW England in mid-March 1995 at three application rates: 25, 50 and 70 m3/ha. Measurements were made from the 50 m3/ha plots of ammonia volatilization, denitrification, nitrous oxide and methane emissions and nitrate leaching. Measurements of herbage yield and apparent N recovery (ANR) were made from all plots. Decreasing the CP content of the pigs' diet reduced N excretion by the pigs and also changed other characteristics of the slurry. Slurry from pigs fed the lower CP diet (the slurry referred to hereafter as LS) had a higher dry matter (DM) content, lower pH, lower total ammoniacal N (TAN), total N and VFA content with a similar total C content compared with slurry from pigs fed the standard commercial diet (the slurry hereafter referred to as CS). From the 50 m3/ha treated plots, losses by ammonia volatilization represented 38 and 58% of the applied TAN and net losses through denitrification represented 5·3 and 12% of the applied TAN for LS and CS respectively. Nitrous oxide emission was similar from the two slurries, with net emissions of c. 0·5% of the applied TAN. Methane emission was significantly less from LS. No nitrate leaching was detected either in spring or in the following autumn. Yield and ANR increased with increasing slurry application rate up to 50 m3/ha. The best% N recovery was from the 50 m3/ha application rate with 58 and 47% of the applied TAN being recovered from LS- and CS-treated plots respectively. Changes in the slurry characteristics due to the lower CP diet resulted in lower losses to the environment and an improved utilization of the slurry N by the herbage.

Two experiments each with two rates of feeding (maintenance and twice maintenance) were conducted during summer 1993/94 (Expt 1) and summer 1994/95 (Expt 2), at Massey University, New Zealand. Four sambar and four red deer, including stags and hinds aged 10–14 months, were used in each year. Animals were fed a pelleted diet (total N 30 g/kg DM; NDF 247 g/kg DM). Digestibility and nitrogen (N) balances were determined using deer metabolism cages, whilst methane production and heat production were determined using open circuit respiration calorimetry, with measurements made on each deer at both rates of feeding. Digestibility and metabolizability of energy were greater for sambar than for red deer in Expt 1 but not in Expt 2. Nitrogen retention, expressed as a proportion of N intake, was similar for sambar and red deer. Metabolizable energy required for maintenance (MEm) was 474 kJ kg W−0·75 d−1 for sambar deer and 567 kJ kg W−0·75 d−1 for red deer, whilst the efficiency of utilization of ME above maintenance (kg) was similar for sambar deer and red deer. These studies indicated that the sambar deer had lower rates of maintenance heat production than the red deer, which may explain the sambar's superior feed conversion measured in previous experiments. However, the two species utilized nitrogen with similar efficiency, when fed a high quality ration.

Sorghum grain was included in a basal diet of molasses (molasses 505, urea 21, sunflower meal 191, pangola grass hay 250, minerals 31 g/kg as fed) at rates of 0, 202, 391 and 707 g/kg, generating diets in which grain replaced 0 (diet A), 33 (diet B), 66 (diet C) and 100% (diet D) of the molasses and hay. The four diets were fed to groups of four Hereford steers (293–334 kg liveweight) over a 96-day period. One half of each treatment group was implanted with a growth promotant (zeranol), and all were slaughtered at a commercial abattoir at the end of the trial. The inclusion of 33% grain increased voluntary feed consumption, digestible dry matter (DM) intake (from 57·6 to 82·0 g digestible DM/kg0·75 per day and significantly increased liveweight gain from 592 to 900 g/day. Zeranol implantation also increased liveweight gain but not feed intake. Steers given only grain (diet D) had the highest liveweight gains (1127 g/day). The addition of grain to molasses diets decreased urinary N excretion and increased ammonia and volatile fatty acid (VFA) concentrations in rumen fluid. Molar proportions of propionic acid in total VFA increased from 0·15 to 0·20, and butyric acid decreased from 0·36 to 0·29 when 33% of the molasses was replaced by sorghum grain. The fat content (depth at sacral position) of the carcasses of steers given grain only (diet D) was significantly greater (14 mm) than that of steers given the basal diet of molasses (4 mm), and carcass fat contents were intermediate (10 and 11 mm) for steers given diets B and C respectively. It was concluded that the inclusion of small amounts of grain in molasses-based diets increased cattle growth principally by increasing digestible energy intake without decreasing molasses intake, thus improving the efficiency of utilization of molasses in molasses-based diets.

An experiment was conducted to investigate the effects of supplements of sorghum grain (1·1 kg/day), sodium propionate (65 g/day) and intra-abomasal glucose infusion (200 g/day) on the liveweight gain (LWG), glucose metabolism and nitrogen utilization of Hereford steers (four per group) given molasses-based diets ad libitum (molasses 589, urea 18, sunflower meal 194, pangola grass hay 187, minerals 12 g/kg as fed). There was no significant effect of treatment on voluntary feed consumption (97–106 g dry matter (DM)/kg0·75 per day) or DM digestibility (0·564–0·579). The LWG of steers given grain supplements (899 g/day) and sodium propionate (943 g/day) were significantly (P<0·05) higher than those of steers given the basal diet (741 g/day) and basal diet plus glucose infusion (794 g/day).

All supplements decreased plasma urea concentrations and urinary N excretion and increased the efficiency of N utilization from 0·19 to 0·36–0·38 g N retained per g apparently digested N intake. The provision of grain (13% DM intake) increased ammonia and volatile fatty acid (VFA) concentrations in rumen fluid, and both grain and sodium propionate increased the proportion of propionic acid in ruminal VFA. Grain supplementation and glucose infusions significantly (P<0·05) increased glucose entry rates (g/day and g/kg0·75 per day) without affecting plasma glucose concentrations or glucose pool size and space. Sodium propionate supplements increased plasma insulin concentrations to a lesser extent than grain supplements and glucose infusion. Increased glucose availability in the present studies was associated with an improved utilization of dietary protein and, in some cases, with improved LWG.

The aim of the study was to investigate the changes in renal function in late pregnant and early lactating Corriedale ewes. Compared with the non-productive state, plasma urea concentration was increased by 67% during pregnancy, whereas it decreased by 36% during lactation. Urine flow, urea clearance, renal plasma flow and glomerular filtration rate were significantly reduced (P<0·05) during both late pregnancy and early lactation. Filtered load of urea and the amount of urea eliminated were significantly reduced (P<0·05) only in lactating ewes. No changes were noted in the fractional excretion of urea, the filtration fraction and the urine osmolality during both late pregnancy and early lactation. It was concluded that, as in other breeds, Corriedale ewes can adapt to increased nitrogen requirements during late pregnancy, and especially during early lactation, by increasing the renal conservation of urea. Unlike other breeds, however, Corriedale ewes restrict the urine urea losses mainly by reducing renal plasma flow and glomerular filtration rate, without any modification of the tubular reabsorption of urea during both late pregnancy and early lactation.

First-harvest, precision-chopped Lolium perenne grass with a dry matter (DM) content of 132·0 g/kg and water-soluble carbohydrate (WSC) and crude protein (CP) contents of 24 g/kg and 106 g/kg DM, respectively, was ensiled in farm scale silos following the addition of formic acid (FA) (2·5 l/t) or molassed sugarbeet pulp (MSBP) (50 kg/t). Mature twin-bearing ewes (n=56) were allocated to one of seven treatments and offered either FA-treated silage or MSBP silage ad libitum. The trial commenced on day 91 of pregnancy, when the ewes were offered FA-treated silage (T1), FA-treated silage+soyabean meal (T2), MSBP silage (T3), MSBP silage+soyabean meal (T4), FA-treated silage+MSBP (T5), FA-treated silage+MSBP+soyabean meal (T6) or FA-treated silage+a barley-based supplement (150 g CP per kg DM) (T7, control). Soyabean meal supplementation was only offered in the last 3 weeks of pregnancy, with the objective of achieving a total CP intake of 220 g/ewe per day. Compared with the FA-treated silage, the MSBP silage had a higher nitrogen content (P<0·01) and a lower neutral detergent fibre (NDF) content, but the two silages did not differ in DM, acid detergent fibre (ADF) or gross energy contents. Silage DM intakes (SDMI) were higher on the MSBP silage-based diets (T3, T4) than for any other treatment (P<0·05). The addition of soyabean meal significantly increased SDMI in T2 in the last week of pregnancy (P<0·05), but there was no response in SDMI to soyabean meal supplementation in any of the other treatments. Ewe liveweight changes (kg) of −0·4, 4·1, 7·8, 10·2, 7·1, 9·6 and 10·8 (S.E.±1·2), body condition score changes of −0·96, −0·59, −0·42, −0·33, −0·37, +0·01 and −0·27 (S.E.±0·1) and total lamb birth weights (kg) of 8·0, 8·7, 9·2, 9·9, 8·6, 8·0 and 10·4 (S.E.±0·5) were recorded for ewes in T1 to T7 respectively.

A study was conducted to examine whether oilseed cakes (cottonseed cake (CSC) or noug (Guizotia abyssinica) cake (NSC)) are complementary to the bird-resistant (BR) and non-bird-resistant (NBR) varieties of sorghum stover and whether sheep select against morphological fractions containing high concentrations of tannins or proanthocyanidins (PA). Either 24 (growth study) or 16 (metabolism study) Ethiopian Menz sheep were used in a randomized complete block design to study the interaction of variety of sorghum stover with type of oilseed cake on feed selection, intake, digestibility, microbial protein synthesis, nitrogen (N) retention and growth. The degradability of the feeds and refusals was also determined. The NBR variety was more degradable than the BR variety during the early hours of incubation. NSC degraded faster, although to a lesser extent than CSC. Stover variety had no effect on ruminal ammonia concentration (RAC) while CSC induced a higher RAC than NSC did. Sheep given the NBR variety had more dust, less heads, less leaf, less sheath and more stem in their ingesta than those fed on the BR variety. It was seen that the sheep discriminated against the stems, since the ratio of stem in ingesta to stem on offer was <1. Since PA are more highly concentrated in the sheath than in any of the other plant fractions, it appears that the choice of the morphological composition of the ingesta by sheep was not determined by PA. Sheep selected a diet which was 2–5% or 5–11% more degradable than the offered or refused feeds, respectively. Relative to NSC, CSC enhanced the intake of N, N bound to neutral detergent fibre (NDF), digestibility and N retention and tended to increase (P<0·06) liveweight gain (LWG) and organic matter (OM) intake but had no effect on microbial protein synthesis. Compared with the NBR variety, the BR variety depressed N digestibility and N retention, had no effect on microbial protein synthesis and on LWG, but depressed the efficiency of LWG by c. 30%. Sheep given the BR+NSC diet had the lowest daily gain but excreted copious amounts of urine, probably in an attempt to eliminate toxic waste substances. Since sorghum is a crop of the semi-arid regions, it is quite likely that, although the bird resistance trait increases crop yield, it has resulted in a feed that is rather less suitable for livestock in this production environment, where water shortages are frequent. In-depth studies on the consequences of water shortage on the utilization of bird-resistant sorghum stover are required.

Increasing the dietary intake of K reduces the Mg absorption from the forestomachs of ruminants by decreasing the apical membrane potential and increasing the transepithelial potential difference (Vt). To evaluate genetic variations in the dependence of Mg absorption on K intake, we performed Ussing chamber experiments and studied the effect of Vt on 28Mg fluxes across rumen epithelium from different breeds of sheep. All breeds showed net absorption of Mg (JMgnet) in the absence of electrochemical gradients. JMgnet of Skudde was lower compared to Merino or Schwarzkopf sheep. Increasing Vt decreased mucosal to serosal Mg flux (JMgms) and increased serosal to mucosal Mg flux. The effect of Vt on JMgnet was almost identical in all breeds of sheep (−30 to −45% for a 25 mV increase in Vt). The effect of Vt on JMgms revealed a Vt-dependent and a Vt-independent component of transcellular Mg absorption in all breeds. Considering the driving forces for these two Mg transport mechanisms, the effect of K on Mg absorption will mainly depend on the feeding regimen, i.e. dietary K must have a relatively higher effect on Mg absorption at low Mg intake levels, which explains the correlation between pasture quality and tetany frequency as well as the missing effect of K on Mg status in some older studies.