Two experiments were run over a 3-year period in the central rainlands of Sudan under two systems of production, rainfed and irrigated, to assess the effects of system of production, inoculation and nitrogen fertilizers on plant and nodule development and grain yield of soya beans. Nodulated plants could fix more than 80 kg N/ha under irrigation whereas under rainfed conditions nodulation was neither effective nor efficient. Soya bean was responsive to nitrogen fertilizers under both systems of production giving significant increments in grain yields. Non-nodulating plants with added nitrogen fertilizers produced more total dry matter than nodulating plants during the vegetative phase until flowering time. At 2 weeks after flowering total dry-matter production for both types was equal and from then on to maturity nodulating plants outyielded non-nodulating ones in total dry-matter production. In 1979 and 1980 yield of irrigated nodulating soya-bean grain was 0·53 and 1·54 t/ha higher than rainfed yields whereas the difference in grain yields of the non-nodulating soya beans was 0·21 t/ha and zero during the same two seasons, respectively. There was a contrasting inverse relation between the number of nodules and dry weights under the two systems of production. Fewer and heavier nodules were produced under irrigation whereas under rainfed conditions nodulation was profuse and nodules were light. On the evidence available 1–4 g/m length of the granular form of soil implant inoculant (Nitragin), i.e. 16·6·66.4 kg/ha, is to be recommended for irrigated soya-bean production in Sudan.

A method of assessing genotypic stability is proposed in the case where genotype yields are measured across environments but no concomitant environment data are available. The method is introduced in a practical context and two examples of its use with actual data are presented.

The method depends ultimately on the choice of a suitable measure of similarity between genotypes. Most of the stability information appears in a sequence of plots, where stable genotypes are immediately highlighted as consistently more remote points.

A field experiment on an alkali soil (ESP 94) studied the effect of gypsum applied at 0, 2·5, 5 and 10t/ha and zinc sulphate applied at 0, 10, 20, 30 and 40 kg/ha on the growth, yield and chemical composition of rice. The effects of gypsum and zinc applications were additive. Optimum response of rice was to 10 kg zinc sulphate/ha at the 5 and 10 t/ha gypsum levels. At low levels of gypsum, plant growth was poor owing to toxicity of Na and/or deficiency of Ca, and higher levels of zinc sulphate gave a yield response. Zinc-deficient plants had significantly lower Zn concentration but higher concentrations of Fe, Mn, Cu, Ca and Mg than the healthy plants. Application of gypsum decreased the concentration of Na, Fe and Zn in rice plants and increased the concentration of Ca, K, Mn and Cu. in plots not treated with gypsum, the Zn concentration of plants was higher but grain yield was lower than that of gypsum-treated plots. Application of zinc increased the DTPA-extractable Zn but gypsum decreased the soil sodicity and DTPA-extractable Zn in alkali soils.

Three experiments, involving a total of 294 Israeli Holstein cows, were carried out to study aspects of the grouping of cows in relation to timing of changes and the type of complete diet given. In Expt 1, 40 cows were changed from a high energy diet to a medium energy diet either at 60 or at 180 days post calving. The results indicated a larger reduction in milk and FCM yield following the later than the earlier change of diet.

Experiment 2 involved 64 cows subjected to two treatments, one involving a ‘uniform’ diet (25:75 forage to concentrate D.M. ratio) and the other a ‘step’ treatment where the same diet as in treatment 1 was given for approximately 74 days and then changed to a diet of 35:65 forage to concentrate ratio. The results showed that it is not necessary to adopt different feeding systems according to the potential yield of the cow and that cows could be given rather lower energy diets within the range offered without loss of efficiency.

In Expt 3, involving 190 cows, the cows were divided into one of two feeding treatments, ‘uniform’ and ‘step’ similar to Expt 2 and the effect of potential yield and parity was considered. The results emphasized the importance of potential yield rather than feeding system in relation to yield. The results showed a shorter period from calving to conception for the ‘uniform’ treatment.

A strategy for efficient cow feeding is outlined.

Grain and straw yields of a range of spring barley cultivars were assessed in field experiments conducted from 1981 to 1983 in Northern Ireland. Mean straw yields varied between 2·75 t/ha in Inga and 1·94 t/ha in Golden Promise over the 3-year period. Both grain and straw yields varied from year to year, with straw production being more consistent for individual cultivars than grain yield. High grain yields were not associated with high straw yields, straw to grain ratios varying between 0·72 in Midas and 0·51 in Corgi. Neither grain yield nor straw length were good predictors of straw yield of cultivars. The role for and assessment of straw yield in cultivar evaluation is discussed.

Water-use efficiency and forage yield of irrigated oats depend to a large extent on water application during initial growth. Root distribution, growth and fodder yield of oats as influenced by time and amount of first irrigation were studied in the field for 2 years. Root-weight density of each layer, profile-root-weight density and yields decreased progressively when the first irrigation was delayed. Application of a small amount of irrigation (20 mm) at day 25 proved to be better than applications of 50 or 70 mm at later stages.

Six parental cultivars (Bragg, Bragg-black seed, Kalitur, Ankur, WT-125 and Glycine formosana), 15 F1's, eight F2's and eight F3's (Bragg × WT-125, Bragg × Glycine formosana, Bragg-black seed × WT 125, Bragg-black seed × Glycine formosana, Kalitur × WT-125, Kalitur × Glycine formosana, Ankur × WT-125 and Ankur × Glycine formosana) were evaluated for seed impermeability. WT-125 and Glycine formosana were identified as impermeable types (92·18, 77·46% impermeability, respectively). The other four varieties, namely Bragg (2·93% impermeable seeds), Bragg-black seed (11·7% impermeable seeds), Kalitur (no impermeable seeds) and Ankur (0·94% impermeable seeds) had soft seed or normal seed.

The segregation pattern for impermeability in the F2 and F3 generations of eight crosses showed the involvement of a pair of dominant genes in Bragg × Glycine formosana, Bragg-black seed × WT-125, and Bragg-black seed × Glycine formosana, three pairs of dominant genes in Bragg × WT-125, Ankur × WT-125 and Ankur × Glycine formosana, and four pairs of dominant genes in Kalitur × WT-125 and Kalitur × Glycine formosana for seed impermeability, assuming maternal control as hard seed was a seed-coat phenomenon.

Vr, Wr graphical analysis also indicated that WT-125 and Glycine formosana possessed mostly the dominant genes for seed impermeability, while the remaining four cultivars contained mostly the recessive genes. The correlation coefficient of Yr (parental mean) and Vr + Wr was negative and high (— 0·907) confirming that most of the dominant genes in the parental cultivars were acting towards high seed impermeability. Thus the overall results obtained through diallel analysis of 15 F1's were in agreement with those obtained through Mendelian analysis.

In Expt 1, 34 individually-penned Finn Dorset ewes of mean live weight 68 kg were synchronized in oestrus and mated to Suffolk rams. From mating until day 28 of pregnancy each received daily 15 MJ of metabolizable energy (ME) and 225 g crude protein (CP). From day 28 to slaughter on days 34, 41, 48 or 55 half of the ewes continued on this feeding regime and half had their daily intake reduced abruptly to 7·5 MJ of ME and 112 g CP. The mean number of ovulations per ewe was 4·03 (range 2–8) and the mean number of viable foetuses at time of slaughter 3·35 (range 2–6). The combined loss of ova (fertilization failure and early embryonic death) was 14·6% and detectable foetal deaths 2·2%. Level of feeding had no significant effect on these measures or on foetal growth. Foetal growth from 34 to 55 days was described by the equation

In w = 0·962–18·613 e-0·0272t–0·00091t(f–3),

where w = foetal weight (kg), t = age (days) and f = litter size. Within-litter variability measured as the S.D. of In w (kg) was 0–081 for twins, 0·108 for triplets and 0·106 for quadruplets and higher multiples.

In a second experiment Suffolk × Finn Dorset embryos were transplanted at the rate of two per uterine horn into 15 recipient Finn Dorset ewes. Embryo survival was 72% and foetal weights at 60 days varied from 67 to 146% of the mean value of 66 g. Withinlitter variation in foetal size was only about 70% of that expected for foetuses developing from the variable distribution in their initial positioning that occurs naturally. The correlation between foetal weight and placental weight at day 60 was 0·72 (P < 0001) indicating that the association between foetal weight and placental weight in prolific ewes is not confined to late pregnancy.

The results of both experiments are consistent with the hypothesis that the greater within-litter variability in birth weight in large litters is controlled by events in early pregnancy.

Six field experiments, three each during 1982–3 and 1983–4, were conducted on a sandy loam soil to study the effect of varying levels of nitrogen, phosphorus and potassium, in the absence and presence of farmyard manure (FYM) (30 t/ha), on the number of tubers and yield of potato in three grades. Increase in nitrogen, phosphorus and potassium application, in the absence or presence of FYM, did not significantly affect the total number of tubers/m2 but did affect the number of tubers in different grades. An increase in nitrogen and potassium significantly decreased the number of tubers/m2 in small (< 25 g) and increased in medium (25–75 g) and large (> 75 g) grades at 45, 60, 75 and 90 days after planting. Increase in the application of phosphorus increased the number of tubers/m2 in the small grade and decreased it in the large grade but did not affect the number in the medium grade. Increase in nitrogen and potassium application decreased the tuber yield in the small grade and increased it in the medium and large grades. Applied phosphorus increased the yield in the small and medium grades and decreased it in the large grade. The increase in the yield of tubers with increase in nitrogen and potassium application was found to be caused by an increase in the number of tubers in the medium and large grades at the expense of the small grade; however, with applied phosphorus the increase in yield was due to increase in the weight of individual tubers within the small and medium grades. FYM application decreased the number of tubers in the small grade and increased it in the medium and large grades. The response of potato to nitrogen increased and to phosphorus and potassium decreased with the application of FYM.

Testicular and epididymal sperm reserves were determined in six sexually mature Mujjafaranagri rams. The testes and epididymides weight were 151·4±5·49 and 20·7±0·164 g respectively. The total spermatids/g were 78±21·8×106, while daily sperm production per ram was estimated to be 4·46×109 when corrected for tunica albuginea weight. The number of spermatozoa in the caput, corpus and cauda epididymides were 3·18, 2·56 and 16·29×lO9 respectively and they represented 14·4, 11·6 and 73·9% respectively of the sperm reserves on that side. The total epididymal sperm reserve per male ram was about 44·06×109 spermatozoa.

The growth and grain yield of winter wheat were measured in plots which had been direct drilled, mouldboard ploughed or shallow-tine cultivated for 10 consecutive years. The experiment was carried out on a non-calcareous clay soil prone to winter waterlogging. In 1985 the crop grew well on all cultivations and grain yield, average 7–2 t/ha, was similar in all treatments and no adverse effects on wheat growth or on grain and straw yield were observed.

It was demonstrated that abiotic chemical precipitation could account for a major proportion of iron hydroxide deposition in drainage water. In filter-sterilized (0·22 μm) drainage water samples from ochreous sites 84% of the total iron in solution was precipitated within 48 h. It was also shown that ferric hydroxide precipitates could catalyse the precipitation of ferric hydroxides in drainage water exposed to the atmosphere.

Sheathed filamentous bacteria, Leptothrix spp. and Gallionella spp., were observed in ochre samples from sites in England and Wales. Thiobacillus ferrooxidans was found in acidic samples (pH < 4·0) and in ochre from drainage water of near neutral pH suggesting that it can contribute to ochre formation over a wide range of drainage water pH, Heterotrophic bacteria capable of growing in artificial media of low pH and complexdegrading heterotrophic bacteria were also isolated. Some ochre deposits could be described as either pyritic or filamentous but the majority of samples fell between these extremes and had various combinations of T. ferrooxidans, sheathed filamentous bacteria and other heterotrophic bacteria.

The characteristics of three fractions obtained by physical separation from each of 19 cattle slurries are reported, with the aim of investigating their behaviour in the soil. The fraction retained on a 1 mm sieve (F1) was the poorest in nutrient content. The fraction passing through a 1 mm sieve but retained in Richard's apparatus on a cellulose membrane of 2·4 nm pore radius (F2) contains most of the slurry's organic N and Pand most divalent cations (Ca2+ and Mg2+). F3, which passes through the cellulose membrane, contains most of the slurry's inorganic N and most monovalent cations.

The individual fractions are both chemically and physically much more homogeneous than the slurry as a whole, and their relative proportions are well correlated with the slurry's density and dry-matter content (P < 0·001), so that this kind of fractionation may confidently be expected to provide an analytical scheme facilitating research on the behaviour of slurry after its application to soil.

Results are described of an experiment involving various pearl millet–cow pea or green gram planting and interplanting systems under four levels of nitrogen and two levels of phosphorus. Planting of pearl millet in paired rows of 30 and 70 cm gave as much yield as normal planting in uniform rows of 50 cm. The productivity per unit area was increased considerably when pearl millet was interplanted with one row of cow pea or green gram. Cow pea gave higher yield than green gram. Nitrogen fertilizer increased pearl millet as well as intercrops yield significantly. Pearl millet responded up to 60 kg N/ha and intercrops up to 30 kg N/ha. Phosphorus fertilizer did not produce marked improvement in either growth or yield of pearl millet. Application of 40 kg P2O5/ha increased grain yield of intercrops significantly

Relations between yield, water use and pre-anthesis growth were analysed for cropsof barley grown for three seasons at several sites in northern Syria. The relations obtained were compared with those for other cereal crops grown in similar regions of Mediterranean climates.

Phosphorus fertilizer application increased the rate of crop development from emergence to floral initiation and advanced anthesis by up to 11 days. Grain and total shoot dry-matter yields were increased by fertilizer (nitrogen + phosphorus) applications at all sites in all years, in most cases without increasing total evapotranspiration. The increased dry matter at anthesis was produced without having used a larger proportion of the total evapotranspiration in the whole season. Consequently, the ratio of grain yield to total above-ground dry-matter yield (harvest index) and kernel weight were also relatively stable between sites and years, despite some very low amounts of post-anthesis water use. Grain yield appeared to be largely determined by anthesis and there were strong linear relationships between grain yield or total dry-matter yield and number of kernels. Differences in water use efficiency of crops given fertilizer between sites and years were closely related to the differences in amounts of winter growth.

Some responses differed from those predicted from models of growth, water use and yield developed in other regions with similar climates. It is concluded that agronomists and breeders should increase amounts of early growth thereby increasing grain and dry-matter yields. Future research emphasis should also be on the development of dynamic simulation models of pre-anthesis growth and water use.

Data are reported on a phenomenon in which piebald lambs having a coat of intermediate hairiness have black wool which is not only longer and coarser than the white wool on the same animal, but which has a different coat structure in terms of the fibre type array. Possible explanations for this effect which is apparently caused by the gene that restricts the production of pigment to certain areas of the skin are discussed. Hairy lambs and woolly lambs did not have this coat difference between the two colours.

The effects of four irrigation treatments on the growth and yield of poppies were studied in two ‘drought’ seasons in Tasmania. Irrigation increased total dry-matter production, leaf area index and delayed leaf senescence in both seasons. Irrigation, which continued until leaf senescence, increased total morphine yield by 5–20 kg/ha compared with no irrigation. This yield increase was attributed to the increase in the number and yield of lateral heads, the yield of terminal heads and capsule morphine concentration.

As the effects of irrigation on head yield reflect the effects on total dry-matter production, irrigation guidelines for poppies were developed from an analysis of plant growth during theseason. For maximum yield, one irrigation of 50 mm should be applied at the 50% hook stage, at 50% flowering, at the end of flowering and 2 weeks after the end of flowering. Growers who currently cease irrigation at 50% flowering can expect yield increases of 4–13 kg/ha ifthey apply two further irrigations thereafter.

Effects of plant density ranging from 44444 to 133333 plants/ha and tillage practices (planting in flat beds (control), in the furrows of open ridges, on the top of open ridges, in the furrows of tie-ridges and on the top of tie-ridges) on growth and grain yield of sorghum were investigated at Kobo, a typical semi-arid area in Ethiopia, during 1980, 1981 and 1982 cropping seasons. Plant growth was limited in the flat beds because they were likely to be deficient in soil moisture and sometimes in the tie-ridging treatments, due to waterlogging. However, planting on the top of tie-ridges produced 1·6, 0·4 and 1·8 t/ha more yield than in the flat beds, the method commonly practised by the Kobo farmers, during 1980, 1981 and 1982 respectively. In all seasons, the effect of plant density did not show marked differences. The plants rather adjusted their reproductive growth and development to the seasonal rainfall and presumably to the available soil moisture at the grain-filling periods. It was concluded that the highest plant density did not reach the optimum for the area. Planting sorghum on the top of tie-ridges is recommended.

Experiments were made over 2 years at two sites using three varieties to investigate the relationship between total yield, number of tubers > 1 cm and the yield of tubers in the 60–80 mmsize range. Regressionanalysisrevealed that yield of tubers in the 60–80 mm size range was a linear function of total yield and number of tubers > 1 cm. The effect of changes in tuber shape on this relationship is discussed.