A restricted randomization procedure for self-conjugate 5 × 5 Latin squares is shown to be useful for trials on intercropping, particularly agroforestry, as records from border plots need no longer be discarded.

Use of an alpha-lattice design in 714 international yield trials of barley, durum wheat and bread wheat in 1990/91 to 1992/93 resulted in an average efficiency 18% higher than the randomized complete block design when average variance was used as the comparison criterion. Alpha-lattice was generally most efficient when the C.V.s of the trials were high. It was also slightly more efficient for low-yielding than for high-yielding trials, and for rainfed than for irrigated trials. Since the changeover to alpha-lattice designs requires no new major input or changes in present field layout, its use for international trials is recommended.

Four sets of near-isogenic lines carrying different combinations of the alleles Rht-B1b, Rht-D1b and Rht-B1c for gibberellin-insensitive dwarfism in hexaploid wheat (Triticum aestivum L.) were compared with tall controls in a series of yield trials in eastern England and central Germany. In all four varietal backgrounds the effects of Rht-B1b and Rht-D1b were similar (plant height ≈ 86 and 83% of tall controls respectively) and in combination reduced plant height to c. 58%. The Rht-B1c allele caused more severe dwarfism (c. 50%) and, when combined with Rht-D1b, reduced plant height still further to c. 41%.

Data from the trials were consistent with a model for height/yield relationships in which the pleiotropic effects of the Rht alleles on yield can be inferred from their primary function: insensitivity to gibberellin limits stem extension growth, decreasing assimilate demand for this organ and diverting it to the developing ear (which is not itself dwarfed). The net balance between the resulting increase in harvest index and the curvilinear relationship observed between plant height and total shoot yield results in optimum grain yields at intermediate plant heights.

Yield advantages of shorter plants over tall controls were evident over several trials with mean grain yields ranging from 200 to 760 g m−2. The optimum plant height for yield improvement in different genetic backgrounds was achieved by different Rht alleles according to the background varietal height, such that intrinsically taller genotypes required more potent Rht alleles to achieve maximum potential grain yield.

Ear yield components showed increases in grain number due to Rht pleiotropy, from which it is inferred that the number of grains per ear is limited by supply of assimilates pre-anthesis. Increases in grain number were associated with decreases in mean weight per grain which varied according to severity of dwarfism and varietal background, so that the net effect on grain yield per ear was sometimes positive, sometimes negative, and sometimes neutral in different Rht/variety combinations.

Agroclimatic conditions in the UK are not ideally suited to maize (Zea mays L.) as a grain crop. An alternative growing technique to direct-seeded maize was investigated at Reading University over three growing seasons, using four cultivars (Bastion, Ace, Anko and Mirna) of different FAO maturity ratings. In the main trials conducted in 1989 and 1990, seedlings were raised for 15–45 days in a glasshouse and planted in the field between early May and mid-June, at 10 plants/m2. On each planting date, maize kernels of the same cultivars were also sown in the field. At the end of each growing season, transplanted and direct-seeded crops were assessed for grain maturity and grain yield components. Averaged over year and cultivar, transplants matured significantly earlier than direct-seeded maize and tended to give higher grain yields. Their grain dry weights (86% DM) averaged 7·0 t/ha in a preliminary study in 1988, 9·0 t/ha in 1989 and 6·1 t/ha in 1990, whereas those of direct-seeded maize averaged 4·0, 8·0 and 3·0 t/ha, respectively. The highest grain weights resulted from May plantings using 15-day-old seedlings of the late cv. Mirna, and from June plantings using 30-day-old seedlings. Yield benefits from transplanting were not significant in 1989, suggesting that in a very warm season transplants may not necessarily outyield direct-seeded crops. Differences in grain weight between transplanted and direct-seeded maize are discussed with respect to grain moisture content, 1000-grain weight, ear length, and number of grains and grain rows per ear; and applications of maize transplanting for cropping systems are outlined. It is concluded that suitable combinations of cultivar, transplant age at planting and planting date can meet the thermal time requirement for a grain harvest in southern England.

Maize seedlings (cultivars Bastion, Ace, Anko and Mirna) were raised for 15, 30 or 45 days in a glasshouse and planted in the field between early May and mid-June in 1989 and 1990, at 10 plants/m2. Samples of transplants and direct-seeded crops of the same cultivars were taken at regular intervals throughout the growing season for growth analyses. In both years, the 15-day-old transplants established more rapidly in the field than older transplants, and the patterns of leaf production of these young transplants were similar to those of direct-seeded maize. Transplants flowered earlier than direct-seeded maize from the same planting date. At most harvests, transplants showed significantly higher dry weights than their direct-seeded counterparts, and May-planted maize had significantly higher dry weights than June-planted crops, while cultivar effects were small. Final biomass yields were consistently higher in 1989 (17 t/ha) than in 1990 (11 t/ha). In both seasons, particularly in 1990, there was a trend for a lower harvest index in direct-seeded maize which reflected its immaturity at final harvest. The lowest harvest index (0·07) in 1990 was recorded for direct-seeded maize of the late cultivar, Mirna (June planting), the highest harvest index (0·65) for 30-day-old Mirna transplants (May-planted). A comparison of the experienced effective temperature sums during the vegetative, reproductive and grain-filling phases suggested that the transplant nursery period provides an advancement in thermal time which can affect grain-filling and crop maturity. Year to year variation in climate seems to be of primary importance for yield advantages of transplanted over direct-seeded maize.

Maize kernels were soaked for 16 h in solutions containing the growth regulators BAS 106.W at 40 or 80 mg/l, PP333 at 80 or 160 mg/l, or BNO 0184 at 100 or 150 mg/l. The plant growth regulator (PGR)-treated kernels and water-soaked controls were sown in planting trays, and seedling transplants were raised in a glasshouse for 24 days. When they were planted in the field, the PGR-treated plants were significantly shorter than controls, with average plant heights (measured from soil level to uppermost leaf collar) of 4·7 cm (BAS 106.W, 40 mg/l), 3·7 cm (BAS 106.W, 80 mg/l), 6·1 cm (PP333, 80 mg/l), 8·0 cm (PP333, 160 mg/l), 6·4 cm (BNO 0184, 100 mg/l), 7·1 cm (BNO 0184, 150 mg/l) and 11·0 cm (controls). The dwarfing of PGR-treated transplants was mainly due to shortened leaf insertions of the lower leaves. Shoot weights were little affected by PGR-treatment, since decreased plant heights were partly compensated for by thicker stems and broader leaves. PGR effects on leaf numbers were negligible. At crop maturity, PGR-treated plants and controls showed similar grain weights and harvest indices. A partial leaf removal treatment at planting using untreated seedlings was associated with rapid crop establishment in the field and like the PGR treatments, it had no significant effect on final yield. It is suggested that a PGR-treatment with a short term dwarfing effect would facilitate the production and handling of maize seedling transplants and may improve establishment and early growth in the field.

Forages produced in the north central interior of British Columbia are low in percentage crude protein (CP). Growing lucerne (Medicago sativa L.) should increase forage percentage CP, but many of the soils are considered too acidic for this species. The objective of three field experiments, conducted at the Prince George experimental farm, was to evaluate management practices that might accommodate the growth of lucerne on acid soils without the expense of liming. Experiment 1 compared three legume species (lucerne, alsike clover (Trifolium hybridum L.) and red clover (T. pratense L.)), preinoculated lime-coated seed (GNRTM, Grow Tec Ltd, Nisku, Alberta), and soil liming on root nodulation and forage dry matter (DM) yield. Experiment 2 compared lucerne genetic lines, seed preinoculation and soil liming on root nodulation and forage DM yield and percentage CP. Experiment 3 compared lucerne rhizobia genetic strains, seed preinoculation and soil liming on root nodulation, forage DM yield and percentage CP.

For effective nodulation, lucerne required seed preinoculation, whereas alsike clover and red clover did not. Lucerne persisted longer than alsike or red clover. In Expts 2 and 3, the combination of lime and preinoculation increased lucerne DM yield by 136% and %CP from 9·2 to 15·4. The addition of lime alone increased lucerne DM yield by an average of 130% and %CP from 9·2 to 16·3. With preinoculation alone, lucerne DM yield increased by 100% and %CP increased from 9·2 to 12·7. Although using preinoculated lime-coated seed alone is not as effective as lime alone, coated seed may be the preferred method, based on ease of application and cost. Neither the six lucerne lines nor the three rhizobial strains evaluated resulted in improved root nodulation under acidic conditions.

In field trials in 1987/88 near Pangbourne, England, wheat (Triticum aestivum) and field beans (Vicia faba) were grown in an organic farming system as sole crops and additive intercrops. The sole crops were grown at 25, 50, 75, 100 and 150% of the recommended density (RD) for conventionally grown crops. The intercrops consisted of all density combinations of wheat and beans from 25 to 100% RD in a factorial experiment. The grain yield of sole cropped wheat and beans increased significantly as their density was increased. The highest yield of both was achieved at 100% RD, indicating that the conventional recommendation was the optimum when applied to organically grown crops. Land equivalent ratio (LER) values for the intercrops were significantly greater than 1·0 when the wheat was sown at > 5% RD and beans at > 50% RD. The highest LER of 1·29 was achieved when wheat and beans were both sown at 75% RD. There was resource complementarity, expressed as relative yield total (RYT) > 1·0, in all of the density combinations. There was a significant decrease in resource complementarity with increasing wheat and bean density. The nitrogen content of the wheat grain and whole plant biomass was significantly increased when the density of beans in the intercrops was increased; this was reflected in a significant increase in grain protein at harvest. The total amount of N accumulated by the wheat, however, decreased with increasing bean density due to a reduction in the biomass of wheat. Beans also showed a significant increase in %N as the density of the other component increased and a decrease in total N accumulation due to reduced biomass. All of the intercrops accumulated more N than the sole cropped wheat, but did not exceed that accumulated by sole-cropped beans. The biomass of weeds was greater under beans than under wheat. Weed biomass in intercrops was significantly reduced when the density of wheat and beans was increased, resulting in a lower weed biomass in the intercrops than was achieved in either the sole cropped wheat or beans. The N content of weeds was significantly reduced with increasing wheat density but was significantly increased with increasing bean density. The total amount of N accumulated by weeds per unit area was reduced significantly by increasing the density of both components. The levels of disease on the wheat were low, but mildew (Erysiphe graminis) increased significantly as bean density increased. The incidence of chocolate spot (Botrytis fabae) increased significantly with increased bean density. The experiment demonstrated that it was possible to harvest the crop with a combine harvester and the wheat and beans can be planted separately mechanically, therefore this system is suited to mechanized agricultural systems.

Urediospores of U. viciae-fabae (broad bean rust) germinated well in the range 5–26 °C, with fastest germination at 20 °C. Exposure to 30 °C gave poor germination and damaged the spores. Infection of Vicia faba leaves depended on a moisture film. At 20 °C some infection occurred with only 4 h leaf wetness, but longer wet periods up to 24 h gave increased infection. At lower temperatures, the infection process was slower and final pustule numbers were smaller. Spore germination was delayed by daylight and by all artificial light sources that contained far-red (700–800 nm) wavelengths. The delay was increased at higher light intensities. When spores were subjected to alternating periods of light and darkness, it was found that 40 min of darkness was sufficient for the irreversible induction of germination at 20 °C.

Nitrogen (N) fertilizer not used by the crop can increase the risk of nitrate leaching into the groundwater. In two growing seasons, 1990/91 and 1991/92, the relationships between N fertilization and yield, N uptake by the grain and the N leaching in the subsequent percolation period were investigated in a multifactorial field experiment at Hohenschulen Experimental Station near Kiel in NW Germany. The crop rotation was oilseed rape – winter wheat – winter barley, and effects of soil tillage (minimum tillage without ploughing, conventional tillage), application of pig slurry (none, application in autumn, application in autumn and in spring), mineral N fertilization (none, 80 or 200 kg N ha−1 to oilseed rape and 120 or 240 kg N ha−1 to cereals) and application of fungicides (none, intensive) were all tested. In each year, the rotation and the treatments were located on the same plots. Mineral N fertilization and fungicide application increased yield and N uptake by grain or seed in all crops. In contrast, the application of slurry, especially in autumn, had only small effects on yield and N uptake. Nitrogen losses by leaching (measured using porous ceramic cups) were affected mainly by the year and the crop. In 1992/93, averaged over all factors, 80 kg N ha−1 was leached compared with 28 kg N ha−1 the previous year. Oilseed rape reduced N losses, whereas under winter wheat up to 160 kg N ha−1 was leached. Due to a lower N-use efficiency, autumn applications of slurry increased N leaching, and mineral N fertilization of the preceding crop also led to higher N losses.

Since the amount of leached N depends both on the nitrogen left by the preceding crop (unused fertilizer N as well as N in residues) and on N uptake by the subsequent crop, it is not possible to apportion the N losses to any particular crop in the rotation. The cropping sequence, together with its previous and subsequent crops, must also be considered.

To minimize leaching, N fertilization must meet the needs of the growing crop. In order to improve the efficiency further, investigations must be conducted in order to understand the dynamics of N in the plant–soil system in conjunction with the weather and crop management practices.

Pure swards of chicory (Cichorium intybus) and perennial ryegrass (Lolium perenne) were grown at Palmerston North, New Zealand. They were cut daily and fed hourly at 2·25 kg dry matter (DM)/day to eight hand-reared, rumen-fistulated castrated red deer stags kept in metabolism crates during December 1994 and January 1995 (summer). Apparent digestibility, rumen fractional disappearance rate (FDPR), rumen fractional degradation rate (FDR), rumen fractional outflow rate (FOR) and mean retention time (MRT) were measured. The ratio of readily fermentable carbohydrate to structural carbohydrate was approximately three times higher in chicory than in perennial ryegrass. Apparent digestibility of DM was higher in deer fed chicory than in deer fed perennial ryegrass (0·785 v. 0·727), whilst apparent digestibility of neutral detergent fibre (NDF) was lower in deer fed chicory (0·679 v. 0·755), due to a reduced hemicellulose digestibility (0·667 v. 0·783). Relative to deer fed perennial ryegrass, those fed chicory had higher rumen FDPR values for DM (14·5 v. 8·6%/h), soluble carbohydrate (69·9 v. 54·7%/h), cellulose (15·5 v. 9·8%/h) and lignin (6·8 v. 3·8%/h). Rumen FDR in deer fed chicory was higher than those fed perennial ryegrass for cellulose (11·4 v. 7·0%/h) and lignin (2·7 v. 1·0%/h), but tended to be lower for hemicellulose. Rumen FOR was higher and MRT was lower for both liquid and particulate matter in deer fed chicory compared to deer fed perennial ryegrass.

It is concluded that rumen FDPR and apparent digestibility were much higher in deer fed chicory than in deer fed perennial ryegrass, due to faster degradation rates of most constituents in the rumen and faster outflow rates from the rumen. An exception was hemicellulose, where reduced rumen degradation rates and shorter rumen particulate MRT contributed to reduced apparent digestibility. Faster clearance from the rumen, due to both faster degradation and outflow rates may be used to explain the greater voluntary feed intake (VFI), as well as faster growth rate in deer grazing chicory compared to those grazing perennial ryegrass. Faster rates of lignin solubility in the rumen probably contributed to the more rapid breakdown of chicory in the rumen.

At the Centre for Tropical Veterinary Medicine, Scotland, during the summer months of 1987, two adult water buffaloes, two Brahman cattle and two Brahman × Friesian steers walked round a circular track on concrete or through 300 mm deep mud. Average walking speed (m/s) when unloaded, or average walking speed (m/s) when pulling 324 N, energy for walking (J/m/kg) and net mechanical efficiency (%) were 1·05 and 0·81 (P < 0·01), 1·03 and 0·80 (P < 0·001), 1·49 and 3·34 (P < 0·001) and 31·0 and 31·8 for concrete and mud respectively. Energy values were calculated from gaseous exchange measured with an open circuit system.

In Central Nigeria, from September 1991 to May 1992, the energy expenditure of eight Bunaji (White Fulani) bulls was monitored using portable oxygen measuring equipment (modified ‘Oxylog’) when walking, ploughing and harrowing on six soil surfaces ranging from hard, smooth earth to ploughed, waterlogged clay. Average walking speeds (m/s), pulling speeds (m/s) and energy cost of walking (J/m/kg) varied from 0·97 to 0·65, 0·55 to 0·47 and 1·47 to 8·58 respectively. Net mechanical efficiency averaged 31·4% and was unaffected by ground surface.

The energy cost of walking for the Bos indicus cattle on smooth ground (1·47 J/m/kg) in this trial was less than that previously reported for Bos taurus (1·80 J/m/kg) and the reported average value for cattle (Bos indicus and Bos taurus) on treadmills (2·09 J/m/kg). The implications for practical agriculture of the higher levels of energy expenditure for walking in muddy conditions are discussed.

Changes in amino acid and glucose metabolism in response to increments of rumen escape protein (REP) were studied in groups of lambs of three differing dietary histories and consequent weights, but similar ages. Crossbred wether lambs (Merino × (Border Leicester × Merino)) were fed to obtain three distinct growth patterns. The LW group (n = 15) were offered a low quality roughage diet throughout the experiment. The MW group (n = 19) were offered a high quality mixed diet followed by the same low quality diet as LW lambs. The HW group (n = 8) were offered a high quality mixed diet throughout. All diets were offered once daily ad libitum. The LW, MW and HW groups had liveweights of 18, 32 and 41 kg respectively at the commencement of supplementation, and were 33±0·1 weeks of age. REP supplements (formaldehyde-treated casein) were offered at 0, 20, 40, 60 or 80 g/day to MW and LW lambs and at 0 or 40 g/day to HW lambs.

REP increased basal digestible organic matter intake (DOMI), liveweight gain (LWG) and urinary N excretion and tended to increase N balance in LW and MW lambs. DOMI, N intake, N balance and LWG were all higher (P < 0·05) in HW compared to MW and LW lambs. REP tended (P < 0·10) to increase LWG in each dietary history group.

Blood glucose concentration was higher (P < 0·01) in HW than in other lambs but was not significantly altered by REP supplementation. Irreversible loss of glucose was greater (P < 0·01) in HW lambs and increased (P < 0·001) with REP for LW and MW lambs. REP increased (P < 0·05) phenylalanine (Phe) concentration in blood, Phe flux and oxidation and whole body rates of protein synthesis and degradation. HW lambs had higher (P < 0·05) values for all these parameters than did MW and LW lambs.

REP increased (P < 0·05) plasma concentrations of insulin-like growth factor-1, and plasma insulin increased (P < 0·05) in MW but not in LW or HW lambs. REP had no effect on plasma growth hormone (GH) concentration. Plasma concentration of insulin was higher (P < 0·05) in HW than in MW or LW lambs, while GH was not significantly affected by dietary history.

The results show that supplementation of ruminant diets with REP increases the rate of flux and oxidation of amino acids, and the rate of glucose utilization. Amino acid supply appears to influence glucose utilization more through oxidation rate than supply, and this relationship is affected by previous dietary history (weight for age) and energy availability, either from the diet or from body stores.

Ten single-sire mating groups of 13 Horro ewes per ram were used to study the effects of mating on liveweight, body condition and scrotal circumference changes and their relationships with level of sexual activity at different stages of the joining period, and effects of sexual activity and pre-joining liveweight and scrotal circumference on fertility. Mating had adverse effects on liveweight, body condition and scrotal circumference. There was a tendency for mean daily liveweight loss to increase with increasing number of services during the period of peak sexual activity and over the whole joining period. Changes in scrotal circumference were non-significantly correlated with sexual activity. Pre-joining liveweight and scrotal circumference had no significant effects on the proportion of ewes served, rate of return to first service and fertility. High losses of liveweight and scrotal circumference were observed during the stage of peak sexual activity, and it could be suggested that more supplementary feed should be provided to working rams at this stage, especially if the ewe[ratio ]ram ratio is to be increased. There is no significant benefit to be gained by increasing ram mating weight and scrotal circumference from 30 kg and 27 cm to 40 kg and 31 cm respectively in Horro sheep.