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Climatic and soil conditions in Uruguay are marginal for white clover (Trifolium repens L.). Plants were collected from four sites, in different parts of the country, multiplied vegetatively, and the populations planted into each of the four sites. Plant survival and internode length (indicating growth potential) were recorded at intervals during the 55-week period after planting. On the site with the highest annual rainfall and lowest summer water deficit, one fifth of the plants survived at least 55 weeks, whereas on the site with the highest annual evaporation almost all the plants had died within 20 weeks. There was some evidence of adaptation to a ‘home’ site in both plant survival and growth potential. Thus, on three of the four sites, populations from the ‘home’ site survived better than the average of the non-‘home’ populations. Also, internode length was greatest (9·5 mm on average, compared with a mean of 5·6 mm for the experiment as a whole) in a population from a site with soil relatively high in available P, when planted into its ‘home’ site. Plant breeders could consider producing different white clover cultivars to suit different conditions of moisture supply and available P.

The present study was conducted to investigate whether white clover (Trifolium repens L.) in grazed swards in Uruguay can produce and shed sufficient seed, and whether sufficient seedlings can develop and survive, to make an important contribution to the long-term persistence of the species. Five sites, on which survival of white clover had been better than is usual in Uruguay, were studied in 1995–97. The sites had been sown with white clover 11–15 years previously and were managed mainly by cattle grazing. The number of white clover inflorescences/m2 was at least 18 at nearly half the counts in the study and the number of viable seeds in the top 5 cm of soil was at least 1500 at half the counts. The results for both the above variables suggest that all five sites had a supply of seed greater than a commercial seed rate at some times of the year. However, the number of seedlings/m2 was >100, a possible target in these conditions, at only one fifth of the counts, and the proportion of seedlings that survived from one recording date to the next (a period of 4–5 weeks) varied from >0·7 to zero. It seems, therefore, that, in these conditions, the failure of seeds to convert to established plants is likely to be a greater constraint than the production and shedding of seeds. There was considerable variability with time, and between and within sites at each stage of the reproductive cycle. On one site, competition from Bermudagrass (Cynodon dactylon) greatly reduced the number of white clover seedlings/m2. Overall, the results suggest that white clover in grazed swards in Uruguay can produce and shed sufficient seed, and that sufficient seedlings can develop and survive, to make a significant contribution to the long-term persistence of the species. However, each year there is a risk of seedlings being killed in dry, hot weather.

In order to learn more about the digestibility, breakdown when eaten and physical structure of stovers and straws, seven diets were compared in one experiment and eight in another. The diets in the first experiment were: the upper and lower parts of lucerne (Medicago sativa) hay, the leaves, upper stem and lower stem of maize (Zea mays) stover and the leaves and stem of sorghum (Sorghum vulgare) stover. The diets in the second experiment were: the upper and lower parts of lucerne hay, the leaves, stems and whole stover of millet (Setaria italica), wheat (Triticum aestivum) straw, rice (Oryza sativa) straw and sweet potato (Ipomoea batatas) haulm. The diets were examined for in vitro digestibility in three forms: milled, chopped (1 cm lengths) and chewed (by cattle). The lengths and widths of the chewed particles were recorded in both experiments. Aspects of the morphology and vascular structure of plant parts of the diets and of chewed particles were recorded in the second experiment.The in vitro digestibility of chopped or chewed plant material was lower (by 11 and 12 percentage units, respectively, on average) than that of milled material. The difference between chewed and milled material in in vitro digestibility was smaller with leaves (5 percentage units, on average) than with stems (18 percentage units, on average) in maize, sorghum and millet. Digestibility of chewed material was similar to or lower than that of chopped material, except with the leaves of maize, sorghum and millet. Millet stover had higher in vitro digestibility than wheat straw or rice straw, whether the diet was milled, chopped or chewed.The thinnest stem internode vascular bundles recorded (0·14 mm) were in wheat. The percentage of stem internode cross-sectional area occupied by vascular bundles was in the range 6–8 for lucerne, millet, wheat and rice. The mean numbers of veins or vascular bundles per chewed particle were in the range 6–23. The mean length of the chewed particles varied from 10 mm with the upper stem of maize to 18 mm with sorghum stem and maize leaves. The mean width of the chewed particles varied from 1·8 mm with rice straw to 5·4 mm with maize leaves.It is suggested that the low digestibility of mature plant tissue such as stovers and straws is not particularly due to thick vascular strands or to a high proportion of vascular tissue, but rather to a high proportion of cell wall and incomplete and delayed access by rumen microorganisms to much of the cell wall.

Swards on wet hill land in mid-Wales, which had been converted from semi-natural rough grazing (dominated by Molinia caerulea, Nardus stricta or Calluna vulgaris) by surface-sowing in the period 1965–75, were examined in 1982, 1984 and 1996/97, using a point quadrat technique, in order to record the extent to which the sown species had persisted and the ingress of unsown species.Lolium perenne had persisted to 1996/97 to the extent of being 20% of the sward on sites c. 300 m above sea level and 3% on sites at c. 500 m. Trifolium repens had persisted to c. 7% of the sward at both elevations. Festuca rubra was 6% of the sward on the higher sites and close to zero on the lower ones. The other main sown species, Phleum pratense, was present in only trace amounts on all sites in 1982, 1984 and 1996/97. The failure of T. repens to persist in larger amounts was attributed in part to below optimum soil pH and K and to the annual application of fertilizer N. The decline in L. perenne was attributed in part to severe winters on the higher sites and to below optimum soil K and pH. Agrostis spp. were the most prominent of the unsown species. Poa spp. appeared to stabilize at 8–15% of the sward. Stellaria media and Holcus lanatus became fairly prominent on the lower sites and Anthoxanthum odoratum on the higher sites. A supplementary study of the lower sites showed that the lime had been effective to at least the 20–25 cm layer of soil, that the distribution of plant roots in the soil was not abnormal, that T. repens plants had a satisfactory number of root nodules and that the soil contained a satisfactory number of earthworms.

The paper reports a study of the chemical composition of 25400 grass silages produced in England and Wales, of which 1040 were from the period 1961–63, 17900 (15480 clamped and 2420 baled) were from 1982–88 and 6460 (5640 clamped and 820 baled) were from 1992–93. A sample of each silage had been analysed for dry matter (DM), pH, crude protein (CP) and volatile N and in most cases for ash.The baled silages were drier on average than the clamped silages, with a wider spread of DM contents. The clamped silages with the lowest pH on average were those with a DM content of c. 240 g/kg; clamped silages wetter than this were progressively higher in pH with reduction in DM content; clamped and baled silages drier than 240 g/kg were progressively higher in pH with increase in DM content, up to pH 5·9 in baled silages of 580 g DM/kg. At a given DM content pH was on average 0·6 units higher in baled than in clamped silages. The ash content of baled silages was similar to that of clamped silages. There was an increase in the mean CP content of clamped silages between 1961–63 and 1992–93 and a reduction in the proportion of CP which was volatile. The relationship between DM and volatile N as a proportion of total N was a curve rather than a straight line, with the steepest part of the curve at the lower end of the DM range. The wet silages harvested in 1961–63 were particularly high in volatile N. At a given DM content in the range 170–320 g/kg, volatile N was rather higher in baled than in clamped silages in both 1982–88 and 1992–93. Clamped silages with a DM content of at least 250 g/kg and baled silages with a DM content of at least 310 g/kg were typically well preserved in the sense of having

To appreciate more clearly some of the physical characteristics of forages which may be important in relation to digestibility and structural integrity, different parts of eight plant species were examined for the proportion of thick-walled, thin-walled and epidermal cells, the thickness of the cell walls and the diameter, length and volume of the cells. The eight species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. Early harvesting was compared with later harvesting in each of two years. The plants were grown in a heated glasshouse in spring–summer.The plant parts with the lowest proportion of thick-walled cells (3–6% of cross-sectional area) were the legume leaflets and those with the highest proportion (47–57%) were the leaf blades and stems of C. ciliaris. The plant parts with the highest proportion of thin-walled cells were the legume leaflets and petioles and the Z. mays stems and leaf sheaths. The walls of the cells categorized as thick-walled were thinnest (0·9 μm) in L. perenne leaf blades and T. repens leaflets and thickest (2·0–2·3 μm) in the leaf blade midribs, leaf sheaths and stems of Z. mays and in the stems and petioles of T. repens. The thinnest outer walls of epidermal cells (0·9 μm) were recorded for the leaf blades of L. perenne.The largest cells within the categories and plant parts examined (1 100000 μm3) were thin-walled cells in the stems of Z. mays. The longest cells recorded (180 μm) were thin-walled cells in the petioles of T. repens. The thick-walled cells were particularly small (1800–2600 μm3) in L. perenne leaf blades and sheaths and in T. repens leaflets. The largest thick-walled cells in the study were in the stems and petioles of T. repens. The epidermal cells of D. intortum leaflets, petioles and stems were particularly small (2000–3000 μm3).

In order to understand better some of the reasons for differences between forage plant species in digestibility, different parts of nine plant species in either milled or chopped (1 cm lengths) form were examined for in vitro digestibility and in milled form for neutral detergent fibre and lignin. The nine species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Brassica napus L., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. In each case early harvesting was compared with later harvesting in each of two years. The plants were grown in spring–summer in a heated glasshouse.The forage at the early harvest was, on average, 1–4% units more digestible in vitro than that at the later harvest and generally slightly lower in lignin and neutral detergent fibre content. However, the stems of Z. mays were higher in neutral detergent fibre at the early than at the later harvest.The leaf sheaths of L. perenne and F. arundinacea were more digestible than the leaf blades. L. perenne was more digestible than F. arundinacea in both sheaths and blades. The sheaths and blades of C. gayana and C. ciliaris were less digestible and had a higher neutral detergent fibre content than those of L. perenne and F. arundinacea. The leaf blades, excluding the midribs, and the stems and leaf sheaths of Z. mays were all rather high in digestibility when milled and moderately low in neutral detergent fibre and lignin; the leaf blade midribs of Z. mays were less digestible and higher in neutral detergent fibre than the stems and similar to the stems in lignin content. The leaflets of T. repens had an appreciably lower neutral detergent fibre content than the stolons and petioles and a rather lower lignin content in dry matter and yet were, if anything, less digestible than the stolons and petioles. The stolons of T. repens were much more digestible than the stems of M. sativa and D. intortum. The digestibility of D. intortum was low in all the plant parts examined, leaflets, petioles and stems. In both D. intortum and B. napus, the leaflets or leaf blades were much lower than the stems in neutral detergent fibre and lignin and yet they were no more digestible than the stems when milled.The digestibility of chopped leaflets and leaf blades was similar to that of milled leaflets and leaf blades, but chopping rather than milling reduced the digestibility of stems (particularly of those of Z. mays), petioles, the leaf blade midribs of Z. mays, and, to some extent, leaf sheaths.

In order to understand more about the nature of forage particles before they enter the rumen and about the degradation of cell walls in the rumen, particles of different plant parts produced by sheep when eating each of eight plant species were described in terms of volume and exposed surface area and in terms of numbers of cells and volume and surface area of cell wall. Estimates were made of the extent to which the walls would be degraded in the rumen. The eight species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. In each case early harvesting was compared with later harvesting in each of two years. The plants were grown in a heated glasshouse.The plant parts which were chewed to the smallest particle size during eating, and which produced particles with the largest proportion of total cell wall area exposed on the outside of the particle (6–10%), were the legume leaflets and the grass leaf blades and sheaths. The proportion of total cell wall area exposed on the outside of chewed particles derived from stems was only 3–4%. The number of thick-walled cells per mm3 of chewed particle was greatest in particles derived from the leaf blades and stems of C. ciliaris, the leaf blades and leaf sheaths of L. perenne and the stems of C. gayana. The average number of thick-walled cells per particle was 860000 in particles derived from the stems of C. gayana and C. ciliaris and 260000 in particles derived from L. perenne leaf blades and sheaths. The volume and surface area of walls of thin-walled cells per mm3 were greatest in particles derived from legume leaflets. The total surface area of walls of epidermal cells per mm3 was greatest in particles derived from leaflets and leaf blades and least in those derived from stems. The estimated percentage of wall thickness of thick-walled cells which would be degraded in the rumen was relatively high in the case of leaf blades, sheaths and stems of C. ciliaris, leaf blades of Z. mays, leaf sheaths of L. perenne and F. arundinacea and stems of C. gayana, relatively low in the case of petioles of T. repens and stems of D. intortum and M. sativa and close to zero in legume leaflets. The estimated percentage of wall thickness which would be degraded did not seem to be related to the concentration of lignin in the walls, either in grasses or in legumes.

Six plant species were compared in terms of their physical breakdown when eaten by sheep and when macerated: chickweed (Stellaria media (L.) Vill.), dandelion (Taraxacum officinale Weber), dock (Rumex obtusifolius L.), ribwort (Plantago lanceolata L.), spurrey (Spergula arvensis L.) and perennial ryegrass (Lolium perenne L.). In two experiments at Aberystwyth in 1985 and 1986, the species were artificially dried and fed to lambs as the total diet. In another experiment in 1987, they were fed fresh, in 1·5 min meals, to yearling sheep.Perennial ryegrass was more difficult to break down than the dicotyledonous species, judging by the particle size distribution in macerated and in chewed material and in the rumen contents and from the rather long time the sheep spent eating and ruminating per 100 g dry matter (DM) intake and the rather high fibrosity index. The width of some of the smaller ryegrass particles in the rumen was such that they must have contained only a single vein. Spurrey was readily broken down by macerating and by chewing and a relatively short time was spent eating and ruminating per 100 g DM intake. The shape of spurrey particles in the rumen was quite similar to that of stemmy ryegrass particles and the fibrosity index of spurrey was high. The breakdown of chickweed was similar to that of spurrey, but the fibrosity index of chickweed was lower. Accumulation of DM in the caecum appeared particularly pronounced in sheep fed ribwort or dock. The dock particles in the rumen typically had a low ratio of length to width and it seemed that dock particles did not need to be reduced in size as much as ryegrass particles before passing out of the rumen.

SUMMARYTrue dry matter digestibility, proportion of cell content, digestibility of cell wall, N and water-soluble carbohydrate were determined in eight related grasses in February, June and September in each of three years. In a separate experiment, true dry matter digestibility, proportion of cell content and digestibility of cell wall were determined in five plant parts of vegetative tillers of two grasses in February, April, June, August, October and December in each of two years.Perennial ryegrass (Lolium perenne) was the most digestible grass and tall fescue (Festuca arundinacea) and Westerwolds ryegrass (Lolium multiflorumvar.Westerwoldicum) were the least digestible. Italian ryegrass (Lolium multiflorum) was high in proportion of cell content, but not in digestibility of cell wall. Meadow fescue (Festuca pratensis) was high in digestibility of cell wall, but low in proportion of cell content. Perennial ryegrass and hybrid ryegrass were high, and tall fescue low, in both proportion of cell content and digestibility of cell wall. Ryegrasses were lower than fescues in concentration of N and higher than the fescues in water-soluble carbohydrate; ryegrass × meadow fescue hybrids were intermediate between the parent species in N and watersoluble carbohydrate.Grass sampled in June and August was lower in both proportion of cell content and digestibility of cell wall than grass sampled at cooler times of year. Grass sampled in February was high in proportion of cell content and N, intermediate to high in digestibility of cell wall and intermediate in water-soluble carbohydrate.Expanding leaf blades of perennial and Italian ryegrass were higher than expanded blades and sheaths in digestibility of cell wall and similar to expanded blades and higher than sheaths in proportion of cell content. Cell wall was less digestible in the tip than in the middle and basal portions of expanded leaf blades.

SUMMARYThe effectiveness of chewing by sheep during eating in breaking a forage diet into particles was studied in twelve plant species over 2 years and related to the physical structure of the plants and their rate of intake. The twelve species were: Trifolium repens L., Medicago sativa L., Onobrychis viciifolia Scop., Desmodium intortum (Mill.) Urb., Brassica napus L., Spergula arvensis L., Lolium perenne L., Lolium multiflorum Lam., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. In each case early harvesting was compared with later harvesting. The plants were grown in a heated glasshouse.L. perenne and L. multiflorum were broken into a large number of particles per g dry matter; the particles were rather long and thin. F. arundinacea was broken into heavier, slightly shorter and slightly wider particles. C. gayana and C. ciliaris were broken into particles which were smaller, heavier and contained more vascular bundles than those of Lolium, reflecting the lower rate of intake, greater weight per unit area of leaf blade and greater proximity of bundles of the tropical grasses. Z. mays leaf blades broke into shorter, wider particles than the leaf blades of the other grasses, reflecting the much wider blades of Z. mays.The leaflets of the four leguminous species and the leaf blades of B. napus were broken into particles with an average length:width ratio of c. 2:1, compared with an average ratio of c. 7:1 for particles derived from grass leaf blades other than those of Z. mays. The legume leaf petioles were broken into particles with an average length: width ratio of c. 13:1; many of the legume petioles were not split longitudinally during chewing. The stems of M. saliva and D. intortum were broken into particles similar in length and width to those from the stems of the tropical grasses, although the rate of intake of the legume diets was at least twice that of the tropical grass diets. The average length: width ratio of particles from B. napus petioles and stems was 5:1. A high proportion of particles from the B. napus and D. intortum diets had a rough surface. 5. arvensis was broken into more particles per g dry matter than the legumes and B. napus, despite its very high rate of intake. Many pieces of stem of S. arvensis were not split longitudinally during chewing.

SUMMARYFour plant species were compared in each of three harvest periods (in August/September) in 1991 and 1992 at Aberystwyth: white clover (Trifolium repens L.), rape (Brassica napus L.), spurrey (Spergula arvensis L.) and perennial ryegrass (Lolium perenne L.). Plant physical structure was considered in relation to rate of intake by sheep, chewing activity and the effectiveness of chewing in breaking the diet into particles.White clover had a much lower proportion of cell wall than perennial ryegrass, but the rate of intake and the number of chews per min were similar for the two species. White clover petioles broke down into long, thin particles, similar in size and shape to those derived from perennial ryegrass leaf sheaths; many of the clover petioles were not split longitudinally by chewing, in contrast to the ryegrass sheaths. A white clover leaflet was typically broken into about 20 blocky particles, whereas a petiole of similar weight was broken into only about three particles. Veins were close together in ryegrass leaf sheaths and blades, particularly the latter; approximately one in seven strips of weaker tissue between veins was ruptured by chewing leaf sheaths and one in 16 in the case of leaf blades, in each case resulting in particles of c. 2 mm width. Rape had a low proportion of cell wall and a low proportion of vascular tissue in its leaf blades, petioles and stems. Rape leaf blades were eaten quickly, but the stems were eaten slowly. The length and width of particles derived from rape leaf blades were very similar to those of particles derived from white clover leaflets. Spurrey had a high proportion of cell wall and was low in in vitro digestibility, but the rates of intake and chewing were high and relatively few chews were required per g of dry matter ingested. The vascular bundles in the spurrey stems were only half the thickness of the bundles in white clover petioles; pieces of spurrey stem were typically broken at about two places along their length and were not split during eating.The study illustrates the wide variation in plant anatomy among species which can be available to herbivores and some effects of the abundance, thickness and orientation of vascular bundles on rate of intake, chewing activity and the size and shape of particles produced by chewing.

SUMMARYThe idea that the addition of compound feed to grass at ensilage can result in adequate preservation of the crop without the need for an acid additive, and that less compound feed would then need to be given when the silage is subsequently fed, was tested with dairy cows. Two diets were compared: (1) a conventional grass silage, to which acid had been added at the time of ensiling, plus concentrates supplied at the time of feeding, and (2) grass silage, to which a compound feed had been added at the time of ensiling, plus a lower rate of concentrates. Each diet was fed to 12 lactating cows for 82 days.The total intake of dry matter was 17·3 kg per cow per day on diet 1 and 18·3 kg on diet 2. Daily milk yields per cow were 24·5 and 26·1 kg, respectively, with similar milk composition. The estimated diet costs per kg of milk were 9·3 p on (1) and 8·3 p on (2). It is concluded that the addition of compound feed to grass at ensilage is worth considering on dairy farms as an alternative to conventional grass silage, but that a more comprehensive study is needed.

SummaryLeaf development was studied in eight related grasses, grown in field swards cut at 5-week intervals, during the year of sowing and the subsequent year (1989 and 1990). The rate of leaf expansion was in the order Westerwolds ryegrass > Italian ryegrass (Lolium multiflorum), Italian ryegrass × meadow fescue > hybrid ryegrass > perennial ryegrass × meadow fescue, meadow fescue (Festuca pratensis), tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne). The order of grasses was similar, but not identical, for rate of leaf appearance, rate of leaf extension, weight of leaf blade emerging per shoot per week and rate of increase in length of exposed leaf sheath, and the order was approximately the reverse for weight per unit area of emerging leaf blade. The area per leaf blade increased greatly between May and October of the year of sowing, particularly in Westerwolds, Italian and hybrid ryegrasses and Italian ryegrass × meadow fescue. Area per leaf blade in tall fescue increased greatly between May and July of the year of sowing and May–July of the subsequent year. Rate of leaf expansion in meadow fescue was much higher in May of the year after sowing than in the previous May.

SUMMARYThe concentrations of water-soluble carbohydrate, N, nitrate-N, P, K, Ca, Mg and Na were determined in six plant species: chickweed (Stellaria media (L.) Vill.), dandelion (Taraxacum officinale Weber), dock (Rumex obtusifolius L.), ribwort (Plantago lanceolata L.), spurrey (Spergula arvensis L.) and perennial ryegrass (Lolium perenne L.). Field crops of these species were grown at Aberystwyth in 1985,1986 and 1987. In 1985 and 1986 the rumen contents and faeces of lambs fed artificially dried diets of the different species were analysed for N, P, K, Ca, Mg and Na. The intake, apparent availability and, in 1986, retention of each element by the lambs on each diet were calculated.The results illustrate the potential of dicotyledonous species to extend the range of concentration of some major elements beyond that normally found in temperate grasses. Chickweed was particularly high in P and K, dandelion in K and Mg, dock in Mg, ribwort in Ca and spurrey in Mg and Na. The apparent availability of the elements studied was as high in chickweed, dandelion and spurrey as in ryegrass. The apparent availability of N and P was lower in dock and ribwort than in ryegrass, possibly due to heat damage during drying. All five dicotyledonous species had a higher Mg concentration in herbage than ryegrass (c. 70% higher, on average) and all led to a higher Mg concentration in rumen contents than ryegrass (c. 70% higher, on average). Retention of Mg was three times as great, on average, in sheep fed dicotyledonous diets as in sheep fed ryegrass. The concentration of water-soluble carbohydrate was lower in the dicotyledonous species than in ryegrass. The concentration of nitrate-N was rather high in ribwort when harvested at a leafy stage in October. Dock was moderately low in nitrate-N, despite a rather high concentration of total N.

SUMMARYAll combinations of five cutting heights (2, 4, 6, 8 and 10 cm), two rates of P application (0 and 100 kg P/ha per year) and two irrigation treatments (0 and maximum soil water deficit 35 mm) were compared on field plots sown with a mixture of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) in Wales. The cutting and P treatments were applied for 4½ years (1986–90) and the irrigation treatments for 2 years (1987 and 1988). The plots were cut at 4-week intervals from April to October each year.Applied P and irrigation had only a small effect on the productivity and composition of the swards. The proportion of white clover in the sward was inversely related to the height of cutting, so that clover was almost eliminated by 3 years of 10 cm cutting. This reduction in clover content led to a 50% reduction in herbage yield. Close cutting increased the tiller density of ryegrass in May and June of the first harvest year, but this effect was subsequently reversed as clover competed more strongly with ryegrass under close cutting. The proportion of unsown species, predominantly Agrostis tenuis, was much higher in the third and fourth than in the first and second harvest years and was positively related to the height of cutting. Close cutting depleted soil K and soil water.

SUMMARYYields of dry matter, nitrogen, phosphorus and potassium in herbage and cereals from fields representing different stages of the rotation were recorded on two organic farms in 2 years. Amounts of N, P and K purchased and sold were also recorded on these farms.Some additional data was obtained from three other organic farms. Herbage production was very satisfactory, whether fields were grazed or cut. The proportion of clover in sown swards was, in most cases, satisfactory to high, but the clover content was very low in a few fields. The yields of cereals were about equal to or below the average obtained on farms using fertilizer and other agrochemical inputs. Manure was normally applied to the leys, which were the fertility-building part of the rotation, rather than to the cereal crops. Leaching of K from manure heaps was considerable.Purchases of N, P and K (mainly in manure) seemed excessive on one of the farms. On one of the farms studied in less detail, less P and K were purchased than were sold. More attention could be given to the balance between purchases and sales of N, P and K and to the efficient conversion of N into saleable produce.

SUMMARYOn two organic farms, nitrate-N and ammonium-N in the surface layers of the soil of representative fields were recorded for 2 years. Nitrate-N was also determined in different soil layers down to 120 cm at the beginning, middle and end of two winters and at intervals after ploughing three fields, to seek evidence of leaching.Nitrate-N and ammonium-N were both consistently low in the surface layers of fields in ley. Nitrate-N accumulated in arable soils on some occasions when there was little or no crop uptake of N, after ploughing, and after very heavy applications of manure.There was some evidence of nitrate leaching in all five fields which were deep-sampled. In four cases, the loss by leaching appeared to be < 25 kg N/ha per winter. In the other case, in which a 4-year ley was ploughed on 5 October, the loss by leaching appeared to be c. 70 kg N/ha. Ploughing in winter, rather than early autumn, might have reduced the nitrate leached, but the drilling of the next crop might have been delayed.The nitrate concentration of water draining from recently ploughed sandy soil in Shropshire was high, but it would have been diluted by water draining from unploughed fields.

SUMMARYSix plant species were compared as food for sheep: chickweed (Stellaria media (L.) Vill.), dandelion (Taraxacum officinale Weber), dock (Rumex obtusifolius L.), ribwort (Plantago lanceolata L.), spurrey (Spergula arvensis L.) and perennial ryegrass (Lolium perenne L.). In two experiments at Aberystwyth in 1985 and 1986, the species were fed to lambs as the total diet, after artificial drying. In another experiment in 1987, they were fed fresh, in 1·5 minute meals, to yearling sheep.The dicotyledonous species had a lower proportion of cell wall (neutral detergent fibre) in dry matter than perennial ryegrass. The true dry matter digestibility of chickweed, dandelion, dock and leafy ribwort was as high as that of ryegrass, but the in vivo digestibility of all five dicotyledonous species was lower than that of ryegrass. The voluntary intake of the dicotyledonous species was higher than might have been predicted from their digestibility. The voluntary intake of spurrey was > 20% higher than that of ryegrass.When the species were fed fresh, spurrey had the highest rate of intake as a consequence of a high chewing rate and a low requirement for number of chews/g of dry matter consumed. Chewing rate was higher on all the dicotyledonous diets than on ryegrass. The rate of intake of dandelion was above average, but that of dock was low and variable, particularly when the plants had been chopped.

SUMMARYTwo varieties of Italian ryegrass (Lolium multiflorum Lam.), Tribune and RvP, were cut in each of 2 years, ensiled and individually fed, ad libitum, to dairy cows. In one year, two rates of supplementary concentrate feeding were compared and, in the other year, two types of concentrate and a silage-only diet. Tribune silage was more digestible, in vitro, and was lower in neutral detergent fibre and fibrosity index than RvP silage. There was no difference between the varieties, however, in the cows’ intake of silage. On the silage-only diet, the cows fed Tribune produced a higher yield of milk solids than did those fed RvP; on the other diets, there was no significant difference between varieties in the yield or composition of milk.The same two varieties were compared when grazed by herds of dairy cows in spring, summer and autumn of the first harvest year on six farms and in the second harvest year on four of the farms. Tribune persisted much better than RvP, in numbers of plants and tillers/m2 and in ground cover, and the herbage was more digestible than that of RvP. Milk yield/cow was c. 0·6 kg per day higher when grazing Tribune than when grazing RvP.

SUMMARYThe growth and seed production potential of white clover (Trifolium repens L.) was studied in field plots in 2 years, with and without a companion grass (Lolium perenne L.). Three rates of grass suppressant, fluazifop-butyl (Fusilade), applied in early June, were compared on plots sown with the companion grass. Two clover varieties, Aberystwyth SI84 and Olwen, were compared.Sowing a companion grass reduced the amount of clover in the sward in both the first and second harvest years, but did not affect the vigour of individual clover growing points or the number of clover inflorescences when the crop was ready to be harvested for seed.Fluazifop-butyl, at the highest rate used (125g/ha), reduced the rates of leaf emergence and extension, and the numbers of reproductive tillers, in Lolium, without reducing the rate of leaf emergence in clover, although the weight per clover leaf was somewhat reduced. In the first harvest year, the numbers of SI84 inflorescences in June and July were increased by fluazifop-butyl, but the effect had worn off by harvest (24 August). Seed yield potential was not increased by fluazifop-butyl at the rates used.Olwen produced heavier leaves, but fewer leaves and fewer growing points/0·1 m2 than SI84. In the first harvest year, Olwen had fewer and smaller inflorescences than S184.It proved feasible to measure the weight of new leaf produced per week and the nett additions to stolon and inflorescence dry matter (DM). The estimate of nett addition to stolon DM was increased by increasing the number of visible internodes included in the calculation, up to the maximum number recorded (nine). The rate of leaf emergence was slower on young branches than on main axes.

SummaryEffects 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 clover (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.White clover grew very strongly at Trefloyne in the first 2 years, fixing 350 kg N/ha/year where no N was applied; the clover declined very markedly during the 3rd year and there was very little in the sward in the 4th year; quite large quantities of clover were harvested in the 1st year even where 600 kg N/ha were applied. At Pwllpeiran the yields of clover were never high, but the clover persisted well where no N was applied. At Trefloyne the indirect contribution of the clover (in increasing the yield of grass) was greater in the first than in the second half of the year; clover was later than grass to grow strongly in the spring, but the extra grass growth compensated for this, so that the seasonal distribution of total herbage yield was similar on a grass-clover sward receiving no fertilizer N to that on a grass sward receiving six applications of N per year. At Pwllpeiran, on the other hand, the indirect contribution of the clover tended to be greater in the second than in the first half of the year where no N was applied.The olover was similar to grass in phosphorus and potassium content and higher than grass in calcium and nitrogen. The clover was higher in nitrate-N content than grass grown without clover, at low levels of applied N, and increased the nitrate-N content of the grass growing with it.Water consumption at Trefloyne was greatest on swards which contained olover and on the swards without clover which received at least 400 kg N/ha/year. The effect of clover on soil water was apparent particularly in the lower horizons of the soil.

SUMMARYThirteen defoliation treatments were applied to a grass-white clover sward for 2 years to study some effects on the sward of cattle grazing compared with sheep grazing compared with various cutting treatments and to study the effect of height of defoliation.Sheep actively sought out the clover in preference to grass whereas the cattle did not. The response of the clover to sheep grazing was a large reduction in the amount of stolon, shorter internodes, petioles and leaflets, and thinner stolon closer to the ground. Reducing the height of defoliation from 8 to 4 cm above ground level also reduced the dimensions of white clover. The clover, however, appeared to recover quickly and completely from the effects both of sheep grazing and of reducing the height of defoliation when these treatments were discontinued. In plots cut for hay the clover disappeared from the sward suddenly and completely in dry conditions following the 2nd-year hay cut. The effect of cattle grazing on white clover was similar to the effect of comparable cutting treatments. Cattle grazing, however, reduced the number of tillers of grass andincreased the proportion of bare ground, compared with cutting or sheep grazing. Grazing rather than cutting tended to encourage perennial ryegrass and to discourageHolcus. Cutting for hay encouragedBromus mollis. Reducing the height of defoliation reduced leaf sheath and blade length and the rate of production of new blade per tiller in perennial ryegrass, but increased the numbers of tillers of grasses.

SummaryThe effect of six intervals between harvests and three levels of N application on digestibility, digestible yield and nitrogen content and yield was studied in four ryegrass(Lolium) varieties during a 30-week period in the first harvest year in a field experiment.Digestibility was higher with a 3-week than with a longer interval between harvests. Yield of digestible organic matter was increased by extending the interval from 3 to 6 weeks, but was slightly reduced by extending from 6 to 10 weeks.Increase in the level of applied N increased the degree of curvature downwards in the response to extending the interval in both yield of digestible organic matter and yield of N, supporting the view that N use should be accompanied by shortened intervals between harvests.Digestibility varied by up to 15 units D-value from one time of the year to another with a constant interval between harvests. The highest values were in the spring. Autumn values were low in spite of a relatively high proportion of green leaf.During the period immediately following the main period of stem development, doubling the interval from 4 to 8 or from 5 to 10 weeks reduced digestibility by 10 units and reduced digestible yield by 22%.In the absence of applied N, the N yield of S. 321 was 31% greater than the average of S. 22, S. 23 and S. 24. However, the apparent recovery of applied N in S. 321 was much lower than in the other varieties.

SummaryThe effect of six intervals between harvests and three levels of N application on the concentration of nitrate-N and total N in total herbage, green leaf and ‘stem’ was studied in two varieties of perennial ryegrass during 30-week periods in each of the first two harvest years of a field experiment. The effect of two intervals between harvests on the concentration of nitrate-N in Italian ryegrass total herbage was studied in the same experiment. The effect of two intervals between harvests and three levels of N application on the concentrations of nitrate-N and total N in total herbage was studied in five grasses during a 32-week period in a second field experiment.Increasing the interval between harvests tended to increase the concentration of nitrate-N in herbage; however, this seemed due mainly to the average date of harvest being later in the year with the longer intervals. The concentration of nitrate-N in herbage increased from June to September. Italian and hybrid ryegrass and tall fescue were much higher than perennial ryegrass in nitrate-N concentration at the highest level of applied N (525 kgN/ha per year). Apart from the species and time of year effects, the nitrate-N concentration seemed to be determined mainly by the amount of N applied divided by the number of days between the date of application and the date of sampling. The ‘stem’ of perennial ryegrasa tended to be slightly higher in nitrate-N concentration than green leaf. The proportion of nitrate-N in total N was increased by increasing the interval between harvests and by applying N and was nearly twice as high in ‘stem’ as in green leaf. Both the nitrate-N and the total N concentration of herbage, particularly the latter, seemed to be inversely related to solar radiation receipt.

SummaryThe effects of six intervals between harvests and three levels of N application on the initiation, emergence and longevity of leaves and longevity of tillers of Italian ryegrass and on dimensions and weights of leaves of four ryegrass varieties were studied in the first harvest year in field experiments. Dimensions and weights of leaves and ‘stems’ of the four varieties were recorded on three dates in the second harvest year.The number of leaf primordia on the shoot apex of young Italian ryegrass tillers was increased by N application and seemed to be increased by increasing the period of uninterrupted growth allowed to the parent tillers. The number of leaves which emerged on marked tillers during a 30-week period was approximately halved by increasing the interval between harvests from 3 to 10 weeks, but was not affected by N application. The number of leaves which died on marked tillers was at least doubled by increasing the interval between harvests from 3 to 5 weeks. The second and third leaves to emerge on a tiller had a longer potential life than the first leaf. Increasing the interval between harvests greatly increased the average age of the green leaves in the canopy at the time of harvest.Length and width, but not thickness, of fully expanded green leaf blades were increased by both N application and increased interval between harvests. The effect of applied N in increasing leaf size appeared to be an important reason for the positive effect of N on yield, particularly with the longer intervals. The effect of N in increasing the number of tillers and leaves was important with the shorter intervals. Applied N reduced dry weight per unit volume of plant tissue and increased ‘stem’ length and increased weight and volume of herbage per unit volume of canopy. The area of exposed surface of ‘stem’ seemed too large to be ignored when considering the photosynthetic capacity of the canopy, particularly with the longer intervals.

SUMMARYHerbage from a grass-white clover sward was dried in the field to the hay stage (≤ 0·33 g moisture/g dry matter) at three times of year in 2 years comparing, in each case, all combinations of two stages of maturity, two levels of applied nitrogen and two thicknesses of swath. Samples taken at intervals during drying were analysed for nitrogen, phosphorus, potassium, calcium, magnesium and sodium.When there was little or no rain during drying, there was no change in the concentration of any of the six elements in the herbage dry matter between cutting and the hay stage, whatever the stage of maturity, level of N applied or swath thickness.The concentrations of potassium and sodium in the crop were greatly reduced by rain in the later stages of drying, but were less affected by rain in the early and middle stages; the concentrations of calcium and magnesium appeared to be reduced by rain as readily in the middle as in the later stages; the concentrations of nitrogen and phosphorus were relatively little affected by rain, but seemed likely to be more at risk in the later stages. The extent of the reductions in the concentration of elements was not markedly affected by the stage of maturity or level of N applied. There were reductions in the thin but not in the thick swaths when rain fell during the early and middle stages of drying, probably partly or wholly because the herbage in the thin swaths was drier, with a higher proportion of dead cells, at that time than the herbage in the thick swaths. At least 70 kg K/ha was leached out of the crop in the thick swaths by rain in the late stages of drying.

SummaryAll combinations of four harvesting treatments and two sowing dates were comparedin each of 3 years in field experiments near Nicosia. In two of the years, different levels of applied nitrogen were compared. The harvesting treatments were: (1) a milk-stage cut,(2) a boot-stage cut and a regrowth cut, (3) a grazing-stage cut and a regrowth cut, and(4) three grazing-stage cuts and a regrowth cut. The sowing dates were (1) normal (12 November) and (2) early (15 October), with sufficient irrigation to ensure establishment. There was almost no response to applied nitrogen, evidently because of high reserves of available nitrogen in the soil. Early sowing reduced by 20 days the time taken to reach the stage at which the first node appeared, but increased, by 36 days, the length of time between the first node and the milk stage. Early sowing increased yield when the firstcut was at the grazing stage, but reduced yield when the first cut was at the boot or milk stage. At the grazing stage, the proportion of green leaf blade and the concentrations of nitrogen and nitrate-N were relatively high (means 74, 4·0 and 0·13% respectively) and digestibility was moderate (mean D-value 61). By the boot stage, green leaf, nitrogen and nitrate-N, but not digestibility, had declined (means 21, 1·8, 0·02 and 63 respectively). By the milk stage, green leaf, nitrogen and digestibility, but not nitrate-N, had declined further (means 3, 1·5, 48 and 0·05 respectively). Fully dead leaf blades were 28 units less digestible and 3·2 percentage units lower in nitrogen concentration than emerging leaves. Half dead leaf blades were higher in nitrate-N than fully expanded, fully green blades. 'Stem’ declined greatly in nitrogen concentration, but relatively little in digestibility, between the grazing and the boot stage.Crops cut once or three times at a grazing stage recovered well, although theretended to be some reduction in the number of tillers compared with an undefoliated crop.

SUMMARYThe effect of six intervals between harvests and three levels of N application on the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence was studied in four ryegrass (Lolium) varieties during a 30-week period in the first harvest year in a field experiment. In one variety, S.23, the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.There was a bigger yield of ‘stem’ and a bigger total herbage yield response to doubling the interval between harvests in S.321 and S.22 than in S.23 and S.24.In the absence, but not generally in the presence, of applied N, S.321 outyielded the other varieties. S.24 was particularly responsive to applied N, especially in terms of green leaf yield.There was a large positive effect on yield of doubling the interval (from 3, 4 or 5 weeks to 6, 8 or 10 weeks respectively) during the main period of stem development. During the subsequent period, however, doubling the interval produced very little extra yield of total herbage and reduced green leaf yield substantially.The percentage increase in yield due to the application of N progressively decreased as the interval was increased.Maximum net production of green leaf was obtained by harvesting every 4 or 5 weeks for most of the season, extending to 6 weeks at the end. Harvesting every 3 weeks, by comparison, resulted in a slightly lower annual green leaf yield, but with a distinctly higher proportion of green leaf in the crop.Applied N generally had little effect on the proportion of crop fractions, but reduced the proportion of green leaf and increased that of' stem' in S.23 and S.24 at the August and September harvests.

SummaryThe effect of six intervals between harvests and two levels of N application on the proportion and digestibility of cell wall was studied in two perennial ryegrass (Lolium perenne) varieties in the first and second harvest years in a field experiment. In the oase of four of the six intervals between harvests the proportion and digestibility of cellulose, hemicellulose and lignin and the N content of cell wall were determined. Diets derived from three of the harvesting treatments were fed, at maintenance level, to sheep as a partial in vivo check on the in vitro procedures. The effect of six intervals between harvests and two levels of N application on the proportion of lignified tissue in leaf cross-section was determined in two varieties in the first harvest year.Effects of interval between harvests and time of year on herbage digestibility were due to effects on both proportion and digestibility of cell wall, particularly the latter. Hemicellulose digestibility appeared to be rather more affected by interval between harvests and rather more closely associated with the proportion of lignin than was cellulose digestibihty. The proportion of cell wall was particularly low and its digestibility particularly high in April and early May.The N in cell wall accounted for about 10% of total N in harvested herbage on all treatments. The ratio of cellulose to hemicellulose averaged 1:0·88 and hemicellulose was rather more digestible than cellulose. Cellulose and cell wall were less digestible in vitro than in vivo.The application of N tended to reduce the proportion of cell wall and to increase its digestibility in leafy but not in stemmy crops.Interval between harvests and N application had no effect on the proportion of lignified tissue in leaf cross-section.

SummaryThe effect of six intervals between harvests and three levels of N application on the dry-matter yield of total herbage, the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence of the sown species, the proportion and yield of unsown species, the digestibility and digestible yield and N content and yield was studied in S. 23 and S. 321 perennial ryegrass during a 30-week period in the second harvest year in a field experiment. In S. 23 the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.The results supported the main findings from the first harvest year (Wilmanet al.1976a, b).There was marked ingress of unsown species in the second harvest year with 3-, 4- and 5-week intervals in S. 321. The combination of 262–5 or 525 kg N/ha/year and 8- and particularly 10-week intervals over 2 years was too severe a treatment for the satisfactory survival of S. 23. With 525 kg N and 10-week intervals, S. 321 was equally badly affeoted.The application of 525 kg N/ha/year compared with nil reduced the proportion of green leaf in total herbage of the sown species by 11 percentage units, on average, and increased the proportion of ‘stem’ by 12 percentage units, in the second harvest year. The effect of N application on the proportion of crop fractions was found in both varieties and in all months of harvest. The effect was much greater than in the first harvest year. In S. 23 the application of 525 kg N compared with nil in the second harvest year increased the proportions of both true stem and leaf sheath (in total herbage of the sown species), true stem being the more important of the two, in this context, with the longer intervals and leaf sheath being the more important with the short intervals.Digestibility was not in general affected by N application despite the higher proportion of stem and leaf sheath and the lower proportion of green leaf blade resulting from N application. N did, however, tend to reduce digestibility at the harvests at which the proportion of stem was highest.Digestibility varied from one time of the year to another with a constant interval between harvests, but not as much as in the previous year. Lower digestibility of leafy crops in summer and autumn than in April and early May in both years may have been partly due to a higher proportion of dead material.Three periods were distinguished approximately in both years: May-June, July-August, and September-October. Only in the first of these periods was there a substantial increase in yield of digestible organic matter as a result of doubling the interval between harvests. Doubling the interval reduced digestibility in all three periods, but especially at harvests within the second period. Yield response to N was large in the first period, intermediate in the second, and low in the third. Apparent recovery of N was low and N content of herbage unduly high in the third period. N content of herbage was low with the long intervals between harvests at harvests in the first two periods. Applied N increased N content at these harvests and at all other times.

SUMMARYA site containing plots of sainfoin, red clover, lucerne and hybrid ryegrass, each sown as a pure stand, was grazed by sheep three times in the first and second harvest years and once in the third. Crop growth was studied during the 8 weeks preceding each grazing.Sainfoin had a high proportion of green leaf and a high weight per unit area of leaf, and the stem as well as the leaf was readily eaten. The yield and persistence of sainfoin were poor, the number of plants and the number of shoots per plant were low, the development of leaf area was slow, and nitrogen content and digestibility were rather low.Red clover had a high proportion of green leaf, large leaves, high nitrogen content and fairly high digestibility, and the stem as well as the leaf was readily eaten. Yield was low except at the first two grazings of the first harvest year, and persistence was poor, there being a large number of plant deaths near the time of the second grazing.Lucerne was higher yielding and more persistent than the other legumes, with a satisfactory number of plants, a relatively large number of shoots per plant, a high rate of emergence of leaves and a relatively large amount of branching. The lucerne had a rather high proportion of stem, and the stem was of rather low digestibility and not very attractive to the sheep.The hybrid ryegrass yielded more herbage than the legumes, had a satisfactory and increasing number of tillers, increased in yield relatively early in spring and recovered well after defoliation. The proportion of green leaf was low by the end of each of the first two growth periods of each year, the leaves emerged at a rather slow rate in the later stages of a growth period, the crop had a relatively high proportion of cell wall and the stem in particular was relatively unattractive to the sheep.

SummaryAll combinations of four levels of potassium and two of nitrogen were applied in each of 2 years to a hill sward on a brown podzolic soil with an 8 cm peaty surface horizon anda very low level of extractable K. The sward had been surface-sown 11 years before with white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.). During the course of the experiment, harvesting was by cutting, with an average interval between cuts of 5 weeks. The previous management had been sheep grazing.The proportion of clover in harvested herbage was increased by applied K and reduced by applied N. The clover grew strongly in the 1st year of cutting management where K, but no N, was applied, but there was much less clover in the 2nd year on all plots. The concentration of K in both clover and grass was greatly increased by applied K, but only the clover responded strongly in terms of extra herbage produced. This suggests that grass growth was N-limited, whereas the clover had sufficient N from symbiotic fixation.Applied K increased the size and weight of clover leaves, the rate of extension of the stolon main axis, and the number and length of stolon branches, but did not affect the rate of emergence of leaves on the stolon main axis. Applied N had a generally negative effect on the aspects of clover growth and morphology which were measured. The length and weight per ryegrass leaf blade were generally slightly increased by both applied K and applied N.

SUMMARYIn a field which had been grazed by dairy cows for 26 years, the bulk density of both total soil and fine earth increased rapidly with depth down to 10–12 cm, but decreased below this depth. The bulk density was approximately twice as great in the 10–12 cm as in the 2–4 cm layer. Total porosity in the 10–12 cm layer was only 22%.Slitting the soil to penetrate the compacted layer approximately doubled net herbage accumulation and the net uptake of N, P and K, raising herbage production and uptake of nutrients from a low level to an acceptable one. Slitting tended to increase the concentrations of nitrate-N and K in herbage, but had little effect on the concentration of total N. Slitting increased the weight of ash-free root in the 10–20 cm depth range.

SummaryThe regrowth of Aberystwyth S. 23 perennial ryegrass, S. 24 perennial ryegrass, S. 59 red fescue and S. 170 tall fescue was studied in field swards, comparing four levels of applied nitrogen, for 8 weeks following a clearing cut. The clearing cuts were in mid-October, mid-February and mid-March in each of 3 years, different plots being used on each occasion.Grass yield was more closely related to solar radiation receipt than to temperature. When radiation during the 3 or 4 weeks before a period of study was added to radiation during the 8-week period, to incorporate some allowance for temperature, the amount of additional yield per unit of additional radiation comparing the first spring period with the autumn period was about the same as that comparing the second with the first spring period. Where no N was applied, there was little or no increase in yield above ground level or above 4 cm from week 1 to about week 6 in the autumn and first spring period, whereas where N was applied yield increased steadily, though rather slowly, during those 5-week periods. Response to N, measured as kg dry matter above 4 cm/kg N applied, was about twice as great in the second as in the first spring period; on the other hand response to N measured as number of days saved in reaching a given yield was greater in the first than the second spring period. The positive effect of applied N on relative growth rate occurred mainly in the rather early stages of regrowth, which seems to be typical of any time of year.Applied N increased the N and nitrate-N content of herbage and reduced the watersoluble carbohydrate content. Applied N increased the number of tillers and the proportion of yield above 4 cm. Yield below 4 cm was not much affected by N or by stage of regrowth. The ‘earliness’ in spring of S. 24, S. 59 and S. 170 compared with S. 23 was associated with greater height and a higher proportion of yield above 4 cm and not with higher above-ground yield. The ryegrasses responded more to N than the fescues in respect of yield above 4 cm and number of tillers. In 2 years in which the number of tillers was relatively low at the beginning of the spring periods of study, the number increased during those periods and there was a large positive effect of applied N, whereas, in a year in which the number was high initially, there was no increase during the periods of study and little response to N.

SUMMARYHerbage from a grass-white clover sward was dried in the field to the hay stage (< 0·3 g moisture/g dry matter) at four times of year in 2 years comparing, in each case, all combinations of three stages of maturity, three levels of applied nitrogen and three thicknesses of swath; 35, 55 and 75 days' regrowth, 0, 75 and 150 kg N/ha and, on average, 220, 474 and 728 g herbage dry matter/m2 were compared.The least mature herbage had the highest moisture content at the time of cutting and dried most quickly at a given swath thickness, being slightly drier than the more mature herbage at the hay stage. At the cuts in late May-early June and late Juneearly July, when the crop was predominantly grass, the application of nitrogen increased both the moisture content at the time of cutting and the initial rate of drying at a given swatli thickness, so that in the middle and later stages of drying there was no effect of applied N on moisture content. At the cuts in early and late August, herbage from the plots that had received no applied N, which contained a substantial amount of white clover, had the highest moisture content at the time of cutting, dried fastest at a given swath thickness and had the lowest moisture content in the later stages of drying. In the very early stages of drying, herbage in a thin swath lost water much faster than herbage in a thick swath, but subsequently the rate of drying was consistently faster in a thick than in a thin swath so that, by the hay stage, herbage in a tick swath was at least as dry as herbage in a thin swath. There was almost no interaction between the different types, of treatment.Rain during the drying period had little or no effect on the nitrogen content of the crop, but reduced digestibility by about 9 units. Stage of maturity and swath thickness did not affect the extent of this reduction in digestibility.

SUMMARYEffects of three levels of N application and four intervals between harvests on field swards of perennial ryegrass (Lolium perenne L.) were studied during 6-week periods in summer and spring. Ryegrass was compared with tall fescue (Festuca arundinacea Schreb.) in spring and autumn.The application of N increased the rate of production of leaf primordia, the number of leaf primordia per tiller, the length of the shoot apex, the rate of development of primordia into unemerged leaves, the number of leaves emerging, the number of live, emerged leaves per tiller, the leaf extension rate and weight of blade emerging and the net gain, per tiller per day, in blade length and weight. The application of N tended to reduce the number of unemerged leaves per tiller and the length of apex per primordium. Applied N retarded leaf death (whether measured as numbers, length or weight) during the first 2–3 weeks after application and accelerated death subsequently. During the 1st week of the summer periods, the net gain in green blade length and weight per tiller was doubled by 22 kg N/ha and trebled by 66 kg N (compared with nil). During the final fortnight of the summer periods, the net gain in green blade length and weight was less with the 6-than with the 3- or 2-week interval, and, in the case of the 6-week interval, the positive effect of applied N on the rate of development of primordia into unemerged leaves and on the number of leaves emerging had been lost.The ryegrass had more leaf primordia and unemerged leaves per tiller than the fescue, and a faster rate of development of primordia into unemerged leaves and of unemerged into emerged leaves.A ryegrass leaf spent a broadly similar length of time in each of the three stages, primordium, unemerged leaf and fully expanded live leaf, and about half as long as one of those stages as an emerging leaf. At nil N a leaf developed to about 6000 times its starting length (as a newly-formed primordium) in 67 days in summer; at high N a leaf developed to about 10500 times its starting length in 53 days. The percentage increase in length per day was greatest during the unemerged leaf stage.

SummaryThe effect of six intervals between harvests and three levels of N application on the number of tillers was studied in four ryegrass (Lolium) varieties in the first harvest year and in two varieties in the second and part of the third harvest years in a field experiment. Weight/tiller was recorded in the first 2 years and weight/green leaf and number of green leaves harvested were recorded in the first year.There was a large negative interaction between level of N and interval between harvests in respect of number of tillers, the number being increased by N with short intervals and tending to be reduced by N with long intervals. The interaction was larger in the second and third years than in the first. The negative interaction in respect of number of tillers and number of green leaves harvested was associated with a reduction in the percentage increase in yields of dry matter, digestible organic matter and N due to the application of N as the interval was increased. It is suggested that one should in general avoid a combination of high N and long intervals between harvests with present varieties of perennial ryegrass.The effects of interval between harvests, N application, variety and time of year on number of tillers and weight/tiller are discussed in relation to their effects on yield to show how tiller information can contribute to a better understanding of the ways in which yields are achieved. Rather low yields in the late summer and early autumn of the second harvest year were in many instances attributable to a rather low number of tillers rather than to low weight/tiller.There was a considerable increase in number of tillers between the end of one growing season and the early part of the next, suggesting that the period in which this increase is achieved may be an important one in relation to the continued vigour of the sown species.A reduction in annual yield of green leaf with extension of interval from 6 to 10 weeks with N applied resulted from a reduction in the number of green leaves harvested/harvest and in the number of harvests, which outweighed an increase in number of green leaves harvested/tiller and in weight/green leaf. Increasing the level of N with intervals of 3–6 weeks increased the number of tillers, the number of green leaves harvested per tiller and per unit area of ground and weight/green leaf and hence consistently increased green leaf yield.

SummaryFour varieties of Italian ryegrass (Lolium multiflorum), which have been found to differ in voluntary intake by livestock at the same level of digestibility, were examined in the year of sowing and in the two subsequent years in a field experiment. Eight dates of first harvest during May–June in the years after the year of sowing were compared. During May–June in these years the proportion of leaf in the crop was closely related to the stage of development of the crop relative to heading date, whereas yield and digestibility were more closely related to calendar date. As a result the later-heading varieties, S. 22 and Sabalan, had a higher proportion of leaf than the earlier-heading varieties, RvP and Tetila Tetrone, at a given yield and digestibility and this may at least partly account for higher intake in the former varieties. In addition, in Sabalan, the proportion of green leaf relative to dead was particularly high and the proportion of cell wall particularly low. The surface area per unit dry weight of leaf blade was much higher than that of ‘stem’, which may contribute to shorter retention time in the reticulo-rumen. Surface area per unit weight of both leaf blade and ‘stem’ declined with delay in date of first harvest.The yield of RvP relative to the other varieties was modest at the first harvest in the years after the year of sowing and high at subsequent harvests, in accord with National Institute of Agricultural Botany results. The high yield of RvP relative to the other varieties after the first harvest appeared to be associated with a relatively large number of tillers with their shoot apex below cutting height at the time of first harvest. It seemed that most of these tillers had emerged during the few weeks before that harvest. The proportion of tillers with their shoot apex below rather than above cutting height at the time of first harvest was higher in all four varieties than casual observation would suggest and the proportion remained rather high throughout May and June. The rapid rate of turnover of tillers in Italian ryegrass was confirmed.

SUMMARYOne hundred and forty different varieties of grass, from seven species, were harvested in spring, in 1, 2 or 3 years, at a D-value of 67 and dried at 25 °C. Moisture content was determined every 3 h for at least the first 48 h and less frequently thereafter until the grass was about dry enough to store as hay.Rate of drying was in the order tall fescue > Italian ryegrass = meadow fescue > timothy = cocksfoot > perennial and hybrid ryegrass. The perennial and hybrid ryegrass took twice as long to dry as did tall fescue. Tetraploid varieties of the ryegrasses took appreciably longer to dry than the diploid varieties. Apart from this there were some differences between varieties within a species in rate of drying. Differences in moisture content at cutting, in the proportion of leaf blade and in the number of leaf sheaths per ‘stem’ may have accounted for some of the differences between species and varieties in rate of drying. Further research is suggested.

SUMMARYThe regrowth of Aberystwyth S. 22 Italian ryegrass, S. 24 perennial ryegrass and S. 37 cocksfoot was studied in field swards with and without applied nitrogen during the 21 days following a cut or grazing, there being a total of five periods of study at different times of year and in different years.The dry-matter content of the harvested herbage deoreased by 4–8 percentage units on average from day 6 to day 18 of regrowth, supporting the evidence of earlier experiments with ryegrass and suggesting that a decrease at about this stage is typical. In the present experiments the same trend was evident after removal of surface moisture. Dry-matter content before removal of surface moisture was sometimes as low as 10%, which could adversely affect animal production. The water potential of fully expanded leaf blades was typically more negative on days 2 and 5 of regrowth than subsequently, so that the moderately high dry-matter content during the first week of regrowth seems to indicate some degree of moisture stress. Emerging leaves were less stressed than fully expanded ones during the very early stages of regrowth. Leaf water potential tended to be rather less negative in the cooksfoot than in the ryegrasses. The application of N reduced dry-matter content, but did not affect leaf water potential.The digestibility of the harvested herbage was little affected by the stage of regrowth. The cocksfoot was less digestible than the ryegrasses. The application of N generally increased digestibility, particularly in cocksfoot.

SummaryEffects of three levels of N application and four intervals between harvests on field swards of perennial ryegrass (Lolium perenne L.) were studied during 6-week periods in summer and spring. Ryegrass was compared with tall fescue (Festuca arundinacea Schreb.) in spring and autumn.An increase in the interval between harvests from 1 to 6 weeks allowed a larger, positive response to applied N to develop in respect of dry-matter yield, weight per tiller, and leaf blade and sheath length. Response to N was expressed more in terms of larger leaf blades than in a larger number of tillers. Tall fescue leaf blade size was increased more than that of ryegrass by a period of uninterrupted growth in May.Within 1 week of its application, N had increased the N content of both emerging and dying leaf blades and had increased the width and reduced the weight per unit area of the emerging blades. The positive effect of N on blade width (and on blade length where uninterrupted growth was allowed) and its negative effect on weight per unit area were ‘carried through’ the sward, to be recorded a second time when that generation of blades had become the dying blades.Applied N increased the number of tillers, the rate of emergence of new tillers, the proportion of tiller buds which developed into tillers, and the proportion of relatively young tiller buds which developed.

SummaryAll combinations of four harvesting treatments and two sowing dates were compared in each of 2 years in field experiments near Nicosia. In one of the years, two levels of applied nitrogen were compared. The harvesting treatments were: (1) a milk-stage cut, (2) a boot-stage cut and a regrowth cut, (3) a grazing-stage cut and a regrowth cut, and (4) three grazing-stage cuts and a regrowth cut. The sowing dates were (1) normal (12 November) and (2) early (15 October), with sufficient irrigation to ensure establishment.Applied nitrogen had virtually no effect on leaf growth, evidently because of high reserves of available nitrogen in the soil. Early sowing increased the rates of leaf emergence, extension and expansion up to the time of the first ‘grazing’ cut (when the first node was showing) and reduced the number of leaves which died in that period. Where growth was uninterrupted to the milk stage, early sowing did not affect the number of leaves produced by a main stem or primary tiller, but increased the longevity of the later leaves. Where there were three ‘grazing’ cuts, early sowing allowed time for the production of more and larger leaf blades, with longer sheaths, between the third 'grazing’ cut and the final harvest.The ‘grazing’ cuts considerably reduced the rates of extension and expansion and the final size of the leaves which emerged soon after a cut. There was good recovery subsequently, however, in rates of extension and expansion and final leaf size, particularly with October sowing.During almost all the period of leaf production on a main stem or primary tiller, several leaves (up to six) were expanding at the same time. The stage, during the period between emergence and death, at which a leaf blade reached its full length was typically half-way between emergence and death. Where growth was uninterrupted, area per leaf blade was positively correlated with both the number of days between the emergence of successive leaves and the number of days between emergence and death.

1. Lucerne was grown in a glasshouse under different moisture regimes in order to determine the effect of soil moisture content at the time of defoliating on subsequent yield.2. Drought conditions were found to reduce yield in the short-term, particularly in conditions in which demand for water was high, but the crop subsequently recovered when supplied with ample moisture. Defoliation during a drought period showed no long-term effect on yield.This work was carried out as part of the programme of crop-husbandry experimentation at the University of Cambridge School of Agriculture, and the author welcomes this opportunity of thanking Mr F. Hanley, Reader in Crop Husbandry, for advice and suggestions.