Showing papers in "The Journal of Agricultural Science in 1987"
TL;DR: In this paper, a computer model was described to simulate changes in soil mineral nitrogen and crop uptake of nitrogen by computing on a daily basis the amounts of N leached, mineralized, nitrified and taken up by the crop.
Abstract: The computer model described simulates changes in soil mineral nitrogen and crop uptake of nitrogen by computing on a daily basis the amounts of N leached, mineralized, nitrified and taken up by the crop. Denitrification is not included at present. The leaching submodel divides the soil into layers, each of which contains mobile and immobile water. It needs points from the soil moisture characteristic, measured directly or derived from soil survey data; it also needs daily rainfall and evaporation. The mineralization and nitrification submodel assumes pseudo-zero order kinetics and depends on the net mineralization rate in the topsoil and the daily soil temperature and moisture content, the latter being computed in the leaching submodel. The crop N uptake and dry-matter production submodel is a simple function driven by degree days of soil temperature and needs in addition only the sowing date and the date the soil returns to field capacity, the latter again being computed in the leaching submodel. A sensitivity analysis was made, showing the effects of 30% changes in the input variables on the simulated amounts of soil mineral N and crop N present in spring when decisions on N fertilizer rates have to be made. Soil mineral N was influenced most by changes in rainfall, soil water content, mineralization rate and soil temperature, whilst crop N was affected most by changes in soil temperature, rainfall and sowing date. The model has so far been applied only to winter wheat growing through autumn, winter and spring but it should be adaptable to other crops and to a full season. The model was validated by comparing its simulations with measurements of soil mineral N, dry matter and the amounts of N taken up by winter wheat in experiments made at seven sites during 5 years. The simulations were assessed graphically and with the aid of several statistical summaries of the goodness of fit. The agreement was generally very good; over all years 72% of all simulations of soil mineral N to 90 cm depth were within 20 kg N/ha of the soil measurements; also 78% of the simulations of crop nitrogen uptake were within 15 kg N/ha and 63% of the simulated yields of dry matter were within 25 g/m2 of the amounts measured. All correlation coefficients were large, positive, and highly significant, and on average no statistically significant differences were found between simulation and measurement either for soil mineral N or for crop N uptake.
312 citations
TL;DR: The excretion of purine derivatives in excess of endogenous contribution was closely related to the theoretically expected values and increased linearly with increasing microbial nucleic acid input in sheep.
Abstract: Two experiments were carried out to determine endogenous excretion of purine derivatives in steers and lambs, and to investigate the relationship between microbial nucleic acid input and urinary excretion of purine nitrogen. The endogenous excretion of allantoin after conversion of hypoxanthine, xanthine and uric acid to allantoin, was calculated to be 72 and 26 mg/kg W 0·75 per day in steers and lambs, respectively, when the dietary protein contained no nucleic acid nitrogen. The excretion of purine derivatives increased linearly with increasing microbial nucleic acid input in lambs. The excretion of purine derivatives in excess of endogenous contribution was closely related to the theoretically expected values. The average recovery was calculated as 0·96 for one sheep and 1·0 for the other.
292 citations
TL;DR: Mo supplementation delayed the onset of puberty, decreased the conception rate and caused anovulation and anoestrus in cattle without accompanying changes in Cu status or in live-weight gain.
Abstract: Two experiments were conducted to examine the effects of supplementation of a control diet of barley grain and barley straw containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 or 800 mg iron (Fe)/kg D.M. on puberty, fertility and oestrous cycles of cattle. Puberty occurred normally in control, Fesupplemented and control animals on a restricted intake whereas it was delayed by 12 and 8 weeks respectively by Mo supplementation. This effect of Mo was not due to the low Cu status since this was equally low in the Fe-supplemented animals, nor was it due to the reduced growth rate since puberty occurred normally in control animals that had a similar live-weight gain. A significant reduction in the pulsatile release of luteinizing hormone was observed within 11 weeks of the Mo supplementation and before any of the other clinical signs were evident, suggesting that Mo may be affecting puberty by altering the release of luteinizing hormone either directly or indirectly.Mo supplementation significantly reduced the percentage conception rate to 12–33% compared with 57–80% in control and Fe-supplemented animals. This effect was not dependent on the rate of live-weight gain which was standardized across the different treatments at approximately 0·6 kg/day. Within 12 weeks of the replacement of dietary Fe by Mo a lower conception rate occurred; replacing dietary Mo by Fe led to a normal conception rate within 12 weeks without any accompanying changes in Cu status or in the rate of live-weight gain. The plasma Mo concentrations, however, changed significantly during these alterations in dietary supplementation. The pre-ovulatory peak height of luteinizing hormone was significantly lower in animals on the Mo-supplemented diet compared with control and Fe-supplemented animals, but the administration of LHRH did not alter the conception rate.More Mo-supplemented animals failed to ovulate following prostaglandin induced synchronization in comparison with the other treatments, and by the 84th week a significantly greater number of Mo-supplemented animals (12/18) had become anoestrous compared with the other groups (2/30). Cu repletion of these anoestrous Mo animals for a period of 20 weeks did not result in resumption of normal oestrous cycles, but ovulation and oestrus were induced by progesterone and LHRH treatment. Results in the latter part of the study indicated that Mo caused superovulation.These data show that Mo supplementation delayed the onset of puberty, decreased the conception rate and caused anovulation and anoestrus in cattle without accompanying changes in Cu status or in live-weight gain. It is suggested that these effects of Mo are associated with a decreased release of luteinizing hormone that might be due to an altered ovarian steroid secretion.
124 citations
TL;DR: In this paper, Friesian cows were allocated to one of four diets for weeks 3-14 of lactation following two weeks on a common diet. The concentrates were designed to have similar concentrations of metabolizable energy and the diets were planned to provide similar intakes of digestible energy and crude protein.
Abstract: Twenty-four Friesian cows were allocated to one of four diets for weeks 3–14 of lactation following 2 weeks on a common diet. The diets (kg air-dry feed/day) were 7–2 kg hay and 10·8 kg either starchy or fibrous concentrates (60S and 60F) or 3·5 kg hay and 14·0 kg either starchy or fibrous concentrates (80S and 80F). Rumen samples were taken by stomach tube in weeks 10 and 12 of lactation and the digestibility of the diets was measured with four cows per treatment during weeks 13 and 14. The digestibility of the same feeds was also measured in sheep at maintenance.The principal carbohydrate constituents of the concentrates were barley, wheat and cassava in the starchy concentrates and citrus pulp, sugar-beet pulp and wheat feed in the fibrous concentrates. The concentrates were designed to have similar concentrations of metabolizable energy (ME) and the diets were planned to provide similar intakes of digestible energy and crude protein.Milk yield and composition were very similar for treatments 60S and 60F. With the higher proportion of starchy concentrates (80S), milk yield was about 20% greater than on 60S, fat concentration fell severely but protein and lactose concentrations were unaffected. With the higher proportion of fibrous concentrates (80F), milk yield and the protein and lactose concentration were similar to values on 60F but fat concentration was lower, though not nearly so low as on 80S. Milk energy yield was reduced by the higher proportion of concentrates but was unaffected by type of carbohydrates. Live-weight changes were small.In both the sheep, consuming at maintenance, and the lactating cows consuming at about 3 times maintenance, digestibility of dry matter, organic matter and energy was higher with the higher concentrate diets but was unaffected by type of concentrate. The digestibility of fibre was greater with the fibrous concentrates but the effect of level of concentrate inclusion was inconsistent. Digestibility coefficients were consistently lower for the lactating cows than for the sheep.The proportion of acetic acid in the rumen volatile fatty acids in the cows was higher and the proportion of propionic acid was lower with the fibrous concentrates. The differences were much greater with the higher proportion of concentrates.During weeks 15–22 of lactation the cows were reallocated to concentrate treatments and given hay ad libitum. Hay intake was about 1 kg/day higher with the fibrous concentrates but the difference was not significant. Hay intake fell by about 0·6 kg/kg concentrate intake for both concentrate types. No significant differences in milk yield or composition were established, probably because of incomplete adaptation even after 8 weeks.It is concluded that at concentrate intakes of about 10 kg/day, the source of carbohydrate in the concentrates has little effect on milk production when the concentrates are of similar ME concentration. However, at higher levels of concentrate inclusion, although the diets may have similar ME concentrations, important differences in the yields of fat, protein and lactose occur due to carbohydrate source and these can be related to differences in rumen fermentation.
112 citations
TL;DR: In general, crops at northern sites developed more slowly than those in the south and particularly the south-west of England, and there was less variation in the timing of apical stages for later sowings.
Abstract: An experiment to measure the variation in the phenological and apical development ofwinter wheat (cv. Avalon) in England and Scotland is described. Ten sites which ranged from Aberdeen (57·2° N), the most northerly, to Newton Abbot (50·6° N), the most southerly, were included in the survey, and at each site seed was hand-sown in mid-September, October and November 1983. Developmental stages and sampling procedures were precisely defined to ensure uniformity in scoring by the observers at each site. Temperatures during the growing season were in line with the long-term means, though spring was cooler at all sites and summer warmer at most. The range of monthly-mean temperatures between sites was about the same as the difference between consecutive months. The method of analysis of development rates and durations was in terms of thermal time, modified by sensitivity to photoperiod and a vernalization requirement that slowed early development until a number of days of low temperatures had been experienced. In general, crops at northern sites developed more slowly than those in the south and particularly the south-west of England. There was less variation in the timing of apical stages for later sowings. Developmental rates responded linearly to temperature and photoperiod, with the base temperature increasing for later phases of development. The effect of photoperiod in modifying the rate of development was apparent for all developmental phases from emergence to anthesis, longer days accelerating development, but there was no effect on the duration of the grain-filling period. Vernalization exerted its effect solely within the phase from emergence to double ridge, and had a major influence on the variation between sites only for the first sowing.
112 citations
TL;DR: In this article, the effects of supplementation of a barley-barley straw diet containing 4 mg copper (Cu)/kg dry matter (D.M.) with 5 mg molybdenum (Mo)/kg D.M. on the Cu status, growth and clinical condition of calves are described.
Abstract: Summary The effects of supplementation of a barley-barley straw diet containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 mg iron (Fe)/kg D.M. on the Cu status, growth and clinical condition of calves are described. Liver and plasma Cu concentrations declined rapidly within 12–16 weeks to levels indicating severe Cu deficiency in both the Mo- and Fe-supplemented groups. The changes in Cu status were similar for both supplements and did not differ significantly from each other. Clinical signs of Cu deficiency, as indicated by reduced growth rate and changes in hair texture and colour, were evident after 16–20 weeks only in animals on the Mosupplemented diet. The reduced growth rate was accompanied by a decreased food intake and reduced efficiency of food utilization. The Mo-supplemented animals also exhibited an altered Fe metabolism, particularly when the growth rate was affected. The results confirm earlier reports that the effects of Mo on growth and clinical condition are independent of its effect on Cu status and suggest that the altered production might be due to effects on the control of food intake, food utilization, or Fe metabolism.
104 citations
TL;DR: It is concluded that agronomists and breeders should increase amounts of early growth thereby increasing grain and dry-matter yields and the development of dynamic simulation models of pre-anthesis growth and water use.
Abstract: Relations between yield, water use and pre-anthesis growth were analysed for cropsof barley grown for three seasons at several sites in northern Syria. The relations obtained were compared with those for other cereal crops grown in similar regions of Mediterranean climates.Phosphorus fertilizer application increased the rate of crop development from emergence to floral initiation and advanced anthesis by up to 11 days. Grain and total shoot dry-matter yields were increased by fertilizer (nitrogen + phosphorus) applications at all sites in all years, in most cases without increasing total evapotranspiration. The increased dry matter at anthesis was produced without having used a larger proportion of the total evapotranspiration in the whole season. Consequently, the ratio of grain yield to total above-ground dry-matter yield (harvest index) and kernel weight were also relatively stable between sites and years, despite some very low amounts of post-anthesis water use. Grain yield appeared to be largely determined by anthesis and there were strong linear relationships between grain yield or total dry-matter yield and number of kernels. Differences in water use efficiency of crops given fertilizer between sites and years were closely related to the differences in amounts of winter growth.Some responses differed from those predicted from models of growth, water use and yield developed in other regions with similar climates. It is concluded that agronomists and breeders should increase amounts of early growth thereby increasing grain and dry-matter yields. Future research emphasis should also be on the development of dynamic simulation models of pre-anthesis growth and water use.
103 citations
TL;DR: The ED treatment was the most detrimental because the amount of light intercepted in the months of highest radiation was greatly reduced owing to the restricted leaf cover and the rate of water use fell from about 1·2 times to 0·6 times Penman potential transpiration rate.
Abstract: The growth and water use of sugar beet affected by early (ED) and late (LD) drought was compared with that of irrigated (I) and unirrigated (NI) controls. Mobile shelters were used to exclude rain from ED plots during June and July, and LD plots during August and September, respectively, whereas outside these periods the ED and LD plots were irrigated as necessary.The ED treatment affected the fibrous roots severely. Many of the roots in the top 60 cm of soil died and development of the root system below this depth was slow. Expansion of the leaf canopy slowed, radiation interception was reduced and the rate of water use fell from about 1·2 times to 0·6 times Penman potential transpiration rate. The LD treatment, which was imposed when the fibrous root system was already extensive, had little effect on the fibrous roots except in the top soil. The accessible soil water was quickly depleted and the resulting stress was accompanied by earlier senescence of leaves. The rate of converting intercepted light to crop dry matter was reduced in both treatments. However, the ED treatment was the most detrimental because the amount of light intercepted in the months of highest radiation was greatly reduced owing to the restricted leaf cover. The relative effects on growth are reflected in the final sugar yields which were 8·7, 10·5, 9·9 and 12·0 (±0·30) t/ha in the ED, LD, NI and I treatments respectively.More of the deep soil water was used in the drought-affected plots (particularly LD) than in the irrigated controls. Maximum depths of water extraction were 140–150 cm in ED and I plots and > 170 cm in LD plots. The highest uptake rates per unit length of root (20–40 μl/cm per day) were measured in the deepest part of the root system. At all depths, uptake rates declined as the soil dried. After correcting for overestimated water use where necessary, the ratios of final dry matter and sugar yields respectively to season-long water use (June–October) were close to 1·4 and 0·8 t/ha per 25 mm for all four treatments.
86 citations
TL;DR: A liquid suspension of sheep faeces is used as an inoculum in the in vitro determination of digestibility of feedingstuffs for ruminants, and the results correlated closely with the in vivo digestibilities.
Abstract: A method is described in which a liquid suspension of sheep faeces is used as an inoculum in the in vitro determination of digestibility of feedingstuffs for ruminants. The modified method was applied to 21 samples of grass, ten of lucerne, and a variety of other food materials. The results correlated closely (r = 0·98) with the in vivo digestibilities, and the relationship between in vitro and in vivo digestibilities was represented by the equation: in vivo digestibility = in vitro digestibility × 1·003.
72 citations
TL;DR: It is concluded that a breeding strategy combining selection for morphological characters thought to confer high yield potential, such as a more erect leaf posture and high number of grains per spikelet, with selection for grain yield per se has been successful in improving the grain yield of durum wheats adapted to north-west Mexico.
Abstract: SUMMARY Two trials designed to measure progress in the yield of durum wheat cultivars released in Mexico by the Institute Nacional de Investigaciones Agn'colas over the period 1960-84 were grown in the Yaqui Valley, Sonora, Mexico, during the 1983—1 and 1984-5 cropping seasons. The trials compared grain yield, above-ground biomass, harvest index (ratio of dry grain yield to dry above-ground biomass), yield components, grain-growth rates and phenological characters for eight key cultivars and the modern advanced line, Carcomun 'S', when grown at a high level of agronomic inputs and management. The grain yield of durum wheat was estimated to have risen for 25 years of breeding from 3-70 to 8-40 t/ha. The estimated average annual rates of increase in grain yield for the periods 1960-71 and 1971-85 were 251 and 121 kg/ha respectively. Grain yield improvements were based on a linear increase in the number of grains/m 2 over the 25-year period, the result of more grains per spikelet. An improved above-ground biomass at maturity was a feature of the two modern genotypes, Altar 84 and Carcomun ' S'. Harvest index increased with each new cultivar up to the release of Mexicali 75 in 1975, but thereafter the higher grain yields achieved with the modern genotypes were not associated with a higher harvest index. Thousand-grain weight remained steady for the released cultivars but fell slightly for the advanced line Carcomun 'S'. Improvements in yield were not associated with a longer cropping cycle. It is concluded that a breeding strategy combining selection for morphological characters thought to confer high yield potential, such as a more erect leaf posture and high number of grains per spikelet, with selection for grain yield per se has been successful in improving the grain yield of durum wheats adapted to north-west Mexico. Improvements have come not only in the size of the grain sink and the efficiency of assimilate partition to grain but also in the biomass produced above ground.
72 citations
TL;DR: Gross efficiency of energy utilization was significantly increased by fishmeal supplementation suggesting an improved balance of nutrients compared with the silage alone diet and the overall effect of oestradiol-17β on protein gain was not significant.
Abstract: The effect of oestradiol-17β on the response to fishmeal supplementation of grass silage was studied in young growing cattle. Voluntary intake and live-weight gain were recorded over 63 days with 36 British Friesian male castrates (initial live weight (LW) 119 kg) offered silage alone (C) or with 50 (FM1), 100 (FM2), or 150 (FM3) g fishmeal/kg silage dry matter. Twelve calves were allocated to each of treatments C and FM3 and six to treatments FM1 and FM2. Half of the calves on each treatment were ear-implanted with oestradiol-17β (Compudose 365) at the start of the experiment. The calves on treatments C and FM3 were slaughtered after 75 days and chemical analysis conducted on half of each carcass. The silage had an organic-matter digestibility in vivo of 0·794 and was well-fermented, with a pH of 3·7. Intake averaged 24·2±0·42 g D.M./kg LW over all the treatments and live-weight gain was 0·77 kg/day on the silage alone. There was a significant ( P P
TL;DR: The effect of insect pollination on plant development and seed yield of winter oil-seed rape, cultivar Jet Neuf, was investigated by comparing plots caged with a honeybee colony and uncaged and 'open-pollinated' by naturally occurring insects.
Abstract: The effect of insect pollination on plant development and seed yield of winter oil-seed rape, cultivar Jet Neuf, was investigated by comparing plots caged with a honeybee colony, plots caged to exclude insects and plots uncaged and 'open-pollinated' by naturally occurring insects. Plants in the bee-pollinated plots finished flowering earlier, showed more advanced pod growth, and were shorter than those in the plots without bees. Pods from the plots with honeybees contained more seed post-flowering than those from plots without honeybees but the proportion of them that grew into mature seeds for harvest was determined by water availability during seed growth.
TL;DR: A method of assessing genotypic stability is proposed in the case where genotype yields are measured across environments but no concomitant environment data are available.
Abstract: SUMMARY A method of assessing genotypic stability is proposed in the case where genotype yields are measured across environments but no concomitant environment data are available. The method is introduced in a practical context and two examples of its use with actual data are presented. The method depends ultimately on the choice of a suitable measure of similarity between genotypes. Most of the stability information appears in a sequence of plots, where stable genotypes are immediately highlighted as consistently more remote points.
TL;DR: In this article, the authors performed a kinetic study on two mature red deer stags during the period of maximum rate of Ca deposition in the antlers, calculated from the model of Ca metabolism, were 58·4 and 38·6 mg Ca/kg W per day.
Abstract: Kinetic studies of Ca metabolism, using 45CaCl32, were carried out on two mature red deer stags during the period of maximum rate of Ca deposition in the antlers. They were offered green-feed oats to provide energy for maintenance; the diet provided approximately 42mg Ca/kg W per day.Ca appeared to be irreversibly lost from the circulation into the antlers and could be treated for kinetic purposes in the same way as loss of Ca from the body in milk. The size of the rapidly exchangeable Ca pool in the body, excluding the antlers, was 0·21 g/kg W, similar to estimates for lactating cattle. Rates of Ca deposition in the antlers of the two stags, calculated from the model of Ca metabolism, were 58·4 and 38·6 mg Ca/kg W per day. Net endogenous loss was 6–7 mg Ca/kg W per day, much lower than estimates available for other ruminant species. Only 25–40% of Ca requirement or 11–24 mg Ca/kg W per day was derived from the diet, suggesting that the availability of Ca in greenfeed oats is much lower than current estimates for forages. Bones removed on completion of the experiment showed evidence of considerable skeletal demineralization.In other stags subjected to stable Ca balances at the same stage of antler growth, while consuming ryegrass-white clover forage, 60–80% of Ca requirement was derived from the diet, with calculated rates of true absorption of 32–46 mg Ca/kg W per day. These rates of Ca absorption are low compared with values observed in other ruminants at times of high Ca demand such as during lactation.
TL;DR: This article showed that removing the rumen anaerobic fungi from sheep fed chemically-treated barley straw diets resulted in elevated proportions of propionic acid in rumen liquor (from ca. 0.15 to 0.30).
Abstract: Elimination of the rumen anaerobic fungi from sheep fed chemically-treated barley straw diets resulted in elevated proportions of propionic acid in rumen liquor (from ca. 0.15 to 0.30). Subsequent inoculation of these sheep with a pure culture of fungus decreased propionate concentrations within 3 days to the levels observed in control animals that possessed abundant fungal populations throughout the experiment. Confirmation that propionate itself was not responsible for the elimination of the fungi was provided by the results of a second experiment in which intraruminal infusions of propionic acid failed to reduce fungal growth or prevent recolonization in sheep previously rendered fungi-free. In a third experiment with sheep fed untreated barley straw, monensin supplementation produced the well known elevation of propionate concentrations. However, this treatment also resulted in the elimination of rumen anaerobic fungi from the animals. The magnitude of the increased concentration of rumen propionic acid, resulting from the elimination of the anaerobic fungal flora, indicates an important role for the fungi in the fermentation of high-fibre diets. In addition, these findings indicate that the well known elevation of propionate levels produced by monensin may likewise be effected directly by removal of the rumen anaerobic fungi.
TL;DR: The initiation of leaf and spikelet primordia was studied at sites ranging in latitude from Newton Abbot to Aberdeen in crops sown in the middle of September, October and November 1983 with a constant rate of leaf initiation and a constant and more rapid rate of spikelet initiation.
Abstract: The initiation of leaf and spikelet primordia was studied at sites ranging in latitude from Newton Abbot (50·6°N) to Aberdeen (57·2°N) in crops sown in the middle of September, October and November 1983. The rate of primordium initiation tended to decrease from south to north but there were also marked differences between quite close sites.The rate of leaf initiation increased with temperature but photoperiod had little effect; the rate of spikelet initiation was affected both by temperature and by photoperiod. There were differences in the total number of leaves initiated which were only partlyexplained by differences in vernalization.Expressing leaf and spikelet initiation rates in terms of thermal and photo-thermal time respectively showed a constant rate of leaf initiation and a constant and more rapid rate of spikelet initiation.
TL;DR: The data suggest that at rates typical of farm practice significant losses of phosphorus and potassium from the rooting zone would be unlikely to occur and may not necessarily have reduced herbage quality despite marked changes in sward botanical composition.
Abstract: A field experiment is described in which three rates of pig and cow slurry were applied to a ryegrass sward over a period of 16 years. The experiment included control plots and plots receiving fertilizer supplying 200 kg N, 32 kg P and 160 kg K/ha per year.The slurry nutrient concentrations were similar to published values. Pig slurry was more variable than cow slurry and both varied significantly from year to year. Slurry was applied at 50, 100 or 200 m3/ha per year, with each rate divided into three equal applications.Even the highest slurry application rate did not depress herbage yield, which showed a typical response curve to the amount of soluble nitrogen applied. The ammoniumnitrogen content of slurry (61% on average) gave an adequate measure of its effect on herbage yield when it was applied three times per year in spring and summer.Recovery of phosphorus in the herbage averaged 30% from pig slurry, 40% from cow slurry and 66% from-fertilizer. Pig slurry supplied more phosphorus than did cow slurry, and herbage phosphorus content was significantly correlated with the amount applied. Much of the slurry phosphorus may have been organically bound and not available to plants in the short term.Recovery of potassium from pig slurry and fertilizer was nearly 90% and from cow slurry about 70%. Cow slurry supplied potassium in excess of crop requirements so that it accumulated in the soil under the largest dressing. Soil phosphorus reserves declined under the smallest dressing of cow slurry but were maintained at higher application rates. The pig slurry produced a marked accumulation of phosphorus under the largest dressing. The substantial accumulations of phosphorus and potassium from pig and cow slurry respectively gave marked penetration of the soil below 10 cm depth only at the highest application rate. The data suggest that at rates typical of farm practice significant losses of phosphorus and potassium from the rooting zone would be unlikely to occur.The main invading plant species were Agrostis stolonifera L. and Poa spp. Small slurry dressings produced a similar botanical composition to that of plots given fertilizer. Increasing slurry application rates decreased the proportion of L. perenne and increased that of A. stolonifera but only under the largest dressing did L. perenne fall to a small proportion of the sward and A. stolonifera become very dominant. L. perenne made maximum contribution to herbage dry-matter yield early in the season while the proportion of A. stolonifera increased as the season progressed.Under these conditions even extremely large slurry dressings did not depress herbage yield and may not necessarily have reduced herbage quality despite marked changes in sward botanical composition.
TL;DR: In this paper, the cell walls from mature stems of three tropical grass species (Digitaria decumbens (pangola), Setaria anceps (cv. Kazangula), and temperate barley straw, were analysed for lignin, carbohydrate, and the maj or acyl groups ferulate, ρ-coumarate and acetate.
Abstract: Cell walls from mature stems of three tropical grass species (Digitaria decumbens (pangola), Setaria anceps (cv. Kazangula) and sugar cane), and temperate barley straw, were analysed for lignin, carbohydrate, and the maj or acyl groups ferulate, ρ-coumarate and acetate. Samples were incubated in nylon bags in the rumen of sheep in a 4 x 4 latin-square design, and rates of disappearance of cellulose, hemicellulose, xylose, arabinose, ferulate, ρ-coumarate and acetate were determined during 60 h incubation. Interspecies differences in cell-wall chemistry appeared largely in the variable degree of acylation with p-coumaric acid (1·0–3·3%) and acetate (0·5–3·6%), and the high glucose concentration in the hemicellulose from pangola (17%) and Setaria (9%). Barley had much lower concentrations of these components than the tropical species. After 24 h incubation, losses of cellulose and acyl groups were greatest from pangola, whereas hemicellulose and its major components xylose and arabinose were degraded to the greatest degree from barley straw. Setaria cell-wall components were generally more resistant to degradation than the other species. No relationship was found between the concentration of any cell-wall constituent and degradability measurements. Nor were changes in microbial population, indicated by measuring the accumulation of cystine on the fibres, related to the rate or degree of degradation of any of the measured cell-wall constituents. Lignin was fractionated with alkali into insoluble and soluble fractions. The latter (25–50% of original lignin) gave high interspecies correlations with the degradability of total hemicellulose and its component monosaccharides. It was concluded that variability in the biodegradability of the cell walls was more likely due to in situ structural features, such as cross-linking between polymers, than to the concentration of any particular cell-wall constituent.
TL;DR: In this paper, a management-oriented study of range, livestock and Maasai ecology in the wildlife conservation and pastoralist land use Ngorongoro Conservation Area (NCA) quantifies spatial and temporal variation in range resources for three main study sites over a 2-year period.
Abstract: This management-oriented study of range, livestock and Maasai ecology in the wildlife conservation and pastoralist land use Ngorongoro Conservation Area (NCA) quantifies spatial and temporal variation in range resources for three main study sites over a 2-year period. Livestock response is analysed in terms of biomass densities, habitat and pasture utilization, activity, herd size, composition and dynamics. Milk production is investigated together with the main ecological factors influencing yields. A household survey of the Maasai food system suggests that pastoral products now provide an annual average of 40% dietary energy intake, the remainder being supplied by grain. These findings form the basis of our analysis of the growing friction between the Conservation Authority and the pastoralists. Pastoralist livestock closely resemble wild ungulate utilization of NCA range resources. A combination of disease interactions and administrative restrictions allow wildlife to establish preferential access to critical grazing resources. Our results in the context of other work suggest that contrary to popular opinion pastoralist land use is an ecologically appropriate and efficient form of livestock management. There is no adverse impact on the conservation values of NCA. Despite average fertility and mortality levels pastoralist herds show progressive decline due to offtake for grain purchase. Imposed policies restrict grazing, ban cultivation and maintain poor conditions for livestock trade and grain supply. Possible interventions and their potential impacts are considered and management compromises which could benefit both pastoralists and wildlife are proposed.
TL;DR: In this paper, the effect of sowing date (September v. October) on both crop and soil NO3-N was compared, as well as the effects of soil type and previous crop (potatoes v. oats and wheat v. beans).
Abstract: Soil NO3-N and NH4-N were measured to 90 cm depth in autumn and again in spring, under several sets of winter wheat experiments, on contrasting sites. Crop samples were taken throughout the growing season, both before and after the fertilizer N was applied, to measure N uptake. The amount of NO3-N in soil at the outset of growth in autumn was related to the uptake of N by wheat not given any fertilizer N until April.The effect of sowing date (September v. October) on both crop and soil N was compared, as also was the effect of soil type (retentive of NO3-N v. readily leached) and previous crop (potatoes v. oats and wheat v. beans).The amounts of NO3-N in the soils in autumn related well with previous crop and declined gradually during winter on the heavier soils, but rapidly on the sandy soil, in the latter case as a consequence of leaching. On the heavier soils, where little leaching occurred, the decline in soil NO3-N related well with the amount of N taken up by September-sown wheat during autumn and winter, but not with that taken up by October-sown wheat, where NO3-N accumulated in the soil during winter, because uptake was so small. Hence delayed sowing enhanced the likelihood of losses of NO3-N by leaching or by denitrification. On the sandy soil at Woburn, whilst the September-sown wheat removed more N than the October-sown, losses of NO3-N by leaching were severe, so that late winter growth was restricted by shortage of N in soil, and the amount of N taken up was far smaller than at Rothamsted.The soil measurements distinguished between the NO3-N residues remaining after beans or wheat in the same field and between residues after oats or potatoes on soils of the same soil series, but in different fields on the same farm.The amount of NO3-N in soil and the N taken up by wheat in February-March were together used to adjust the amount of fertilizer N applied in April, using a balance sheet approach to meet a specific yield objective. Some of the N uptake data from these experiments are presented. This should aid the calculation of N requirement during specific growth periods and thus help improve the prediction of fertilizer N dressings in spring.
TL;DR: In this paper, an analysis of chickpea experiments carried out in northern Syria during the 1980-1 and 1981-2 growing seasons showed that both intercepted solar radiation and its rate of conversion to dry matter were variable components of dry-matter production.
Abstract: An analysis of chickpea experiments carried out in northern Syria during the 1980–1 and 1981–2 growing seasons showed that both intercepted solar radiation and its rate of conversion to dry matter were variable components of dry-matter production. Among the sources of variation in the experiments, the most important factor affecting both interception and utilization of solar radiation was site. Winter planting also led to increased solar radiation interception and utilization. Used in conjunction with chickpea lines resistant to blight, winter planting seems likely to lead to increased productivity. In higher rainfall areas, where the crop is usually grown, such an increase would be of commercial significance. In drier areas, winter planting would enable the cultivation of chickpea as a subsistence crop.
TL;DR: In this article, the effects of the time of sowing on growth and chemical composition of carrots grown from May to November were studied during 3 years, and the results did not indicate the presence of a well defined stage of biochemical maturity in the autumn when carrot roots are expected as most suitable for harvest and subsequent long-term storage.
Abstract: The effects of the time of sowing on growth and chemical composition of carrots grown from May to November were studied during 3 years.Delaying sowing for 1 or 2 months after the beginning of May resulted in a reduction in the growth of both roots and foliage and gave roots with lower dry-matter content and glucose/fructose ratio but higher amounts of hexoses, total nitrogen and amino nitrogen in root dry matter. Sowing date had no influence on the concentration of sucrose, phosphorus, potassium, calcium and magnesium in root dry matter up to 137 days from sowing. Carotene decreased only after the last sowing. Sucrose concentration of the roots increased throughout the periods studied irrespective of the time of sowing. The longer the growing period the higher was the sucrose concentration. The concentration of hexoses decreased from the first harvest at 70 days to reach a constant level at about 130 days from sowing.The results did not indicate the presence of a well-defined stage of biochemical maturity in the autumn when carrot roots are expected as most suitable for harvest and subsequent long-term storage.
TL;DR: Water stress during the period when tubers are initiated may reduce the final number of tubers and increase the incidence of common scab in susceptible cultivars and it is important to be able to estimate the time of tuber initiation.
Abstract: Water stress during the period when tubers are initiated may reduce the final number of tubers (MacKerron & Jefferies, 1986) and increase the incidence of common scab (Streptomyces scabies) in susceptible cultivars (Lapwood & Hering, 1970). It is important, therefore, for the maintenance of a large number of tubers and for the limitation of scab, to be able to estimate the time of tuber initiation. Tuber initiation has been defined differently by a number of workers (e.g. Sale, 1979; Sands, Hackett & Nix, 1979; O'Brien et al. 1983; MacKerron & Jefferies, 1986) based on either the number or proportion of stolon apices that have reached a certain size (usually twice the diameter of their stolons). These are definitions of tuber growth rather than development and require destructive sampling at frequent intervals for recognition of the event. Temperature has a major influence on the rates at which plant organs develop so that the time taken to reach a given developmental stage may be related to thermal time, defined as the time-integral of temperature (Jones, 1983). In potato the physiological age of tubers (Wurr, 1978; Allen et al. 1979; O'Brien et al. 1983), sprout development and extension (MacKerron, 1984), and the initiation of leaf primordia (Kirk, Davies & Marshall, 1985) have been related to thermal time. In a model of the development and bulking of potatoes Sands et al. (1979) used a single non-linear function to describe the effects of time and temperature on several development processes including tuber initiation. That function did not adequately describe the time taken to tuber initiation and Sands et al. (1979) did not then use tuber initiation as an important stage in their model.
TL;DR: In this paper, an increase in blood volume during acute heat stress occurred with an increase of both plasma and cell volume, and an elevation of plasma water coincided with an increased in plasma protein and glucose.
Abstract: During 5 h of acute heat exposure (41 °C), there were increases in the heart rate from 43±2 (S.E.) to 51 ± 1 beats/min, respiratory rate from 26±4 to 86± 16 breaths/min and rectal temperature from 38·5 ± 0·1 °C to 39·7 ± 0·2 °C. The flow rate of liquid from the rumen and body water turnover significantly increased while biological half life of chromium-51 ethylenediaminetetra-acetate in the rumen and tritiated water decreased from 12·9 ± 2·5 and 87·7 ± 6·8 h to 9·3 ± 2·0 and 49·2 ± 5·7 h respectively. An increase in blood volume during acute heat stress occurred with an increase of both plasma and cell volume. An elevation of plasma water coincided with an increase in plasma protein and glucose. There is evidence that the increase in plasma water during heat exposure came from extravascular tissue space and/or from the digestive tract.
TL;DR: It is suggested that an inadequate intake of sodium is an overlooked factor of the pathogenesis of this disease and that a low sodium intake influences the absorption of Mg in a similar manner as it has been observed with a high K intake.
Abstract: Three sheep, equipped with cannulae in the dorsal rumen sac, abomasum and ileum, were fed a low sodium diet of artifically dried young grass. Mean daily intake of sodium was 310 mg. The sheep were given daily supplements of 0 or 2·3 g sodium by an intraruminal infusion.The concentration of K in mixed saliva and ruminal fluid from the sheep not given sodium supplements increased and the concentration of Na decreased markedly. The changes in the ion concentrations were associated with an increase of the transmural potential difference across the ruminal epithelium.The altered ion concentrations of Na and K in the ruminal fluid and the increased potential difference were accompanied by a decrease in Mg absorption from the forestomachs. The apparent availability of Mg from the gastrointestinal tract decreased from 34·5 (sodium supplementation) to 22·3 (low sodium intake).It is suggested that a daily intake of Na of 310 mg did not cover the sodium requirement of these sheep and that a low sodium intake influences the absorption of Mg in a similar manner as it has been observed with a high K intake.The results are discussed in context of grass tetany in ruminants. It is suggested that an inadequate intake of sodium is an overlooked factor of the pathogenesis of this disease.
TL;DR: The results are discussed in terms of the significance of urine-affected areas in determining a patchy distribution of clover in grazed swards; the role of animals in the transfer of fixed N from clover to grass is considered.
Abstract: The effect of artificially applied urine on clover performance in a perennial ryegrasswhite clover sward grazed by sheep was examined during summer. Sheep urine or deionized water (51/m2) was applied to areas (2·70 × 1·25 m) which were protected from subsequent excretal return by graze-through cages. Grass and clover populations, nitrogen-fixing activity, soil nitrogen and soil pH were monitored over the following 90-day period.Urine reduced clover population density, stolon length and dry weight but had little effect on number of grass tillers. Nitrogen-fixing activity of clover was reduced initially to less than 30% of control values, perhaps owing to high levels of soil inorganic nitrogen inhibiting fixation, although osmotic effects due to the high salt concentration in urine cannot be discounted. The lower levels of activity at later dates were due largely to reduced clover in urine-treated areas. Soil pH (0–5 cm) was increased by about 0–5 units 3 days after urine application, with a smaller increase in the 5–10 cm horizon. Recovery of urine nitrogen in the soil mineral N pool was at best 27% of the added nitrogen.The results are discussed in terms of the significance of urine-affected areas in determining a patchy distribution of clover in grazed swards; the role of animals in the transfer of fixed N from clover to grass is considered.
TL;DR: It appears that whilst increased flower density in a canopy might be expected to contribute to increased seed yield, increased reflectivity by petals may have a negative effect on yield.
Abstract: Flowers were present over a period of approximately 6 weeks in 12 varieties of oil-seed rape. A linear relationship was found between flower cover (maximum 74%) and photon reflectivity (400–700 nm) which increased from around 0–047 during vegetative growth to 0.195 for a canopy in full flower. Reflexion and absorption of photons by flowers reduced light available to the leaf canopy and immature pods. Spectral measurements indicate that flowering canopies reflect substantially more radiation and absorb less than vegetative canopies between 500 and 700 nm but reflect less and absorb slightly more between 400 and 500 nm. Seed yield was not strongly correlated with estimates of the radiation absorbed by the leaf canopy under the flower layer. It appears that whilst increased flower density in a canopy might be expected to contribute to increased seed yield, increased reflectivity by petals may have a negative effect on yield. Breeding for reduced petal size or for apetalous lines may result in improved yields by producing more efficient light distribution within the canopy.
TL;DR: The results of this study demonstrate that properly managed short-duration genotypes of pigeonpea may have considerable potential for increased yield from multiple harvests in environments where winters are warm enough to permit continued growth.
Abstract: Environmental and cultural factors that may limit the yield of short-duration pigeonpea were investigated over three seasons. Plants in the peninsular Indian environment at Patancheru grew less and produced less dry matter by first-flush maturity than at Hisar, a location in northern India where the environment is considered favourable for the growth of short-duration pigeonpea. However, with a similar sowing date in June, the mean seed yields of three genotypes, ICPL 4, ICPL 81 and ICPL 87, were very similar, at about 2·3 t/ha, in both environments. This was mainly due to the higher ratio of grain to above-ground dry matter at Patancheru. In addition to the first harvest, all genotypes showed a potential for two more harvests owing to the warm winters at Patancheru. The potential for multiple harvests was particularly high in ICPL 87, which yielded 5·2 t/ha from three harvests in 1982–3, 3·6 t/ha from two harvests in 1983–4, and 4·l t/ha from three harvests in 1984–5. The optimum plant population density at Patancheru was 25–35 plants/m2 for ICPL 87, but was higher for the other two genotypes.
At Patancheru, the total dry-matter and seed yield of first and subsequent harvests were significantly reduced by delaying sowing beyond June. Generally, the second- and the third-harvest yields were lower on vertisol than on alfisol under both irrigated and unirrigated conditions.
The total yield of ICPL 87 from two harvests was far higher than that of a well-adapted medium-duration genotype BDN 1, grown over a similar period. The yield advantage was greater on the alfisol because of the better multiple harvest potential of this soil. The results of this study demonstrate that properly managed short-duration genotypes of pigeonpea may have considerable potential for increased yield from multiple harvests in environments where winters are warm enough to permit continued growth.
TL;DR: In this article, the cows in each group received either 11kg/day fresh weight of concentrate S in which the principal energy source was cereal starch, or 9 kg/day of concentrate F containing mixed high quality fibre sources plus 2 kg/d fresh weight S. The cows in group A were offered silage individually through Calan Broadbent gates while those in group B were given 24 h/day access to a self feed silage clamp.
Abstract: Ninety-nine lactating British Friesian cows, in their second and subsequent lactations, were divided into two groups receiving ad libitum grass silage. The cows in group A were offered silage individually through Calan Broadbent gates while those in group B were given 24 h/day access to a self-feed silage clamp. The crude protein (CP), acid-detergent fibre (ADF), neutral-detergent fibre (NDF), in vitro digestible organic matter and estimated metabolizable energy (ME) values in the D.M. of the silage were 140, 373, 584, 610g/kg D.M. and 9·7 MJ/kg D.M. respectively. The cows in each group received either 11kg/day fresh weight of concentrate S in which the principal energy source was cereal starch or 9 kg/day fresh weight of concentrate F containing mixed high quality fibre sources plus 2 kg/day fresh weight of concentrate S. The CP, ADF, NDF, starch and sugar concentrations in concentrates S and F were 203, 71, 204, 444, and 44 and 202, 147, 329, 116 and 149g/kg D.M., respectively. The only significant difference produced by method of silage allocation was that groupfed cows gained more live weight ( P . Over the whole experimental period the mean silage D.M. intake of cows fed concentrate F in group A was 0–5 kg/day higher than those fed concentrate S. However, in early lactation the benefit to silage intake in favour of concentrate F was 1 kg D.M./day. In group A estimated intakes derived from calculated ME inputs and outputs were markedly lower than the observed intakes, but were similar to correspondingly derived estimates for group B. Although concentrate type did not affect milk yield, concentrate F was associated with a higher fat concentration and yield (P 0–05) but a lower protein concentration (P 0·001) and a slightly lower yield. The in vivo digestibility coefficients for D.M. and organic matter determined in lactating dairy cows given concentrates S and F respectively were similar (0·724 v. 0·716 and 0·749 v. 0·742) but that for ADF was significantly ( P v. 0·673) in the ration containing concentrate F than in that containing concentrate S. Estimates of the mean efficiency of utilization of the production ME made on a weekly basis were unaffected by concentrate type.
TL;DR: The impact of age on the productivity of sown pastures of green panic (Panicum maximum var. trichoglume cv. Petrie) growing on black earth soil in south-east Queensland was measured from 1976 to 1981.
Abstract: The impact of age on the productivity of sown pastures of green panic (Panicum maximum var. trichoglume cv. Petrie) growing on black earth soil in south-east Queensland was measured from 1976 to 1981. During winter and spring, weaner steers grazed at 2·4 animals/ha on summer-spelled pastures which, in each year, were 1, 2, 3, 4 and 5 years old. Pastures were given 58 kg N/ha as urea each year. Live-weight gain averaged 74 kg/head on 1-year-old pasture but only 35 kg/head on 5-year-old pasture, with most of the reduction in weight gain in winter (June to August) occurring up to age 3 years, and with most of the reduction in spring (September to November) occurring for pastures older than 3 years.The decline in animal production was not caused by changes in species composition of the pasture. Rather, weight gain on older pastures was restricted by pasture quality in winter and by reduced pasture growth in spring, but not by presentation dry-matter yield. The decrease in pasture productivity seemed to be primarily due to reductions in available soil mineral N with age, since the N concentration of plant shoots decreased as a pasture aged. Tt is postulated that the immobilization of N in decomposing grass litter is a primary cause of productivity decline in ageing pastures.