Showing papers in "The Journal of Agricultural Science in 1997"

Nutrients and antiquality factors in different morphological parts of the Moringa oleifera tree.

Abstract: Moringa oleifera grows throughout most of the tropics and has several industrial and medicinal uses The objective of this study was to evaluate the potential of different morphological parts of this tree as animal feed The crude protein (CP) content of leaves, soft twigs and stems was 260, 70 and 60 g kg -1 respectively About 64, 79 and 67 % of the total CP present in the leaves, twigs and stems respectively was found to be degradable after 24 h in the rumen The protein insoluble in acid detergent fibre (ADIP), considered unavailable to animals, in these samples was 30, 150 and 170 g kg -1 respectively About 87 % of the total CP was in the form of true protein in the leaves (60 and 53 % in twigs and stems respectively) The leaves had negligible amounts of tannins (12 g kg -1 ), and trypsin and amylase inhibitors, lectins, cyanogenic glucosides and glucosinolates were not detected The saponin content of the leaves was 80 g kg -1 as diosgenin equivalent, which did not show any haemolytic activity The phytate content of the leaves was 21 g kg -1 Tannins, saponins, cyanogenic glucosides and glucosinolates were detected in twigs and stems but the concentrations were negligible Trypsin and amylase inhibitors were not detected in twigs and stems Phytate contents of both twigs and stems were c 30 g k -l In leaves, amounts of all the essential amino acids were higher than the amino acid pattern of the FAO reference protein and comparable to those in soyabeans The CP and lipid contents of the kernel were 370 and 420 g kg -1 respectively, and the CP of the meal (fat-free) was 610 g kg -1 The kernels and meal are extracted with water and the extract is used for the purification of water in some developing countries The residues left after water extraction of kernels and meal (designated as extracted-kernel and extracted-meal) had a CP content of 350 and 700 g kg -1 respectively and all of this CP was in the form of true protein After taking into account the ADIP contents in these samples, c 38 and 69 % of the total protein was calculated to be available in the post-rumen in extracted-kernel and extracted-meal respectively The pepsin digestibility of these samples was 91 and 84 % respectively The sulphur-containing amino acids in kernel proteins were present at higher concentrations than those specified in the amino acid pattern of the FAO reference protein but other essential amino acids were deficient Amongst the antinutritional factors mentioned above, glucosinolates and phytate were present in appreciable amounts (655 μmol/g and 41 g kg -1 respectively) in meal Haemagglutination activity was also detected in the meal The extracted-meal was virtually free of all the antinutritional factors examined except for phytate (67 g kg -1 ) The leaves of Moringa oleifera and the residue obtained after the recovery of oil and coagulants can be good sources of proteins for animal feeds

Optimizing wheat grain yield: effects of Rht (gibberellin-insensitive) dwarfing genes

Abstract: Four sets of near-isogenic lines carrying different combinations of the alleles Rht-B1b, Rht-D1b and Rht-B1c for gibberellin-insensitive dwarfism in hexaploid wheat (Triticum aestivum L.) were compared with tall controls in a series of yield trials in eastern England and central Germany. In all four varietal backgrounds the effects of Rht-B1b and Rht-D1b were similar (plant height ≈ 86 and 83% of tall controls respectively) and in combination reduced plant height to c. 58%. The Rht-B1c allele caused more severe dwarfism (c. 50%) and, when combined with Rht-D1b, reduced plant height still further to c. 41%.Data from the trials were consistent with a model for height/yield relationships in which the pleiotropic effects of the Rht alleles on yield can be inferred from their primary function: insensitivity to gibberellin limits stem extension growth, decreasing assimilate demand for this organ and diverting it to the developing ear (which is not itself dwarfed). The net balance between the resulting increase in harvest index and the curvilinear relationship observed between plant height and total shoot yield results in optimum grain yields at intermediate plant heights.Yield advantages of shorter plants over tall controls were evident over several trials with mean grain yields ranging from 200 to 760 g m−2. The optimum plant height for yield improvement in different genetic backgrounds was achieved by different Rht alleles according to the background varietal height, such that intrinsically taller genotypes required more potent Rht alleles to achieve maximum potential grain yield.Ear yield components showed increases in grain number due to Rht pleiotropy, from which it is inferred that the number of grains per ear is limited by supply of assimilates pre-anthesis. Increases in grain number were associated with decreases in mean weight per grain which varied according to severity of dwarfism and varietal background, so that the net effect on grain yield per ear was sometimes positive, sometimes negative, and sometimes neutral in different Rht/variety combinations.

REVIEW Towards an explanation of crop nitrogen demand based on the optimization of leaf nitrogen per unit leaf area

Abstract: An area of plant science that is still uncertain is precisely what determines plants' demand for nitrogen (N), that is the amount of N they need to take up from the soil to meet their requirements for potential growth and synthesis of new tissue. A robust and unequivocal physiological basis from which to determine N demand is lacking. Yet N dominates plant nutrition. No nutrient is needed in larger quantities and, in most environments, no nutrient is in such limiting supply. Knowledge of the factors governing N demand is essential to predict the needs of crops under a wide range of field situations, so that growers can be given more reliable fertilizer recommendations (Greenwood 1982; van Keulen et al . 1989). This is important, not just for economic reasons, but because of the risks to the environment that can arise from the over-application of N fertilizers, in particular the problem of nitrate leaching (Addiscott et al . 1991).

Effects of plant density on intercropped wheat and field beans in an organic farming system

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

Effect of condensed tannins in Lotus corniculatus on the nutritive value of pasture for sheep

Abstract: The extent to which condensed tannins (CT) in Lotus corniculatus were able to affect protein degradation and the nutritive value of pasture were evaluated at Palmerston North, New Zealand in 1992 in an indoor feeding trial with sheep and using in vitro incubations. The feeding trial involved three groups of seven young wether sheep held indoors in metabolism crates for the 32-day experimental period with one group fed freshly cut ryegrass/clover pasture (Pasture group) whilst the other two groups received a mixture of c. 37% freshly cut Lotus corniculatus and 63% pasture (dry matter (DM) basis). One of the latter groups was given twice daily oral drenches of polyethylene glycol (PEG) to bind with and remove the effects of the CT (PEG group) whilst the remaining sheep (Tannin group) were not drenched. Intakes of sheep given the mixed diets were constrained to that of the pasture group. The CT concentration in the lotus was 26.1 g/kg DM so that the mixed diets contained c. 10 g CT/kg DM. Effects of CT on digestion and sheep performance were minimal. Apparent digestibility of N was lower in the Tannin group (76.4 %) than PEG (79.8 %) or Pasture (79.4 %) sheep (P < 0.001), but there were no differences in DM digestibility (75 %) or wool growth from midside patches. Rumen ammonia and soluble protein concentrations appeared to be similar in PEG and Tannin sheep and volatile fatty acid (VFA) concentrations were similar in all groups (100 mmol/l). For incubations in vitro, several ratios of Lotus corniculatus: pasture were used to determine the effects of CT on precipitation of soluble proteins and the net yield of ammonia and gas with and without PEG. Homogenates of Lotus corniculatus leaves and pasture showed that 50 % of soluble protein was precipitated by 1.3 % CT in homogenate DM and there was a substantial decrease in in vitro degradation to ammonia when lotus leaf accounted for 33 % or more of DM with pasture. This work emphasises the need for caution when extrapolating from in vitro to the in vivo situation and suggests that 1 % CT from Lotus corniculatus may be insufficient to affect the nutritive value of fresh forages for sheep.

Effects of season, soil type and cropping on recoveries, residues and losses of 15N-labelled fertilizer applied to arable crops in spring

Abstract: 15 N-labelled fertilizer was applied in spring to winter wheat, winter oilseed rape, potatoes, sugarbeet and spring beans in field experiments done in 1987 and 1988 in SE England on four contrasting soil types – a silty clay loam, a chalky loam, a sandy loam and a heavy clay. The 15 N-labelled fertilizers were applied at recommended rates; for oilseed rape, a two-thirds rate was also tested. Whole-crop recoveries of labelled nitrogen averaged 52% for winter wheat, 45% for oilseed rape, 61% for potatoes and 61% for sugarbeet. Spring beans, which received only 2·5 kg ha −1 of labelled N, recovered 26%. Removals of 15 N-labelled fertilizer N in the harvested products were rather less, averaging 32, 25, 49, 27 and 13% in wheat grain, rape seed, potato tubers, beet root and bean grain, respectively. Crop residues were either baled and removed, as with wheat and rape straw, or were flailed or ‘topped’ and left on the soil surface, as was the case with potato tops and sugarbeet tops. Wheat stubble and rape stubble, together with leaf litter and weeds, were incorporated after harvest. The ploughing in of crop residues returned 4–35% of the original nitrogen fertilizer application to the soil, in addition to that which already remained at harvest, which averaged 24, 29 and 25% of that applied to winter wheat, oilseed rape and sugarbeet respectively. Less remained at harvest after potatoes ( c . 21%) and more after spring beans ( c . 49%). Most of the labelled residue remained in the top-soil (0–23cm) layer. 15 N-labelled fertilizer unaccounted for in crop and soil (0–100 cm) at harvest of winter wheat, oilseed rape, potatoes, sugarbeet and spring beans averaged 23, 25, 19, 14 and 26% of that applied, respectively. Gaseous losses of fertilizer N by denitrification were probably greater following applications to winter wheat and oilseed rape, where the N was applied earlier (and the soils were wetter) than with potatoes and sugarbeet. Consequently, it may well be advantageous to delay the application of fertilizer N to winter wheat and oilseed rape if the soil is wet. Total inorganic N (labelled and unlabelled) in soils (0–100 cm) following harvest of potatoes given 15 N-labelled fertilizer in spring averaged 70 kg N ha −1 and was often greater than after the corresponding crops of winter wheat and oilseed rape, which averaged 53 kg N ha −1 and 49 kg N ha −1 , respectively. On average, 91 kg ha −1 of inorganic N was found in soil (0–100 cm) following spring beans. Least inorganic N remained in the soil following sugarbeet, averaging only 19 kg N ha −1 . The risk of nitrate leaching in the following winter, based on that which remained in the soil at harvest, ranked in decreasing order, was: spring beans=potatoes>oilseed rape=winter wheat>sugarbeet. On average, only 2·9% of the labelled fertilizer applied to winter wheat and oilseed rape remained in the soil (0–100 cm) as inorganic N (NO − 3 +NH + 4 ) at harvest; with sugarbeet only 1·1% remained. In most cases c . 10% of the mineral N present in the soil at this time was derived from the nitrogen fertilizer applied to arable crops in spring. However, substantially more ( c . 21%) was derived from fertilizer following harvest of winter wheat infected with take-all ( Gaeumannomyces graminis var. tritici ) and after potatoes. With winter wheat and sugarbeet, withholding fertilizer N had little effect on the total quantity of inorganic N present in the soil profile at harvest, but with oilseed rape and potatoes there was a decrease of, on average, 38 and 50%, respectively. A decrease in the amount of nitrogen applied to winter wheat and sugarbeet in spring would therefore not significantly decrease the quantity of nitrate at risk to leaching during the following autumn and winter, but may be more effective with rape and potatoes. However, if wheat growth is severely impaired by take-all, significant amounts of fertilizer-derived nitrate will remain in the soil at harvest, at risk to leaching.

Modelling phasic development in wheat: a conceptual integration of physiological components.

Abstract: Simulation of phasic development in wheat is necessary in constructing wheat growth and yield models. It is also useful for evaluating cultivar adaptation and scheduling cultural practices. This paper describes a conceptual model of wheat development based on phenological principles, as affected by vernalization, photoperiod, thermal response and intrinsic earliness, and also reports the results of sensitivity analysis and validation of the model. The model predicts when the plant will reach double ridge, terminal spikelet and heading. In the model, the daily thermal sensitivity of development following emergence is determined by an interaction of relative vernalization completion' and 'relative photoperiod effectiveness' for that day. After complete vernalization is reached, the daily thermal sensitivity is determined only by relative photoperiod effectiveness, which gradually increases from terminal spikelet to heading. A multiplication between the daily thermal sensitivity and thermal effectiveness generated daily flowering time, which was accumulated to trigger a particular developmental stage. Genotypic differences were characterized as vernalization requirement, photoperiod sensitivity and intrinsic earliness. The model showed a sensitive response to environmental variables of temperature and daylength, and to genetic parameters of vernalization requirement and photoperiod sensitivity. Evaluation of the model using multiple experimental data involving various cultivars and planting dates exhibited a marked goodness of fit between simulation and observation with a root mean square error < 5 days. The results indicate that the model can be used as a predictor for the major flowering stages, as well as functioning as a knowledge base for understanding the characteristics of different development components in wheat.

Effects of 28-homobrassinolide on yields of wheat, rice, groundnut, mustard, potato and cotton

Abstract: Yield responses of some economically important crop plants due to foliar applications of low concentrations of 28-homobrassinolide (HBR) were studied in experiments conducted at research stations and in farmers' fields in India during 1989–95. Foliar sprays of different concentrations of HBR were applied at tillering and spike/panicle initiation in wheat (0·5 and 1·0 mg/l) and rice (0·25, 0·50 and 1·00 mg/l); at flowering and pegging in groundnut (0·25 and 0·50 mg/l); 30 and 45 days after sowing (DAS) in mustard (0·25 and 0·50 mg/l); 25 and 35 days after emergence in potato (0·25 and 0·50 mg/l); and 30, 50, 70 DAS in cotton (0·1 and 1·0 mg/l). The HBR treatments significantly (P<0·05 and P<0·01) increased grain yields in wheat, rice and mustard, pod yields in groundnut, tuber yields in potato and seed cotton yields, over control. The extent of yield improvement due to HBR was influenced by crop species, concentration of HBR, plant growth stage at application and frequency of application.

Effects of salinity on growth, shoot water relations and root hydraulic conductivity in tomato plants

Abstract: Growth, shoot water relations and root hydraulic conductivity were studied in tomato plants (Lycopersicon esculentum cv. INCA9) subjected to different salt concentrations in the root medium. Two experiments were carried out at Instituto Nacional de Ciencias Agricolas (INCA), Cuba, during May and June 1995. In the first experiment, plants were grown for 13 days in a nutrient solution with 0 or 100 mM NaCl. In the second experiment, the hydraulic conductivity was measured on roots submerged in nine different concentrations of NaCl up to 200 mM. The effect of temperature treatments between 0 and 50 °C on root hydraulic conductivity was also examined. Shoot growth, leaf water potential, leaf stomatal conductance, leaf relative water content and root hydraulic conductivity values decreased more rapidly in the treated plants than in control plants. A strong correlation was found between the root hydraulic conductivity and leaf water parameters, indicating that water flow through the roots was the main factor controlling shoot water relations.

Grain weight in wheat cultivars released from 1920 to 1990 as affected by post-anthesis defoliation

Abstract: Although it has been generally recognized that the difference in yield potential amongst wheat cultivars released in different eras is related to differences in their reproductive sink strength, there have been few investigations about changes in source-sink ratios as a consequence of wheat breeding. In the present study, two field experiments, in which plots were fertilized and irrigated and lodging and diseases were prevented, were carried out with seven cultivars (including a commercial hybrid) representing different periods of plant breeding in Argentina from 1920 to 1990. The cultivars were defoliated during post-anthesis to analyse the response of grain weight at particular positions within the spike (which have intrinsic differences in potential size). Individual grain weight was virtually unaffected by defoliation in the old cultivars, but modern cultivars exhibited a significant reduction in individual grain weight for several positions within the spike, although this reduction was small (c. 15 %) and many grains were unaffected. In addition, no relationship was found between individual grain weight in the controls and its reduction due to defoliation. We concluded that if the source-sink ratio is further reduced, the grain yield of modern wheats will be simultaneously limited by the source and the sink. Future breeding should therefore attempt to improve simultaneously both sink and source strengths.

Extent of digestion and rumen condition as factors affecting passage of liquid and digesta particles in sheep

Abstract: Two experiments were carried out at Mt. Cotton, The University of Queensland, from November 1992 to July 1993, to study the effect of extent of digestion or feed type (grass or legume) on particle kinetics in the rumen. Small (0.5-1.18 mm) Yb-labelled grass or legume particles, either digested or undigested, were injected into the rumen of sheep fed on different diets, and their retention time in the reticulo-ruminal compartment measured. In Expt 1, four intact wethers were fed on either pangola grass hay, chaffed lucerne hay, pelleted lucerne hay or commercial pelleted concentrate. Digested particles from the faeces of animals fed on pangola or lucerne and undigested material from the same diets were wet-sieved and the fraction 0.5-1.18 mm collected, labelled with Yb-acetate and injected into the animals together with a solution of Cr-EDTA. Faecal samples were taken and analysed for marker concentrations. In Expt 2, four similar animals, fitted with duodenal and ruminal cannulae, were fed on different proportions of pangola grass hay and lucerne hay, and Cr-EDTA and the above mentioned labelled particles were injected through the rumen cannula. Samples were taken from the duodenum and analysed for marker concentrations. The results indicated that diet characteristics rather than extent of digestion or particle type had the greatest influence on rates of passage of both liquid and particulate phases. Different proportions of pangola and lucerne did not result in marked differences in either the volumes of rumen contents or the rates of passage of the solid phase marker but altered the rates of passage of Cr-EDTA. Increasing the proportion of legume increased intake and decreased retention time markedly, with no additive effects on digestibility. Particles of the same small size escaped with the same fractional passage rate within each diet, irrespective of type (grass or legume) or status (undigested or digested), indicating identical kinetics within each rumen type. It was concluded that rumen conditions as influenced by diet type have most influence on water and particle kinetics and that extent of digestion of the small particles used in our experiments was not important. Particles of legume or grass of the same size behaved similarly within a diet type.

Observations on two commercial flower mixtures as food sources for beneficial insects in the UK

Abstract: Observations were made in 1994 and 1995 in Hertfordshire of the flowering phenology and attractiveness to beneficial insects of two commercial mixtures of flowering plants intended for set-aside land These were the Tubingen Mixture from Germany and Ascot Linde SN from the Netherlands The mixtures were visited by 14 species of Hymenoptera, 14 species of syrphid Diptera and six species of Lepidoptera Although the mixtures contained 12 and five plant species respectively, Phacelia tanacetifolia was the dominant species to establish, flower and attract insects in both mixtures The other plants contributed little to flower density or insect diversity These mixtures are therefore not suitable for UK needs using the present proportions of plant species

Application of the CERES--wheat model to yield predictions in the irrigated plains of the Indian Punjab.

Abstract: The crop environment resource synthesis model for wheat, CERES-Wheat, was used to simulate yields from 1985 to 1993 at Ludhiana, India. The simulated anthesis and physiological maturity dates, grain and total biomass yields of wheat were compared with actual observations for the commonly grown cultivar, HD-2329. The simulated and actual dates of phenological events showed deviations from only -9 to + 6 days for anthesis and -6 to + 3 days for physiological maturity of the crop. The model estimated the kernel weight within 88-113 % (mean 100 %) of the actual kernel weights. The model predicted the grain yields from 80 to 115 % (mean 97.5 %) of the observed grain yield. Biomass yields were predicted from 93 to 128 % (mean 110.5 %) of the observed yields. The results obtained with the model for the eight crop seasons demonstrated satisfactory predictions of phenology, growth and yield of wheat. However, the biomass simulations indicated the need for further examination of the factors controlling the partitioning of photosynthates during crop growth. The results of this study reveal that the calibrated CERES-Wheat model can be used for the prediction of wheat growth and yield in the central irrigated plains of the Indian Punjab.

Rumen gases and bloat in grazing dairy cows

Abstract: Results are reported from three experiments conducted at the Dairy Research Institute, Ellinbank, Australia during 1992/93 which examined the composition and kinetics of the gas in the rumen headspace of lactating dairy cows grazing white clover/perennial ryegrass pastures. Before grazing, rumen headspace gas was composed of carbon dioxide 65%, methane 31% and nitrogen 4% whereas, after one hour of active grazing, the headspace gas was composed of carbon dioxide 76%, methane 22% and nitrogen 2%. The composition of headspace gas was not affected by antibloat capsules (which release 250 mg/day of monensin). The headspace gas from bloated cows contained slightly less (P<0·01) carbon dioxide and slightly more nitrogen than that from non-bloated cows.A novel technique which employs ethane as a tracer to measure rumen headspace volume and the kinetics of the rumen headspace gases is described. The tracer technique was used in two experiments in which the influence of grazing, antibloat capsules and bloat on the rumen headspace volume and the kinetics of the headspace gases were examined. It is concluded that our ethane tracer technique provides a simple and inexpensive way to estimate methane production by grazing ruminants.

A comparison of animal output and nitrogen leaching losses recorded from drained fertilized grass and grass/clover pasture

Abstract: Annual liveweight gain of beef cattle (steers) grazing grass pasture fertilized with 200 kg N/ha was compared over a period of 7 years (1989-95) with that of steers grazing grass/white clover pasture given no artificial N fertilizer at North Wyke, Devon, UK. Nitrogen lost by leaching over the ensuing winter drainage periods was monitored from both pastures. Nitrogen leaching loss from the fertilized pasture over an extended period of 13 years (1983-95) is also reported. The average annual liveweight gain of the steers grazing the grass/clover pasture (0.81 t/ha) was 19% lower than that of the steers grazing the N-fertilized grass pasture (1.00 t/ha). The average annual loss of nitrate-N by leaching in winter drainage from the grass/clover pasture (13 kg/ha) was only 26% of that recorded from the fertilized grass (50 kg/ha). A possible reason for this difference may arise from the previous history of the grass/clover pasture which had been ploughed in 1982, causing a flush of N mineralization and consequently greater immobilization of N in the soil in subsequent years. Losses of N each winter by leaching measured over a 13-year period from the fertilized grass were highly correlated (P < 0.001) with the preceding summer's soil moisture deficit, with the highest losses following dry summers. The nitrate-N concentration in the drainage water exceeded the European Union limit in drinking water (11.3 mg/l) in the initial 25 mm of drainage during 11 of the 13 autumns. The average loss of N each winter (53 kg/ha) was equivalent to 26% of the fertilizer-N applied annually. Immediate losses of N by leaching of fertilizer applied in early spring and throughout one very wet summer (1993) were minimal.

Effect of slurry application and mineral nitrogen fertilization on N leaching in different crop combinations

Abstract: Nitrogen (N) fertilizer not used by the crop can increase the risk of nitrate leaching into the groundwater. In two growing seasons, 1990/91 and 1991/92, the relationships between N fertilization and yield, N uptake by the grain and the N leaching in the subsequent percolation period were investigated in a multifactorial field experiment at Hohenschulen Experimental Station near Kiel in NW Germany. The crop rotation was oilseed rape – winter wheat – winter barley, and effects of soil tillage (minimum tillage without ploughing, conventional tillage), application of pig slurry (none, application in autumn, application in autumn and in spring), mineral N fertilization (none, 80 or 200 kg N ha −1 to oilseed rape and 120 or 240 kg N ha −1 to cereals) and application of fungicides (none, intensive) were all tested. In each year, the rotation and the treatments were located on the same plots. Mineral N fertilization and fungicide application increased yield and N uptake by grain or seed in all crops. In contrast, the application of slurry, especially in autumn, had only small effects on yield and N uptake. Nitrogen losses by leaching (measured using porous ceramic cups) were affected mainly by the year and the crop. In 1992/93, averaged over all factors, 80 kg N ha −1 was leached compared with 28 kg N ha −1 the previous year. Oilseed rape reduced N losses, whereas under winter wheat up to 160 kg N ha −1 was leached. Due to a lower N-use efficiency, autumn applications of slurry increased N leaching, and mineral N fertilization of the preceding crop also led to higher N losses. Since the amount of leached N depends both on the nitrogen left by the preceding crop (unused fertilizer N as well as N in residues) and on N uptake by the subsequent crop, it is not possible to apportion the N losses to any particular crop in the rotation. The cropping sequence, together with its previous and subsequent crops, must also be considered. To minimize leaching, N fertilization must meet the needs of the growing crop. In order to improve the efficiency further, investigations must be conducted in order to understand the dynamics of N in the plant–soil system in conjunction with the weather and crop management practices.

Heterosis, overdominance for grain yield, and alpha-amylase activity in F1 hybrids between near-isogenic Rht dwarf and tall wheats

Abstract: The Rht-B1b, Rht-D1b and Rht-B1c alleles for reduced height in wheat (the Norin 10 and Tom Thumb dwarfing genes previously known as Rht1, Rht2 and Rht3) were exploited in combinations to generate a near-continuous range of plant heights, from 53 cm to 123 cm, amongst near-isogenic homozygotes and F1 hybrids. Pleiotropic yield effects of Rht genes were measured in both homozygous (intravarietal) and heterozygous (intervarietal) genetic backgrounds. Heterosis due to overdominance of Rht genes was detected among intravarietal hybrids. The effects of heterozygosity at other genetic loci (mean dominance) were determined, independently of Rht effects, from comparisons between intravarietal and intervarietal F1 hybrids.Genotypes of intermediate plant heights gave maximum yields, in agreement with other trials of the homozygous lines, so that heterosis (hybrid exceeding best parent) for Rht yield effects was observed in crosses between tall and dwarf isogenic pairs. This heterosis combined additively with increased mean weight per grain in intervarietal crosses, generating the highest overall grain yields in hybrids with semi-dwarf stature in heterozygous genetic backgrounds. The Rht-B1c allele showed single-gene overdominance for grain yield, also the production of alpha-amylase in ripening grains of Maris Huntsman was effectively inhibited in the Rht-B1a/c intravarietal hybrid. The Rht-B1c allele thus offers advantages for both grain yield and grain quality in the heterozygous condition and should be considered as an alternative to the conventional semi-dwarfing genes Rht-B1b and Rht-D1b for F1 varieties in environments conductive to preharvest sprouting.

Effect of a bacterial inoculant on rate of fermentation and chemical composition of high dry matter grass silages

Abstract: Four experiments were carried out in Lelystad, The Netherlands in 1994, in which perennial ryegrass wilted to 421–568 g dry matter (DM) kg−1 was ensiled with and without an inoculant containing Lactobacillus plantarum and Enterococcus faecium strains in 1-litre capacity laboratory silos. Treated silages showed a markedly increased rate of pH decline. The final pH of treated silages was reached 20–30 days after ensiling, whereas acidification of control silages continued during the full 180-day ensilage period. After 180 days ensilage, treated silages showed significantly (P<0·001) lower pH, DM loss and ammonia-N concentrations and significantly (P<0·001) higher lactic acid concentrations than control silages in all experiments. Concentrations of ethanol and acetic acid were significantly (at least P<0·05) lower for the treated silages, except for acetic acid in one experiment and ethanol in another. Butyric acid was not found in any of the silages. One of the control silages (ensiled at 517 g DM kg−1) contained ethanol as the major fermentation product indicating that alcoholic fermentation had taken place, probably by yeasts. Treated and untreated grasses used in the first experiment (432 and 442 g DM kg−1, respectively) were also used to produce silages in two 40-t capacity clamp silos. Similar to the laboratory silos, the treated silage had a higher lactic acid concentration and lower pH and ethanol, acetic acid and ammonia-N concentrations than the untreated silage.

Effect of fertilizer rate and form on the recovery of 15N-labelled fertilizer applied to wheat in Syria

Abstract: 15N-labelled fertilizer was applied at different rates (0, 30, 60, 90 kg N ha−1) and in different forms (urea or ammonium sulphate) to wheat grown in Syria in three seasons (1991/92, 1992/93 and 1994/95).Recovery of 15N-labelled fertilizer in the above-ground crop at harvest was low (8–22%), with the amount of 15N-labelled fertilizer recovered in the crop increasing as the rate of application increased. Fertilizer application caused a significant increase in the amount of unlabelled soil N in the crop, suggesting that the application of N fertilizer caused a ‘real’ added nitrogen interaction. Recovery of 15N-labelled fertilizer in the crop was unaffected by the form of the fertilizer.On average 31% (14–54%) of the 15N-labelled fertilizer remained in the soil at harvest, mostly in the 0–20 cm layer. At the lowest application rate (30 kg N ha−1) most of the residual fertilizer was as organic N, but at the higher application rates (60 and 90 kg N ha−1), a greater proportion of the 15N-labelled fertilizer was recovered as inorganic N, presumably as the result of top-dressing N in dry conditions in the spring. The amount of 15N-labelled fertilizer remaining in the soil increased as the fertilizer rate increased, but was unaffected by the form of fertilizer applied.Losses of 15N-labelled fertilizer were large (>35%), probably caused by gaseous losses, either through volatilization of N from the calcareous soil, or through denitrification from wet soils rich in organic residues.N fertilization strategies in the West Asia/North Africa (WANA) region should take note of the low recovery of N fertilizer by the crop in the season of application, and the resultant large quantities of residual fertilizer.

A comparison of fresh and dried Calliandra calothyrsus supplements for sheep given a basal diet of barley straw

Abstract: Leaves from the tropical tree legume calliandra (Calliandra calothyrsus) were harvested and fed either fresh frozen (F) or dried (D) as a supplement (200 g dry matter (DM)) to sheep (n = 4) given barley straw ad libitum in metabolism cages in a controlled-environment animal house. Sheep given these diets were intra-ruminally infused (0.5 litres/day) with either water or a solution containing 100 g/l polyethylene glycol (PEG). These treatments were administered in a randomized complete block design, and the results statistically analysed. Drying significantly increased the cell wall (cellulose, hemicellulose) and lignin contents, but decreased the condensed tannin (butanol-HCl method) content (F = 35.7, D = 21.7 g/kg DM). Both drying and PEG infusion significantly (P < 0.05) increased straw organic matter (OM) intake, but the effects of drying plus PEG were not additive. Organic matter digestibility of the diets was significantly (P < 0.05) increased by drying (F = 433 g/kg, D = 486 g/kg), but not by the infusion of PEG. Total nitrogen (N) digestibility was significantly (P < 0.05) increased by drying (F = 207 g/kg, D = 316 g/kg) in the absence of PEG, and by PEG for both frozen (-PEG = 207 g/kg, +PEG = 392 g/kg) and dried (-PEG = 316 g/kg, +PEG = 434 g/kg) calliandra. PEG infusion significantly increased the proportion of feed N degraded in the rumen (-PEG = 0.41, +PEG = 0.52) and rumen ammonia concentrations (-PEG = 63, +PEG = 103 mgN/l), but had no significant effect on the rate or efficiency of microbial protein synthesis in the rumen. PEG infusions significantly increased the amount and proportion of N intake absorbed from the lower digestive tract, but had no significant effect on overall N balance. Drying decreased the tannin losses (as % intake) occurring in the rumen (F = 37.3%, D = 24.2%), and PEG infusion increased these losses for both frozen (-PEG = 37.3%, +PEG = 72.5%) and dried (-PEG = 24.2%, +PEG = 68.7%) calliandra supplements. It was concluded from these studies that the presence of tannins in fresh (frozen) calliandra depressed feed utilization, and that drying was an effective means of improving the nutritive value of calliandra when fed as a supplement to low quality straws.

The energy expenditure of cattle and buffaloes walking and working in different soil conditions.

Abstract: SUMMARY At the Centre for Tropical Veterinary Medicine, Scotland, during the summer months of 1987, two adult water buffaloes, two Brahman cattle and two Brahman x Friesian steers walked round a circular track on concrete or through 300 mm deep mud. Average walking speed (m/s) when unloaded. or average walking speed (m/s) when pulling 324 N, energy for walking (J /m/kg) and net mechanical efficiency (%) were 1.05 and 0.81 (P < 0.01), 1.03 and 0.80 (P < 0.001), 1.49 and 3.34 (P < 0.001) and 31.0 and 31.8 for concrete and mud respectively. Energy values were calculated from gaseous exchange measured with an open circuit system. In Central Nigeria, from September 1991 to May 1992, the energy expenditure of eight Bunaji (White Fulani) bulls was monitored using portable oxygen measuring equipment (modified' Oxylog ') when walking. ploughing and harrowing on six soil surfaces ranging from hard, smooth earth to ploughed. \vaterlogged clay. Average walking speeds (m/s), pulling speeds (m/s) and energy cost of walking (J/m/kg) varied from 0,97 to 0.65, 0.55 to 0,47 and 1.47 to 8,58 respectively. Net mechanical efficiency averaged 31.4 % and was unaffected by ground surface. The energy cost of walking for the Bos indicus cattle on smooth ground (1.47 J /m/kg) in this trial was less than that previously reported for Bos (aurus (1.80 J /m/kg) and the reported average value for cattle (80S indicus and Bos (aurus) on treadmills (2,09 J/m/kg). The implications for practical agriculture of the higher levels of energy expenditure for walking in muddy conditions are discussed.

Broad bean and lentil seed treatments with imidazolinones for the control of broomrape (Orobanche crenata)

Abstract: Studies were conducted from 1993 to 1995 in Southern Spain to determine the feasibility of controlling broomrape (Orobanche crenata Forsk.) in broad bean (Vicia faba L.) and lentil (Lens culinaris L.) by treating seeds with imazethapyr and imazapyr. In the broad bean, soaking for 5 min in 0·01–0·1% herbicide solutions or coating at 20–40 g ha−1 (seed sowing rate 160 kg ha−1) with imazethapyr (Pursuit-10) did not affect seed germination and crop growth, and resulted in 60–80% broomrape control. Furthermore, broad bean seeds treated with imazethapyr followed by an additional late post-emergence application of imazapyr (Arsenal-25) at 5 g ha−1 resulted in excellent broomrape control (>95%). Similarly, lentil seed treatments with imazapyr by coating seeds at rates equivalent to 5–10 g ha−1 or by soaking for 5 min in 0·25% solutions did not affect germination or crop growth, and controlled 85–95% of broomrape. As a result, with broomrape-efficient herbicide treatments, crop biomass/seed yield increased as compared to broomrape-infested, non-treated controls. Herbicide seed treatments with imazapyr in broad bean and with imazethapyr in lentil were less well tolerated and were less effective in controlling broomrape than treatments with imazethapyr and imazapyr, respectively.

Rumen digestion and rumen outflow rate in deer fed fresh chicory ( Cichorium intybus ) or perennial ryegrass ( Lolium perenne )

Abstract: Pure swards of chicory (Cichorium intybus) and perennial ryegrass (Lolium perenne) were grown at Palmerston North, New Zealand. They were cut daily and fed hourly at 2.25 kg dry matter (DM)/day to eight hand-reared, rumen-fistulated castrated red deer stags kept in metabolism crates during December 1994 and January 1995 (summer). Apparent digestibility, rumen fractional disappearance rate (FDPR), rumen fractional degradation rate (FDR), rumen fractional outflow rate (FOR) and mean retention time (MRT) were measured. The ratio of readily fermentable carbohydrate to structural carbohydrate was approximately three times higher in chicory than in perennial ryegrass. Apparent digestibility of DM was higher in deer fed chicory than in deer fed perennial ryegrass (0.785 v. 0.727), whilst apparent digestibility of neutral detergent fibre (NDF) was lower in deer fed chicory (0.679 v. 0.755), due to a reduced hemicellulose digestibility (0.667 v. 0.783). Relative to deer fed perennial ryegrass, those fed chicory had higher rumen FDPR values for DM (14.5 v. 8.6%/h), soluble carbohydrate (69.9 v. 54.7 %/h), cellulose (15.5 v. 9.8 % /h) and lignin (6.8 v. 3.8%/h). Rumen FDR in deer fed chicory was higher than those fed perennial ryegrass for cellulose (11.4 v. 7.0%/h) and lignin (2.7 v. 1.0%/h), but tended to be lower for hemicellulose. Rumen FOR was higher and MRT was lower for both liquid and particulate matter in deer fed chicory compared to deer fed perennial ryegrass. It is concluded that rumen FDPR and apparent digestibility were much higher in deer fed chicory than in deer fed perennial ryegrass, due to faster degradation rates of most constituents in the rumen and faster outflow rates from the rumen. An exception was hemicellulose, where reduced rumen degradation rates and shorter rumen particulate MRT contributed to reduced apparent digestibility. Faster clearance from the rumen, due to both faster degradation and outflow rates may be used to explain the greater voluntary feed intake (VFI), as well as faster growth rate in deer grazing chicory compared to those grazing perennial ryegrass. Faster rates of lignin solubility in the rumen probably contributed to the more rapid breakdown of chicory in the rumen.

Morphology of tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) plants in pastures under sheep and cattle grazing

Abstract: The effects of contrasting management systems either of infrequent rotational grazing by town milk supply dairy cattle, or of frequent defoliation by continuously grazing sheep and beef cattle, on the morphology of independent plants and populations of 'Grasslands Roa' tall fescue in mixed pastures, were measured over 1 year (1992/93) in New Zealand. Volunteer perennial ryegrass plants were also measured for comparison. While both species exhibited a similar pattern of clonal growth, tall fescue developed more plants of higher branching complexity than perennial ryegrass, chiefly through maintaining more connective stems, as herbage production was confined to the three youngest branching orders in both species. Greater resistance to microbial degradation of old stems through poorer quality organic matter (wide C: N ratio) compared to perennial ryegrass may be responsible for the greater complexity of fescue plants. In addition, tillering rates in tall fescue were three times lower which was offset by greater longevity and size of leaves and tillers, compared to perennial ryegrass. As a result, seasonal fluctuation in the distribution of plants among the various branching orders in tall fescue was small, producing a more stable population relative to the distinct seasonal changes in the population of perennial ryegrass plants. Grazing management had no effect on the seasonal population structure in either species. Differences in plant structure due to grazing management were small, with only slightly more tillers on sheep-grazed than on cattle-grazed tall fescue plants. The major effect of grazing management was on dry weight or size of plant components. Cattle-grazed tall fescue plants were 120 % heavier, with greater numbers and lengths of stolons and flower heads than those under sheep grazing. For the volunteer perennial ryegrass, the difference was only 65 %, possibly due to competition from the more vigorous tall fescue under rotational cattle grazing. Both species produced stolons throughout the year, although these were primarily associated with reproductive growth in spring. In tall fescue, an additional distinction was made between stolon and rhizome, the latter occurring mainly in the summer-autumn. Their possible functions in plant growth are discussed.

Quantitative evaluation of Linum usitatissimum varieties for dual-purpose traits

Abstract: New uses of natural fibres in industrial processes have increased the demand for linseed fibre which is normally discarded. In this investigation, 18 linseed and 10 flax varieties are evaluated for 13 developmental, seed yield and fibre yield traits with a view to identifying suitable genotypes which may have high yields of both seed and fibre, and therefore can be used as dual-purpose varieties and/or are likely to provide a suitable foundation for breeding new cultivars with an ability to produce high yields for seed as well as fibre. Comparison of linseed and flax varieties has revealed that the two plant types have diversified to a great extent, particularly for those traits which have been subjected to direct or indirect selection during the past decades. However, considerable variation still exists among the linseed and flax varieties, and linseed shows more heritable variation than flax, for both seed and fibre traits. On the other hand, persistent selection of linseed and flax for commercially desirable phenotypes has not modified the genetic correlations to any appreciable level and both crops display almost identical correlations which do not differ significantly for any pair of traits. None of the flax or linseed varieties has shown such outstanding performance for seed yield as well as fibre weight which would have allowed them to be considered suitable for cultivation as a dual-purpose variety. In general, linseed x linseed and linseed x flax crosses would constitute better source materials for breeding high yielding dual-purpose cultivars compared to flax x flax crosses, particularly when seed will be the primary commercial product and fibre/straw a secondary commodity of such varieties.

Changes in the weight and quality of sugarbeet (Beta vulgaris ) roots in storage clamps on farms

Abstract: The changes in weight and quality of sugarbeet roots stored in 18 clamps, mostly in eastern England during the winters of 1992/93 to 1994/95, were studied on farms using best commercial practice. Storage usually started in early December, at about the last recommended date of harvesting, and continued until the end of the beet-processing campaign at the local sugar factory (usually in February). Random samples of beet, in open-weave nets, were either analysed at the outset or were buried in a predetermined pattern in the clamp for up to 84 days. Periodically, samples were removed from the clamps for analysis. Beet weight hardly changed but sugar was lost as a reduction in sugar concentration: this declined at c. 0.02 % per day. The concentration of reducing sugars, which are important impurities, increased fourfold during storage. Most other beet quality parameters remained unchanged. Sugar and adjusted weight was lost at 0.143 and 0.187% per day respectively. This relationship was highly significant, but a relationship between sugar loss and accumulated thermal time (0.0188 % per °C day) accounted for more of the variation (73 %). Temperature changes within the clamps, and the differences between clamps in accumulated thermal time, were not predictable. Some clamp insulation materials appear to allow more heat to accumulate than is desirable.

Soil carbon, nitrogen and phosphorus contents in maize plots after 14 years of pig slurry applications

Abstract: Excessive applications of liquid pig manure (LPM) could result in nutrient accumulation in the soil, thereby increasing the potential for plant nutrient losses through movement in groundwater. The objective of this work was to measure the concentrations of total carbon (C,), total nitrogen (N 1 ), total phosphorus (P t ) and Mehlich-3 extractable-P (P M3 ) with depth in a Le Bras silty loam soil growing maize (Zea maize L.) under reduced tillage conditions. The soil was fertilized annually with various rates of LPM (0, 30, 60, 90 and 120 m 3 /ha) in four completely randomized blocks since 1979. In autumn 1992, twenty soil plots were sampled in increments of 20 cm to a depth of 1.0 m and analysed for total C, total N, total P and Mehlich-3 extractable-P. LPM application rate (R), soil depth (D) and the interaction R x D had highly significant (P < 0.001) linear effects on C t , N t , P t and P M3 concentrations throughout the 100-cm depth profiles. At all depths, C t , N t , P i and P M3 contents increased with increasing rates of LPM application. The zone of maximum accumulation of C i , N t , P t and P M3 concentrations occurred at the first 0-40 cm depth. A significant relationship was found between soil organic matter and N t , P t and P M3 . Differences in N and P concentrations between manure rates are due to manure and maize. The increase in P M3 was generally greater for soil samples with high P t content. Results from this study indicate that long-term application of a high rate of LPM leads to greater total C, N and P concentrations in the soil profile.

Phosphorus homoeostasis in grazing breeder cattle

Abstract: The phosphorus (P) balances and P kinetics of 15 Droughtmaster heifers were studied in mid and late pregnancy and early and late lactation to compare their P absorption coefficients and their P endogenous faecal losses with those of growing cattle. The heifers continuously grazed three paddocks of tropical pasture for a year to provide a range of P intakes. The daily dry matter (DM) and P intakes of the heifers were generally much higher during lactation (17-26 g DM/kg LW and 11-40 mg P/kg LW) than during pregnancy (10-16 g DM/kg LW and 6-22 mg P/kg LW), due in part to the heifers calving at the beginning of the wet (pasture growing) season. Plasma inorganic P levels decreased as the experiment progressed and were very low (< 30 mg/1) in all treatments in late lactation. Milk and milk P secretion were high in early lactation (4.0-5.5 l/day and 12-16 mg P/kg LW per day) so the heifers were in more negative balance during lactation than during pregnancy. The coefficient of P absorption was similar to that previously observed in growing cattle consuming forage diets and it was concluded that 0.75 was the appropriate value to use in the estimation of requirements. Endogenous faecal losses ranged from 7 to 17 mg/kg LW and were related to P intake or DM intake plus plasma inorganic P. Comparison of the regressions with those from the larger data set for growing cattle showed that the endogenous faecal losses were similar and there were no special faecal endogenous losses in breeding cattle.

Effect of in vitro manipulation of pH on magnesium solubility in ruminal and caecal digesta in sheep

Abstract: Rumen and caecal digesta were collected, under anaesthetic, from eight sheep offered either hay, pelleted concentrate or pasture at the Johnston Memorial Laboratory, Lincoln University during 1991. Subsamples of digesta were incubated at 39 °C for 1 h after adjustment of pH within the range 0.5-12 by the addition of H 2 SO 4 or NaOH. The samples were centrifuged at 30000 g for 30 min and magnesium (Mg) concentration measured in the 30000 g supernatant fraction and in total digesta to assess Mg solubility. In rumen digesta, Mg solubility declined from 0.86 at pH 5 to 0.30 at pH 7 and differences in response between diets were small. Magnesium solubility in caecal digesta was generally higher than in ruminal digesta, and particularly at pH values > 6. At pH 7 the difference was twofold. Moreover, differences were observed between diets in the rate of decline in solubility in caecal digesta with increasing pH. At pH 5, 0.90 of Mg from hay and concentrate diets was soluble compared with only 0.8 for pasture. At pH 7, Mg solubility in caecal digesta from hay and concentrate-fed animals was almost double that from pasture-fed animals (0.64 and 0.62 ν. 0.36, respectively). The implications of the findings for Mg homoeostasis in ruminants are discussed.