Twenty slurries, 20 farmyard manures (FYM) and 10 poultry manures were chemically analysed to characterize their nitrogen (N) fractions and to assess their potential organic N supply. The organic N fraction varied between I manure types and represented from 14% to 99% of the total N content. The readily mineralizable N fraction, measured by refluxing with KCl, was largest in the pig FYMs and broiler litters, but on average only represented 7-8% of the total N content. A pot experiment was undertaken to measure N mineralization from the organic N fraction of 17 of these manures. The ammonium-N content of the manures was removed and the remaining organic N mixed with a low mineral N status sandy soil, which was sown with perennial ryegrass (Lolium perenne L.). N offtake was used as a measure of mineralization throughout the 199 day experiment. The greatest N mineralization was measured from a layer manure and a Dig slurry, where N offtake represented 56% and 37% of the organic N added, respectively. Lowest (%) N mineralization was measured from a dairy cow slurry (< 2%) and a beef FYM (6%). The mineralization rate was negatively related to the C:organic N ratio of the ammonium-N stripped manures (P < 0.01, r = -0.63).
Of the anthropogenic greenhouse gas emission in Denmark animal manure contributes an estimated 40 % of methane (CH4) and 20% of nitrous oxide (N2O). Livestock production systems undergo changes for the purpose of increasing animal welfare, and such changes often include increasing the amounts of bedding manure. Emission of greenhouse gases from composting pig deep litter was studied during a ii-month period. Effects of increasing the amount of straw used in deep litter (reducing litter density) were included in the study. Methane was produced at a high rate in the centre of the heap at high density during the thermophilic phase of composting, and CH4 emission was only measured during this phase. In this treatment N2O was also produced in the centre both initially and after the temperature of the compost had dropped to below 45 degrees. Emissions of N2O were only significant in the low temperature phases. Production of N2O was probably restricted to the surface layers during the thermophilic phase of composting. Total carbon dioxide (CO2) emissions were 737 and 0.09 kg C/t fresh weight from the heaps with bulk densities of 0.44 and 0.23 kg/l, respectively. Methane emission from the high density compost heap was 191 g C/t and N2O emission was 58 g N/t. Emissions of CH4 and N2O from the low density heap were not detected. The greenhouse effect of gas emission from the high density compost heap was calculated by multiplying the climate force efficiencies and the cumulated gas emission. This calculation showed that CH4 contributes almost as much to the global warming potential as CO2, and N2O contributed twice as much as CO2.
The study examined the extent to which n-3 PUFA from different sources were biohydrogenated in the rumen and their effects on rumen microbial efficiency and whole tract nutrient digestibility. Four ruminally and duodenally cannulated whether lambs were used in a 4 x 4 Latin square design. Four iso-energetic and iso-nitrogenous diets based on dried grass were formulated to provide similar fat levels (60 g/kg DM) from different sources; Megalac (palmitic acid. C16:0; Control), whole linseed (alpha -linolenic acid, C18:3n-3; Linseed) fish oil (eicosapentaenoic acid, C20:5n-3, EPA and docosahexaenoic acids C22:6n-3, DHA; Fish oil) and whole linseed plus fish oil providing equal amounts of oil (LinFish). Diets were offered at a rate of 1.2 kg/day in 12 equal portions. Total fatty acid intake was similar on all diets whilst duodenal fatty acid flow varied between 101, 94, 87 and 90 % of dietary intake for animals fed the Control, Linseed, Fish oil and Linfish diets respectively. Duodenal flow of C18:3 n-3 in animals fed the Linseed diet was twice that of animals fed the Control diet (P < 0.01)whilst animals fed the Fish oil diet had a significantly greater flow of EPA and DHA than those fed any of the other dietary treatments. Duodenal flow of ri ans C18:1 in animals fed the Linfish diet was significantly greater than that in animals fed either Linseed, Fish oil or Control diets (P < 0.001). Biohydrogenation of C18:3n-3 was 80 to 93 % in all diets whilst that of C20:n-3 and C22:6n-3 was 72 to 79 % in diets that contained fish oil or linseed and fish oil. Apparent fatty acid digestibility (duodenum to rectum) tended to be greater for unsaturated than saturated fatty acids whilst whole tract Fatty acid digestibility (mouth to rectum) was significantly greater in animals fed diets containing fish oil (P < 0.05). All dietary n-3 PUFA sources decreased microbial protein synthesis and efficiency when expressed as either gN/kg organic matter (OM) apparently or truly degraded in the rumen. Additionally, the inclusion of fish oil increased the proportion of propionate in the rumen whilst depressing the rumen digestibility of OM and fibre (P < 0.01), but had no significant effect on whole tract OM or fibre digestibility.
The aim of this study was to determine whether the inclusion of a condensed tannin (quebracho tannin, QT) and/or the elevation of dietary protein could reduce Trichostrongylus colubriformis establishment and existence in the small intestine of lambs. Thirty-six lambs (mean liveweight 32.6 +/- 3.9 kg) were randomly allocated to one of six experimental groups, groups 1-5 were parasitized with a trickle infection of 3000 infective Trichostrongylus colubriformis larvae daily, whilst group 6 remained as uninfected controls. Experimental diets were formulated to contain 222 g CP/kg (high protein) or 97 g CP/kg (low protein) with or without the inclusion of 50 g QT/kg. All six animal groups were fed the low protein diet, group 2 fed low protein diet+QT, for one month prior to infection (groups 1-5). Once nematode eggs were observed in the faeces, diets were abruptly changed in three experimental groups. Group 1 remained on the low protein diet, group 2 remained on the low protein+QT diet, group 3 changed to the high protein diet, group 4 changed to the high protein + QT diet, group 5 changed to the low protein + QT diet and group 6 remained uninfected and fed the low protein diet. Production, haematological and parasitological parameters were monitored at regular intervals. Results show that parasitized animals fed the high protein diet achieved growth rates similar to those of uninfected low protein-fed lambs. Inclusion of dietary QT did not depress liveweight gain. Total daily faecal egg counts declined after feeding the high protein diet. Inclusion of QT into the low protein diet also reduced faecal egg counts to similar levels observed in the high protein-fed lambs. The inclusion of QT into the high protein diet did not further reduce faecal egg counts. No significant differences in the haematological parameters measured were observed between infected animals (groups 1-5), suggesting that the beneficial effect of dietary QT in the low protein diet is unlikely to be mediated through an immune response. These data suggest that the inclusion of QT in low protein diets may be an alternative to feeding high protein diets to reduce nematode burden in lambs.
Despite numerous reports on the positive effects of vesicular arbuscular mycorrhizae (VAM) on plant growth in temperate soils, surprisingly little data exist on the importance of VAM for crop growth on acid sandy soils of West Africa. A pot experiment conducted with local genotypes of pearl millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor L. Moench) and cowpea (Vigna unguiculata) with and without phosphorus (P) application in a sterilized sandy soil from a farmer's field in Niger shelved large growth-enhancing effects of VAM. Phosphorus application led to 18- and 24-fold increases in pearl millet root and shoot dry matter independently of VAM, whereas the shout and root dry matter of sorghum and cowpea depended largely on the interaction between P application and VAM. With P, VAM increased total uptake of P, K, Ca, Mg and Zn by 2.5- to 6-fold in sorghum and cowpea. On severely P deficient West African soils P application can lead to large increases in early root growth, a prerequisite for early mycorrhizal infection and a subsequent significant contribution of VAM to enhanced plant growth and nutrient uptake.
A field experiment was conducted for two years (1994-96) to evaluate three nitrogen fixing bacteria (NFBs) namely Azotobacter, Azospirillum and Beijerinckia as foliar biofertilizers on mulberry (Morus spp.). Foliar application of these bacteria in their specific culture media with half of the recommended dose of N as a basal application of chemical fertilizer were compared with the recommended dose of N (300 kg/ha per year in four equal splits) but without biofertilizer. Other controls for comparison were respective culture media with half N. All the NFBs improved leaf yield over their respective controls (specific culture media). The addition of Azotobacter resulted in significantly greater yield than that given by the recommended dose of N. The Beijerinckia treatment resulted in a leaf yield equal to that from the recommended dose of N and Azospirillum reduced leaf yield in comparison to that from the recommended N treatment although the yield from Azospirillum treatment was more than that from the culture medium treatments. A combination of NFBs where Azotobacter was one of the components improved leaf yield over single NFB treatments. NFBs also resulted in improved leaf quality as indicated by their protein content and their impact on silkworm rearing and cocoon production when treated leaves were subjected to bioassay. The use of these NFBs, particularly the Azotobacter, as a foliar biofertilizer to increase mulberry leaf production has not been investigated before.
Soya beans, like other legumes, contain low concentrations of the nutritionally essential sulphur amino acid, methionine. Cysteine, although not an essential amino acid because it can be synthesized from methionine, also influences the nutritional quality of soya bean products when it is only present in low levels. A low cysteine: content will also aggravate a methionine deficiency. Soya bean lines deficient in 7S protein subunits have been identified. The 7S proteins contain substantially less methionine and cysteine than the 11S proteins. With the myriad of genetic null alleles for these subunits it may be possible to tailor the 7S/11S storage protein ratio and their total composition in seeds to include only those subunits with the richest sulphur amino acid composition. Cotyledon feeding experiments, using isolated soya bean cotyledons, demonstrated that addition of methionine to the culture media caused increased synthesis of both proteins and free amino acids but the mechanism by which this takes place is not clear. Biotechnological approaches to improve nutritional value of soya brans include elevated expression of genes that originate from other species which encode high-sulphur proteins. High level expression of a 2S Brazil nut albumin gene in soya bean resulted in raised methionine concentration although the Brazil nut gene is highly antigenic and therefore will not be useful in production agriculture. Modification of glycinin to increase sulphur amino acid content is possible, and these gene products are capable of normal assembly into trimers in vitro although are rapidly degraded in vivo by the asparaginyl endopeptidase responsible for post-translational modification of proglycinin. Solutions to the methionine deficiency may be anticipated from a combination of approaches followed in laboratories worldwide. Many of these approaches are not without difficulty but, despite this, the likelihood is that soya beans with improved nutritional quality (which may not be confined to sulphur-containing amino acids as other nutritionally essential amino acids are also valuable) will be available in the near future. It will be essential to confirm that the increased total methionine (or other amino acid) is digestible to the animal to at least the same degree as conventional cultivars.
Near infrared spectroscopy (NIRS) is widely used in the flour milling industry for rapid determination of moisture and protein in wheat. However, these measurements give little indication of the nutritive value of wheat when fed to poultry or pigs. Accurate estimates of nutritive value require specialist facilities and are time-consuming and costly. Accordingly, prediction from chemical or NIRS measurements would be of some considerable benefit. In the current study 160 samples of wheat, representing 24 different varieties, were used to generate NIRS calibration equations for chemical, nutritive and agronomic characteristics. Predictions of chemical constituents in wheat were very accurate. Coefficients of determination (r(2)) were 0.94 for dry matter, 0.90 for crude protein, 0.97 for ash, 0.78 for starch and 0.98 for oil. True metabolizable energy in broiler chickens was predicted more accurately (r(2) = 0.52 for adult birds, 0.74 for young birds) than apparent metabolizable energy (r(2) = 0.45). Digestible energy (r(2) = 0.17) and nitrogen digestibility (r(2) = 0.22) in pigs were not predicted very accurately on a smaller subset (n=33). Agronomic characteristics were predicted very accurately (r(2) = 0.98 hardness, 0.80 bushel weight, 0.99 thousand-grain weight). Predictions of nutritive value of wheat from chemical or agronomic characteristics are very inaccurate, since coefficients of determination vary from zero to 0.25. It is concluded that NIRS can accurately estimate the chemical composition of wheat, but accurate prediction of nutritive value is reduced by animal variation. Nevertheless, NIRS is potentially more reliable for assessing nutritive value than chemical composition or agronomic characteristics.
Three animal manures cross-labelled with N-15 in either the urine, faeces or straw fractions were prepared. After a storage period of 86 days when the manures were exposed to either composting or to anaerobic storage, portions of the manures were incubated in six differently textured soils with clay contents ranging from 11 to 45%. Evolved CO2-C was determined during a 266 day incubation and inorganic N and N-15 in soil were measured at the termination of the incubation. The mineralization of C was analysed using first-order kinetics, and two C pools with fast (P-1) and slow (P-2) turnover rates were estimated. The total conversion of added C (P-s) was estimated as P-s = P-1 + P-2. The cumulated CO2 production was considerably higher from soils incubated with anaerobically stored manure compared with soils amended with composted manure. CO2 production levelled off after c. 60 days in the three sandier soils whereas CO2 continued to be produced throughout the incubation from the three soils with the highest clay content. More C was assigned to the easily decomposable P-1 pool in the sandiest soils whereas the more recalcitrant P-2 pool was larger in the soils with higher clay content. Because of the different relationships between soil texture and C pools, P-s ended up being similar for five of the six soils. When taking C losses during the preceding storage into account, the accumulated C losses during storage and after incubation in soil accounted for 60 and 54% of C initially present in the composted and anaerobically stored manure, respectively. Net N mineralization which averaged 16% of applied organic N took place in all soils amended with composted manure. Soils with anaerobically stored manure showed net immobilization after the 266 days of incubation. The amount of N immobilized accounted for up to 30% of the inorganic N applied with the manure. As anaerobically stored manure generally loses less inorganic N during storage, it may contain more inorganic N than composted manure at the time of held application. Because of the immobilization that takes place after application of anaerobically stored manure to soil, the immediate levels of plant available N in soil may not be as different from soil supplied with composted manure as could be expected from the inorganic N content in the two types of manure. However, when considering the manure as a N resource, anaerobic storage is superior to composting.
A 5-year study was conducted from 1988 to 1992 at three sites in Niger to determine the effects of crop rotation of a cereal and legumes and nitrogen fertilizer on chemical properties of the soil (0-20 cm) and yield of pearl millet (Pennisetum glaucum (L.) R.BR.), cowpea (Vigna unguiculata (L.) Walp.), and groundnut (Arachis hypogea L.). Four N levels and rotation treatments including continuous fallow were investigated. Soil samples taken from the top 20 cm depth at the end of the experiment from treatments without nitrogen application which included continuous fallow, fallow-millet rotation, groundnut-millet rotation, cowpea-millet rotation, and continuous millet were analysed for soil pH, organic carbon, total nitrogen and exchangeable bases. Fertilizer N significantly increased yield of pearl millet, cowpea and groundnut. Continuous monocropping of pearl millet resulted in lower yields across N levels compared to legume-millet rotations. Legume yields were also consistently lower in monoculture than when rotated with millet. There was a decline in organic matter under continuous millet, cowpea-millet rotation and groundnut-millet rotation. The fallow-millet rotation supplied more mineral N than the legume-millet rotations. Nitrogen availability was greater in cowpea-millet rotation than continuous millet. Crop rotation was more productive than the continuous monoculture but did not differ in maintaining soil organic matter. The legume-millet rotation at 30 kg/ha N appears to be the most viable for millet production. Research should focus on understanding the effect of legume/cereal intercrops and rotations on soil productivity.
In situ and in vitro rumen incubations were used to determine the effect of condensed tannins (CT) on the solubilization and degradation of the plant protein from white clover (Trifolium repens) and Lotus corniculatus. These forages contained, respectively 0.3 and 22.1 g CT/kg dry matter (DM). The sheep used for the experiments were also fed either white clover or L. corniculatus. Effects of CT were determined by making measurements in the presence and absence of polyethylene glycol (PEG; molecular weight 3500), which binds and inactivates CT. The loss of DM, neutral detergent fibre (NDF), total nitrogen (N) and Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase; EC 22.214.171.124; fraction I leaf protein) from polyester bags suspended in the rumen of sheep was measured. The loss of these constituents from polyester bags suspended in the rumen was used as a measurement of their solubilization. Degradation was defined as the disappearance of Rubisco from white clover and L. corniculatus added to in vitro incubations with rumen fluid obtained from the same fistulated sheep fed either white clover or L. corniculatus. In the absence of PEG, the in situ loss of Rubisco from L. corniculatus was less rapid than the loss of this protein from white clover when each forage was incubated in the rumen of sheep fed the same diet. Addition of PEG tended to increase the loss of Rubisco from L. corniculatus, suggesting that CT slowed the rates of solubilization of Rubisco from this forage. Effects of rumen fluid were small, but there was some evidence that the rumen fluid in sheep fed L. corniculatus reduced the solubilization of Rubisco from white clover. The action of CT did not inhibit the in situ loss of NDF from either white clover or L. corniculatus. In the absence of PEG, the in vitro degradation of Rubisco from L. corniculatus was slower when compared to the degradation of this protein from white clover; PEG addition increased the degradation of Rubisco from L, corniculatus, but not from white clover, showing that CT was the causal agent. The addition of CT extracted from L. corniculatus markedly depressed the degradation of Rubisco from white clover, with the effect being completely reversible by PEG. The large subunit (LSU) of Rubisco was consistently degraded at a faster rate than the small subunit (SSU) and added CT had a greater effect in slowing the degradation of the LSU compared to the SSU. There was little difference in the degradation of Rubisco when rumen fluid from sheep fed either white clover or L. corniculatus was used for in vitro incubations. It was concluded that the action of CT from L. corniculatus reduces the digestion of protein in the rumen of sheep. This effect is predominantly due to the action of CT reducing the degradation of plant protein, although CT also reduced the solubilization of plant protein. The main effects of CT on protein solubilization and degradation seemed to be produced locally by CT present in plant tissue; transfer of these effects through rumen fluid was small in magnitude.
A three factor experiment with winter wheat (Triticum aestivum L.) was carried out during two years on a coarse sandy soil in Denmark. The factors comprised four irrigation strategies including no irrigation, three nitrogen levels providing 67, 83 or 100 % of the recommended nitrogen rate, and two strategies for control of leaf diseases (with and without fungicides). Different varieties were used in the two years, Pepital in the first year and Hussar in the second year. Mildew dominated the trial in the first year, but was almost absent in the second year. Septoria occurred in both years, but most severely in the second year. Irrigation increased grain yield, but there were no significant differences between the three strategies, where irrigation was applied. The effect of irrigation on yield was almost solely via an effect of increased transpiration, whereas water use efficiency and harvest index was unaffected. There was a significant interaction for grain yield between irrigation and nitrogen strategies with higher irrigation effects at higher nitrogen rates. This interaction was absent at high disease levels. Increasing nitrogen rate increased grain yield in the second year, but not in the first year. This was attributed to an increasing mildew incidence with increasing nitrogen rate. Irrigation also increased mildew incidence. This caused significant interactions for grain yield between fungicide application and nitrogen rate and between fungicide application and irrigation strategy. Septoria was also significantly affected by both nitrogen and irrigation strategies, but to a lesser degree and not in a consistent manner. The main effect of disease on grain yield was through a reduction in harvest index and a reduction in grain weight. Increasing nitrogen rates slightly reduced harvest index both on a dry matter and on a nitrogen basis. The interaction effects were smaller than the effects of the main factors, and the effect of changes in irrigation or nitrogen strategy on disease incidence could not substitute for the effective disease control obtained by fungicides. The results do, however, indicate possibilities of improving the efficiency of current decision support systems for both fungicide control by better timing of application and irrigation scheduling by reducing water application.
Rotations of barley with feed legumes produce more biomass and crude protein than barley-fallow and continuous barley sequences, but scope remains to improve the potential value to farmers of feed legume-based systems. This gaper summarizes B-year results from two sites from 2-year rotations of barley with: narbon vetch (Vicia narbonensis) and lathyrus (Lathyrus sativus), each harvested mature; and common vetch (Vicia sativa). harvested by simulated green-grazing and mature, all in factorial combination with four NP fertilizer regimes applied biennially to the barley. Mean yield differences between rotations were quite small. but at the drier site the narbon vetch rotation was significantly superior in both total biomass and crop total nitrogen. Other results implied yield compensation between barley and legume phases: barley performance was relatively depressed at the wetter site after high-yielding narbon vetch but was relatively enhanced at both sites after green-grazed common vetch. Evidence from year-round soil-water monitoring suggests that the benefit following green grazing may have arisen, in part, from a small carry-over of profile moisture between crops not much inferior to that residual from a fallow year. Both crop phases responded strongly to biennial P fertilizer; and barley responded strongly to three rates of N-fertilizer, but a sometimes significant curvilinear component to this response reflected a tendency for grain yields to be depressed by added nitrogen in the driest years. But interactions between N-rates and rotations were not significant. It was concluded that narbon vetch may have greater potential than common vetch and lathyrus for mature harvest in drier areas, but its unsuitability for grazing green is a limitation. Flexibility of utilization is important, to accommodate the needs of different farmers and the exigencies of different seasons. The green-graze option has major potential where there is a demand for high-quality spring grazing; and indications that barley may be as productive after green-grazed vetch as after a year of fallow suggest an alternative approach for farmers who have previously avoided legumes in order to maximize barley production.
The concentration of n-alkanes in the cuticular wax of plants can be used to estimate the composition of the diet selected by free-ranging animals. The aims of this study were to characterize the n-alkane profiles of developing leaves and evaluate the degree of chemical discrimination between six browsed broadleaf tree species: European ash (Fraxinus excelsior L.): flowering ash (Fraxinus or nus L.), hornbeam (Carpinus betulus L.), hazel (Corylus avellana L.), mountain ash (Sorbus aucuparia L.) and beech (Fagus sylvatica L). The effect of the stage of development was examined by considering five different vegetative stages: dormant bud (DB), late bud (LB), young leaf (YL): mature leaf(ML) and senescing leaf(SL). Five samples per each vegetative stage and species, gathered in a mixed woodland of the Italian Eastern Alps between February and October, were analysed for their n-alkane concentrations (C-23-C-30). The residual coefficient of variation was 15.5 % on average for the individual n-alkanes considered. There were noticeable differences in individual and total n-alkanes content between species. In particular, C-27 was the predominant n-alkane in beech and C-33 was found in high proportions in the two species of Fraxinus; hazel and flowering ash had a higher total n-alkanes content than the overall mean, while the lowest values were found in hornbeam and beech. The n-alkane profile also underwent important changes during the vegetative development, with different extent and direction according to the species. In the three successive leaf stages, a tendency for a progressive increase in the longest chain homologues was observed. In any case, the young leaf stage differed most from the contiguous stages. Canonical discriminant analysis indicated that the n-alkane profile of buds and leaves were mathematically distinguishable and the chemical differences between species were persistent over the plant vegetative development.
The current experiment was conducted to study the effect of different doses of tannic acid, a hydrolysable tannin, on ruminal degradation and post-ruminal digestion of treated soya bean meals (SBM) in sheep. Samples of SBM were prepared by spraying 100 g SBM with 100 mi distilled water containing 0, 1, 5, 10, 15 or 25 g of commercial tannic acid (S-0, S-TA1, S-TA2, S-TA3, S-TA4 and S-TA5, respectively). Three ruminally cannulated awes, that had never consumed tannic acid previously, were used to determine in situ degradability of tannic acid-treated SBM. Intestinal digestibility of protein remaining after 16 h rumen incubation was estimated in vitro. Extent of rumen degradation of SBMs was significantly (P < 0.05) affected by the tannic acid treatment. All doses of tannic acid used in this experiment, even the lowest one (S-TA1), significantly decreased the extent of N degradation but only doses higher than that used to treat S-TA3 reduced the extent of DM degradation. This reduction in the extent of DM and N degradation was mainly due to a marked decrease in the immediately degradable fraction (a), which was observed in all treated SBM, and to a lower rate of degradation (c), observed in meals S-TA3, S-TA4 and S-TA5. Intestinal digestion of the non-degraded protein was decreased (P < 0.05) by treatment with the two highest doses of tannic acid (those used to treat meals S-TA4 and S-TA5). It was therefore concluded that tannic acid can exert a negative effect both on rumen degradation and on intestinal digestion of SBM, this effect being clearly dependent on the dose used to treat the SBM.
Data from a three factor experiment carried out during two years were used to analyse the effects of drought, nitrogen and disease on light interception (IPAR) and radiation use efficiency (RUE) in winter wheat (Triticum aestivum L.). The factors in the experiment comprised four irrigation strategies including no irrigation, three nitrogen levels providing 67, 83 and 100% of the recommended nitrogen rate, and two strategies for control of leaf diseases (with and without fungicides). Light interception was estimated from weekly measurements of crop spectral reflectance. This method was compared with estimates derived from crop area index measured by plant samples or by using the LAI2000 instrument. There was a good correspondence between the different methods before anthesis, but an overestimation of light interception with the methods using crop area index after anthesis due to an increase in non-photosynthetic active leaf area. Irrigation increased both IPAR and RUE. The relative increase in IPAR for irrigation was greater than the relative increase in RUE in the first year, whereas they were of similar size in the second year. The differences between the years could be attributed to changes in timing of the drought relative to crop ontogenesis. Increasing nitrogen rate increased IPAR, but caused a small decrease in RUE in both years. This reduction in RUE with increasing nitrogen concentration in leaves was also found to be significant when disease levels and drought effects were included in a multiple linear regression. Fungicide application increased IPAR in both years, but RUE was only significantly reduced by disease in the first year, where mildew dominated the trial. The data were also used to estimate the coefficients of partitioning of dry matter to grains before and after anthesis. About 40% of dry matter produced before anthesis and about 60% after anthesis was estimated to contribute to grain yield. The low fraction after anthesis is probably due to the fact that it was not possible to estimate changes in RUE with time, which may lead to biases in the estimation of partitioning coefficients.
The effect of sulphur (S) application on the efficiency of nitrogen (N) use was investigated using cut plot experiments on two contrasting soil types. Nitrogen was applied at 200 and 450 kg N/ha per year, with and without 38 kg SO3/ha (15.2 kg S/ha) per cut. Over three conventionally timed silage cuts for 2 years, measurements were made of herbage dry matter, the yield of N and S in herbage and losses of N and S by leaching, and N by denitrification. Herbage dry matter and N yields were significantly increased by the application of S at the high N level at the sandy loam site (Halse). At the clay loam site (Great Close) the application of S had no significant effect on herbage dry matter or N yields. At Halse, the pattern of response through the year was not the same in the 2 years studied, although in both, the effect of S was significant at third cut at high N. Deficiency was suggested by the N:S ratio of herbage on the plots without S, especially at first cut, and at later cuts at Halse. Nitrate leaching was reduced by S at Halse by 72% and 58% with high N in 1997 and 1998, respectively, and by 10% and 5% on the low N treatments in 1997 and 1998, respectively. Application of S at high N at Halse reduced the peak concentration of nitrate-N in leachate from 27.3 mg N/l to 9.3 mg N/l. At Great Close, application of S had no significant effect on the amount or peak concentration of nitrate-N leached. The improvement in efficiency reported at Halse suggests that on permeable soils receiving high levels of N, the application of S could have a large effect on nitrate leaching and its associated environmental impact.
A study on the use of quebracho tannins as chemical additives was carried out at the Spanish Council for Scientific Research, Leon, Spain during 1998 by conducting two experiments. In the first experiment, three ruminally cannulated ewes were used to determine in situ degradability of soya bean meals (SBM) treated with different doses of quebracho tannin. Samples were prepared by spraying 100 g SBM with 100 ml distilled water containing 0, 1, 5, 10, 15 or 25 g of commercial quebracho powder (S-0, S-Q1, S-Q2, S-Q3, and S-Q5, respectively). Intestinal digestibility of non-degradable protein was estimated in vitro. The rapidly degradable protein fraction of all quebracho treated soya bean meals was different (P < 0.05) from the non-treated SBM (S-0: 0.154), with values ranging from 0.032 to 0.133. S-Q4 and S-Q5 showed lower fractional rates of degradation of the protein than S-0 (0.042 and 0.046 v. 0.082, respectively). By contrast, in vitro digestibility of the non-degradable protein was not significantly affected by the treatments imposed, with the exception of treatment with the highest dose of quebracho tannin in which intestinal digestion was reduced (0.939 v. 0.826 for S-0 and S-Q5, respectively. P < 0.05). In the second experiment, ten ruminally cannulated ewes were used to examine the effect of a daily dosing of quebracho tannin into the rumen on the degradation of the quebracho-treated SBM. Long-term dosing of quebracho tannin did not increase the ability of the rumen microbes to degrade tannin treated SBM. It was therefore concluded that quebracho tannins could be used as chemical additives for improving the digestive utilization of protein-rich feeds in sheep.
A field study was conducted on an experimental held of the Maize Research Institute Zemun Polje-Belgrade (latitude: 44 degrees 49' N), Yugoslavia over a 3 year period (1994-1996). The objective of this study was to find the optimal spatial arrangement of a maize-beans intercrop in irrigated and rainfed farming systems. Plant arrangement patterns in an intercropping system did not significantly affect LAI values in maize compared with a sole crop, while irrigation had a greater positive influence on it. Leaf area values of beans were Inore sensitive to the same treatments. Microenvironmental conditions in maize-bean mixtures were Inore favourable for bean crop than for sole brans. An intercropping system had a greater influence on yield components of maize. Component combination 1/2:1/2 (maize:bean) was most effective in all yield components of maize. Intraspecific competition appears to be more intense than interspecific competition in both crops. Yield component of bean was more sensitive to water regime of the site than to planting pattern in an intercrop. Irrigation increased all yield components of bean (especially pod number). The intercropping system decreased harvest index in both crops compared with monocrops. Maximum total grain yield was in 1994 in irrigated maize-bean intercrop 1/2:1/2, with highest efficiency being in an intercrop in irrigation in 1995. The Land Equivalent Ratio (LER), based on grain yield, was consistently greater than 1.0 in an irrigation water regime in 1995. Proportion of maize:bean = 1/2:1/2 gave the highest increase of yield (LER = 1.54). Under conditions of chernozem soil type in Zemun Polje, with often-expressed dry periods, irrigation is a very important measure for increasing maize-beans intercrop productivity.
For welfare reasons, fattening pigs on organic farms are raised on deep litter in the open with simple, flexible climate tents for shelter. Within this system, the nitrogen (N) flow both during fattening of the pigs from 17 to 100 kg liveweight in winter and during composting of the deep litter from the enclosures in summer was studied. During the fattening period, the pigs were provided with barley straw at four daily rates (0.67, 1.21, 1.32 and 1.87 kg) per kg increase in liveweight. During the summer period, N balances from four enclosures receiving straw at around the 1.32 kg rate were examined. Temperatures in the deep litter mat and in the compost heap were determined. as well as concentrations of ammonia (NH3) and nitrous oxide (N2O) in the compost heaps. The temperature increased after 4 weeks to between 40 and 70 degreesC in the deep litter mats receiving > 1.21 kg straw; the highest temperatures were observed in the mats with the highest straw rate. Temperatures exceeded 50 degreesC in all compost heaps. In the deep litter mars and compost heaps the highest temperatures were recorded for the longest periods in the material containing the most straw. The initial concentration of NH3 in the gas phase of the compost heaps was > 10 mg NH3-N/m(3), which dropped to zero within 1 month. After the NH3 concentration had fallen, the amount of N2O increased significantly for a period in the two heaps with 1.21 and 1.32 kg straw. Over 120 days in summer, an average of 16.3 +/- 6 % N was lost from the four enclosures strawed at a rate of 1.32 kg (+/- 0.2 kg) straw per kg increase in liveweight. During the winter 12-24 % of the N excreted was lost during a fattening period of 119-134 days, and 15-42 % of the N stored was lost during the following composting period of 143 days. In total? 29-54 % of the N added to the deep litter mat in excretion and straw was lost during the fattening period (119-134 days) and subsequent storage (143 days). The lowest loss was recorded from deep litter strawed daily with 1.32 kg straw per kg increase in pig liveweight.