bluuebunny/crossref_metadata_2025 huggingface dataset:
Denitrification in nitric-acid-treated cattle slurry during storage
Authors: Oenema O. , Velthof G.L.
Published: June 2020

Lowering the pH of cattle slurry with HNO3 was used to reduce NH3 volatilization during storage and after application. Incubation studies were carried out to examine possible NO3 losses and N2O emission from HNO3 treated slurry during storage. Batches of cattle slurry were treated with various amounts of HNO3 to obtain a pH range of 6.0 to 3.0. The slurries were stirred once or twice a week and stored for 6 months at 15 degrees C. Changes in pH, Eh, NO3- and NH4+ concn, and emissions of N2O, CO2 and CH4 were monitored. The loss of NO3- and the emission of N2O were related to slurry pH, being lowest at low pH. Cumulative loss of NO3- ranged from ~40 mmol/kg for slurries of target pH < or =>5.0 to ~400 mmol/kg for slurries of target pH 6.0. Homogenization of the slurries via stirring and addition of H2O2 decreased NO3- loss and H+ consumption. The strong pH dependence of NO3- loss, the production of N2O and the stoichiometry of H+ consumption and NO3- loss indicated that the loss of NO3- was mainly due to microbiological denitrification. Similar N2O production rates in the presence and absence of C2H2 indicated that nitrification was not an important source of N2O. It is concluded that lowering the pH to values 4.5 as well as regular and complete homogenization of the slurry via stirring are important for the success of the on-farm treatment of slurry with HNO3.
Field experiments with slurry and dicyandiamide: response of potatoes and effects on soil mineral nitrogen
Authors: Wadman W.P. , Neeteson J.J. , Wijnen G.J.
Published: June 2020

In the period of 1983-1985, 18 field experiments with potatoes grown for industrial starch production were set up in the Netherlands to investigate the effects of poultry-slurry application on tuber yield and on soil mineral nitrogen. Slurry was applied in autumn with and without the nitrification inhibitor dicyandiamide (DCD) and in spring without DCD. Control treatments without slurry or DCD were included. Various nitrogen fertilizer rates were applied to all slurry treatments. In autumn, following slurry application without DCD, slurry-derived nitrate moved to the 0.3-0.6 and 0.6-1 m soil layers. Following DCD-application, most of the slurry-derived nitrate remained in the 0-0.3 m soil layer. Maximum yields as estimated from a nitrogen fertilizer response function were slightly increased by the slurry application. Nitrogen supplied from the slurry decreased the amount of fertilizer nitrogen needed for maximum yield. Increasing the amounts of soil mineral nitrogen in June from slurry or applied inorganic nitrogen fertilizer increased residual soil mineral nitrogen at harvest.
Ammonia treatment of wheat straw. 1. Voluntary intake, chewing behaviour, rumen pool size and turnover and partition of digestion along the gastro-intestinal tract of sheep
Authors: Van Bruchem J. , Oosting S.J. , Lammers-Wienhoven S.C.W. , Leffering C.P.
Published: June 2020

Intake and digestion and rate of passage kinetics were studied in 6 wether sheep fed on ammoniated wheat straw (AWS) plus pelleted sugarbeet pulp, untreated wheat straw plus sugarbeet pulp, and untreated wheat straw supplemented with urea. Ammonia treatment increased intake and whole tract digestion (rumen + small intestine + large intestine) without significantly affecting rumen pool size and rate of passage. 91% of the increased intake of cell wall material in ammonia-treated straw was due to a higher rate of degradation of cell walls in the rumen. No significant effects of ammonia treatment on concentration, molar composition or rate of absorption of volatile fatty acids were observed. The rate of passage in the large intestine and the contribution of this region to digestion were not significantly affected by ammonia treatment. Rumination and eating time and daily number of rumen contractions did not differ among diets, but AWS showed a lower rumination time/kg NDF ingested than the other 2 diets. After ammonia treatment, whole tract digestion and rumen degradation of hemicellulose increased more than those of cellulose. The effects of ammonia treatment could not be attributed to its nitrogen content since there was no effect on any parameter, except rumen ammonia-N concentration.
Growth, yield and composition of four winter cereals. I. Biomass, grain yield and yield formation
Authors: Ellen J.
Published: June 2020

A field experiment with 3 cultivars of each of 4 winter cereals (wheat, rye, triticale and barley), sown at about 320 plants/msuperscript 2, was conducted on a fertile clay soil in the central Netherlands. The N fertilizer was split-dressed: 120 kg/ha in total for wheat and triticale, and 60 kg/ha for rye and barley. The fewest shoots/msuperscript 2 were found in triticale (828/msuperscript 2), and the most in barley (1477/msuperscript 2). The average decrease in number of shoots during shoot/ear development was 51% in wheat, 54% in rye, 49% in triticale and 67% in barley. The rate of crop development was largest in rye and barley; they flowered and matured earlier than wheat and triticale. Rye was the first to attain a closed canopy (LAI >3), and had the lowest maximum LAI and shortest leaf area duration. Wheat and triticale stayed green longest. Average specific leaf weight was 4.3 mg/cmsuperscript 2 in wheat and triticale, and 3.7 mg/cmsuperscript 2 in rye and barley. The growth rate of the grains at the linear stage was fastest in barley (1.89 mg grain-1 d-1) and slowest in rye (0.89 mg grain-1 d-1). Total aboveground DM production was 18 790 kg/ha in wheat, 15 230 kg/ha in rye, 18 300 kg/ha in triticale and 12 460 kg/ha in barley. Grain yields (t/ha) were 8.74 (wheat), 6.64 (rye), 8.20 (triticale) and 6.62 (barley). Cultivar differences in grain yield and in yield components were mostly smaller in wheat and rye than in triticale and barley. The harvest index was highest in barley (53.3%) and lowest in rye (43.7%); in some plant species there were marked differences between cultivars, but in others there were not.
Digestion in defaunated and refaunated sheep fed soybean oil hydrolysate or crushed toasted soybeans
Authors: Van Nevel C.J. , De Smet S. , Demeyer D.I.
Published: June 2020

Defaunated then refaunated sheep were given diets containing soyabean oil hydrolysate (SOH: 70 g/day) or an equivalent amount of lipids administered as crushed toasted soyabeans (TSB). Defaunation increased molar percentage of propionate in the rumen, while butyrate decreased. SOH caused a similar effect in both the defaunated and refaunated rumen, while the effect on acetate proportions was variable. Protozoal counts were lower after feeding SOH. Crushed toasted soyabeans had a minor effect on rumen fermentation pattern. Rumen digestibility of organic matter was decreased by both defaunation and SOH feeding, with a concomitant shift in digestion to the lower intestinal tract. Total tract digestibility was not affected. Both treatments increased nonammonia N flows at the duodenum, but this was only significant with defaunation. Total tract digestion of N remained almost constant. Defaunation resulted in more microbial protein reaching the duodenum. Except for the TSB diet, total lipid leaving the rumen equalled intake. Total tract digestibility of total lipid was much higher with SOH and TSB than with controls. Defaunation almost doubled microbial growth efficiency and this value tended to increase by SOH feeding. The decrease of protozoal count or even elimination of protozoa after lipid feeding could not entirely explain the change in rumen metabolism, as additional changes in defaunated sheep were shown.
Response of a Scots pine (Pinus sylvestris) stand to application of phosphorus, potassium, magnesium and lime. 3. Foliar nutrient concentrations and stand development
Authors: Arnold G. , Van Diest A.
Published: June 2020

In 1985-88, a 25-yr-old Scots pine forest in Netherlands was limed and fertilized with P, K and Mg in a factoral design. This paper addresses effects of these treatments on foliar nutrient concentrations and tree growth. Stem volume increments of individual trees were measured. Average annual volume growth was estimated to be about 16 msuperscript 3/ha, which may be a slight underestimation. P and K showed increased foliar concentrations immediately after treatment and were the only elements that significantly increased volume growth in 1988-91. Additional annual volume growth of individual trees brought about by P and K corresponded with 0.9 and 2.2 msuperscript 3/ha, respectively. Foliar Mg and Ca increased later and insignificantly reduced and increased volume growth, respectively. Lime and Mg applications tended to lower foliar N. When absolute foliar concentrations and element ratios were compared to Dutch and German standards, it appeared that application of some of these standards in present research would not always have given a fully correct prediction of growth responses to nutrient additions.
Carbon in Dutch forest ecosystems
Authors: Nabuurs G.J. , Mohren G.M.J.
Published: June 2020

Present stock of carbon in living biomass, litter and stable humus and annual accumulation of carbon in stems of 15 forest types was quantified from inventory data on growth and standing volume, and forest soil information in combination with literature data on forest biomass, as part of the Dutch National Research Programme on Global Air Pollution and Climate Change. Forest area in the Netherlands is about 330 000 ha, mainly young plantations of conifers (Scots pine, Douglas-fir, larch) on poor, dry sandy soils. Average age is about 50 yr. Present average standing volume is 170 msuperscript 3/ha and average annual volume increment was 9.0 msuperscript 3/ha in 1984-89. About 63.7 Mt C is stored in the entire forest, including dead organic matter in forest soil, almost 60% as stable humus in the soil compartment. Average carbon stock in the stable humus is 113 t C/ha, whereas only 59 t C/ha is contained in living biomass and 19 t C/ha in litter layer. Average stock in living biomass is largest for beech stands (124 t C/ha). Annually, about 0.66 Mt C of atmospheric carbon is stored in stem volume increment when harvesting is not considered. On average, about half of annual storage is harvested each year, which means that forest acts as a net carbon sink for about 0.33 Mt C/yr. Largest net annual accumulation is attained in beech stands (1.8 t C/ha). Average annual net accumulation for the entire forested area amounts at present to some 0.97 t C/ha. Long rotations with species like oak, beech and Douglas-fir which may build-up a large standing biomass and which produce durable wood products, are most suitable for a long-term storage of carbon.
Growth and nutrient uptake of Douglas fir seedlings at different rates of ammonium supply, with or without additional nitrate and other nutrients
Authors: De Visser P.H.B. , Keltjens W.G.
Published: June 2020

Two pot trials were conducted on effects of soil acidification and excess ammonium on root and shoot development of juvenile Douglas fir (Pseudotsuga menziesii) on an acid sandy forest soil. Experiment I included a control treatment (without fertilizer application) and different supply rates of NH4. Application of other nutrients to the NH4-fertilized pots was constant, while at one supply level the added N included 50% nitrate in order to study effect of N form. High supply rates of ammonium suppressed root length growth, but did not affect shoot growth during one season of application. Root and stem growth was stronger with a mixture of ammonium and nitrate than with pure ammonium as N source. Experiment II examined balanced fertilization, additional to nitrogen, at low and high NH4-N supply during a two-year period. Second year bud break was retarded and shoot growth depressed at high levels of ammonium supply. In August of the second year nearly all trees died that had received a total NH4-N dose of 230 kg/ha. Addition of base cations and P to ammonium application raised P and K needle concentrations, but could not prevent adverse effects of NH4, and even increased acidification of soil. In both experiments presence of a litter layer tended to increase tree growth, and alleviated adverse effects of ammonium in soil and needles. A corresponding fertilizer application in a mature Douglas fir stand on the same soil improved nutrition of P and K as well.
Preserving genetic variance resources in commercial and non-commercial populations
Authors: Buis R.C. , Oldenbroek J.K. , Van Der Werf J.H.J.
Published: June 2020

Genetic diversity is the basis for livestock breeding. Diversity within breeds may be reduced by effective breeding methods in commercial breeds; diversity between breeds may be reduced by disappearance of non-commercial breeds. Two means of preserving diversity are discussed: the development of breeding methods that aim at genetic gain yet account for loss of diversity, and the setup of gene banks to preserve current diversity for future use.
Breeding goals for intensive but sustainable poultry meat production
Authors: Leenstra F.R. , Ehlhardt D.A.
Published: June 2020

The effects of selecting male parent breeding stock for efficiency of feed utilization (EFU) were compared with those of selection for body weight (BW). Selection for EFU resulted in an improved feed and protein efficiency at a certain fixed body weight when compared with BW selection. Correlated effects of selection for EFU (slaughter yield, viability, parent stock fertility) were favourable. For sustainable poultry meat production, losses in the production cycle through manure, slaughter offals and mortality should be minimized. The results of experimental selection indicate that selection for EFU may be a useful tool towards decreasing losses in poultry meat production.
Sustainability os small ruminant population on the Adja Plateau (South Benin)
Authors: Van Den Broek A. , Gbégo I.T.
Published: June 2020

Since 1986 the RAMR project (Recherche Appliquee en Milieu Reel) has conducted on-farm research on the Adja Plateau in Mono Province (South Benin). In this article, technical and socio-economic aspects of small ruminant production systems on the Adja Plateau are described. Monitoring of small ruminant flocks showed that about 25% of the small ruminants were sold annually. Export of nutrients as a result of the sale of animals (85 g N. 23 g P. 12 g K and 46 g Ca per hectare) was low compared with export through crop production. In-depth studies at village level showed that farmers mainly collected oil palm leaves, constituting 75% of the small ruminant rations, to feed their animals. Nutrients in collected oil palm leaves represented a substantial fraction (about 10%) of available nutrients in fields under oil palm. Proposals for future research on small ruminant production systems have to contribute to the sustainability of farming systems. Emphasis will be put on animal feeding and feed production integrating small ruminant and crop production.
Ecomorphology as a tool in fisheries: identification and ecotyping of Lake Tana barbs (Barbus intermedius complex), Ethiopia
Authors: Sibbing F.A. , Nagelkerke L.A.J. , Osse J.W.M.
Published: June 2020

Fisheries development of Lake Tana, Ethiopia, urgently requires the identification of its unknown units of fish stock. A diversity of large barbs (up to 80 cm SL), lumped into one species Barbus intermedius and contributing over 35% of the annual catch, consists of at least thirteen distinct morphotypes (Nagelkerke et al., 1994), possibly species. Their abilities and limitations in food selection and feeding can be predicted from structural specializations following functional morphological methods. Using ecomorphology, a spectrum of ecotypes ranging from detritivores to piscivores is predicted. Such hypotheses may be tested by analysing these fishes' intestinal contents. From knowledge of available food organisms and the trophic segregation thus found among barbs and sympatric species, a preliminary food web has been constructed. This food web, together with quantitative studies on population dynamics and energy flow, provides a biological framework for rational fisheries management aiming at sustainable production and protection of biodiversity.
Effect of fruit growth, temperature and irradiance on biomass allocation to the vegetative parts of cucumber
Authors: Marcelis L.F.M.
Published: June 2020

Cucumber plants were grown in a greenhouse at 18 or 25 degrees C with four intensities of fruit removal (1 fruit remaining for every 1, 3 or 6 leaf axils, or all fruits removed) or at three different levels of irradiance (shading with cheesecloth to give 100, 50 or 30% transmittance) in order to analyse the effects of fruit growth, temperature and irradiance on the dry matter allocation to leaves, stems, petioles and roots. With increasing irradiance, the dry weight of the vegetative part of the shoot increased, but the proportion of the total dry matter distributed to this part decreased. An increase in irradiance enhanced stem dry matter production less than leaf and petiole dry matter production which was in turn less stimulated than root dry matter production. In fruit-bearing plants, an increase in temperature had no effect on the dry matter allocation to the leaves, stems and petioles, but reduced the allocation to the roots. Fruit growth strongly reduced dry matter production of all vegetative plant parts, but the distribution between stems, leaves and petioles was only slightly affected. At 25 degrees, the dry matter distribution between the roots and the vegetative part of the shoot was not affected by fruit growth, but at 18 degrees, the root to vegetative shoot dry weight ratio decreased with increasing number of fruits on the plant. The biomass allocation between roots and shoot is discussed in relation to the functional equilibrium concept.
Determining developments in pesticide use: an application to the Netherlands
Authors: Oskam A.J. , Vijftigschild R.A.N.
Published: June 2020

Different causes of changes in pesticide use are analysed, with the situation in the Netherlands as background for empirical illustrations. The usual methodology assumes a large inventory study on pesticide use. This inventory study may contain a number of errors or rest upon incomplete information. During a certain period indicators of pesticide use are often more aggregate. Moreover, the introduction of new pesticides, the abolishing of some old ones and the fluctuation in pesticide use because of changes in weather and disease patterns make it very difficult to measure developments in pesticide use. This is, however, an important element in the targeting of the reduction of emissions. A methodology is presented which introduced, in a stepwise manner, new information within a large database to provide decision makers with relevant information. The methodology classifies different causes, such as inconsistency between different data sets, changes in the area of different crops, introduction of new and abolishing of old pesticides, developments in pesticide use and fluctuations in pesticide use. It is concluded that as a result of the importance of the 1st, 3rd and 5th categories, it is difficult to give a clear indication of the development in pesticide use and therefore the fulfilment of environmental targeting in volume of active ingredient.
Genetic correlations of clinical mastitis and feet and legs problems with milk yield type traits in Dutch Black and White dairy cattle
Authors: Groen A.F. , Hellinga I. , Oldenbroek J.K.
Published: June 2020

Direct selection for decreased disease incidence is difficult given low hsuperscript 2s and the absence of disease recording. Genetic correlations between diseases and type traits indicate possibilities for indirect selection; however, correlations often include experimentally instead of routinely scored type traits. The aim of this study was to estimate genetic correlations of clinical mastitis and feet and legs problems with milk yield and routinely scored type traits in Dutch Black and White [DBW; Dutch Black Pied] cows. From 1983 to 1991, the incidence of diseases was recorded at 44 farms with DBW dairy cattle. Records on 3617 cows sired by 224 bulls were analysed. Heritabilities for milk yield, type traits and diseases were obtained using an equal design multivariate Restricted Maximum Likelihood procedure considering all observations on a continuous scale. A bivariate threshold procedure was used to estimate hsuperscript 2s of diseases and genetic correlations of diseases with milk yield and type traits. Genetic correlations of clinical mastitis and feet and legs problems with milk yield were 0.16 and 0.26 respectively, and hsuperscript 2s for diseases were low 0.01-0.11. Unexpected positive relations between udder type traits and clinical mastitis were found (0.09-0.26), and possible reasons are discussed. Genetic correlations between type traits for feet and legs and problems of the feet and legs were negative -0.01 and -0.24 respectively. Final score for feet and legs could be used as a selection criterion to select to reduce the incidence of feet and legs problems.
Uncertainties in input-output coefficients for land use optimization studies: an illustration with fertilizer use efficiency
Authors: Bessembinder J.
Published: June 2020

The problem of uncertainties in input-output coefficients is examined, using the uncertainty in estimating the fertilizer use efficiency as an illustration. An example of uncertainty due to lack of knowledge on processes involved is the use of different approaches for estimating fertilizer use efficiency in two land use optimization studies. A further problem is uncertainty due to lack of data; this is illustrated with an example from the Atlantic Zone of Costa Rica. Very few data are available to determine fertilizer use efficiency and data from regions with similar soil and climate type are not available. Data from non-similar regions may not give a correct assessment of the possibilities in the region. Different concepts and sources of information result in different estimates of coefficients, which might in turn greatly influence the results of the linear programming model. It is therefore concluded that, rather than using one fixed value for a particular input-output coefficient, the effect of uncertainty in coefficients on the final results of the model should be examined.
The need to study and manage variation in agro-ecosystems
Authors: Almekinders C.J.M. , Fresco L.O. , Struik P.C.
Published: June 2020

Variation within agro-ecosystems is a universal but complex phenomenon which is present in each of the factors that determine the agro-ecosystem, i.e. the environment, genetic resources and management. Agrodiversity is defined as the variation resulting from the interaction between these factors. This variation manifests itself in many different forms, at different scales and levels of aggregation. Examples show that poor management of agrodiversity in high and low external input agriculture reduces output, output stability, resource-use efficiency and the production potential of the natural resource base. A better understanding of agrodiversity is required to improve its management. Also, analysis of variation in agro-ecosystems requires other approaches in research to be further developed in order to characterize, measure and understand relevant variation.
Formation of microsclerotia of Verticillium dahliae on various crops
Authors: Mol L.
Published: June 2020

In 2 pot experiments, potato (cultivars Element, Mirka, Ostara and Astarte), pea, sugarbeet, onion, flax, spring barley, faba beans, spring wheat and spring rape were inoculated with V. dahliae by root dipping or by growing the plants in artificially infested soil. In both treatments the dry matter yield and formation of microsclerotia were determined for aerial parts. In plants grown in infested soil, the DW and microsclerotia formation were determined in stubbles and roots as well. The highest numbers of microsclerotia per g plant material and per pot in the root dipping treatment were found on potato, flax and barley. The microsclerotia density on potato cv. Element, pea and barley was higher in the root dipping treatment than in the soil infestation treatment. The reverse was true for potato cultivars Ostara and Mirka. Dry matter yield of the harvestable organs of potato cultivars Element and Astarte, flax, sugarbeet and barley was lower in the root dipping treatment than in the soil infestation treatment. The greatest inter-crop differences in the microsclerotia yield/pot were in the aerial parts. Flax gave the highest numbers of microsclerotia/pot, followed by the 4 potato cultivars. The other crops had a much lower microsclerotia yield. It is suggested that the results will be useful for modelling effects of various crops on the soil population at crop and farm level.
Digestion versus composting of straw and hay: effects on composition of biomass residues
Authors: Oomen G.J.M. , Verschuur C.M. , Schiere J.B.
Published: June 2020

The effect of two decomposition processes, digestion and composting, was compared on the quality of the final residue from two substrates: hay and straw. The digestion was done by using dwarf goats on digestion crates and the composting process was simulated in buckets. Composting was allowed to continue to the same level of organic matter loss as achieved in a digestibility trial. The results indicated that the pattern of biomass decomposition, as measured by the fibre analysis in the Goering and Van Soest method, was similar between both processes and substrates. Absolute amounts of acid detergent lignin (ADL) did not change significantly throughout both decomposition processes, but the quantity of other fibre components decreased. Chemically, the ADL fraction made up a large part of the humus in the soil and though the results were variable, they suggested that the initial ADL content of a substrate indicates its humus building capacity. Concerning the nitrogen fractions, however, there were larger differences between the decomposition processes and substrates. Digestion left less nitrogen in the organic matter than composting, and the composting of straw even resulted in a net increase in nitrogen content.
The effect of manure and litter handling and indoor climatic conditions on ammonia emissions from a battery cage and an aviary housing system for laying hens
Authors: Koerkamp P.W.G.G. , Keen A. , Van Niekerk T.G.C.M. , Smit S.
Published: June 2020

Ammonia emissions from both traditional and new welfare-based housing systems for laying hens must be reduced to prevent detrimental effects on the environment. In a comparative study, the effect of manure handling (variation in drying and removal frequency) in a battery cage and the effect of manure handling (as in battery cage system) and litter treatment (removal of litter) in a Tiered Wire Floor (TWF) aviary system on the emission of ammonia were investigated. Each system housed 6480 hens, treatments were varied in time, and effects were analysed by means of time-series analysis. The hens in the TWF system dropped 22.5% of their excreta in the litter and the remaining part, like all manure in the battery cage system, was dropped on the manure belts. The estimated emission from the manure on the belts in both systems was 18.8 g/h (daily mean, manure removal twice a day), whereas the emission from the litter in the TWF system amounted to 62.5 g/h. Emission from the belt manure on a typical day increased by 14, 39, 109 and 177% from the 1st until the 4th day after manure removal. The effect of increasing temperature and water vapour pressure difference on emission was +17% and -22% per degree and per kPa, respectively. Drying of manure on the belts increased the dry matter content of the manure and showed a tendency towards lower emissions. The dry matter content of the litter varied between 780 and 840 g/kg, the mean total nitrogen content was 3.3% of the dry matter, and the layer thickness varied between 2 and 9 cm. Both the ammonia content, which ranged between 20 and 190 mg/kg, and the layer thickness of the litter influenced the emission from the litter positively.
Effect of nitrogen availability on dry matter production, nitrogen uptake and light interception of Brussels sprouts and leeks
Authors: Booij R. , Kreuzer A.D.H. , Smit A.L. , Van Der Werf A.
Published: June 2020

In field experiments with Brussels sprouts (cv. Kundry) and leeks (cv. Arcona) on a sandy soil, DM production and N uptake during crop growth were studied at different N application rates. N fertilizer application rate affected DM production, leaf area expansion and N uptake more strongly in Brussels sprouts than in leeks. When all N was applied before transplanting, Brussels sprouts showed a higher recovery of N fertilizer than leeks. This was explained by a higher rate of DM production in Brussels sprouts, a consequence of faster leaf area expansion. Late N application, whether as a part of a split application or not, increased N uptake more than DM production, so that tissue N concentrations increased. The relationship between N uptake and DM production depended on N availability and crop growth stage, and if all N was applied before transplanting, the relationship could be described by an asymptotic function. Plant plasticity allowed 'luxury consumption' of N to take place when availability was ample and 'dilution' of N when shortages developed during later growth stages. This implied an increasing tissue N concentration with increasing N application and a decreasing N concentration with increasing age. To achieve near-maximum DM production at any time, tissue N concentration should be kept at 2.8-3.1% DW during the whole growing period for Brussels sprouts as well as for leeks. However, in Brussels sprouts a minimum concentration of 1.2-1.5% DW still allowed growth. In both crops N uptake increased linearly with LAI until maximum leaf area (LAI = 4-5) was reached and this relationship was not affected by N application rate or by experimental year. Irrespective of N application rate or species, 2.3 g above ground biomass per MJ intercepted radiation was produced. Therefore, measurement of radiation interception by the canopy can be used as a tool to estimate the N status of the crop.
Outline for an integrated modelling approach concerning risks and economic consequences of contagious animal diseases
Authors: Horst H.S. , Dijkhuizen A.A. , Huirne R.B.M.
Published: June 2020

Management decisions on control of major infectious animal diseases may have a large impact, but are usually based on scarce and unreliable information. An integrated model which combines the various aspects of outbreaks and risks with economic consequences has yet to be developed. A flexible model with the possibility of evaluating the consequences of various strategies would be an important tool to aid in policy and decision making. In this paper a modelling approach is proposed which should lead to such an integrated model. The approach (a general framework) is outlined and several techniques to be applied are discussed. Subjective mathematical probability seems to be an appropriate technique as a basis for the model. In developing the model, special emphasis should be given to gathering the input data, which could include the use of expert panels. Promising techniques to deal with expert panels mainly originate from the area of marketing and consumer science and include conjoint analysis and the elicitation of subjective probability distributions.
In vitro estimation of rumen fermentable organic matter using enzymes
Authors: Cone J.W. , Van Gelder A.H. , Van Vuuren A.M.
Published: June 2020

The amount of rumen fermentable organic matter (FOM) can be calculated using tables, taking into account the amount of digestible organic matter, the content of fat and fermentation products, and the amount of starch and protein escaping rumen fermentation, or FOM can be calculated using in situ incubations. An in vitro method is described to predict FOM using amylase and other carbohydrate degrading enzymes. FOM estimated by the enzymic method showed a moderate correlation (Rsuperscript 2 = 0.71) with FOM estimated by the in situ method. The relationship could be improved by separating the high crude fibre samples (Rsuperscript 2 = 0.88) from the other samples (Rsuperscript 2 = 0.77). Because degradation rates with the enzymic method were high compared with the assumed rumen passage rates, it proved that FOM could be predicted with a similar accuracy (Rsuperscript 2 = 0.76 - 0.80) by the undegraded fraction after 24 h.
Aggregation of spatial units in linear programming models to explore land use options
Authors: Hijmans R.J. , Van Ittersum M.K.
Published: June 2020

Consequences of aggregating spatial units in an interactive multiple-goal linear programming (IMGLP) model are analysed for a schematized and an existing IMGLP model (GOAL) exploring land use options for the European Union. A discrimination was made between effects on objective functions for the system as a whole, and effects on related optimum land use allocation within the system. In GOAL, effects on land use allocation are more important than effects on the value of objective functions. Several rules or factors were identified that determine the effect of aggregation, among which the degree in curvilinearity in input-output relations and the method of aggregation are important ones. However, because of complicated interacting effects, the aggregation error is difficult to predict. Therefore, in land use studies using IMGLP it is important to first optimize the linear programming model at the non-aggregated level and then aggregate to the appropriate policy level. If aggregation is inevitable because LP models become too big, aggregation according to agro-ecological criteria, i.e., aggregation of units with similar output-input ratios and constraints, results in the smallest errors.
Effects of nutrient (NPK) supply on faba bean response to elevated atmospheric CO2
Authors: Wolf J.
Published: June 2020

In greenhouse pot experiments, Vicia faba cv. Minica was grown at ambient (315 ppm) or increased CO2 concentrations (695 ppm) with sufficient or 90 or 70% of required N, P and K. Doubling of atmospheric CO2 resulted in a >100% increase in total yield. This CO2 effect disappeared rapidly with increasing N, P or K shortage. Doubling of atmospheric CO2 resulted in no change in minimum N concentration and no change or a slight decrease in minimum P concentration in crop residues.
Scenarios of technical and institutional change in Dutch dairy farming
Authors: Berentsen P.B.M. , Giesen G.W.J. , Renkema J.A.
Published: June 2020

Scenario analysis was used to assess consistent sets of future circumstances in Dutch dairy farming. The fields of interest were technical and institutional change. Technical change included improvement in fodder and milk production. Institutional change included changes in environmental policy and in market and price policy. All key factors were historically analysed and forecasts were made for the year 2005 which were grouped into 4 scenarios. The scenarios were governed by environmental policy and the Common Agricultural Policy (CAP). Moderate and severe variants were distinguished for environmental policy; and for the CAP, price support and 2-price variants were identified.
Molluscicidal seed treatment of barley, wheat and perennial ryegrass to control the field slug (Deroceras reticulatum)
Authors: Ester A. , Nijenstein J.H.
Published: June 2020

The effects on the field slug (Deroceras reticulatum) of treating seeds of barley, wheat and perennial ryegrass (Lolium perenne) were investigated in laboratory experiments. Barley seeds were treated with metaldehyde and methiocarb, wheat seeds with metaldehyde, methiocarb, neem oil (azadirachtin) and saponins, and perennial ryegrass seeds with metaldehyde, methiocarb and thiocyclam hydrogen oxalate. These compounds were tested at several rates. Metaldehyde was the most effective treatment in preventing slug damage to the seeds and seedlings. The level of protection against slugs at 0.8 g a.i. kg-1 barley and 1.6 g a.i. kg-1 wheat seeds was insufficient, but 1.6 g a.i. kg-1 (barley) and 3.2 g a.i. kg-1 (wheat) gave good protection for up to 10 and 6 days, respectively, after sowing. Metaldehyde at 160 g a.i. kg1 perennial ryegrass seed also gave sufficient protection against the field slug.
Future trends in agricultural engineering
Authors: Jongebreur A.A. , Speelman L.
Published: June 2020

Beside traditional mechanical engineering, other engineering branches such as electronics, control engineering and physics play their specific role within the agricultural engineering field. Agricultural engineering has affected and stimulated major changes in agriculture. In the last decades agricultural engineering has also focused on environmental aspects. Nowadays knowledge and expertise generated in several agricultural and environmental engineering fields must be integrated with expertise of biological and socio-economic sciences. In the evolution towards sustainable agricultural systems important contributions can be made. The re-design of production systems and their technology can help to achieve ecologically sound and economically viable agriculture and its acceptance in the community. Mechanization and automation, structures and environment, labour and management, and energy and water are discussed.
Computational Fluid Dynamics (CFD) as a tool for the analysis of ventilation and indoor microclimate in agricultural buildings
Authors: Mistriotis A. , De Jong T. , Wagemans M.J.M. , Bot G.P.A.
Published: June 2020

The basic concepts of CFD are presented in relation to applications in modelling the ventilation process and the resulting indoor climate of agricultural buildings. The validity and the advantages of this numerical technique are presented using 3 examples. Firstly the pressure coefficients along the roof of a 7-span Venlo-type greenhouse were calculated and compared with the corresponding experimental values. Next, the ventilation process in a single-span greenhouse was investigated and the results were compared to laboratory experiments. Finally, the use of CFD as a design tool for more efficient ventilation systems was demonstrated for the case of a broiler house.
Economic and environmental consequences of technical and institutional change in Dutch dairy farming
Authors: Berentsen P.B.M. , Giesen G.W.J. , Renkema J.A.
Published: June 2020

A linear programming model of a dairy farm was used to explore the future for different types of Dutch dairy farms under different scenarios. The scenarios are consistent sets of changing factors that are considered external at farm level. The factors included are technical, such as efficiency of milk production and feed production, or institutional, such as national environmental legislation and EU market and price policy. Income and nutrient losses for farms differing in intensity and size are generated for the base year 1992 and for the year 2005. The results show that technical change up to the year 2005 has a positive influence on labour income as well as on nutrient losses. The increase of labour income is higher for farms with a higher total milk production in the basis situation. The influence of environmental policy on labour income and environmental results is bigger for farms with a higher intensity, as these farms have to take more measures to comply with governmental policy. Replacement of the price support policy for milk by a 2-price system with a high price for a restricted amount of milk and a low price for an unrestricted amount of milk has negative consequences for labour income, especially for intensive farms.
A farm economic module for tactical decisions on sugar beet area
Authors: Smit A.B. , Van Niejenhuis J.H. , Renkema J.A.
Published: June 2020

For decisions at operational level in sugarbeet growing (for example on plant density, nitrogen fertilizer rate and harvest date), returns above allocated variable costs can be used as a criterion for comparing the economics of different options. For (tactical) decisions on sugarbeet area, the sugarbeet grower has to take into account the opportunity costs of labour and equipment. The paper's calculations are based on the assumption that these can be reflected by the respective allocated fixed costs. Using Dutch farm data for the period 1991-93, a method of allocating fixed costs to crops in the cropping plan is described and included in PIEteR, a bio-economic model for sugarbeet growing. Seed and ware potato and sugarbeet had the highest returns above allocated variable costs, but when allocated fixed costs were also taken into account, sugarbeet appeared to be more profitable than seed potato. When sugar quota were included in the calculations, the returns above allocated variable and fixed costs decreased with sugar yields beyond quota level, because prices of C-beets are lower than those of quota-beets. Growing C-sugar beet was not attractive; wheat growing was more profitable. However, the estimated area required to grow the exact amount of quota-sugar was uncertain with a standard deviation of +or- 10%.
GIS and multivariate analysis of farmer's spatial crop decision behaviour
Authors: Lawas M.C.M. , Luning H.A.
Published: June 2020

Among farmers, differences in decisions about what crops to grow can be attributed to the differences in resources, levels of knowledge, environment, approach in confronting uncertainty, and other factors. In this paper, the spatial dimension of farmer's crop decision behaviour is studied by analysing the factors they considered important when choosing crops to cultivate. A total of 131 fields were randomly selected from within seven land management units in Buguias municipality, northern Luzon, Philippines, and data from their farmer-owners [number not given, year of survey not given] was collected by interview. The important factors identified were grouped into few components applying the principal component analysis (PCA). The result of the analysis is linked with a geographic information system (GIS) to present farmer's crop decision behaviour, e.g. on a map. The aims are to facilitate better understanding of such behaviour, make it more accessible and manipulable in a computer-based information system. The findings show that these objectives are achieved.
Root, soil water and nitrogen dynamics in a catch crop - soil system in the Wageningen Rhizolab
Authors: Van Dam A.M. , Leffelaar P.A.
Published: June 2020

Catch crops (winter rye [Secale cereale] and fodder radish [Raphanus sativus]) were grown on lysimeters with rhizotron facilities in Wageningen, Netherlands, from September-March (1993-94) and August-March (1994-95) in order to study root growth and water and nitrogen dynamics under different regimes of irrigation and N supply. Catch crops took up 20-30 g N/msuperscript 2, of which 37-48% was present in dead leaves in March. Rooting depth increased by 2.6 cm/day for both species at the start of the growing season. Catch cropping reduced the NO-3-N concentration in the soil considerably, initially in the top layers and then further down the soil profile. The reduction in total leached N was similar to the total crop N uptake. Nitrate-N concentrations in leached water were reduced by 49-85 mg/litre (62-99%), depending upon N availability and irrigation. Due to catch cropping the NO-3-N concentration in the percolate decreased with increasing irrigation (or precipitation), whereas the amount of N leached increased with irrigation. Evapotranspiration from a catch cropped soil was close to the potential evapotranspiration under optimal growth conditions.
Evaluation of the dry weight rank method for botanical analysis of grassland by means of simulation
Authors: Neuteboom J.H. , Lantinga E.A. , Struik P.C.
Published: June 2020

With the Dry Weight Rank (DWR) method of 't Mannetje and Haydock [see Journal of British Grassland Society (1963) 18, 268-275] for botanical analysis in pastures, the dry weight proportions of species are estimated from their first, second and third ranks in dry weight in single quadrats. The yield correction of Haydock and Shaw [see Australian Journal of Experimental Agriculture and Animal Husbandry (1975) 15, 663-670] is used additionally to solve the problem of the respective under- and overestimates of the dry weight proportions of high and low yielding species when these grow in patches. In this paper the DWR method is evaluated by means of computer simulation. Main element of the simulation model is a computer sampling program with which a fictitious vegetation can be sampled with a circular quadrat. The output shows that the DWR method works well using relatively small sampling quadrats with, on average, only a few plants per quadrat, irrespective of the horizontal vegetation structure. In vegetations where species grow patchwise, satisfactory results are also obtained using large quadrats with much more plants (i.e. tens) per quadrat. The reason is that in these cases also minor species can compete successfully for first, second and third ranks. However, it appeared that only a certain degree of patchiness is necessary, and with the usually applied quadrat sizes up to 25 dmsuperscript 2, probably in most vegetations this condition is fulfilled. Care should be taken in applying the DWR method for estimating species composition in recently sown grasslands where species usually occur more or less at random. In those cases, in principle a very small sampling quadrat (smaller than 1 dmsuperscript 2) could be used. However, this has practical limitations since the quadrat size should not be too small for realistic yield estimations, needed for the Haydock & Shaw yield correction. The simulations revealed that one condition (i.e., that the sampling quadrat should be at least as large that it usually contains three or more species) is not necessary because of the almost always perfect functioning of the correction for missing ranks. Generally speaking, a sampling quadrat should be chosen not larger than is strictly necessary from the viewpoint of horizontal vegetation structure and from the viewpoint of realistic yield estimations. Multipliers calculated from simulation data could satisfactorily mimic the original multipliers of DWR given by 't Mannetje & Haydock. It is postulated that the DWR method is well suited for studying vegetation changes in old, floristically diverse grasslands with dominant species often in moderate dry weight proportions and species usually growing in patches.
Spatial and temporal dynamics of water in the root environment of potted plants on a flooded bench fertigation system
Authors: Otten W. , Raats P.A.C. , Baas R. , Challa H. , Kabat P.
Published: June 2020

The relationship between evapotranspiration of potted Ficus benjamina plants on a flooded bench fertigation system and the distribution of water in the root zone was studied in detail for a range of fertigation schedules. The physical characteristics of the peat-based potting medium were described by models commonly used in soil physics. The functioning of the substrate in practical situations was greatly affected by hysteresis in the water retention characteristic. Daily evapotranspiration of Ficus benjamina plants ranged from 0.4 to 4.1 kg/msuperscript 2 per day, of which 19-41% was lost by evaporation. Water uptake by plant roots resulted in near hydrostatic equilibrium conditions as long as the volumetric water content was above 0.22. Lower average water contents resulted in locally drier conditions in the root environment. The absorption of water during irrigation depended on the soil physical conditions and increased with decreasing volumetric water content before flooding. The majority of the water absorption occurred within the first minutes, making frequent fertigation more effective than increasing the duration. Actual buffer capacity of the potting medium was defined and by combining measured absorption during flooding with data on evapotranspiration, the derivation of minimum requirements of the fertigation schedule is demonstrated.