bluuebunny/crossref_metadata_2025 huggingface dataset:
Degradation of nitrate by enterobacteria during silage fermentation of grass.
Authors: Spoelstra S.F.
Published: June 2020

Enterobacteria were isolated from grass and from grass ensiled in laboratory silos. Strains isolated from grass belonged mainly to the Erwinia herbicola group. After ensiling, the numbers of these bacteria diminished and Escherichia coli, Hafnia alvei and Klebsiella pneumoniae became the predominant bacteria in the respective experiments. Several strains, isolated either from grass or silage, were tested for their action on nitrate degradation by adding them to grass prior to ensiling. The isolates from grass did not affect nitrate degradation, whereas those from silage increased the rate of nitrate degradation and gave higher transient concn of nitrite and nitric oxide. Results showed no direct relationship between the total number of enterobacteria on grass and its ensilability. The numbers of enterobacteria on grass that developed after ensiling were 2 orders of magnitude lower than the total number of enterobacteria originally present on the grass. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Storability research with starch potato cultivars.
Authors: Wustman R. , Hak P.S. , Plieger P.
Published: June 2020

Studies over 4 years with 10 commercial or commercially promising cultivars grown on peat soils in the Netherlands revealed significant differences with respect to susceptibility to damage, weight loss and starch loss during storage at 6 or 20 degrees C and development of rotting at 20 degrees C. Astarte had high weight losses, and Elkana and Prominent low losses. Astarte showed a high susceptibility to internal and external damage. Erlkana, Atrela and Prominent were highly susceptible to conversion of starch to sugar at 6 degrees C, reducing processing quality; Astarte and Promesse were much less susceptible. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Behavioural phenomena related to normal and difficult deliveries in dairy cows.
Authors: Metz J. , Metz J.H.M.
Published: June 2020

Behavioural aspects of parturition, as well as the behaviour of cows and calves in the earliest post-partum period were studied in a group of 75 Polish Black and White cows. Distinction was made between unassisted deliveries, deliveries that required a little help (traction by not more than 2 persons) and difficult deliveries, requiring veterinary help. Of the cows 14% gave birth without prior behavioural signs of an approaching delivery, 72% manifested clear signs of preparturient unrest and 70% showed outflow of allantoic fluids before the calf appeared. A large variation was seen in the timing of these preparatory phases. Prolonged unrest, a cessation of labour and no appearance of the calf's feet were the clearest signs that a difficult delivery would follow. After the appearance of the feet, only 48% of the cows were able to expell the fetus within 1 h. Spontaneous expulsion of fetal membranes occurred characteristically within 12 h after parturition. Of the cows whose deliveries were unaided or aided, 86 were in recumbent position during the final phase of expulsion of fetus. The majority (64%) of cows with difficult delivery were standing. Cows separated from their calves lie down earlier after calving than those kept with their newborn. From the latter category those after a difficult delivery spent most time licking their calves, partly in lying position. After a difficult delivery calves started their first attempts to stand later, stood later, and when kept with their mothers, suckled later, than did other calves. The behavioural differences between calves from unaided and partly aided deliveries were small. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of seasonal radiation and daylength shifts on growth and development of spray carnation. 2. Flower initiation.
Authors: Klapwijk D.
Published: June 2020

Growth and development of 32 year-round plantings of the spray carnation cv. West Pink were determined. Pinching between March and July resulted in a growth period of about 70 days between pinching and microscopically visible flower initiation. When pinching took place between August and October this period increased linearly to 180 days. When pinching took place in November or later, the growth period until flower initiation decreased with one day for every day pinching was delayed. This resulted in a microscopically visible flower initiation on 7 May in many plantings. At cellular level flower initiation would have occurred in mid-April, i.e. at a daylength of approximately 14 h. Immediately after flower initiation there was an abrupt increase in the shoot extension rate. Frequent measurement of shoot length thus offers a non-destructive method to determine flower initiation. No substantial differences were found between West Pink and the standard carnation cv. White Sim with respect to daylength effects. These results with spray carnations agree fairly well with published year-round data on the total growth period between planting or pinching and flowering of standard carnations. [For part 1 see Netherlands Journal of Agricultural Science (1987) 35 (1), 55-62.] (Abstract retrieved from CAB Abstracts by CABI’s permission)
Implications of improvements in modeling canopy photosynthesis in SUCROS (a simple and universal crop growth simulator).
Authors: Kropff M.J. , Bastiaans L. , Goudriaan J.
Published: June 2020

The behaviour of an improved version of the crop growth simulation program SUCROS was compared with the original version. The improved model had a more mechanistic way of modelling canopy photosynthesis and gave higher readings at low LAI on clear days and in autumn and winter when days were short and sun elevations were low. At low assimilation rates the older version underestimated crop production of sugarbeet by 5-25%. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of exposure to different climatic environments on some blood parameters in young growing pigs.
Authors: Verhagen J.M.F. , Kreukniet M.B. , Visser W. , Herwijnen J.R. van
Published: June 2020

Young growing pigs, liveweight 22 kg, were exposed to 4 climatic treatments during 16 days. Treatments were (1) 25 degrees C, (2) 15 degrees C, (3) fluctuating temperature over 24 h (0900-1900 h 25 degrees C, 2100-0700 h 15 degrees C) and (4) fluctuating temperature in combination with draught. In each treatment 20 group-housed pigs were used. Levels of albumin and globulins before and after exposure were measured in 6 pigs, chosen at random. Leukocytic cells were differentiated. Levels of albumin and globulins were not affected by treatments. Percentage of lymphocytes decreased and percentage of neutrophils increased after 16 days' exposure to fluctuating temperature in combination with draught. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Movement of zinc sulphate in a calcium-saturated soil: cation exchange and precipitation of gypsum.
Authors: Harmsen K.
Published: June 2020

A one-dimensional model for the movement of zinc sulphate through calcium-saturated soil is presented. Processes considered include mass flow, ion exchange, precipitation and dissolution. Precipitation occurs when the solubility product of gypsum is exceeded. In the presence of gypsum, ion exchange takes place at two separate interfaces, which move with different velocities through the soil. At the first interface precipitation of gypsum takes place in conjunction with ion exchange, and at the second interface the gypsum dissolves again and ion exchange proceeds until equilibrium is reached with the leaching solution. The composition of the transition zone between the two interfaces is calculated from the conditions of mass conservation and electroneutrality, the solubility product of gypsum and assuming a linear ion exchange equation.
It is shown that the concentration of sulphate in the transition zone is higher than in the leaching solution, due to dissolution of gypsum at the second interface. In the presence of gypsum, zinc penetrates deeper into the soil than in its absence, but the fraction of the adsorption complex saturated with zinc is smaller. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Distribution of the cumulative zinc burden upon soil around galvanized pylons supporting electricity transmission lines.
Authors: Lexmond T.M.
Published: June 2020

The use of galvanized steel in pylons supporting electricity transmission lines has caused soil contamination by zinc. The distribution of the cumulative zinc burden was evaluated from the zinc content in the top 60 cm of the soil around five pylons of two different types. An adequate description of the data was obtained with a model comprising a background value of the zinc content, a factor related to the time-integrated source strength and local variables characterizing exposure frequency and deposition rate. The exposure frequency factor was calculated as the sum of long-term directional wind frequencies over the range of azimuths over which winds move from the pylon to a given location. Deposition rate was related to distance from the pylon by an exponential decay function. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Subsistence use of fallow vegetation in the highlands of Papua New Guinea.
Authors: Louman B.T.M.
Published: June 2020

The structural and floristic composition of fallows 5-8, 8-12 and 15-20 yr old, was studied in the Wau area. Results confirmed general ideas of secondary succession and supported the theoretical model of ecologically sound land use described by Oldeman, R.A.A. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of slowly and rapidly degradable concentrate protein on a number of blood parameters in dairy cattle.
Authors: Veen W.A.G. , Bakker Y.T.
Published: June 2020

In 3 feeding trials high-yielding cows and heifers (102, 72 and 92, respectively) were given diets from week 2 of lactation containing grass silage and maize silage and concentrates with slowly or rapidly degradable protein (DP). Diets were given according to the standard or slightly above the standard for digestible crude protein and net energy for milk production. A sample of peripheral blood was taken immediately before the morning feed and at 3-4.5 h after the concentrate was given. Blood urea was higher and blood glucogenic amino acids were lower (P
Digestion of alfalfa and grass silages in sheep. 1. Rates of fermentation in and passage from the reticulorumen.
Authors: Bosch M.W. , Janssen I.M. , Bruchem J. van , Boer H. , Hof G.
Published: June 2020

Wilted lucerne and grass silages were given for 9 weeks (3 weeks adaptation, 6 weeks experimental) to mature wethers. Fractional rate of passage of particles (kp) from the reticulorumen, as determined with chromium-mordanted neutral detergent fibre (Cr-NDF), was negatively related to digestibility, but positively to feed intake. Ratio of kp to kl (liquids) decreased with higher intake of indigestible material. Models were developed to interrelate cell wall pool in the reticulorumen, passage of undegraded cell walls in the proximal duodenum, fractional rate of passage of particles, fractional rate of degradation of cell walls (kd), and the proportion of large particles (fL) within the total particle pool in the reticulorumen. Although estimates of kd and fL were not very accurate yet, differences between silages could be characterized. The kd values of cell walls in grass silages were negatively related and fL positively related to stage of maturity at harvesting. For silages with similar kd, the extent to which cell walls left the reticulorumen was higher with lucerne than with grass silage. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of lysine intake and feeding level during rearing on growth performance of laying-type pullets.
Authors: Kwakkel R.P. , Corijn P.C.M.Z. , Bruining M.
Published: June 2020

A total of 640 White Leghorn pullets were given from 1 day to 6 weeks, 7 to 15 weeks and 16 to 18 weeks old: free access to diets with digestible lysine (DL) contents 0.85, 0.67 and 0.57 or 0.67% (step-down); free access to diets with DL contents 0.65, 0.67 and 0.77 or 0.67% (step-up), or; free access with 0.85% DL, access restricted to 85% of free intake with 0.79% DL and free intake with 0.77 or 0.67% DL, respectively. Treatment did not affect weight at 18 weeks old. Total feed intake was lower (P
Population dynamics of the thrips predators Amblyseius mckenziei and Amblyseius cucumeris (Acarina: Phytoseiidae) on sweet pepper.
Authors: Ramakers P.M.J.
Published: June 2020

The population dynamics of 2 predacious phytoseiid mites as potential biological control agents against thrips were investigated on sweet peppers [Capsicum annuum] in a greenhouse in the Netherlands, where the prey was predominantly a spontaneous outbreak of Thrips tabaci. Amblyseius cucumeris [Neoseiulus cucumeris] established more easily and reached higher population densities than A. mckenziei. Mixed populations of both predators were observed for several generations, but eventually A. mckenziei was superseded by N. cucumeris. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The role of soils and land use in the greenhouse effect.
Authors: Bouwman A.F.
Published: June 2020

The global biogenic sources and sinks of the major greenhouse gases emitted by soils, CO2, CH4, N2O, NO and CO, are reviewed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Apple growing potentials in Europe. 3. Northern limits.
Authors: Kronenberg H.G.
Published: June 2020

The northern production limits were determined, on the basis of prevailing temperatures, for 4 cultivars: White Transparent (very early), Cox's Orange Pippin (mid-season), Golden Delicious (late) and Granny Smith (very late). A model was developed incorporating temperatures recorded at the northernmost fruit research station (Blangstedgard, Denmark, 55 degrees 40' N) with available data on flowering, harvesting and yields. This was later tested using temperature data from numerous sites in different countries; these are tabulated and a map shows the different limits for each cultivar. [For part 2 see Netherlands Journal of Agricultural Science (1988) 33, 45-52.] (Abstract retrieved from CAB Abstracts by CABI’s permission)
Lower nitrogen excretion in pig husbandry by feeding: current and future possibilities.
Authors: Lenis N.P.
Published: June 2020

The pollution of the environment with manure nitrogen is a major argument for improving N utilization and limiting N excretion by animals. The existing legislation covering manure application in the Netherlands is briefly reviewed. In pig nutrition, the need to match more closely the protein supply to the pig's age and physiological state is highlighted - this can result in 6% less N excretion in growing pigs and up to 24% less in breeding sows. In the long term, improving the balance of dietary protein by reducing the total protein content of feeds and supplementing the diets with synthetic amino acids is suggested. Calculations show that reducing the protein content in the diets for growing pigs by 2 percentage units would reduce N excretion by about 25%. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of cultivar mixtures on the wave velocity of expanding yellow stripe rust foci in winter wheat.
Authors: Buiel A.A.M. , Verhaar M.A. , Bosch F. van den , Hoogkamer W. , Zadoks J.C.
Published: June 2020

The wave velocity of an expanding focus of Puccinia striiformis was studied in 4 mixtures of the susceptible cv. Okapi and the resistant cv. Sarno grown in ratios of 1 : 0, 1 : 1, 1 : 2 and 1 : 4. Two methods of calculating velocity were employed: (a) the gradient method, based on the disease gradient moving away from the focus with time, and (b) the area method, calculated from the enlargement of the diseased area with time. Results revealed a logarithmic relationship between the wave velocity and the proportion of susceptible plants in the mixture. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effects of light intensity on yield components, carbohydrate economy and cell-wall constituents in spring barley (Hordeum distichum L.).
Authors: Ellen J. , Oene H. van
Published: June 2020

The effects of light intensity (129, 86 and 37 W/msuperscript 2) after spikelet initiation on development, yield and chemical composition were studied in spring barley cv. Trumpf under controlled conditions. Reducing the light intensity resulted in fewer shoots/plant, prolonged the leaf area duration, lowered the specific leaf wt and delayed shoot and ear development. The light intensity strongly influenced the number of aborted spikelets, the number of grains/ear and 1000-grain wt. During leaf, stem and ear development the content and amount of water-soluble carbohydrates (WSC) in leaves plus stems decreased. At the same time there was a strong increase in content and amount of cell-wall constituents (CWC), especially in leaves and stems. This implies that the formation of CWC requires a large consumption of WSC. Reducing the light intensity diminished the production of WSC and CWC appreciably. The percentage of WSC in stems at anthesis correlated well (r = 0.68) with the number of grains/ear at final harvest, calculated over main shoot, 1st and 2nd tillers. The high amount of WSC in the stems of the plants at the 2 highest light intensities at maturity implies an insufficient storage capacity in the grains. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Evaluation of the performance of three advisory methods for nitrogen fertilization of sugar beet and potatoes.
Authors: Neeteson J.J.
Published: June 2020

The performances of 3 different N fertilizer recommendation methods were retrospectively tested with data obtained from 150 trials with sugarbeet and 98 trials with potatoes in the Netherlands in 1973-82. The recommendations consisted of applying a fixed N rate in all situations (126 kg N/ha for sugarbeet and 286 kg N/ha for potatoes), the current Dutch method, which takes only the amount of mineral N present in the soil in early spring into account, and a refinement of the current method, which also takes soil type and recent applications of organic manures into account. On av., significantly lower amounts of fertilizer N were recommended with the current method. The difference from the other methods was on av. 25 kg N/ha for sugarbeet and 30 kg N/ha for potatoes. With the refined current method the highest crop yields were obtained but the difference from the other methods was not significant and averaged only 0.3-0.4 t/ha for sugarbeet and 0.1-0.2 t/ha for potatoes. The recovery of fertilizer N by the potato tubers was 2% higher with the current method than with the other methods. Based on these findings it is concluded that the current recommendation method is preferable to the other methods. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The relation between oestrus signs and probability of ovulation at dubious oestrus in gilts.
Authors: Boer H. , Hartog L.A. den , Boode K. , Steen H.A.M. van der , Melger W.C. , Posthumus M.A.
Published: June 2020

680 gilts were studied from 168 days of age. Urine samples were collected 10-12 days after a "dubious" 1st oestrus. Of 188 gilts showing a dubious 1st oestrus, 14 produced urine samples with a creatinine concentration of 0.25 mg/ml, 99 and 75 samples had a high and a low pregnanediol concentration resp. It was concluded that 99 (57%) of gilts had an ovulatory 1st oestrus as indicated by high urine creatinine and pregnanediol concentrations. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of long-term storage at low temperature on storage losses and field performance of seed-potato cultivars.
Authors: Buitelaar N. , Marcus R. , Wustman R.
Published: June 2020

The effects of 0, 5, 4, 3, 2 and 1 month storage at 0.5 degrees C on storage losses, field emergence and development, stem number/plant, tuber yield and size distribution of seed tubers of 12 potato cultivars were investigated. Cv. Ostara was very susceptible to chilling injury; Alpha, Bea, Draga and Jaerla were susceptible to a lesser extent. Storage losses of unaffected cultivars were low; storage losses of affected cultivars varied from 4.2% for cv. Alpha to 51.4% for cv. Ostara. Only visibly unaffected seed tubers were planted in the field. Field emergence of these was 99.8%. Five months at 0.5 degrees followed by presprouting of the seed increased stem numbers/plant and reduced total tuber yield, but decreased tuber yield in the size grade 28-35 mm. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Accelerated transformation of 1,3-dichloropropene in loamy soils.
Authors: Smelt J.H. , Teunissen W. , Crum S.J.H. , Leistra M.
Published: June 2020

Inadequate nematode control on some loamy soils after fumigation with 1,3-dichloropropene prompted further study of transformation in these soils. The rate of transformation of (Z)- and (E)-1,3-dichloropropene was measured in moist soils incubated at 15 degrees C in fumigant-tight systems. In six loamy soils, transformation was gradual and pseudo first-order during 3 to 6 days but thereafter it was very fast. At an initial content in dry soil of 62-80 mg/kg the remaining amounts were less than 0.2% of the dose after a week. The greatly accelerated transformation after a short time lag suggests that the soils contained microorganisms that can transform 1,3-dichloropropene effectively. The fast transformation was measured in soil from fields once or twice fumigated previously as well as from fields never treated. In one of these loamy soils, a fast transformation (less than 0.2% remaining after 7 days) was measured at initial contents of 3.7, 18 and 92 mg/kg. But when the initial content was 470 mg/kg, the transformation rate was markedly suppressed (half-life 33 days). In another loamy soil, which showed no accelerated transformation patterns, the pseudo half-lives substantially increased from 4.3 to 36 days when the initial content of 1,3-dichloropropene was raised from 3.7 to 470 mg/kg. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Breeding primin-free Primula obconica.
Authors: Heyting J. , Toxopeus S.J.
Published: June 2020

The progeny of reciprocal crosses established between 8 different coloured strains were screened for the presence of primin, a compound with allergenic properties. Progenies of all strains except Donkerrose produced primin (p+). Of the 5 p- progenies of this strain, 4 were of the long styled form. Intercrossing these p- plants resulted in exclusively primin-free plants, but crosses with other (p+) plants generally yielded p+ progeny. In a cross of a p- plant with cv. Stadt Zurich (p+), 33 of 100 plants were primin free. F1 and backcross analyses suggested that primin production is controlled by a single gene, although this could not always be confirmed in the F2. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Influence of feeding level on the population of C-terminal-gastrin-immunoreactive cells in the digestive tract of young Clarias gariepinus (Burchell 1822).
Authors: Boon J.H. , Rombouts J.H.W.M. , Booms G.H.R. , Machiels M.A.M.
Published: June 2020

C-terminal-gastrin-immunoreactive cells, representing cholecystokinin (CCK) cells, were predominantly found in the first flexure of the anterior part of the intestine of young African catfish (Clarias gariepinus). Gastrin-containing cells could not be identified in the stomach using the same techniques and antibodies, suggesting the presence of different C-terminus of gastrin in this species compared with higher vertebrates. The number of CCK-like cells did not change in fish fed at 9% of body weight daily (low feeding level), but in fish fed at 27% the number of CCK-cells increased from week 6 and was significantly higher than the number in fish on the low feeding level at 8 weeks old. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Crop photosynthesis, respiration and dry matter production of maize.
Authors: Louwerse W. , Sibma L. , Kleef J. van
Published: June 2020

Aboveground net photosynthesis and respiration of maize cv. LG11 was determined in the field between mid-June and end-Oct. at regular intervals (1-2 weeks) at 12.5 and 22.5 degrees C by measuring the CO2 uptake or release in mobile crop enclosures. The actual growth rate of the crop was determined from fortnightly harvests. Temp. dependence of photosynthesis was highest in the early (until mid-July) and very late (early Oct.) stages of crop growth, showing a reduction of about 50% at the higher irradiances (>400 W/msuperscript 2). In the period of major DM production (mid-July to Sep.) the reduction was only 12-15%. Assuming maintenance respiration to become constant for cobs and grain exceeding a yield of 1000 kg/ha and for stems exceeding 2500 kg/ha, the measured and calculated dark respiration at 22.5 degrees matched fairly well. At 12.5 degrees the calculation, using the same assumptions, significantly overestimated dark respiration during the first part of the growing period. The carbon balance sheet showed that from the total amount of CO2 absorbed by the crop (equivalent to 30.7 t DM/ha), 30% was lost by aboveground respiration and 50% was invested in aboveground harvestable material. The remaining 20% was assumed to be transported to plant parts below ground. Substantial losses of DM at the end of the growing season did not occur. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Ammonia volatilization from arable land after application of cattle slurry. 2. Derivation of a transfer model.
Authors: Molen J. van der , Beljaars A.C.M. , Chardon W.J. , Jury W.A. , Faassen H.G. van
Published: June 2020

A model for the transfer of ammonia from arable land to the atmosphere after surface application or incorporation of cattle slurry is presented. The model can be used to study the interactions of the chemical, physical and environmental factors influencing volatilization losses and their combined influence on NH3 volatilization under field conditions. The model employs the following flux equation: R = k (Cs-Ca) where k is a transfer function, Cs is the NH3(g) surface concentration and Ca is the atmospheric NH3(g) background concentration. The rate of volatilization R can be calculated at any moment after application, provided k, Cs and Ca are known at that moment. The model therefore basically consists of modules which yield these variables. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Modelling weed competition and yield losses to study the effect of omission of herbicides in winter wheat.
Authors: Lotz L.A.P. , Kropff M.J. , Groeneveld M.W.
Published: June 2020

Omission of application of various herbicides to winter wheat cv. Arminda, cv. Citadel, cv. Okapi, cv. Granada, cv. Sarino and cv. Tombola on clay and sandy soil in 1982-86 caused a significantly lower crop yield only when the densities of certain weed species were extremely high in spring. A dynamic model simulating the competition for light and water between broadleaved weeds and winter wheat was used to assess the observed small effects of weeds on yield in terms of the relative emergence time, physiological and morphological characteristics of weeds. Like the experiments, the simulations indicated that in the Netherlands weeds emerging in spring hardly affect crop yield. Weeds emerging in autumn, however, reduced crop yield considerably if they grew as tall as winter wheat (20% loss at a density of 100 plants/msuperscript 2). The results are discussed in relation to characteristics of crop rotation systems that include root and tuber crops. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Horizontal and vertical distribution of wind speed in a vegetation canopy.
Authors: Jacobs A.F.G. , Boxel J.H. van
Published: June 2020

Wind speed measurements within a maize row canopy were carried out to investigate the horizontal and vertical variability of the mean wind speed and its standard deviation. Attention was given to finding adequate scaling parameters of the within-canopy wind speed profiles under various atmospheric stratification states. A validation of existing model simulations was also carried out. The horizontal mean wind speed and its standard deviation can vary about 20% from its spatial mean value. During day time and night time the friction velocity appears to be a good scaling parameter. Clear nights, however, are exceptions, when the wind speed above the crop drops to a very low value. Then the free convection velocity appears to be an appropriate scaling parameter for the within-canopy processes. The canopy models of Wilson & Shaw [Journal of Applied Meteorology (1977) 16, 1197-1205] and Li et al. [Boundary-Layer Meteorology (1985) 33, 77-84] were found to simulate the spatially averaged mean wind profile within the range of the horizontal variability. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Growth analyses of tomato genotypes grown under low energy conditions.
Authors: Nieuwhof M. , Garretsen F. , Oeveren J.C. van
Published: June 2020

Growth analyses were carried out on young plants of 15 genotypes, grown initially at 19/14 degrees C day/night temperatures for an 8 h day at low light intensity and subsequently at the night temperatures of 6, 10 and 14 degrees C. Significant genotypic differences occurred for relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA) and leaf weight ratio (LWR). RGR, LAR and SLA increased and LWR decreased at higher night temperatures. A strong negative correlation was observed between NAR and LAR and NAR and SLA whilst a positive correlation was noted between LAR and SLA. Plant weight was strongly influenced by seed size. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Some problems concerning aerial photo-interpretation in soil survey.
Authors: Buringh P.
Published: June 2020

A review, with 16 references. Aerial surveys can only be used as an aid in soil mapping. Field and laboratory studies of soils cannot be dispensed with. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Optimal depth of drainage.
Authors: Wesseling J. , Van Wijk W.R.
Published: June 2020

The optimal depth of drainage for field and herbage crops in the Netherlands is discussed. On clay soils, arable crops are unlikely to suffer from water shortage when water tables are about 130 cm. below the surface. Grass crops kept short by mowing or grazing may suffer from water shortage when the water table is lower than 50 cm. below the surface.-W.J.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Some factors influencing the keeping quality of potatoes.
Authors: Schippers P.A.
Published: June 2020

Physiological and microbiological keeping quality are discussed.-D.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Thermal inactivation of weed seeds and tubers during drying of pig manure.
Authors: Bloemhard C.M.J. , Arts M.W.M.F. , Scheepens P.C. , Elema A.G.
Published: June 2020

Propagules of 7 plant species were subjected to heat treatments comparable to industrial processing. Propagules of all species, which had been preincubated 1 day in pig slurry, responded to heat treatment in an oven in the range from 50 to 104 degrees C. Brassica napus and Solanum nigrum were the most heat-sensitive species. The viability of their seeds was greatly reduced after 15 min at 50 degrees C. Seeds of Amaranthus retroflexus, B. napus, Chenopodium album and S. nigrum were inactivated after 3 min at 75 degrees C, seeds of Echinochloa crus-galli and tubers of Cyperus esculentus after 3 min at 90 degrees , whereas seeds of Abutilon theophrasti only slightly responded to 3 min at 104 degrees . Heating seeds of A. theophrasti at 104 degrees with steam resulted in much less viability than heating at the same temperature in the oven. More than 1 day preincubation in slurry positively affected thermal inactivation of E. crus-galli seeds and C. esculentus tubers at 75 degrees , but not of A. theophrasti seeds at 75, 90, and 104 degrees . (Abstract retrieved from CAB Abstracts by CABI’s permission)
Components and systems research for integrated fruit production.
Authors: Schenk A.M.E. , Wertheim S.J.
Published: June 2020

The desirability of integrated fruit production, defined as an economical way of growing fruit while providing long-term safeguards to public health and the environment, and components of such a system that are currently available in the Netherlands (biological pest control, supervised chemical control of diseases, resistant cultivars, alternatives to herbicides and to soil fumigation, replacement of plant growth regulators, novel spraying techniques and fertigation) are discussed. Results of ongoing trials with 8 cultivars of apples at Numansdorp and Zeewolde, in which the current standard method of production is being compared with 2 systems of integrated production, are also presented. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Integrated production systems for glasshouse horticulture.
Authors: Welles G.W.H.
Published: June 2020

Current glasshouse horticulture in the Netherlands is based on high inputs of energy, fertilizers and pesticides, with serious environmental effects. Consequently, it has to face a restrictive governmental policy and changing consumer attitudes towards the quality of products in relation to the production process. Integrated production systems with minimum inputs are described, e.g. efficient use of energy, nutrients and pesticides, with as a consequence, minimum emissions. These systems will be introduced after tests with prototype systems for pilot crops of major crop groups. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Integration of animal husbandry and nature conservation on grassland farms.
Authors: Hermans C. , Vereijken P.
Published: June 2020

A farming model for peat grassland has been designed as an instrument in physical planning, integrating nature conservation and animal husbandry by combining the conditions for existence of both. It includes a subdivision of the farm in production grassland and nature grassland, such as marsh marigold hayfield and blue grassland. Each type of grassland has a suitable combination of groundwater level, P- and N-controlled animal and plant production, and a regime of mowing and grazing depending on its function for flora, fauna and animal husbandry. Sixteen variants, differing in type of activity (dairy, suckler, sheep and cross-bred husbandry) and type of grassland, all single or in combination, are quantified. The initial results of modelling show that the integrated model offers various perspectives for physical planning aimed at integration of agriculture, nature and outdoor recreation. It concerns areas where production grassland has to be converted completely into nature grassland as part of the National Ecological Network, as well as areas where production grassland is partly to be maintained to serve dairy husbandry. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Field evaluation and simulation of frost tolerance in Syrian durum wheat landraces
Authors: Elings A. , Nachit M.M.
Published: June 2020

Forty-nine Syrian durum wheat landraces were sown in late Nov. 1989 at Tel Hadya, Syria (a low-yielding site) and 38 were sown in mid-Dec. at Homs (a high-yielding site) with or without N + P fertilizer. Jan. frosts caused less than 5% apparent foliar damage in any of the landraces. However, foliar damage by Mar. frosts averaged 23% (range 3-65%). Late frost tolerance of foliage appeared to be related to minimum winter temperatures in the regions of origin, with landraces from coastal regions showing the highest sensitivity. Fertilizer did not significantly affect foliar damage. In simulation studies based on observed foliar damage rates at Tel Hadya due to Mar. frosts, foliar damage alone did not decrease grain yield but decreased straw yield. Additional floret damage decreased grain yield and increased straw yield.
Effects of low light intensities at night on nitrate accumulation in lettuce grown on a recirculating nutrient solution
Authors: Steingrover E.G. , Steenhuizen J.W. , Van Der Boon J.
Published: June 2020

During winter, when light intensities are low, high nitrate concentrations often occur in leafy vegetables which are undesirable from the viewpoint of public health. The effects of low lighting during the night in combination with various nutrient solutions and solution temperatures on the nitrate concentration of lettuce cv. Panvit plants grown in a nutrient film technique system were studied. The experiment showed that lettuce heads could be grown during winter under glass with a nitrate concentration as low as 2900 mg/kg FW, which is much lower than the maximum permissible concentration for winter-grown lettuce in the Netherlands of 4500 mg/kg. The lowest nitrate concentration, without negative effects on yield or quality, was obtained by growing the crop on recirculating nutrient solutions with an initial ammonium:nitrate ratio of 0.25, with a change to a ratio of 1.0 for the last 2 weeks. The addition of chloride did not affect the nitrate concentration. Raising the temperature of the nutrient solution at night from 6 to 10 degrees C in combination with a minimum air temperature of 6 degrees stimulated growth, but also increased the lettuce nitrate concentration by an average of 360 mg/kg. Supplying light of a low intensity at a photon flux density of 27 micro mol m-2s-1 (400-700 nm) at night for up to 8 nights before harvest did not further reduce the nitrate concentration on a FW basis because the dry matter percentage increased.
Response of a Scots pine (Pinus sylvestris) stand to application of phosphorus, potassium, magnesium and lime. 2. Soil solution composition
Authors: Arnold G. , Sweers I.L. , Van Diest A.
Published: June 2020

In 1985-88, a 25-yr-old Scots pine forest in Netherlands was limed (5 levels) and fertilized with P, K and Mg in a factorial design. This paper discusses the influence of P, K and Mg addition (as one treatment) and liming, on solute concentrations at depths of 30 cm, i.e. in the root zone (monitored September 1989 - April 1992) and 100-150 cm, i.e. below the root zone (April 1991). Liming increased NO3 concentrations at both depths. At 30 cm this effect of liming gradually vanished during the study period, concurrently with declining soil solution pH, while an increasing effect of PKMg on NO3 developed. Probably it took several years for nitrifying microflora to adapt to improved nutrient availability, while the effect of liming was instantaneous. These data show that besides liming, fertilization may increase NO3 leaching. NH4 was not affected by any treatment. Applied K and Mg compounds were easily soluble, and their soil solution concentrations were increased at both depths in PKMg-amended plots. Probably slow-release fertilizers would allow for a more efficient incorporation of K and Mg into the system's biomass. Reducing effects of liming on soluble Al were weak (30 cm) or absent (100-150 cm). Al at 30 cm did not reach concentrations known to be harmful to Scots pine, but Ca:Al ratios were critical in unlimed plots. No evidence was found for enhanced cation leaching caused by increased formation of nitric acid in limed plots.
The use of models in the analysis and management of aquatic and terrestrial animal production systems
Authors: Machiels M.A.M. , Udo H.J.M. , Van Densen W.L.T.
Published: June 2020

Modelling of animal production systems as a whole is mainly used for extensively managed systems, such as fishing and hunting natural animal populations. This type of modelling is widely used in fisheries management, but has as yet found limited application in the modelling of extensive cultivation practices. This paper provides a systematic overview of the types of models in use for animal production systems; these models differ in their control over production factors. The state of the art with respect to modelling subsystems is also sketched. Special attention is paid to the modelling and prediction of the environmental load caused by the output of present systems and to the search for alternative management strategies following this whole system approach
Physiological determinants to optimize metabolic utilization of dietary amino acids for animal protein production
Authors: Schreurs V.V.A.M. , Ten Doeschate R.A.H.M. , Boekholt H.A. , Koopmanschap R.E.
Published: June 2020

Dietary amino acids are distributed between different metabolic pathways depending on availability, physiological priority and metabolic capacity. Metabolic utilization of dietary amino acids for animal protein production can be optimized by making proper use of physiological determinants. This entails the development of so-called 'physiological feeding strategies'. An overview of recent achievements is presented.
The prediction of forage maize digestibility by near infrared reflection spectroscopy
Authors: De Boever J.L. , Van Waes J. , Cottyn B.G. , Boucque C.V.
Published: June 2020

The potential of near infrared reflectance spectroscopy (NIRS) to predict organic matter digestibility (OMD) of fresh forage maize was examined. Cellulose digestibility, corrected to in vivo level, served as a reference method. Calibration was based on 261 samples, varying in OMD from 68.0 to 80.3% and validation occurred in 58 samples (71.7-75.9% OMD). With a scanning IA-500 monochromator the best equation, based on the second derivative of the reflected energy at wavelengths 1620 and 1664 nm, had a standard error of prediction (SEP) of 0.65%. The repeatability of the prediction amounted to 0.49% and was smaller than that of the reference analysis. The best equation, developed for a simulation of an IA-450 filter-apparatus, had a SEP of 0.74%. Cross-validation on the calibration set showed the validity of the calibrations for a wide range of digestibility. NIRS-predicted OMD was highly correlated with the reference OMD, whereas calculated OMD, based on constant digestion coefficients for the ears and stalk + leaves, did not show any relationship.
USTED: a methodology for a quantitative analysis of land use scenarios
Authors: Stoorvogel J.J. , Schipper R.A. , Jansen D.M.
Published: June 2020

Scenarios are a useful tool to study the effects of changes in the socio-economic and/or biophysical environment on agricultural land use. For the analysis of these scenarios an operational methodology, USTED, has been developed. The methodology is based on a linear programming model in combination with GIS, crop growth simulation models, and expert systems. The data requirements include quantitative descriptions of land use systems and technologies, attribute data on such features as prices and chemical compositions, and georeferenced data on farms and soils. Sustainability is incorporated in the methodology by a limited number of quantified sustainability parameters. The linear programming model analyses, on the basis of different farm types, the effect of different scenarios on land use. Customized computer software (MODUS) is used to integrate the different models. The methodology is illustrated with a case study for the Neguev settlement in the Atlantic Zone of Costa Rica.
A static, descriptive approach to quantify land use systems
Authors: Jansen D.M. , Schipper R.A.
Published: June 2020

Quantitative tools for analysis and planning of land use require descriptions of land use systems, for example to use in optimization models. A static, descriptive formulation of land use systems, called Land Use Systems at a defined Technology (LUSTs), is discussed, that describes quantified operation sequences. Attributes, such as prices and nutrient contents, do not form part of these LUSTs, but are described separately, thus allowing for separation of technical options from socioeconomic limitations. Examples are given for the Atlantic Zone of Costa Rica. Advantages of and limitations to the LUST approach are discussed.
Sub-regional linear programming models in land use analysis: a case study of the Neguev settlement, Costa Rica
Authors: Schipper R.A. , Jansen D.M. , Stoorvogel J.J.
Published: June 2020

The paper deals with linear programming as a tool for land use analysis at the sub-regional level. A linear programming model of a case study area, the Neguev settlement in the Atlantic zone of Costa Rica, is presented. The matrix of the model includes five submatrices each encompassing a different farm type. The farm types are distinguished on the basis of land-labour ratios, considering farm size and three different soil types, and assuming a fixed availability of household labour. Land use activities are defined as a combination of a land unit (three soil types, with or without forest cover) and land type (cassava, logged forest, maize, palm heart, pasture with cattle, pineapple, plantain and tree plantain). These represent land use systems with fixed input-output coefficients. Two indicators for sustainability are taken into account: soil nutrient depletion and biocide use. These are built into the model via constraints, marking upper limits to the use of renewable resources and to the waste flow into the environment. The linear programming model forms part of the USTED (Uso Sostenible de Tierras En el Desarrollo) methodology for the analysis and planning of sustainable land use. Several land use scenarios are analysed to assess whether the income of all farms in the Neguev can increase through an improved, and sustainable, land use. First, a base scenario is calculated to serve as a reference for assessing the impact of policy measures. A striking feature of the base scenario is the large area with palm heart in comparison to the actual area. Sustainability-related policy measures studied are increasing biocide prices, and quantitative restrictions on biocide use and soil nutrient losses. Doubling the biocide price hardly affects its use, while a quantitative restriction on the use of biocides per ha of 50% in comparison to the base scenario use, reduces average incomes by less than 1%. A similar conclusion applies to soil nutrient depletion. Restricted to 'critical nutrient losses' per year over a ten year period, specified per land unit per farm type, average incomes are reduced by less than 3%. Other scenarios concern the impact of decreasing palm heart prices, as a consequence of increased supply, the influence of increasing wages and the role of the discount rate.
Effects of nitrogen on development and growth of the leaves of vegetables. 3. Appearance and expansion growth of leaves of spinach
Authors: Biemond H.
Published: June 2020

In a series of greenhouse and field trials, spinach cv. Trias plants were supplied with different amounts of N fertilizer in various split applications. Rates of leaf emergence and expansion were recorded, as well as final leaf size. The rate of leaf appearance varied between 0.16 and 0.57/day across experiments, but was hardly affected by N treatment. The rate of leaf expansion and mature leaf area increased with leaf number, reaching maximum values at leaf pair 3+4 or 5+6 and decreasing subsequently. Both characteristics were positively correlated with N supply. The duration of expansion was not influenced by N treatments and varied between 15 and 30 days in most experiments. The rate of leaf expansion was the main factor determining mature leaf size. Specific leaf area over all green leaves slowly decreased with time in most experiments and was around 300 cmsuperscript 2/g. As the differences in the number of leaves were small, the differences in total green leaf area per plant resulted from differences in the areas of individual mature leaves.