bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of ammonium nutrition on uptake and metabolism of nitrate in wheat.
Authors: Breteler A. , Smit A.L.
Published: June 2020

Wheat plants 1 month old grown in nitrate culture were exposed for 2 days to media containing 4 meq NO3 and 0-4 meq NH4/l. Where solutions contained both forms of N the uptake of NH4 exceeded that of NO3 even at the lowest NH4 level. NH4 metabolism predominated over NO3 assimilation and resulted in a higher free amino acid content, a lower carboxylate content and lower nitrate reductase activity in the tops than with NO3 alone. NH4 inhibited nitrate reductase activity whereas amino acids did not. The fall in activity of this enzyme in wheat tops caused by NH4 nutrition could not be related to the low level of tissue NH4 and it was suggested that changes in the redox situation in the cells might be involved. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Energy production and use in Dutch agriculture.
Authors: Dekkers W.A. , Lange J.M. , Wit C.T. de
Published: June 2020

This paper on food energy production and consumption illustrates to what extent agriculture in the Netherlands is dependent on fossil fuel. It can be seen from tabulated data on energy balance in agricultural systems that energy input for secondary production (e.g. meat, milk and eggs) exceeds energy output by approx. 60 X 1012 kcal/yr (70.1 vs. 10.2 X 1012 kcal/yr); this large difference, however, is mainly due to use of fodder (43 X 1012 kcal/yr) rather than use of fossil fuel. Possible ways to diminish the fossil energy input of the modern farm are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Thermal infrared pictures and the mapping of microclimate.
Authors: Derksen W.J.
Published: June 2020

Describes some field studies by the technique of air-borne infra-red line scanning (IRLS) in the Netherlands, with a theoretical introduction. The discussion covers the properties of 'warm' and 'cold' soils, the influence of vegetation cover, wind patterns, and the timing of flights. The studies include one on the location of frost hollows in sand-dune country SE of Barneveld, extensively afforested with Pinus sylvestris, where Pseudotsuga menziesii has suffered frost damage. [CF. FA 32, 6158]. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Phosphorus - a limiting factor in future food production.
Authors: Larsen S.
Published: June 2020

Extractants producing no change in the state of P in the soil (distilled water, CO2-saturated water) are not sufficiently effective to be of use in determining the release of non-labile P. Their effectiveness can be increased however by introducing an anion exchange resin charged with Cl ions into the soil-water system. The resin, apart from its ability to exchange anions, is inert, and, if applied in sufficient quantity, provides a large sink for the PO4 ions. A knowledge of the readiness with which non-labile P can be released could be helpful in periods of PO4 shortage for deciding whether PO4 need be applied. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Nutrient availability and yield formation.
Authors: Mengel K.
Published: June 2020

Available macronutrients present in the immediate vicinity of plant roots contribute only to a small degree to the total nutrient uptake of the plant. An important factor in the availability of a nutrient is therefore its mobility in the soil. The rate of translocation of a nutrient by diffusion or mass flow depends on its concentration in the soil solution, hence the nutrient level of the soil solution is of greater importance than the amounts of exchangeable or easily soluble plant nutrients in determining nutrient availability. Soil moisture and the volume of the root system also have an important effect on nutrient availability. In general, soil test methods based on the nutrient concentration of the soil solution give better correlations with plant growth than methods based on the pool of soluble and/or exchangeable nutrients. 43 references. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Structure of mushroom casing soil and its influence on yield and microflora.
Authors: Visscher H.R.
Published: June 2020

Mushroom yields were higher on more compact casing soil provided (1) a large amount of water was applied (in this case 7 litres/m2) and (2) the upper layer of the casing was ruffled or raked up before the start of the generative phase. Suppressing the diffusion of gaseous metabolites from compost to air during vegetative growth improved the yield provided a good diffusion of air is restored just prior to fructification. Many of the relevant phenomena can be attributed to CO2, but the effect of other metabolites such as acetone and ethylene on fruit body-inducing micro-organisms cannot be neglected. Microbial action appears to be involved in the stimulating effect of soya bean meal added to the mushroom compost. (Abstract retrieved from CAB Abstracts by CABI’s permission)
An explosion of leaf growth after stress conditions.
Authors: Kleinendorst A.
Published: June 2020

A root temperature of 5 deg C inhibited leaf growth of maize cv. Pioneer 395 by causing a greater retardation in cell elongation than in cell division. When this stress condition was lifted by increasing root temperature to 20 deg , temporarily accelerated leaf growth occurred. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of some salts on head weight and tipburn of lettuce and on fruit production and blossom-end rot of tomatoes.
Authors: Sonneveld C. , Ende J. Van den
Published: June 2020

In an experiment with tomatoes and lettuce grown in containers, various salts were added to the irrigation water, binary salts to give 121/2 and 25 mmol, and tertiary salts to give 81/3 and 162/3 mmol per litre water. The tomato yield was reduced by 16% at the low salt level and by 28% at the high salt level, the lettuce yield by 11 and 26%, respectively. No significant differences were found in tomato yields as a result of the various salts. Sodium bicarbonate gave a greater yield reduction in lettuce than the other salts. Calcium chloride reduced tipburn in lettuce but most other salts, in particular sodium bicarbonate, increased the disorder. Some blossom-end rot occurred in tomatoes as a result of the salt applications. Magnesium chloride resulted in more blossom-end rot than the other salts. The soil was analysed at regular intervals by means of the saturation extract. Low calcium and magnesium figures were obtained after the application of sodium bicarbonate. The uptake of nutrients in the different treatments were determined by the analysis of leaf and fruit samples. The application of the different salts was clearly reflected in the chemical composition of the crop.
ADDITIONAL ABSTRACT: In a trial with container-grown tomatoes and lettuce various salts were added to the irrigation water. These comprised NaCl, KCl, CaCl2, MgCl2, NaNO3, NaCl, Na2SO4 and NaHCO3. Binary salts were applied at 121/2 or 25 mmol and tertiary salts at 81/3 or 162/3 mmol/l water. Tomato yields were reduced by 16% at the low salt level and by 28% at the high salt level, compared with normally irrigated controls. The corresponding reductions in lettuce yields were 11 and 26%, respectively. Tomatoes showed no differences in yield in response to the various salts, but with lettuce NaHCO3 reduced yield more than the other salts. Tipburn in lettuce was reduced by adding CaCl2 but increased by most other salts, particularly NaHCO3. Treatments, particularly with MgCl2, induced some blossom-end rot in tomatoes. Nutrient uptake was determined by leaf and fruit analyses. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Transport systems in glasshouse horticulture.
Authors: Hendrix A.T.M.
Published: June 2020

Transport of glasshouse crops by conveyor belts and rail systems is discussed and examples are described of specialized forms of the 2 systems on commercial holdings producing ornamental and vegetable crops. The capital and annual costs of rail systems are relatively low. Such systems are more suited than conveyor belts to crops that need to be harvested over a period and they can be used both for harvesting and cultural operations. The advantages of the 2 systems over traditional means of transport are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The climate glasshouse at Naaldwijk.
Authors: Vooren J. van de , Koppe R.
Published: June 2020

The layout of an experimental glasshouse with 24 separate compartments is described. A process computer with peripheral units is used to control the glasshouse climate and to record the climatic data inside and outside the glasshouse. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Growth rates of tomato seedlings and seasonal radiation.
Authors: Klapwijk D. , Lint P.J.A.L. de
Published: June 2020

Over 3 years 34 sowings of tomato cv. Moneymaker were made at regular intervals and the plant fresh weight was determined once or twice a week until flowering. The daily growth percentages and the number of days required for plants to develop from 0.1 to 10 g fresh weight/plant were then related to the total radiation and average daily radiation for each of the growing periods and also to data from other trials. The length of the growing period up to attainment of 10 g fresh weight/plant was determined by the amount of irradiation in winter only; from the beginning of March until after mid-September the length of the growing period remained constant. The light efficiency and also the maximum growth rate of the plants in these trials were higher than those obtained in trials by other workers. Some batches of plants grew less rapidly than others despite adequate light, but the reasons for this are not known. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The relationship between the Aphis gossypii Glover group and cucumber mosaic virus in autumn cucumbers.
Authors: Brouwer W.M.T.J. de , Dorst H.J.M. van
Published: June 2020

The results of studies involving aphid trapping and natural virus infection of test plants showed that A. gossypii played an important part in cucumber and gherkin infection by CMV, which occurred most frequently in August. However, only a small percentage of any of the aphids found was responsible for virus transmission. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Fossil and recent soil formation in Late Pleistocene sand deposits in the eastern part of the Netherlands.
Authors: Slager S. , Jongmans A.G. , Pons L.J.
Published: June 2020

Along the Slinge Brook near Winterswijk, a profile was investigated which is assumed to consist of two aeolian deposits: Old Coversand I at the bottom and Old Coversand II at the top, between which a fluvioglacial deposit occurs, the Beuningen Complex. The profile, which now is well-drained, was poorly drained from the beginning of the Holocene up to some centuries ago. The following soil forming processes were recognized micromorphologically: decarbonation, biological activity, clay illuviation, decomposition of illuviated clay and one or two cycles of gleying. It was concluded that: (1) during the deposition of the Beuningen Complex a hydromorphic cycle may have occurred in this profile; (2) between the beginning of the Bolling interstadial and the rise of the watertable at the beginning of the Holocene, biological activity and clay illuviation occurred and possibly some decarbonation; (3) between the beginning of the Holocene and recent times a hydromorphic cycle (possibly the second) took place; (4) finally in recent times biological activity and decarbonation occur. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Nitrate poisoning in cattle. 2. Changes in nitrite in rumen fluid and methemoglobin formation in blood after high nitrate intake.
Authors: Kemp A. , Geurink J.H. , Haalstra R.T. , Malestein A.
Published: June 2020

2. Three experiments with mature dry Friesian cows lasted for up to 16 days. Nitrate was given as nitrate-rich hay or mixed with concentrates to supply from 2.4 to 16.0 g/100 kg liveweight at each meal. To test the hypothesis that methaemoglobin was formed as the result of the production of nitrite as an intermediate in the rumen, one group was given a daily supplement of KNO2, 2 to 3 g/100 kg liveweight. Blood was sampled at frequent intervals, and ruminal fluid was sampled every 15 min for short periods from cows with a recirculating sampling device. Large intakes of nitrate in either form increased nitrite in the rumen, leading to increase of methaemoglobin in the blood during the first few days, after which the high value was maintained. The high methaemoglobin value was positively correlated with the larger nitrite content in the rumen. Results are discussed in the light of conflicting reports on the tolerance of cattle to large amounts of nitrate and the importance of frequent sampling to obtain a true picture is stressed. Previous inferences regarding the ability of cattle to tolerate nitrate at up to 90 g/100 kg are considered to be mistaken.
ADDITIONAL ABSTRACT: In two experiments groups of 4 cows (415-669 kg body weight) received similar daily amounts of NO3- as either a single oral dose of KNO3 (15 g/100 kg) or a single feed of nitrate rich hay (12.4-15.4 g NO3-/100 kg) for 18 days. In a third experiment 6 cows received 2 or 3 g/100 kg of NO3- as a single oral dose of KNO2 for 6 days. Nitrate, nitrite and ammonia were measured in rumen sample and haemoglobin and methaemoglobin were measured in blood. The daily supply of equal doses of nitrate to cows, as hay with a high nitrate content or as potassium nitrate, induced higher nitrite contents in the rumen fluid and a higher percentage of methaemoglobin in the blood during the first days, after which they remained on this higher level. These increases were probably due to a change in the activity of the reducing micro-organisms in the rumen. The changes also partly explain the controversial data in the literature on the acceptable dosages of nitrate to be supplied to ruminants. This may have led to the mis-interpretation that ruminants should tolerate daily intakes up to 90 g of NO3- per 100 g body weight. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Induction of male sterility in lettuce (Lactuca sativa L.) with GA3; influence of temperature and GA3 concentration.
Authors: Eenink A.H. , Vereyken A.L.J.
Published: June 2020

During 1976, L. sativa 'Suzan' plants were grown in the glasshouse at constant temperatures of 17, 20 and 23 deg C, or with day and night temperatures varying between 25 and 15 deg C. Plants with flower buds 1-3 mm in length were sprayed with seven GA3 concentrations (0-400 mg/kg H2O). Male-sterile and fertile flowers were assessed visually, and then pollinated by the anthocyanin-containing cultivar Valore. The induction of male sterility was most successful at varying day/night temperatures, and the optimum GA3 concentrations were 50 mg at 17 and 20 deg C, 100-200 mg at 23 deg C and 200 mg/kg at varying day/night temperatures. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of relative humidity on fruit set and seed set in pepper (Capsicum annuum L.).
Authors: Baer J. , Smeets L.
Published: June 2020

During 1976, plants of the sweet-pepper variety Verbeterde Glas [Improved Glass] were placed in growth rooms at 55, 80 or 95% relative humidity, at the onset of flowering. The flowers were artificially pollinated until flower drop, and the plants were moved to the glasshouse for the fruit-ripening period. Fruit set was not influenced by relative humidity, but seed set increased with increasing humidity. Time from pollination to harvest was significantly shorter at 95% relative humidity. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Differences in grain growth, crop photosynthesis and distribution of assimilates between a semi-dwarf and a standard cultivar of winter wheat.
Authors: Spiertz J.H.J. , Haar H. van de
Published: June 2020

The crop performance of semi-dwarf wheat cv. (Maris Hobbit) was compared with a standard-ht. cv. (Lely) at various levels of N supply. The grain yields of Maris Hobbit were considerably higher due to a higher number of grains and a heavier grain wt. Owing to the higher grain yield and a lower stem wt. the harvest index of Maris Hobbit was higher than that of Lely (0.47 and 0.40, resp.). The content of water-soluble carbohydrates in the stems of both cv. appeared to be very high until 3 wk after anthesis, despite the occurrence of low light intensities. Lely used more assimilates for structural stem material than did Maris Hobbit. Quantity and date of N application greatly affected grain number, but affected grain wt. to a lesser extent. Thus within each cv. grain number/m2 was the main determinant of grain yield. Late N dressings promoted photosynthetic production, grain wt. and CP content of the grain. The low CP contents of the grain were attributed to the low temp. during the grain-filling period. The distribution of N within the plant was only slightly influenced by N dressings and cv. differences. N harvest index ranged from 0.74 to 0.79. Grain N was derived from the vegetative organs (63-94%) and from uptake after anthesis (6-37%). The importance of carbohydrate and N economy for grain yield are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Ridge quality and potato growth.
Authors: Kouwenhoven J.K.
Published: June 2020

Field and soil-bin experiments carried out for 10 yr indicate that potato growth can be considerably influenced by ridge quality, probably mainly by way of soil temp., soil m.c. and soil covering on the tubers. Under Netherlands conditions an opt.-quality ridge contains about 600 cm2 of loose soil in cross-section, has only a slightly flattened or a rounded top, has fine tilth (mean weighed diam. less than or equal to 8 mm and no clods >40 mm) and is situated on a medium-textured soil. Elsewhere, the opt. ridge, depending on climatic conditions, the occurrence of clods and stones and the predisposition for capping of the soil, can be deduced from the relationships discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Growth and yield of seed potatoes after application of gibberellic acid to the tubers before planting.
Authors: Marinus J. , Bodlaender K.B.A.
Published: June 2020

The influence of GA on growth and yield of potato seed tubers (size 28-45 mm) was studied in field experiments on sandy soil in the late cv. Alpha. Different GA conc. were applied to seed tubers with or without sprouts by both dipping and spraying. The main purpose was to find a more suitable method of preparing seed tubers than the laborious presprouting in light method. This other method would allow mechanical planting, should not be laborious and should give a high yield of seed tubers. The application of GA accelerated emergence. GA also significantly increased the yield of the seed tuber fraction, probably by increasing the number of stems and thus the number of tubers/plant. GA accelerated tuberization, decreased the total tuber yields in one experiment, whereas in the other experiment an increase occurred. The best results were obtained if sprouted tubers were treated and under favourable growing conditions. Spraying was equally effective as dipping also in the 'spraying just before planting' treatment after heat shock. This means that application during mechanical planting seems to be possible, on the understanding that the GA conc. is not too high to prevent the occurrence of phytotoxic effects (45 mg GA/l caused small leaflets with yellow discolouration). The application of GA to seed tubers seems to be attractive especially in slowly emerging cv. or in cv. with a high proportion of large tubers. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Calculation of daily totals of the gross CO2 assimilation of leaf canopies.
Authors: Goudriaan J. , Laar H.H. van
Published: June 2020

Daily totals of gross CO2 assimilation of leaf canopies have been calculated, based on photosynthesis-light response curves of individual leaves, and on a set of standard conditions. This work is partly a revision of that by de Wit [see FCA 19, 515 or HbA 36, 357]. It is extended for a range of saturation levels of leaf photosynthesis. The influence of leaf angle distribution is small. A set of descriptive equations is developed that gives an adequate description of the daily totals of gross CO2 assimilation, both of a closed and of a non-closed surface. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Competition between Hordeum vulgare L. and Chenopodium album L. with different dates of emergence of Chenopodium album.
Authors: Elberse W.T. , Kruyf H.N. de
Published: June 2020

Under controlled conditions, competition experiments were carried out with (a) spring barley and (b) C. album; this experiment was also simulated with a computer programme written in CSMP (Continuous System Modeling Program) on the basis of a model. When (b) was sown 7 days earlier, it could not compete with (a), but when this period was 21 and 31 days, (a) could no longer compete with (b). This result was hardly influenced by the applied densities of (b). Correspondence between the simulated and observed yields was rather poor initially, but could be considerably improved by correcting the model with the length factor. For this, the observed difference in length growth between the 2 spp. was included in the model. Based on the simulation results it could be concluded that light interception is probably the most important competition factor between the 2 spp. Simulating a series of 7, 21 and 31 days earlier germination for (b) showed that the critical period in which (b) can just maintain itself in a mixture with (a) is c. 15 days. Attention is called to the fact that the result of a competition experiment carried out under controlled conditions in a climate room cannot be used without comment for predicting a value under field conditions. (Abstract retrieved from CAB Abstracts by CABI’s permission)
A tentative approach to the molecular structure of humic acids: the spectral evidence for a derivation of humic acids from plant-borne esters. 1. The electron paramagnetic resonance (EPR) spectra.
Authors: Minderman G.
Published: June 2020

It is suggested, from the evidence of EPR spectra, that humic acids are heterogeneous polymers of mixed esters derived from tannins. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Apple growing potentials in Europe. 1. The fulfilment of the cold requirement of the apple tree.
Authors: Kronenberg H.G.
Published: June 2020

Data from over 600 weather stations in Europe were used to calculate the number of hours with temperatures below 7 deg C. Lists are given of 12 places in southern Europe in which the number of hours below 7 deg is less than 1000, and of 119 places in which 1000 h below 7 deg (the minimum cold requirement of apple trees) is reached, with dates. It is concluded that most apple cvs would be unsuitable for growing south of a line dividing the zones. North of that line the dates on which the cold requirements were reached varied between 17 November and 12 March. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of frequency of feeding and dietary treatment on metabolism, performance and carcass characteristics of swine.
Authors: Kempen G.J.M. van , Boer H. , Poel A.F.B. van der , Poppel F.J.J. van
Published: June 2020

In a 3 X 2 factorial design of experiment 96 growing pigs weighing 20 kg initially were given a ration based on maize which is normally used for performance testing in the Netherlands or a least-cost ration with more byproducts, twice daily at 50, once daily at 100 or once every 2 days at 200 g/kg0.75. Metabolism trials were made when the pigs reached 35, 65 and 85 kg. Blood was sampled at intervals just before feeding. Growth rate and feed efficiency were greater in pigs fed once daily than in those fed twice daily by 4 and 3% respectively. Nonesterified fatty acids in blood showed that pigs need be fed only once daily. Performance of pigs fed every 2 days was poor. The least-cost ration caused a decrease in growth rate and feed efficiency but produced thinner backfat and a greater percentage of meat. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Deficiency symptoms in cacao seedlings observed in pot experiments with the Bouma-Janssen method.
Authors: Muller A.
Published: June 2020

The Bouma-Janssen pot experiment method with a double pot technique [see HCA 45, 11] was used to demonstrate deficiency symptoms in tropical perennial crops, using cacao as the test plant, with purified sand and with a volcanic ash subsoil from Ecuador. The deficiency symptoms observed generally agreed well with those described by other workers, but they appeared at a much earlier stage than reported in experiments with conventional sand or water cultures. Sickle leaf has usually been related to Zn deficiency, but other nutrient disorders may also produce sickle leaf, as with B deficiency in the present study. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The direct and indirect effects of nitrogen shortage on photosynthesis and transpiration in maize and sunflower.
Authors: Goudriaan J. , Keulen H. van
Published: June 2020

Experiments with maize and sunflower in sol. culture were carried out to investigate the effect of N shortage in the leaf tissue on stomatal behaviour. In maize a linear relation existed between the rate of net CO2 assimilation and the conductance of water vapour, independently of the N status of the tissue. In sunflower a similar relation existed although the evidence was less conclusive. It was concluded that stomatal behaviour cannot explain differences in water-use efficiency between plants growing at different levels of N. (Abstract retrieved from CAB Abstracts by CABI’s permission)
A plant test for sufficiency of phosphorus based on the phosphorus-nitrogen interaction in sunflower nutrition.
Authors: Dijkshoorn W. , Lampe J.E.M.
Published: June 2020

Sunflower plants were alternated between complete nutrient sol. and sol. devoid of either P or N. Successive harvests of top growth were analysed for P and N fractions to follow the time course of depletion and restoration. Under adequate P the TCA-insoluble protoplasmic substance contained 25 mol P/1000 mol N. Unrestrained incorporation of P needed the presence of at least 25 mol inorganic P/1000 mol protoplasmic N; P was adequate with at least 50 mol of total P/1000 mol N converted to proteins and nucleic acids. This ratio agreed with the ratio total P:total N at which max. growth was attained in published work of both field and pot experiments, presumably because most of the N was protein bound. Because of the possibility of higher contents of TCA-soluble N, it is better that total P be related to the TCA-insoluble N. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of cutting frequency and nitrogen fertilizer rates on dry matter production, nitrogen uptake and herbage nitrate content.
Authors: Sibma L. , Alberda T.
Published: June 2020

In 3 trials with perennial ryegrass given N in the range 0-1000 kg/ha and from 3 to 28 times/yr, DM production, N uptake and NO3 content in relation to N application rates and cutting frequencies of herbage were compared. Higher N application rates increased the herbage yield more at longer growing periods than at higher cutting frequencies. N uptake was positively affected by the application rate and not or only slightly by the cutting frequency. Consistent with this, appreciably high N conc. (max. 5.4%) were found on av. in the herbage at high fertilizer N rates and frequent cutting than at lower rates and less frequent cutting (1.6%). NO3 content increased during the growing season, especially as the N application rate was higher and the growing periods longer. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Soil surface albedo and multispectral reflectance of short-wave radiation as a function of degree of soil slaking.
Authors: Heide G. van der , Koolen A.J.
Published: June 2020

The feasibility of mapping the degree of soil slaking using remote sensing on the basis of reflected solar radiation was investigated in the laboratory. Relationships between soil surface reflection and wavelength of light were plotted for a range of soil moisture contents and degrees of soil slaking. Reflection tended to increase with decreasing moisture content. Slaking had little effect on reflection at high moisture contents, but slightly increased reflection at low moisture contents. The detection of slaking by spectral analysis is not recommended, while albedo measurements may be successful under dry conditions. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Pretreatment of soil samples before NO3-N analysis.
Authors: Breimer T. , Slangen J.H.G.
Published: June 2020

Storage of sandy, loam and clay soil samples at 35 deg C or 70 deg C for 2-3 days reduced the NO3-N level in the soils. Freezing (-20 deg C), refrigeration (-4 deg C) or storage at room temperature for 2-3 days had little effect on NO3-N levels, although low or room temperature storage for 2 months increased NO3-N levels in the loam and clay soils. Freezing or refrigeration of the sandy soil for 2 months reduced NO3-N levels, while long storage at room temperature markedly increased NO3-N levels in this highly organic soil. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Nitrogen, potash and magnesium nutrition of some vegetable fruit crops under glass.
Authors: Sonneveld C. , Voogt S.J.
Published: June 2020

Different concentrations and proportions of N, K and Mg were applied as supplementary fertilizers to various crops through the irrigation system (strip spraying). Fertilizer containing 9 mol N, 4 mol K and 1.6 mol Mg/kg applied at electrical conductivities between 0.45 and 0.9 mS/cm at 25 deg C produced yields of up to 15.6, 19.7, 9.5 and 20.2 kg/m2 of tomatoes, cucumbers, sweet peppers and eggplants, respectively. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Growth of tomato plants in a split-root system as affected by various boron levels in the nutrient solution.
Authors: Cerda A. , Eysinga J.P.N.L.R. van
Published: June 2020

Growth characteristics and B translocation were investigated in tomato plants, cv. Moneydor, grown in a split-root system with different B levels. Slight B toxicity was associated with 324 mu mol B/litre in the solution, while 3240 mu mol produced clear symptoms. Exposure of both halves of the root system to 3240 mu mol B reduced the weight of tops by 45%, compared with 25% when only one half of the system was exposed. B deficiency was only observed when B was omitted from both halves of the system. In this case weight of tops, but not of roots, was reduced as was the uptake of other nutrients, especially P and K. There were no significant differences in growth between plants which received 32 mu mol B in one part of the system, and 0, 32 or 324 mu mol in the other. B contents were higher in the leaves on the side of the plant corresponding to the roots growing under high-B conditions. B content of leaves on the low-B side increased when the concentration in the high-B side was increased, indicating a lateral movement of B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Nutrient absorption by pea plants during dinitrogen fixation. 1. Comparison with nitrate nutrition.
Authors: Beusichem M.L. van
Published: June 2020

In experiments with pea cv. Rondo grown hydroponically for 6 wk with nitrate as the only N source, an acidic nutrient uptake pattern was observed. When effectively nodulated plants were fixing nitrogen, however, cation absorption exceeded anion absorption resulting in an alkaline ion uptake pattern. Maintaining ambient temp. at 13 deg C allowed for comparison of the effects of N acquisition on nutrient absorption and proton or hydroxyl/bicarbonate excretion by the roots in plants with similar DM yield and N content.The amount of excreted alkalinity or acidity for both nitrate-supplied and nitrogen-fixing plants corresponded well with the respective excess absorption of nutritive anions or cations. Physiological and agronomic consequences of the alkaline nutrient uptake pattern and acidity generation by nitrogen-fixing legumes are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Evapotranspiration.
Authors: Wijk W.R. van , Vries D.A. de.
Published: June 2020

The practical difficulties of calculating evapo-transpiration using Thornthwaite's and Penman's methods are discussed.-w.J.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The toxicity of cassava roots.
Authors: Bolhuis G.G.
Published: June 2020

A discussion, with 15 references, of the scant evidence on various factors affecting toxicity of cassava roots. Depending on the nature of the cones and age of plants, long drought periods may have unfavourable effects and deficiency of soil K seems to cause toxicity by increasing the glucoside contents of roots. The connexion between soil N and the degree of root toxicity is still lacking proof. (Abstract retrieved from CAB Abstracts by CABI’s permission)
What has the State Agricultural Experiment Station at Hoorn contributed to research into the feeding value of roughage.
Authors: Dijkstra N.D.
Published: June 2020

Work on the digestibility of fresh and dried grass, hay and silage, carried out at Hoorn (mainly in the period 1930-50) is reviewed. An account is given of attempts to formulate relationships between the contents of crude fibre and digestible organic matter in hay and grass, and between the contents of crude protein and digestible crude protein in grass (fresh and dried), hay and silage.-W.J.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
An investigation into the content of trace elements in cow livers.
Authors: Hart P.C.
Published: June 2020

Copper, zinc, manganese, molybdenum and cobalt were estimated in the livers of 62 cows. Half of the animals had been treated for 5 weeks with Vevoron, an antithyroid preparation containing methylthiouracil, for fattening. On a low-protein diet the Vevoron had increased slaughter weight and the weight of the livers. The contents in pg. per g. dry liver of Cu, Zn, Mn, Mo and Co in control animals were 116, 144, 10-9, 4-98 and 0-37. In experimental animals they were 120, 125, 8-4, 4-24 and 0-34. Zn, Mn and Mo were significantly decreased by Vevoron. Cu and Co were not significantly affected. In animals with infections except fascioliosis of the liver, and those with fascioliosis of the liver only, the only difference in content of trace elements in the livers was in Cu, which was higher in the healthy animals.-T. D. Bell. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of mechanical resistance and phosphate supply on morphology and function of maize roots.
Authors: Boone F.R. , Veen B.W.
Published: June 2020

In 3 pot experiments, maize cv. Avanti was grown on a marine sandy loam compacted to different pore vol. and supplied with different rates of P. Root wt. was not changed by different levels of mechanical resistance but root extension growth and cone resistance were curvilinearly related. At high mechanical resistance, root growth was more horizontal; vertical root growth was very limited at high cone resistances. Specific root length was also smaller, root diam. larger and fewer laterals/cm main root were developed although their av. length was not affected. The influence of mechanical resistance on root distribution and morphology reduced nutrient uptake and therefore shoot growth. With low P availability, P limited shoot growth more the higher the mechanical resistance. With sufficient P, K had the same effect. If an aboveground factor such as a low light intensity limited shoot growth, mechanical resistance had no effect on shoot growth. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Grassland productivity as affected by intensity of nitrogen fertilization in preceding years.
Authors: Prins W.H. , Neeteson J.J.
Published: June 2020

2 sown grasslands on a sandy and clay soil and an old permanent grassland on a clay soil comprising mostly perennial ryegrass were given up to 1120 kg N/ha annually and cut at various stages of development. Productivity decreased with increasing N application in the pretreatment yr, and was accompanied by a decrease in pasture quality. Annual applications of 400-480 kg N/ha gave a good balance between DM yield and sward quality. These results indicated that 1-yr field trials do not allow general conclusions as to long-term effects. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effects of use and mineral supply on the botanical composition and yield of old grassland on heavy-clay soil.
Authors: Elberse W.T. , Bergh J.P. van den , Dirven J.G.P.
Published: June 2020

In 1958-9, an area of permanent grassland was divided into plots to be used for hay production and given no fertilizer or heavily fertilized with P, K, PK, NPK or Ca and pasture plots left without fertilizer or given PK, NPK or Ca. DM production was estimated yearly and botanical composition and soil fertility analysed at regular intervals. Changes in the plots with a view to ecological indicator values and population dynamics and data on mineral uptake in the different treatments are discussed. Pasture plots not given fertilizer changed the least over the study period. DM yield, spp. diversity and changes in biomass are tabulated for each treatment and spp. present are listed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Some preliminary results of experiments with in-vitro culture of dipterocarps.
Authors: Smits W.T.M. , Struycken B.
Published: June 2020

A study was made of the influence of light, temp., growth regulators, and sugar and macrosalt concn. on the growth and morphogenesis of leaf and axis explants of young Shorea curtisii, S. obtusa and Dipterocarpus grandiflorus. Terminal and axillary buds grew best on half strength Murashige and Skoog medium. Leaf explants formed more callus on full strength medium, when containing part of the midrib and when taken from the lower half of the leaf. More than 95% of D. grandiflorus explants were infected by a fungus apparently present in the parent plant. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Relationships between temperatures and blooming dates of apple trees.
Authors: Kronenberg H.G.
Published: June 2020

Minimum winter and spring temperatures required for flowering of 8 cultivars were investigated by means of a mathematical model which used temperature data for 1927-1947 and 1971-1980 and date of blossoming (20% open flowers) data for these years. Temperature sums ( degrees C days) of temperatures above a particular base [unspecified] from 22 January to blossoming at two sites in the Netherlands are tabulated. The model was not very successful in predicting blossoming dates from temperature data. The data suggest that temperature requirements change at different stages of flower development. Higher temperatures required in February and March than April and May for bud development (predicted by the model) suggest that there is a process which prevents too early development of buds. The data also suggest that in places with a milder climate, the processes required to lift this blocking system might partially take place the previous autumn. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Functional equilibrium: sense or nonsense?
Authors: Brouwer R.
Published: June 2020

DM distribution in shoots and roots of vegetative plants depending on various environmental conditions and experimental interventions is discussed. Because of the difficulties in maintaining conditions at a sufficiently constant level for some time, functional equilibria are not likely to exist during prolonged periods of time. From the responses occurring after transferring plants including perennial ryegrass and maize from one condition to another or after disturbance of existing relationships, it is demonstrated once more that nutritional control, i.e. functional control, of distribution is still the most reasonable interpretation of the observed reaction patterns. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Inflorescence production in plants and in seed crops of Poa pratensis L. and Festuca rubra L. as affected by juvenility of tillers and tiller density.
Authors: Meijer W.J.M.
Published: June 2020

The vegetative development of seed crops of P. pratensis and red fescue and the production of inflorescences in the 1st yr may vary considerably when sown under a cover crop. Juvenile tillers were studied in pot experiments. In field experiments, low inflorescence production in late-sown P. pratensis mainly resulted from too few tillers, whereas the tillers that emerged during late autumn and winter were very fertile. In late-sown red fescue crops, low inflorescence production mainly resulted from the low fertility of late emerging tillers. In field experiments on sowing rate, density had a considerable effect on the capacity of consecutive tillers to produce inflorescences. The mortality of later appearing generations of tillers increased rapidly. Management methods to attain adequate crop development and reduce density effects are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Modelling and (adaptive) control of greenhouse climates.
Authors: Udink ten Cate A.J.
Published: June 2020

After a discussion on control of greenhouse climates, new algorithms for temperature control are presented and tested in practice. A novel approach of modelling of the climate control process is presented by using time-series analysis techniques. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Agricultural development in the Western Province of Zambia with special reference to rice cultivation.
Authors: Blom P.S.
Published: June 2020

The Western Province with its traditional subsistence agriculture is one of the less developed regions of Zambia. Climate and soil conditions and inadequate support services are the main constraints to agricultural development. Farming mainly consists of wet season food production. Cassava and millet are grown on upland soils and maize and sorghum on the lower slopes of depressions (dambos). Some farmers grow rice as a cash crop on the lower slopes, while others are engaged in extensive cattle raising. The agricultural potential of the region and the possibilities for improved family farming are insufficiently known but there are good prospects for an increase in animal and rice production. The rice area and rice yields can be increased by improved, site-specific cultivation practices and increased availability and use of draught animals. Agricultural development in the Western Province requires long-term planning, adaptive research with a farming systems approach and adequate marketing and credit facilities. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Some mechanical properties of aggregates of top soils from the IJsselmeer polders. 2. Remoulded soil aggregates and the effects of wetting and drying cycles.
Authors: Dexter A.R. , Kroesbergen B. , Kuipers H.
Published: June 2020

The mechanical properties of remoulded samples of eight soils from the IJsselmeer polders were investigated. The Atterberg (Plastic and Liquid) Limits were positively correlated with the soil clay content, but were not significantly correlated with the organic matter content. Artificial aggregates of the remoulded soil age-hardened when moist. The tensile strength of artificial aggregates was positively correlated with the soil clay content and negatively correlated with the porosity. Friability of the dried, remoulded soil was much lower than that of natural, undisturbed soil. Factors affecting the rates of wetting and drying of aggregates in the laboratory were examined in detail. Wetting resulted in mellowing (or softening) of artificial aggregates. Mellowing was investigated as a function of the potential of the source of water causing the wetting. Multiple wetting and drying cycles may result in increased mellowing or in no mellowing depending on the water potential. New terminology is introduced to facilitate discussion of these phenomena. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of the phosphorus concentration in the diet on the performance of fast-growing pigs.
Authors: Jongbloed A.W.
Published: June 2020

In 6 experiments with 359 pigs weighing 30 to 110 kg different amounts of phosphorus were added to the diet as CaHPO4 in 3 or 4 steps of 0.75 g P/kg. All diets had a Ca:P ratio of +or- 1.3:1. Optimum results were obtained by addition of 0.75 g inorganic P with digestible P 1.6 to 1.8 g/kg DM. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of energy intake during rearing on reproductive traits in gilts.
Authors: Hartog L.A. den
Published: June 2020

The effect of energy intake from 12 until 38 weeks old on reproductive performance in 538 Dutch Landrace gilts was studied. Four treatments based on different amounts of energy (about 3.0 M, 2.5 M, 2.1 M and 1.8 M; M = metabolizable energy required for maintenance) were tested. All received a similar daily amount of protein per kg bodyweight. Conception rate was lower for gilts (67 and 64%) at the 2 higher amounts of energy intake than for gilts at the 2 lower (both 76%). A significant interaction for ovulation rate was found between energy intake and oestrus number at average age of 8.5 months. Number of piglets born alive, average birthweight and homogeneity of the litter (measured as s.d. of birthweights within a litter) were not clearly affected by energy intake. The pooled regression coefficients of average birthweight on weight of sow on the day before farrowing and rate of gain during the last 100 days of pregnancy were significant (P
Digestibility of plant fractions from different genotypes and the predictability of quality of forage maize in northwest Europe.
Authors: Struik P.C.
Published: June 2020

Differences in digestibility of plant parts from 5 forage maize hybrids are described and related to the differences in whole plant digestibility of crops grown under different conditions. Plant parts differed greatly in digestibility, and the proportions of the DM of the total plant were variable due to numerous physical, chemical, biological and genetic factors. Whole-plant digestibility, however, was fairly constant and predictable. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Trees in agricultural and livestock development.
Authors: Wiersum K.F.
Published: June 2020

A review of the use of trees outside the forest in tropical farming systems: the role of trees; traditional systems of farm tree management; the scope for multipurpose (especially nitrogen-fixing) trees; wood yields from scattered or hedgerow trees and from woodlots; and development opportunities and programmes. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Towards sustained timber production from tropical rain forests in Suriname.
Authors: Boxman O. , Graaf N.R. de , Hendrison J. , Jonkers W.B.J. , Poels R.L.H. , Schmidt P. , Tjon R.L.S.
Published: June 2020

A summary account of the complementary Celos Harvesting System and Celos Silvicultural System developed by the Agricultural University of Wageningen and the Anton de Kom University of Suriname in a joint project over the last 20 yr. The harvesting system comprises: prior mapping of the trees to be selectively felled and opening up of skid trails; directional felling; winch extraction; and registration of log flow from stump to destination. This system has reduced skidding costs by 10-20% and skidding damage by 50% compared with existing unplanned operations. The silvicultural system comprises 3 treatments: refining 1-2 yr after selective logging, by climber cutting and poison-girdling of non-commercial trees (preferably