bluuebunny/crossref_metadata_2025 huggingface dataset:
The determination of cation-exchange characteristics of saline and calcareous soils.
Authors: Yaalon D.H. , Van Schuylenborgh J. , Slager S.
Published: June 2020

The soil is saturated with LiCl solution buffered at pH 8.2 with LiOAc, followed immediately by leaching with Ca(OAc)2 at pH 8.2. Na, K, Ca, Mg and Li are determined in the extracts by direct flame photometry and complexometry. The need for washing the soil is eliminated by assaying the remaining excess salts as C1. Soluble ions are determined on a separate sample. The method can be used on non-saline or CO3-free soils by adjusting the saturating and extracting solutions to pH 7. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Distribution and redistribution of dry matter in perennial fodder crops.
Authors: Sonneveld A.
Published: June 2020

A review.-R.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Programme planning; a practical example.
Authors: Forsyth H.A.
Published: June 2020

A method of programme planning, partly similar to the techniques developed by Johnson and Giaever, is used to calculate a near optimum (production) plan for a mixed farm of 12 hectares. The techniques and principles of gross margin analysis and mathematical elements of linear programming are used, and the results are compared with an optimum plan, derived by means of linear programming. This method does not provide an exact picture of enterprise relationships such as can be obtained by linear programming, but is shows which enterprises are blocking the plan and where adjustments can be made. Differences in results between near optimum and optimum plans are so small, that the method may be considered to be accurate enough for use in empirical work. R.v.H. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The tropical grey and black earths of the Accra Plains, Ghana; their environment, characteristics and air-photograph mapping.
Authors: Hagenzieker F.
Published: June 2020

Gray solonetsic and black montmorillonitic earths cover extensive areas of the Accra Plains. Similar soils occur on plains east of the river Volta. Both soils are deficient in N and P. Aerial photographs offer the possibility of recognizing principal soil groups and other features important for large-scale agricultural planning. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of temperature, light intensity and nitrate concentration on dry-matter production and chemical composition of Lolium perenne L.
Authors: Alberda T.
Published: June 2020

In this trial the nitrate concentration of the nutrient solution affected the rate of DM production only when it fell below 0.2 mM. Between 0.2 and 1.5 mM the chemical composition of the plant was altered considerably but production was not affected. The soluble carbohydrate content, which reached a very high value in the above-ground parts when the nitrate supply was low, fell as the nitrate concentration rose; the same tendency was observed in the crude-fibre content and some unidentified components, probably hemicelluloses and pentosans. The organic-N fraction increased with increasing nitrate concentration in the above range. Above 1.5 mM the effect was virtually confined to the plant nitrate concentration, and there was always a definite relationship between the nitrate content and the soluble-carbohydrate content. The optimum temp, for DM production increased with increasing light intensity.-R.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Copper metabolism in milch cows. III. Evaluation of the method for radio-measurements over the liver.
Authors: Binnerts W.T.
Published: June 2020

Cows were inoculated i/v and i/m with Cu-64 and the radioactivity of the liver was measured in vivo and P.M. The absolute and relative errors of the in vivo measurements were calculated. Studies also included the geometry of the body related to the counting system, and the position of the counter, its shielding and the value of background readings. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Some characteristics of young sediments in Lake IJssel.
Authors: Hofstee J.
Published: June 2020

Recent material was in prolonged and intensive contact with fresh lake water whereas in older sediments cation exchange was still affected slightly by the former marine medium. Under fresh lake water, adsorbed Mg, K and Na are exchanged for Ca. This may also explain the lower content of S compounds; S compounds are oxidized into SO4 in the young material, which is rich in oxygen and bacterially active, and are then removed by percolating water. Moreover fewer new insoluble compounds are formed in fresh water than in SO4-rich seawater. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Interrelation between frequency dominance and dry-weight percentages of species in grassland vegetation.
Authors: Dirven J.G.P. , Hoogers B.J. , De Vries D.M.
Published: June 2020

In botanical grassland research in the Netherlands, dry weight analysis and the combined 25 cm2 frequency and order method have mainly been applied. Since the botanical composition of many fields had been analysed by both methods, it was possible to study the interrelation between the percentages of frequency, dominance and dry weight. The results showed that the relation between dominance and percentage dry weight depended on the plant-size/ quadrat-size ratio. As this quotient becomes greater, the relation progressively approaches the 45 degrees line. In the analysis of tropical grasslands it is possible to obtain sufficiently reliable information about the quantitative ratios of the various grass species fairly rapidly by determining the dominance percentage. The relation between frequency percentage (F%) and dominance percentage (D%) is also determined by plant-size ratio and can be expressed by the general equation: D% = -m Iog10 (100-F%) + 2 m. The coefficient m is a reliable standard of the dominance tendency of the grassland species.-A.G.G.H. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Chromosome numbers in Begonia.
Authors: Legro R.A.H. , Doorenbos J.
Published: June 2020

The somatic chromosome numbers of 100 Begonia species were counted, of which 72 have been determined for the first time. Eighteen different numbers have been established, ranging between 22 and 156, fifteen of which could be fitted into a tentative scheme of five polyploid series. The most common numbers were 22 (14 species), 28 (35 species) and 56 (17 species). The species have been grouped into sections according to Irmscher. In some cases these sections appeared to have a characteristic chromosome number whereas in others, e.g. Pritzelia and Begoniastrum, a great diversity in chromosome number was encountered. [For earlier work see H.A., 39: 5182.]-Univ. Wageningen. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Water movement in layered soils-a simulation model.
Authors: Van Keulen H. , Van Beek C.G.E.M.
Published: June 2020

The simulation model is written in "continuous system modelling Program" and is applied to ploughed and unplowed soils with layers of different conductivity. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Experimental studies on seed production of tropical grasses in Kenya. 2. Tillering and heading in seed crops of eight grasses.
Authors: Boonman J.G.
Published: June 2020

Tillering in seed crops grown undisturbed for 6 months was studied over 2 years in cultivars of Setaria sphacelata, Chloris gayana, Panicum coloratum, Panicum maximum and Brachiaria ruziziensis. Tiller numbers rose to a maximum around the time of initial head emergence (5-10 heads/m2), followed by a decline and finally a levelling off. Head emergence was found to continue in some cv. for over 3 months. The weight/tiller increased at a linear rate. Tiller numbers never exceeded 1900/m2. Tillers were less numerous but were heavier in the year of sowing than in the subsequent year. Total dry weights of tillers were also highest in the first year. Seed yield was significantly correlated with degree of concentrated head emergence and percentage of heading tillers in a cultivar. It is suggested that, within cv., plants with heavier tillers may produce higher seed yields. Cv. within species can be identified according to date of initial head emergence. A type of culm branching is described in which tillers develop into flowering culms out of elevated nodes of erect parental culms. (Abstract retrieved from CAB Abstracts by CABI’s permission)
An experiment for determining the depth of penetration of various phosphates with the aid of P³².
Authors: Haasjes K.H.S. , Sissingh H.A.
Published: June 2020

In addition to investigations into the depth of penetration of radio-active phosphates in the soil, studies were also made of the assimilation by plants of P2O5 derived from radio-active phosphates. Oats, peas, maize and potatoes were grown in Mitscherlich pots containing soil to which suitable quantities of fertilizers other than phosphate were added at the date of sowing or planting. One month after sowing or planting, 3 different types of phosphatic fertilizers, superphosphates, di-calciumphosphate and tri-calciumphosphate, were applied separately to all four types of crop. Equal quantities of P2O5 were applied, in the form of phosphate, to each pot and the radio-activity of the quantity of phosphate applied to each pot was 300 p. c. Measurements of radio-activity in the plants, made 11 days after application of the phosphates, showed that rapidity of absorption of P205 is conditional upon the water-solubility of the phosphate. In all cases the most P2O5 was present in the plants where superphosphate had been applied and the least where tri-calcium phosphate had been applied. The degree of radio-acitivity (indicating the quantity of P2O5 present) of maize, pea and potato leaves of different ages is shown graphically for each phosphatic treatment. In all cases the greatest quantities of P2O5 were assimilated by the youngest leaves and the least by the oldest leaves. Measurements of the radio-activity of leaves of equal age on different stems of a single potato plant indicated that there were differences in assimilatory capacity between different stems of the same plant. It was also observed that important differences in capacity to assimilate P2O5 existed between individual plants in the same crop.-W.J.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of temperature rise on silage.
Authors: De Man J.C.
Published: June 2020

Cut and crushed grass samples were separately ensiled in preserving jars and kept either at 35 degrees C. for one week and subsequently at 20 degrees C. for 6 months or at 20 degrees C. throughout. Maintaining silage at 35 degrees C. for one week stimulated the formation of butyric acid and restricted the formation of lactic acid. In another experiment jars were held at 35 degrees C. for periods varying from 1 to 8 days. Silage deteriorated after 1 day at 35 degrees C. The deleterious effect of keeping silage at 35 degrees C. was less pronounced in the case of crushed than in the case of cut grass.-W.J.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of light intensity on some morphological and physiological aspects of the crop perennial ryegrass (Lolium perenne L. var. 'Cropper') and its effect on seed production.
Authors: Spiertz J.H.J. , Ellen J.
Published: June 2020

Perennial ryegrass cv. Cropper was given high (188), intermediate (140) or low (84 cal/cm2 day between 400-700 nm) light intensity during the period 1 Apr.-30June using supplementary lighting, normal daylight and artificial shading, respectively. Other plots were given 174, 86 and 52 cal/cm2 day during 26 Aug.-1 Oct. and 106, 43 and 26 cal/m2 day until 29 Oct., without affecting the photoperiod. Increased light intensity in autumn or spring considerably increased tillering, while shading treatments gave a decrease. Differences in tiller numbers in autumn decreased during winter and early spring. Numbers of vegetative and reproductive tillers and weight/tiller increased with increasing light intensity in spring. Seed yield was closely correlated with number of reproductive tillers and less closely with number of seeds/head. Supplementary illumination in autumn had only a small effect on number of reproductive tillers but increased number of seeds/head. Maximum LAI of the top 3 leaves, internodes and inflorescences was 13.2, 11.6 and 7.7 in the 3 treatments respectively; these values were high compared with cereals. Amounts of water-soluble carbohydrates in reproductive tillers increased exponentially until ripening and then fell sharply. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Dispersion in simulation models of population growth and salt movement in the soil.
Authors: Goudriaan J.
Published: June 2020

[113.413:116.113].The basic equations for mass transport of salt in the soil were analogous to those for development in a population. Both types of processes are modelled by compartmentalization. In such models with layers or classes an artificial dispersion is introduced with a coefficient vB/2, where v is the rate of transport or development and B the size of the compartment. Rectangular integration causes an additional dispersion with a coefficient -v2 DELTA t/2, where DELTA t is the time interval of integration. The artificial dispersion can be used to mimic natural dispersion. Methods for controlling or preventing artificial dispersion are discussed in relation to the method of integration used. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Calcium nutrition of higher plants.
Authors: Marschner H.
Published: June 2020

Despite low intra-cellular requirements for Ca in the higher plants, Ca deficiency has been recorded in agricultural and horticultural plants during recent years. Because of insufficient selective and active uptake of Ca and its slow translocation, a high Ca concentration at the root surfaces is essential. The Ca requirement also increases when the supply of other nutrients, particularly cations increases. The use of inorganic fertilizers containing Ca should therefore receive more consideration. 56 references. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Physical aspects of soil fertility - the response of roots to mechanical impedance.
Authors: Russell R.S. , Goss M.J.
Published: June 2020

Penetrability of soil by roots is reviewed. Roots of barley did not decrease in diameter in order to penetrate small pores. Where substrates were selected with pores smaller than the diameter of root axes but larger than that of laterals, axes were impeded but lateral roots proliferated, indicating that an appreciable reduction in root extension caused by mechanical stress would not necessarily reduce crop yield. Where barley root axes were forced to bend, lateral root initials typically developed on the convex side. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Climate, nitrogen and grass. 6. Comparison of yield and chemical composition of some temperate and tropical grass species grown at different temperatures.
Authors: Deinum B. , Dirven J.G.P.
Published: June 2020

For part 5 see NAR 43, 148. 6. Lolium perenne, Festuca arundinacea and 2 tropical grasses, Axonopus compressus and Brachiaria ruziziensis, were grown in pots under day/night temperatures of 19 deg /12 deg , 24 deg /18 deg , 28 deg /23 deg and 34 deg /30 deg C and regrowth was cut after 18 and 35 days. The stemmy Brachiaria was much more productive than the others which remained vegetative. The optimum production temperature was 24 deg or less for the temperate grasses but >30 deg for the others. Yield was greatest after 35 days and with high N fertilization. Lolium had the highest average content of N, soluble carbohydrates and digestibility in vitro and Brachiaria the lowest. Digestibility declined with increase in temperature and age, most for Brachiaria. These effects were caused by an increase in content of cell-wall constituents and a decrease in their digestibility. N fertilization had no effect on digestibility. Results support the hypothesis that the low digestibility of tropical grasses is mainly due to the high temperature during growth but may be improved appreciably if stem formation is suppressed.
ADDITIONAL ABSTRACT: Lolium perenne, Festuca arundinacea, Axonopus compressus and Brachiaria ruziziensis were grown in pots in a glasshouse under day/night temperatures of 19/12, 24/18, 28/23 or 34/30 deg C with intermediate or high N and regrowth was harvested after 18 and 35 days. Reproductive B. ruziziensis was much more productive than the other vegetative species. Optimum day temperature for production was 24 deg or lower for temperate grasses but >30 deg for tropical species. L. perenne had the highest contents of N and soluble carbohydrates and in vitro digestibility and B. ruziziensis the lowest, differences being smallest at the low temperature. There was a consistent decline in digestibility of all species with increase in temperature and age which was correlated with an increase in cell wall constituents but was not related to amount of N applied. [For Part 5 see HbA 43, 1557] (Abstract retrieved from CAB Abstracts by CABI’s permission)
A crop geography of late brussels sprouts.
Authors: Kronenberg H.G.
Published: June 2020

The producing areas of late brussels sprouts are restricted by the prevailing temperatures, which determine the first possible planting date, duration of the growing season and growth during this season, sprout formation and frost damage in autumn and winter. In Europe 2 partly overlapping sprout growing areas can be distinguished: a large area of medium/late sprouts in north-western Europe (growing period May/June-October) and a smaller area of late sprouts near the Atlantic Ocean in southern England and western France, and in northern Italy (July-November). Crop statistics show production in these areas. Outside Europe sprouts can be grown in parts of the USA, Canada, Japan, Australia, South Africa, New Zealand, Chile, Argentina and Paraguay. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Moisture retention and plasticity of highly calcareous soils in Egypt.
Authors: Stakman W.P. , Bishay B.G.
Published: June 2020

Particle size distribution, moisture retention curves and consistency limits were determined for six soils from northwestern Egypt. The soils contained 25-61% CaCO3 and attapulgite was the major clay mineral. In the clay and clay loam soils the CaCO3 was predominantly in the silt and clay fractions, in the sandy loam it was regularly distributed over the clay, silt and sand fractions and in the loamy sand it was mainly in the sand fraction. Decalcification shifted the particle size distribution to a coarser texture class and increased porosity and moisture content. Liquid limit and plasticity index increased with increasing clay and CaCO3 contents up to 40% clay and 35% CaCO3. The plastic limit stayed rather constant at increasing clay and CaCO3 contents. The liquid limit corresponded with suctions of pF 1.3-1.9 within the flex range from the saturated to the unsaturated condition of the pF curves. The plastic limit and the plasticity index corresponded with pF 2.1-3.0 and 2.6-3.8, respectively. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Some influences of zero-tillage on the structure and stability of a fine-textured river levee soil.
Authors: Boone F.R. , Slager S. , Miedema R. , Eleveld R.
Published: June 2020

By means of physical and micromorphological analyses the difference in soil structure caused by ploughing and 5 years zero-tillage on a fine-textured fluviatile deposit was characterized. Although bigger pores were less stable and more affected by compaction, within each pore size class stability varied widely. Zero-tillage resulted in a denser and more homogeneous soil in which small aggregates disappeared and aggregate stability increased whereas pore continuity was not improved very much. Active pseudogleying was responsible for extensive bleaching in the zero-tillage profile, caused by a periodical lack of oxygen. The earthworm population increased markedly, but most earthworms were small. The number of large worm holes decreased sharply with depth, indicating a poor environment for the deep-burrowing worms which improve vertical water transport. Temporary pool formation occurred on part of the zero-tillage plots in the autumn and winter of the last few years, and after a heavy rainstorm in June 1975, when many worms died on the zero-tillage plots. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Regulation of fat mobilization in adipose tissue of dairy cows in the period around parturition.
Authors: Metz S.H.M. , Bergh S.G. van den
Published: June 2020

Samples of subcutaneous adipose tissue were taken from Dutch Black Pied and Meuse-Rhine-Yssel cows at regular intervals from about a month before until a month after parturition. Tissue was incubated in Krebs-Ringer bicarbonate buffer with 5% bovine serum albumin for 15 min and then for experimental incubations with fresh buffer without or with bovine insulin, glucose or norepinephrine. Rates of release of free fatty acids (FFA) and glycerol from tissue of cows in early lactation were greater than those from tissue of the same cows before parturition. The increase in fat mobilization after parturition was caused by an increase in rate of lipolysis and by an almost complete disappearance of the reesterification of fatty acids in the adipose tissue. FFA in blood also increased after parturition. During the period before and after parturition norepinephrine stimulated the release of FFA and glycerol from adipose tissue. Although glucose normally inhibits fat mobilization by stimulation of the reesterification of fatty acids, this effect was not seen during the first weeks after parturition. Insulin did not influence the effects of glucose on fat mobilization. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of temperature on sex expression in onion (Allium cepa L.).
Authors: Meer Q.P. van der , Bennekom J.L. van
Published: June 2020

At the onset of bolting, eleven populations of the variety Wolska were placed in the greenhouse at constant temperatures of 14, 17, 20 or 23 deg C. The percentage of male-fertile plants increased with increasing temperature, the critical temperature appearing to be 17 deg C. The transference of plants from outside to a constant temperature of 14 deg C, three or six weeks after the initiation of bolting, showed the effect of temperature to decrease with time, suggesting that induction of male sterility occurs in the early stages of bolting. Observations on an unspecified number of A and B lines of the variety Rijnsburg at 14, 20 and 23 deg C indicated that instability of sex expression occurs only in B lines. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of temperature and light on parthenocarpy in pickling cucumbers (Cucumis sativus L.).
Authors: Ponti O.M.B. de
Published: June 2020

Parthenocarpy was influenced unfavourably by high temperatures. The effect of high day temperatures could partly be compensated by low night temperatures. A temperature regime of 23/17 deg C seemed to be optimal. The influence of daylength and light intensity are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effects of leaf removal on yield components in sunflower.
Authors: Pereira A.S.R.
Published: June 2020

In a study of the relationship between leaf apparatus and yield in sunflower, the Rumanian hybrid HS 18 and the French hybrid INRA 4701 were subjected to a variety of leaf removal treatments. These treatments differed both in the number and in the position of the leaves removed. The leaves were removed one at a time during the vegetative period in one series and all at once shortly before flowering in another. The effects of the various treatments on final plant ht., size of head, seed setting and different aspects of yield were determined. INRA 4701 was more sensitive to leaf removal in terms of plant ht. and head size, whereas seed and oil yield were affected more in HS 18. Seed setting in the centre of the inflorescence was better in INRA 4701 than in HS 18 for all treatments. Relative to the untreated controls, however, the effect of leaf removal was more injurious to seed setting in INRA 4701.
ADDITIONAL ABSTRACT: A study of the varieties HS18 and INRA4701 showed the leaf efficiency of the former to be twice that of the latter. Defoliation had a greater effect on seed yield and oil yield in HS18 and on for plant height, head diameter, grain weight and seed setting in the central area of the head in INRA4701. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effects of nitrogen on crop development and grain growth of winter wheat in relation to assimilation and utilization of assimilates and nutrients.
Authors: Spiertz J.H.J. , Ellen J.
Published: June 2020

Grain growth and yield components of winter wheat cv. Lely were studied in a field experiment in 1976 with 4 rates of N (50, 100, 100 + 50 or 100 + 100 kg N/ha). Growing conditions were characterized by a high level of solar radiation, warmth, ample nutrient supply and no damage by diseases. N raised grain number/m2 from 16 700 to 20 600 and grain yield from 640 to 821 g dry wt./m2. Grain growth duration was short, due to warmth, but the rate of the grain filling was very high (from 24.0 to 29.2 g/m2 day during the effective grain-filling period). A high grain yield was associated with a high grain N content which resulted in a grain protein yield ranging from 63.8 to 107.1 g/m2 with increased N rate from 50 to 200 kg/ha. The carbohydrate demand of the grains was provided by current photosynthesis and relocation of stem reserves. The latter was reflected in a decline of the stem wt. after the mid-kernel filling stage. N and P demands of the grains were supplied by withdrawal from the vegetative organs (leaves, stem, chaff) and to a large extent by post-floral uptake and assimilation. Under the prevailing growing conditions the grains turned out to be very strong sinks for carbohydrate, N and P as shown by the harvest indices. Additional N dressings increased the harvest indices of DN, N and P from 0.40 to 0.48, from 0.75 to 0.81 and from 0.91 to 0.93 resp. It was suggested that a more restricted vegetative crop development at high N levels and a longer duration of root activity, photosynthesis and grain growth after anthesis would considerably favour grain yield. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Computer-aided estimates of drainage charges - a Dutch case study.
Authors: Bie S.W. , Holst A.F. van , Stricker J.N.M.
Published: June 2020

When regional water management is regulated centrally on a cooperative basis, methods must be developed whereby drainage charges can be estimated from agreed and objective data. Reported here is a method to compute and map, from data on altitude, the supposed open water level after a given discharge and soil characteristics for available moisture, the charges to be levied. Independent 'maps' are compiled for each of the three attributes by computer mapping techniques. The area is split into a large number of small cells (here 12.5 m X 15.5 m), for each of which the altitude is estimated by interpolation from known spot heights. For the same cells the supposed open water levels are approximated by interpolation from a number of calculated water levels in streams and ditches. Known watershed divides are introduced as barriers to interpolation. Four soil moisture classes are generated. The three 'maps' provide for each cell the basic data required by an allocation algorithm which evaluates the value for altitude, water level and soil moisture class. For each cell the appropriate drainage charge class was determined. A payment class map is generated by the allocation and can be printed on the computer lineprinter, each class being given a distinguishing printing symbol. The method is demonstrated for a 210-ha test area under the jurisdiction of the Regional Water Board Salland. Further extension to include a cadastral map to allow automated invoicing procedures are discussed. The system is implemented on a CDC Cyber 72 computer and uses SYMAP (Harvard University, USA) as one module. (Abstract retrieved from CAB Abstracts by CABI’s permission)
A case study on the effect of soil compaction on potato growth in a loamy sand soil. 1. Physical measurements and rooting patterns.
Authors: Boone F.R. , Bouma J. , Smet L.A.H. de
Published: June 2020

An interdisciplinary field study, including consideration of soil tillage, soil physics, pedology and crop science was made to study the effect of soil compaction on potato growth in a young alluvial loamy sand soil in the very dry growing season of 1976. The treatments consisted of different degrees of compaction in or just below the arable layer and also consider the effect of irrigation. Compaction decreased soil pore vol. whereas the volumetric water content at any given pressure potential was increased or decreased depending on the degree of compaction. A high mechanical resistance encountered by the roots proved to be the primary factor affecting root elongation. Roots penetrated the compacted layers in all treatments but at very different rates. As a result the pressure potential at the rooting front was relatively low as long as roots were growing in the compacted layers. Moisture flow to the roots by capillary rise from the water table occurred during the entire growing season but varied significantly among treatments as a function of the distance above the water table and hydraulic conductivity of the various layers. Moderate compaction increased, but severe compaction decreased, the potential for capillary rise in the topsoil. The plough pan in the subsoil increased the potential for capillary rise. Critical groundwater levels at a given rooting depth were calculated for different steady upward fluxes for some of the treatments. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Investigation into plant characters affecting the competitive ability of perennial ryegrass (Lolium perenne L.).
Authors: Hofman T.B. , Ennik G.C.
Published: June 2020

In a number of pot and tray experiments in soil and in sol. culture the same clone of 6 perennial ryegrass clones tested was always the most competitive both in the vegetative phase and the reproductive phase, while another clone always showed the least competitive ability. The most competitive clone had the relatively greatest root system, the least competitive clone the relatively smallest root system. The soluble carbohydrate content in tillers and stubbles of the clones did not yield any evidence on competitive ability. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Regrowth potential of shoot and of roots of Rhodes grass (Chloris gayana Kunth) after defoliation.
Authors: Dovrat A. , Dayan E. , Keulen H. van
Published: June 2020

In field and pot trials the effect of different lengths of pre-cutting periods and of cutting intervals on regrowth of shoot and of root were studied in Rhodes grass cv. Katambora. The initial regrowth of the sward after a long (28 days) pre-cutting period was slower than after a short (7 days) pre-cutting period. The reduction of the residual LAI following the extension of the pre-cutting period was associated with reduction in the number of tillers capable of regrowth after defoliation. Root wt. decreased drastically following cutting when the initial root wt. was high (long pre-cutting period), but little when the initial root wt. was small (short pre-cutting period). The decrease in root wt. lasted c. 1 wk after which it increased at a more or less constant rate proportional to the increase of shoot wt. irrespective of the length of the pre-cutting period. The lack of the capability of tillers to regrow after cutting was closely related with developmental stage of tillers. Since tillers of subtropical and tropical grasses have a tendency for early stem elongation, it was concluded that the relatively small number of sites available for regrowth in these grasses is the major deterrent for quick shoot growth of the sward after defoliation. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Genetic differences in digestibility of forage maize hybrids.
Authors: Deinum B. , Bakker J.J.
Published: June 2020

A collection of 27 and 29 forage maize hybrids submitted for agronomic testing for 2 yr under Dutch conditions was also tested for whole crop digestibility. In 1976 (warm) and 1978 (cool) highly significant genetic differences were found in digestibility. This digestibility was only partly correlated with ear percentage (r = 0.48 and 0.46), possibly because the hybrids had already been screened for this character. However, digestibility was highly correlated with digestibility of cell-wall constituents of the stover (r = 0.85 and 0.80, resp.). Breeding for stover quality therefore appears promising. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of air-drying of soil samples upon some physical soil properties.
Authors: Van Schuylenborgh J.
Published: June 2020

Air drying of mountain soils (weakly podzolized brown forest types) which developed under a humid tropical climate appreciably increased the coarser fractions and decreased the finer fractions and the consistency values (plastic number, sticky point, etc.) of the samples. It appears that silicic-acid gels in these soils underwent an irreversible dehydration and exerted a vigourous cementing action on the soil particles. By this mechanism, and possibly due to some change in the nature of the organic matter, the characteristics of air-dried soils changed from that of a plastic clay to a coarse to medium sand of considerably lower water-holding capacity. Results suggest that samples of tropical soils of humid climates in particular should be analysed in their original moist state. (Abstract retrieved from CAB Abstracts by CABI’s permission)
A recording apparatus for measuring thermal conductivity, and some results obtained with it in soil.
Authors: Van Duin R.H.A. , De Vries D.A.
Published: June 2020

The automatic apparatus described comprises a number of elements which, placed to various depths at 3-90 cm in field soils, are successively switched on so as to give a straight-line photographic record of the deflections of a galvanometer. The gradient of the line is a measure of thermal conductivity, from which moisture content may indirectly be computed and evapo-transpiration determined by repeated measurements. Results of moisture determinations in a sandy soil under grass cover are reported. The method is well suited for observing moisture changes in lysimeters. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The influence of an isocaloric substitution of soya bean oil for carbohydrates and of the nutrient density of the feed on growth and efficiency of energy utilization in broiler chickens.
Authors: Grimbergen A.H.M. , Stappers H.P. , Cornelissen J.P.
Published: June 2020

From 5 weeks until 7 weeks old, broiler chickens were given 8 diets (crude protein 15.1 g/40 g) with metabolizable energy 1392, 1333, 1274, 1214, 1374, 1315, 1255 and 1196 kJ/40 g; in the last 4 diets (high-fat diets) 6 g of soya bean oil was used to replace an isoenergetic amount of carbohydrates (15.4 g) per 40 g basal diet. A decrease in the dietary energy from carbohydrates resulted in lower energy retention, mainly as a result of lower fat deposition. Isoenergetic replacement of carbohydrate by the soya bean oil had no effect on body composition but increased rate of gain and energy retention, and thus increased the efficiency of utilization of metabolizable energy. In another experiment with 5-week-old broilers, the effect of an isoenergetic replacement of carbohydrate by soya bean oil, using 2 different energy:protein ratios, with or without the addition of sand or cellulose as a diluent in the high-fat diets was studied. The replacement of carbohydrate by fat resulted again in improved efficiency of energy utilization. The diluent had no effect on the efficiency of energy utilization in the high-fat diets. Reducing the energy:protein ratio increased rate of gain, but also led to less efficient energy utilization as a result of a lower deposition of carcass fat. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Urea nutrition of young maize and sugar-beet plants with emphasis on ionic balance and vascular transport of nitrogenous compounds.
Authors: Beusichem M.L. van , Neeteson J.J.
Published: June 2020

In a pot trial, maize cv. Prior and sugarbeet cv. Polyrave were given N as urea or ammonium. There was no significant difference between DM producton in either spp. with the different N sources, although plant N content was increased with N supplied as ammonium. Root cumulative net proton extrusion closely agreed with calculated values for net absorption of cations, indicating that urea was absorbed intact, at a rate sufficient for growth. Xylem exudate was free from urea and NH3-N suggesting metabolism in the roots. Urea appeared to be assimilated other than by enzymic breakdown. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Responses of young cucumber plants to root and shoot temperatures.
Authors: Kleinendorst A. , Veen B.W.
Published: June 2020

Young cucumber plants were grown at all combinations of three shoot and three root temperatures (12, 18 and 24 degrees C). Growth and development of vegetative parts and fruits were studied after a temperature treatment of 14 days or 28 days. Shoot temperature has a positive effect on the rate of leaf development, while the rate of leaf initiation is influenced to a minor degree. There is only a small effect of root temperature on the rate of leaf appearance. The number of fruits is increased with increasing shoot and root temperature, the shoot temperature being more important than the root temperature. The total fruit fresh weight also increases with increasing shoot temperature; at 24 degrees C shoot temperature, the fruit weight shows an optimum at 18 degrees C root temperature. Distribution of dry matter is also dependent on root temperature and to a greater extent on shoot temperature. A shoot temperature of 18 degrees C is optimal for root growth, while 24 degrees C shoot or root temperature is sub-optimal for shoot growth. Increase in shoot temperature has a stronger positive effect on stem growth than on leaf dry weight. The relative effect of root temperature on stem growth equals that on leaf growth. Growth analysis shows that increase in relative growth rate at higher shoot and root temperatures under low light conditions is achieved by increasing the specific leaf area. This adaptation to changes in shoot or root temperature occurs within 14 days.
ADDITIONAL ABSTRACT: Cucumber plants (cvs Farbio and Sandra, both F1 hybrids) were grown at 12, 18 and 24 deg C shoot and root temperatures in all combinations. The number of fruits was increased with increasing shoot and root temperature, the shoot temperature being the more important. Total fruit fresh weight also increased with rising shoot temperature. At 24 deg shoot temperature, however, fruit weight was optimum with 18 deg root temperature. Also, at 24 deg shoot temperature, the lower the root temperature the more fruits were present at a given leaf number. A shoot temperature of 18 deg was optimal for root growth but 24 deg shoot or root temperature was still suboptimal for shoot growth. An increase in shoot temperature had a stronger positive effect on stem growth than on leaf dry weight. The relative effect of root temperature on stem growth was equal to that on leaf growth. Growth analysis showed that leaves became thinner at higher temperatures. This adaptation to changes in shoot or root temperature occurred within 14 days. Cvs showing the highest specific leaf area at the desired temperature seem to be the best qualified to give the optimal relative growth rate at the low light intensities prevailing in early spring. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Further studies on the effect of fat supplementation of concentrates fed to lactating dairy cows. 3. Effect on rumen fermentation and site of digestion of dietary components.
Authors: Tamminga S. , Vuuren A.M. van , Koelen C.J. van der , Khattab H.M. , Gils L.G.M. van
Published: June 2020

Fat-supplemented concentrates were given to dairy cows with rumen and duodenal cannulae, and the effect on rumen fermentation and site of digestion of dietary components was studied. Treatments were feeding concentrates supplemented with 7% fat (treatment C7), supplemented with 12% fat (treatment C12) and supplemented with 12% fat adsorbed on a carrier (treatment C12C). Small but significant changes in rumen fermentation characteristics such as pH, total VFA (volatile fatty acids) and NGR (non-glucogenic/glucogenic ratio) were observed with treatments C12 and C12C as compared with treatment C7. Numbers of protozoa were severely reduced with treatments C12 and C12C, but not with treatment C7. Site of digestion of organic matter and energy was affected by treatments C12 and C12C but this could be attributed to increased postruminal fat digestion. Total digestion and site of digestion of carbohydrate fractions (crude fibre, neutral detergent fibre, starch, sugars) were not affected by fat supplementation. Recovery of hydrogen in CH4 actually measured was close to 90% of that estimated from the rumen fermentation balance. Nitrogen flow to the small intestine was not affected by replacing part of the carbohydrates by fat, indicating an increased efficiency of microbial protein synthesis in the rumen when fat was increased. (Abstract retrieved from CAB Abstracts by CABI’s permission)
'The functional equilibrium', nibbling on the edges of a paradigm.
Authors: Lambers H.
Published: June 2020

Mechanisms underlying the functional equilibrium between aboveground and belowground organs of higher plants are discussed with reference to maize, potatoes, wheat, cucumber and Plantago lanceolata. Evidence is presented that the alternative path contributes to a significant extent in root respiration and as this path is only engaged when the supply of carbohydrates to a sink exceeds its demand, it is suggested that root growth is not limited by the supply of carbohydrates. The close correlation between carbohydrate supply to the roots and root growth cannot be explained by a limitation of root growth by carbohydrates but a satisfactory alternative explanation is not provided. Translocation of N from the leaves to the roots of wheat at both opt. and limiting nitrate supply is described. The proportion of N translocated to the leaves and then retranslocated to the roots was highest with limiting N. It is suggested that leaves are unable to incorporate all imported N under N-limiting conditions and that the excess N is then translocated back to the roots. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Issues in farming systems research.
Authors: Fresco L.O.
Published: June 2020

There is growing concern about the gap between maximum yields obtained in research stations and actual farmers' yields. Farming systems research (FSR) aims to study the production constraints of small farmers in the Third World outside the research station with a view to developing technologies that fit their needs. Stages in FSR are: definition of fields for recommendation, diagnostic survey, design and on-farm testing of technology, and dissemination. Major methodological and institutional issues in the FSR approach are discussed. It is concluded that a future role for FSR lies in broadening the scope of existing agricultural research programmes. Thus, FSR is not a separate discipline but provides a focus for the different disciplines involved in agricultural research. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Digestion of proteins of varying degradability in sheep. 3. Apparent and true digestibility in the small intestine and ileal endogenous flow of N and amino acids.
Authors: Bruchem J. van , Bongers L.J.G.M. , Walsem J.D. van , Onck W. , Adrichem P.W.M. van
Published: June 2020

Sugarbeet pulp, citrus pulp, sugarbeet molasses and minerals and vitamins were mixed with different amounts of groundnut expeller, potato protein, peas or dried brewers' grains to give 6 concentrates with protein solubility from 7 to 51%. The concentrates (600 g daily) were given with rye grass (300 g daily) to 2 Texel wethers with an infusion tube into the abomasum and with cannulae in the cranial duodenum and terminal ileum. Apparent digestibility of amino acid nitrogen in the small intestine was 57.0 to 73.2% and increased with increasing amounts of protein entering the small intestine. Mean true digestibility in the small intestine was 90.3%. Apparent and true digestibilities of individual amino acids varied considerably. Of protein leaving the small intestine 75% was endogenous (non-ammonia N 321 mg/kg0.75 daily). (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effects of pen size during rearing on later agonistic behaviour in piglets.
Authors: Lammers G.J. , Schouten W.G.P.
Published: June 2020

Agonistic behaviour during experimental social encounters between 2 unfamiliar pigs was studied in 10-week-old pigs reared in pens of 3.5 msuperscript 2 or 6.7 msuperscript 2. In 3.5 msuperscript 2 pens, pigs which became dominant in the experimental social encounters exhibited more abnormal agonistic behaviour than pigs reared in 6.7 msuperscript 2 pens. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The effect of intensification of shifting cultivation in Africa on stabilizing land-use and forest conservation.
Authors: Wiersum K.F.
Published: June 2020

Intensification of shifting cultivation towards more permanent forms of agriculture has been proposed as a means of stabilizing land-use and protecting forest resources in tropical countries. Based on the results of 4 African case-studies it is shown that it cannot be expected that changes in cultivation practices will in themselves have these results. Rather the new cultivation systems should be combined with measures to control possible negative effects in the socio-economic environment including changed attitudes towards land as a productive factor, and with measures to sustain the multifunctional characteristics of shifting cultivation. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of crude fibre, feeding level and body weight on apparent digestibility of compound feeds by swine.
Authors: Everts H. , Smits B. , Jongbloed A.W.
Published: June 2020

Compound feeds containing 43, 76 or 113 g crude fibre in DM were given to 22 adult sows and 18 growing male pigs. Digestibilities of DM, organic matter and crude protein were decreased with increased crude fibre in the diet, were decreased with increased intake from 1.2 times maintenance to 2.4 times maintenance and were increased with increased body weights. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The economic optimization of replacement decision for sows with a stochastic dynamic programming model.
Authors: Huirne R.B.M. , Dijkhuizen A.A. , Giesen G.W.J.
Published: June 2020

A stochastic dynamic programming model was designed to determine the economically optimum replacement decisions for sows. Influences of changes in production and prices on the optimum policy were established. An economic index was calculated to be used as a culling guide for individual sows. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Applications of material coordinates in the soil and plant sciences.
Authors: Raats P.A.C.
Published: June 2020

The continuum theory of mixtures is used to show the common basis of models in three areas. In each, the central problem is the description of the deformation and motion of a reference continuum and of the movement of one or more constituents relative to this reference continuum. The three applications concern the movement of solutes relative to soil water, the movement of soil water relative to the solid phase of swelling/shrinking soils, and the movement of water, solutes, and gases relative to growing plant tissues. (Abstract retrieved from CAB Abstracts by CABI’s permission)