bluuebunny/crossref_metadata_2025 huggingface dataset:
Examination of soils and crops after the inundations of 1st February, 1953. II. The influence of salt on the chief vegetable crops.
Authors: Van Dam J.G.C.
Published: June 2020

Eleven trial fields were selected on the islands of South Holland in an investigation of the reactions of vegetables to the salt content of the soil. The C index (number of grams of NaCl per litre of soil moisture) was calculated for the 5-20 cm. soil layer, and varied from normal to 8. In fields with a high C index the following effects were observed: Before rain leaching, seed germination of leeks, spinach and carrots was poor. Seed germination of chicory was also poor where the soil structure had deteriorated; soil structure was improved by gypsum applications. The crops grew more slowly and were harvested at a later date than in normal soils. Bolting was stimulated in cabbage lettuce and spinach. Lettuce, endive and savoy cabbage showed marginal leaf scorch, and leeks showed tipburn. Phaseolus beans, peas and strawberries were very sensitive to even a low salt content. There were only slight differences in yields of brassicas sown in situ and transplanted; with leeks sowing in situ was inferior to transplanting. The forcing quality of chicory roots from salty soils was approximately the same as of those from normal soils. The cauliflower crop failed in the trial fields. Yields of leafy crops were better in soils with high than with low moisture contents. Brussels sprouts and red cabbage were more susceptible to attack by Phoma lingam [Leptosphaeria maculans] in the salt trial fields than in normal soils. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Examination of soils and crops after the inundations of 1st February, 1953. III. Sensitivity to salt of inundated fruit crops.
Authors: Beeftink W.G.
Published: June 2020

Characteristic symptoms of salt water flood damage are described for apples, pears, plums, cherries, currants, gooseberry, walnuts, grapes and mulberries. In general the crops showed symptoms of drying out, indicating their inability to absorb enough water. A table of the approximate sensitivity of the fruit crops, and also of apple and pear varieties was compiled; there was a wider range of sensitivity in apples than in pears. The sensitivity of the chief Malling rootstocks did not appear to run parallel to their vigour. The salt content of the soil moisture was the limiting factor for apple and pear recovery; 7-8 g. per litre for apples, and 11-12 g. for pears were the limits beyond which trees could not be saved. Flooding had no influence on the growth condition of apples and pears until after it had lasted 8 or 9 weeks. Tree age had no clear effect on sensitivity, though apple trees of 25 years and over had less resistance. Deep cultivation before flooding, soil exhaustion, and general neglect had detrimental effects on tree resistance. (Abstract retrieved from CAB Abstracts by CABI’s permission)
The relation between the crude fibre content of food and the milk production.
Authors: Schoorl P.
Published: June 2020

The Friesian cow in Indonesia gives about 1, 500 1. milk in about 240 days compared with 3, 800 1. in 300 days in the Netherlands. The author believes that the main reason for the low production in the tropics is not climate, but faulty feeding practices. A cow fed a typical Indonesian ration of reedy grass and fibrous concentrates gave 1, 003 1. milk in the first no days of her first lactation, but increased to 1, 870 1. in the first 102 days of her second lactation when given a diet containing much less crude fibre, in spite of the fact that the former lactation was in the wet and the latter in the dry season. G.F.S. (Abstract retrieved from CAB Abstracts by CABI’s permission)
On the significance of some characteristics of egg production in breeding utility breeds of poultry.
Authors: Van Albada M.
Published: June 2020

Trials with White Leghorns from 1947 to 1952 showed that more accurate selection could be based on average length of laying cycle and age at first egg than on total production for the first laying year. To apply this method, careful observations must be made for a few months while the birds are trap-nested.-T. D. Bell. See also Absts. 5780, 5917, 5919, 5928, 1013. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Flow of water through plant roots.
Authors: Wind G.P.
Published: June 2020

The paper provides a mathematical discussion, illustrated with graphs, of the relationship be-tween pressure gradients required for the flow of water through soil and through roots at different soil depths, radius of root and of xylem vessels of grasses (Lolium perenne, Phleum pratense and Dactylis glomerata), and the upward flow of soil water to replenish that lost by transpiration. The discussion has a bearing on the point at which water enters the grass roots from the soil and explains why, in the grassland studied, little water was found in roots below a depth of 10 cm.-D.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effects of injection of saline with and without vitamin C on heat tolerance of neonatal chicks.
Authors: Hamdy A.A.M. , Henken A.M. , Hel W. van der , Elmoty A.K.I.A. , Galal A. Gh.
Published: June 2020

The effects of injection of saline (0.9% NaCl) with or without vitamin C on heat tolerance of newly hatched chicks were studied. Sham-treated chicks served as controls. The chicks hatched from eggs incubated at 45% RH or 55% RH. Between the first and the second treatment, a 48-h exposure period to a constant environmental temperature of 30 degrees C took place. Consecutively, production parameters were studied during a 4-week growing period. During heat exposure, chicks hatched from eggs incubated at 45% RH lost less body weight than those from eggs incubated at 55% RH. At the end of exposure, body temperature was lower in chicks hatched from eggs incubated at 45% RH compared to 55% RH. Incubation RH did not affect growth rate, feed intake, feed conversion and mortality during the post-exposure growing period. Injection of saline with or without vitamin C before exposure resulted in a higher body weight after heat exposure compared with controls. Injection of saline enhanced body weight to a greater extent than saline with vitamin C. Injection of either solution before or after exposure did not affect production parameters in the 4-week period after exposure, except for mortality. Mortality of sham treated chicks was higher than that of once or twice injected chicks. It is concluded that saline injection increased heat tolerance, but that addition of vitamin C did not have any contributing positive effect. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of nitrogen fertilization during raising of cauliflower transplants in cellular trays on plant growth.
Authors: Booij R.
Published: June 2020

The effects of N fertilizer applied by overhead irrigation, on cauliflower cv. Andes seedling growth during raising in cellular trays and on plant growth after field transplanting were studied during 1986-87. Increased N concentration (0-1.55 g/litre, applied twice a week) generally increased plant DW, plant height and leaf area, but significantly reduced percentage DM. DM production was greatest at 0.47 g N/litre, but leaf area expansion rate continued to increase beyond this N rate. A linear relationship between leaf area and plant height was observed which was independent of N fertilizer regime and duration of the seedling raising period (6 or 8 weeks). The large differences in plant attributes observed at the end of the seedling raising period had almost disappeared 3 weeks after transplanting in the field. At the final harvest, no significant differences between N treatments was detected for harvesting date, duration of the harvest period, curd quality or yield. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Autumn-cut grass silage as roughage component in dairy cow rations. 1. Feed intake, digestibility and milk performance.
Authors: Visser H. de , Hindle V.A.
Published: June 2020

A feeding trial was carried out with 56 dairy cows in >=2nd lactation. The duration of the experiment was 13 wk and started immediately after parturition. Basal diets consisted of maize silage, pressed beet pulp, moist ensiled maize gluten feed, ensiled brewers' grains and concentrates, which provided 70% of total DM. The remaining 30% of the DM consisted of grass silages, which were given as supplement to the basal diet. Treatments were wilted grass silage (WGS), moist grass silage ensiled with molasses (MGS), moist grass silage ensiled with formic acid (FGS) and wilted grass silage with added water (WW). The rations were given as a total mixed ration (TMR) to avoid selection. All grass silages were harvested between 30 Aug. and 1 Sept. from the same pastures. The moist grass silage differed in chemical composition from the wilted grass silage in ash (higher), crude fibre (lower) and NDF (lower). The in vitro and in vivo digestibility did not differ between silages. Total DM intake was lowest for both moist silages (MGS and FGS) and, as a consequence, net energy intake was also lowest with MGS and FGS. Milk yield was highest on WGS and WW, resulting from the higher energy intake. Milk fat yield and content did not differ between treatments. Milk protein yield was significantly lower for groups given MGS and FGS. Milk protein content tended to be lower for groups given FGS and MGS. During the experiment energy balance was negative on all treatments. Calculation of the duodenal digestible protein value (DVE), using the recommended equation for grass silage, gave WGS silage a better fit with the DVE balance measured in the feeding trial than found with high moisture silages (MGS, FGS), which appeared to be underestimated. Body weight changes correspond favourably with net energy balances, after correction of energy values for volatiles in grass silages, using individual net energy values for volatiles instead of an av. for grass silage OM. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Relation between stolon and tuber characteristics and the duration of tuber dormancy in potato.
Authors: Ittersum M.K. van , Struik P.C.
Published: June 2020

Potatoes cv. Diamant were grown in the greenhouse and date of stolon initiation, stolon length, position of the stolon on the stem, date of tuber initiation, position of the tuber on the stolon, tuber shape and tuber weight were determined. After harvest, tubers were stored at 18 degrees C to assess the duration of dormancy. By means of regression analyses, sets of variables were selected that explained the variation in duration of dormancy best. Tuber weight explained by far the highest proportion of the variation in dormancy and was negatively correlated with dormancy duration. The duration of dormancy was also significantly (positively) related to the date of tuber initiation and to the position of the tuber on the plant during its growth. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Development of integrated flower bulb production.
Authors: Raven P.W.J. , Stokkers R.
Published: June 2020

The Dutch flower bulb market, the aims of the Dutch government to develop more environmentally friendly approaches to agriculture by reducing inputs and emissions, and the economic implications of such a shift in policy to the bulb market are discussed. Reducing pesticide inputs by rotating crops, selecting suitable cultivars and using pathogen-free planting material, reducing inorganic fertilizer inputs by properly assessing the needs of crops and using organically-based nutrient sources, and reducing emissions to the environment by using better application techniques are advocated. Progress in the development of integrated bulb production schemes at 3 experimental farms in the Netherlands (at Sint-Maartensbrug, Hillegon and Zwaagdijk) is discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Integrated nursery stock production.
Authors: Dolmans N.G.M.
Published: June 2020

Integrated nursery stock production involves developing efficient and reliable systems for the production of quality stock while using reduced amounts of pesticides and fertilizers. Its aims are described and strategies for its introduction and development are set out. Three prototype integrated production systems are described, one for field-grown seedlings for forests, hedges and rose rootstock, another for field-grown ornamental shrubs and conifers, and a 3rd for container-grown ornamental shrubs and conifers in a specially-designed greenhouse. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Effect of injection of GnRH analogue at the onset of oestrus on LH and FSH release and embryonic mortality in gilts
Authors: Van Der Meulen J. , Helmond F.A. , Oudenaarden C.P.J. , Van Der Lende T. , Kronnie G.T.
Published: June 2020

In the 1st of 2 experiments, 5 gilts were injected with saline at the onset of standing oestrus (control oestrus), and at the next cycle the same gilts were injected with 100 mu g GnRH analogue. The LH and FSH peaks in the GnRH-treated oestrus were not significantly different from those in the control oestrus, but both peaks were sharper in the GnRH-treated oestrus. In the 2nd experiment, 49 gilts were injected with 100 mu g GnRH at the onset of standing oestrus or were not treated (controls), and slaughtered on day 4, 11, 13 or 35 of pregnancy. For animals slaughtered on day 4, 11 or 13, compared with controls, treated animals had significantly more corpora lutea (16.3+or-2.3 vs. 14.8+or-1.5) and embryos (15.0+or-3.0 vs. 12.1+or-3.4). Embryonic mortality on day 35 was 24.7% in the treated group vs. 11.3% in controls. The av. number of corpora lutea for gilts slaughtered on all 4 days was greater in treated gilts than in controls (16.4+or-2.3 vs. 14.3+or-3.3), but the difference was not significant. A similar trend was observed for number of embryos (15.4+or-2.0 vs. 13.0+or-3.3).
Autumn-cut grass silage as roughage component in dairy cow rations. 2. Rumen degradation, fermentation and kinetics
Authors: De Visser H. , Huisert H. , Klop A. , Ketelaar R.S.
Published: June 2020

In a 4 x 4 Latin square experiment the effects of DM content and/or the extent of fermentation in grass silages on the pattern of rumen fermentation and rumen kinetics were studied. In a separate study two cows were used to measure the rate of degradation using the dacron bag technique. Four rumen cannulated dairy cows were used to measure rumen fermentation pattern, rumen kinetics were measured in three of these animals. Basal diets (70% of total DM) consisted of maize silage, moist ensiled beet pulp, moist ensiled maize gluten feed, moist ensiled brewers' grains and a concentrate mixture. The remainder of the diet (30% of total DM) was wilted grass silage (WGS), high moisture grass silage with molasses (MGS), high moisture silage with formic acid (FGS) or wilted grass silage with additional water (WW). All diets were fed as complete feeds. pH of the rumen fluid was lower on the MGS and FGS diets. Concentrations of total VFA, acetic acid, ammonia and branched-chain fatty acids (BCFA) were highest on high moisture diets (MGS and FGS). Rates of clearance and digestion of the organic matter (OM) fractions were or showed tendencies towards being negatively influenced by both MGS and FGS, but remained unaffected by WGS and WW. Degradability of the grass silages was influenced by fermentation in the silo (lower digestible fractions and higher soluble fractions), as were rates of degradation (higher). Results of the degradability measured on the basal diet ingredients were in agreement with published literature and showed a strong correlation between OM digestibility in vitro and the undigestible fraction.
Growth, yield and composition of four winter cereals. II. Nitrogen and carbohydrate economy
Authors: Ellen J.
Published: June 2020

A field experiment with 3 cultivars each of wheat, rye, triticale and barley, grown at a density of about 320 plants/m, was conducted in 1986 on a fertile clay soil at East Flevoland, Netherlands. N at 120 kg/ha for wheat and triticale and 60 kg/ha for rye and barley was split-dressed in 2 applications. N yield was highest in wheat (196 kg/ha) and lowest in rye (123 kg/ha). The amounts taken up were influenced by the N rate. The triticale cv. Lasko and the barley cv. Marinka had a higher N-uptake than the other triticale and barley cultivars. N harvest index (i.e. the ratio of N in grains and N in above-ground DM at final harvest) was lowest in rye and highest in barley. N concentration in plant organs (grains, chaff, leaves, stems and roots) was higher in wheat and triticale than in rye and barley. This was probably caused by the difference in the level of N application. N use efficiency, expressed as grain DM production/kg N taken up, was 53 in wheat, 68 in rye, 50 in triticale and 61 in barley. In all species, the largest reserves of water-soluble carbohydrates (WSC) were found in the stems. Rye allocated more dry matter to stem growth before flowering than wheat, triticale and barley. Averaged over these cereals, 26% of WSC, produced before flowering, was used for redistribution and respiration during grain production.
Economic and environmental consequences of different governmental policies to reduce N losses on dairy farms
Authors: Berentsen P.B.M. , Giesen G.W.J.
Published: June 2020

Dairy farming contributes substantially to Dutch environmental problems. In this paper the central issue is to quantify the consequences of four government environmental policies on labour income and losses of nitrogen on dairy farms situated on sandy soil. Two policies impose a legal regulation and two impose a financial incentive to farmers. A linear programming model is used to model some typical dairy farms. The most important decision variables affecting nitrogen use and nitrogen losses are: the animal density on the farm, the feed ratio of the cows and young stock, the method and length of storing manure, the method of applying manure to the land, whether the land is used for grassland or fodder crops and the level of nitrogen application on grassland. The results show net farm income decreases (excluding levies paid) on the intensive farm up to Dfl 13 910 (17%). N losses on this farm decrease up to 283 kg/ha (54%). Finally, it appears from the results that it is much more expensive to reduce ammonia emission than to reduce the same amount of other N losses (leaching and run-off).
The influence of restricting nitrogen losses of dairy farms on dairy cattle breeding goals
Authors: Steverink M.H.A. , Groen A.F. , Berentsen P.B.M.
Published: June 2020

The objective of this paper was to investigate the influence of environmental legislation to restrict nitrogen losses on dairy cattle breeding goals. Linear programming was used to model a dairy farm, including multiple restrictions on product output and production factor input. Management was optimized to maximize labour income. Effects of genetic improvement on labour income (economic values) were derived for dry-matter intake capacity, body weight and milk production (carrier, fat and protein). Also effects of genetic improvement on the farm's nitrogen losses were computed. Basic economic values calculated were 0, -0.05, -0.18, 0.78, and 13.81 for dry matter intake capacity, body weight, carrier, fat and protein, respectively. With more stringent environmental legislation, the economic value of fat increased (1.68) and the economic value of body weight decreased (-0.21), with constant economic values of carrier, protein and dry matter intake capacity. Generally, a higher fat production per cow resulted in a reduction of nitrogen losses, and an increase in body weight increased nitrogen losses.
Validation of protein evaluation systems by means of milk production experiments with dairy cows
Authors: Van Straalen W.M. , Salaun C. , Veen W.A.G. , Rijpkema Y.S. , Hof G. , Boxem T.
Published: June 2020

Protein evaluation systems (crude protein (CP), digestible crude protein (DCP), protein digested in the intestine (PDI), amino acids truly absorbed in the small intestine (AAT), absorbed protein (AP), metabolizable protein (MP), crude protein flow at the duodenum (AAS) and digestible protein in intestine (DVE)) were validated using data from 15 production experiments with dairy cows, carried out in the Netherlands. Only treatments that were deficient in protein according to at least one system were selected. Average yield was 31.2 kg of fat and protein corrected milk daily and 989 g of milk protein daily. The observed milk protein production was compared with milk protein production predicted from the protein supply and requirements in each system. The difference between observed and predicted milk protein production expressed as the absolute and relative prediction error was smallest for the DVE-system (-2 g/day; 5.7%) and increased in the order CP (-22 g/day; 6.7%), PDI (-19 g/day; 7.8%), DCP (-44 g/day; 8.8%), AP(-37 g/day; 9.3%), AAS (100 g/day; 11.7%), AAT (112 g/day; 13.4%) and MP system (204 g/day; 22.9%). Predictions can be improved when a variable efficiency of milk protein production is used. In the DVE-system the observed efficiency decreased with increasing protein to energy ratio in the diet and milk production level. It was concluded that under Dutch conditions the prediction of milk protein production decreased in the order DVE, CP, PDI, DCP, AP, AAS, AAT and MP system.
Nitrogen fertilization and head rot in broccoli
Authors: Everaarts A.P.
Published: June 2020

An increase in the amount of N supplied (from 0 to 196 kg N/ha) to broccoli (Brassica oleracea var. italica) cv. Emperor led to an increased incidence of head rot (probably caused by a number of Pseudomonas and Erwinia species), which resulted in a decrease of the amount of marketable produce. Indications were found that head weight and head DM content are, probably indirectly, involved in limiting head rot at low N levels. The harvest index was not influenced by N treatment. Identification of the mechanisms which resulted in limited head rot at low N levels, could help to identify breeding characteristics for screening in agronomic evaluation programmes for broccoli cultivars under normal N levels.
Influence of stage of maturity of grass silages on protein digestion and microbial protein synthesis in the rumen
Authors: Bosch M.W. , Van Bruchem J. , Bongers L.J.G.M. , Tamminga S.
Published: June 2020

In four change-over experiments, wilted grass silages, differing in growth stage at harvesting and as a consequence in cell wall content, were fed ad libitum to dairy cows in early and late lactation. Ruminal degradation rate of the crude protein fraction of the silages was investigated using nylon bag incubations. No significant relation between the degradation rate (%h-1) and the cell wall content of the silages was found. The soluble and undegradable fractions of the crude protein both increased with an increase in silage cell wall content. The soluble fraction was more closely related to dry matter content and date of harvesting than to cell wall content of the silages. The fraction of dietary protein escaping rumen fermentation increased with cell wall content.In duodenal protein, the fraction originating from the diet, estimated using amino acid profiles of dietary, microbial and duodenal protein, decreased with cell wall content.
The influence of endometrium on morphology and oestrogen release of day-11 and day-13 pig blastocysts in vitro
Authors: Van Der Meulen J. , Helmond F.A. , Kronnie G.T. , Oudenaarden C.P.J.
Published: June 2020

Day-11 spherical and Day-13 filamentous blastocysts were cultured in vitro without supplementation of oestrogen precursors for 2 consecutive periods of 24 h, with or without endometrial tissue. Spherical Day-11 blastocysts flushed from one uterine horn (5.5 +/- 0.8 blastocysts; 5.3 +/- 0.4 mm in diameter; mean +/- s.d.) did not show gross morphological changes during the culture period. Free and conjugated oestrone (E1) and oestradiol-17 beta (E2) were released during the first and second 24 h culture period and was maximal during the first 24 h. In the presence of endometrial tissue the release of oestrogens from the blastocysts was reduced to 30-50%. Clewed Day-13 filamentous blastocysts, recovered after flushing, formed trophospheres and also in these cultures both free and conjugated E1 and E2 were released. In this case the addition of endometrial tissue did not affect the release of oestrogens from the blastocysts. Single Day-13 filamentous blastocysts cultured without endometrial tissue (n = 33, from 4 gilts), developed trophospheres and all blastocysts released E1 and E2. During the first 24 h on average per blastocyst 2.6 ng E1 (range 1.6-4.0) and 9.7 ng E2 (range 4.3-15.3) were released. In all cultures of spherical and filamentous blastocysts E2 release exceeded E1 release.These data show that Day 11-13 blastocysts are able to release both free and conjugated E1 and E2 during in vitro culture from endogenous precursors. The addition of endometrial tissue reduced the release of oestrogens from Day-11 but not Day-13 blastocysts. Whether this is due to an altered oestrogen release of the blastocysts in the presence of endometrium on Day-11 or due, to an increased uptake of oestrogens by the endometrium on Day-11 remains to be investigated.
Ammonia volatilization from nitric-acid-treated cattle slurry surface applied to grassland
Authors: Bussink D.W. , Huijsmans J.F.M. , Ketelaars J.J.M.H.
Published: June 2020

The reduction in NH3 loss from HNO3 treated cattle slurry, surface applied to grassland, was measured on different soil types throughout the Netherlands from 1989 to 1992. Thirteen micro-meteorological mass balance and 10 small wind tunnel experiments were carried out. Amounts varying between 7-17 and 10-30 m-3 ha-1 were applied, resp. and measurements were performed for 4 and 10 days, resp. The pH of treated slurry ranged from 3.9 to 6.6. A mean total of 60% (range: 29-98%) of the NH4-N from untreated slurry was volatilized in the mass balance experiments. A reduction in NH3 volatilization of 85, 72 and 55% was achieved for acidified slurry with a respective pH of c. 4.5, 5.0 and 6.0. Approx 55% (range: 7-91%) of the total loss from acidified slurry was measured on the day of application. A mean total of 66% (range: 21-90%) of NH4-N from untreated slurry volatilized in the tunnel experiments. The reduction in NH3 volatilization was 73% for slurry with pH 4.5. Approx 27% (range: 6-91%) of the total loss from acidified slurry was measured on the first day. The smaller reduction and the different pattern in NH3 volatilization observed in the wind tunnel experiments might be the consequence of different climatic conditions in and outside the tunnels or they might be related to the higher rates of slurry application in these experiments. Regression analysis indicated that high temperature, slurry pH, potential water evaporation and NH4+ concn stimulated NH3 loss in the mass balance experiments (Rsuperscript 2 = 87%). It is suggested that the results obtained with acidified slurry were independent of the grassland soil type at the application levels employed.
An environmental yardstick in farm economic modelling of future pesticide use: the case of arable farming
Authors: Verhoeven J.T.W. , Wossink G.A.A. , Reus J.A.W.A.
Published: June 2020

The integration of a new environmental yardstick for pesticide use in an economic farm model designed to monitor the environmental-economic interplay under changing price and policy conditions is discussed. The model is used to compare the effects of two control systems for pesticide use in arable farming in the Netherlands: the governmental system focusing on the amount of active ingredients used per hectare; and an alternative based on the detailed environmental criteria of the yardstick. The application for arable farming on a sandy soil indicates that, in the context of the national pesticides use reduction objectives for the year 2000, the economic effects of the two systems are similar. The environmental implications are far better represented by the yardstick, however.
The possibilities of near infrared reflection spectroscopy to predict total-phosphorus, phytate-phosphorus and phytase activity in vegetable feedstuffs
Authors: De Boever J.L. , Eeckhout W. , Boucque C.V.
Published: June 2020

238 samples, representing 19 vegetable feeds, were analysed for total and phytate phosphorus. Phytase activity was estimated in a limited number of feeds with an activity of >100 units/kg. Near infrared reflection spectra (NIRS) were taken between 1100 and 2500 nm in steps of 4 nm. By means of principal component analysis the feeds were grouped in starch- (n = 150) and protein-rich feeds (n = 88). NIRS-calibrations were developed using partial least square regression and tested by cross-validation. Total P varied from 0.22 to 1.25% and phytate P from 0.05 to 1.02% for high-starch feeds and, respectively, from 0.46 to 1.37% and from 0.22 to 0.56% for protein-rich feeds. Within these broad ranges, NIRS-values were highly correlated to measured total and phytate P with prediction errors of 0.08 and 0.08%, respectively, for high-starch feeds and 0.08 and 0.04%, for protein-rich feeds. However, considering the mostly small deviation of mean or calculated values for the individual feeds, NIRS is practical for predicting total P for wheat byproducts and phytate P for maize gluten feed. On the other hand, NIRS could be used for unknown or not tabulated products. Spectral signals from total and phytate P are partly based on direct responses from organic complexes but also on secondary relations through protein and fat. It was concluded that NIRS seemed not sensitive enough to detect phytase.
Linking GIS and models: structure and operationalisation for a Costa Rican case study
Authors: Stoorvogel J.J.
Published: June 2020

Users of geographical information systems often require very specific, disciplinary operations on geo-information that are not supported by GIS. These operations can be made available for GIS through links with external models. A general structure for the GIS-model interface is presented and identifies six consecutive steps: (1) geometry operations; (2) attribute operations; (3) data export from the GIS to the external model; (4) model run; (5) data import from the model into the GIS; and (6) visualization or spatial analysis of the model results with the GIS. This structure is illustrated for a case study from Costa Rica, where a GIS is linked with a linear programming model for the analysis of alternative land use scenarios. The structure can be used with many commercial software packages to develop user oriented applications.
Farm household modelling for estimating the effectiveness of price instruments in land use policy
Authors: Kruseman G. , Ruben R. , Hengsdijk H. , Van Ittersum M.K.
Published: June 2020

A farm household modelling approach using linear programming is presented that integrates biophysical and socioeconomic information for simulating micro-level responses to specific changes in the socioeconomic environment. The linear programming model includes separate modules for prices, production activities and expenditures from which the objective function is derived. Moreover, the model comprises a production structure adjustment coefficient to account for incomplete specification of the objectives of the farmer in the objective function. The model was calibrated for one specific farm type in the Atlantic Zone of Costa Rica, a peasant household growing basic grains and other food crops for household consumption and sale, and applied to calculate effects of several price instruments. The results, in terms of response multipliers, give an indication of the pace and direction of land use change at the micro-level as a result of (induced) change in the socioeconomic environment. The overall effect of an increase in biocide prices (taxation) is a change in cultivated crops and decrease in biocide use, but at the expense of a reduction in income. Increasing fertilizer prices affects income and utility positively. Thus, changes in fertilizer prices would seem to be an appropriate instrument to induce land use modifications.
Validation of Goudriaan's model: a case study for maize
Authors: Singh R.S. , Jacobs A.F.G.
Published: June 2020

The crop microclimate model of Goudriaan was tested, using data collected in a maize field in the Netherlands during one day in summer 1986. Except for the soil heat flux, latent and sensible heat fluxes were simulated reasonably well. Goudriaan's model overestimated the latent and sensible heat fluxes above the crop canopy by 9 and 10%, respectively, in comparison with the eddy correlation technique. The simulated fluxes could be improved by a better incorporation of the effect of dewfall in the model. Root mean square errors of the simulated soil temperatures at 1, 5, 10 and 20 cm depth were between 0.30 and 0.68 K. Sensitivity analysis of the model showed that the heat fluxes were more sensitive to soil than to crop parameters, for the same magnitude of variations. Among soil parameters, the soil surface resistance to evaporation had a large influence on the latent heat and the sensible heat fluxes at the soil surface; it also influenced the soil heat flux. Soil water stress had a large influence on the daily net CO2 assimilation as well as the latent and the sensible heat fluxes above the crop canopy.
Modelling the carbon cycle of grassland in the Netherlands under various management strategies and environmental conditions
Authors: Van Dasselaar A.P. , Lantinga E.A.
Published: June 2020

A simulation model of the grassland carbon cycle (CCGRASS) was developed to evaluate the long-term effects of different management strategies and various environmental conditions on carbon sequestration in a loam soil under permanent grassland in the Netherlands. The model predicted that the rate of increase in the amount of soil organic carbon will be greatest at low to moderate application rates of nitrogen (100-250 kg N/ha per year). This is because the annual gross photosynthetic uptake of CO2 in permanent grassland is hardly influenced by the level of N supply. Since N shortage stimulates the growth of the unharvested plant parts (roots and stubble) the carbon supply to the soil is highest at low to moderate N application rates. The rate of increase in soil organic carbon will be greater under grazing than under mowing as a result of a greater amount of carbon added to the soil. Increase of atmospheric CO2 concn may induce an increase in decomposition rate of soil organic matter due to simultaneously increased temperatures. At the same time, plant productivity and thus carbon supply to the soil will be stimulated due to the CO2-fertilization effect. Assuming a temperature increase of 3 degrees C if the present atmospheric CO2 concn doubles, the model predicted that the combined effect of elevated CO2 and temperature will slightly reduce the rate of increase in the amount of organic carbon in grassland soils compared to that under unchanged environmental conditions. There was 2% less carbon sequestration by grassland at the end of a 100 year period as a result of these changes in environmental conditions. The separate effects of increased temperature or elevated CO2 were 10% less and 10% more carbon storage after 100 years, resp.
Effects of nitrogen on development and growth of the leaves of vegetables. 1. Appearance, expansion growth and life span of leaves of Brussels sprouts plants
Authors: Biemond H. , Vos J. , Struik P.C.
Published: June 2020

In greenhouse pot trials, Brussels sprouts cv. Icarus SG2004 plants were supplied with various amounts of N at different stages during growth. The rate of leaf emergence ranged from 0.39 to 0.72 per day and was significantly increased by increasing N application rate. Leaf expansion rate and mature leaf area increased with leaf number, reaching maximum values between leaf number 10 and 20 and decreasing subsequently. Plants receiving more N had a higher total green leaf area per plant, due to more and larger green leaves. Specific leaf area of all leaves declined gradually from 130-230 cmsuperscript 2/g (depending on experiment) at about 30 days after planting to 60 cmsuperscript 2/g at the end of the experiments and was usually significantly increased by increasing N application rate.
Effects of nitrogen on development and growth of the leaves of vegetables. 2. Appearance, expansion growth and life span of leaves of leek plants
Authors: Biemond H.
Published: June 2020

In greenhouse pot experiments and field trials, leek cv. Albana plants were supplied with different amounts of N fertilizer at various growth stages. Leaf emergence, expansion, size and senescence were monitored. The rate of leaf appearance was not affected by N treatments and almost constant across experiments at 0.15/day. The rate of leaf expansion and the mature leaf area increased with leaf number, reaching maximum values between leaf numbers 11 and 14 and decreasing with higher leaf numbers. Both variables increased with increasing N application rate. The duration of leaf expansion was more or less constant across leaf numbers and not influenced by N treatments; the leaf expansion rate was the main factor determining mature leaf area. The rate of leaf senescence was not influenced by N treatments. Differences in total green leaf area per plant were caused by differences in the area of individual mature leaves and not by differences in the number of leaves. The specific leaf area of all leaves was more or less constant at 100 cmsuperscript 2/g.
Protein evaluation of cattle compound feeds: comparison of in sacco measurements and tabular values
Authors: De Boever J.L. , Vanacker J.M. , Bogaerts D.F. , Boucque C.V.
Published: June 2020

The supply of true protein to the small intestine (DVE) and the degraded protein balance (OEB) of 29 experimental compound feeds were estimated in the rumen and intestine of dairy cows (reference), using the nylon bag technique. DVE and OEB were also calculated from tabulated values of the ingredients, taken from the Dutch CVB-tables, assuming additive effects. Reference DVE was on average 11 g/kg DM lower and OEB 6 g/kg DM higher than tabulated values, resulting from a higher rumen degradability of protein (-5.5 percentage units) and lower intestinal digestibility of rumen undegradable protein (-2.0 percentage units) and a lower rumen degradability of starch (+5.8% units) and DOM-content (+27 g/kg DM). The possible causes of these differences are discussed. After elimination of systemic differences, residual errors between reference and tabular values amounted to 5.9 and 14.9% for DVE and OEB, respectively. It is concluded that a reasonable relation exists between DVE- and OEB-content of compound feeds based on tabular values for the ingredients and those calculated from in sacco measurements.
Relation between soil mineral nitrogen before sowing and optimum nitrogen fertilization in onions
Authors: De Visser C.L.M. , Van Den Berg W. , Niers H.
Published: June 2020

To study the relationship between the amount of soil mineral nitrogen before sowing of onions (Nmin) and the optimum amount of nitrogen fertilizer (Nopt), 36 multilevel fertilizer nitrogen trials were conducted in the Netherlands between 1978 and 1982. For 26 trials Nopt was within the studied range (0-200 kg N/ha) and could be estimated using a quadratic response function. A significant linear relationship between Nopt and Nmin before sowing was only found when Nmin in the layer 0-30 cm was considered. The same 26 trials were analysed together using a quadratic and a linear exponential response function. However, with both methods the yield predicted from Nmin did not prove to be superior to a fixed nitrogen application rate of about 125 kg of nitrogen/ha. A verification pointed out that the relationship overestimated the opt. amount of fertilizer nitrogen found in 8 independent multilevel fertilizer nitrogen trials. A fixed rate of 100-125 kg of nitrogen/ha yielded better results. The possible reasons for the absence of a strong relationship between the amount of soil mineral nitrogen before sowing and the opt. amount of nitrogen fertilizer are discussed.
Nitrogen effects in sugar beet growing: a module for decision support
Authors: Smit A.B. , Struik P.C. , Van Niejenhuis J.H.
Published: June 2020

PIEteR, a field-specific production model for sugarbeet in the Netherlands, is described. The model was developed as a basis for decision support, for example in determining N fertilizer requirements. Root and sugar yields, sugar content, (K + Na) and alpha -amino-N contents, extractability index, operating receipts (a measure for financial returns) and residual nitrogen in leaves are modelled as function of N availability, defined as (N-fertilizer rate + Nmin, 0-60 cm (soil, February)), and included in PIEteR as a so-called 'N-module'. Analysis of experimental data showed that root and sugar yield were optimal at 240 and 200 kg N ha-1, respectively. Sugar content and extractability index decreased, and (K + Na) and alpha -amino-N contents and fresh leaf yield increased with increasing N-availability. The operating receipts were optimal with 180 kg ha-1, or with a nitrogen fertilizer rate of 130 kg ha-1, assuming an Nmin-amount in soil in February of 50 kg ha-1. The results of the analysis were the basis for the functions in the N-module. In an independent test on data of 100 fields, the prediction errors for root and sugar yields and financial results decreased by about 2% and the explained variances increased by about 15% by including the N-module.
Effects of nitrogen accumulation and partitioning of dry matter and nitrogen of vegetables. 1. Brussels sprouts
Authors: Biemond H. , Vos J. , Struik P.C.
Published: June 2020

Three greenhouse trials and one field trial were carried out on Brussels sprout cv. Icarus SG2004 in which the treatments consisted of different N amounts and application dates. DM and N accumulation in stems, apical buds and groups of leaf blades, petioles and sprouts were measured frequently throughout crop growth. Total amounts of accumulated DM and N were affected by amount of N applied and date of application, but the final harvest indexes for DM and N (0.10-0.35 and 0.20-0.55, respectively) were not significantly affected by treatments in most experiments. Nitrate N concentrations were only high (up to about 2%) shortly after planting. The total N concentration of leaf blades and petioles increased with increasing leaf number. This increase resulted from a decreasing N concentration during the leaf's life. The total N concentration in sprouts changed little with leaf number.
Effects of nitrogen on accumulation and partitioning of dry matter and nitrogen of vegetables. 2. Leek
Authors: Biemond H.
Published: June 2020

Two greenhouse and 2 field trials were carried out on leeks cv. Albana with different N fertilizer rates and application dates. Observations included frequent measurements of DM and N accumulation in leaf blades, leaf sheaths and, if present, scapes. Both the amount of N applied and the time of application affected the total accumulation of DM and N in the plant. The relative partitioning rates of DM increase to the shaft were affected in such a way that the final harvest indices for DM (which ranged from 0.32 to 0.53) were significantly lower at higher N application rates. The final harvest indices for N (0.21-0.35) were not significantly affected by amount or timing of fertilizer applications. The total N concentrations of leaf blades and leaf sheaths decreased with increasing leaf age. Average nitrate N concentrations over all plant parts were always below 40%.
Modelling the release and loss of nitrogen after vegetable crops
Authors: Whitmore A.P.
Published: June 2020

A computer model is described that is able to simulate the mineralization-immobilization turnover of nitrogen derived from vegetable crop residues added to soil. Once mineralized, N is subject to loss from soil in the model by leaching and denitrification. That the mineralization part of the model works well is demonstrated with reference to some pot experiments in which residues from Brussels sprouts, leeks, cabbage or spinach were mixed with either a sandy or clay soil and incubated at 20 degrees C under optimal moisture conditions for 48 weeks. The release of mineral N was measured at intervals during the experiment and was strongly dependent upon the amount of N added in the crop residues: spinach (C:N = 6) released most nitrogen and most quickly, the other residues (C:N = 13-15) released N more slowly. With adaptations for field conditions, the model was then used to elucidate the fate of nitrogen remaining after field vegetables. The dynamics of both mineral and organic N remaining in soil were traced with this model. After spinach, much nitrate leaches to groundwater; sprouts, however, appear able to immobilize or denitrify what little mineral N remains at harvest reducing the loading of N in percolating water. The model suggests that during the last 40 years over winter losses of nitrate after cabbage almost always exceeded the EC drinking water limit of 11.3 mg NO3-N/litre: in some years by a factor of four. Since mineral N remaining in soil at harvest is shown to have most influence on leaching losses, measures taken to reduce unused mineral N will probably benefit groundwater quality most.
Growth of the Chromolaena odorata fallow vegetation in semi-permanent food crop production systems in south-west Cote d'Ivoire
Authors: Slaats J.J.P. , Van Der Heiden W.M. , Stockmann C.M. , Wessel M. , Janssen B.H.
Published: June 2020

Growing population pressure pushes farmers to use the young Chromolaena odorata fallow vegetation for food crop production. As a first step in defining appropriate management for such a fallow, the growth of this vegetation was studied by following changes in biomass, composition and nutrient content over time. The fallow vegetation rapidly covered the soil after crop harvest. Right from the start C. odorata was the dominant species, with an average annual growth rate of 8.7 t/ha. Standing biomass of the fallow vegetation reached a peak of 22 t/ha in the third year, while in subsequent years growth stagnated as a result of dieback of C. odorata. In the fifth year other woody species tended to succeed C. odorata as the main component of the fallow vegetation. In 5 yr the vegetation accumulated 130 kg N, 9 kg P and 160 kg K/ha. The results suggest that a fallow period of 3 yr is most appropriate when using this type of fallow vegetation in semi-permanent food crop production systems.
The influence of soil phosphorus, pH and texture on the uptake of phosphorus from soil and fertilizer by upland rice
Authors: Van Reuler H. , Janssen B.H.
Published: June 2020

At six sites in 1987, and two sites in 1988 in the Tai region of south-west Cote d'Ivoire, long-term field trials were started to study the supply of nutrients from the soil and the response of food crops to fertilizers. The results for P during the first season after removal of the primary or secondary forest vegetation in experiments with rice are described. P rates were 0 or 50 kg/ha in 1987, and 0, 12.5, 25 or 50 kg in 1988. The application of 50 kg P increased grain yield by 0.5-1.0 t/ha at five of the six sites in 1987. In 1988, a similar response could be obtained with lower rates of 12.5 or 25 kg P ha. At all sites, P application increased P uptake significantly, but the recovery of fertilizer P decreased with increasing P application rates. The soil P supply was best described by an equation including P-Dabin (a modified P-Olsen method), total P and pH. The recovery of fertilizer P could best be described by equations including silt plus clay content, P-Dabin, and/or total P. Since some soils had a high gravel content, soil analytical data, referring to the fine earth (