EUF-nutrient contents required for optimal nutrition of grapes

Summary Our field surveys conducted in 10 Hungarian grape producing areas have revealed that the nutrient contents of vine leaves of different grape varieties were closely correlated with the EUF-nutrient contents of different soil types with different contents of clay. Resulting from these relationships the following EUF-nutrient values are considered as required for optimal nutrition of the vine-stock to attain grape yields of 10–12 t/ha in the areas under investigation:     

A comparison of electro-ultrafiltration and quantity/intensity measurements of soil potassium with its uptake by ryegrass in Scottish soils

Summary Electro-ultrafiltration (EUF) and quantity/intensity (Q/I) parameters of soil K were compared for 14 soils from each of three soil series. The K desorbed by EUF during the first 10 min (K₁₀) was closely correlated with the equilibrium activity ratio (AR₀) for soils of the same series, but differences between series reflected the soil K-buffering capacity, indicating that K₁₀ includes loosely held exchangeable K and is not strictly an intensity measurement. EUF values were compared with conventional soil test methods for predicting K-uptake and dry-matter yield of ryegrass grown in the glasshouse. Correlation coefficients between K uptake at the first cut were 0.80 for K₁₀, 0.88 for K_a (the initially labile K derived from the Q/I curve), 0.92 for K₃₅ (desorbed by EUF in 35 min) and 0.97 for K_ex (1.0M ammonium acetate extraction).     

Evaluation of the electro-ultrafiltration technique (EUF) as a measure of the K supplying power of Quebec soils

The electro-ultrafiltration (EUF) method has been used to evaluate the short-term and long-term supplying power of soils for many essential plant nutrients. The objective of this study was to compare the capacity of EUF with other extraction techniques to predict the plant availability of soil K and K fertilizer responsiveness by 10 cuts of alfalfa (Medicago sativa L.) growing over a 366-day period. Increasingly higher average concentrations of soil K were extracted by EUF at 50 V and 20°C (29 mg kg^-1), EUF at 200 V and 20°C (48 mg kg^-1), 0.002 M SrCl₂ (55 mg kg^-1), EUF at 200 V and 80°C (85 mg kg^-1), 0.1 M HCl (105 mg kg^-1), Mehlich 3 (119 mg kg^-1), 1 M NH₄OAc (120 mg kg^-1) and boiling 1 M HNO₃ (601 mg kg^-1). The large content of vermiculitic minerals in the silt and clay fractions is responsible for EUF desorbing more K in 55 minutes than NH₄OAc in 29 out of 30 soils. The total amount of K desorbed by EUF at 80°C was as effective as Mehlich 3-extractable K in predicting K uptake for the first three cuts and was best among the extracting procedures after boiling 1 M HNO₃ in predicting the long-term K supply, the uptake of K from non-exchangeable sources and the relative yield of alfalfa over 10 cuts. The desorption of soil K with EUF provides a better evaluation of the K-supplying power of Quebec soils than the extractants currently used, especially on a long-term basis.Contribution no. 396.     

Application of the EUF procedure in grape production

Summary The relationships between the nutrient contents in vine leaves and grape yield on the one hand and the nutrient contents in the soil on the other are described on the basis of results from pot and field experiments conducted over several years. The soils were analysed by means of conventional methods as well as by electro-ultrafiltration (EUF). The following results were obtained: The application of high K and P fertilizer amounts in pot experiments increased the availability of Mg, Mn and Fe. A marked rise in the Mg, Mn and Fe contents was observed in the vine leaves. The exchange processes due to fertilizer addition were well indicated by the EUF method, whereas the results obtained by extraction with ammonium lactate (AL) and CaCl₂ were unsatisfactory. Close and highly significant correlations were found between the EUF-P, EUF-K and EUF-Mg contents on the one hand and the P, K and Mg contents in vine leaves on the other. A close correlation also exists (r=0.91^***) between grape yield and EUF-K contents. Grape yield increases with increasing EUF-K values up to 25 mg/100 g/30 min at 20°C in pot experiments (30 cm rooting depth) and only up to 12 mg/100 g/30 min at 20°C in field experiments. The soil in this field experiment had, however, EUF-K values of 12 mg/100 g in the topsoil as well as in the subsoil. When assessing the limit values, it is therefore important to consider the depth of the horizon in which the nutrients are present. After addition of very high amounts of P fertilizer the P contents in vine leaves markedly decrease after one year, as there is a decline in the availability of phosphates. The EUF-P values measured immediately after the application of high doses of P fertilizer can only characterize the P supply status of a soil for a period of one or two years. The P availability after application of different forms of phosphate fertilizers (superphosphate, hyperphosphate) is well indicated by means of EUF, but not by means of the AL method. When assessing the required K and Mg values in the soil (whatever the method) the vine variety has also to be taken into account, whereas the utilization of soil phosphates depends less on the varietal differences.     

The relationship between EUF-K and soil-K fractions of different K selectivity

Summary The fraction of K released during EUF 30-35 min, 80°C, 400 V (EUF₃) and various other soil-K parameters were compared for 24 soils that range widely in clay mineral composition, clay content and percentage K saturation. When EUF₃ was compared with fractions of soil-K containing increasing amounts of non-exchangeable K (=selectively adsorbed K), the R² values decreased with increasing quantities of non-exchangeable K. This indicates that EUF₃ is a function of the exchangeable pool of K, although some initially non-exchangeable K is also involved.     

Comparative study on EUF and other methods of soil analysis for the determination of available potassium in soils from Northern Greece

Summary Twenty-one representative soils from Northern Greece could be grouped into three categories based on the EUF-K curves which displayed marked differences in the magnitude of K release by the soils employed. The cumulative K desorption by EUF within 35 min and the cumulative K-uptake values of ryegrass (10 cuts) were found to be correlated (r=0.87***). Although this correlation is rather close, the K dynamics of a soil can be better characterized by the course of the K-desorption curves. Because the quotient EUF-K-80°C/EUF-K-20°C can give information on the course of K desorption it is therefore sufficient in routine investigations to know the EUF-K-20°C contents and the numerical values of the quotients EUF-K-80°C/EUF-K-20°C.The EUF procedure does not only indicate the close relationship between K extracted and K uptake by plants, but it can also provide information on other nutrients in the same soil sample. With this extra information it was possible to explain why in some of the analysed soils K uptake was low despite high K availability, the reason being that P availability was not optimal in one of the experimental soils and that the Mn concentration of the soil solution was too high in another. At equal K availability the K uptake was also dependent on the amount of EUF-extractable N.     

Relationship between EUF-K contents,K uptake and sugar yield of sugar beet in deep loess soils

Summary In field experiments with varying K fertilization (1981 and 1982) changes in EUF-K contents were studied in deep loess soils of Southern Lower Saxony under sugar beet. A significant positive linear relationship was found between EUF-K contents at 20°C and 200 V (15 mA) of the topsoils and quantities of K absorbed by sugar beet in both years. The corresponding regression lines for 1981 and 1982 are almost parallel, the only difference being the yield level which was higher in 1982.The relationship between EUF-K contents at 20°C of topsoils and sugar yields showed the same parallelism for the two years. Not much increase in sugar yield was found at EUF-K contents over 12 mg/100 g soil at EUF-K 80°C/EUF-K 20°C ratios between 0.5 and 0.7. To attain a sugar yield of 10 t/ha an EUF-K 20°C value of at least 12 mg/100 g soil is required for these deep soils at the beginning of the K uptake period. This finding confirms experiences gained over an 8-year period at the Tulln Sugar Factory (Austria) with fertilizer recommendations based on EUF.     

Changes of EUF-N and EUF-K fractions in three deep grey-brown luvisols during 18 months under fallow

Summary The EUF-N and EUF-K contents of deep grey-brown luvisols under fallow were investigated over a period of 18 months.EUF-NO₃-N increased continuously during the spring and summer of 1983, reaching their peak in September/October. They declined in the winter of 1984, and increased again during the spring and summer of the same year.During the spring and winter EUF-N_org was higher than EUF-NO₃-N. A decline in EUF-N_org due to mineralization was associated with an increase of EUF-NO₃-N. EUF-N_org increased due to mobilization of soil N in April/May. EUF-N_org also increased in autumn 1983 as a consequence the incorporation of mineral nitrogen into this fraction. When mineral N was incorporated EUF-NO₃-N declined.EUF-N_org in the subsoil was lower than in the topsoil. EUF-NO₃-N in the subsoil decreased as EUF-N_org increased. It may therefore be assumed that the higher the content of EUF-N_org in the subsoil the more mineral nitrogen will be immobilized.     

Effect of liming on EUF-nutrient fractions in the soil,on nutrient contents of grape leaves and on grape yield

Summary In pot experiments with vine, liming significantly raised EUF-Ca 20°C as well as EUF-Ca 80°C values of an acid clay soil (pH 4.2). This resulted in a marked rise in Ca contents of vine leaves (Table 2). High amounts of K fertilizers without lime raised mainly the EUF-Ca 20°C values whereas the EUF-80°C values remained at a low level (Table 3). Liming lowered the EUF-K 20°C values and as a result the ratio EUF-K 80°C C/EUF-K 20°C increased from 0.7 to 1.0.High K applications raised the K content of the leaves at flowering stage but at grape ripening a marked decrease in K content was observed (Table 5). In contrast, the application of both lime and K fertilizer raised the K content of leaves at both flowering and ripening. Grape yield increased as well (Table 11).Liming raised the EUF-P values of the soil and to a lesser extent the P contents of leaves (Tables 6 and 7).High K applications without lime raised the Mn contents of leaves (Table 9), Exchange processes due to K fertilizer addition were reflected in increased EUF-Mn values (Table 9).The highest yield (three-year average) was obtained in a high K treatment (22 g K₂O/pot) in combination with lime (40 g CaO/pot).     

Determination of K forms in K-fertilized soils by electro-ultrafiltration

We confirmed the suitability of electro-ultrafiltration (EUF) for (a) determination of the distribution of potassium fertilizer among the various forms of potassium in soils with a predominance of micaceous minerals in their clay fraction, and (b) investigated the effects of the degree of openness of the dominant micaceous mineral and of incubation time on the kinetics of the EUF extraction of K from these soils.Samples of illitic, mixed-layer and vermiculitic soils from Galicia (N.W. Spain) were incubated at field capacity for 450 days with 0 (blank), 5,15 or 25 mg K (as KCl) per 100 g dry soil. After 1, 30, 150 and 450 days, subsamples were removed and repeatedly extracted using electro-ultrafiltration at low (20° C/200 V) and then high (80° C/400 V) temperature/voltage (6 and 10 five-minute extractions, respectively). Five different pools of K were identified: solution K (K_s), surface and internal K (collectively, K_p), slowly exchangeable K (K_e) and non-exchangeable K (K_i). The effects of increasing the incubation time depended on the dominant clay mineralogy: after 450 days, the K added to illitic soils was mostly solution K, whereas that added to vermiculitic soils was mostly internal K.For both low and high temperature/voltage EUF experiments, the extraction-time data were best fitted by the Elovich equation (extracted K=a+b ln t). The kinetic coefficient b depended on the incubation time and dominant clay mineral, and for given soil and incubation time increased linearly with the dose of added K.Abbreviations EUF Electroultrafiltration - K_s Solution potassium - K_p Easily exchangeable (surface + internal) potassium - K_e Slowly exchangeable potassium - K_i Non-exchangeable potassium