Available potassium reserves and release rate of nonexchangeable

Transcription

1 Symposium no. 14 Paper no. 973 Presentation: poster Available potassium reserves and release rate of nonexchangeable potassium in Greek soils SIMONIS A.D. Petrou Syndica 60B, Thessaloniki , Greece Abstract Thirty soils from several areas of Northern Greece were investigated. The available reserves and release K characteristics were determined in soils grown with ryegrass for 335 days and by continuous leaching of the soils with 0.01 N HCl. The available K reserves of the soils ranged from 346 to 2,058 kg ha 1 under ryegrass and from 603 to 3,211 kg ha 1 under continuous leaching, respectively. The rate of release of nonexchangeable K from soils ranged from 27 to 913 kg K ha 1 y 1, and 2/3 of the soils released the nonexchangeable K at a rate < 400 kg K ha 1 y 1. The total amount of potentially available K of the soils taken up by ryegrass, during the 335 days of experimentation, averaged 3% of the total potassium. The HClextractable K yielded a high correlation with the total Kuptake (r=0.90 *** ). The information on the rate of release of nonexchangeable K can be used as an index for the time period needed to cover the available reserves and as a measure for comparing soils with respect to their capacity to supply crops with nonexchangeable potassium. Keywords: available K reserves, release rate of nonexchangeable K, exhaustively cropping technique, continuous leaching technique Introduction Potassium is found in soils in three different forms and a three way dynamic equilibrium exists between them : Nonexchangeable K exchangeable K soil solution K Potassium is taken up by plants from the soil solution, and the concentration in solution will be replenished by the exchangeable fraction. Some of nonexchangeable K can also released into the soil solution and may thus be taken up by plants (Mcean, 1961; Blanchet and Bosh, 1967; Prasad and Power, 1997; Havlin et al., 1999; Brady and Weil, 1999). The capacity of soils to supply plants with K does not depend only on the amounts of K reserves in soil, but also on the rate of availability to plants. The latter can be estimated only with suitable experiments in pots (Grimme and Nemeth, 1978). Some soils can provide enough K for many years, but the release of K is slow to meet the needs of crops (Arnold and Close, 1961; Mc ean and Watson, 1985; Johnston and Goulding, 1990). The highest biggest practical difficulty in assessing available K reserves of soils arises from the soil s ability to release K from nonexchangeable sources (Mcean and Watson, 1985). The fact, that the soils vary markedly in their ability to supply plants with K from nonexchangeable sources, provides soil chemists with a most difficult and complex problem. Two ways of approaching the problem have been suggested exhaustive cropping in greenhouse and extraction analysis in the laboratory. 9731

2 17 th WCSS, 1421 August 2002, Thailand The exhaustive cropping technique, which has been employed in a variety of experimental conditions (Reitemeier, 1951; Arnold and Close, 1961; Salmon, 1965; Abed and Drew, 1966; Talibudeen and Weir, 1968), provides the most thorough mean of estimating nonexchangeable K reserves, though it involves a large amount of work, which is slow to execute. Extraction of soils with mineral acids at moderate concentrations, and usually at elevated temperatures, has been the laboratory technique most commonly used (Quemener, 1978; Black, 1993). Successive extraction of soil with 1N HNO 3 (Haylock, 1956), continuous leaching of soil with dilute HCl (Garman, 1957), extraction with H + saturated exchange resin (Barber and Matthews, 1962; Salmon, 1965; Blanchet and Bosh, 1967), and extraction with sodium tetraphenylboron (Schulte and Corey, 1965; Quemener, 1974) constitute, more or less, successful methods under certain conditions. Further possibilities are available from the successful application of electroultrafiltration (EUF) technique (Nemeth, 1979; Simonis and Nemeth, 1985). The assessment of available K in Northern Greece soils has been the subject of extensive investigation (Simonis, 1978; Simonis 1980; Simonis, 1986). Part of this work, concerning (a) the determination of the available K reserves and (b) the rate of release of nonexchangeable K, in 30 representative soils of Northern Greece, by exhaustive cropping and continuous leaching of soil with dilute HCl, is presented in this paper. Materials and Methods Soils used A total of 30 surface (020 cm) soils, representing the main soil types of Northern Greece, were selected to give a range of texture and clay content and other selected physicochemical properties (Table 1). Pot culture technique One kg of soil, mixed in plastic pots with 400 g of properly washed sand, and a basal nutrient solution containing 200 mg N, 100 mg P and water. The soil mixture in each pot was seeded with 1.5 g ryegrass (olium perenne, var. S23) seed and the pots were placed on a glasshouse bench in a randomized design. Each pot was placed in a plastic saucer which was used for watering. The grass was cut 10 times about 1.0 cm above soil level at 5 to 6 week intervals and after each cut extra nutrients, without K, were applied. The foliage was dried immediately after harvest at 80 o C, weighed, ground and stored for analysis. The dry matter of plant material (0.5 g) was ashed at 550 o C, and the residue was dissolved in a solution of 20% HCl for determination by flamephotometry. The amounts of exchangeable and nonexchangeable K uptaken by the ryegrass plants were calculated for each soil from the relation : Total K uptake by grass Exchangeable K uptake = nonexchangeable K uptake + K in roots (initial exchangeable Kfinal exchangeable K after cropping) Analytical methods Total K in the airdry soils was extracted with a mixture of H 2 SO 4 HClO 4 HF and the K determination in the digest by flame photometry (Jackson, 1958). Exchangeable K in the soil was determined, before and after cropping by leaching of the 9732

3 17 th WCSS, 1421 August 2002, Thailand soil with an excess of a 1.0 M ammonium acetate solution (NH 4 OAc). The continuous leaching of the soil with a 0.01 N HCl conducted separately according to the method of Garman (1957). Twentyfive grams of soil were mixed with 25 g of washed quartz sand and 6 g of resin (Amberlite JI20) placed in a leaching tube. The leaching solution was then passed through the soilsand mixture. The K accumulated through adsorption by the resin was removed by 0.01 N HCl. The leaching was adjusted to a rate of 1 per h. Each soil was leached with 10 of neutral ammonium acetate solution. Table 1 Great Soil Group and Selected Physicochemical Characteristics of Soils Studied. Soil No Great soil group Clay % Deg. Inceptisol Deg. Inceptisol Inceptisol Inceptisol Entisol Entisol Entisol Entisol Inceptisol Deg. Inceptisol Deg. Inseptisol Deg. Inceptisol Inceptisol Vertisol Vertisol Texture ph CaCO 3 % S S S S S S S S S C Si S S SiC S C trace OM % CEC cmol kg 1 soil Total K of soil %

4 17 th WCSS, 1421 August 2002, Thailand Results and Discussion Exchangeable and nonexchangeable K methods The total K uptake during the 335 days of growth, the initial and final exchangeable K of the soils, the exchangeable and nonexchangeable K uptake by ryegrass and the rate of nonexchangeable K uptake between the 5 th and 10 th cut, are given in Table 2 (mean of 3 replications). The total uptake (exchangeable and nonexchangeable) varied from to cmol kg 1 soil. The corresponding exchangeable K uptake varied from 2.21 to cmol kg 1 soil, while the nonexchangeable K uptake from 4.29 to cmol kg 1 soil. The soils differed significantly with respect to their ability to supply plants with nonexchangeable potassium. In all, but No 2, 25 and 26 soils (Table 2), over 50% of the total soil K taken up by plants, was originated from nonexchangeable K sources. The amount of K in soils, taken up by plants, as it is estimated by the exhaustive soil cropping technique represents the most reliable measurement of the available soil K sources. In general the total amount of potentially available K (exchangeable and nonexchangeable) of the soils studied, released to plants, averaged 3% of the total soil potassium. From this percentage, 30% was exchangeable and the remainder 70% nonexchangeable (Table 2). The later was comparatively higher in soils developed from basic rocks, than from acidic rocks. Characteristically, plants took up, on average, from Inceptisols (calcareous), more than twice as much amounts of nonexchangeable K (47.11 cmol kg 1 soil), than from Degr. Inceptisols (19.36 cmol kg 1 soil). Rate of nonexchangeable potassium uptake The rate of nonexchangeable K uptake in soils ranged from to cmol kg 1 soil d 1 (Table 2). From certain soils (Nos 8, 12, 28) even though their initial levels of exchangeable k differed significantly, about the same amounts of nonexchangeable K were released during the growth period. This means that, the equilibrium levels of exchangeable K in various soils, do not necessarily correlate with the ability of these soils to release K from nonexchangeable sources. The capacity of soils to supply K to plants depended not only on the quantities of different forms present, but also on the rate at which the exchangeable K was replenished from the nonexchangeable sources of the soils. A linear correlation (r=>0.90), significant for 0.1% level, was found between the total K cropping conditions with ryegrass, the level of exchangeable K uptake and the time, between the 5 th and the 10 th cut. It is known that, under exhaustively cropping conditions with ryegrass, the level of exchangeable K in most soils, after the 5 th or the 6 th cut, approaches the minimum value, afterwards plants take up the needed K from nonexchangeable K soil sources (Haylock, 1956; Arnold, 1958). Consequently, the slope of this linear relationship total K uptake over time for each soil, between the 5 th and the 10 th cut, may be used as a measure of plant availability. Extraction with 0.01 N HCl The amounts of K extracted from the soils, using the continuous leaching technique with 0.01 N HCl varied from 678 to 3,211 kg K ha 1. Figure 1 shows the cumulative curves of K extracted from the soils with 0.01 N HCl. 9734

5 17 th WCSS, 1421 August 2002, Thailand Table 2 Total K Uptake by Ryegrass, Initial and Final Exchangeable K of Soils, Uptake of Exchangeable and NonExchangeable K and Rate of NonExchangeable K Uptake. Soil No Mean Total K Uptake 1 cmol kg 1 soil (a) Initial Exch. K cmol kg 1 soil (b) Sum of 10 cuts of ryegrass and roots 2 after the 10 th cut 3 between the 5 th and 10 th cut Final 2 Exch. K cmol kg 1 soil (c) Uptake of Exch. K cmol kg 1 soil (d=bc) Uptake of Nonexch. K cmol kg 1 soil (ad) Rate of non Exch. K uptake cmol kg 1 soil/ day The total K uptake by plants (a) minus the fall in exchangeable K in soil (d = uptake of exchangeable K) gives the nonexchangeable K uptake (ad). For the calculation of the rate of nonexchangeable K uptake recorded in the last column in Table 2 see page

6 17 th WCSS, 1421 August 2002, Thailand Figure 1 Cumulative curves of soil extracted K with 0.01 N HCl. Available potassium reserves of soils Table 3 shows the available K reserves and the release rate of nonexchangeable K from the soils studied, using the exhaustive cropping and the continuous leaching technique. Table 3 Available K Reserves and Rate of NonExchangeable K Release in Various Great Soil Groups of Greece. Determined by the Techniques of Exhaustive Cropping and successive Extractions with 0.01 N HCl. Exhaustive cropping with ryegrass Successive extractions Available K reserves Rate of release With 0.01 N HCl kg ha 1 kg ha 1 y 1 Great soil group Number Range of Mean Range of Mean Range of Mean Deg. Inceptisols Inceptisols Entisols Mollisols s Vertisols of soils The available soil K reserves varied from 346 to 2,058 kg K ha 1 (method of K depletion by continuous cropping) and from 678 to 3,211 kg K ha 1 (method of continuous leaching). They followed the order : Inceptisols > Mollisols > Vertisols > Entisols > Degrated Inceptisols > s, and they were double in Inceptisols than in s. The nonexchangeable K release rate varied from 27 to 913 kg K ha 1 y 1 and followed the order : Inceptisols > Mollisols > Vertisols > Entisols > s > Degrated Inceptisols. They were on an average, characteristically, almost four times greater in Inceptisols (560 kg K ha 1 y 1 ) than in Degrated Inceptisols (150 kg K ha 1 y 1 ). There was a very high correlation between the K uptake by plants and the of analyses (extraction 31K) (Figure 2). 9736

7 17 th WCSS, 1421 August 2002, Thailand Figure 2 Relation between total Kuptake by ryegrass and of analyses (extraction 3K). The 2/3 of the soils released the nonexchangeable K at a rate less than 400 kg ha 1 y 1. Similar results were obtained from glasshouse experiments with ryegrass, in G. Britain, in which the nonexchangeable K release rate from 20 soils varied from 50 to 100 kg K ha 1 year 1 (Arnold and Close, 1961). Generally, the nonexchangeable K reserves of soils may be very high, but the low rate with which these K reserves of soils are finally becoming available to plants, will diminish plant growth and yield and will often lead to depressed soil fertility. Conclusions The following conclusions can be drawn from this study: (1) The available K reserves of soils varied from 346 to 2,058 kg K ha 1 (exhaustively cropping technique) and from 603 to 3,211 kg K ha 1 (continuous leaching technique (They followed the order: Inceptisols > Mollisols > Vertisols > Entisols > Degrated Inceptisols > s. (2) The rate of nonexchangeable K release from soils ranged from 27 to 913 kg K ha 1 y 1, while the 2/3 of the soils released the nonexchangeable K at a rate less than 400 kg K ha 1 y 1. It followed the order: Inceptisols > Mollisols > Vertisols > Entisols > s > Degrated Inceptisols. On an average, the rate of nonexchangeable K release was found four times greater in Inceptisols (560 kg K ha 1 y 1 ) than in Degraded Inceptisols (150 kg K ha 1 y 1 ). (3) The total amount of potentially available K of the soils taken up by ryegrass, during the 335 days of experimentation, averaged 3% of the total potassium. From this percentage, 30% was exchangeable and the remainder 70%, which was higher in soils developed from basic than acidic rocks, nonexchangeable. (4) The 0.01 N HCl extraction (continuous leaching technique) yielded a high relationship with the total K uptake by ryegrass (r=0.90 *** ). (5) The information on the nonexchangeable K release rate obtained, can be used as indices for the time period needed to cover the available reserves and as a measure of 9737

8 17 th WCSS, 1421 August 2002, Thailand comparison of soils with respect to their capacity to supply crops with nonexchangeable potassium. References Abed, F.M. and J.V. Drew Importance of illite as a source of K in Nebraska soils. Soil Sci. Soc. Am. Proc. 30:242. Arnold, P.W. and B.M Close Potassium uptake by cationexchange resins and minerals. Nature 182: Barber, T.E. and B.C. Matthews Release of nonexchangeable soil K by resin equilibration and its significance for crop growth. Can. J. Sci. 42:266. Black, C.A Soil Fertility Evaluation and Control. ewis Publishers. Blanchet, R. and M. Bosh Potassium balances of soils and the K nutrition of plants as influenced by fixation and liberation of nonexchangeable K + ions. Ann. Agr. 18: Brady, N.C. and R.R. Weil The Nature and Properties of Soils, 12 th ed. Prentice hall, New Jersey. Garman, W Potassium release characteristics of several soils from Ohio and New York. Soil Sci. Soc. Am. Proc. 21:5258. Grimme, H. and K. Nemeth The evaluation of soil K status by means of soil testing, pp In Proc. 11 th Congress Inter. Potash Inst., Bern. Haylock, O.F A method for estimating the availability of nonexchangeable potassium, pp In Proc. 6 th Inter. Congress Soil Sci. Havlin, J.., J.D. Beaton, S.. Tisdale and W.. Nelson Soil fertility and fertilizers. In An Introduction to Nutrient Management, 6 th ed. Prentice Hall, New Jersey. Jackson, M Chemical Analysis, pp Constable and Co td. Johnston, A.E. and K.W.T. Goulding, The use of plant and soil analyses to predict the potassium suppling capacity of soil, pp In Development of K Fertilizer Recommendations. Proc. of the 22 nd Colloquium of the International Potash Institute held at Soligorski, USSR, IPI, Worblaufen, Bern, Switzerland. Mcean, A.J Potassium supplying power of some Canadian soils. Can. J. Soil Sci. 41: Mcean, E.O. and M.E. Watson Soil measurements of plantavailable potassium, pp In Munson (ed). Potassium in Agriculture. ASACSSASSSA Madison, Wi. Nemeth, K The availability of nutrients in the soil as determined by EUF. Advances in Agronomy 31: Quemener, J The use of reagents containing sodium tertra phenylboron for the extraction of soil potassium application to the study of fertility problems, pp In 10 th IPI Congress. Prasad, R. and J.F. Power Soil Fertility Management for Sustainable Agriculture. C.R.C. Press. C. Quemener, J The measurement of soil potassium. IPI Research Topics 4:

9 17 th WCSS, 1421 August 2002, Thailand Reitemeier, R.F Soil potassium. Adv. In Agr. 65:135. Salmon, R.S Release of nonexchangeable K from some Rhodesian soils cropped with grass. J. Agr. Sci. 65:135. Schulte, E.E. and R.B. Corey Extraction of K from soils with sodium tetraphenylboron. Soil Sci. Soc. Am. Proc. 29:3335. Simonis, A.D The available to plants soil K and evaluation of methods for its determination. Dozent Thesis, Athens Faculty of Agriculture (in Greek). Simonis, A.D Determination of exchangeable and nonexchangeable K of soils and their availability to plants. Agr. Res. 4: (in Greek). Simonis Principles of potassium fertilizationthe Greek experience. In Potassium Symposium. Hellenic Society of Soil Science and International Potash institute (in Greek). Simonis, A.D. and K. Nemeth Comparative study on EUF and other methods of soil analysis for the determination of available potassium in soils from Northern Greece. Plant and Soil 83: Talibudeed, O. and A. Weir Rep. Rothamsted Exp. Stn. For p. 9739