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Monthly communications by the International Potash Institute, Berne (Switzerland)

Subject 4 Soil Science April 1965 34th suite

The Fixation, Accumulation and Depletion of Potassium in Lowland Rice Soils

M. P. Feng and S.C. Chang' From: Memoirs of College of Agriculture, National Taiwan University, Taipei, Vol. 8, No. 1 (1964) Analyses of a large number of paddy soil samples representative of the main soil groups in Taiwan, from acidic Latosols to calcareous alluvial soils, reveal that the contents of exchangeable potassium are generally low, from 50 to 80 ppm, and rather uniform among soil groups, while those of non-exchangeable potassium are much higher and vary considerably among soil groups (Chang and Feng, 1960). Studies on the soils from a long-term fertilizer experiment of lowland rice show that neither the depletion of exchangeable and non-exchangeable potassium in the no-potassium plot nor the accumulation in the potassium-treated plot is noticeable (Chang and Chu, 1960). All these data suggest that the equilibrium of the various forms of potassium in flooded soils must be different from that in upland soils. Systematic data on this subject are, however, scanty.The purpose of this paper isto make a preliminary study with regard to the fixation, accumulation and depletion of potassium in a number of soils of Taiwan under flooded condition for rice growing.

Materials and Methods Three series of experiments are included in this investigation. Soil samples taken from the plots of nine long-term experiments of potash fertilizer conducted on representative soils of Taiwan were used to observe the change of exchangeable and non-exchangeable potassium resulting from different fertilizer treatments. These long-term experiments were started in 1958 or 1959. Samples of surface soils and subsoils were collected after the harvests of the second crop of rice each year successively for the last three years from 1959 through 1961. The general properties of the nine soils and two other soils which were used in the later part of this investigation are shown in Table 1. The fixation of potassium was studied on five representantive soils from Chunglee, Taoyuan, Taichung, Yuanlin and Hsinying, respectively. Potassium at rates of 200 and 400 ppm was added to the soils. The soils were kept under four different moisture conditions for three months. The soluble and exchangeable potassium was determined, and the fixed potassium calculated to study the distribution of the added potassium into these various forms. Research Assistant, and Professor, Soils and Plant Nutrition Laboratory of National Taiwan University, Taipei, Taiwan. Date received for publication: February 10, 1964.

1 ... The release of potassium under excessive leaching was studied with four soils from Chunglee, Taichung, Yuanlin and*Hsinying. 400 ppm of K was added to each soil on a Buchner funnel and kept under continuous flooding and percolation by adding water to the funnel as needed. Soluble potassium was determined in successive 200 ml portions of leachate for five times. The total number of days needed to collect 1000 ml of leachate is around 10 days for the soils of Chunglee and Tai- chung, 20 days for the soil of Yuanlin and 40 days for the soil of Hsinying. The exchangeable and non-exchangeable potassium of the treated soil was also determined. Table 1 General properties of the soils used

Dominant Organic clay Locations Soil groups Texture pH matter (%) minerals

Chunglee Latosol Silty clay loam 4.7 2.0 Kt' Nanshi Latosol Silty clay loam 4.9 1.3 Kt Taoyuan Latosol Silty clay loam 4.9 2.2 Kt Taipei Sandstone and shale Silt loam 4.8 2.5 Kt, It alluvial soil Hsinchu Sandstone and shale Silt loam 6.1 3.1 Kt, It alluvial soil Miaoli Sandstone and shale Sandy loam 5.9 1.2 Kt. It alluvial soil Hsinhua Sandstone and shale Silt loam 6.1 1.2 Kt, It alluvial soil Yuanlin Slate alluvial soil Silt loam 7.5 2.1 It Silo Slate alluvial soil Silt loam 6.4 2.1 It Pingtung Slate alluvial soil Silt loam 6.2 1.9 It Hsinying Mudstone alluvial soil Silty clay loam 7.3 2.1 It

" Soil: H.O is I : 1. " Kaolinite S]llite

Throughout this investigation, soluble, exchangeable, and non-exchangeable potassium was extracted by water, neutral N ammonium acetate (Schollenberger, 1945), and sulphuric acid (Hunter and Pratt, 1958), respectively. The potassium in the extract was determined flamephotometrically.

Results and Discussion The exchangeable and non-exchangeable potassium in the soils sampled from the fields of nine potash fertilizer experiments in three representative soil groups are presented in Table 2. In the potassium-treated plots. 80 kg/ha of K2O or 33 ppm of potassium on the basis of 2 000 000 kg/ha of furrow slice of soil, were applied for each crop. There- fore, the total potassium applied for the experiments started from the second crop of rice of 1958 is equivalent to 231 ppm (7 crops), and that for experiments started from the first of 1959 is 198 ppm (6 crops). A perusal of the figures in Table 2 shows that the tendency of accumulation and depletion of potassium in the soils, year by year, is not consistent, yet the tendency does show that neither depletion in the no-potassium plots nor accumulation in the potassium-treated plot is signifi-

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4/34

Table 2 Exchangeable and non-exchangeable K in the soil sampled in successive years

Location of Treat- Exchangeable K ppmO Non-Exchangeable K ppmn experiments ments Soil layers 1959 1960 1961 Average 1959 1960 1961 Average

K Surface soil 56 61 60 59 61 72 53 62 K. 1 Subsoil 44 44 39 42 56 79 61 65 Surface soil 66 66 91 74 62 72 42 59 h e Subsoil 44 49 58 50 66 74 55 65 fhnlrSurface soil 59 84 60 66 61 64 53 599 MK. 1 Subsoil 41 46 41 43 57 79 59 65 Surface soil 76 95 94 88 62 65 51 59 Subsoil 44 74 59 59 69 64 64 66

Surface soil 75 81 69 75 93 82 91 90 K. ( Subsoil 74 69 66 70 106 91 74 90 92 92 94 K Surface soil 91 98 103 97 99 Subsoil 86 69 81 79 109 96 89 98 Nanshi M Surface soil 91 79 86 85 99 111 74 95 MK. N Subsoil 86 58 71 72 99 122 84 102 100 66 82 MK. Surface soil 105 95 124 103 80 Subsoil 89 61 76 75 81 119 69 90

Surface soil 54 40 35 43 96 90 105 97 K. Subsoil 49 40 33 41 149 125 150 141 Surface soil 55 40 41 45 115 110 104 110 I Subsoil 43 40 33 39 157 156 142 151 Taipei Surface soil 50 38 38 42 95 117 90 101

Subsoil 43 40 31 38 147 160 139 149 116 100 106 m Surface soil 58 44 45 49 102 Subsoil 43 38 31 37 147 170 149 155

Surface soil 50 46 41 46 150 164 194 169 K. Subsoil 49 43 35 42 159 190 208 186 K. Surface soil 50 50 49 50 160 180 186 175 163 207 218 196 in K Subsoil 50 46 35 44 160 184 166 MK. Surface soil 45 53 46 48 155 Subsoil 49 44 35 43 176 181 208 188 153 162 186 167 MK. Surface soil 55 58 54 56 Subsoil 45 44 39 43 175 169 209 184

Surface soil 23 34 25 27 50 54 53 52 K. Subsoil 23 53 20 32 50 70 50 57 Surface soil 25 53 30 36 58 70 58 62 Miaoli K, Subsoil 21 34 21 25 52 51 52 52 50 54 MK. Surface soil 24 28 25 26 56 55 Subsoil 21 23 21 22 57 50 52 53 Surface soil 28 28 34 30 60 57 54 57 Subsoil 24 21 26 24 59 59 47 55

3 Location of Treat- Exchangeable K ppm' Non-Exchangeable K ppm' experiments ments' Soil layers 1959 1960 1961 Average 1959 1960 1961 Average

Surface soil 33 60 36 43 150 158 154 1 Subsoil 38 50 44 44 245 265 269 260154 K= j Surface soil 30 43 35 36 165 155 160 160 HsKnhu Subsoil 36 43 38 39 257 220 230 236 Surface soil 29 50 34 38 164 168 179 170 MK. Subsoil 36 44 38 39 242 236 230 236

MK J Surface soil 33 35 35 34 170 185 155 170 Subsoil 36 38 35 36 242 243 218 234

K. Surfacesoil Subsoil 24 20 26 23 109 108 107 103 K 23 18 23 22 130 152 144 142 K2 Surfacesoil 28 20 26 25 117 115 124 119 YuaKlin Subsoil 23 18 23 22 127 152 146 142

MK. Surface soil 25 23 26 25 115 110 116 114 Subsoil 24 23 24 24 129 152 146 142 MK, Surface soil 28 29 28 28 122 111 127 120 Subsoil 25 21 25 24 135 154 150 146

K. Surface soil 34 44 54 44 179 181 166 K Subsoil 33 175 40 38 37 185 213 182 193 K2 Surface soil 38 46 55 46 175 182 193 183 Silo Subsoil 34 40 39 38 194 203 234 210 MK. Surface soil 40 43 40 41 173 182 173 176 ( Subsoil 35 40 38 38 195 208 222 208 K{ Surface soil 40 46 49 45 176 197 194 189 Subsoil 34 38 39 37 189 192 214 198

Surface soil 35 35 33 34 143 178 147 156 K Subsoil 28 29 33 30 180 239 220 213 K. Surface soil 38 55 38 44 145 205 150 167 Pingtung Subsoil 29 34 35 33 166 251 233 217 MK. Surface soil 35 60 36 44 143 193 149 162 Subsoil 29 30 33 31 164 275 202 214 MK2 Surface soil 35 50 39 41 148 213 146 169 Subsoil 28 30 38 32 165 263 210 213

5 M represents 8 mt/ha of compost per crop. Kaand K. represent 0 and 80 kg/ha of KO per crop, respectively, 80 kg/ha of N and 60 kg/ha of P.O. were applied to all treatments. S * The field experiments of Chunglee, Taipei, Hsinchu, Miaoli, and Yuanlin were started from the second rice crop of 1958, while the others were started from the first rice crop of 1959. cant within the experimental error of sampling and determination, except that there is a slight indication of accumulation of exchangeable potassium in the Latosols of Chunglee and Nanshi and of non-exchangeable potassium in the calcareous soils of Yuanlin, Silo and Pingtung. This phenomenon suggests that in flooded soils, the transformation of potassium from mineral to non-exchangeable, exchangeable and soluble form is quicker than in the upland soils. On the other hand, the applied potassium is also rarely fixed, and leaching of potassium is tremendous. This is in agreement with the early observation by Chang and Chu (1960). The fixation of 400 ppm of potassium added under four moisture conditions in a period of three months is shown in Table 3.

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Monthly communications by the International Potash Institute, Berne (Switzerland)

The four conditions are: continuous field moisture capacity, continuous flooding, alternate flooding and drying to field moisture capacity for 8 cycles in three months, and alternate flooding and drying to air dryness for 5 cycles in three months at room temperature. The soluble and exchangeable potassium of both the check (no potassium added) and treated soils was determined. The distribution of the added potassium into the soluble, exchangeable and non-exchangeable forms was then calculated. The figures in Table 4 clearly show that the two Latosols can fix little potassium, the calcareous alluvial soils of Yuanlin and Hsinying can fix a considerable great amount of potassium, while the acid alluvial soil stands intermediate. Conti- nuous flooding seems to cause an increased fixation in the two kaolinitic Latosols and the acid alluvial soil, but no significant influence on the two illitic calcareous alluvial soils. Alternate flooding and drying to field moisture capacity does not appreciably increase the fixation over the continuous flooding and continuous field moisture capacity but alternate flooding and drying to air dryness almost doubles the fixed amount at the rate of 400 ppm of potassium by the two calcareous alluvial soils. During the growing period of rice, the paddy soil is kept continuously under f!ooding; occasionally it may be under alternate flooding and drying to field moisture capacity, but would rarely be subjected to air dryness. In view of the fact illustrated in Table 3 that even in the calcareous soils with high fixing power, only one fourth to one half of the added potassium was fixed under condition of continuous flooding and alternate flooding and drying to field moisture capacity, the amount of potassium to be fixed at the moderate rate of application of potassium such as 33 ppm in the above mentioned field experiments would be reasonably negligible, particularly under the open system of field condition where excessive leaching is unavoidable. The potassium leached out under continuous flooding is shown in Table 3.

Table 3 K in succesive 200 mIs of leachate K intreated K in original soil Loca- Treatments Soluble K ppm soil ppm ppm ttion Of K oi Moisturesture1 st 2nd 3rd 4th 5th Non- Non- Soils applied condi- 200m] 200 20Or 200ml 200ml Total Exch. exch. Solu. Exch. exch. ppm tion Chun- Flood- glee 0 ing 25 13 10 8 10 66 48 69 0 61 69 Flood- 400 ig 300 43 25 19 15 402 101 50- - - Taich- Flood- ung 0 ig 100 23 15 15 10 163 48 66 59 108 82 Flood- 400 ig 405 52 30 23 24 534 89 88- - - Yuan- Flood- [in 0 ing 22 13 10 15 10 70 39 91 3 36 82 Flood- 400 mg 271 58 30 24 18 401 60 88- - - Hsiny- Flood- ing 0 ing 20 15 10 18 15 78 50 316 5 64 313 Flood- 400 ing 178 63 44 39 24 348 100 347 - - -

5 ... Table 4 The distribution of added K in various forms

Sandstone and shale alluvial soil Slate alluvial soil Mudstone alluvial soil Treatments Latosol (Taoyuan) Latosol (Chunglee) (Taichung) (Yuanlin) (Hsinying)

K Soluble Exch. K Soluble Exch K Soluble Exch. K Soluble Exch. K Soluble Exch. K applied Moisture K K fixed K K fixed K K fixed K K fixed K K fixed 7 ppm condition ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm

200 Continuous F.M.C. 65 151 -16 68 114 18 102 73 25 48 76 76 30 93 77 Continuous flooding 45 157 - 2 39 136 25 73 75 52 48 82 70 23 105 72 Alternate flooding 81 132 -13 69 129 2 100 74 26 51 SS 61 23 96 81 and F.M.C. Alternate flooding 59 141 0 56 142 2 93 76 31 43 86 71 24 92 84 and air dry

400 Continuous F.M.C. 170 266 -36 164 259 -23 232 161 7 115 166 119 79 224 97 Continuous flooding 121 293 -14 116 273 11 186 147 67 121 158 121 63 218 119 Alternate flooding 175 244 -19 153 246 1 158 154 88 123 155 122 70 201 129 and F.M.C. Alternate flooding 155 268 -23 145 244 11 143 153 99 65 128 207 38 129 233 and air dry

F.M.C. represents Field Moisture Capacity. 0 rp)of ask (Review

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4/34 In the first 200 ml of leachate, more than half of the added 400 ppm of potassium was washed out of the soils with the exception of the calcareous Hsinying soil. Thereafter the potassium was washed out at a lower rate; however, 1000 ml of water washed out almost more than three fourth in the first three soils, and more than half in the last soil. Although the rate of potassium used in this experiment is almost 10 times the practical rate, but with a percolation of water at a magnitude approaching 1000 mm of water per crop as is commonly the case in Taiwan, the leaching loss would likely be equal to or even over the commonly applied amount. Another interesting point illustrated in Table 4 is that the exchangeable and non-exchangeable potassium in the treated soil with no potassium added are almost comparable to those in the original soil, except in the soil of Taichung which con- tains originally a relatively higher amount of soluble and exchangeable potassium. This fact strongly indicates that the transformation of potassium from mineral to non-exchangeable and exchangeable forms is rather quick.

Conclusion The kaolinitic Latosols in Taiwan have extremely weak power to fix potassium, but the illitic calcareous soils can fix a considerable amount of added potassium. At the moderate rate of application of potassium, the different moisture conditions including those under continuous flooding, field moisture capacity, and alternate flooding and drying to field moisture capacity or to air dryness, do not appreciably influence the amount of potassium to be fixed, but at a high rate of application of 400 ppm of potassium, alternate flooding and drying to air dryness almost doubles the amount of fixation in the calcareous soils. Since air drying would seldom occur in the growing period of lowland rice, representative Taiwan soils would hardly fix any appreciable amount of potassium at the common rate of application under field conditions of lowland rice. Consequently, under intensive leaching of flooding soil, most of the added potassium will be washed away during the whole growing period of about four months. However, due to the relatively quicker transformation of potassium from mineral form to exchangeable and non-exchangeable forms, the soil can maintain a fairly constant status of exchangeable and non-exchangeable potassium. This explains why neither depletion nor accumulation of potassium in the check and potassium treated plots was observed in some field experiments of potash fertilizer. It seems that the response of rice to potash should be better corre- lated with the reserve amount of potassium in the soil rather than the apparent exchangeable potassium. Whenever the reserve is low, potassium fertilizer should be applied in split lots to avoid the leaching loss.

Summary Representative soils of Taiwan sampled from nine field experiments of potash fertilizer for rice conducted for 3 to 4 years were analyzed to determinethe exchangeable and non-exchangeable potassium resulting from different treatments of potassium application. It was found that neither depletion of potassium in the no- potassium plots, nor accumulation in the potassium-treated plots was appreciable.

7 ... It was further found with four representative soils that at the practical rate of application of potassium under the moisture condition of paddy soil during the growing period, potassium is not significantly fixed in all soils from kaolinitic to illitic. While on the other side, leaching loss of the added potassium is tremendous. The soil after excessive leaching of potassium can quickly restore to its original status of exchangeable and non-exchangeable potassium under flooded condition. This explains the little change of exchangeable and non-exchangeable potassium in the plots of the above mentioned potash fertilizer experiments on rice. The practical meaning of this investigation with regard to potash application on lowland rice was discussed.

Bibliography

1. Chang S.C. and Chu W.K.: Effect of fertilizer treatments on the exchangeable bases of lowland paddy soils. Memoirs of the College of Agri., National Taiwan University, Vol. 5, No.4 (1960. 2. Chang S.C. andFang M.P.: Exchangeable and non-exchangeable potassium in the main agricultural soils of Taiwan. Memoirs of the College of Agri., National Taiwan University, Vol. 5, No. 4 (1960). 3. Hunter A.H. and Pratt P. F.: Extraction of potassium from soils by sulfuric acid. Soil Sci. Soc. Amer. Proc. 21; 595-598 (1957). 4. Schollenberger C.J. and Simon R.H.: Determination of exchange capacity and exchangeable bases in soil-ammonium acetate method. Soil Sci. 59; 13-38 (1945).