Potassium Research and Agricultural Production - The International ...

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(c) Nigeria, savanna zone (Healhcole [/5}). Response or cereals to potassium, grown in rotation maize, sorghum and groundnuts Kano Sorghum Maize Mok .... a Maize (Block 1) Muize (Block 2) Groundnuts Years or rotation Maximum yield, kg/ha Maximum K response kg/ha Years of rotation Maximum yield. kg/ha Maximum K response. kg/ha Years of rotation Maximum yield, kg/ha Maximum K response, kg/ha Years of rotation Maximum yield, kg/hu Maximum K response, kg/ha Years of rotation Maximum yield, kg/ha Maximum K response, kg/ha 2 1600 + 772 1270 + 125 3290 + 309 2 3280 + 1282 2620 - 95 4 2110 + I 188 4 3860 + 1085 3 2600 + 1420 4 3880 + 1541 5 820 + 107 (d) Ivory Coast. northern and southern savanna zone (Niakaramandougou and Katiola respectively) and forest zone (Yamoussoukrou) (Dial [7}) Year Niakaramandougou Katiola Yamoussoukrou Yields of cotton in successive years in plots given N. P and S fertiliser, as percentage of those in plots receiving N, P, Sand K 96 91 96 2 92 90 94 Thus it is quite clear that any significant extension of the cropping period must be accompanied by appropriate use of Fertilisers, if yields are to be maintained at reasonable levels. The only exception is that as far as nitrogen is concerned the situation may be somewhat changed if legumes with active Rhizobia in root nodules are included amongst the crops. The effects of long term additions of P and K to many tropical soils are very inadequately understood. It seems to be the more general rule that phosphorus is only weakly adsorbed and subsequently slowly available, rather than irretrievably 'fixed' by iron and aluminium oxides (Greenland [12]). Hence it may be that continued use will tend to build levels of soil phosphorus where rates of Fertiliser application can be reduced. With potassium less is known, but the existing evidence indicates that leaching losses are relatively large (Bollon [4J .. GodeJroy, Muller and Roose [11]) so that low or negligible residual effects are obtained (Boyer [5J). The amounts of nutrients added to the 3 85 69 82 4 84 62 58 5 77 319
soil when a woody natural fallow is cleared are an order of magnitude larger than the rates of fertiliser usually considered necessary for arable crops (table 5) but whether these large amounts are available to crops for more than one or two seasons has not been adequately established. The limited data obtained from following soil changes at one site (table 6) and from Iysimetry (&Iton (4] and Godefroy, Muller alld Roose (IIJ) suggest that because leaching losses of potassium are rapid and large in the more humid areas, potassium requirements of the high yielding varieties of maize as well as root and tuber crops might not be fully met even as little as two years after clearing. The results collected in Table 7 show that, for a range of soil types, potassium, as well as nitrogen and phosphorus, is essential to any extension of the cropping period beyond two or three years in the forest areas, and is likely to be necessary in all areas whenever longer cropping periods are established. When shortened vegetative fallows are used, the onset of potassium deficiencies may be delayed for a few cycles of the system, but must eventually arise if substantial export of food or cash crops occurs. 2.3. Reduction of the fallow period In most instances when population increases and requires a greater intensity of land use, it is the fallow period which is reduced, rather than the cropping period extended. Several examples are given by Prothero {27J. The commonest reason for this is that the labour involved in weeding is a determining factor, and this combined with falling yields usually makes it preferable to abandon a plot and open fallow land even though it is not adjudged ready for fresh cultivation. The reduction in the fallow period means that the total bulk of the fallow vegetation is less, the nutrients immobilised in it and released on burning are less, and soil organic matter will not have been built to as high a level as after a longer fallow. It may also mean that nutrients in the vegetation have not been withdrawn from as great a depth in the soil as when the fallow persists for longer. For a short cropping period, with low yielding varieties, this may introduce no obvious problems, as the potassium may well not be a limiting factor in such circumstances. As leaching losses of potassium tend to be very large in the forest areas, it may in some respects be wasteful to have forest fallows of 20 years or more, which accumulate over 500 kg/ha of potassium (table 5) and release it immediately on burning. There is too little data available to give good evidence of the rate of leaching of potassium from soils following clearing and burning of forest fallows, but sufficient to suggest that shortening the fallow period will often provide sufficient potassium for a few years of cropping, while reducing losses from the soil-plant system due to leaching. Natural fallows develop most rapidly when the cropping period is short, and initial clearing and subsequent weeding are inefficient. Their great advantage is that they develop through the existing crop, and the essential in erosion prevention of keeping a cover on the soil is observed. They also involve no labour in establishment. If the cropping period is prolonged and production techniques during the cropping period improved, they do not necessarily develop so rapidly when the land is abandoned, nor are they necessarily very efficient in terms of extraction of plant nutrients from subsoils or nitrogen accretion. Intensification of the system must therefore also be considered in terms of replacing the natural fallow by a planted fallow. 320
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Potassium Research and Agricultural
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Chaudet, P. 1st Working Session SOD
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Drouineau, G. Mathieu, M. Mafavofta
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Chairman: Co-ordinator: 1 si Workin
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of the agricultural wage-earners wa
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for certain industrial crops a mino
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expected to produce fertilizer type
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Organization and Achievements of Ag
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Research expenses are distributed a
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vigorously cultivated. The intensiv
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It became clear that in Congresses
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this balancing effect. On the other
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problems were studied by field and
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There is need to relate fertiliser
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Increase in the fertilisers used in
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are easier to use than three separa
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of workers, preferably associated b
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Chairman: Co-ordinator: 2 nd Workin
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Accordingly, K release increases fr
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ways satisfactory. If the greater p
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The Use of Reagents Containing Sodi
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tiated by the cultivation practices
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terial being an eruptive or crystal
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G. Dut/lion, C. and Grosman, Ruth:
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Potassium Fixation and Assessment o
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The quantitative and qualitative di
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Table 6. Average dry matter yield i
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tons in 1960 in Hungary. Rapidly in
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Bibliography I. KOIak. M.: Study of
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Interaction of Potassium, Magnesium
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3.3. Influence 0/ K, Alg alld Ca do
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Table 8. (Lehmann. Malysirlk (15])
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the magnitude of these reserves may
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than a plant rich ill carbohydrates
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form. Up to now wc do not know of o
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Improvement of potassium nutrition
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ATP Synthesis and Assimilate Transp
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38 36 32 30 28 26 r Fig. J. x y •
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Potassium and the Nutritive Balance
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account of the unfavourable results
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thorough understanding of the funct
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Table 4. Nand K contents in milligr
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In our view the fact that the K ion
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[29]), suggesting that the K defici
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eral sites permitting hydrogen-bond
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Ions may be appreciably retransloca
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would suggest that translocation is
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Absorption and Lateral Transport of
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cells and intracellular ,K+ activit
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a value between the optimum and 1.0
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the optimum (2.34%). Leaves affecte
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!, 42 0,2u QII: laD l,Ra VfMl /91a
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During the course of the years as t
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Or. A. Vakhimstrov pointed out the
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Summary Assessment of Potassium Fer
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population the same imbalanced situ
Page 249: Table 6. Responses of rice in soil
Page 253: Table 10. Effect of potassium on th
Page 259 and 260: 12. Groundnut Groundnut is generall
Page 261: Such a heavy production per hectare
Page 266 and 267: sic primary minerals such as felspa
Page 268 and 269: tween yield and K content of leaves
Page 270 and 271: soils cannot therefore give any val
Page 272 and 273: Summary Recent Developments of K Fe
Page 274 and 275: 5 FiK. 1. Soil regions of Latin Ame
Page 276: N ... '" 7. Lower Amazon and J lowe
Page 280 and 281: Table 2-3. Quantities of elements e
Page 285: Ratio 1973 Time Fig. 5. Trends in r
Page 292 and 293: Summary Intensification of Agricult
Page 295 and 296: w ..,. Relative yield 100 " 80 70 5
Page 297 and 298: agement practices, and without natu
Page 302: 2.4. Improved ·/allows' If a plant
Page 305 and 306: Report of the Co-ordinator of the 4
Page 307 and 308: eached where the land is continuous
Page 309 and 310: Chairman: Co-ordinator: 5 th Workin
Page 311 and 312: kg/ha 5000 4000 3000 2000 1000 o Ge
Page 313 and 314: Pollution caused by fertilizer is t
Page 315 and 316: Thus, even relatively high nitrate
Page 317: Table 4. Distribution of the potass
Page 321: The Table shows, that even sand fro
Page 324: This indicates that potassium uptak
Page 328 and 329: 6. Vollen'lf.'cidcr Rich.A.: Scient
Page 330 and 331: Report of the Co-ordinator of the 5
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