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Presented at the

8th AFA International Annual Conference

29-31 January 2002, Cairo, Egypt

Soil potassium mining in the WANA region, a matter of concern?

by Dr. A. Krauss, Director, International Potash Institute, IPI, POB 1609, CH-4001 Basel, Switzerland
Tel +41 61 261 29 22; Fax +41 61 261 29 25; e-mail: ipi@ipipotash.org; www: www.ipipotash.org

Contents

The agronomic feature of WANA
What are the consequences for crop production and nutrient management?
Fertilizer use and nutrient balances in the WANA region
What are the consequences of extended soil K mining?
Conclusions
References

The agronomic feature of WANA

Characteristic to the WANA region, which comprises the countries of West Asia and North Africa, is the following:

  • The population is steadily growing. It almost doubled every 25 years from about 143 million in 1960 to currently 400 million and will increase further to almost 600 million in 20 years from now (FAOSTAT, 2002). Compared to Asian regions and Latin America, the WANA region has the highest relative population increase, only surpassed by Sub-Saharan Africa.
  • The share of people living in urban areas rapidly increased from 32% in 1960 to currently 60% and will increase further to almost 70% in 2020 (Figure 1). In this context, PINSTRUP-ANDERSEN et al. (1999) also projects that the annual income will increase in the next 20 years with a growth rate of 3.83%, which is less than in other Asian regions like East Asia (5.12%) but higher than the global mean of 2.64%.
Figure 1: Demographic evolution in the WANA region
Figure 1: Demographic evolution in the WANA region
  • The cultivated land area (arable land and permanent crops) increased in the last 40 years only slightly to about 100 million ha (Figure 2). Compared to the rapid demographic development, it means that land availability declined in the last 40 years from 0.6 ha per capita in 1960 to currently 0.25 ha.
Figure 2: Availability of cultivable land (arable and permanent crops) in the WANA region
Figure 2: Availability of cultivable land (arable and permanent crops) in the WANA region
  • The countries of the WANA region are exposed to arid/semi-arid climatic conditions, i.e. evaporation exceeds precipitation. Irrigation is therefore mandatory when high land productivity is expected. The total area under irrigation nearly doubled in the last 40 years from 15 to 28 million ha. This represents an average share of 28% of the cultivated land (arable land and permanent crops). However, the share of irrigated land in individual countries differs substantially and ranges from 7 to 8% in Algeria and Tunisia, 30 to 40% in Israel, Iran and Saudi Arabia to 100% in Egypt. Although water withdrawal in developing countries for agricultural use is expected to increase further, the share will decline within the next 25 years from almost 90 to nearly 70% due to increasing competition for domestic and industrial use.
  • Cereals dominate the crop spectrum and occupy about 40 million ha (Figure 3). Although the area under cereals hardly changed in the last 40 years, the cereal production more than doubled from 34 to 78 million tons. This indicates a substantial achievement in raising the yield level. Scarcity of cultivable land will force the agriculture to increase yields further in order to meet the demand. However, in order to balance the demand for cereals, the WANA region had to import progressively more cereals, which rose from 6 million tons in 1961 to currently 54 million tons, representing $7.2 billion. PINSTRUP-ANDERSEN et al. (1999) expects that the need to import cereals will increase further.
Figure 3: Sectrum of annual crops in WANA (2000)
Figure 3: Sectrum of annual crops in WANA (2000)
  • In contrast to cereals, the area with fruits and vegetables increased in the last 40 years by 80 and 115%, respectively. Even more impressive is the progress in fruit and vegetable production of the WANA region, which trebled output of fruits and quadrupled production of vegetables during the same period of time (Figure 4). Interestingly, although the domestic demand increases according to a growing population, the WANA regions is in the position to export some 2 million tons fruits and vegetables (net export), which represents currently a value of about $2.2 billion.
Figure 4: Evolution of production of selected crops in WANA
Figure 4: Evolution of production of selected crops in WANA
FAOSTAT, 2002

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What are the consequences for crop production and nutrient management?

  • More people need more food. To achieve self-sufficiency in cereals and to lower the financial burden for import of cereals, its production has to be increased. Due to scarcity of land and water, the required higher cereal output can only be obtained through higher yields. With increasing yields, the nutrient uptake increases as well, which challenges the nutrient supply from the soil. As shown in figure 5, in rice, for instance, K uptake increased with yield. Nevertheless, even when applying 66 kg/ha K (80 kg K2O), the K uptake exceeded potash use, the K balance remained negative.
Figure 5: Rice yield and K balance as affected by fertilizer use
Figure 5: Rice yield and K balance as affected by fertilizer use
DOBERMANN, 1999
  • Increasing urbanisation affects crop production and nutrient management differently: (i) together with the food, nutrients are transferred into urban centres where the nutrients are deposited and thus lost, and (ii), with urbanisation, the diet changes and quality becomes an important determining factor in selecting the food. The nutrients transferred into towns are usually not recycled and have to be replaced by nutrients from fertilizers. Furthermore, changing diet pattern towards vegetables, fruit and animal protein has its impact on the crop spectrum. Vegetables are in general more nutrient demanding than cereals.
  • With irrigation, cropping intensity and yields increase, fallow periods disappear. This again challenges the nutrient supply from the soil.
  • Export of fruits and vegetables as an important foreign exchange earner in the WANA region requires top quality and freedom from pests and diseases, at the same time, nutrients are exported as well, which has to be replenished.

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Fertilizer use and nutrient balances in the WANA region

Use of mineral fertilizers in the WANA region increased steadily from a meagre 0.52 million t (Mt) in 1961 to currently 6.6 Mt NPK (Figure 6). About 2/3 of the applied nutrients consist of nitrogen, 25-30% of P2O5 and 5-7% of K2O.

Figure 6: NPK consumption in WANA
Figure 6: NPK consumption in WANA
FAOSTAT 2002

Accordingly, fertilizer use is highly unbalanced with a very wide NK ratio of 1:0.1. However, the individual countries vary substantially in the NK ratio in fertilizer use (Figure 7). Turkey and Egypt, the biggest fertilizer consumers, apply N and K in a ratio of around 1:0.05 (mean 1997-99). Iran improved considerably within the last few years the NK ratio of 1:0.04 in 1997 to a current ratio of 1:0.23 (1999). Morocco (1:0.32) and Israel (1:0.59) have a fairly balanced NK ratio, Algeria even a very close ratio (1:0.77, average 1997-99). These figures compare with the ratio by which plants absorb N and K. Cereals absorb both nutrients in almost equal quantities (NK ratio 1:1), vegetables and tuber crops take up even more K than N.

Figure 7: N:K ratio in fertilizer use in selected countries of the WANA region in relation to nutrient uptake by crops (fertiliser use mean 1997-99)
Figure 7: N:K ratio in fertilizer use in selected countries of the WANA region

Highest N rates of 296 kg/ha are applied in Egypt. Use of P2O5 is highest in Lebanon with 104 kg/ha whereas the highest K use is seen in Israel with 83 kg/ha K2O (figure mean of 1997-99, FAOSTAT, 2002). On average, the countries of the WANA region apply 39 kg/ha N, 16 kg/ha P2O5 and 3 kg/ha K2O.

When the fertilizer use is compared with the nutrient removal by crops, it shows the following picture:

  • Until the middle of the eighties, N removal by crops exceeded N use by mineral fertilizers. The resulting negative N balance indicates soil N mining (Figure 8). After that period, N use by mineral fertilizer was in the same quantity or slightly exceeded N removal by crops. N balance became positive at a level of 2-5 kg/ha.
Figure 8: N removal by crops in relation to N use in WANA
Figure 8: N removal by crops in relation to N use in WANA
  • The P balance shows a fairly similar development over time as the N balance, i.e. from a slightly negative balance in the 70ies and early 80ies to a positive balance with about 5 kg/ha P2O5.
  • The evolution of the K balance differs substantially from N and P. K removal by crops exceeds by far the K use by mineral fertilizers (Figure 9). The resulting K balance decreases almost linearly from -20 kg/ha in 1970 to currently -37 kg/ha K2O (mean 1997-99) (Figure 10). The total annual K deficit exceeds 3.6 million tons K2O. This indicates severe soil K mining and loss of soil fertility.
Figure 9: K removal by crops in relation to K use in WANA
Figure 9: K removal by crops in relation to K use in WANA

Figure 10: Apparent nutrient balance in WANA
Figure 10: Apparent nutrient balance in WANA

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What are the consequences of extended soil K mining?

  • Sustainability of soil fertility: After exhausting the fraction of easily available K in soil at inadequate or omitted potash use, the plant has to rely on K released from the less readily available fraction of non-exchangeable K. However, the release rate of K from the non-exchangeable fraction is much smaller than from the exchangeable fraction (Figure 11). A high yielding crop absorbs K in a rate of up to 10 kg K2O/ha/day. Failing to match K release from the soil into the solution with the demand of the crop restricts yield formation. The more the plant has to rely on K release from the non-exchangeable fraction, the lower becomes the yield.

    Figure 11: Effect of soil K mining on the soil K status and K release intensity
    Figure 11: Effect of soil K mining on the soil K status and K release intensity
    after CHENG MINGFANG et al., 1999

    Simultaneously, with depletion of the readily available K fraction, the clay minerals start to fix potassium, which makes soil K less available. The same applies to ammonium (Figure 12). Plants cultivated on K fixing soils require a much higher potash supply than on non-fixing soils and thus, have higher production costs. NH4 fixation of K depleted soils lowers the N fertilizer use efficiency, which is also a cost factor.
Figure 12: NH4- Fixation in soils as affected by the K status
Figure 12: NH4- Fixation in soils as affected by the K status
after MERBACH et al., 1999
  • Yield and income: Numerous field trials in the WANA region showed significant yield responses of a wide range of crops to potash applications. EL HADI and ETOURNEAUD (1995) could demonstrate already in the early 90ies that use of 60 kg/feddan K2O increased in the Nile delta of Egypt yield of berseem, cotton, beans and several cereals by 4 to almost 10% although those soils contain up to 500 ppm exchangeable potassium. Similar results were obtained in Upper Egypt. BADRAOUI et al. (1997) showed with sugar beet that investing one $ in potash returned up to eight $ through higher yield. Also IPI-sponsored field trials with a wide range of crops and soil types in different countries proved the profitability of potash.
    Yield reduction at insufficient potash supply is synonymous to loosing opportunity yield and income (Figure 13). The farmer could obtain higher yields and income with adequate potash supply. At the same time, use efficiency of other inputs decreases as well. Therefore, insufficient supply of potash leads to waste of natural resources such as land, water and energy, it is a threat to the environment at inefficient use of N and P fertilizers and reduces the profit of the farmer.
Figure 13: Loss of opportunity yield on K depleted soils
Figure 13: Loss of opportunity yield on K depleted soils
after MERBACH et al., 1999
  • Quality and competitiveness: Quality of agricultural products became the dominant factor in selecting food at the market. Quality can be expressed according to the nutritive value, hygienic and organoleptic properties, the functional properties, and the compatibility with the environment at its production. Due to its multi-functionality in the plant, potassium is considered as the nutrient being most involved in quality production. Higher protein content in wheat, oil content in soybean and groundnut, fibre content in cotton, better shelf-life of fruits and vegetables are some of the findings from field trials with potash (Figure 14). AGBANI et al. (1999) reported from Morocco, that applying 150 kg/ha N and 300 kg/ha K2O has proved to be the most effective combination for the highest extractable sugar content.

    Figure 14: Impact of balanced fertilization with K and Mg on yield and quality of sugar beet
    Figure 14: Impact of balanced fertilization with K and Mg on yield and quality of sugar beet
    IPI trials, Hungafy 2000

    Each percent sugar less in sugar beets requires about 6% more beets to be transported and extracted to yield the same amount of white sugar. The higher energy consumption and lower profitability in extracting low quality beets are obvious. Furthermore, the higher content of noxious N in sugar beets at unbalanced fertilization with inadequate potash lowers in addition the sugar extraction.
    Farmers being paid according to the quality will loose their competitiveness at the market when producing crops with inferior quality. Lower procurement prices for crops poor in nutritive value shrink his income and profit from farming.
  • Stress tolerance: Plants inadequately supplied with potash are more susceptible to pests and diseases (Figure 15) and vulnerable to climatic and soil-borne stress. Less pest and disease incidences at balanced fertilization reduce the need for agrochemicals, reduce the storage losses, especially in fruits and vegetables, and the marketable crops have a better appearance. This lowers the production costs and increases the competitiveness at the market when offering healthy and safe products. One should also not forget that in an age of globalization and liberalized international trade, quality such as freedom from pests and diseases became an important non-tariff trade barrier. In not complying with the hygienic standards set by the importing country, the market is quickly lost.
    Variable yields when plants are vulnerable to climatic and soil-borne stress are not only a financial risk for the producer but also impair the planning of the food supply of the nation.
Figure 15: Pest incidence in soybean as affected by K fertilization
Figure 15: Pest incidence in soybean as affected by K fertilization
IPI trials in India, 2000
  • Compatibility with the environment: Consumers will ask more than before whether food is produced in accordance with the environment. This refers in particular to agricultural products. The rapidly increasing market of so-called ‘bio’-product gives evidence on this development.
    DOBERMANN (1999) showed in field trials with rice that the recovery efficiency of N increased from 26% at low K (20 kg/ha K2O) to 36% at adequate K (80 kg/ha K2O). This means that less N is left in the rooting zone at adequate K supply, which otherwise could pollute the groundwater when leached or contribute to global warming when volatilized. A higher N fertilizer use efficiency, less pest and disease incidences at balanced fertilization with adequate potash comply with the requirement of safeguarding the environment in agricultural production.

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Conclusion

Soil potassium mining in the WANA region, a matter of concern? Certainly, all stakeholders in agricultural production should be concerned, the farmers, the fertilizer sector and the public including the consumers, environmentalists and decision-makers.

The farmer: balanced fertilization with adequate potash warrants sustainability of soil fertility, and higher income through better yield and quality. Potash is also a crop insurance against natural and man-made calamities, such as drought, salinity, pest or disease. With higher income, he spends more money for non-agricultural products, this attracts other business in the rural region, which creates jobs and contributes to social security. The better quality and less need for agrochemicals gives him advantages at the market, he complies with the public expectation of healthy and safe food. And last but not least, balanced fertilization protects the environment.

The fertilizer industry benefits from a better fertilizer use efficiency at balanced nutrition. Less N and P remain in the rooting zone, which means less potential environmental threat. Utilizing and promoting the benefits of balanced fertilization contributes to improve the image of an industry, which will always be under close observation by environmentalists in particular.

The public: the consumers of agricultural products can feel safe when purchasing high quality products also from conventional farms when balanced fertilization according to site specific needs is adopted. This gives him the confidence to trust not only the product he buys, but also to trust the producer. The consumer will find that, with balanced fertilization, the crop production is environmentally sound and complies with the need to economize the use of natural resources. With this trust, the consumer will be willing to pay adequate prices also for conventionally produced food.

It is time that the decision-makers, and with them the public, pick up the message.

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References

Agbani, M., Badraoui, M. and Soudi, B. (1997): Effects of potassium and nitrogen on sugar beet yield and quality in the Doukkala region in Morocco. In: Proc. Regional Workshop of IPI on ‘Food security in the WANA region, the essential need for balanced fertilization’, May 26-30, Bornova, Izmir/Turkey, pp. 203-212.

Badraoui, M., Agbani, M. and Soudi, B. (1997): Potassium status in soils and crops, recommendations and present use in Morocco. In: Proc. Regional Workshop of IPI on ‘Food security in the WANA region, the essential need for balanced fertilization’, May 26-30, Bornova, Izmir/Turkey, pp. 115-124.

Cheng Mingfang, Jin Jiyun and Huang Shaowen (1999): Release of native and non-exchangeable soil potassium and adsorption in selected soils of North China. Better Crops International, Vol. 13 (2), pp. 3-5.

Dobermann, A. (1999): Reversing diminishing growth of rice yields in Asia. 67th Annual Conference of the International Fertilizer Industry Association, IFA, May 17-20, Manila, Philippines.

El Hadi, A. and Etourneaud, F. (1995): From natural manuring in the days of the Pharaohs to modern nutrient management with fertilizers since the High Dam. In: International Fertilizer Correspondent Vol. 36, 3/1995. International Potash Institute, Basel, Switzerland.

FAOSTAT (2002): Statistic Website Food and Agriculture Organization, FAO, Rome, Italy.

Merbach, W., Schmidt, L. and Wittenmayer, L. (1999): Die Dauerdüngungsversuche in Halle (Saale). B.G. Teubner, Stuttgart-Leipzig, pp. 56-65.

Pinstrup-Andersen, P., Pandya-Lorch, R., and Rosegrant, M.W. (1999): World food prospects: Critical issues for the early twenty-first century. IFPRI, Washington DC, USA.

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