IPI International Potash Institute
IPI International Potash Institute

Balanced fertilization, an integral part in quality management of crop production

Presented at the Research Institute of Crop Production Prague
50th Anniversary Conference

Crop Science on the verge of the 21st century - opportunities and challenges

September 11-13, 2001, Prague, Czech Republic

Balanced fertilization, an integral part in quality management of crop production

by Dr. A. Krauss.

Contents

Summary
Urbanization drives demand for food quality
Quality counts in the market place
What is quality?
Plant nutrition and food quality - what is the involvement of potassium?
Nutritional properties
Functional properties
Organoleptic properties
Hygienic properties
Environmental compatibility
Conclusion
References

Summary

Quality of food, feed and fibre refers to the value, which is attached to the product with respect to quality properties, namely nutritional properties, hygienic properties, organoleptic properties, functional properties and environmental compatibility.

Urbanisation together with higher income are major driving forces behind demand of quality crops. Urbanites usually look for more and diverse food such as fruits and vegetables, and more animal protein than their rural counterparts. Nutritional, hygienic and organoleptic properties play an important role when selecting the food. This benefits those producers who can supply quality food accordingly. Urbanites are also progressively more concerned by the environmental compatibility of the production of the crop when purchased for consumption.

Numerous field trials prove the beneficial effect of balanced fertilization with potassium on the quality of the harvested product. This refers in the same way to nutritional properties such as the content of protein, oil, vitamins and to functional properties. Crops with adequate supply of potassium also have a better appearance. Freedom from pests and diseases at balanced fertilization satisfies the demand for hygienic food. And lastly, higher yields at balanced fertilization leave less residual N in soils which could pollute the environment, a factor related to the environmental compatibility in production.

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Urbanization drives demand for food quality

FAO (2001) estimates that, by the year 2030, the proportion of the world's population living in towns will have grown to 61% compared with 40% in the 80ies and 48% today. The increase in urbanization will be greatest in developing countries (1980 <30%, 1999 40%, 2030 57%). In contrast, in developed countries, urbanization, already 74%, is expected to increase only slightly to 82% in 2030. The corresponding urbanization rate for the Czech Republic is currently 66% and will be 76% in 2030.

Fig. 1. Per capita supply of major food items as affected by urbanization
Per capita supply of major food items as affected by urbanization
data from 1997; source: FAOSTAT, 1998

Dietary habits alter with urbanization and income. In general, developed countries with their high proportion of urban people consume much more fruits, vegetables and meat than developing countries (figure 1). However, the trend in developing countries follows the industrialized world. Taking China as an example, the Ministry of Agriculture in Beijing estimated that the per capita demand for meat would increase from 28.2 (1995) to 50 kg in 2020 (MEI FANGQUAN, 1997). The demand for fruit would rise at a similar rate, from almost 31 kg to 50 kg in 2020.

As indicated in figure 2, with increasing income the diet shifts from low value subsistence crops like cereals and root crops towards animal protein, fruits and vegetables, and quality comes into picture. Ultimately, the wealthy 'high-tech' society spending less time on food preparation and eating habit looks for packed and processed food. Furthermore, the considerable public concern on nitrate in vegetative food, growth hormones and antibiotics in meat production or the cases of BSE in Europe increases the desire for safe food of 'bio' origin. The market share of bio-food although still rather small will grow. In 1997, the US market for organic products was $4 billion, up from $78 million in 1980; European consumers spend about $4.5 billion on organic products and Japan around $2 billion per year (SWEZEY & BROOME, 2000). And Sweden has set a goal of converting 20% of its farm acreage to organic farming by 2005 (IFA, 2000).

Fig. 2. Relationship between income and food habit
Relationship between income and food habit
after KERN, 2000

The recent years brought also a growing awareness of the critical role that the diet can play in a wide spectrum of diseases. KEEN & ZIDENBERG-CHERR (2000) refer to the antioxidant effects of vitamins C and E in human plasma which is prolonged in the presence of the phytochemical catechin, a phenolic compound found in fruits, vegetables, green tea, red wine and chocolate. There is also an increased public interest in functional food that may have a potential to lower body fat, cure gut maladies, provide gender and age-related medical needs, improve skeletal strength, lower cholesterol or improve the optical vision, etc. (KERN, 2000). Ingredients such as lycopene in tomato, allicin in garlic or isoflavones in soybean are associated with prevention or treatment of cancer, diabetes, hypertension, and heart disease (BRUULSEMA, 2000). Rice has been genetically modified to synthesize and accumulate beta-carotene (provitamin A) or to contain 3 times the iron content of conventional rice, i.e. factors involved in controlling eyesight and anemia, respectively (GOTO et al., 1999; GURA, 1999; YE et al., 2000).

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Quality counts in the market place

Irrespective of whether agricultural products are grown for the domestic market or for export, the quality of the produce determines success in the market. A survey in 7 European countries shows that quality, though largely a subjective property, is rated as the most important determinant of acceptability by 25% of consumers, followed by price (16%), brand name/reputation (14%) and freshness (9%) (figure 3) (TRAILL, 1999).

Fig. 3. Relative importance of product attributes in product choice
Relative importance of product attributes in product choice
after TRAILL, 1999

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What is quality?

According to ABALAKA (1999) ".an intrinsic property of food by which it meets pre-defined standard requirements. Determinants of food quality can be grouped into several properties. Food quality therefore refers to the value, which is subjectively or objectively attached to food with respect of quality properties."

     
  Nutritional properties  
   
Hygienic properties
FOOD QUALITY
organoleptic properties
   
  Functional properties environmental compatibility  

More detailed quality indicators were compiled by HÄRDTER & KRAUSS (1999), listing next to nutritional value also aspects of health, sensorial, suitability, socio-physiology, political-societal and ecological values.

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Plant nutrition and food quality - what is the involvement of potassium?

K in plants is a multipurpose highly mobile element, which is not incorporated in any organic compound. Its main functions and involvement are the following:

  • osmoregulation
  • stomata movement
  • cation/anion balance
  • phloem transport
  • enzyme activation
  • N metabolism

K has also a motor function in cycling nutrients for growth, i.e. nitrogen from the roots to the shoot and carbon from the source (shoot) to the sink (roots, storage organs like grains, tubers). K travels as counter-ion together with NO3 in the xylem to the shoot (MARSCHNER et al., 1996). Lack of potassium however, restricts the NO3 transport, which leads to nitrate reduction in the roots and accumulation of amino acids (Figure 4). This may signal via a feedback effect to the root to restrict further N uptake, which in turn lowers the N fertilizer use efficiency. More N remains in the rhizosphere that might be leached or volatilized. The plant cannot be forced to take up more N if K is in short supply.

Fig. 4. Nutrient cycling in plants as affected by potassium
Nutrient cycling in plants as affected by potassium
after MARSCHNER et al., 1996

Enzymatic stimulation of assimilation and its translocation and storage in form of starch or fat/oil, and the incorporation of inorganic N into organic compounds such as amino acids and ultimately protein are prerequisites of high quality plant products. Numerous IPI field trials have shown the beneficial effect of balanced fertilization on yield and quality, but also on stress tolerance.

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Some examples:

Nutritional properties

Wheat in India: In IPI on-farm demonstration plots, addition of potash to a basal NP treatment increased grain yield by 28%. At the same time, grain protein content was improved resulting in an increase of almost 40% in protein yield, sufficient to supply the needs of an additional 12 people per hectare. On this basis, the farmer would benefit financially. By spending 706 rupees on potash, he would earn an extra RS 3589 per hectare. Each rupee invested in potash would return more than 5 rupees. The better appearance of the grain from the treated plots gave a 10-20% bonus on the price.

Fig. 5. Effect of balanced fertilization on yield and profit of rape seed in Czech Republic
Effect of balanced fertilization on yield and profit of rape seed in Czech Republic
from BAIEROVA, 2000

Rape seed in Czech Republic: Applying adequate K (160 kg/ha K2O) increased the seed and oil yield of rape seed by 33% (figure 5). Balancing NP+K with Mg further increased seed and oil yield to 2.59 t/ha and 1.17 t/ha, respectively, which is 62 and 70% higher than the NP control (1.6 t/ha seeds and 0.69 t/ha oil). At the same time, the farmer earned an extra profit of more than 23'000 Kc/ha.

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Functional properties

Potato in Poland: Use of potash in addition to standard NP increased tuber yield by 27% and starch yield by 31% (figure 6). However, the highest tuber and starch yield of 38.9 t/ha (+36%) and 6.75 t/ha (+47%) were achieved when NP+K was balanced with magnesium and sulphur. This result also demonstrates the importance to apply 'balanced' fertilization in the true sense by adding all those nutrients, which are deficient, i.e. in Poland not only K to NP but also Mg and S.

Fig. 6. Tuber and starch yield of potato in Poland as affected by balanced fertilization
Tuber and starch yield of potato in Poland as affected by balanced fertilization
from ROGOZINSKA, 1999

Sugar beet in Hungary: The treatment with 120-100-200-36 kg/ha NPKMg resulted in 2% higher root yield, 9.2% higher sugar content and 14.1% higher sugar yield than the NP control (figure 7). To produce 100 t of white sugar, about 77 t more beets with low sugar content have to be transported and extracted than beets with high sugar content. The saving of energy when beets with high quality are produced is evident. Apart from that, at the best treatment (NPKMg), the farmer earned an extra profit of 49'300 Forint/ha. Comparable results were obtained in Poland, Czech Republic and Romania.

Fig. 7. Root and sugar yield of sugar beet in Hungary as affected by balanced fertilization
Root and sugar yield of sugar beet in Hungary as affected by balanced fertilization
from KULCSAR, 2000

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Organoleptic properties

Taste of vegetables in Russia: Applying adequate potash to cabbage increased yield by 20 t/ha to 90.8 t/ha and improved vitamin C content by 12% (PROKOSHEV, 1998). WIEBEL (1997) quotes results from China which show quadrupling of yield and 29% higher vitamin C content in chilli pepper with adequate K.

... and in China: Celery receiving adequate K had a nitrate content of 427 ppm, which was 27% lower than with unbalanced nutrition (HÄRDTER & KRAUSS, 1999). Potash helped to keep the nitrate content of celery within the limits established by the public health authority.

Taste of grapes in Bulgaria: With K and Mg on top of NP, yield of grapes increased by 4.78 t/ha over the NP control (11.11 t/ha). Concomitantly, the sugar content increased further by 0.6% units to 20.0% (NIKOLOVA, 2000).

Potato chips in Bulgaria: Potato trials in Bulgaria not only confirmed the trend seen in Poland with regard to tuber and starch yield. In addition, it could also be shown that the content of reducing sugar dropped from 0.56% at NP to 0.04% at NP+K+Mg (180-120-150-50 kg/ha N-P2O5-K2O-MgO) (NIKOLOVA, 1999). A low content of reducing sugar in potato tubers is the main prerequisite of tasty and bright coloured potato chips.

Storage loss of cabbage in Russia: Cabbage stored during 4 months showed a substantial loss in weight (35%) and serious incidence of spot necroses when unbalanced fertilized with NP only (figure 8). In contrast, balanced fertilization improved shelf-life (weight loss 27%) and reduced considerably the incidence of spot necroses. After 4 months, those heads had also a rather favourable K:N ratio of 1.18, whereas the cabbage heads at NP control contained substantially more nitrate (K:N 0.49). Comparable results were also found in carrots and red beet in Russia.

Fig. 8. Shelf-life and disease incidence of cabbage in Russia as affected by balanced fertilization

Shelf-life and disease incidence of cabbage in Russia as affected by balanced fertilization
PROKOSHEV, 1999

Fissures, cracks and lesions observed on K-deficient fruits and leaves not only offer easy access for invading pathogens but also put off potential consumers in the market. The appearance and thus the quality are poor, the farmer cannot sell his produce. Apart from K, deficiency of Ca and Boron also causes malformation of fruits, blossom end rot in tomato or melons, thus causing substantial loss in market value.

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Hygienic properties

Pests and diseases are often reasons for the rejection of imports. Microbial and mould contamination and pesticide residue account for about 24% of detained shipments of food imports into the USA.

Potash helps the plant to be more resistant. This message was brought forward by IPI at the recent IFA Agric. Conference in Barcelona (KRAUSS, 1999). The result of a review of 2450 references (PERRENOUD, 1990) was to show that correct balanced fertilization with potash resulted in a greater than 50% reduction in disease and pest incidence, and at the same time considerably higher yields. Nutrition has a substantial impact on the predisposition of plants. By affecting the growth pattern, the anatomy and morphology and particularly the chemical composition, the nutrition of plants may contribute to an increase or decrease in the resistance and/or tolerance to pests and diseases.

Higher resistance to pests and diseases also means better appearance of agro-products on the market and lower production costs due to less need for agrochemicals to protect the plant. The latter would also lower the risk of residual pesticides causing rejection by the market.

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Environmental compatibility

The consumer, especially in developed countries, becomes more and more suspicious on how the food had been produced. He not only looks for affordable and good quality food but also for 'safe' food. He wants to follow-up the production, whether environmentally friendly and resource saving methods have been used. Quality auditing could add a particular image to the produce, the added value would increase the competitiveness at the market.

Fig. 9. Residual nitrate in subsoil after harvest of cabbage as affected bt fertilization practice in China
Residual nitrate in subsoil after harvest of cabbage as affected bt fertilization practice in China
HÄRDTER & KRAUSS, 1999

In this context, IPI trials in China showed that when subsoil nitrate contents after vegetables (cabbage) decreased drastically, the more balanced nutrition becomes (figure 9). Under farmer's practice, some 140 kg/ha nitrate-N was measured in subsoils, and farmer's practice in China means N first of all. The NO3-N content decreased to about 100 kg/ha after adding K to high N. It declined further to less than 40 kg/ha NO3-N when N was well balanced with potassium. Those farmers applying balanced fertilization can proof that:

  1. plants have been fertilized in a 'balanced' and thus 'natural' way because of less residual N in soil
  2. the natural resources land, fertilizer and energy - contained in fertilizers - have been utilized efficiently because of higher yields
  3. less residual nitrogen means less potential contamination of groundwater and the atmosphere.

Apart from higher profit, the farmer using balanced fertilization could claim an extra bonus for environmentally compatible production.

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Conclusion

In an era of globalization, certification schemes for quality and environmentally sound production processes, free trade and a multiple choice of the consumer in the market, agriculture has to respond accordingly. The consumer wants a transparent production to be sure to get 'safe' food. He wants to follow-up how the food is produced, whether environmentally friendly and resource saving production methods are applied.

Balanced fertilization, which takes care on all nutrients according to site and crop-specific needs to assist the farmer to comply with the demand from the consumer. His crop is healthy and of good quality. Higher yields at balanced fertilization indicate better use efficiency of the natural resources land and energy in form of fertilizers and transport. It also protects the environment by better utilization of applied nutrients. Less processing energy at high contents of nutritive ingredient goes also conform to the request of resource saving food production.

Ultimately, a farmer who is producing high quality food is competitive at the market. This ensures his income and his inclination to invest again in soil fertility in form of fertilizers. However, this requires that he will be informed on the latest development in plant nutrients related research. IPI intends to bridge the gap in knowledge by conducting demonstration trials as well as seminars, workshops, etc. Publications in local languages also assist to disseminate the information.

There is also need to inform decision-makers and politicians on the benefit of balanced fertilization. They have to provide the correct policy frame in terms of regulative measures to ensure availability of inputs at affordable costs and, at the same time, an appropriate market structure to sell his produce at fair prices.

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References

Abalaka, J.A. (1999): Assuring food quality and safety: Back to the basis-quality control throughout the food chain. FAO/WHO/WTO Conf. on Int. Food Trade beyond 2000, Melbourne, Australia, 11-15 Oct. 1999.

Baierova, V. (2000): IPI Co-operator Report, Institute of Crop Production, Prague-Ruzyne, Czech Rep.

Bruulsema, T.W. (2000): Functional food components: a role for mineral nutrients? Better Crops 84(2), pp. 4-5.

FAO (2001): Food and Agriculture Organization Rome, Italy.

FAOSTAT (1998): Food and Agriculture Organization Rome, Italy, statistics.

Goto, F., Yoshihara, T. and Shigemoto, N. (1999): Iron fortification of rice seed by the soybean ferritin gene. Nature Biotechnology 17: 282-286.

Gura, T. (1999): New genes boost rice nutrients. Science 285: 994-995.

Härdter, R. and Krauss, A. (1999): Balanced fertilization and crop quality. IFA Agric. Conference on Managing plant nutrition. Barcelona, Spain, June 29-July 2.

IFA (2000): International Fertilizer Industry Association, Paris, France, Organic farming, seeking the mainstream. April 11.

Keen, C.L. and Zidenberg-Cherr, S. (2000): What are the best strategies for achieving optimal nutrition? California Agriculture, Sep-Oct 2000, pp. 12-18.

Kern, M. (2000): Future of agriculture. Global dialogue EXPO 2000, the role of the village in the 21st Century: crops, jobs and livelihood. August 15-17, 2000, Hanover, Germany.

Krauss, A. (1999): Balanced nutrition and biotic stress. IFA Agric. Conference on Managing plant nutrition. Barcelona, Spain, June 29-July 2.

Kulcsar, L. (2000): IPI Co-operator Report, Sugar Beet Research Institute Sopronhopacs, Hungary.

Marschner, H., Kirkby, E.A. and Cakmak, I. (1996): Effect of mineral nutritional status on shoot-root partitioning of photo-assimilates and cycling of mineral nutrients. J. Exp. Botany 47: 1255-1263.

Mei Fangquan (1997): Expectations and strategies for food security in China by the early 21st century. 65th IFA Annual Conference, Beijing, China, 19-22 May.

Nikolova, M. (1999): IPI Co-operator Report. N.-Poushkarov Institute of Soil Science and Agroecology, Sofia, Bulgaria.

Nikolova, M. (2000): IPI Co-operator Report. N.-Poushkarov Institute of Soil Science and Agroecology, Sofia, Bulgaria.

Perrenoud, S. (1990): Potassium and plant health. IPI-Research Topics No. 3, International Potash Institute, Basel, Switzerland.

Prokoshev, V. (1998): Internal IPI report.

Prokoshev, V. (1999): Internal IPI report.

Rogozinska, I. (1999): IPI Co-operator Report, Academia Technicz Rolnicza/ Bydgoszcz, Poland.

Swezey, S.L. and Broome, J.C. (2000): Growth predicted in biologically integrated and organic farming. Cal. Agric. Vol. 54 (4), pp. 26-35.

Traill, W.B. (1999): Prospects for the future: Nutritional, environmental and sustainable food production considerations - changes in cultural and consumer habits. FAO/WHO/WTO Conference on Int. Food Trade beyond 2000, Melbourne, Australia, 11-15 Oct.

Wiebel, J. (1997): Potassium and the nutritional value of fruits and vegetables. In: Proc. IPI Regional Workshop on 'Food security in the WANA region, the essential need for balanced fertilization', Bornova, Izmir, Turkey, 26-30 May, pp. 224-238.

Ye, X., Al-Babili, S. and Kloti, A. (2000): Engineering the provitamin A (beta-carotene) biosynthetic pathway into (carotenoid-free) rice endosperm. Science 287: 303-305.

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