IPI International Potash Institute
IPI International Potash Institute

Quality production at balanced fertilization: the key for competitive marketing of crops

12th CIEC International Symposium on

Role of fertilizers in sustainable agriculture

August 21-22, 2000, Suceava, Romania

Quality production at balanced fertilization: the key for competitive marketing of crops

by A. Krauss


Population growth and urbanization demand for more and better food. The diet also becomes more diverse with higher demand for vegetables and fruits. At the same time, with higher income, the quality consciousness of the urban population increases as well. Quality is considered by consumers as the most important determinant of acceptability and rated higher than price, brand name, reputation or freshness.

Quality refers to the value, which is subjectively or objectively attached to food with respect to nutritional properties, organoleptic properties, hygienic properties and functional properties. As an additional criterion in quality judgement comes into picture whether environmentally sound procedures were observed and applied in production of the food items.

Numerous on-farm trials within IPI projects proved that balanced fertilization helps the farmer to produce food, which fulfills the different quality criteria. Balanced fertilization also safeguards natural resources and contributes to protect the environment.

Adopting quality management in concert with an 'environment management', the farmer benefits from balanced fertilization with a better market chance, higher procurement prices and thus better income. This improves the purchasing power of the rural area; it attracts other business and creates jobs. The nation will ultimately benefit from balanced fertilization with a better social security, less migration, and last but not least, with better export opportunities of competitive quality products.


Urbanization drives demand for food quality

FAO (1999) estimates that, by the year 2030, the proportion of the world’s population living in towns will have grown to almost 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 81% in 2030.

The demographic trend in W-Europe is similar to that in the developed countries as a whole. Romania in comparison has still a rather high proportion of its population living in the rural area, however the share of people living in towns increases rapidly.

  Figure 1: Evolution of Urbanization
selected regions
year year
  data source: FAOSTAT '98  

Dietary habits alter with urbanization. In general, urbanites, having a higher income, eat more meat, fruits and vegetables than their rural counterparts. With urbanization, demand for these items naturally increases. Correspondingly, IFPRI estimates that the per capita demand for meat will increase by 5% till 2020 in developed countries, but in developing countries by 60% (ROSEGRANT et al., 1995). In Bangladesh for instance, cereals (83% of the total calorie intake) dominate the current average diet. Animal protein, fruits and vegetables including potatoes, accounting at present for less than 8% of the total energy intake, are expected to increase to 15% by the year 2020. At the same time, the share of cereals should be reduced to 55% of the total energy (BHUIYAN, 1998). India expects future growth in demand for wheat at 1.5%, but for vegetables and fruits 3.6 and 4%, respectively (DAYANATHA JHA & RAMESH CHAND, 1998).

Increased production of fruits and vegetables not only meets the domestic demand but, at the same time, creates export opportunities and thus generates higher income for farmers. Near East for instance increased during the last 20 years production of fruits and vegetables from about 57 million t to currently almost 100 million tons (FAO, 1998). Export of fruits and vegetables increased during this time from 4 to 6 million t, whilst the value of exports more than doubled with US$ 4 billion. East Europe used to have a net export of about 3 million t fruits and vegetables during the end of the eighties. In the meantime, E-Europe turned into an importing country, the decreased domestic production is certainly one of the factors responsible for this development. W-Europe in comparison has always been an important importer of fruits and vegetables (figure 2).

  Figure 2: Trade of fruits and vegetables in Europe  
year year
  data source: FAOSTAT '98  

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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).

  Figure 3: Relative importance of product attributes in product choice
survey of consumers in 7 European countries
  after TRAILL, 1999  

HAMMER (1999) from FAO says that "... in order to be a successful food exporter, a country must produce foods that are both sought after and be acceptable in quality. Compliance with the statutory, compulsory or mandatory requirements of importing countries is an unavoidable and essential prerequisite...".

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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

Nutritional properties are characterized by the content of certain constituents such as protein, oil/fat or starch, mineral components and vitamins. Content of fiber and ballast as well as the energy content are widely used parameters in human diet. The content of nutritive elements like protein or oil is used in many countries as a basis for procurement systems and thus is an economic factor.

Hygienic properties refer mostly to freedom from pests and diseases and their metabolic by-products, which might be toxic or initiate food allergy. Other aspects refer to contamination with nitrate or heavy metals, residues from agrochemicals. 'In a situation of globalization, trade liberalization and commitment to reduce tariffs and eliminate non-tariff barriers, sanitary and phytosanitary justification could be used as a means of introducing measures that are more protectionist than if they were only concerned with safety and health' (GONZALO RIOS, 1999).

Organoleptic properties are highly subjective. They describes the appearance, color, structure, smell or taste. The preference of many customers for a shiny dark red apple, compared to a yellowish or green one, is wellknown although there might be no difference in nutritive value.

Functional properties are related to the crops' suitability in processing like sugar content in beets or cane, starch in potatoes, content and spectrum of fatty acids in oil seeds. The resistance of crop plants to biotic and abiotic stress such as salinity, drought, heat and cold or the tolerance to weedizides as implanted into transgenic plants can be grouped into this category.

Environmental compatibility of production will become an important quality parameter used by consumers when selecting food at the market or for processors in their quality management. The rather rapidly expanding market with a growth rate of 25% p.a. for 'organic products' refers to the desire of consumers for 'safe' food. It is estimated that sales in this market will be in the order of about $20 billion and may represent within the next 5 years, 5 to 10% of the total food sales in some countries (ISHERWOOD, 2000).

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How to produce quality?

SINSAKUL (1999), from the Thai Industrial Standards Institute, stated that "...developing countries often find themselves defenceless when at the negotiating table dealing with issues of sanitation and quality of their agricultural products. This is because they often lack technical information...".

The International Potash Institute, IPI, is very much concerned to fill the gap in technical information with respect to quality production. The information and advice we disseminate derive from our on-farm trial programmes as well as results from other co-operating institutions. We concentrate attention on how the appropriate use of plant nutrients can ensure the production of top quality food.

Some examples:

Nutritive properties

Protein content of wheat. In Madhya Pradesh, India, IPI on-farm demonstration plots showed that 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.

Oil content in oilseeds. Applying adequate K (100 kg/ha K2O in split application) in Madhya Pradesh, India, increased the seed yield of soya by 26% and oil yield by 34% (figure 4). This represents an added net value of about US$ 120/ha in seeds or about $ 150/ha in oil and soybean cake. The higher oil yield also provides an additional 22 people with the annual allowance of 6.57 kg edible oil. As a further effect, soybean fed with balanced fertilizer showed considerably less incidences of girdle beetle, semilooper and aphids.

Other oilseeds also responded to K in India with higher oil yields. The oil yield from mustard in West Bengal doubled and net income increased by more than Rs 4000/ha at a VCR of almost 10. In Orissa, groundnut responded to K with oil output increased by 50-60% when the basal fertilizer was balanced with K. Net income and VCR of potash use was comparable with that of mustard in West Bengal.


Figure 4: Effect of balanced fertilization with potash on yield and quality of soybean in India
(IPI on-farm trials, mean of 3 years 1994-96)


Nutritive value 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 potassium.

Functional food components. These phytochemicals are defined as bio-active ingredients in food thought to support health and fitness. Lycopene in tomatoes, allicin in garlic or isoflavones in soybean belong to this group. They are associated with prevention or treatment of cancer, diabetes, hypertension, and heart disease (BRUULSEMA, 2000). Potassium may enhance for instance the content of lycopene in tomato. Soybean grown at different levels of potash showed an increased content of isoflavones in seed with higher seed K content (BRUULSEMA et al., 2000).

Organoleptic properties

Appearance of rice and wheat. In Orissa, India, rice yielded better with potash, a higher yield, with improved grain filling and larger seeds (higher thousand-grain weight). Wheat grains from K trials in Madhya Pradesh, India, got a bonus price because of the better appearance, i.e. more bold and shiny than seeds from control plots.

Appearance of potato. Potash increased in West Bengal the proportion of 'A' -grade tubers from 4 to 12%. Potash use was repaid by a profit of 14 to 19 rupees per rupee invested.

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.

Functional properties

Processing of potato. BANSAL & SHAHID UMAR (1998) reported from Uttar Pradesh, India, that supplying potato with adequate potash increased tuber yield and dry matter content. At the same time, for potatoes grown for processing, chip colour was improved and storage loss of fresh tubers was reduced. The latter is of particular economic importance because the market price of potatoes increases considerably in the weeks after harvest. As an example, during the season 1997-98 the price increased from Rs/kg 4.5 at harvest to Rs/kg 6 two weeks later and Rs/kg 8 four weeks later. This increased the VCR of potash from 16.6 at harvest to 21.4 and 28.5 two and four weeks later, respectively (at 150 kg/ha K2O as SOP).

Processing of sugar beet. Sugar beet in Hungary, receiving adequate potash, gave a higher root yield with increased sugar content and consequently a much higher sugar yield (KULCSAR & DEBRECZENI, 1997). The latter counts when quality-based procurement systems are established. Farmers in Germany earned an additional $140/ha from sugar beet at 360 kg/ha K2O in spite of higher fertilizer costs because, at adequate soil K levels, quality of beet improved and commanded a higher procurement price (figure 5) (ORLOVIUS, 1996a).

In Iran, sugar beet responded to potash application with higher yield and better quality (TEHRANI & MALAKOUTI, 1997). Boron and sulphur, in addition to recommended rates of NPK, achieved in Iran a further increase in sugar yield but not in root yield.

OEHLUND (1999) calculated that, in order to produce one ton of sugar from low quality beet (e.g. 80% extractability and 13% sugar content typical of unbalanced fertilization), about 10 t of roots would be needed. But, with high quality beet having 95% extractability and 17% sugar content, less than 7 tons would suffice. The savings in energy required to transport and extract 3 t of a lower quality beet is obvious.

  Figure 5: Effect of potash on quality of sugar beet and income
Germany, alfisols dev. from loess, Kesch.:180-220 mg/kg
  gross income DM/ha  
  kg K2O/ha  
  data from Orlovius, 1996  

Processing of sugar cane. Sugar cane in Egypt responded to increasing soil K content with higher yield and higher sucrose content in stalks. The same IPI on-farm trials also showed that increasing soil salinity had a deleterious effect on both the fresh weight of stalks and their sugar content. The decreasing sucrose content in cane stalks with increasing salinity derives from the fact that Cl, together with K, accumulates in the storage tissue where it raises the osmotic potential. This impedes sucrose transport into storage cells and competes with sucrose for storage space. Furthermore, Cl in storage tissue decreases the pool of plant potassium available for other metabolic functions in the plant (KRAUSS, 1991).

Fiber quality in jute. Fiber yield and quality in W-Bengal, India, was improved with balanced fertilization. Use of farmyard manure on top of NPK further increased yield.

Hygienic properties

Healthy potato. Correctly fertilized potatoes in Germany had a higher starch content as well as lower incidence of black spot (figure 6). The beneficial effect of potash on starch content of potato tubers was more pronounced with sulphate of potash than with potassium chloride. The higher starch content returned a higher sales price with a quality bonus of DM 205/ha (ORLOVIUS, 1996b; 1999).

Less nitrate in vegetable production. IPI on-farm trials in China showed that celery receiving adequate K had a nitrate content of 427 ppm, which was 27% lower than that with unbalanced nutrition (HÄRDTER & KRAUSS, 1999). Potash helped to keep the nitrate content of celery within the limits laid down by the public health authority.

Potash helps the plant to be more resistant, a factor related to hygienic properties. 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) shows that correct balanced fertilization with potash resulted, in more than 50% of the recorded cases, in a reduction in disease and pest incidence, and at the same time, in considerably higher yields. Nutrition of plants 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 agro-chemicals to protect the plant. The latter would also lower the risk of residual pesticides causing rejection by the market.


Figure 6: Relationship between K content of potato tubers and incidence of black spot on soils different in K status

  kg K2O/ha (in sulphate form)  
  source: Orlovius, 1996  

Environmental compatibility

IPI trials in China revealed that subsoil nitrate contents after vegetables (cabbage) increase drastically with unbalanced fertilization. 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 K (figure 7).


Figure 7: Residual nitrate in subsoil after harvest of cabbage as affected by fertilization practice
results from China

  source: HÄRDTER & KRAUSS, 1999  

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Nitrate in plants - is it a quality factor?

A factor widely used in judging food quality is its content of nitrate. The main public health concern about high dietary nitrate intake is that it may increase the risk of gastrointestinal cancer, and be a cause of infantile methaemoglobinaemia, the "blue baby syndrome".

Vegetables and fruits are the main sources of nitrate. In temperate zones where vegetables are grown under low light intensity, nitrate levels in vegetables can be high because nitrate reduction in leaves depends very much on light intensity. Unbalanced fertilization with inadequate potassium supply also leads to nitrate accumulation in plants. Drinking water can also contribute to the dietary nitrate intake, especially when N fertilizer use efficiency is low and thus NO3 is leached down to the groundwater.

How dangerous is nitrate in food?

LEIFERT et al. (1999) looked at the "Human health effects of nitrate". The potential risks of dietary nitrate are seen in context with gastrointestinal carcinogenesis. Because salivary nitrate is rapidly converted to nitrite, it was postulated that nitrite may nitrosate amines to form nitrosamines. Some nitrosamines were shown to be carcinogenic when fed to experimental animals.

However, studies, undertaken in an attempt to establish whether dietary nitrate is directly linked to gastrointestinal cancer, produced conflicting and often contradictory results. More recent experiments showed that nitrite from nitrate entering the normal acidic stomach appears to be rapidly converted to reduced N-forms which cannot nitrosate secondary amines.

On the other hand, there is "... growing evidence to suggest a beneficial physiological role of dietary nitrate in the gastrointestinal protection against food-borne pathogens including Helicobacter pylori which is increasingly recognised to be associated with gastric malignancy...". This belief is supported by the fact that dietary nitrate is recycled with the blood, actively concentrated in the saliva and repeatedly re-circulated through the stomach where, as mentioned earlier, nitrate is converted into nitrite. Addition of nitrite also controlled all food borne pathogens, which could survive acid treatments at pH 2 to 4, as commonly found in the stomach. Without additional bacteriocidal control through nitrite, such bacteria surviving low pH could re-grow and cause disease when reaching the neutral environment of the more distal intestine.

However, as Leifert and co-workers say "... although the apparent beneficial effects of nitrite (from nitrate) in the prevention of infectious diseases are likely to change the current negative perception of vegetable based dietary nitrate intake, the authors feel that a sensible limit for levels of nitrate in drinking water should be enforced. A rise in nitrate levels is a symptom of improper use of nitrogen fertilizers and poor agricultural management practice...".

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What is the link between potassium and product quality?

The positive impact of adequate potassium on quality can be regarded as a result of the nitrogen-potassium interaction in plants. This partnership in the control of quality starts in the root. Under non-saline conditions, NO3 accumulates in roots and is taken up by the shuttle K into the shoot to be reduced and ultimately to form protein. At the same time, malate is produced in the shoot and part of the K-malate moves down to the root system where malate is oxidized, yielding KHCO3, which exchanges for KNO3. And the cycle continues (BEN-ASHER & PACARDO, 1997). Lack of potassium however, restricts the NO3 transport, which leads to nitrate reduction in the roots and accumulation of amino acids (figure 8). Accumulation of low molecular N compounds in roots at inadequate K and excessive N may signal via a feedback effect to the root to restrict further N uptake, which in turn lowers the N fertilizer use efficiency (MARSCHNER et al., 1996). This also means that the plant cannot be forced to take up more N if K is in short supply.

Correspondingly, after interrupting the K supply, tobacco plants absorbed 26% less nitrate than plants receiving adequate potassium. From the nitrate taken up after 5 hrs in K deficient plants, only 15% was incorporated into protein and 45% still remained as nitrate. In contrast, plants well fed with potassium converted 40% into protein and kept only 30% as nitrate (KOCH & MENGEL, 1974).

A similar mechanism can be seen behind the fact that sugar beet roots have a high content of noxious N when fed with excessive N and inadequate K. Noxious N reduces the extractability of sugar from beet. Noxious N accumulates because synthesis of protein is restricted. In addition, the sugar content is low because more assimilates are required for N metabolism (KRAUSS & BERINGER, 1988).

A lower sugar content in beet receiving inadequate potash may also derive from reduced translocation of assimilates from the leaves into the storage organ due to restricted phloem loading. This was demonstrated by supplying potato plants with labelled C and subjecting them to varying K supply. In plants receiving reasonable amounts of K, 80% of foliar applied 14C was translocated within 2 hrs into the tubers, whereas K deficient plants retained more than 50% of the absorbed 14C in the shoot (HAEDER et al., 1973). In this context, it is noteworthy that translocation of assimilates into the tubers was higher when potassium was supplied as K2SO4 compared to KCl (HAEDER, 1976).


Figure 8: K nutrition and nutrient cycling in plants

  after MARSCHNER et al., 1996  

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Quality auditing, a market chance or a burden?

In an era of globalization, certification schemes for quality and environmentally sound production processes, and other regulative measures, agriculture has to respond and to make the production process transparent by using approved standards like balanced fertilization. As indicated earlier, the customer not only looks for affordable food in good quality, he also looks for 'safe' food. He wants to follow-up how the food is produced, whether environmentally friendly and resource saving production methods have been used. Quality auditing could add a particular image to the produce, the added value would increase the competitiveness. MOERSCHNER et al. see a good market chance for those farmers, who adopt management systems with respect to quality and environment. This refers to production based on demonstrable quality norms; by so doing, it secures old and opens new markets, the farmer can certify quality and origin of his produce, he proves compliance with legislative rules, no problem with product liability, etc. Of course, quality auditing requires continuous recording, book keeping, nutrient accounting etc. However, it offers an important market niche.

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There is no doubt that, based on current demographic development and continuous urbanization with its impact on dietary pattern, quality crop production is a must. This refers equally to produce which is consumed either fresh, cooked or processed.

Balanced fertilization supports this demand by regulating the metabolic processes in yield formation towards quality. Ultimately, it is not only the consumer who will benefit, it is also the farmer through higher income, and the nation with export opportunities. Balanced fertilization also assists in resource conservation and environment protection.

For agriculture, and this applies to quality production, JOHNSTON (1997) says that efficient fertilization requires that all possible nutrient inputs be considered and a management strategy developed that ensures both economic viability and the maintenance and improvement of soil fertility.

But, this would also:

  • require support from policy makers through to farmers,
  • require the setting of appropriate limits for soil fertility,
  • require a massive educational program for farmers, and,
  • require the fertilizer industry to be able to continue to supply the nutrients the farmer needs.

Naturally, when procurement prices of crops are based on quality, farmers will take care. A survey made by IPI in India, after the price hike of phosphate and potash in 1992, showed that farmers in Northern India growing mostly staple food crops continued to buy urea and phosphate as before. However, with the higher phosphate price, nothing was left in the budget to buy potash and the nutrient ratio deteriorated considerably. Absence of quality based procurement and almost no visible response of cereals tempted the farmer to sacrifice potash at higher fertilizer prices. In Southern India however, cash crops like tea, coffee, pepper or cardamom are paid according to the quality. Farmers know that quality depends on balanced nutrition with potash. Forced to economize on fertilizer purchase, in order to preserve crop quality, they lowered the overall fertilizer level but tried to keep the balance.

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