Nutritional aspects of farming

Plants are the only species that are able to convert CO2 from the air and water into carbohydrates. The carbohydrates are the source of energy for most other species that obtain their energy from carbohydrates.

Plants do not only produce carbohydrates but also essential organic compounds like vitamins, essential amino acids and fatty acids. Therefore plants, and more specifically the food crops cultivated by man, are the primary source of carbohydrates and essential organic compounds for the entire food chain. Furthermore, they provide almost all essential nutrients for humans and animals.

Table 1 shows the known essential nutrients for crops, humans and animals. The minerals in table 1 that are printed in bold are the plant nutrients. In addition to the plant nutrients that are required by the plant itself, crops also absorb other minerals from the soil and incorporate them into their biomass, which provide the essential minerals for the species further down the food chain. This is the natural way in which minerals are introduced into the food chain and an explanation why minerals in organic matter like food is absorbed more easily by the body - has a better bio-availability - than the minerals ingested via mineral supplements.

Table 1: Known nutrients essential to sustain life

The issue of food quality and the nutritional contribution it can make, starts on the farm where the crops are grown, because the agricultural soil is the fundamental source of minerals for crops. Adequate amounts of essential nutrients are required to achieve desired yields and produce quality. If the soils do not contain the required minerals, a drop in crop yield and quality will be the consequence.

The nutrient supply to the crop can be influenced and specifically managed by the application of appropriate fertilizers. Without the use of mineral fertilizer, crop yield and quality depend on the natural soil fertility, the cropping history and the growing conditions. Balanced nutrition can enhance yield level, the mineral composition and crop quality. This applies equally to all essential plant nutrients and also for minerals that are not essential for crops but vital for humans and animals.

An example of lack of a mineral not essential for plants is selenium (Se). Many soils contain little or even no Selenium. Since Selenium is not a plant nutrient, plant growth will not suffer from Selenium deficiency. But plants grown on such soils will not contain enough Selenium for a healthy Selenium supply further down the food chain. Figure 1 gives an example of a Selenium effect on grassland. Application of an NPK from Yara that contained 0.001% (10 gram per ton) Selenium increased the Selenium content in the grass which in turn increased the Selenium in the blood of the cattle to the right level. The result: improved cattle health and a benefit for the farmer.

Figure 1: A NPK with Se increased the Se in the grass and in the blood of the cattle

Adequate levels and correct balance of all essential nutrients are required to ensure optimum yield and quality of the crop. Higher levels may be required  for certain nutrients to improve quality characteristics. In some countries the daily Calcium (Ca) intake of the population does not meet the standards recommended by WHO. Increased supply of Calcium to the crops grown in these countries may contribute to solve the problem. Figure 2 gives an example of a Ca enrichment of Pak Choi (a Chinese cabbage). It confirms that an increasing supply of Calcium Nitrate from Yara (Tropicote) increased the Calcium levels in the cabbage. This in turn will lead to a better Calcium content in the diet of the people.

Figure 2: Significant increase of calcium content in leaf tissue of Pak Choi by calcium application

In the future it is expected that health considerations will included in the quality requirements of crops. From a plant nutrition point of view it is possible to apply specific fertilizers that help crops to better respond to specific nutritional quality requirements. Such requirements will shift growers’ focus from quantity and crop yield towards crop quality. For this to happen, clear targets must be set by specialists on human nutrition and the targets be adopted throughout the entire food chain. Know how on plant nutrition can support such targets, making it possible to grow the healthy crops required to prepare and serve healthy food.