The effect of mineral nutrition on fat accumulation in crops

The content and quality of vegetable oil in seeds are key indicators of the productivity of oil crops. By managing plant mineral nutrition, an agronomist directly influences the intensity of fatty acid synthesis in seeds. This allows not only for an increase in the total oil harvest but also for the improvement of its commercial properties.

Storage fats are deposited in seed kernels in the form of organized intracellular structures called spherosomes. In addition to fats, these structures contain phosphoglycerides, phytin, and hydrolytic enzymes necessary for seed germination. Fat synthesis occurs at the expense of carbohydrates derived from vegetative organs.

The formation of fat structural components takes place in stages:

• Glycerol, as well as saturated and monounsaturated (with one double bond) fatty acids, are synthesized in the cytoplasm.
• Acylglycerols and polyunsaturated fatty acids with two or three double bonds are formed in the endoplasmic reticulum.

Phosphorus and potassium fertilizers have the primary impact on the volume and properties of oil. Their application at optimal rates during the reproductive period meets the plants' requirements for phosphorus and potassium and increases the oil content of the seeds. At the same time, the proportion of polyunsaturated fatty acids in the oil increases, which enhances its nutritional and technical value.

Nitrogen affects fat accumulation differently. It is necessary to apply nitrogen fertilizers strictly during the growing season of plant growth and development. A nitrogen deficiency during this period weakens plant growth and reduces the assimilating surface area of leaves, which ultimately lowers both the total seed yield and their fat content.

Fat accumulation in root crops and risks of over-fertilization

In sugar beet, forage beet, and garden beet, as well as in carrots, very little fat is accumulated, and it is concentrated mainly in the peripheral parts of the root crops. This fat is characterized by a high amount of saturated fatty acids and low iodine values. Root crops require a large amount of nutrients; therefore, on poor soil, fertilizers significantly influence not only the yield but also the accumulation of carbohydrates, vitamins, nitrogenous substances, and fats.

• Increase in seed oil content from P and K — 2–3 %
• Fat content in beet — about 0.1 % of raw mass
• Fat content in carrots — 0.2–0.3 % of raw mass