Nutrienții care sunt esențiali pentru menținerea verde a culturii sunt azotul și magneziul.
Magnesium plays a crucial role at the heart of the chlorophyll molecule despite being considered a secondary nutrient. Any magnesium deficiency quickly entails a drop in the chlorophyll content explained by reduced protein synthesis. 20 to 30% of the plant’s magnesium is connected to the chlorophyll; the remainder is in soluble form associated with various organic or mineral ions.
High deficiencies are still fairly rare however and can result either from a magnesium depleted soil, or be induced from the compaction of the soil or through an imbalance with other cations in the soil such as potassium, calcium or ammonium.
Comparativ cu absorbția totală, rapița returnează în sol 90% din potasiu și calciu, 83% magneziu, 66% sulf, 55% azot și 46% fosfor.
Manganese and iron are the two micro nutrients with the largest requirement by oilseed rape, however, boron and molybdenum deficiencies are those most frequently encountered.
A boron deficiency greatly reduces the viability of the pollen and seed formation, thereby reducing flowering and fertilization. Protein content is also affected. A slight deficiency may show no symptoms but nonetheless leads to poor seed formation. Distinguished by a very low requirement in the order of 20g/ha with contents of 0.4 to 0.6 ppm in the plant, oilseed rape is nonetheless susceptible to molybdenum deficiencies as with all crucifers. Any molybdenum deficiency reduces protein synthesis, leads to an accumulation of nitrate and reduces the effectiveness of the nitrogen.
There is an antagonism between sulphur and molybdenum: high sulphur uptake may reduce the uptake of molybdenum. Molybdenum is the only micro nutrient whose plant availability is increased by raising the pH of the soil.
Sulful a făcut obiectul unei cercetări intense, având în vedere cererea mare de rapiță pentru acest element și riscul unei pierderi semnificative de producție în cazul în care este deficitar; Precum și rolul său în calitatea semințelor și a șrotului.