Optimization of Spring Rapeseed Nutrition

An on-farm field experiment studying spring rapeseed nutrition with sulfur was conducted in 2016 in the Tyulyachi District of the Republic of Tatarstan. The grey forest soil (Humic Luvisol) at the experimental location had a heavy texture, low organic matter (OM) content (2.0%), slightly acid pH, low mineral nitrogen (N) (9 ppm), very high Olsen-extractable phosphorus (P) (43 ppm), high exchangeable potassium (K) (153 ppm), and a very low concentration of available sulfur (S) (2.7 ppm, extraction with 1 M KCl) in the 0 to 20 cm soil layer. The following seven fertilizer treatments were applied in 2016 (N, P₂O₅ and K₂O are indicated as kg/ha): 1) N29Р46K30; 2) N90Р46K30; 3) N90Р46K30S14; 4) N120Р46K30; 5) N120Р46K30S21; 6) N150Р46K30; and 7) N150Р46K30S28. A complex NPК fertilizer was applied at planting 2.5 cm to the side of the seed, providing 24 kg/ha of each N, P₂O₅, and K₂O. The other fertilizers including ammonium Nitrate, ammonium sulfate nitrate (30% N and 7%S), monoammonium phosphate, and potassium chloride were applied in spring before planting.

The 2016 season was characterized by optimal weather conditions in the spring through June, however July and August were somewhat hot and dry. The following seed yield of spring rapeseed was obtained in the indicated seven treatments (t/ha, 14% grain moisture content): 1) 0.95; 2) 1.78; 3) 1.81; 4) 2.07; 5) 2.15; 6) 2.58; and 7) 2.69. Thus, there was a strong linear response to N application up to the highest application rate of 150 kg/ha. Sulfur rates tended to increase seed yield by 2 to 4%. There was also a trend towards higher protein content in seeds in experimental treatments received S-containing fertilizer.