The effect of different levels of N, P and K fertilisation on the readily available nutrient content of the soil and on the yield, oil %, fatty acid composition, yield components and disease resistance of the sunflower hybrid Koflor-2 was studied in 1982 in the 9th year of a long-term fertilisation experiment set up on a total of 128 plots with 43 = 64 treatments on calcareous loamy chernozem soil. The annual N rates were 0, 100, 200 and 300 kg/ha, while the P2O5 and K2O rates amounted to 0, 1000,2000 and 3000 kg/ha over the 9 years. The ploughed layer of the experimental site contained around 5% CaCO3, 3% humus and 20% clay, and had a pH(KCl) of 7.3. The soil analysis showed the original soil to be satisfactorily supplied with Mg, Mn and Cu, moderately supplied with N and K, and poorly supplied with P and Zn. The groundwatcr was at a depth of 13-15 m and the growing site was liable to drought. Rainfall during the vegetation period amounted to 295 mm, prior to which the soil contained water reserves of approx. 200 mm. The main results can be summarised as follows: 1. The air dry mass of the 6-8-lcaf sunflower shoots rose 2.5 times as the result of combined PK fertilisation, while N fertilisation caused mild depression. By harvest time the PK effects had disappeared and a moderate (0.3 t/ha) N effect was observed in the achcnc yield, which could be attributed to an increase in the diameter of the inflorescence. As the NxP supplies improved, however, the oil content of the seed declined from 50 to 45 %, so there was no change in the oil yield as the result of the treatments. 2. Sunflower yielded 3.1 t seed, 3.1 t stalk and 1.7 t head (a total of 7.9 t air-dry mass) per hectare. The oil yield was 1.5 t/ha. On similar soils rates of 100 kg/ha N, 120-150 mg/kg AL-P2O5 and 150-200 mg/kg AL-K20, estimated with the ammonium lactatc method, will ensure a good yield. 3. Excessive nutrient supplies, or over-fertilisation, led not to a greater yield, but to greater susceptibility to diseases and to a decrease in quality. The occurrence olMacrophominaphaseoIina in the mature crop was four times as high as in the control, especially in plots given combined NxP supplies. Infection with Alternaria zinniae rose significantly by 8% due to excessive K, while infection with Embellisia helianlhi was doubled by excessive N. The frequency ol Sclerotinia sclerotiorum was insignificant in this dry year, though it also tended to increase with fertilisation (from 0.3 to 3 %). The number of seeds shed from the head was also several times greater in the fertilised plots. 4. The extreme values of 1000-sccd mass and oil content ranged from 20-80 g and 40-57%, respectively, for individually examined plants. The seed yield and 1000-achcnc mass rose with an increase in the inflorescence diameter, while the oil % of the seed declined. There was a great reduction in the 1000sccd mass and an increase in the oil % towards the middle of the inflorescence. 5. From the agronomic point of view an head diameter of 18-20 cm, a plant density of 45-55 thousand plants/ha, achieved with a spacing of 7025 or 7030 cm, and most importantly a uniform stand arc desirable. A thin stand resulting in extremely large flowers or a dense stand leading to very small flowers will reduce the oil yield. 6. On relatively heavy soils with a satisfactory supply of nutrients sunflower is not a crop with a high fertiliser requirement. A seed yield of 3 t/ha can be achieved with approx. half as much N and P fertiliser as a 6 t/ha yield of cereals. The interests of the grower and the oil industry will not clash if the negative correlation between yield and oil % is only moderately manifested.
|Number of pages||11|
|Publication status||Published - Dec 1 2001|
ASJC Scopus subject areas
- Agronomy and Crop Science