The effect of different N, P and K supplies on the yield, composition and sugar yield of the sugarbeet variety Beta Monopoli N-1 was studied in the 8th year of a long-term experiment in 1981 on calcareous loamy chernozem soil. The readily available nutrient contents of the soil were also investigated using various methods. The ploughed layer had a pH(KCl) of 7.3 and contained 5 % CaCO3, 3 % humus and 20 % clay, while soil analyses indicated satisfactory supplies of Mg, Mn and Cu, moderate supplies of N and K and poor supplies of P and Zn. The main experimental conclusions can be summarised as follows: 1. Nitrogen. The maximum beet yield (55.7 t/ha) and refined sugar yield (10.1 t/ha) were given by the 100 kg/ha/year N treatment. The maximum digestion (19.4%) was obtained on plots which had received no N for 8 years. As the result of increasing N abundance the beet/foliage ratio dropped from 4.5 to 2.2 and the plant density at harvest from 82,000 to 66,000, while the mean beet mass rose from 568 g to 835 g. In this same treatment the digestion and refined sugar yield were reduced by 2.0-2.5%, while the molasses yield rose from 2.8% to 3.6% and the harmful N from 4.6 to 8.8 mgeq/100 g. The K and Na concentrations were also significantly higher, by 0.6 mgeq/100 g. 2. Phosphorus. Sugarbeet does not have a high P requirement and no real P effects were observed on this low-P soil. The optimum AL-P2O5 range on calcareous loamy soils of this type is around 150-200 mg/kg. The damaging effects of excessive N could not be counterbalanced by increasing P rates. 3. Potassium. The optimum AL-K2O range was around 200 mg/kg and increasing K rates were partly able to counteract the negative consequences of excessive N: they moderated the reduction in plant density, increased digestion by 0.5-0.7 % and resulted in a 1.4 t/ha increase in the crude sugar yield and a 0.9 t/ha increase in the refined sugar yield. There was no change in the refined sugar %, however, since the excessive rate of K also increased the K content of the beet from 4.3 to 6.9 mgeq/100 g, while the molasses content rose from 2.8 to 3.8%. 4. The NO3-N reserves in the 0-60 cm soil layer at sowing could serve as a basis for determining the N requirements. These N reserves have a value equal to that of mineral fertilisers and give a good reflection of the N-supplying ability of the soil. The optimum values of the 20°C fraction obtained using the EUF method indicate the following limit concentrations for the ploughed layers of similar soils: NO3+NO2-N 3-4, P 1.0-1.5, K 8-10 mg/kg. These data could serve as guidelines for the extension service.
|Number of pages||13|
|Publication status||Published - Dec 1 2000|
ASJC Scopus subject areas
- Agronomy and Crop Science