Mineral fertilisation of sugarbeet (Beta vulgaris L.) on calcareous loamy chernozem soil

The effect of different N. P and K supplies on the yield, composition and s ugar yield of the sugarbeet variety Beta Monopoli N-1 was studied in the 8( th) year of a long-term experiment in 1981 on calcareous loamy chernozem ro il. The readily available nutrient contents of the soil were also investiga ted using various methods. The ploughed layer had a pH(KCI) of 7.3 and cont ained 5% CaCO3, 3% humus and 20% clay, while soil analyses indicated satisf actory supplies of Mg, Mn and Cu, moderate supplies of N and K and poor sup plies of P and Zn. The main experimental conclusions can be summarised as f ollows: 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 digestio n (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 t o 2.2 and the plant density at harvest from 82,000 to 66,000, while the mea n 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 E: 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 e ffects were observed on this low-P soil. The optimum AL-P2O5 range on calca reous loamy soils of this type is around 150-200 mg/kg. The damaging effect s 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 excessi ve 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 conten t 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 equ al to that of mineral fertilisers and give a good reflection of the N-suppl ying ability of the soil. The optimum values of the 20 degreesC fraction ob tained 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.