ANALYSIS OF INFLUENCE OF SOME AGROECOLOGICAL FACTORS ON THE PROCESS OF SUGAR-BEET PRODUCTION

The sort of sugar beet Domona was used in the polyfactorial trial in Caslav over the years 1988 to 1991 in this crop rotation: legume mixture (forage pea + broad bean) -winter wheat - sugar beet - spring barley. The trial was carried out in the sugar beet - barley growing region on heavy-medium textured, degraded Chernozem. The humus content was 2.5 %. Agrochemical properties of the soil (depth up to 0.2 m) before beginning: pH (KCl) 6.6; P (Egner) 59.1 mg.kg-1; K (Schachtschabel) 153 mg.kg-1. Three factors were studied in the trial them: 1. fertilizing of the nitrogen (three levels); 2. application of growth regulator Relan - anthranil acid and acetaminophenol (three variants); 3. weed control (two variants). During four years were obtained the results (Tab. I) which confirmed the need for the differential nutrition to reach the high values of quality. On the other hand, it is not necessary for the highest yield of sugar beet roots. For the highest sugar content yield, exploitability and high yield of polarized sugar manuring and PK fertilizing were sufficient. Without nitrogen fertilizing it is possible owing to the higher sugar content yield to reach the same or higher sale price thouhg when the yield of sugar beet roots was lower. Saving nitrogen fertilizers is very important for economic and ecological reasons. Very close negative correlation was found between the sugar content yield and amount of drawn nitrogen (r = 0.92xx) which was differing in each particular year. The sugar content yield was decreasing when nitrogen uptake increased, but higher uptake of nitrogen did not result in higher production of dry matter. Nitrogen fertilizing connected with its level had negative influence on the content of alphaaminonitrogen, potassium and sodium in roots and exploitability was worse. The influence of application of the growth regulator Relan on the root yield in a single dose or double dose in two various dates was unessential. The quality of roots did not change also significantly after application of the growth regulator. The positive influence of preemergent and subsequent postemergent application of herbicides on the sugar content yield, exploitability and yield of polarized sugar was found higher than the influence on the root yield. Only preemergent application resulted in no significant effects.