GROWTH CONDITIONS AND SUGAR BEET YIELDING

ON VARIOUS CULTIVATION SYSTEMS

Summary

The crop rotation-fertilizer experiment was founded in 2007 at the Agricultural Experiment Station Swojec (51º11'45" N, 17º14'10" E) belonging to the Wroclaw University of Life Sciences, in black soil rightly classified as complex IIIa soil. The doctoral thesis was carried out on the basis of strict, two-factor field experiment, and a randomized block design with three replications was established in the years 2013–2015. The subject of the study was four systems of sugar beet tillage: A – conventional tillage (ploughing 20 cm), B – reduced tillage (ploughing 15 cm + white mustard stubble), C – conservation tillage (mulch sowing of white mustard stubble shallowly mixed with soil), D – minimum tillage (mulch sowing of straw shallowly mixed with soil). The second research factor was nitrogen fertilization: 80 kg · ha^-1 (lowered), 120 kg · ha^-1 (optimal), 160 kg · ha^-1 (increased). The preceding crop in each year of the study was spring barley, while the preceding crop was spring wheat. Under the grain they also used similar tillage systems. The entire side preceding crop was placed into the soil. The aim of the study was to check the response of the sugar beet tillage on shallowing and to eliminate some cultivation treatment while applying fertilizer of straw and catch crop and the application of varied nitrogen fertilization.

The highest yields of sugar beet roots (65.8 t · ha^-1) was obtained after the application of traditional crops. Abandonment of deep ploughing in favour of conservation tillage has contributed to a negligible drop in yields. The lowest yields of roots were obtained in the plots of the minimal crop in which the forecrop plants used direct seeding. The use of simplification in tillage led to a significant reduction of sugar beet density. The highest final density was found in conventional tillage (102.9 thous. pcs · ha^-1) and the lowest, nearly 1/3 lower minimum tillage. The highest sugar content was characterized by sugar beet roots from minimum tillage (18.2%) and conservation tillage (17.1%). The lowest sugar content was found in conventionally grown beets (14.5%). The increase in nitrogen doses (80, 120 and 160 kg · ha^-1) resulted in a reduction of sugar content in the roots. Technological sugar yield was significantly conditioned by cultivation systems. Most sugar was obtained from beet grown in the conservation system (9.4 t · ha^-1) and minimum tillage (9.1 t · ha^-1). The use of crops without ploughing has generally led to achieve significantly enhanced performance of the soil structure. Earthworm abundance and biomass was significant higher in conservation and minimum tillage compared with reduced tillage. Soil respiration on the spring was not determinated by cultivation systems, nitrogen fertilization and interaction of experimental factors, but the greatest respiration was in conservation tillage. At autumn the smallest respiration found at reduced tillage. Despite the significantly more concise soil in no-plough tillage of sugar beet, longer, thicker and heavier roots were produced under the influence of conservation and minimum tillage. Thanks to these morphological parameters, density losses were largely nullified. The use of mulch seeding led to increased weed infestation of sugar beet. The largest infestation was found in the plots cultivated in a minimum way (92.3 pcs. · m^-1), and the smallest – from conventional tillage (62.2 pcs · m^-1). Long-term use of the no-plough tillage with mulch sowing led to a mass of horsetail.

The most optimal system of cultivation proposed to implement the practice of farming, conservation tillage is combined with the application of 80 kg N · ha^-1.