Weed infestation structure of fodder beet fields under various tillage systems

Abstract

Nowadays in domestic arable farming sown crop (weed) vegetation is among the leaders as to the harmfulness for agricultural crop yields. Weeds are an annually acting factor which reduces the yields of economically-valuable output in all the regions of Ukraine. It is to be mentioned that in arable farming of the country the yield losses of agricultural crops, caused by weeds, are growing constantly. A serious decrease of public target financing to protect cultivated crops from pests, diseases and weeds resulted in the violation of farm practices in agricultural crop cultivation all over the country. Namely, in all agro-climatic regions of Ukraine well-balanced scientifically-grounded crop rotations were reduced to 3–4 field rotations with 60–70 % share of grain crops. And, without a proper expertise of the farm machinery available at the farms, minimal or zero tillage is used. For example, reduced crop rotation with a dominating share of grain crops led to the increased load, caused by annul application of the same herbicides, and this, in turn, resulted in the appearance of resistant weed kinds in agro-phytocoenoses; the term violation of the weed control measures (first of all, chemical thinning) caused the decrease of their efficiency, particularly in controlling root-sprout weeds. Secondly, climate warming resulted in the increase of weed infestation of the agricultural crop fields due to the fact that most of the weeds survived during winter time and those typical for southern regions moved to the north (barnyard grass, amaranth, nightshade black, milkweed sharp, mallow runty and others). At the same the migration of northern kinds to the south was not recorded. One of the leading measures to regulate a weed component in agro-phytocoenoses is mechanical tillage. The updated tillage system has to be based on the principles of minimization which envisage the reduction of a mechanical effect on the soil aimed at the increasing of its erosion resistance and the optimization of soil fertility indicators. One of the ways to minimize mechanical tillage is to substitute moldboard tillage for mould boardless one, and also to decrease its depth and the number of cultivations. Purpose of the research is to estimate weed infestation of the fodder beet fields when various tillage systems are used. The experiments in five-field crop rotation were carried out in accordance with the theme of the research in a stationary field trial of SPC of Bila Tserkva NAU in 2009-2011. Four systems of tillage were studied. Three-fold replication and compact placing of replications are used; plots of the first order (tillage) are placed in one layer, gradually, systematically. Farm practices of fodder beet cultivation, used in the experiment, are typical to the ones applied in the research institutions and at the advanced farms of the zone. Machines, equipment and mechanisms, which are available at SPC BTsNAU and advanced farm enterprises are equipped with, are used when growing fodder beets. The methodology and organization of the technique of performing the trial facilitated this. Lowing at 30-32 cm depth was done with plow PLN –3–35, mouldboardless tillage – at 30–32 cm depth with subsurface cultivator KPG –250, shelling – at 10–12 cm depth with stubble plow PL – 5–25 and disc harrow BDV –3.0. The largest amount of weed raw mass was recorded under regular tillage with a subsurface cultivator. When differentiated and continuous shallow tillage was done, this indicator was the highest, as compared with the control, in the first year of the trial, and a reverse regularity was recorded in the last year of the trial. The raw mass of one sown crop was the highest under regular mouldboardless tillage, and under differentiated and continuous shallow tillage it was at the level of the control. Under continuous mouldboard, regular mouldboardless, differentiated and continuous shallow tillage this indicator was 3.67; 4.06; 3.71 and 3.73 g in 2009 and 3.37; 3.82; 3.34 and 3.34 g in 2011. A determinative factor, which weed infestation of agricultural crop fields depends on in the period of their vegetation, is light condition of the soil surface in the field. The latter is determined by the peculiarities of plant morphology, their development and sowing practice. In the structure of weed infestation the highest percentage – 20.7 % belongs to amaranth, 15.7 %– to Setaria pumila, 14.2 % – to barnyard grassand 11.1 %– to quinoa white. Under the effect of crop rotation weed grouping is changed (succession) in the period of germination of fodder beets which is connected with both the effect of a forecrop and a fertilization system of crop rotations and variants of tillage. Key words: fodder beet (mangold), tillage system, structure of weed infestation, raw mass of weeds, succession.